Counter-electrode for electrodeposition and electroetching of resistive substrates
Various counter-electrodes for electroplating, electrodeposition or anodizing of substrates are disclosed. According to certain embodiments, multi-segmented counter-electrodes are provided. According to additional embodiments, counter-electrodes having concave or convex top surfaces are provided. The disclosed counter-electrodes enable greater control over electrodeposition, electroetching and anodizing processes for resistive substrates, as well as more uniform plating and etching of resistive substrates. Methods for electroplating, electrodeposition or anodizing of resistive substrates using multi-segmented counter-electrodes are also provided.
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In recent applications of electroplating such as Damascene plating of on-chip interconnects, the need for smaller electronic devices has resulted in the tendency to use thinner conductive seed layers, or the tendency to eliminate the conductive layer and plate on a high resistivity layer. The high active area density in Damascene plating, along with trends towards larger wafers, higher plating rates and stringent requirements of thickness uniformity have increased the need to control what is known as the “terminal effect.” The terminal effect, which is caused by the high ohmic drop within the seed layer and the plated deposit, results in highly non-uniform current distribution in the vicinity of electrical contacts during plating. The highly non-uniform current distribution can cause tremendous non-uniformity in thickness of the electrodeposited metal between areas in the vicinity of the electrical contacts and areas remote from these contacts. Similar effects are seen when the reversed polarity is used and the electrochemical process is one of electroetching or anodizing.
In many cases, the seed layer is of high resistivity and the resistance to passing current through the full distance between the terminal and the center of the electroprocessed substrate is very high. In such cases, the current lines will concentrate near the terminal and almost nothing will deposit at the substrate center because the high resistance of the electrode dominates the overall resistance of the electroplating circuit.
One known way to overcome the above-described terminal effect is to use current deflectors, known as “thieves”, that drive the current outward and away from the edges of the substrate and thus increase the relative current density to the substrate center and overall current uniformity. However, the use of current thieves in manufacturing significantly raises the cost of equipment processes and maintenance, because a current thief will deposit (or oxidize) the same metal or material as the workpiece, while consuming additional plating solution, and furthermore will need to be periodically stripped.
In view of the above, there remains a need for devices and methods for reducing the terminal effect and thereby promoting greater thickness uniformity in the electroprocessing of substrates.
SUMMARYVarious embodiments of novel counter-electrodes are disclosed herein. The novel counter-electrodes allow greater control over electrodeposition and electroetching processes for resistive substrates and enable more uniform plating and etching of resistive substrates as compared to known counter-electrodes.
According to one embodiment, a multi-segmented counter-electrode for electrodeposition, electroetching or anodizing of resistive substrates is provided, wherein the multi-segmented counter-electrode comprises: a series of vertically stacked counter-electrode segments comprising a center counter-electrode segment, at least one middle counter-electrode segment disposed beneath said center electrode, and an outer counter-electrode segment disposed beneath said at least one middle electrode.
According to another embodiment, a multi-segmented counter-electrode for electrodeposition, electroetching or anodizing of resistive substrates is provided, wherein the multi-segmented counter-electrode comprises: a center counter-electrode segment; at least one middle counter-electrode segment concentric with said center counter-electrode segment; an outer counter-electrode segment concentric with said center counter-electrode segment and said at least one middle counter-electrode segment; and a height-adjusting means arranged to individually adjust a height of at least one of the following: said center counter-electrode segment, said at least one middle counter-electrode segment and said outer counter-electrode segment.
According to further embodiments, counter-electrodes comprising concave or convex top surfaces are provided.
According to an additional embodiment, a method for electroplating, electrodeposition or anodizing of resistive substrates is provided, wherein said method comprises: providing a multi-segmented counter-electrode comprising a series of vertically stacked counter-electrode segments; and selectively powering at least one of the counter-electrode segments.
According to yet another embodiment, a method for electroplating, electrodeposition or anodizing of resistive substrates is provided, wherein said method comprises: providing a multi-segmented counter-electrode comprising a series of concentric counter-electrode segments; and independently varying a height of at least one of the counter-electrode segments.
Those skilled in the art will appreciate the above stated advantages and other advantages and benefits of various embodiments upon reading the following detailed description of the embodiments with reference to the below-listed drawings.
According to common practice, the various features of the drawings are not necessarily drawn to scale. Dimensions of various features may be expanded or reduced to more clearly illustrate the embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
The center counter-electrode segment 110 has the smallest diameter (or width, in cases in which non-cylindrical counter-electrode segments are used) as compared to the diameters of segments 120 and 130, and is referred to as a “center” segment because its top face 114, and therefore its conductive layer 118, is exposed in the vicinity of the central axis Y of the counter-electrode 100. The middle counter-electrode segment 120 has a diameter larger than the diameter of the initial segment 110, and is referred to as the “middle” segment, because its top face 124, and thus its conductive layer 128, is exposed at a middle radial region of the counter-electrode 100. The outer counter-electrode segment 130 has the largest diameter as compared to the diameters of the segments 110 and 120, and is referred to as the “outer” segment because its top face 134, and therefore its conductive layer 138, is exposed at the outermost radial region of the counter-electrode 100.
In order to provide greater control over an etching or deposition process, one or more of the counter-electrode segments 110, 120 and 130 may be individually powered. In order to individually power the segments 110, 120, 130, each segment 110, 120, 130 may be provided with an individual power supply (not shown). Thus, by selectively powering one or more counter-electrode segments, one can exercise greater control over the current field in the plating/etching circuit in order to achieve a uniform deposition or etching.
Greater control over an electrodeposition or electroetching process can be obtained by providing a multi-segmented counter-electrode having counter-electrode segments with variable interelectrode distances (i.e., variable heights), as shown in the embodiment of
In order to allow the counter-electrode segments 210, 220, 230, 240 to move independently with respect to each other, adjacent counter-electrode segments must not be fixed together. Therefore, if the counter-electrode 200 is constructed such that adjacent anode sections contact each other, the vertical interfaces 202, 204, 206 of adjacent counter-electrode segments should be low-friction interfaces. Beyond polishing, low-friction interfaces may be achieved by applying a low-friction coating to contacting surfaces of adjacent counter-electrode segments, or by constructing the counter-electrode segments 210, 220, 230, 240 from a smooth low-friction material such as PTFE. Alternatively, the counter-electrode 200 should be constructed such that a solution-filled annular gap is provided between adjacent counter-electrode segments in lieu of the low-friction interfaces 202, 204, 206.
One way to compensate for the terminal effect during plating or etching processes, and therefore achieve more uniform plating or etching, is to increase the interelectrode distance (i.e., reduce the height of) of the counter-electrode segments that are closer to the workpiece edge (one or more of segments 220, 230 and 240) and to decrease the interelectrode distance (i.e., increase the height of) of the center counter-electrode segment 210, such that the center electrode 210 is brought vertically closer to the workpiece, while the counter-electrode segments that are closer to the workpiece edge are moved vertically further away from the workpiece.
Additionally, each segment 210, 220, 230, 240 of the counter-electrode 200 may be independently powered. Thus, the optimal conditions for achieving a uniform plating/deposition for a given plating/etching run (e.g., plating a particular type of substrate, at a particular plating rate, out of a particular plating solution, etc.) can then be defined by a combination of current profile and height profile of the segments 210, 220, 230, 240.
The counter-electrode 200 provides a very flexible solution to plating/etching. The use of counter-electrode segments 210, 220, 230, 240 that are independently height-adjustable increases the feasibility of connecting more than one segment to the same power supply, since it is possible to achieve more uniform plating/etching just based on varying the height of each segment 210, 220, 230, 240.
Although the counter-electrode 200 includes cylindrical and annular counter-electrode segments, other embodiments are possible which include counter-electrode segments of different shapes. For example, the center counter-electrode segment may have any given geometric shape, and the middle and outer counter-electrode segments may have similar shapes with hollow center portions.
Although the multi-segmented counter-electrodes discussed in the preceding embodiments are shown having certain numbers of counter-electrode segments, it is possible to include any number of counter-electrode segments in the disclosed counter-electrodes. The number counter-electrode segments used will be determined based on the nature of the application.
The advantages of certain embodiments disclosed herein are illustrated in the following examples:
EXAMPLES In the following Examples 1-3, the results of which are illustrated in
The center, middle and outer counter-electrode segments were all powered at the same current density to form a deposit on the seed layer. The 3-D diagram of
The center counter-electrode segment only was powered. The local sheet resistance of the resulting deposit is mapped in
The center and middle counter-electrode segments only were powered, to the same current density. The local sheet resistance of the resulting deposit is mapped in
In this example, the same counter-electrode configuration and current distribution from the previous examples was used to electroplate two 200-mm wafers having widely different seed layer sheet resistances. In the case depicted in
From the above examples, it is clear that the mere selective powering of different segments makes it possible to radically modify the thickness of the deposit. The uniformity can be further improved by fine-tuning the fractional current sent to each segment, by increasing the number of segments, and by modifying the dimensions of the segments.
The foregoing description illustrates and describes only selected embodiments, but it is to be understood that modifications within the scope of the inventive concept as expressed herein are possible, commensurate with the above teachings, and/or within the skill or knowledge of the relevant art. Accordingly, the description is not intended to limit the invention to the form disclosed herein. Also, it is intended that the appended claims be construed to include alternative embodiments, not explicitly defined in the detailed description.
Claims
1. A multi-segmented counter-electrode for electrodeposition, electroetching or anodizing of resistive substrates, said multi-segmented counter-electrode comprising:
- a series of vertically stacked counter-electrode segments comprising a center counter-electrode segment, at least one middle counter-electrode segment disposed beneath said center electrode, and an outer counter-electrode segment disposed beneath said at least one middle electrode.
2. The multi-segmented counter-electrode of claim 1, wherein said center counter-electrode segment, said at least one middle counter-electrode segment and said outer counter-electrode segment are cylindrical in shape.
3. The multi-segmented counter-electrode of claim 2, wherein said at least one middle counter-electrode segment has a diameter that is larger than a diameter of said center counter-electrode segment and said outer counter-electrode segment has a diameter that is larger than the diameter of said at least one middle counter-electrode segment.
4. The multi-segmented counter-electrode of claim 1, wherein said at least one middle counter-electrode segment has a width that is larger than a width of said center counter-electrode segment and said outer counter-electrode segment has a width that is larger than the width of said at least one middle counter-electrode segment.
5. The multi-segmented counter-electrode of claim 1, wherein said at least one middle counter-electrode segment comprises two or more middle counter-electrode segments.
6. The multi-segmented counter-electrode of claim 1, wherein said center counter-electrode segment, said at least one middle counter-electrode segment, and said outer counter-electrode segment are constructed of a non-conductive material, and wherein an exposed portions of a top surface of each of said center counter-electrode segment, said at least one middle counter-electrode segment, and said outer counter-electrode segment is covered by a conductive layer.
7. A system comprising the multi-segmented counter-electrode of claim 1 and separate power supplies for each of said center counter-electrode segment, said at least one middle counter-electrode segment, and said outer counter-electrode segment.
8. A multi-segmented counter-electrode for electrodeposition, electroetching or anodizing of resistive substrates, said multi-segmented counter-electrode comprising:
- a center counter-electrode segment;
- at least one middle counter-electrode segment concentric with said center counter-electrode segment;
- an outer counter-electrode segment concentric with said center counter-electrode segment and said at least one middle counter-electrode segment; and
- a height-adjusting means arranged to individually adjust a height of at least one of the following: said center counter-electrode segment, said at least one middle counter-electrode segment and said outer counter-electrode segment.
9. The multi-segmented counter-electrode of claim 8, wherein said height-adjusting means comprises at least one shim disposed beneath at least one of the following: said center counter-electrode segment, said at least one middle counter-electrode segment, and said outer counter-electrode segment.
10. The multi-segmented counter-electrode of claim 8, wherein said height-adjusting means comprises at least one remotely-controlled element disposed beneath at least one of the following: said center counter-electrode segment, said at least one middle counter-electrode segment, and said outer counter-electrode segment.
11. The multi-segmented counter-electrode of claim 10, wherein said remotely controlled element comprises a pneumatic support.
12. The multi-segmented counter-electrode of claim 11, wherein the pneumatic support is connected to an air tube positioned along internal edges of an electrochemical cell.
13. The multi-segmented counter-electrode of claim 8, wherein adjacent counter-electrode segments among said center counter-electrode segment, said at least one middle counter-electrode segment, and said outer counter-electrode segment contact each other at low-friction vertical interfaces.
14. The multi-segmented counter-electrode of claim 8, wherein adjacent counter-electrode segments among said center counter-electrode segment, said at least one middle counter-electrode segment, and said outer counter-electrode segment are separated by a gap.
15. The multi-segmented counter-electrode of claim 8, wherein said center counter-electrode segment is cylindrical in shape, and wherein said at least one middle counter-electrode segment and said outer counter-electrode segment are annular in shape.
16. The multi-segmented counter-electrode of claim 15, wherein said at least one middle counter-electrode segment has an outer diameter that is larger than an outer diameter of said center counter-electrode segment and said outer counter-electrode segment has a diameter that is larger than the outer diameter of said at least one middle counter-electrode segment.
17. The multi-segmented counter-electrode of claim 8, wherein said center counter-electrode segment, said at least one middle counter-electrode segment, and said outer counter-electrode segment are constructed of a non-conductive material, and wherein an exposed portion of a top surface of each of said center counter-electrode segment, said at least one middle counter-electrode segment, and said outer counter-electrode segment is covered by a conductive layer.
18. The multi-segmented counter-electrode of claim 8, wherein said at least one middle counter-electrode segment comprises two or more middle counter-electrode segments.
19. A system comprising the multi-segmented counter-electrode of claim 8 and separate power supplies for each of said center counter-electrode segment, said at least one middle counter-electrode segment, and said outer counter-electrode segment.
20. A counter-electrode for electrodeposition, electroetching or anodizing of resistive substrates, wherein said counter-electrode comprises a concave or convex top surface.
21. A method for electroplating, electrodeposition or anodizing of resistive substrates, comprising:
- providing a multi-segmented counter-electrode comprising a series of vertically stacked counter-electrode segments; and
- selectively powering at least one of the counter-electrode segments.
22. The method of claim 21, wherein selectively powering at least one of the counter-electrode segments comprises powering at least two counter-electrode segments at equal current density.
23. The method of claim 21, wherein selectively powering at least one of the counter-electrode segments comprises powering at least two counter-electrode segments at different current densities.
24. A method for electroplating, electrodeposition or anodizing of resistive substrates, comprising:
- providing a multi-segmented counter-electrode comprising a series of concentric counter-electrode segments; and
- independently varying a height of at least one of the counter-electrode segments.
25. The method of claim 24, comprising selectively powering at least one of the counter-electrode segments.
26. The method of claim 25, wherein selectively powering at least one of the counter-electrode segments comprises powering at least two counter-electrode segments at equal current densities.
27. The method of claim 25, wherein selectively powering at least one of the counter-electrode segments comprises powering at least two counter-electrode segments at different current densities.
28. The method of claim 24, wherein the counter-electrode comprises at least one shim for independently varying the height of at least one of the counter-electrode segments.
29. The method of claim 24, wherein the counter-electrode comprises at least one remotely controlled element for independently varying the height of at least one of the selected counter-electrode segments.
30. The method of claim 24, wherein the at least one remotely controlled element comprises a pneumatic support.
Type: Application
Filed: Jun 20, 2005
Publication Date: Dec 21, 2006
Applicant: International Business Machines Corporation (Armonk, NY)
Inventors: Panayotis Andricacos (Croton-On-Hudson, NY), Emanuel Cooper (Scarsdale, NY), John Cotte (New Fairfield, CT), Hariklia Deligianni (Tenafly, NJ), Caliopo Andricacos (Chicago, IL)
Application Number: 11/155,495
International Classification: C25C 7/02 (20060101);