US20060188658A1

US20060188658A1 - Pressurized reactor for thin film deposition

Info

Publication number: US20060188658A1
Application number: US11/358,147
Authority: US
Inventors: Robert Grant
Original assignee: SC MATERIALS; SCMATERIALS LLC
Current assignee: Nanoscale Components Inc
Priority date: 2005-02-22
Filing date: 2006-02-21
Publication date: 2006-08-24
Also published as: WO2006091548A2; WO2006091548A3; EP1851360A2

Abstract

An apparatus is provided for use with thin film deposition to permit sequential deposition of discrete conformal layers onto a substrate situated within the apparatus. The apparatus includes a chamber and an outlet in substantial alignment therewith. The chamber includes an inlet to permit introduction of a pressurized gas into the chamber, and a platform on which a substrate may be placed for thin film deposition. The outlet provides an exit through which the substrate may be removed from within the chamber. The apparatus also includes a gate position within the chamber adjacent the outlet for moving between an open position and a closed position relative to the outlet. In the presence of pressurized gas within the chamber, the gate may be pushed against the outlet to provide a substantially pressure tight seal thereat.

Description

RELATED US APPLICATION(S)

The present application claims priority to U.S. patent application Ser. No. 60/655,253, filed Feb. 22, 2005, which application is hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates pressurized reactors, and more particularly to pressurized reactors for use in connection with thin film deposition, such as a chemical fluid deposition (CFD) process.

BACKGROUND ART

Integrated circuits, micro-electromechanical systems (MEMS) devices, flat panel displays, fuel cells, and other substrates are commonly formed today by applying or depositing thin films onto substrates. New techniques in patterning and deposition have led the way in fulfilling Moore's Law (the historical increase in processor speed), as well as the trend toward lower cost via smaller feature sizes and denser circuitry. As integrated circuits and other electronic components continue to be made smaller and smaller moving into the sub-micron or nanometer size with aspect ratio approaching 100 to 1 (depth to width), it has become apparent that existing deposition approaches may not be able to provide the necessary multi-layer conformity on non-planar substrate surfaces. Existing deposition approaches also include other drawbacks, such as slow deposition rates, high carbon content, and poor conductivity.
For example, conformity and stoichiometry control can act as limiting factors for Chemical Vapor Deposition (CVD). CVD can be used to deposit a dielectric, conductive metal oxide or metal using the decomposition of, for instance, metalorganic precursors in a partial vacuum condition. Since deposition is dependent on precursor concentration arriving to a surface, different deposition rates can result in non-conformal or non-uniform deposition on a non-planar substrate having deep features. “Bridging” may also occur with CVD, eventually closing off the deep feature in the substrate prior to complete coating. In addition, a CVD deposited film can include up to about 10% Carbon (i.e., CO₂, CO etc.) contamination, which can affect the effectiveness of the resulting capacitor.
In the case of Atomic Layer Deposition (ALD), growth rates can be exceedingly slow and carbon contamination, similar to CVD, may become an issue, even after an Oxygen annealing process. With ALD, the precursor is decomposed in Oxygen at reduced pressure to deposit only one atomic monolayer at a time. This process, therefore, can be extremely slow for applications where hundreds of layers are needed, such as the case when depositing film thickness of, for example, 600 Angstroms and only 4 Angstroms (i.e., the thickness of a monolayer) can be deposited at a time. Therefore, ALD would not be able to address the speed requirements needed.
Sputtering, on the other hand, is a “line of sight” technology, which can be severely limited in non-planar architecture. In particular, droplets of metal are caused to travel across a high vacuum space from a source target toward a substrate. Momentum does not allow the droplets to easily turn or diffuse into the sides of a deep feature. As a result, this can leave a coating that essentially excludes the sides of the deep feature. Moreover, if several metals are present in the sputtering target source, there can be additional problems, such as those related to fractional distillation that can cause incorrect stoichiometry in the deep feature. A resulting film, therefore, may not perform properly.
To address some of these issues, Chemical Fluid Deposition (CFD) has recently been utilized. In general, CFD is a process by which materials (e.g., metals, metal oxides, or organics) may be deposited from a supercritical or near-supercritical solution via chemical reaction of soluble precursors. Desired materials can be deposited on a substrate, such as a silicon wafer, as a high-purity thin film. The supercritical fluid employed may be used to transport a precursor material to the substrate surface where a reaction takes place, and subsequently transport ligand-derived decomposition products away from the substrate to remove potential film impurities. The entire process takes place in solution under supercritical conditions to provide substantially conformal thin films on small features.
Experimental pressurized reactors have been developed for use with various deposition processes, including those utilizing supercritical gases to deposit thin films on substrates, such as those employed in CFD. These reactors, however, have opening mechanisms that can expose the reactor and the substrate, after deposition, to ambient air or a similar environment that can introduce contaminants onto the substrate. These reactors also have the added inconvenience of having large and forceful opening and/or closing mechanisms that can affect the substrate removal process from within these reactors.
Accordingly, it would be desirable to provide a reactor for use in connection a supercritical gas deposition process to provide conformal thin films on a substrate, and which can minimize exposure of the substrate to the environment to prevent contamination of the substrate, while providing convenience and ease of use.

SUMMARY OF THE INVENTION

The present invention provides, in one embodiment, an apparatus for use with a deposition process utilizing supercritical gases, such as CO₂, and a metal or metal organic precursor, for depositing conformal thin films onto a substrate, for example, a Silicon substrate.
In accordance with an embodiment, the apparatus includes a chamber within which a pressurized gas can be accommodated for thin film deposition of a substrate. The chamber can include an inlet through which the pressurized gas can be introduced and a platform on which a substrate can be placed. The platform, in an embodiment, can include a heating element to raise the temperature of the substrate to a desired level in order to control deposition rate onto the substrate. The apparatus can also include an outlet in substantial alignment with the chamber so that the substrate can subsequently be removed therethrough. A biasing gate may be provided adjacent the outlet for engaging the outlet, so as to minimize outflow of pressure and gas from within the chamber. In an embodiment, the gate can move between an open position and a closed position relative to the outlet. The gate may be designed so as to permit pressure from within the chamber to push the gate against the exit to enhance a seal thereat.
In accordance with another embodiment, an apparatus for use in thin film deposition is provided. The apparatus includes a processing module and an exit portion coupled thereto. The processing module, in an embodiment, includes a chamber within which a substrate may be placed for thin film deposition. In accordance with one embodiment, a heated platform onto which the substrate may be placed can be provided within the chamber. The processing module may also include an inlet through which a mixture of pressurized gas and a precursor may be injected into the chamber. The exit portion, in an embodiment, may include an interior cavity in substantial alignment with the chamber when the exit portion and the processing module are coupled to one another to provide a substantially pressure tight environment. An outlet may be provided in the exit portion so that the substrate can be removed from within the chamber. A biasing gate may further be provided within the exit portion adjacent the outlet for moving between an open position and a closed position. The gate may be designed so as to permit pressure from within the chamber to push the gate against the outlet to enhance a seal thereat.
The present invention also provides a method for thin film deposition. The method initially includes providing an apparatus having a chamber within which a pressurized gas can be accommodated, an outlet in substantial alignment with the chamber and through which a substrate can be removed, and a biasing gate positioned within the chamber adjacent the outlet for engaging the outlet, so as to minimize outflow of pressure and gas from within the chamber. Next, a substrate may be placed within the chamber. Thereafter, the gate may be advanced to a closed position, such that the gate engages the outlet. Subsequently, a mixture of a pressurized gas and a precursor material can be injected into the chamber, and a thin film allowed to be formed on the substrate from the mixture. The injection of the mixture into the chamber provides sufficient pressure to push the gate against the outlet to ensure a substantially pressure tight engagement thereat. In addition, the substrate may be heated to a desired temperature to control the rate of thin film deposition thereon. Once the deposition is complete, and pressure is reduced, the gate may be moved into an open position and the substrate may be removed through the outlet.
The present invention further provides another method for thin film deposition. The method initially includes providing a chamber within which a pressurized gas can be accommodated for thin film deposition of a substrate. Next a substrate may be placed into the chamber through an outlet thereof. Thereafter, the outlet may be blocked from within the chamber so as to minimize outflow of pressure and gas therefrom. Subsequently, a mixture of a pressurized gas and a precursor material may be injected into the chamber, and a thin film be allowed to form on the substrate from the mixture. The injection of the mixture into the chamber, in one embodiment, provides sufficient pressure to further act on the blocking of the outlet, so that a substantially pressure tight engagement can be provided thereat. In addition, the substrate may be heated to a desired temperature to control the rate of thin film deposition thereon. Once the deposition is complete, and pressure is reduced, the outlet may be unblocked and the substrate removed through the outlet.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a cross-sectional view of a pressurized reactor, in accordance with an embodiment of the present invention.
FIG. 2A illustrates a cross-sectional view of an exit portion of the reactor in FIG. 1 along with a gate in a closed position.
FIG. 2B illustrates the gate in FIG. 1 in an open position.
FIG. 3A illustrates a cross-sectional view of the gate in FIGS. 2A-B.
FIG. 3B illustrates a seal for use in connection with the gate in FIG. 3A.
FIG. 4 illustrates a plurality of reactors in FIG. 1 attached to a device for clustering of the deposition process.
FIG. 5 illustrates a system for Chemical Fluid Deposition using supercritical conditions in accordance with an embodiment of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The present invention provides, in one embodiment, an apparatus for use with thin film deposition, including Chemical Fluid Deposition (CFD), such as that utilizing supercritical gases and a metal or metal organic precursor, for sequentially depositing discrete conformal thin films or layers onto a substrate.
In general, Chemical Fluid Deposition (CFD) is a process by which materials (e.g., metals, metal oxides, or organics) may be deposited from a supercritical or near-supercritical solution via chemical reaction of soluble precursors. CFD is generally described in detail in U.S. Pat. No. 5,789,027, which patent is hereby incorporated herein by reference. Desired materials can be deposited on a substrate, such as a silicon wafer, as a high-purity (e.g., better than 99%) thin film (e.g., less than 5 microns). The supercritical fluid employed may be used to transport a precursor material to the substrate surface where a reaction takes place, and to subsequently transport ligand-derived decomposition products away from the substrate to remove potential film impurities. Typically, the precursor in CFD is non-reactive by itself, and a reaction reagent (e.g., a reducing or oxidizing agent) may be mixed into the supercritical solution to initiate the reaction which forms the desired materials. The entire process takes place in solution under supercritical conditions. The process provides a high-purity film at various process temperatures under 250° C., depending on the precursors, solvents, and process pressure used.
Solvents
Solvents that can be used as supercritical fluids are well known in the art and are sometimes referred to as dense gases (Sonntag et al., Introduction to Thermodynamics, Classical and Statistical, 2nd ed., John Wiley & Sons, 1982, p. 40). At temperatures and pressures above certain values for a particular substance (defined as the critical temperature and critical pressure, respectively), saturated liquid and saturated vapor states are identical and the substance is referred to as a supercritical fluid. Solvents that are supercritical fluids are less viscous than liquid solvents by one to two orders of magnitude. In CFD, the low viscosity of the supercritical solvent facilitates improved transport (relative to liquid solvents) of reagent to, and decomposition products away, from the incipient film. Furthermore, many reagents which would be useful in chemical vapor deposition are insoluble or only slightly soluble in various liquids and gases and thus cannot be used in standard CVD. However, the same reagents often exhibit increased solubility in supercritical solvents. Generally, a supercritical solvent can be composed of a single solvent or a mixture of solvents, including for example a small amount (<5 mol %) of a polar liquid co-solvent such as methanol.
It is important that the reagents are sufficiently soluble in the supercritical solvent to allow homogeneous transport of the reagents. Solubility in a supercritical solvent is generally proportional to the density of the supercritical solvent. Ideal conditions for CFD include a supercritical solvent density of at least 0.2 g/cm³or a density that is at least one third of the critical density (the density of the fluid at the critical temperature and critical pressure).

The table below lists some examples of solvents along with their respective critical properties. These solvents can be used by themselves or in conjunction with one another or other solvents to form the supercritical solvent in CFD. The table respectively lists the critical temperature, critical pressure, critical volume, molecular weight, and critical density for each of the solvents.

Critical Properties of Selected Solvents

	T_c	P_c	V_c	Molecular	ρ_c
Solvent	(K)	(atm)	(cm/mol)	Weight	(g/cm³)

CO₂	304.2	72.8	94.0	44.01	0.47
C₂H₆	305.4	48.2	148	30.07	0.20
C₃H₈	369.8	41.9	203	44.10	0.22
n-C₄H₁₀	425.2	37.5	255	58.12	0.23
n-C₅H₁₂	469.6	33.3	304	72.15	0.24
CH₃—O—CH₃	400	53.0	178	46.07	0.26
CH₃CH₂OH	516.2	63.0	167	46.07	0.28
H₂O	647.3	12.8	65.0	18.02	0.33
C₂F₆	292.8	30.4	22.4	138.01	0.61

To describe conditions for different supercritical solvents, the terms “reduced temperature,” “reduced pressure,” and “reduced density” may be used. Reduced temperature, with respect to a particular solvent, is temperature (measured in Kelvin) divided by the critical temperature (measured in Kelvin) of the particular solvent, with analogous definitions for pressure and density. For example, at 333K and 150 atm, the density of CO₂is 0.60 g/cm³; thus, with respect to CO₂, the reduced temperature is 1.09, the reduced pressure is 2.06, and the reduced density is 1.28. Many of the properties of supercritical solvents are also exhibited by near-supercritical solvents, i.e., solvents having a reduced temperature and a reduced pressure both greater than 0.8, but not both greater than 1. One set of suitable conditions for CFD includes a reduced temperature of the supercritical or near-supercritical solvent of between 0.8 and 1.6 and a critical temperature of the fluid of less than 150° C.
Carbon dioxide (CO₂) is a particularly good choice of solvent for CFD. Its critical temperature (31.1° C.) is close to ambient temperature and thus allows the use of moderate process temperatures (<80° C.). It is also unreactive with most precursors used in CVD and is an ideal media for running reactions between gases and soluble liquids or solid substrates. Other suitable solvents include, for example, ethane or propane, which may be more suitable than CO₂in certain situations, e.g., when using precursors which can react with CO₂, such as complexes of low-valent metals containing strong electron-donating ligands (e.g., phospines).
Precursors and Reaction Mechanisms
Precursors may be chosen to yield the desired material on the substrate surface following reaction with the reaction reagent. Materials can include metals (e.g., Cu, Pt, Pd, and Ti), elemental semiconductors (e.g., Si, Ge, and C), compound semiconductors (e.g., III-V semiconductors such as GaAs and InP, II-VI semiconductors such as CdS, and IV-VI semiconductors such as PbS), oxides (e.g., SiO₂and TiO₂), or mixed metal or mixed metal oxides (e.g.; a superconducting mixture such as Y—Ba—Cu—O). Organometallic compounds and metallo-organic complexes are an important source of metal-containing reagents and are particularly useful as precursors for CFD. In contrast, most inorganic metal-containing salts are ionic and relatively insoluble, even in supercritical fluids that include polar modifiers such as methanol.
Some examples of useful precursors for CFD include metallo-organic complexes containing the following classes of ligands: beta-diketonates (e.g., Cu(hfac)₂or Pd(hfac)₂, where hfac is an abbreviation for 1,1,1,5,5,5-hexafluoroacetylacetonate), alkyls (e.g., Zn(ethyl)₂or dimethylcyclooctadiene platinum (CODPtMe₂)), allyls (e.g. bis(allyl)zinc or W(π⁴-allyl)₄), dienes (e.g., CODPtMe₂), or metallocenes (e.g., Ti(π⁵-C₅H₅)₂or Ni(π⁵-C₅H₅)₂). For a list of additional potential precursors see, for example, M. J. Hampden-Smith and T. T. Kodas, Chem. Vap. Deposition, 1:8 (1995).
It should be noted that precursor selection for CVD is limited to stable organometallic compounds that exhibit high vapor pressure at temperatures below their thermal decomposition temperature. This limits the number of potential precursors. On the other hand, CFD obviates the requirement of precursor volatility, and instead replaces it with a much less demanding requirement of precursor solubility in a supercritical fluid.
Any reaction yielding the desired material from the precursor can be used in CFD. However, low process temperatures (e.g., less than 250° C., 200° C., 150° C., or 100° C.) and relatively high fluid densities (e.g., greater than 0.2 g/cm³) in the vicinity of the substrate are important features of CFD. If the substrate temperature is too high, the density of the fluid in the vicinity of the substrate approaches the density of a gas, and the benefits of the solution-based process may be lost. In addition, a high substrate temperature can promote deleterious fragmentation and other side-reactions that lead to film contamination. Therefore a reaction reagent, rather than thermal activation, may be used in CFD to initiate the reaction that yields the desired material from the precursor.
For example, the reaction can involve reduction of the precursor (e.g., by using H₂or H₂S as a reducing agent), oxidation of the precursor (e.g., by using O₂or N₂O as an oxidizing agent), or hydrolysis of the precursor (i.e., adding H₂O). An example of an oxidation reaction in CFD is the use of O₂(the reaction reagent) to oxidize a zirconium beta-diketonate (the precursor) to produce a metal thin film of ZrO₂. An example of a hydrolysis reaction in CFD is water (the reaction reagent) reacting with a metal alkoxide (the precursor), such as titanium tetraisopropoxide (TTIP), to produce a metal oxide thin film, such as TiO₂. The reaction can also be initiated by optical radiation (e.g., photolysis by ultraviolet light). In this case, photons from the optical radiation can be the reaction reagent.
In this supercritical processing approach, chemical selectivity at the substrate can be enhanced by a temperature gradient established between the substrate and the supercritical solution. For example, a gradient of 40° C. to 250° C. or 80° C. to 150° C. can be beneficial. However, to maintain the benefits of CFD, the temperature of the substrate measured in Kelvin, divided by the average temperature of the supercritical solution measured in Kelvin, may typically be maintained between 0.8 and 1.7.
In some cases, the supercritical fluid can participate in the reaction. For example, in a supercritical solution including N₂O as a solvent and metal precursors such as organometallic compounds, N₂O can serve as an oxidizing agent for the metal precursors yielding metal oxides as the desired material. In most cases, however, the solvent in the supercritical fluid is chemically inert.
Reactor
To provide a substantially pressure tight environment during the deposition process so that exposure of the substrate to potential contaminants, for instance, those present in ambient air or a similar environment, can be minimized or controlled, the present invention provides, in one embodiment, a reactor 10, as illustrated in FIG. 1.
As illustrated in FIG. 1, reactor 10 includes a processing module 11 and an exit portion 12 coupled thereto. The processing module 11, in an embodiment, includes a chamber 13 within which a substrate may be placed for thin film deposition. To accommodate the substrate, a platform 14, in one embodiment, may be positioned within chamber 13 to permit the substrate to be placed thereon. In addition, as the condition of the deposition process needs to be preserved within chamber 13, the platform 14 may be provided with a heating element 141 to enable the temperature of platform 14 to be raised. In this manner, the temperature of the substrate on the platform 14 can be maintained substantially similar to that of the processing temperature (e.g., supercritical processing temperature). In one embodiment, the heating element 141 provided may be a commercially available heating element designed to permit the temperature of the platform 14 to be elevated to a temperature range of from about 20° C. to about 400° C., or other desired temperature ranges.
In order to supply the necessary energy to activate the heating element 141, the processing module 11 may include an electrical line 142 extending across wall 111 into the chamber 13 and connecting to the heating element 141. Furthermore, to control the temperature of the heating element 141 and prevent the heating element 141 from being elevated to that beyond a desired level, the processing module 11 may include a feedback controller 143, such as a thermocouple device, extending across wall 111 into the chamber 13 and connecting to the heating element 141. Since the electrical line 142 and the feedback controller 143 extend across wall 111, to maintain the integrity of the environment within the chamber 13 (i.e., minimize leakage of the processing condition therefrom, as well as introduction of possible contaminants thereinto), a seal 144 may each be placed around the electrical line 142 and the feedback controller 143 where each extends across wall 111 and into chamber 13.
The processing module 11, one embodiment, may further include an inlet 15 through which a mixture of a pressurized gas and a deposition (i.e. precursor) material may be injected into the chamber 13. The inlet 15 can be provided with, for instance, a one-way valve to minimize backflow of the pressurized gas and deposition material mixture from the chamber 13. Such a valve may also be a high pressure valve, so as to permit the valve to withstand the high pressures of the gases used in the deposition process. In certain instances where access to within the chamber 13 may be necessary, a service port 16 may be provided. Although only one service port 16 is illustrated, it should be appreciated that additional service ports 16 may be provided, each located at a strategic location on the processing module 11 to provide access to a particular area or component within the processing module 11.
With reference now to the exit portion 12 of the reactor 10, exit portion 12 may be securely coupled to an end of the processing module 11 opposite that of the inlet 15 to provide a pressure tight environment within the chamber 13. In one embodiment, the coupling of the exit portion 12 to the processing module 11 may be accomplished by mounting bolts 17. Of course, other well known mechanisms in the industry, for instance, screws, clamps or any other mounting mechanisms may be used, so long as the exit portion 12 remain securely attached to the processing module 11 to permit the reactor 10 to withstand processing pressure ranging from about 1000 PSI to about 5000 PSI in the presence of a pressurized gas. If desired, a seal, such as an O-ring seal 121 may be positioned between the exit portion 12 and the processing module 11 to ensure a pressure tight engagement thereat. In addition, it should be appreciated that rather than having an independent exit portion 12 and an independent processing module 11, the reactor 10 may be designed so that the exit portion 12 and the processing module 11 can be integral with one another.
The exit portion 12, in an embodiment, may include an interior cavity 18 that terminates in an outlet 19. As illustrated in FIG. 1, the interior cavity 18 and outlet 19 can be designed to be in substantial alignment with the chamber 13 when the exit portion 12 and the processing module 11 are coupled to one another. In this manner, the interior cavity 18 and outlet 19 can provide a substantially clear pathway for a substrate to be removed from within the chamber 13.
Looking now at FIGS. 2A and B, there is shown the exit portion 12 in detail. The exit portion 12, as shown therein, includes a biasing gate 20 positioned adjacent outlet 19. To permit the biasing gate 20 to move between a closed position (FIG. 2A) and an open position (FIG. 2B), the exit portion 12, in one embodiment, may be provided with a recess 21 within which the biasing gate 20 may be located. In accordance with one embodiment of the present invention, the gate 20 includes a head 201, designed for sliding engagement with outlet 19, and an elongated shaft 202 extending from the head 201 into the recess 21. The shaft 202 may be connected, at an end opposite to that attached to the head 201, to a biasing device 22 (See also FIG. 1) capable of moving from a closed position to an open position and vice versa. In the embodiment shown in FIGS. 2A and B, the gate 20 may be designed to move in an up/down, linear, or piston-like motion. To that end, the biasing device 22 may be any linear motion device, such as a stepper motor, air cylinder mechanism, or other similar mechanical or electro-mechanical devices.
Of course, other biasing motion may be provided for gate 20, and as such, other appropriate biasing devices may be necessary. For example, gate 20 may be coupled to a pivoting mechanism at one end of the shaft 202 so that when the gate 20 is pivoted, the head 201 may be moved, in similar manner to that of a pendulum, between an open position and a closed position over the outlet 19.
As shaft 202 is connected to biasing device 22, it needs to extend across wall 23 of the exit portion 12. Accordingly, to maintain the integrity of the environment within the reactor 10, that is, minimizing the leakage of the pressurized processing condition, as well as the introduction of possible contaminants thereinto, an extensible membrane, such as bellow 24, may be situated circumferentially about the shaft 202. Bellow 24, as shown in FIG. 2A, may be manufactured so that it can elongate or extend, when the gate 20 is in the closed position, to accommodate the length of the shaft 202 extending from the recess 21 into the interior cavity 18 of exit portion 12. In addition, bellow 24 may be manufactured so that it can collapse, when the gate 20 is in the open position (FIG. 3B), to accommodate the shortness of the shaft 202 within recess 21. It should be noted that during the course of collapsing, in order to minimize an occurrence of rupture within the bellow 24, a vent 25 may be provided to allow air pressure from within the bellow 24 to exit. In one embodiment, the vent 25 may extend from within the bellow 24 through head 201 of biasing gate 20. Such a vent, of course, may take on other designs, so long as it permits air pressure to escape from within bellow 24.
To prevent the bellow 24 from moving up the shaft 202 and/or exposing the recess 21 to potential contaminants entering through a juncture 231 where the shaft 202 extends across wall 23, bellow 24 may be secured at one end to a base surface 211 of recess 21 and at an opposite end to head 201 of gate 20 adjacent vent 25. To further minimize the potential presence of contaminants through juncture 231, a seal 26, in one embodiment, may be situated between the base surface 211 of recess 21 and the bellow 24, and the bellow 24 may be secured thereto. Moreover, a filter mechanism 251 may be placed over or within vent 25 to capture potential contaminants that may have entered through juncture 231 and into the bellow 24. Such a filter, in an embodiment, may be a sintered metal filter or any other filters that can withstand the supercritical condition within the reactor 10.
With reference now to FIGS. 3A and B, there is shown a head 31 of a biasing gate 30, similar to the head 201 of biasing gate 20. Head 31, in one embodiment, includes an upstream surface 311 directly exposed to a substantially high pressure coming from, for instance, within the chamber 13 of processing chamber 21, and a downstream surface 312 adjacent outlet 32. The downstream surface 312 may be relatively larger than outlet 32, so that when the head 31 is in the closed position, the downstream surface 312 can cover the outlet 32 and substantially minimize the outflow of the processing pressure and gases from within the chamber 13 thereat. In accordance with one embodiment, to facilitate contact between the downstream surface 312 and outlet 32 when the head 31 is in a closed position, surface 312 and outlet 32 may be provided with complementary sloping angles, such as that illustrated in FIGS. 3A and B. Such sloping angles can provide relative easy of engagement between the surface 312 and the outlet 32 when head 31 moves from an open (i.e., down) position to a closed (i.e., up) position or vice versa. Although illustrated with a complementary sloping design, it should be appreciated that other complementary designs may be provided, so long as engagement between the downstream surface 312 and the outlet 32 can be facilitated to provide a substantially pressure tight environment within the processing chamber 13 for supercritical deposition.
To enhance the contact between the downstream surface 312 and the outlet 32 when the head 31 is in the closed position so that a substantially pressure tight engagement can be ensured, an outlet seal 33 may be provided on the downstream surface 312 of head 31. In particular, seal 33 may be placed, in one embodiment, substantially continuously along edges 313 of the surface 312. In accordance with an embodiment, a groove 314 may be provided along edges 313 to permit seal 33 to be securely maintained on the downstream surface 312. Seal 33, in the presence of high pressure, can be deformed to press against wall 34 about outlet 32 to provide a substantially pressure tight engagement. To that end, seal 33 may be made from a deformable material that can withstand supercritical pressure and temperature, while minimizing occurrence of skidding along wall 34. For example, seal 33 may be made from a rubber material, such as silicone rubber, polymers, such as fluoropolymers, or other similar materials.
In accordance with one embodiment of the present invention, seal 33 may be a O-ring seal, such as that shown in FIG. 3A. With such a design, in the presence of substantially high pressure (e.g., supercritical pressure) acting on the upstream surface 311, the head 31, in the closed position as illustrated in FIG. 2A, may be pushed towards outlet 32 to press the O-ring seal against the wall 34 to provide a substantially pressure tight seal between the gate 31 and the outlet 32. Alternatively, seal 33 may be a U-shape seal 35, such as that shown in FIG. 3B. In connection with this design, not only can the pressurized gas from the chamber act on the upstream surface 311, but such pressure can further move over the top and bottom surfaces of head 31 toward the downstream surface 312 and into groove 314. The presence of highly pressurized gas within the groove 314 can act to push rim 351 of U-shape seal 35 against wall 34 to provide a substantially pressure tight seal between the gate 31 and the outlet 32.
The reactor 10, in an embodiment, may be designed for attachment to a positive, negative and/or atmospheric pressure cluster handler 40, such as that illustrated in FIG. 4. The cluster handler 40 shown in FIG. 4 is designed to accommodate a plurality of reactors 10. To permit attachment to handler 40, reactor 10 may be provided with a cluster mounting flange 122 on the exit portion 12, as illustrated in FIG. 1. In addition, a seal, such as an O-ring seal 123 may be provided on the exit portion 12 for placement between the exit portion 12 and the cluster handler 40, so as to ensure a pressure tight engagement thereat. It should be noted that the high pressure generated during the deposition process can help to enhance the engagement between the exit portion 12 of the reactor 10 and the handler 40. A vent line (not shown) may be also be provided to permit communication between the reactor 10 and the handler 40, and to allow the reactor 10 to depressurize toward a transfer pressure prior to the substrate being removed from the reactor 10. The transfer pressure may be positive or negative (vacuum) depending on the situation. Furthermore, upon reaching transfer pressure, the gate within the reactor 10 may be moved to the open position to enable the handler 40 to handle and remove the substrate from within the reactor 10.
Operation
In use, looking now at FIG. 5, there is illustrated, in accordance with one embodiment of the present invention, a system 50 for implementing a CFD deposition protocol (e.g., a hydrogen assisted supercritical deposition protocol) to which a reactor 56, similar to that described above, may be connected at its inlet to the system 50. As shown in FIG. 5, vessels 51, 52, and 53 may each be provided with a distinct precursor for subsequent deposition of an individual discrete film layer onto a substrate, such as a silicon substrate situated in reactor 56. These precursors, examples of which are provided above, may be provided in liquid form and may, in an embodiment, be slightly pressurized by, for instance, N₂gas. Since the deposition process employed by the present invention involves the use of supercritical gases, such as CO₂, high pressure valves 54 which can withstand the pressures of supercritical gases may be used throughout the system 50.
To initiate the deposition process, a micro-volume of a precursor, such as that from vessel 51, may be generated within a coil of small tubing 511. It should be appreciated that a micro-volume each of the precursors from each of vessels 52 and 53 may also be generated within coils 512 and 513 respectively for sequential deposition of subsequent thin film layers on the substrate.
Next, to generate the supercritical gas, a solvent, such as CO₂, may be supplied to a pump 55 in either liquid form, or as a high-pressure gas. In the case the solvent is to be supplied as a gas, the solvent may subsequently be condensed to a liquid. The liquid solvent may next be pressurized to supercritical pressure, for CO₂it is about 1100 PSI or more. It should be noted that whether the solvent is supplied as a gas or a liquid, a reaction agent such as Hydrogen (e.g., H₂gas) may be introduced on the low-pressure or high-pressure side of the pump 55 and allowed to mix with the solvent to assist in the supercritical processing of the precursor for subsequent deposition. Once reaching pressure for supercritical gas conditions, heat may be added to bring this gas mixture up to supercritical temperature. In the case of supercritical CO₂, the temperature is about 31° C.
Upon reaching supercritical pressure and temperature, the supercritical gases (e.g., CO₂and H₂) may be flushed through the coils 511, 512, and 513 containing the respective micro-volumes to substantially dissolve the precursor material. The supercritical gas and precursor mixture may be then directed toward a reactor 56, which may contain or be partially filled with a supercritical gas, such as CO₂, within its processing chamber. It should be appreciated that the system 50, in one embodiment, may be conditioned to the temperature of the supercritical gas, so as to minimize shock and preserve the supercritical condition for the process. In this example, since about 1100 PSI is employed in connection with CO₂, the system 50 may be maintained at about 31° C. to preserve the supercritical condition. The system 50, in an embodiment, may also be provided with, for instance, pressure gauges and metal burst discs to monitor and maintain the safety of the system 50.
Once the supercritical gas and precursor mixture has been introduced and stabilized within the processing chamber of the reactor 56, the temperature of a platform upon which the substrate sits within the chamber of the reactor 56 may be brought up to that similar to the processing temperature. In the case of SCCO₂and, for instance, a Platinum precursor, the platform may be heated to about 60° C. It should be appreciated that since, for example, Hydrogen assisted SCCO₂deposition rates may be zero order dependent on concentration, the temperature may be used as a primary control for the deposition rate. To the extent that other precursors may be used, the temperature of the platform may be varied accordingly up to about 400° C.
After the deposition reaches a desired thickness on the substrate, a pressure valve 57 downstream of the reactor 56 may be opened, so that substantially all the gases (e.g., SCCO₂, H₂) and solutes (e.g., precursor ligands, unused precursor) can leave the system 50. To facilitate removal of the gases and solutes from the reactor 56 and the precursor paths, additional amounts of SCCO₂may be used to flush the system 50 since there is substantially good solubility with the gases and the solutes. In one embodiment, a cleaning additive may be used with SCCO₂to enhance the flushing and cleaning process. A by-product trap, such as an activated carbon canister, may also be provided for use in connection with the cleaning process.
Subsequent to the deposition of the first layer onto the surface of the substrate, other thin film layers may be sequentially deposited atop the first layer on the substrate by repeating the steps disclosed above using, for instance, the precursors from vessel 512 and 513 respectively.
Once the deposition process has completed, reactor 56 may be depressurized toward a transfer pressure. The transfer pressure may be positive or negative (vacuum) depending on the situation. The transfer pressure, in one embodiment, can be achieved through the use of a downstream pressure controller 57 or the use of a connected vent line to the handler (not shown). Thereafter, the substrate may be removed through an outlet in reactor 56.
The system 50, in an embodiment, may be designed so that a closed environment can be provided from loading of the substrate into the reactor 56 to removal of the substrate from within the reactor 56, so as to minimize exposure of the substrate and reactor 56 to potential contaminants during the entirety of such process.
The reactor of the present invention along with its internal gate can be easily adapted for use in the production of integrated circuit. In particular, the reactor 10 of the present invention may be used in connection with system 50 to implement a deposition process utilizing supercritical gases, such as CO₂, and a metal or metal organic precursor to provide conformal thin films onto a high aspect ratio substrate, for example, a Silicon substrate. The high aspect ratio capacitor structures for integrated circuits (Decoupling, Tuning, DRAM, ROM, SRAM, FeRAM etc.), in an embodiment, can include high aspect ratio features over 5:1, and can range from at about 5:1 to about 100:1 depth to width. The reactor 10 may also be used with system 50 to provide conformally deposited thin layers that are substantially pure in content. Each thin film layer, in an embodiment, can be provided with about 2% to about 5% thickness uniformity and substantially without an appreciable amount of Carbon.
It should be noted that although discussed in connection with CFD and the use of supercritical gases, the reactor of the present invention can be adapted for use with other processes. For instance, the reactor of the present invention can be used in connection with chemical reaction or extraction vessels or any other processes where high pressure within the reactor is needed.
The foregoing has outlined, in general, certain aspect of the invention and is to serve as an aid to better understanding the more complete detailed description which is to follow. In reference to such, there is to be a clear understanding that the present invention is not limited to the method or detail of construction, fabrication, material, or application of use described and illustrated herein. Any other variation of fabrication, use, or application should be considered apparent as an alternative embodiment of the present invention.

Claims

1. An apparatus for use in thin film deposition, the apparatus comprising:

a chamber within which a pressurized gas can be accommodated for thin film deposition of a substrate;

an outlet in substantial alignment with the chamber and through which the substrate can be removed; and

a biasing gate positioned within the chamber adjacent the outlet for engaging the outlet to minimize outflow of pressure and gas from within the chamber.

2. An apparatus as set forth in claim 1, wherein the chamber includes an inlet through which the pressurized gas can be introduced.

3. An apparatus as set forth in claim 1, wherein the chamber includes a platform on which the substrate can be placed.

4. An apparatus as set forth in claim 1, wherein the platform includes a heating element to permit heating of the platform to a desired temperature to control deposition rate onto the substrate.

5. An apparatus as set forth in claim 1, wherein the biasing gate includes a head for engagement with the outlet, and an elongated shaft extending therefrom.

6. An apparatus as set forth in claim 5, wherein the shaft is connected, at an end opposite to that attached to the head, to a biasing device capable of moving the gate between a closed position, where the head engages the outlet, and an open position, where the head is situated away from the outlet.

7. An apparatus as set forth in claim 5, wherein the gate includes a collapsible membrane situated circumferentially about the shaft to minimize introduction of contaminants across a juncture where the shaft is connected to the biasing device.

8. An apparatus as set forth in claim 7, wherein the collapsible membrane includes a vent extending from within the membrane through the head of the gate to permit air or pressure from within the membrane to exit, so as to minimize an occurrence of rupture within the membrane when it is collapsed.

9. An apparatus as set forth in claim 8, wherein the vent includes a filter to prevent any contaminants present within the bellow from entering into the chamber of the apparatus.

10. An apparatus as set forth in claim 5, wherein the gate includes a seal positioned on the head of the gate along a surface adjacent the outlet to provide a pressure tight engagement with the outlet.

11. An apparatus as set forth in claim 5, wherein the outlet and the head of the gate include complementary sloping angles to facilitate ease of engagement between the head and the outlet.

12. An apparatus as set forth in claim 1, wherein the chamber and the outlet are positioned within separate components of the apparatus.

13. An apparatus as set forth in claim 1, wherein the chamber and the outlet are positioned within an integral component comprising the apparatus.

14. A reactor for use in thin film deposition, the reactor comprising:

a processing module having a chamber within which a substrate can be placed for thin film deposition;

an exit portion coupled to the processing module for providing a substantially pressure tight environment within a pressurized gas can be accommodated;

an outlet on the exit portion through which the substrate can be removed; and

a biasing gate positioned within the exit portion and adjacent the outlet for engaging the outlet to minimize outflow of pressure and gas from within the chamber.

15. A reactor as set forth in claim 14, wherein the processing module includes an inlet through which the pressurized gas can be introduced into the chamber.

16. A reactor as set forth in claim 14, wherein the processing module includes a platform on which the substrate can be placed.

17. A reactor as set forth in claim 14, wherein the platform includes a heating element to permit heating of the platform to a desired temperature to control deposition rate onto the substrate.

18. A reactor as set forth in claim 17, wherein the processing module includes a feedback controller to control the temperature of the heating element.

19. A reactor as set forth in claim 14, wherein the exit portion includes a cavity in substantially alignment with the chamber and the outlet to provide a pathway along which the substrate can be removed from the chamber.

20. A reactor as set forth in claim 14, wherein the exit portion includes a recess within which the biasing gate can be positioned.

21. A reactor as set forth in claim 14, wherein the biasing gate includes a head for engagement with the outlet and an elongated shaft extending therefrom.

22. A reactor as set forth in claim 21, wherein the shaft is connected, at an end opposite to that attached to the head, to a biasing device capable of moving the gate between a closed position, where the head engages the outlet, and an open position, where the head is situated away from the outlet.

23. A reactor as set forth in claim 21, wherein the gate includes a substantially collapsible membrane situated circumferentially about the shaft to minimize introduction of contaminants across a juncture where the shaft is connected to the biasing device.

24. A reactor as set forth in claim 23, wherein the collapsible membrane is attached at one end to a seal positioned at the juncture to further minimize introduction of contaminants across the juncture.

25. A reactor as set forth in claim 23, wherein the collapsible membrane includes a vent extending from within the membrane through the head of the gate to permit air from within the membrane to exit, so as to minimize an occurrence of rupture within the membrane when it is collapsed.

26. A reactor as set forth in claim 25, wherein the vent includes a filter to prevent any contaminants present within the bellow from entering into the chamber of the apparatus.

27. A reactor as set forth in claim 21, wherein the gate includes a seal positioned on the head of the gate along a surface adjacent the outlet to provide a pressure tight engagement with the outlet.

28. A reactor as set forth in claim 27, wherein the seal includes one of an O-Ring seal or a U-Shape seal capable of being deformed to provide a pressure tight engagement with the outlet.

29. A reactor as set forth in claim 21, wherein the outlet and the head of the gate include complementary sloping angles to facilitate ease of engagement between the head and the outlet.

30. A reactor as set forth in claim 14, wherein the exit portion is designed to engage a cluster handler to minimize contamination of the substrate during removal of the substrate from the chamber of the reactor.

31. A method for depositing a thin film onto a substrate, the method comprising:

providing an apparatus having a chamber within which a pressurized gas can be accommodated for thin film deposition of a substrate, an outlet in substantial alignment with the chamber and through which a substrate can be removed, and a biasing gate positioned within the chamber adjacent the outlet for engaging the outlet to minimize outflow of pressure and gas therefrom;

placing a substrate within the chamber;

advancing the gate to a closed position, such that the gate engages the outlet;

injecting into the chamber a mixture of a pressurized gas and a material for deposition onto the substrate; and

allowing a thin film to be formed on the substrate from the mixture.

32. A method as set forth in claim 31, wherein the step of providing includes placing the apparatus within a closed environment in order to minimize subsequent occurrence of contamination to the substrate.

33. A method as set forth in claim 31, wherein the step of placing includes moving the substrate across the outlet into the chamber.

34. A method as set forth in claim 31, wherein the step of injecting includes permitting pressure from the mixture to push the gate against the outlet, so as to provide a substantially pressure tight engagement between the gate and the outlet.

35. A method as set forth in claim 31, wherein the step of allowing includes heating the substrate to control a deposition rate of the thin film onto the substrate.

36. A method as set forth in claim 31, further including:

moving the gate to an open position, such that the gate provides access to the substrate within the chamber through the outlet.

37. A method as set forth in claim 36, wherein the step of moving includes depressurizing the chamber to a transfer pressure.

38. A method as set forth in claim 36, further including:

removing, through the outlet, the substrate from within the chamber.

39. A method for depositing a thin film onto a substrate, the method comprising:

providing a chamber within which a pressurized gas can be accommodated for thin film deposition of a substrate;

placing a substrate into the chamber through an outlet thereof;

blocking the outlet from within the chamber to minimize outflow of pressure and gas therefrom;

allowing a thin film to be formed on the substrate from the mixture.

40. A method as set forth in claim 39, wherein the step of providing includes connecting the chamber to a closed environment in order to minimize subsequent occurrence of contamination to the substrate.

41. A method as set forth in claim 39, wherein the step of injecting includes permitting pressure from the mixture to further act on the blocking of the outlet, so as to provide a substantially pressure tight engagement thereat.

42. A method as set forth in claim 39, wherein the step of allowing includes heating the substrate to control a deposition rate of the thin film onto the substrate.

43. A method as set forth in claim 31, further including:

unblocking the outlet so as to provide, through the outlet, access to the substrate within the chamber.

44. A method as set forth in claim 43, wherein the step of unblocking includes depressurizing the chamber to a transfer pressure.

45. A method as set forth in claim 43, further including:

removing, through the outlet, the substrate from within the chamber.