US20040104119A1

US20040104119A1 - Small volume electroplating cell

Info

Publication number: US20040104119A1
Application number: US10/308,848
Authority: US
Inventors: Sergio Edelstein; Peter Hey; Yezdi Dordi
Original assignee: Applied Materials Inc
Current assignee: Applied Materials Inc
Priority date: 2002-12-02
Filing date: 2002-12-02
Publication date: 2004-06-03

Abstract

A method and apparatus for plating a metal onto a substrate. The apparatus generally The apparatus generally includes a substrate support member configured to support a substrate during a plating process, a cathode clamp ring detachably positioned to circumscribe a perimeter of the substrate and a movable anode assembly disposed above the substrate, wherein the anode assembly is movable in a direction generally perpendicular the substrate. The apparatus generally further includes a fluid inlet formed through the anode assembly, the fluid inlet being configured to supply a plating solution to the processing area sufficient to electrically connect the anode assembly to the substrate. The method generally includes supplying a plating solution to a processing chamber, the processing chamber being defined by a movable anode assembly disposed above the substrate and a cathode clamp ring detachably positioned to circumscribe the perimeter of the substrate, wherein the plating solution is supplied at a rate sufficient to electrically connect the anode assembly to the substrate and plating a metal from the plating solution onto the substrate.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to deposition of a metal layer onto a substrate. More particularly, the embodiments of the present invention relate to electroplating a metal layer onto a substrate.

2. Description of the Related Art

Metallization for sub-quarter micron sized features is a foundational technology for present and future generations of integrated circuit manufacturing processes. In devices such as ultra large scale integration-type devices, i.e., devices having integrated circuits with more than a million logic gates, the multilevel interconnects that lie at the heart of these devices are generally formed by filling high aspect ratio interconnect features with a conductive material, such as copper or aluminum. Conventionally, deposition techniques such as chemical vapor deposition (CVD) and physical vapor deposition (PVD) have been used to fill these interconnect features. However, as interconnect sizes decrease and aspect ratios increase, void-free interconnect feature fill via conventional metallization techniques becomes increasingly difficult. As a result thereof, plating techniques, such as electrochemical plating (ECP) and electroless plating, for example, have emerged as viable processes for filling sub-quarter micron sized high aspect ratio interconnect features in integrated circuit manufacturing processes.

In an ECP process sub-quarter micron sized high aspect ratio features formed on a substrate surface may be efficiently filled with a conductive material, such as copper, for example. ECP plating processes are generally two stage processes, wherein a seed layer is first formed over the surface features of the substrate, and then the surface features of the substrate are exposed to an electrolyte solution while an electrical bias is simultaneously applied between the substrate and an anode positioned within the electrolyte solution. The electrolyte solution is generally rich in ions to be plated onto the surface of the substrate. Therefore, the application of the electrical bias causes these ions to be urged out of the electrolyte solution and to be plated as a metal on the seed layer. The plated metal, which may be copper, for example, grows in thickness and forms a copper layer that fills the features formed on the substrate surface.

Present designs of cells for electroplating a metal on semiconductor substrates are generally based on a fountain plater type configuration. FIG. 1 illustrates a cross sectional view of a simplified exemplary fountain plater. Generally, the

fountain plater

10 includes an electrolyte container 12 having a top opening, a substrate holder 14 disposed above the electrolyte container 12, an anode 16 disposed at a bottom portion of the electrolyte container 12, and a cathode 20 contacting the substrate 18. The cathode 20 includes a plurality of contact pins distributed about the peripheral portion of the substrate 18 to provide an electrical bias to the substrate surface. The semiconductor substrate 18 is generally positioned a fixed distance above the electrolyte container 12, and the electrolyte generally impinges perpendicularly on the substrate plating surface. Because of the possible dispersion effects of the electrical current at the exposed edges of the substrate 18 and the possible non-uniform flow of the electrolyte, the fountain plater 10 may provide non-uniform current distribution, particularly at the region near the edges and at the center of the substrate 18, which may result in non-uniform plating on the substrate. The electrolyte flow uniformity at the center of the substrate 18 can be improved by rotating the substrate 18. However, the plating uniformity still may deteriorate as the boundaries or edges of the substrate are approached.

Therefore, there remains a need for a reliable, consistent copper electroplating technique to deposit and form copper layers on semiconductor substrates having nanometer-sized, high aspect ratio features. There is also a need for a face-up electroplating system that allows fast substrate processing and increases throughput with a small volume of plating solution. Furthermore, there is a need for an apparatus for delivering a uniform electrical power distribution to a substrate surface and a need for an electroplating system that provides uniform deposition on the substrate surface.

SUMMARY OF THE INVENTION

Embodiments of the invention generally include an apparatus for plating a metal onto a substrate surface. The apparatus generally includes a substrate support member configured to support a substrate during a plating process, a cathode clamp ring detachably positioned to circumscribe a perimeter of the substrate and a movable anode assembly disposed above the substrate, wherein the anode assembly is movable in a direction generally perpendicular the substrate. The apparatus generally further includes a fluid inlet formed through the anode assembly, the fluid inlet being configured to supply a plating solution to the processing area sufficient to electrically connect the anode assembly to the substrate.

Embodiments of the invention further include a method for plating a metal onto a substrate. The method generally includes supplying a plating solution to a processing chamber, the processing chamber being defined by a movable anode assembly disposed above the substrate and a cathode clamp ring detachably positioned to circumscribe the perimeter of the substrate, wherein the plating solution is supplied at a rate sufficient to electrically connect the anode assembly to the substrate and plating a metal from the plating solution onto the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. [0010]
FIG. 1 (Prior Art) illustrates a cross-sectional view of an exemplary fountain plater. [0011]
FIG. 2 illustrates a cross-sectional view of an exemplary plating cell. [0012]
FIG. 3 illustrates a cross-sectional view of an exemplary anode assembly. [0013]
FIG. 4 illustrates a cross-sectional view of another anode assembly. [0014]
FIG. 5 illustrates a cross-sectional view of another anode assembly.[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 2 illustrates a cross-sectional view of an [0016] exemplary plating cell 100 with a substrate 116 in a processing position. The plating cell 100 generally includes an enclosure 126 having a substrate support member 102 and an anode assembly 104. The substrate support member 102 generally includes a conductive base plate 130 providing a cathode connection to a cathode clamp ring 108. The substrate support member 102 is generally disposed in a bottom portion of the enclosure 126. The anode assembly 104, discussed in further detail below, is electrically connected to a power supply 106 via an electrical line 128. The plating cell 102 may further include a vacuum chuck to secure the substrate 116 onto a substrate supporting surface 132 on the substrate support member 102 during processing.
In the loading position, the [0017] cathode clamp ring 108, which may be supported by an annular catch cup 110, is generally disposed in a middle portion of the plating cell 100 between the substrate support member 102 and the anode assembly 104. The cathode clamp ring 108 is positioned in the plating cell 100 such that the movement of the substrate support member 102 from a load/transfer position (not shown), to the processing position lifts the cathode clamp ring 108 slightly off the catch cup 110. The load/transfer position is discussed in detail in U.S. Pat. No. 6,416,647, filed on Apr. 19, 1999, which is hereby incorporated by reference.
The [0018] cathode clamp ring 108 preferably includes an outer portion having a downwardly sloping surface 166 that overlaps an inner terminus 168 of the catch cup 110 to assist the plating solution flow into the catch cup 110. The inner terminus 168 includes a ridge 170 corresponding to a recess 172 on the bottom surface 174 of the cathode clamp ring 108. The ridge 170 supports the cathode clamp ring 108 when the substrate support member 102 is not engaged in a deposition position. When the substrate support member 102 is engaged in the deposition position, the cathode clamp ring 108 is lifted from the ridge 170 and is supported on the substrate deposition surface 176.
The electrical power is delivered by the [0019] cathode clamp ring 108 to the substrate deposition surface 176 through a contact portion 178 of the cathode clamp ring 108. To provide electrical power to the cathode clamp ring 108, one or more cathode contacts 180 are fixedly secured to a bottom surface 146 of the conductive base plate 130 of the substrate support member 102 and extend radially outward to electrically contact a bottom surface 174 of the cathode clamp ring 108. Upon rotation, the electrical power is conducted through the rotating shaft 134 to the conductive base plate 130, then through one or more cathode contacts 180 secured onto the conductive base plate 130, and then to a bottom surface 174 of the cathode clamp ring 108. Alternatively, the cathode clamp ring 108 is fixedly connected to the power supply 106 through connection wires (not shown).
The rotating [0020] shaft 134 extends through a lift pin platform 136 having a plurality of lift pins 138 disposed thereon. A lift platform actuator 142 moves the lift pin platform 136 vertically to lift and lower a substrate 116 for transfer into and out of the plating cell 100. A flexible bellow 144, preferably made of polyethylene, is disposed around each lift pin 138, to provide a splash seal against plating solutions, rinsing solutions, and other processing chemicals. The flexible bellow 144 is attached from a top surface of the lift pin platform 136 to a bottom surface of the conductive base plate 146 of the substrate support member 102. The flexible bellow 144 compresses when the lift pin platform 136 is elevated by the lift platform actuator 142 and stretches when the lift pin platform 136 is resting on a platform ridge 148. Each flexible bellow 144 also maintains a seal when subjected to a slight side load, such as when the substrate support member 102 rotationally accelerates or decelerates.
To prevent plating solutions, rinsing solutions, and other process chemicals from contacting components disposed in the central portion of the plating [0021] cell 100, such as the lift platform actuator 142 and the shaft sleeve 150, a splash guard 152 is generally attached to an outer portion of a lower surface of the lift pin platform 136. The splashguard 152 includes a cylindrical downward extension that is disposed radially outward of an upwardly extending inner container wall 154. The inner container wall 154 is a cylindrical upward extension from the enclosure bottom 156 of the plating cell 100 that holds the process solutions to be pumped out of the system through a solution outlet 114.
To provide rotational movement to the [0022] substrate support member 102, a rotary actuator 158 is disposed on an actuator platform 160 and connected to the rotating shaft 134. The rotary actuator 158 rotates the rotating shaft 134 freely within the shaft sleeve 150. During deposition, the rotary actuator 158 rotates or oscillates the substrate support member 102 about a central axis through the rotating shaft 134. Generally, the rotary actuator 158 rotates the support member 102 at between about 10 revolutions or cycles per minute to about 50 RPM or cycles per minute. The rotation or oscillation of the substrate support member 102 provides uniform exposure of the plating solution to the substrate deposition surface 176 promoting uniform metal deposition. In the alternative, the anode assembly 104 may be rotated. Deposition uniformity is further promoted by continuous cathode electrical contact provided by the cathode clamp ring 108. The cathode clamp ring 108 operates to distribute a uniform current density across the substrate deposition surface 176.
To move the [0023] substrate support member 102 vertically, a vertical actuator 162 extends and retracts a shaft 164 connected to the actuator platform 160. The vertical actuator 162 is disposed outside of the cell 100 on the cell bottom 156, and the shaft 164 extends through the cell bottom 156 and is attached to a bottom surface of the actuator platform 160. These actuators may be fluid cylinders, screw-type actuators, or any other actuator capable of producing longitudinal movements. In addition, a substrate transfer actuator 122 vertically adjusts the anode assembly 104 to set an anode assembly 104 to substrate 116 distance. The distance may be from about 2 mm to about 20 mm. The anode assembly 104 may be sized to recess within the contact ring 108 upon vertical adjustment, e.g., during plating, so that the anode assembly 104 is in electrical contact with the plating solution. In addition, plating solution may flow through the anode assembly 104 to provide additional plating solution or to provide movement within the existing plating solution. Alternatively, the anode assembly 104 may be sized to rest upon the contact ring 108 upon vertical adjustment. When the anode assembly 104 rests upon the contact ring 108, an insulator may be utilized to separate the anode assembly 104 and the contact ring 108.
The [0024] cell 100 additionally includes a sidewall 124 having a slit 118 formed therein for receiving and discharging a substrate 116, e.g., loading and transferring the substrate 116. The plurality of lift pins 136 extends through vertical bores in the substrate support member 102 and lifts the substrate 116 above a robot blade (not shown). The robot blade then retracts out of the cell 100 and the slit valve 120 closes the slit opening 118. Once the substrate 116 is in the processing position, a plating solution pump (not shown), which is connected to a plating solution inlet 112, pumps plating solution from a plating solution reservoir (not shown) into the plating cell 100. Generally, a plating solution outlet 114 is connected to a plating solution drain (not shown) formed in the catch cup 110 to return the plating solution back to the plating solution reservoir to be re-circulated to the plating cell 100.
The plating solution fills a processing area defined by the [0025] substrate 116, i.e., the processing area bottom, and the contact ring 108, i.e., the sidewalls. Therefore, the volume of the processing area and the resulting volume of the plating solution utilized are dependent upon the size of the substrate 116 and the height of the contact ring 108. In addition, the volume is dependent upon the distance of the anode assembly 104 from the substrate 116. Generally the anode assembly 104 is from about 2 mm to about 20 mm from the substrate 116. Preferably, the anode assembly 104 is from about 2 mm to about 10 mm from the substrate 116.
FIG. 3 illustrates a cross-sectional view of an [0026] exemplary anode assembly 200. The anode assembly 200 may be used in the plating cell 100 described above, or another plating cell capable of processing semiconductor substrates in the face-up position. The anode assembly 200 and the substrate 116 and clamp ring 108 define a cell chamber 208, e.g., a processing area. The cell chamber 208 generally has a volume of from about 0.5 L to about 1.9 L.
The [0027] anode assembly 200 generally includes an anode plate 202 and a hood 204. The anode plate 202 generally has a circular cross-section. The anode plate 202 preferably includes a consumable metal that can dissolve in the electroplating solution to provide the metal particles to be deposited onto the substrate deposition surface. The hood 204, which is electrically insulated from the anode plate 202, depends from the outer periphery of the anode plate 202 and may be made of anodic material, which is the same or different from the material of the anode plate 202. For example, the anode plate 202 may be formed of a mesh material. Alternatively, the anode plate 202 and hood 204 are each made of consumable metal particles encased in a fluid permeable membrane such as a porous ceramic plate. An alternative to the consumable anode plate is a non-consumable anode plate that is perforated or porous for passage of the electroplating solution therethrough. However, when a non-consumable anode plate is used, the electroplating solution requires a metal particle supply to continually replenish the metal particles to be deposited in the process.
As described above, the [0028] contact ring 108 is in electrical communication with the cathode terminal of a power supply (not shown). The power source discussed in reference to FIG. 2 generally includes controls for varying the voltage and polarity of the anode plate 202 and the hood 204. For example, to ensure plating in a central portion of the substrate, the hood 204 may be electrically isolated to prevent ions from plating on the hood 204.
The [0029] hood 204 generally is secured to the anode plate 202 by an insulating ring 206. The hood 204 is sized to substantially cover the substrate 116 and the clamp ring 108 from the outer edges of the anode plate 202 extending downward towards the substrate 116.
The flow of electrolyte through the [0030] processing chamber 208 is controlled by the size of an annular opening 210, e.g., the distance between the hood 204 and the clamp ring 108. The annular opening 210 is sized in relation to the electrolyte flow rate to maintain the electrolyte in the chamber 208 at a predetermined level during the plating process. Generally, the flow of plating solution continues during plating to retain electrical contact between the anode plate 202 and the substrate 116. In addition, the flow of electrolyte into the processing chamber 208 is generally equal to the flow of electrolyte out of the processing chamber through the annular opening 210 and the consumption of electrolyte due to plating on the substrate. Generally, the processing chamber 208 is full of electrolyte throughout plating to maintain an electrical connection between the anode and the substrate.
In operation, the plating cell provides a small volume (electrolyte volume) [0031] processing chamber 208 that may be used for copper electrochemical plating processes, for example. A substrate 116 is first immersed into a plating solution contained within the processing chamber 208. Once the substrate is immersed in the plating solution, which generally contains copper sulfate, chlorine, and one or more of a plurality of plating additives (levelers, suppressors, accelerators, etc.) configured to control plating parameters, an electrical plating bias is applied between a seed layer on the substrate and the anode 202 positioned above the substrate 116. The electrical plating bias generally operates to cause metal ions in the plating solution to deposit on the cathodic substrate surface 116. The plating solution is continually circulated through the processing chamber 208 via fluid inlets and outlets.
FIG. 4 illustrates a cross-sectional view of another [0032] anode assembly 300. The embodiment shown in FIG. 3 includes the same components as the embodiment shown in FIG. 2, except that the anode plate 304 does not include a hood. Thus, the cell chamber 302 is defined by the downwardly facing surface of the anode plate 304, the upwardly facing surface of the substrate 116, and the clamp ring 108, e.g., the clamp ring 108 operates as sidewalls for the chamber 302, thereby defining the volume of the chamber 302. The distance of the anode plate 304 from the substrate 116 is generally minimized. For example, the distance may be from about 2 mm to about 20 mm, resulting in a small chamber volume. Alternatively, the distance may be from about 2 mm to about 10 mm. The precise volume of the chamber is determined by the vertical actuator setting.
FIG. 5 illustrates yet another embodiment of an [0033] anode assembly 400. The anode assembly 400 includes an anode plate 402. The anode plate 402 generally includes a plurality of annular anode segments that are separated by insulators 404. The insulators 404 may be annular spaces, plastic rings, or other means capable of insulating the anode segments from one another. The individual anode segments allow selective plating operation by providing individual voltage control for each anode segment. Selective operation provides control over the flow of cations adhering and flowing to the cathode/substrate 116, thereby resulting in uniform plating upon the substrate 116. Although the anode assembly 400 may be used alone, the anode assembly 400 may also be used in conjunction with either of the embodiments illustrated in FIGS. 2 and 3.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. [0034]

Claims

What is claimed is:

1. An apparatus for plating a metal onto a substrate surface, comprising:

a substrate support member configured to support a substrate during a plating process;

a cathode clamp ring detachably positioned to circumscribe a perimeter of the substrate;

a movable anode assembly disposed above the substrate, wherein the anode assembly is movable in a direction generally perpendicular the substrate; and

a fluid inlet formed through the anode assembly, the fluid inlet being configured to supply a plating solution to the processing area sufficient to electrically connect the anode assembly to the substrate.

2. The apparatus of claim 1, wherein the movable anode assembly is configured to adjust a distance between an anode plate of the anode assembly and the substrate.

3. The apparatus of claim 2, wherein the distance is between about 2 mm and about 20 mm.

4. The apparatus of claim 1, wherein movable anode assembly includes a disk shaped anode plate surrounded by an annular hood member.

5. The apparatus of claim 3, wherein the hood member is manufactured from an insulating material.

6. The apparatus of claim 4, wherein the hood member is manufactured from a metal and is connected to a power source to selectively control current passing between the anode plate and the substrate.

7. The apparatus of claim 1, wherein movable anode assembly comprises a disk shaped anode plate having an aperture formed therein, the aperture forming the fluid inlet.

8. The apparatus of claim 7, wherein the anode plate is positioned in parallel relationship to a plating surface of the substrate.

9. The apparatus of claim 7, further comprising an actuator configured to actuate the anode plate toward and away from the substrate.

10. The apparatus of claim 1, wherein the cathode clamp ring is configured to be positioned over an upper perimeter surface of the substrate support member in a manner such that the cathode clamp ring electrically engages the perimeter portion of the substrate and forms a processing volume above the substrate and within the clamp ring.

11. The apparatus of claim 10, wherein the processing volume is as deep as the cathode clamp ring is tall and is sized to receive an anode plate therein.

12. A method for plating a metal onto a substrate, comprising:

supplying a plating solution to a processing volume, the processing volume being defined by a movable anode assembly disposed above the substrate and a cathode clamp ring detachably positioned to circumscribe a perimeter of the substrate, wherein the plating solution is supplied at a rate sufficient to electrically connect the anode assembly to the substrate; and

plating a metal from the plating solution onto the substrate.

13. The method of claim 12, further comprising moving the anode assembly to define a distance between the anode plate and the plating surface.

14. The method of claim 12, wherein the anode assembly comprises an anode plate including a plurality of metal segments, the plurality of metal segments being separately controlled by a power source to provide uniform metal deposition.

15. The method of claim 14, wherein the plurality of metal segments are separated by an insulating material.

16. The method of claim 12, wherein the anode assembly further comprises a hood depending from the periphery of the anode plate.

17. The method of claim 16, further comprising releasing electrolyte from the processing chamber through an annular opening, the annular opening being defined by a distance between the hood and the cathode clamp ring.

18. The method of claim 17, further comprising supplying plating solution to the processing chamber at a rate essentially equal to the rate of release.

19. The method of claim 12, further comprising rotating the substrate.

20. The method of claim 12, further comprising adjusting the anode assembly to form a cell chamber having a volume of from about 0.5 L to about 1.9 L.

21. The method of claim 14, wherein the distance between the substrate and the anode plate is between about 2 mm and 20 mm.

22. The method of claim 14, wherein the distance between the substrate and the anode plate is between about 2 mm and about 10 mm.

23. An electrochemical processing cell, comprising:

a substrate support member having a circular upper substrate support surface formed thereon;

an annular cathode contact ring configured to releasably engage an outer perimeter of the substrate support surface and electrically contact a substrate positioned thereon; and

a disk shaped anode configured to be received within an inner diameter of the annular cathode contact ring, the disk shaped anode being movable between an processing position and a loading position.

24. The processing cell of claim 23, wherein the disk shaped anode further comprises a fluid inlet configured to deliver a processing fluid to a processing volume defined by the anode, the cathode contact ring, and the substrate.

25. The processing cell of claim 23, wherein the contact ring forms an annular wall above the substrate, the annular wall being configured to maintain a volume of a plating solution therein.

26. The processing cell of claim 23, wherein the anode further comprises a hood member.