US20090188805A1

US20090188805A1 - Superconformal electrodeposition of nickel iron and cobalt magnetic alloys

Info

Publication number: US20090188805A1
Application number: US12/358,628
Authority: US
Inventors: Thomas P. Moffat; Chang Hwa Lee; Daniel Jossel; Soo-Kil Kim
Original assignee: National Institute of Standards and Technology (NIST); US Government
Current assignee: GOVERNMENT OF United States, COMMERCE NATIONAL INSTITUTE OF STANDARDS AND TEHCNOLOGY, Secretary of; National Institute of Standards and Technology (NIST); US Government
Priority date: 2008-01-25
Filing date: 2009-01-23
Publication date: 2009-07-30

Abstract

A process for electrodepositing at least one ferromagnetic material into a three dimensional pattern within a substrate is provided. The process comprises providing a substrate material, dielectric or conductor, having a three dimensional recessed pattern in at least one outer surface thereof, dielectric substrate materials also having an electrical conductive seed layer at least within the three dimensional pattern. An electrolytic bath is prepared comprising at least one ferromagnetic material and at least one accelerating, inhibiting, or depolarizing additive. The at least one ferromagnetic material comprises at least one metal cation selected from the group consisting of Ni²⁺, Co²⁺, Fe²⁺, Fe³⁺, and combinations thereof. The substrate is placed into the electrolytic bath and the electrolytic bath contacts the conducting three dimensional pattern in the substrate or the conducting seed layer within the pattern on a dielectric substrate. A counter electrode is placed into the electrolytic bath. An electric current is passed through the electrolytic bath between the electrical conductive substrate or seed layer on the three dimensional substrate and the counter electrode. At least a portion of the ferromagnetic material is deposited into at least a portion of the three dimensional pattern wherein the at least one deposited ferromagnetic material is substantially void-free.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/023593, entitled “Superconformal Electrodeposition Of Ni—Fe—Co Magnetic Alloys”, filed Jan. 25, 2008, which is hereby incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This work is funded by the National Institute of Standards and Technology under the U.S. Department of Commerce.

ATTORNEY DOCKET NUMBER: 083 08 001ASSIGNEE: NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY

CERTIFICATION OF EFS-WEB TRANSMISSION UNDER 37 C.F.R. 1.10


I hereby certify that this New
Application and the documents referred	Signature
to as enclosed herein are being deposited	Steve A. Witters, 53,923
with the United States Patent Office on	Name, Reg. #
date of signature via the EFS-Web
Service.	Date of Signature

1. Field
Aspects of the present invention generally relate to using electrodeposition to fill recessed surface features of a substrate with metals and alloys in a substantially void free manner. More specifically, by using certain electrolyte additives void-free electrodeposition of ferromagnetic materials onto a three dimensional patterned substrate may be achieved.
2. Background
As reflected in the literature, electrodeposition of ferromagnetic materials, such as Co, Ni, Fe, and related alloys has been used in the fabrication of recording heads and media for hard disk drives, magnetic sensors, inductors, three-dimensional (3-D) structures associated with ultralarge-scale integration (ULSI), micro-electromechanical systems (MEMS), 3-D packaging and actuators.
In the prior art, thin-film ferromagnetic microstructures have been produced by through-mask electroplating (also known as the LIGA). Through-mask deposition has been applied to a wide variety of materials ranging from metals to semiconductors, including applications in both passive and active devices. LIGA combines template production (e.g., lithography) with electrodeposition whereby metal deposition proceeds on the exposed sections of the underlying conductive seed layer. Two manifestations of this are metal plating in nanopores of a metal-backed anodized alumina membrane and selective plating on a metallized substrate patterned with an overlying insulating photoresist. This process yields microstructures that are the negative image of the template structure. The implementation of the process is effectively two-dimensional in nature. Developing complex multilayered three-dimensional (3-D) structures by through-mask deposition may be problematic, particularly with regard to electrical addressability as required for the electrodeposition process as well as subsequent electrical and/or thermal isolation of the final intricate structures.
The Damascene process, which is widely used for producing multilevel Cu interconnection in ultralarge-scale integration, has offered an alternative to the LIGA approach to building 3-D magnetic nanostructures. The Damascene process comprises metallizing a topographically 3-D patterned dielectric with a thin seed layer to ensure conductivity across the entire surface followed by metal electrodeposition across the entire surface. This may be effectuated by the addition of accelerating and inhibiting electrolyte additives in an electrolytic bath in combination with the consequences of area change that accompanies deposition in the 3-D pattern. A subsequent planarization step removes the overburden, leaving the desired metal structures embedded within the dielectric. The process can be repeated as needed to produce multilevel interconnected structures that may exceed ten layers. The Damascene metallization process may provide void-free bottom-up superconformal filling of the trenches and vias with Cu.
In the case of copper, silver, and gold, void-free superconformal feature filling has been demonstrated by the use of electrolyte additives that locally modify the rate of growth leading to bottom-up filling of recessed features, such as trenches and vias. However, such void free feature filling has not been realized for electrodeposition of ferromagnetic materials.
In the case of ferromagnetic materials, the effect of additives on the morphological evolution and physical properties of the deposits has been employed in the prior art to a limited extent. For example, the influence of dilute concentrations of species, such as saccharin, quinoline, thiourea, and coumarian on improving film properties such as internal stress, corrosion resistance, and leveling of the micro-roughness, has been reported. Among them, thiourea and coumarin are known levelers that reduce the difference in height between protruding and recessed surface features in large 3-D structures, over 10-100 μm wide. However, use of the Damascene process for the electroplating of ferromagnetic materials in a 3-D patterned dielectric substrate has been limited. Void-free filling of trenches and vias with ferromagnetic materials remains problematic, especially in a small scale. What is needed is a process for substantially void-free filling of recessed surface features such as trenches and vias in 3-D patterned substrates with ferromagnetic materials.

SUMMARY

Aspects of the present invention generally relate to using electrodeposition to fill recessed surface features of a substrate with metals and alloys in a substantially void free manner. More specifically, by using certain electrolyte additives, substantially void-free electrodeposition of ferromagnetic materials within a three dimensional patterned substrate may be achieved. The substrate may be electrically conductive such as a metal or a doped semiconductor. Alternatively the substrate may be a dielectric. With a dielectric substrate, the patterned surface may first be rendered conductive by deposition of a thin electrically conducting seed-layer at least within the three dimensional pattern.
According to one aspect of the present invention, a process of electrodepositing at least one ferromagnetic material into a three dimensional pattern within a substrate is provided. The substrate may be comprised of electrically conductive materials, dielectric materials, or a combination thereof. A substrate material is provided having an electrically conductive three dimensional recessed pattern in at least one outer surface thereof. When using a dielectric substrate, a thin electrical conductive material is first deposited within the three dimensional pattern and optionally the outer surface of the substrate having the three dimensional pattern, providing a seed layer on the substrate. Providing an electrically conductive outer surface and an electrically conductive three dimension pattern may provide a more efficient deposition process. An electrolytic bath comprising at least one ferromagnetic material and at least one inhibiting, accelerating or depolarizing additive is prepared. The at least one ferromagnetic material comprises at least one metal cation selected from the group consisting of Ni , Co^{2 +}, Fe²⁺, Fe³⁺, and combinations thereof, and the anion typically being sulfate, chloride, sulfamate or some combination thereof. The substrate with seed layer is placed into the electrolytic bath wherein the at least one outer surface and three dimensional pattern is contacted by the electrolytic bath. A counter electrode is placed into the electrolytic bath whereby an electrical current is passed through the electrolytic bath between the seed layer on the substrate and the counter electrode. At least a portion of the at least one ferromagnetic material is deposited into at least a portion of the three dimensional pattern wherein the deposition of the at least one ferromagnetic material is substantially void-free.
According to another aspect of the present invention, the at least one accelerating, inhibiting, or depolarizing additive comprises a nitrogen containing compound.
According to yet another aspect, the at least one accelerating, inhibiting, or depolarizing additive has at least one compound selected from the group consisting of cationic surfactants, anionic surfactants, nonionic surfactants, heterocyclic benzimidazole derivatives, and combinations thereof.
According to a further aspect of the present invention, the at least one accelerating, inhibiting, or depolarizing additive comprises at least one compound selected from the group consisting of polyethyleneimine (PEI), 2-mercapto-5-benzimidazolesulfonic acid (MBIS), and combinations thereof.
According to yet a further aspect of the present invention, the at least one accelerating, inhibiting, or depolarizing additive comprises PEI.
According to another aspect of the present invention, the at least one accelerating, inhibiting, or depolarizing additive comprises MBIS.
According to yet another aspect of the present invention, a process of electrodepositing at least one ferromagnetic metal into a three dimensional pattern within a substrate is provided. The process comprising: providing a substrate material comprising an electrical conductive three dimensional recessed pattern in at least one surface thereof; preparing an electrolytic bath comprising at least one ferromagnetic metal cation selected from the group consisting of N2+, Co2+, Fe2+, Fe3+, and combinations thereof; mixing at least one accelerating, inhibiting, or depolarizing additive into the electrolytic bath; placing the electrical conductive pattern of the substrate into the electrolytic bath; contacting the electrical conductive pattern of the substrate with the electrolytic bath; placing a counter electrode into the electrolytic bath; passing an electrical current through the electrolytic bath between the electrical conductive pattern of the substrate and the counter electrode; the electrical current being passed between the electrical conductive pattern of the substrate and the counter electrode is such that the potential between the substrate and a reference electrode is at a value negative of -0.8V SCE or at an applied current density in the range of 0.1 to 50 mA/cm2 of the area of the electrically conductive pattern of the substrate, or both; and depositing at least a portion of the at least one ferromagnetic material into at least a portion of the three dimensional pattern wherein the at least one deposited ferromagnetic material is substantially void-free.
According to a further aspect of the present invention, a process of electrodepositing at least one ferromagnetic material into a three dimensional pattern within a substrate is provided. The process comprising: providing a substrate material having an electrical conductive portion with a three dimensional recessed pattern; preparing an electrolytic bath comprising the at least one ferromagnetic material and at least one accelerating, inhibiting, or depolarizing additive; the at least one ferromagnetic material comprising at least one metal cation selected from the group consisting of N2+, Co2+, Fe2+, Fe3+, and combinations thereof; placing the electrical conductive portion of the substrate into the electrolytic bath; contacting the electrical conductive portion of the substrate with the electrolytic bath; placing a counter electrode into the electrolytic bath ; passing an electrical current through the electrolytic bath between the electrical conductive portion of the substrate and the counter electrode; and depositing at least a portion of the at least one ferromagnetic material into at least a portion of the three dimensional pattern wherein the at least one deposited ferromagnetic material is substantially void-free.
According to yet a further aspect of the present invention a process of electrodepositing at least one ferromagnetic material into a three dimensional pattern within a substrate is provided. The process comprising: providing a substrate material having an electrical conductive three dimensional recessed pattern in a surface thereof; preparing an electrolytic bath comprising the at least one ferromagnetic material and at least one accelerating, inhibiting, or depolarizing additive; the at least one ferromagnetic material comprising at least one metal cation selected from the group consisting of N2+, Co2+, Fe2+, Fe3+, and combinations thereof; the at least one accelerating, inhibiting, or depolarizing additive comprising an additive selected from the group consisting of polyethyleneimine, 2-mercapto-5-benzimidazolesulfonic acid, and combinations thereof; placing the electrical conductive three dimensional recessed pattern in the substrate into the electrolytic bath; contacting the electrical conductive three dimensional recessed pattern in the substrate with the electrolytic bath; placing a counter electrode into the electrolytic bath; passing an electrical current through the electrolytic bath between the electrical conductive three dimensional recessed pattern in the substrate and the counter electrode; and depositing at least a portion of the at least one ferromagnetic material into at least a portion of the three dimensional recessed pattern in the substrate wherein the at least one deposited ferromagnetic material is substantially void-free.
According to another aspect of the present invention, the process step of preferentially depositing the ferromagnetic material into the three dimensional pattern results in a superconformal deposition of the ferromagnetic material within the three dimensional pattern.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a)-1(f) are schematic representations of different plating structures at various stages of different electrodeposition processes;

FIG. 2 is a series of field-emission scanning electron microscopy (FESEM) images of 3-D structures showing the effect of electrodeposition of Ni with an electrolytic solution containing MBIS at different concentrations within different patterns;

FIG. 3 is a series of FESEM images of 3-D structures showing the effect of electrodeposition of Ni with an electrolytic solution containing MBIS at different time intervals within different patterns;

FIG. 4 is a series FESEM images of 3-D structures showing the effect of electrodeposition of Ni at different overpotentials with an electrolytic solution containing MBIS within different patterns;

FIG. 5 is a FIB-TEM image of 3-D structure showing the morphology of Ni from the electrodeposition of Ni with an electrolytic solution containing MBIS;

FIGS. 6( a)-6(f) are a series of FESEM images of 3-D structures showing the effect of electrodeposition of Ni—Fe with an electrolytic solution containing MBIS within different patterns;

FIG. 7 is a series of FESEM images of 3-D structures showing the effect of electrodeposition of Co with an electrolytic solution containing MBIS within different patterns;

FIG. 8 is a series of FESEM images of 3-D structures showing the effect of electrodeposition of Co with an electrolytic solution containing MBIS at different time intervals within different patterns;

FIG. 9 is a FIB-TEM image of 3-D structure showing the morphology of Co from the electrodeposition of Co with an electrolytic solution containing MBIS;

FIGS. 10( a)-10(f) are a series of FESEM images of 3-D structures showing the effect of electrodeposition of Co—Fe with an electrolytic solution containing MBIS within different patterns;

FIGS. 11( a)-11(d) are a series of FESEM images of 3-D structures showing the effect of electrodeposition of Ni with an electrolytic solution containing no additive within different patterns;

FIGS. 12( a)-12(c) are a series of FESEM images of 3-D structures showing the effect of electrodeposition of Ni with an electrolytic solution containing PEI within non-uniform patterns;

FIGS. 13( a)-13(f) are a series of FESEM images of 3-D structures showing the effect of electrodeposition of Ni with an electrolytic solution containing PEI within different and non-uniform patterns;

FIGS. 14( a)-14(d) are a series of FESEM images of 3-D structures showing the inhomogeneity of Ni growth with the electrodeposition of Ni with an electrolytic solution containing PEI within non-uniform patterns;

DETAILED DESCRIPTION

The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.
Various inventive features are described below that can each be used independently of one another or in combination with other features. However, any single inventive feature may not address any of the problems discussed above or may only address a subset of the problems discussed above. Further, one or more of the problems discussed above may not be fully addressed by any of the features described below.
In at least one embodiment provided herein, a process for bottom-up void-free filling of ferromagnetic materials within a 3-D pattern in a substrate is provided. In at least one embodiment provided herein, a process may provide void-free filling of submicrometer 3-D patterns with at least one ferromagnetic material. The products formed by the process may be suitable to form products that may be useful as active device elements in ultralarge-scale integration (ULSI) and micro-electromechanical systems (MEMS). For example, 3-D structures associated with ULSI, MEMS, 3-D packaging, actuators, ferromagnetic materials in magnetoresistive random access memory, biomedical systems, magnetic race track memories, contacts for semiconductors and related devices, new semiconductor materials, electronic and spintronic device architectures, active devices within other electronic circuitry, and other devices as known in the art that may have an application for the incorporation of ferromagnetic materials by processes disclosed herein. Other products that may be produced by the processes disclosed herein may include three-dimensional batteries which represent a new approach for miniaturized power sources that are purposely designed to maintain small footprint areas and yet provide sufficient power and energy density to operate autonomous devices. Such products are disclosed in “Rethinking Multifunction in Three Dimensions for Miniaturizing Electrical Energy Storage” by Bruce Dunn, Jeffrey W. Long, and Debra R. Rolison, published in The Electrochemical Society Interface, Fall 2008, incorporated herein in its entirety. It is anticipated that other and additional applications of the processes disclosed herein will become apparent to those skilled in the art and the present disclosure shall not be limited to these examples of products that may have applications for the presently disclosed processes.
In addition to products benefitting from the magnetic properties of materials deposited onto a substrate, aspects of the invention may provide products with materials having desired thermal expansion properties. For example, Fe—Ni INVAR alloys may be deposited onto a patterned substrate in a void free manner which may be beneficial for building micro-sensors, actuators, precision instruments such as clocks, seismic creep gauges, television shadow masks frames, valves in motors, antimagnetic watches, etc. Aspects of the present disclosure may provide methods of building such devices or other devices which may utilize the thermal expansion properties of materials deposited onto a substrate. Methods of aspects of the present disclosure may be incorporated into a Damascene process with minimal cost.
A process of at least one embodiment herein may provide three dimensional micromagnets for microelectromechanical devices as well as active magnetic material components for use in a variety of information storage devices. An embodiment may provide a means for deposition of ferromagnetic metals as a precursor to forming two-dimensional or three-dimensional silicide contacts in microelectronics. In at least one embodiment provided herein, a process may provide a variety of device geometries formed from partially filling trenches, i.e., horseshoe magnets, or vias, i.e., magnetic cylinders. Trenches and vias may be completely filled and may even provide embedded magnetically isolated structures in nonferrous environments.
At least one embodiment disclosed herein provides void-free filling of recessed surface features on non-planar conducting surfaces with iron group magnetic materials. Specifically, the addition of certain benzimidazole derivatives to a conventional additive-free nickel plating baths, e.g. Watts bath NiSO₄—NiCl₂or sulfamate (SO₃NH₂—) bath may result in a superconformal deposition growth mode which may provide a manufacturable solution to problems associated with bottom-up filling with the overall growth front propagating uniformly across the work piece.
In at least one embodiment disclosed provides a process for electrodepositing of ferromagnetic materials such as Ni, Co, Fe, and alloys containing combinations thereof into trenches and/or vias in a substrate, such as dielectric substrate containing Si or some other element or compound. The process comprises a modified damascene process wherein the substrate is first etched by processes known in the art to form trenches and/or vias in a surface thereof. This three dimensional structure may then prepared with an adhesive material such as the physical vapor deposition of a thin Ti adhesion layer. An electric conductive seed layer such as Cu is then placed on the surface of the three dimensional structure of trenches and/or vias by processes as known in the art. This prepared substrate is then placed into an electrolytic bath containing at least one ferromagnetic material and at least one heterocyclic benzimidazole derivative such as MBIS. A counter electrode is then placed into the Watts bath and an electrical current is passed between the prepared substrate and the counter electrode. The ferromagnetic material(s) are first preferentially deposited at the bottom corners of the trenches and/or vias and then the three dimensional structure in the substrate material is filled by bottom-up filling. The filled substrate may then be planarized to remove any overburden of the ferromagnetic material(s). The process provides substantially void-free feature filling of submicrometer trenches and/or vias in a dielectric substrate with ferromagnetic materials. The product produced by this process may be a multilevel interconnection having ferromagnetic material(s) in trenches and/or vias with little or no void space within the three dimensional structure.
In at least one embodiment, the substrate is electrically conductive. Providing an electrically conductive substrate may eliminate the steps of preparing the substrate with an adhesive material and placing an electric conductive seed layer on the surface of the three dimensional structure of trenches and/or vias.
Examples of at least one embodiment are discussed in two recently published articles. One of such articles is entitled, “Electrodeposition of Ni in Submicrometer Trenches” by S.-K. Kim, J. E. Bonevich, D. Josell, and T. P. Moffat, published in the Journal of The Electrochemical Society 154 (9) D443-D451 (2007), incorporated herein in its entirety. This article discusses the effect of cationic, anionic, and nonionic surfactants on the rate and morphological evolution of nickel electrodeposition. Attention is given to the prospect for void-free filling of submicrometer trenches. Cationic species such as polyethyleneimine (PEI) and cetyl-trimethyl-ammonium (CTA+) were shown to yield significant inhibition of nickel deposition. The other article entitled “Magnetic Materials for Three-Dimensional Damascene Metallization: Void-Free Electrodeposition of Ni and Ni₇₀Fe₃₀Using 2-Mercapto-5-benzimidazolesulfonic Acid” by Chang Hwa Lee, John E. Bonevich, Joseph E. Davies, and Thomas P. Moffat, published in the Journal of The Electrochemical Society, 155 (7) D499-D507 (2008), incorporated herein in its entirety. This article discusses superconformal filling of submicrometer trenches with electrodeposited ferromagnetic materials in an electrolyte containing 2-mercapto-5-benzimidazolesulfonic acid (MBIS). The process may offer the ability to build three-dimensional magnetically active structures that may be easily integrated with other state-of-the-art metallization schemes such as the Damascene process.
In at least one embodiment provided herein, a process for the electrodeposition of nickel, cobalt, iron, and alloys thereof in 3-D structures in a dielectric material is provided. A process of electrodepositing at least one ferromagnetic material into a three dimensional pattern within a dielectric or metallic substrate may comprise providing a dielectric or metallic substrate material having a three dimensional recessed pattern in at least one outer surface thereof. In the case of a dielectric substrate an electrical conductive material is deposited onto the outer surface having the 3-D pattern and within the three dimensional pattern providing a wetting conductive seed layer on the substrate.
An electrolytic bath is prepared comprising at least one ferromagnetic material and at least one accelerating, inhibiting, or depolarizing additive. The at least one ferromagnetic material has at least one of Ni²⁺, Co²⁺, Fe²⁺, Fe³⁺, and combinations thereof. The dielectric substrate having the seed layer is placed into the electrolytic bath where the electrolytic bath contacts the at least one outer surface and the three dimensional pattern having a seed layer in the case of a dielectric substrate. A counter electrode is placed into the electrolytic bath and an electrical current is passed through the electrolytic bath between the seed layer on the substrate and the counter electrode. At least a portion of the ferromagnetic material is deposited into at least a portion of the three dimensional pattern wherein the deposited ferromagnetic material is substantially void-free. The electrodeposition step may provide superconformal filling of the 3-D pattern.
The at least one accelerating, inhibiting, or depolarizing additive may comprise a nitrogen containing compound. Alternatively or additionally, the at least one accelerating, inhibiting, or depolarizing additive may have a compound selected from the group consisting of cationic surfactants, anionic surfactants, nonionic surfactants, heterocyclic benzimidazole derivatives, and combinations thereof. Advantageously, the at least one accelerating, inhibiting, or depolarizing additive may comprise a compound selected from the group consisting of polyethyleneimine, 2-mercapto-5-benzimidazolesulfonic acid, and combinations thereof. Alternatively or additionally, the at least one accelerating, inhibiting, or depolarizing additive comprises polyethyleneimine. Furthermore, the at least one accelerating, inhibiting, or depolarizing additive may comprise 2-mercapto-5-benzimidazolesulfonic acid. Advantageously, the process may provide superconformal filling of trenches, vias, and other patterns within the dielectric substrate. It is to be understood that other and different additives may be placed into the electrolytic bath to provide void-free filling of the electromagnetic material into the trenches and vias or 3-D structure in the dielectric substrate and be within the scope of the present invention.
Advantageously, the process disclosed herein may provide for preferential deposition of the ferromagnetic material into the 3-D pattern and more advantageously the process may provide for superconformal deposition of the ferromagnetic material within the three dimensional pattern.
At least one embodiment may provide a deposition process that may allow void-free filling of recessed features with nickel and related iron group alloys as well as cobalt and other alloys and may be easily integrated with existing Damascene processes and related tool sets. Superconformal void-free deposition of nickel, cobalt, iron, and alloys thereof within a 3-D pattern with the addition of heterocyclic compounds such as benzimidazole (BI), benzotriazole (BTA), 2-mercaptobenzimidazole (MBI), a 2-mercapto-5-benzimidazolesulfonic acid (MBIS), and combinations thereof may be achieved in a modified Damascene process.
A uniform growth profile of electromagnetic materials at the pattern length scale of a given wafer may be achieved in at least one process disclosed herein. The addition of heterocyclic benzimidazole derivatives to the electrolytic bath may induce void-free feature filling of submicrometer trenches with Ni, Co, Fe, and alloys thereof for example. Superconformal filling of submicrometer trenches with electrodeposited Ni may be accomplished with an electrolytic bath comprising MBIS additions to a conventional NiSO₄—NiCl₂—FeSO₄electrolytic plating bath. The process may have the ability to build 3-D magnetically active structures that may be easily integrated with the conventional Damascene process as well as other state-of-the-art metallization schemes. Although the disclosure is not restricted to a particular mechanism, MBIS may act to inhibit Ni(Fe) electrodeposition, for example, although under certain conditions rapid, autocatalytic breakdown may accompany the onset of Ni deposition. Optimal trench filling may be associated with the positive feedback process, moderated by electrolyte internal-resistance losses, and manifest as a hysteretic voltammetric response on planar electrodes for an MBIS concentration ˜100 μmol/L, for example. On freshly immersed substrates, trench filling may be characterized by an initial period of uniform growth followed by the development of a v-notch geometry which may be associated with transient depletion of MBIS within the recessed feature. The finest submicrometer features may be filled with only minimal deposition on the neighboring free surface. Continued growth of the MBIS derived v-notch geometry may result in void-free filling of the larger features by geometrical leveling. Similar deposition of electromagnetic materials, such as Fe, Ni-rich Ni—Fe alloys, Co and Co—Fe alloys, for example, may be accomplished by at least one embodiment. MBIS may not significantly perturb the low coercivity of electromagnetic metals and alloys, which may be an important attribute for prospective applications of processes disclosed herein.
At least embodiment of a process disclosed herein may provide a desired effect on the rate and morphological evolution of ferromagnetic metal electrodeposition with the addition of cationic, anionic, and nonionic surfactants to the electrolytic bath. Cationic species such as polyethyleneimine (PEI) and cetyl-trimethyl-ammonium (CTA+) may provide significant inhibition of the deposition of magnetic metal, such as nickel, thereby providing void-free filling of submicrometer trenches. For a range of concentrations, single cationic surfactant systems may exhibit hysteretic voltammetric curves that, when corrected for ohmic electrolyte losses, may reveal an S-shaped negative differential resistance. Void-free bottom-up superconformal feature filling may be accomplished when operating at potentials within the hysteretic regime whereby metal deposition begins preferentially in the most densely patterned regions of the wafer followed by propagation of the growth front laterally across the wafer surface. Alternatively, at low overpotentials and concentrations, sulfur-bearing additives such as thiourea (TU) may exert a depolarizing effect on nickel deposition and negligible hysteresis. With a combination of PEI and TU in an electrolytic bath, the suppression provided by PEI may be diminished and feature filling may lead to more uniform deposition on the wafer scale. Suitable combinations of PEI and TU may enable near void-free filling of ≧230 nm wide trenches with sloping (˜3.5 degree inclination from vertical) sidewalls. Initial conformal growth may be followed by geometric leveling once the deposits on the sloping sidewalls meet. Feature filling with varied morphological evolution may be provided with one or more embodiment disclosed herein.
In at least embodiment, superconformal feature filling of Ni in sub micrometer trenches with an electrolytic bath comprising cationic surfactants, such as PEI, cetyl-trimethylammonium chloride, and 4-picoline, may exert significant inhibition on Ni electrodeposition at specific ranges of concentration and overpotential. Cationic nitrogen bearing polymers that may capable of generating superconformal feature filling having lateral non-uniformities may be provided. In particular, the polyelectrolyte PEI may give rise to a superconformal growth mode whereby preferential deposition occurs at the bottom corners of the trenches with almost negligible deposition occurring on the neighboring free surface area, at least during the initial stages of trench filling. Furthermore, the deposition process may be highly heterogeneous at the pattern length scale whereby dense arrays of narrower trenches may be filled followed by lateral propagation of the growth front onto neighboring planar areas. An aspect of this embodiment may provide a means to selectively fill only the finest feature on a given level or layer while leaving the large features open and available for deposition by a different material such as Cu. In this aspect, Cu coils may be placed around a ferromagnetic inductor all on one level of metallization, e.g. in the context of Damascene processing. By appropriate patterning and design, a variety of fully consolidated 3-D shapes and geometries may be fabricated. The resulting structures may have potential use as micromagnets for microelectromechanical devices as well as active magnetic material components for use in a variety of information storage devices. The process may also be useful in the deposition of Ni and related metals as a precursor to forming silicide contacts in microelectronics. The means to selectively fill only the finest features on a given level or layer while leaving the large features open and available for deposition by a different material may provide for an array of metal structures within a single layer, e.g. in the context of Damascene processing.
FIGS. 1( a) through 1(f) show examples trench or via 2 filling within a dielectric substrate 1. The dielectric substrate 1 may be first metallized with an electric conductive material on the surfaces adjacent to metal 3, not shown. FIG. 1( a) shows subconformal filling of a metal 3 in trench or via 2 in a planar region 4 of the dielectric substrate. The subconformal filling has a greater deposition rate at pattern features such as at the top edges 5 of trench or via 2. The subconformal growth shown in FIG. 1( a) may lead to voids 6 as shown in FIG. 1( b). As the electrodeposition continues, the metal growth at top edges 5 continues until the metal 3 meets at point 8, forming void 6 therein as shown in FIG. 1( b). FIG. 1( c) shows an example of conformal growth wherein metal 3 grows at a consistent rate on the planar region 4 of the dielectric substrate, within trench or via 2, and at the top edges 5 of trench or via 2. Conformal growth as shown in FIG. 1( c) may form a seam 8 as shown in FIG. 1( d). Seam 8 may be formed with the continued growth of metal 3 inward from the sidewalls 7 of trench or via 2. FIG. 1( e) shows an example of superconformal super-filling wherein metal 3 forms a “V-notch” 9 centrally oriented within trench or via 2. This is also referred to as bottom-up filling and may produce a substantially uniform filling of trench or via 2 with metal 3 as shown in FIG. 1( f). In bottom up filling, metal deposition occurs preferentially in recessed surface features, such as patterned trenches and vias 2, thereby resulting in void-free filling, as shown in FIG. 1( f). On freshly immersed substrates, trench filling may be characterized by an initial period of uniform growth as shown in FIG. 1( e) followed by the development of “v-notch” 9 geometry which may be associated with transient depletion of an additive such as MBIS or PEI within the recessed feature, trench or via 2. The finest submicrometer features may be filled with only minimal deposition on the neighboring free surfaces 10, as shown in FIG. 1( e).

EXAMPLES

The following examples are included to demonstrate embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples that follow represent techniques discovered by the inventors to function in the practice of the invention, and thus can be considered to constitute selected modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments that are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.

Example 1

Void-free Ni deposition was shown onto a dielectric substrate. Nickel was eletrodeposited from an electrolytic bath comprising of 1.0 mol/L NiSO₄.6H₂O, 0.2 mol/L NiCl₂.6H₂O, and 0.5 mol/L H₃BO₃, with pH 2.5 as a base electrolyte. Separate electrolytic solutions were prepared by adding different concentrations of MBIS, from 0 to 400 μmol/L, to the base electrolyte. The sodium salt dihydrate of MBIS, C₇H₅N₂NaO₃S₂.2H₂O, manufactured by Aldrich, was used. Both planar and patterned Cu seeded Si wafers were used as working electrodes for electrochemical analyses and film growth. The specimens were prepared by physical vapor deposition of a thin Ti adhesion layer followed by 100 nm of Cu. The trenches including the barrier layer were 670 nm deep, and the widths varied from 590 to 90 nm at the bottom and from 720 to 120 nm at the top, corresponding to sloping sidewall angle that ranged from 6 to 2 degrees from vertical. On the basis of the average width, the features range from 6.4 to 1.0 in aspect ratio (height divided by average width). In this example, features are specified by the respective bottom width.
The working electrodes were sealed with a Teflon holder having an exposed area of 1.28 cm , facing up to the electrolyte in order to facilitate removal of any hydrogen gas associated with deposition. The Pt counter electrode was formed as a circular wire of similar radius to, and suspended above, the working electrode. A saturated calomel reference electrode (SCE) was firmly positioned with respect to the working and counter electrode in a Teflon jig, thereby fixing the electrical distribution and resulting internal-resistance iR effects between different solutions. For feature filling examples, the trench and via patterned wafer specimens were immersed at a preset growth potential. Field-emission scanning electron microscopy (FESEM) was used to examine cross sectional profiles of the trench filling. Transmission electron microscopy (TEM) was used to more closely examine the microstructure of an array of Ni-filled trenches. The specimen was prepared by focused ion-beam FIB sectioning. X-ray diffraction (XRD) and atomic force microscopy (AFM) were used to examine the crystallographic texture and the surface morphology of the Ni films grown on planar substrates. The magnetic properties of planar Ni and Ni—Fe films were examined by vibrating sample magnetometer (VSM) and the saturated magnetic moment, coercivity and squareness were evaluated as a function of MBIS concentration. Specimens were prepared by cleaving to obtain square-shaped samples. The specimen area and thickness were measured by an optical scanner and FESEM, respectively.
Ni deposition from the additive-free electrolytic bath was examined by cyclic voltammetry (CV). The onset of metal deposition was evident near 0.7 V, followed by a rapid increase in the current with the applied potential that tends toward a linear response at higher current densities.
A series of samples were feature filled as a function of MBIS concentration. Ni was deposited at −0.925 V SCE (i.e., voltage defined relative to saturated calumel reference electrode, SCE) for 3 min, and then the specimens were cross sectioned for FESEM analysis. Images of trench arrays with four different dimensions are shown in FIG. 2 wherein trench widths of 520 nm are shown in column (1), trench widths of 260 nm are shown in column (2), trench widths of 150 nm are shown in column (3), and trench widths of 90 nm are shown in column (4). The trench widths are reported as the dimension of the bottom of the trench and these different dimensions offer a representative sample of filling behavior. The concentrations of MBIS were 0 μmol/L, shown in row (a), 50 μmol/L, shown in row (b), 80 μmol/L, shown in row (c), 100 μmol/L, shown in row (d), and 150 μmol/L, shown in row (e). The dark contrast 103 at the bottom 118 of the trench 102 and on the free surface 104 between the trenches is associated with the copper seed layer. In the absence of MBIS, a large seam 106 is apparent in the narrowest trenches, shown in FIG. 2, column (4), while voids are sometimes evident at the top of all but the widest features, as in row (a) of FIG. 2. The upper surface 110 of the deposition on free surface 104 is also notably rough relative to the dimension of the trenches 102 and overburden 112. Thus, conformal deposition coupled with high surface roughness may lead to the formation of voids and/or seams 106 when the rough opposing side walls impinge.
Deposition in the presence of 50 μmol/L MBIS, shown in row (b) of FIG. 2, results in smoother overburden 110 above the widest trench, as shown in FIG. 2, row (b), column (1); however, centerline voids and/or seams 106 appear near the top of the smallest trenches shown in column (4). Increasing the MBIS concentration to 80 μmol/L, shown in row (c) of FIG. 2, yields a smoother free surface 110; however, voids and/or seams 106 are still evident at the top of finest trenches shown in row (c), column (4), although they are smaller than for the 50 μmol/L shown in row (b) of FIG. 2. A further increase in the MBIS concentration to 100 μmol/L, shown in row (d) of FIG. 2, leads to void-free filling for all features shown. Comparison between the additive-free, 50, 80, and 100 μmol/MBIS concentrations shown in rows (a), (b), (c), and (d) respectively, performed for the same duration and potential, show progressively less overburden 112 above the filled features 102, which may show the inhibition provided by MBIS. This effect is most notable over the widest features, shown in column (1) of FIG. 2. A further increase of MBIS concentration to 150 μmol/L, shown in row (e) of FIG. 2, was shown to lead to a sharp decrease in the overall deposition rate. In row (e) of FIG. 2, very limited deposition occurred on the free surface 104 while substantial filling of the trenches 102 occurred. The smaller trenches 102 shown in columns (2)-(4) of FIG. 2, row (e), are completely filled while the growth front in the widest features shown in column (1) of FIG. 2, row (e), has a well-defined v-notch shape 114. This shows a superconformal film growth mode in column (1), row (e), of FIG. 2; whereby the effect of a linear gradient of the sidewall 116 growth velocity with trench depth is evident and deposition at the bottom 118 of the trench 102 is substantially progressed compared to the neighboring free surface 104.
In order to show a more detailed view of shape evolution during feature filling, a series of samples were examined as a function of deposition time at −0.925 V SCE in the 100 μmol/L MBIS electrolytic solution. The results for five different trench widths as shown in FIG. 3 wherein row (a) has a trench width of 590 nm, row (b) has a trench width of 520 nm, row (c) has a trench width of 305 nm, row (d) has a trench width of 160 nm, and row (e) has a trench width of 130 nm. For reference purposes, the Cu-seeded substrate t=0 is shown prior to Ni deposition in the column (1) of FIG. 3 for each trench width. The columns, from left to right, show the deposition of Ni after 0 seconds in column (1), 25 seconds in column (2), 50 seconds in column (3), 100 seconds in column (4), 150 seconds in column (5), 200 seconds in column (6), and 300 seconds respectively in column (7). The buildup of Cu 202 on the top 204 and bottom 206 surfaces, relative to the sidewalls 208, reflects the nature and limitations of the physical vapor deposition or sputtering process used to form the seed layer 210. Examination of the filling images after 25 seconds of deposition show a substantially conformal Ni layer 212 along the entire surface profile, where the height 214 of the bottom surface 206 and the sidewall 208 thickness 216 are almost the same. The extent of Ni deposition in the recessed regions 218 may be compared to the integrated deposition charge derived from the chronoamperometry transient. Because the surface area changes significantly during feature filling, a comparison of nominal thickness value may be only considered for the first 25 seconds and the last 100 seconds from 200 to 300 seconds, assuming that there is minor area change occurring for the respective cases.
Between 25 seconds and 50 seconds, shown in column (2) and column (3) respectively, the two finest features, shown in rows (d) and (e), are shown to be filled while almost negligible Ni deposition has occurred on the top surface 204. The geometry of the feature filling is such that electrode area change effects may be most strongly during the filling of the smallest and highest aspect ratio features. In the three wider trenches shown in rows (a), (b), and (c), a gradient in the deposition rate on the sidewalls 208 has clearly developed as a function of width, similar to that noted earlier in row (e) of FIG. 2 The amount of Ni deposited on the bottom surface 206 is shown to be substantially the same to that on the sidewalls 208 immediately adjacent to the bottom 206. Notably, the amount of Ni deposited on the sidewalls 208 of the larger features may exceed half of the width of the two narrowest trenches, shown in rows (d) and (e), consistent with those features which may have already been filled by sidewall collision, followed by a geometric zipping process The transient depletion of MBIS within the trench may result in the sloping sidewalls or v-notch shape and may be critical to the overall void-free filling process.
Between 50 seconds and 100 seconds, as shown in columns (3) and (4) of FIG. 3, growth continues on the bottom 206 and sidewalls 208 of the 305 nm wide trench shown in row (c) of FIG. 3. The slope associated with sidewalls 208 did not change substantially between 50 seconds and 100 seconds, as shown in columns (3) and (4), row (c), of FIG. 3. This may show a transition back to a conformal growth mode as reflected by the constant sidewall growth velocity during this time increment. Evolution of the growth front in the widest trench, shown in row (a) of FIG. 3, may also support this. In the absence of any compositional gradients, continued growth on such a v-notched surface geometry may result in a planar surface by an effect known as geometrical leveling. Indeed, following trench filling, significant growth is shown to begin on the adjacent free surface 204 and the remaining cusp shape in the larger features is filled congruent with geometric leveling.
FIG. 3 shows that trench filling may be associated with three stages, a brief period of near conformal growth, followed by the development of sloping sidewalls, and the subsequent onset of impingement of opposing sidewalls. The remaining cusp or v-notch shape may then be filled by geometric leveling. A key role of MBIS may be the development of sloping sidewalls, which may be associated with transient depletion of the MBIS flux within the trench. Deposition in the presence of MBIS was shown to be substantially uniform on the pattern density length scale, making the MBIS process a viable manufacturing solution in the context of conventional Damascene processing
The potential dependence of trench filling is shown in FIG. 4 for a fixed MBIS concentration of 100 μmol/L and a fixed deposition time of 300 seconds. The results for four different trench widths as shown in FIG. 4 wherein column (1) has a trench width of 520 nm, column (2) has a trench width of 305 nm, column (3) has a trench width of 160 nm, and column (4) has a trench width of 90 nm. The rows, from top to bottom, show the deposition potential wherein row (a) has an potential of −0.850 V SCE, row (b) has an potential of -0.875 V SCE, row (c) has an potential of −0.900 V SCE, row (d) has an potential of −0.925 V SCE, and row (e) has an potential of −0.950 V SCE.
At −0.850 V SCE, shown in row (a) of FIG. 4, the deposition potential was so low that the transition to the activated surface 300 and the MBIS passivated one is substantially negligible. Deposition on the trench pattern was limited, but preceded conformally, and the roughness that developed on the sidewalls 308 of the finest feature in column (4) of FIG. 4 lead to incipient occlusion of voids 315 along the centerline of the finest features, as shown in row (a), column (4) of FIG. 4. Increasing the overpotential by 0.025 V to −0.875 V SCE placed the system within the positive feedback hysteretic voltammetric regime. Void-free filling of the finest features was shown along with the development of sloping sidewalls 308 in the wider trenches, as shown in row (b) of FIG. 4. When the overpotential is increased further by 0.025 V to −0.900 V SCE, sloping sidewalls 317 are readily evident in the widest trench shown in row (c), column (1) of FIG. 4 while the remaining trenches are filled and void-free, as shown in row (c), columns (2)-(4) of FIG. 4. For growth at −0.925 V SCE and −0.950 V SCE, all features are shown to be void-free and the overburden thickness 313 increased sharply as shown in rows (d) and (e) of FIG. 4.
FIG. 5 shows a FIB-TEM cross sectional image of a 160 nm width trench filled by Ni electrodeposition in the presence of 100 μmol/L MBIS where the deposition was performed at −0.925 V SCE for 150 seconds. FIG. 5 shows that the addition of MBIS enables void-free trench filling. FIG. 5 shows that the volume of materials associated with the free surface 404 between the trenches 401 is mostly Cu 403, which is only covered with a thin 25 nm thick Ni layer 405. In contrast, the 160 nm wide trench 401 is entirely filled with Ni 402 and free of any obvious voids. A microstructural seam 407 may exist along the top two-thirds of the trench. This seam 407 or consolidated boundary may be formed during deposition in a manner analogous to grain boundary generation associated with grain coalescence during Volmer-Weber film growth. The bright-field contrast shows an average grain size on the order of about 30-40 nm, although certain grains are shown to be larger with well-defined twins or stacking faults evident.

Example 2

Void-free Ni—Fe deposition was shown onto a dielectric substrate 500 is shown in FIGS. 6( a)-(e). The extension and efficacy of MBIS for inducing superconformal deposition of Ni—Fe alloys is shown. Permalloy, a Ni₈₀Fe₂₀alloy that has a rich history in the development of magnetic storage devices was electrodeposited onto a dielectric substrate 500 with the process of Example 1. The electrolytic bath comprised 1 mol/L NiSO₄.6H₂0+0.2 mol/L NiCl₂.6H₂O+0.05 mol/L FeSO₄+0.5 mol/L H₃BO₃. 100 μmol/L of MBIS was added to the solution and the Ni—Fe alloy was electroplated onto the 3-D seeded surfaces of the dielectric substrates with an electric potential of about −0.950 V (SCE) for about 300 seconds. Cross-sectional FESEM images of various patterned trenches showing the deposition of the Ni—Fe alloy 502 are shown in FIGS. 6( a)-(e). Void-free feature filling is clearly shown in each pattern in FIGS. 6( a)-(e). The presence of iron in the electrolytic solution showed a decrease in the deposition rate as compared to that of Example 1. The magnetic properties of the Ni—Fe alloy films were shown not to be significantly altered by MBIS additions in the plating bath.

Example 3

Void-free Co deposition was shown onto a patterned substrate. The effect of MBIS for inducing void-free deposition of cobalt is shown in FIGS. 7-9. Cobalt was electrodeposited onto a dielectric substrate with the process of Example 1. The electrolytic bath comprised 0.4 mol/L CoSO₄7H₂O+0.01 mol/L CoCl₂+0.5 mol/L H₃BO₃. Various amounts of MBIS were added to the solution and the Co was electroplated onto the 3-D surfaces of the substrates with various electric potentials for various periods of time.
FIG. 7 shows cross-sectional FESEM images of various patterned trenches showing the deposition of Co 602 in an additive-free deposition at -0.86 V for 300 seconds in rows (a) and (b) for various trench widths, ranging between 720 and 90 nm. Rows (c) and (d) show the deposition of cobalt 602 with an electrolytic solution comprising 200 μmol/L MBIS at −0.86 V for 300 seconds for various trench widths, ranging between 720 and 90 nm. The smaller trenches in the additive-free deposition have void spaces 615, as shown in row (a) column (3) and row (b) columns (1)-(3), of FIG. 7. This is contrasted with the void-free deposition of Co 602 shown in each trench in rows (c) and (d), having MBIS.
FIG. 8 shows the deposition of cobalt 602 with an electrolytic solution comprising 200 μmol/L MBIS at −0.87 V for 25 seconds in column (1), 50 seconds in column (2), 100 seconds in column (3), 180 seconds in column (4), and 300 seconds in column (5) for various trench widths in each row (a)-(e). The trench widths in FIG. 8 are as follows; row (a) had a trench width of 720 nm, row (b) had a trench width of 280 nm, row (c) had a trench width of 215 nm, row (d) had a trench width of 200 nm, and row (e) had a trench width of 140 nm. Void free deposition of Co 602 in a range of trench widths was shown. In each pattern shown in rows (a)-(e), superconformal filling of Co 602 was exhibited as shown.
FIG. 9 shows TEM for Co 602 filling using the process of Example 1. The electrolytic bath comprised 200 μmol/L MBIS and the Co 602 was deposited onto the dielectric substrate 601 at an overpotential of −0.86 V SCE. The TEM shows that the micro-structure is void-free with a low density grain boundary marking the 603 center line.

Example 4

Void-free Co—Fe deposition was shown onto a patterned substrates. FIGS. 10( a)-(f) show Co₈₀Fe₂₀ 702 trench filling using the process of Example 1 but in a base electrolyte of 0.4 mol/L CoSO₄ ⁻7H₂O+0.01 mol/L CoCl₂+0.5 mol/L H₃BO₃+0.01 mol/L FeSO₄. The electrolytic bath contained 200 μmol/L MBIS and the alloy was deposited onto the patterned dielectric substrates 703 at an overpotential of -0.87 V for 300 seconds. The patterns varied, having trench widths between 726 nm in FIG. 10( a) and 134 nm in FIG. 10( f). A superconformal void-free deposition of Co₈₀Fe₂₀ 702 was shown in each of the patterns of FIG. 10( f).
In each of the Examples 1-4, the addition of MBIS to the electrolytic solution yielded a smoother outer surface with little or no measurable effect on the saturated magnetization (Ms) of the ferromagnetic materials deposited onto the dielectric substrate.
Examples 1-4 show superconformal electrodeposition of Ni, Ni—Fe, Co, and Co—Fe alloys using a single benzimidazole derivative, MBIS, as an additive to the respective sulfate/chloride mixed electrolyte. The process may offer integration of the ferromagnetic materials into Damascene processes, microelectromechanical systems and related thin-film derived technologies. Feature filling at potentials within the voltammetrically identified critical regimes resulted in void-free superconformal film growth. For freshly immersed specimens, trench filling initially proceeded with a period of conformal growth followed by the development of sloping sidewalls which may be associated with transient depletion of MBIS within the recessed features. The resulting v-notch growth front then evolved in a manner that is difficult to distinguish from geometric leveling. Stabilization of the feature filling process within the voltammetrically identified critical domain is provided by a decrease in the overpotential for metal deposition that accompanies the flow of current in the resistive electrolyte.

Example 5

A survey of the effect of various electrolyte additives on the nickel deposition kinetics, as revealed by voltammetric and chrono-amperometric measurements was conducted. The effect of molecular size and function on the metal deposition were examined. Potential suppressor or rate inhibiting species included were dodecyltrimethylammonium chloride [DTAC, CH₃(CH₂)₁₁N⁺(CH₃)₃Cl⁻; manufactured by Fluka], dodecyltrimethylammonium bromide [DTAC, CH₃(CH₂)₁₁N⁺(CH₃)₃Br⁻; manufactured by Fluka]; sodium dodecyl sulfate [SDS, , CH₃(CH₂)₁₁OSO₃ ⁻Na⁺; manufactured by Fisher], 2-butyne-1,4-diol [2-B-1,4-D, HOCH₂C═CCH₂OH, manufactured by Aldrich], saccharin [C₇H₅N0₃S, manufactured by Aldrich], sodium benzenesulfonate [SBS, C₆H₅SO₃ ⁻Na⁺, manufactured by Aldrich], cetyltrimethylammonium chloride [CTAC, CH₃(CH₂)₁₅N⁺(CH₃)₃Cl⁻; manufactured by Alfa Aesar], polyethyleneimine {PEI,-[NH₂ ⁺CH₂CH₂NH⁺(CH₂CH₂NH₃ ⁺)CH₂CH₂ ⁻]_n, 1800 Mw; branched, manufactured by Fluka Alfa Aesarl}, 4-picoline (CH₃C₅H₄N, manufactured by Alfa Aesar), polyethylene glycol [PEG, (—CH₂CH₂O—)_n, 3400 Mw; manufactured by Aldrich). Some sulfur-containing organic additives, such as thiourea (TU, H₂NCSNH₂, manufactured by Alfa Aesar), 3-mercapto-1-propane sulfonic acid, sodium salt [MPS, HS(CH₂)₃SO₃—Na⁺, manufactured by Raschig], bis(3-sulfopropyl) disulfide, sodium salt [SPS, Na₂ ⁺(SO₃ ⁻(CH₂)₃S)₂, manufactured by Raschig], and 3-N,N-dimethylaminodithiocarbamoyl-1-propane sulfonic acid, sodium salt [DPS, Na⁺SO₃ ⁻(CH₂)₃SCSN (CH₃)₂, manufactured by Raschig] were investigated as potential accelerating or depolarizing additives.
This example shows feature filling with a range of effects on morphological evolution. Filling examples were performed at potentials and current densities where negligible depletion of the nickel cations occurred. The following examples were performed at pH 3, which minimized the parasitic effects of hydrogen evolution on the voltammetric measurements and avoided potential complications associated with the H₂bubbles that form readily in more acidic electrolytes.
Ni electrodeposition onto a dielectric substrate metallized with thin Cu seed layer was performed with an electrolytic bath comprising 1 mol/L NiS0₄.6H₂O, 0.2 mol/L NiCl₂.6H₂O, and 0.5 mol/L H₃B0₃dissolved in 18 MΩ cm deionized water. A nickel plate and a saturated calomel electrode (SCE) were used as the counter and reference electrodes, respectively. The cell for the electrochemical experiments was a Teflon cylinder of 5 cm diameter and 8.5 cm height with parallel, vertically oriented working and counter electrodes separated by a distance of 1.3 cm. The SCE reference electrode was fixed midway between the working and counter electrode but laterally positioned so as not to interfere with the current distribution between the other electrodes. A distance of 1.8 cm separated the working and reference electrode and impedance measurements revealed an uncompensated ohmic resistance of 9.35 Ωcm².
The concentrations of the suppressors were fixed at 100 μmol/L with the exception of PEI which was found to exhibit similar inhibition as the other additives at much lower concentrations. In order to more fully characterize the effect of PEI the concentration was varied from 2 to 200 μmol/L. For comparison to the rate-suppressing additives, accelerating sulfur-bearing species were surveyed using a fixed concentration of 100 μmol/L. Feature filling was examined using Cu-seeded trenches approximately 770 nm deep and 5 μm to 210 nm wide to probe the effect of the suppressing and accelerating additives as well as combinations thereof. Depositions were conducted at -0.9 V vs. SCE for 3 min in the base electrolyte with designated concentrations of the additives. In order to minimize seed-layer corrosion, the specimens were immersed into the electrolyte with the potential applied. Feature filling was also examined as a function of deposition time. Specimen cross sections obtained by mechanical polishing followed by ion milling were examined by field emission scanning electron microscopy (FESEM). A subset of samples was also prepared by a single-step focus ion beam milling and examined by SEM. Filled features were also examined by transmission electron microscopy of cross sections prepared using traditional dimpling and ion-milling methods.
PEI was shown to exhibit superior void-free feature filling over the other additives screened. For context the results are compared to those obtained from an additive-free nickel plating electrolyte.
FIG. 11 shows a cross-sectional image of a Ni electrodeposition grown in additive-free solution for 3 min at −0.9 V SCE. Ni was deposited on 5 μm wide trenches 802, 700 nm wide trenches 804, 400 nm wide trenches 806 and 230 nm wide trenches 808. The Ni deposit 810 on the 5 μm wide trench 802 was conformal. The slightly smaller thickness 812 on the sidewalls 814 reflects the difference between the seed-layer 816 thickness on the sidewalls 814 versus the free surface 818 and bottom 820 due to line-of-sight constraints during physical vapor deposition (PVD) preparation. The growth front exhibits noticeable roughness 822. The two widest, low-aspect- ratio trenches 802 and 804 may be void-free while voids 824 are clearly evident in the narrower high-aspect-ratio features of trenches 806 and 808, shown in FIGS. 11( c) and 11(d).
Additions of PEI were shown to induce significant changes in the feature-filling dynamics. Conformal filling of an ˜1 μm wide trench 902 in the additive-free electrolyte is shown in FIG. 12 a. The addition of 5 μmol/L PEI yields superconformal film growth, as shown in FIG. 12 b, by preferential deposition at the bottom 904 and on the deeper sections of the sidewall surfaces 906 of trench 904, while more limited deposition occurs on the neighboring wall surface 908. Preferential deposition of nickel is also evident in the bottom corners 910 of the larger features such as that shown in FIG. 12( c). It is shown that void-free filling of the trenches 904 may persists up to an aspect ratio of at least 2.3 for a mid-height trench width greater than 300 nm.
Ni electrodeposition grown in an electrolytic bath comprising 10 μmol/L PEI for 3 min at −0.9 V showed further evidence of preferential deposition toward the bottoms of the finer features, as shown in FIG. 13( a)-FIG. 13( c). The sloping deposits on the sidewalls 1002 suggests a PEI depletion effect in the higher aspect ratio features that may be congruent with a consumption-driven leveler depletion mechanism, as shown in FIG. 13( b). Limited nickel deposition occurs on the top surfaces 1004, 1006, 1008, and 1010 between the trenches 1005, 1007, 1009, and 1011, as shown in FIG. 13( a)-FIG. 13( d) such that the convex bumps 1012, 1014, 1016, and 1018 are substantially comprised of the copper seed layer. In FIG. 13( e), feature filling and planarity are obtained with modest overburden 1020. However, significant dispersion in the feature-filling dynamics was shown in FIG. 13( f).
In addition to the superconformal feature-filling mode, deposition from 10 μmol/L PEI electrolyte showed a variety of interesting pattern--density-dependent effects. For example, specimens grown at −0.9 V SCE for 3 min showed multiple examples of preferential nucleation and bottom-up growth occurring in the finest and most densely packed trench arrays with negligible deposition evident on neighboring planar or lower feature density regions. Four examples of this behavior are shown in FIGS. 14( a)-14(d). These figures show distinct active and passive areas. The inhomogeneity in growth, a manifestation of self-patterning, enables selective deposition triggered by the nonuniform substrate topography. For example, FIG. 14( d) shows a greater film growth proximate the center of the pattern and lesser film growth proximate each end of the pattern.
Cationic species such as protonated, nitrogen-bearing PEI were shown to substantially inhibit Ni deposition. The addition of PEI to the electrolytic bath was shown to yield bottom-up superconformal feature-filling that also included pattern scale effects whereby feature filling began preferentially in the most densely patterned (high-surface area) regions and was followed by lateral propagation of the metal nucleation and growth fonts. Patterning and designing a three dimensional recess in a dielectric substrate may provide a desired three dimensional shapes and configurations of a ferromagnetic material deposited on the dielectric substrate.
The addition of PEI to the electrolytic bath provided a deposition of the magnetic material with a smooth outer surface and little or no measurable effect on the magnetic properties.
It should be understood that the foregoing relates to exemplary aspects of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.

Claims

1. A process of electrodepositing at least one ferromagnetic metal into a three dimensional pattern within a substrate comprising:

providing a substrate material comprising an electrical conductive three dimensional recessed pattern in at least one surface thereof;

preparing an electrolytic bath comprising at least one ferromagnetic metal cation selected from the group consisting of Ni^{2 +}, Co²⁺, Fe²⁺, Fe³⁺, and combinations thereof;

mixing at least one accelerating, inhibiting, or depolarizing additive into said electrolytic bath;

placing said electrical conductive pattern of said substrate into said electrolytic bath; contacting said electrical conductive pattern of said substrate with said electrolytic bath;

placing a counter electrode into said electrolytic bath;

passing an electrical current through said electrolytic bath between said electrical conductive pattern of said substrate and said counter electrode;

said electrical current being passed between said electrical conductive pattern of said substrate and said counter electrode is such that the potential between the said substrate and a reference electrode is at a value negative of −0.8V SCE, or at an applied current density in the range of 0.1 to 50 mA/cm of the area of the electrically conductive pattern of the substrate, or both; and

depositing at least a portion of said at least one ferromagnetic material into at least a portion of said three dimensional pattern wherein said at least one deposited ferromagnetic material is substantially void-free.

2. The process of claim 1 wherein said substrate is a dielectric substrate and said process further comprises:

depositing an electrical conductive material onto said three dimensional pattern of said dielectric substrate providing an electrical conductive seed layer on said substrate.

3. The process of claim 1 wherein said process step of preferentially depositing said ferromagnetic material into said three dimensional pattern results in a superconformal bottom-up deposition of said ferromagnetic material within said three dimensional pattern.

4. The process of claim 1 wherein said at least one accelerating, inhibiting, or depolarizing additive comprises a nitrogen containing compound.

5. The process of claim 1 wherein said at least one accelerating, inhibiting, or depolarizing additive has a compound selected from the group consisting of cationic surfactants, anionic surfactants, nonionic surfactants, heterocyclic benzimidazole derivatives, and combinations thereof.

6. The process of claim 1 wherein said at least one accelerating, inhibiting, or depolarizing additive comprises a compound selected from the group consisting of polyethyleneimine, 2-mercapto-5-benzimidazolesulfonic acid, and combinations thereof.

7. The process of claim 1 wherein said at least one accelerating, inhibiting, or depolarizing additive comprises polyethyleneimine.

8. The process of claim 1 wherein said at least one accelerating, inhibiting, or depolarizing additive comprises 2-mercapto-5-benzimidazolesulfonic acid.

9. The process of claim 8 wherein said 2-mercapto-5-benzimidazolesulfonic acid is in said electrolytic bath at a concentration of at least 50 μmol/L.

10. The process of claim 1 wherein said three dimensional structure has at least one trench or via with a width ranging from nanometers to macroscopic dimensions.

11. A process of electrodepositing at least one ferromagnetic material into a three dimensional pattern within a substrate comprising:

providing a substrate material having an electrical conductive portion with a three dimensional recessed pattern;

preparing an electrolytic bath comprising said at least one ferromagnetic material and at least one accelerating, inhibiting, or depolarizing additive;

said at least one ferromagnetic material comprising at least one metal cation selected from the group consisting of Ni²⁺, Co²⁺, Fe²⁺, Fe³⁺, and combinations thereof;

placing said electrical conductive portion of said substrate into said electrolytic bath;

contacting said electrical conductive portion of said substrate with said electrolytic bath;

placing a counter electrode into said electrolytic bath;

passing an electrical current through said electrolytic bath between said electrical conductive portion of said substrate and said counter electrode; and

12. The process of claim 11 wherein said process step of passing an electrical current through said electrolytic bath between said electrical conductive portion of said substrate and said counter electrode is such that the potential between the said substrate and a reference electrode is at a value negative of −0.8V SCE.

13. The process of claim 11 wherein said process step of passing an electrical current through said electrolytic bath between said electrical conductive portion of said substrate and said counter electrode is at an applied current density in the range of 0.1 to 50 mA/cm2 of the area of the electrically conductive portion of the substrate.

14. The process of claim 11 wherein said at least one accelerating, inhibiting, or depolarizing additive comprises a nitrogen containing compound.

15. The process of claim 11 wherein said at least one accelerating, inhibiting, or depolarizing additive has a compound selected from the group consisting of cationic surfactants, anionic surfactants, nonionic surfactants, heterocyclic benzimidazole derivatives, and combinations thereof.

16. The process of claim 11 wherein said at least one accelerating, inhibiting, or depolarizing additive comprises a compound selected from the group consisting of polyethyleneimine, 2-mercapto-5-benzimidazolesulfonic acid, and combinations thereof.

17. The process of claim 11 wherein said at least one accelerating, inhibiting, or depolarizing additive comprises polyethyleneimine.

18. The process of claim 11 wherein said at least one accelerating, inhibiting, or depolarizing additive comprises 2-mercapto-5-benzimidazolesulfonic acid.

19. The process of claim 18 wherein said 2-mercapto-5-benzimidazolesulfonic acid is in said electrolytic bath at a concentration of at least 50 μmol/L.

20. A process of electrodepositing at least one ferromagnetic material into a three dimensional pattern within a substrate comprising:

providing a substrate material having an electrical conductive three dimensional recessed pattern in a surface thereof;

said at least one accelerating, inhibiting, or depolarizing additive comprising an additive selected from the group consisting of polyethyleneimine, 2-mercapto-5-benzimidazolesulfonic acid, and combinations thereof;

placing said electrical conductive three dimensional recessed pattern in said substrate into said electrolytic bath;

contacting said electrical conductive three dimensional recessed pattern in said substrate with said electrolytic bath;

placing a counter electrode into said electrolytic bath;

passing an electrical current through said electrolytic bath between said electrical conductive three dimensional recessed pattern in said substrate and said counter electrode; and

depositing at least a portion of said at least one ferromagnetic material into at least a portion of said three dimensional recessed pattern in said substrate wherein said at least one deposited ferromagnetic material is substantially void-free.