US 7378004 B2
An apparatus capable of assisting in controlling an electrolyte flow and an electric field distribution used for processing a substrate is provided. It includes a rigid member having a top surface of a predetermined shape and a bottom surface. The rigid member contains a plurality of channels, each forming a passage from the top surface to the bottom surface, and each allowing the electrolyte and electric field flow therethrough. A pad is attached to the rigid member via a fastener. The pad also allows for electrolyte and electric field flow therethrough to the substrate.
1. A pad structure for use in an apparatus for depositing material on, or removing material from, a substrate, the pad structure comprising:
a substantially circular pad material having a top surface, a bottom surface and a defined thickness;
means for communicating electrolyte and an electric field, magnetic field or electromagnetic field through the pad material to the substrate, wherein the communicating means is an array of holes extending through the pad material and arranged in a radial direction from a center of the pad material; and
an adhesive system on the bottom surface, wherein the adhesive system is configured to block at least one of the holes to control distribution of at least one of the electric field and the electromagnetic field through the pad material.
2. The pad structure according to
3. The pad structure according to
4. The pad structure according to
5. The pad structure according to
6. The pad structure according to
7. The pad structure according to
8. The pad structure according to
9. The pad structure according to
a top pad material and a subpad material; and
an adhesive securing the top pad material to the subpad material.
10. The pad structure according to
11. The pad structure according to
12. A pad structure for use in an apparatus for depositing material on, or removing material from, a substrate, the pad structure comprising:
a pad material having a top surface, a bottom surface and a defined thickness;
at least one opening extending between the top surface and the bottom surface, the at least one opening having an inlet at the bottom surface and an outlet at the top surface, wherein the at least one opening is adapted to communicate electrolyte and an electric field, magnetic field or electromagnetic field through the pad material to the substrate, wherein the substrate is exposed to the outlet and wherein the at least one opening is a slit extending across a substantial portion of the diameter of the pad material, said slit also extending through the pad material; and
an adhesive system on the bottom surface, wherein the adhesive system is configured to block at least a portion of the inlet and configured to control distribution of at least one of the electric field and the electromagnetic field through the pad material.
13. The pad structure according to
14. The pad structure according to
15. The pad structure according to
16. The pad structure according to
17. The pad structure according to
18. A pad for polishing a surface of a substrate comprising:
a plurality of channels formed therein, wherein the plurality of channels extend between a first surface and an opposite second surface of the pad, wherein at least one of the plurality of channels has an outlet exposed, wherein the surface of the substrate is exposed to the outlet, and wherein the plurality of channels are cylindrical and the channels include a diameter from 0.5 mm to 5 mm; and
an adhesive system on one of the first and second surfaces, wherein the adhesive system is configured to block at least one of the channels to control distribution of at least one of an electric field and electromagnetic field through the pad.
19. The pad according to
20. The pad according to
21. The pad according to
22. The pad according to
23. The pad according to
24. The pad according to
25. A pad for polishing a surface of a substrate comprising:
a plurality of channels formed therein;
a polishing surface having a plurality of grooves disposed thereon, wherein a portion of the plurality of grooves intersect the plurality of channels, wherein the plurality of channels extend between the polishing surface and a bottom surface opposite the polishing surface; and
an adhesive system on the bottom surface, wherein the adhesive system is non-porous under at least one of the channels and to configured to control distribution of at least one of an electric field and electromagnetic field through the pad.
26. The pad according to
27. A pad for polishing a surface of a substrate comprising:
a plurality of channels formed therein;
a polishing surface having a plurality of grooves disposed thereon, wherein the plurality of grooves extend transversely with respect to one another, wherein the plurality of channels extend between the polishing surface and a bottom surface opposite the polishing surface; and
an adhesive system on the bottom surface, wherein the adhesive system is non-porous under at least one of the channels and to configured to control distribution of at least one of an electric field and electromagnetic field through the pad.
28. The pad according to
29. The pad according to
30. A pad for polishing a surface of a substrate comprising:
a plurality of channels formed therein, wherein the plurality of channels extend between a polishing surface and an opposite undersurface of the pad, wherein at least one of the plurality of channels has an outlet exposed, wherein the surface of the substrate is exposed to the outlet;
an adhesive system on one of the first and second surfaces, wherein the adhesive system is configured to block at least one of the channels to control distribution of at least one of an electric field and electromagnetic field through the pad; and
a support structure attached to the undersurface of the pad by the adhesive system, wherein the support structure includes a plurality of channels disposed therein and adapted to flow material therethrough and at least a portion of the plurality of channels in the pad are aligned with the plurality of channels in the support structure adapted for the flow of the material through the support structure and the pad.
31. The pad structure according to
32. The pad structure according to
33. The pad structure according to
34. The pad structure according to
35. The pad structure according to
36. The pad structure according to
This application is a divisional of application Ser. No. 09/511,278, filed Feb. 23, 2000 now U.S. Pat. No. 6,413,388.
1. Field of the Invention
The present invention relates to a highly versatile apparatus for depositing, removing, modifying, or polishing a material on a workpiece, such as a substrate. More particularly, the present invention is directed to various pad designs and structures for depositing, removing, modifying and/or polishing a material on a suitable substrate.
2. Description of Related Art
There are numerous processing steps in the fabrication of high performance integrated circuits (ICs), packages, magnetic film heads, thin film display units, and the like. One important step is to deposit, remove, or planarize a conductive or insulative material on a workpiece, such as a semiconductor substrate. Deposition of conductive materials such as copper, gold, nickel, rhodium, and their various alloys may be performed, for example, by electrodeposition.
In inlaid metal technology, a workpiece, such as a substrate 10 shown in
The conductive material may be, for example, Cu deposited by way of a chamber-type device 100 (generally shown in
A holder 108 holds the workpiece, such as the substrate 10. For a detailed description of the holder, reference can be made to the assignee's co-pending application Ser. No. 09/472,523, entitled “Work Piece Carrier Head For Plating and Polishing” filed Dec. 27, 1999, the specification of which is incorporated by reference herein as non-essential matter.
For the deposition process, the substrate 10 is typically immersed in the electrolyte 106 with the aid of the holder 108, which also provides a way of electrically contacting the substrate 10. By applying a potential difference between the anode 104 and the substrate 10 (i.e., the cathode), materials may be deposited on or removed from the substrate. For example, when the anode is more positive than the substrate, copper may be deposited on the substrate 10. If the anode is more negative than the substrate, however, copper may be etched or removed from the substrate. To aid electrolyte agitation and enhance mass transfer, the substrate holder 108 may include a rotatable shaft 112 such that the substrate holder 108 and the substrate 10 can be rotated. The substrate 10 is typically spaced apart from the anode 104 at a distance of at least about 10 mm; this distance may, however, be as great as about 300 mm. The surface of the substrate 10 may contain topographic features, such as the vias 12 and channels 14 illustrated in
After depositing the conductive material 22 on the top surface of the substrate 10, the substrate 10 is typically transferred to a chemical mechanical polishing (CMP) apparatus in order to polish, planarize, or both polish and planarize the same surface.
The conventional method for depositing a conductive material produces large variations in material overburden across the substrate as shown in
There is therefore a need for an apparatus that can reduce the time needed during the planarization phase of the fabrication process, and that can simplify the planarization phase itself. In other words, a more efficient and effective method and apparatus for depositing a conductive material on a substrate is needed. Various pad designs and structures are disclosed herein that can be used for depositing conductive material with a very uniform material overburden on a surface of a substrate.
It is an object of the present invention to provide a method and apparatus for performing any of depositing, removing, polishing, and/or modifying operations on conductive material, which is to be applied to or has been applied on a substrate.
It is another object of the present invention to provide a method and apparatus for depositing a conductive material with minimum material overburden.
It is still another object of the invention to provide a method and apparatus for depositing a conductive material with a uniform material overburden across the surface of a substrate.
It is a further object of the invention to provide a method and apparatus for depositing material on a substrate in an efficient and cost-effective manner.
It is still a further object of this invention to provide various pad designs and structures for depositing a conductive material on a substrate.
It is yet another object of this invention to provide a method for mounting a pad having channels, holes or grooves for depositing a conductive material on a substrate.
It is a further object of this invention to provide a method and apparatus to mount a pad to be used for depositing a material on a surface.
It is yet another object of the invention to provide a method and pad to control the uniformity of a deposited material on a substrate.
These and other objects of the present invention are obtained by providing a method and apparatus for simultaneously plating and polishing a conductive material on a substrate. The substrate (or cathode in the deposition process) is disposed in close proximity to a rotating member having a pad material attached thereto. The pad is interposed between the substrate (cathode) and the anode. Upon applying an electrical current or potential between the substrate and the anode in the presence of a suitable electrolyte, the conductive material may be removed or deposited on the cathode.
In a preferred embodiment, the conductive material may be selectively deposited in the cavities of topographical features on the substrate surface, while the pad material minimizes or prevents material depositions in regions above the cavities.
The nature, design, fabrication and mounting of the pad material used in this invention advantageously allow for the modification of material removal from, or the deposition of a high quality conductive material on, a substrate surface.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
The present invention will now be described in detail. Various refinements in and modifications of the various embodiments are possible based on the principles and teachings herein.
The present invention can be used to deposit and/or remove materials on any substrate, such as a wafer, flat panel, magnetic film head, integrated circuit, package, semiconductor device or chip, or any other device or workpiece of interest. For purposes of this description, the terms “substrate” and “workpiece” can be used interchangeably. Further, the specific parameters referred to herein, such as materials, dimensions, thicknesses, and the like, are intended to be explanatory rather than limiting.
The pad support member 320 is secured to the anode holder 322 b with screws in a manner such that they are both electrically isolated from one another. An electrolyte or solution chamber 322 e is therefore formed between anode bottom portion 322 a and the pad support member 320. The gap 322 f separates the anode bottom portion 322 a from the pad support member 320. Small channels 324 are formed in the pad support member 320 for fluid solutions to communicate between the chamber 322 e to the substrate 10. A polishing pad material 330 is attached above the pad support member 320. The polish pad material 330 may contain two or more distinct types of channels. Channels 330 a are provided for the fluids to communicate between the chamber 322 e and the substrate 10, and channels 330 b for mostly an electric field to communicate between the anode bottom portion 322 a, via the electrolyte chamber 322 e and pad support member 320, and the substrate 10. The combination of channels (sometimes referred to as holes) are used to manipulate the electrolyte fluid flow and electric field distribution over the substrate 10 to control the nature of the material deposited on the substrate, in particular the uniformity of the deposit on the substrate.
The pad material 330 is secured to the pad support member 320 with the aid of a fastener, such as an adhesive material 332. The entire anode bottom portion-pad support member-pad assembly 322 is housed in another chamber 334, in which electrolytes emanating from interface 334 b between the substrate 10 and a surface of the pad material 330 accumulate. This accumulated electrolyte solution may be pumped into a reservoir system for reclaimation and reuse, or may just simply be discarded.
It is further noted that electrical contact with the anode bottom portion 322 a may occur directly or via the anode housing 322 b, while another electrical contact of opposite polarity is made to the substrate 10. Thus, electrical contact need not be made to the pad support member 320.
By way of example, the anode housing 322 b may be formed of polymeric material such as PVDP, polypropylene, PTFE, and/or other materials that are essentially inert to the electrolyte fluids used in the reaction. However, it is most preferred that the anode housing 322 b be made of titanium, stainless steel, graphite, and the like. The anode housing may also be coated with a very thin layer of platinum or palladium. The anode material itself may be an inert type of anode such as graphite, platinized metals, such as Pt/Ti and the like. In some inert anode applications, for simplification, the inner wall of the anode housing 322 b may serve as the anode.
In other applications, a soluble anode 322 a may be housed in the anode housing 322 b. The soluble anode 322 a may be formed by materials such as Cu, phosphorized Cu, Ni, gold, Pt, Ag, Cd, Rh and/or various other alloy electrode materials depending upon the material to be plated. The insulating sealing spacer 322 c may be made of a polymeric material or a combination of polymeric/metallic and/or polymeric/ceramic materials. It is only essential that the electrolyte or fluids used in the reaction do not degrade the spacer 322 c, and/or that the spacer 322 c does not adversely affect the designed qualities of the metal deposited on the substrate 10. Additionally, the method of securing the pad support member 320 via the insulating spacer 322 c must not electrically short the anode 322 a to the pad support member 320.
The pad support member 320 is preferably fabricated from a stiff material with a very specific modulus, such as carbon titanium and the like. Stainless steel may also be used. The pad support member material must not interact in an adverse manner with the deposition fluids so as to affect the material deposited on the substrate. The thickness of the pad support member 320 is such that the member behaves as if it has an infinite stiffness relative to itself (weight) and with respect to the applied polishing load. Additionally, the pad support member 320 may be coated with a very thin layer of platinum or palladium, e.g. about up to 500 Å, to enhance the adhesion of the pad material 330 and also to enhance the electric field dispersion.
The anode housing 322 b of
Referring back to the channels or holes formed in the pad material 330, more than one type of channel/hole with respect to the pad support member 320 or the anode 322 a may be provided. For example, a first family of channels 330 a (or holes, cavities, etc.) can be designed and positioned for fluid and electric field transfer from the electrolyte chamber 322 e to the substrate. Hence, the channels 330 a may be disposed directly on, or adjacent to, channels 324 b formed in the pad support member 320 as shown in
Combination of these families of channels 330 a, 330 b and placement of adhesive sheets 332 are used to control electrolyte and electric field distribution on the substrate 10, and thus control the nature of the material deposited. More particularly, the uniformity of the deposited material can be controlled during plating or plating/polishing operations.
Referring back to the channels 324 arranged in the pad support member 320 and the channels 330 a and 330 b in the pad material 330, these channels may have any shape, such as square, rectangular, etc., however, it is preferred that they be cylindrical in shape. The diameter of the channels may range from about 0.01 to 8 mm, preferably between about 0.03 to 6 mm.
The number of channels in the pad support member 320 may range between about 1 to at least 1000, but preferably between about 10 to 800, depending on the dimensions of the pad support member. These channels may be distributed across the lateral dimensions of the pad support member in any profile that enhances fluid and electric field transfer through the channels. For instance, the channels may be spaced apart by about 0.5 to 50 mm, but preferably between about 1 to 20 mm. Also, the channels need not all be uniform, but may have varying dimensions and diameters.
The channels 330 a and 330 b in the pad material 330 may be similar to those on the pad support member 320. However, channels 330 b are positioned in the pad material 330 so as to land on the pad support member away from channels 324, or at least separated from channels 324 via an insulating or adhesive sheet material 332 x (see
Another embodiment of the invention is illustrated in
The entire chamber housing 404, 407 may be made of a polymeric material such as PVDF, or titanium, but preferably from stainless steel coated with a polymeric film such as PVDF, Teflon or other inert materials that do not adversely affect the performance of the electrolyte or deposited material.
The lower chamber is separated from the upper chamber by an electrolyte filled space or gap 419 (when the tool is operational). The electrolyte gap 419 may vary in size from about 0.5 to 30 mm, but preferably between about 1 to 20 mm. This electrolyte gap 419 may serve as a mixing zone for electrolytes before entering the pad support member 420. This is important in the deposition of laminate films, where metals of different composition are deposited. Thus, for example, one type of electrolyte may be injected via electrolyte inlet 408, while a second electrolyte may be injected intermittently or at a different flow rate into the electrolyte gap 419 from the electrolyte inlet 410. For example, one electrolyte may be injected at a flow rate of about 0.2 to 8 L/min through the electrolyte inlet 408, while a second fluid may be injected intermittently or continuously through electrolyte inlet 410 at a rate ranging from about 2 cc to 20000 cc/min. A portion of the electrolyte mixing may occur within the electrolyte gap 419. The balance of the mixing may occur within the pad support member 420, or within the pad material itself and in the area between the pad material 430 and the substrate 10.
Separating the lower chamber from the upper chamber is the pad support member 420 (shown as part of the lower chamber in
Also, the pad support member 420 should be sufficiently stiff to minimize its deformation or deflection during material deposition and planarization pressures. In addition, the mount for the pad support member should be designed to minimize deformation or deflection of the pad support member 420. Thus, stiffeners (not shown) may be used as appropriate, on the lower surface of the pad support member 420 (surface facing the anode 406). It should be noted that the substrate holder 440 of
The pad 430 is attached to the top surface of the pad support member 420 which faces the substrate 10. The pad material preferably may contain fixed abrasives. The pad 430 has channels 432 of various shapes and forms. Their distribution on the pad 430 also varies depending on the functions to be carried out. In the present invention, the channels 432 in the pad 430 are designed to influence several important process parameters. These channels 432 determine the distribution of the electrolyte fluid or fluids over the surface of substrate 10. The channels 432 also shape the electric field between the anode 406 and the substrate 10. Proper choice of the pad material and the distribution of channel openings 432 on the pad 430, as well as the channels 424 in the pad support member 420 (or the top anode portion 320 of
The pad 430 may be attached to the pad support member 420 of
A third embodiment of the invention illustrated in
where E2 is the allowed controlled leakage volume to help purge bubbles and anode fines, and the balance E4 is the portion filtered through filter 454 and migrated to the substrate surface via the pad support member channels and pad channels.
In a preferred embodiment, the amount of solution E2 allowed to leak ranges between about 0.1 to 20%, but preferably between about 1 to 10% of the total electrolyte flow E1. Also, it is preferred that the volume E4 of the electrolyte discharged into the anode chamber to minimize concentration polarization ranges between about 10 to 40%, but preferably between about 15 to 30% of the volume flow. Thus, the orifices in the shaft 450 discharging E1 into the anode chamber 452 may be chosen accordingly.
The electrolyte E3 emanating from the substrate and the controlled leakage solution E2 may drain through a drain opening 462 at the bottom of the anode chamber 405. These solutions are typically drained to a reservoir for process filtering, and then recycled back to the deposition chamber. Also in
Referring again to
The anode and cathode may be energized after a brief moment of wetting the substrate. The current density to the cathode may range between about 1 to 50 mA/cm2, but preferably between about 5 to 45 mA/cm2.
For example, the substrate may be plated at a current density of about 10 to 25 mA/cm2 for 20 to 70% of the deposition time at a pressure of about 0 to 0.5 psi, and at a higher pressure for the 30 to 80% balance of the deposition time. The pressure on the substrate may increase from 0 to 0.5 psi mentioned above to 0.5 to 3 psi. The electrolyte flow may also be varied within the intervals. Also during the deposition, the carrier head may make continuous or intermittent contact with the stationary pad or rotating pad. The substrate and the anode may rotate between about 2 to 250 rpm, but preferably between about 5 to 200 rpm. Also, lateral movement of the substrate relative to the pad may occur during the deposition process. The speed of the lateral motion may range between about 0.5 to 25 mm/second.
The lateral motion is programmed such that the substrate, while rotating, comes to rest momentarily at various points, or during any stage of its motion. In addition, the rotation of the substrate may be varied in such a manner that, for instance, the substrate is rotated at only about 60 to 85% of normal when the substrate is at one end of a smaller anode/pad than when the centers of the substrate and anode coincide.
Also, the pressure on the substrate is varied depending on the later position of the substrate relative to the pad. Thus, for a given pad design, the combination of various lateral motions, substrate rotation, substrate pressure and electrolyte flow rate may be used to control the uniformity of the deposited material. The deposited material may be either uniform or thinner at the edge or center of the substrate. Using the above process and an appropriate electrolyte, a superplanar metal deposit may be readily obtained when copper or any other metal is deposited over structures of the type shown in
The apparatus of
The invention therefore describes an apparatus allowing for the deposition/removal of material on a substrate or workpiece surface while the surface is in static or dynamic contact with another surface. The other surface need not be the anode. The other surface may be abrasive or non-abrasive in nature. It is essential, however, that the material of the other surface transmit fluid or electrolytes between an anode and a workpiece, as well as allow magnetic, electric or electromagnetic fields to communicate between the anode and the workpiece. In some portions, the pad contact material allows only the electric, magnetic or electromagnetic fields to communicate with the workpiece.
Besides the choice of the pad material, the design and placement of the adhesive material 332 or 332 x (in
In other embodiments, the adhesive material may be a conducting porous material. Also, a conducting adhesive material may be combined with a non-conducting adhesive to attach a pad to the surface of interest. The adhesive material may also be porous or transparent to electric fields, magnetic fields, and even the electrolyte.
In yet other embodiments, the pad material and the adhesive material may selectively diffuse certain ions, e.g. cations while preventing the diffusion of other ions. The criteria for selectivity may be by charge type, charge size, ion size, ratio of ion charge to ion size, and the like.
In yet other embodiments, the pad 330 can be-attached/bonded to the support member 320 using any of the following alternative methods described herein. It is noted that methods other than those described herein can be implemented without departing from the principle teachings provided herein.
In the embodiment of
In the embodiment of
Similar PSA adhesive films are used to attach the pad to either the anode portion or the pad support member. Besides strips, a continuous perforated adhesive material sheet or ply 562 may be used as shown in
As illustrated in
This presents a very practical method to assemble and secure the pad to an anode surface. The edges of the anode are fully sealed to prevent any undesirable fluid leakage. Thus, all the electrolyte emanates from the top of the pad in a controlled manner.
The channels in the subpad need not align directly with those in the pad material above it. Often, it is advantageous to slightly displace the channels in both pads relative to each other, such that the solution does not spray out of the pad but, rather, oozes or migrates out of the pad.
In another embodiment shown in
The choice of the subpad material should allow the electric field to migrate freely through it with minimum resistance. In this way, the electric field distribution is determined by the channels/holes in the pad only. Also, the subpad material and the pad material may be laminated to form more than two layers to obtain optimum material deposition and removal characteristics.
The entire pad structure or pad assembly may be shaped, such as by varying in thickness from its center to the edge. Thus, the pad assembly may be about 3-25% thicker in regions closer to the center than regions closer to the edge. These lateral variations in pad thickness may be necessary to overcome any substantial difference between material net deposition rates across the surface of the pad.
Examples of shaped pads are shown in
Adhesives other than those illustrated herein can be used to attach/bond the pad to the top anode portion (pad support member). These other adhesives may also be shaped in various configurations and in combinations of various shapes described herein so long as they are sufficient to provide a strong bond between the pad and the top anode portion (pad support member), while not degrading the deposited material on the substrate.
As mentioned above, the shape, type, and placement of the adhesives on the pad is important in order to control the uniformity of the deposited material on the substrate. In certain embodiments, a combination of conductive and non-conductive adhesives may be used to obtain a desired level of uniformity. Further, depending on the type, shape, and placement of the adhesives in relation to the pad and the top anode portion or pad support member, the electrolyte solution and electric field distribution across the substrate can also be controlled. For example, when discontinuous sections of adhesives are used, portions of the electrolyte solution may emanate from regions between the adhesives to the pad. Then, the adhesive sheets are used as a fluid or electric field shield or deflector.
Each of the pads described herein may include abrasive or non-abrasive materials. The pad thicknesses may range from about 0.2 to 20 mm, but preferably between about 0.4 to 10 mm. It is also desirable that the pads 330 be made of a material such as polyurethane, kevlar, glass fibers, ceramic fibers, polycarbonate, polyimide, elastomerized epoxy and PVDF, polysulfone or other suitable materials or material combinations.
One of the most important attributes of the pad material is that it does not degrade, contaminate or adversely affect the performance of the electrolyte solution. The pad material may be reinforced with hard abrasive particles. The abrasive particles may be titanium nitride, silicon carbide, cubic boron nitride, alumina, zirconia, diamond, ceria, hard ceramic powders, or hard metallic powders. Again, regardless of the type of abrasive particles used, the abrasive particles should not adversely affect the performance of the electrolyte solution, be dissolved by the electrolyte solution, or degrade the electrical and mechanical properties of the deposited metal layer.
The size of the abrasive particles should be less than approximately 5000 nm, preferably between about 3 to 1000 nm, and most preferably between about 4 to 50 nm. The particle loading or volume fraction in the pad may range from about 5 to 75%, but most preferably range from about 5 to 60% for optimum performance.
The abrasive content of the pad material may be varied radially from the center of the pad to the edge of the pad. For example, particle loading may be about 30-40% in the center and in regions around the center of the pad, and may be gradually reduced to about 5 to 15% at the periphery of the pad material. This gradation in particle distribution within the pad promotes uniform material removal across the pad, such that material removal by the pad is almost independent of the location of the pad. By way of example, for a nominal pad rotating at 100 rpm, the removal rate is expected to be lowest at the center of the rotating polishing pad, while it may be highest close to the periphery of the pad where the pad velocity with respect to the substrate is highest. Similarly, high abrasive loading in the pad material is expected to produced higher material removal rate. Thus, the abrasive loading in a pad may vary so as to effect equivalent removal rates radially across the pad material despite the velocity differences.
In the embodiment of
In yet other embodiments, the plating and polishing pad may include both through channels and grooves. For example,
In alternative embodiments, radial V-shaped grooves may be formed on the top surface of the pad. For example,
In other instances, the grooves may be wedge-shaped with lips to enhance fluid shear and for continuous injection of the electrolyte solution toward the surface of the substrate.
In other embodiments of the present invention, narrow channels and grooves/slits may be used to enhance electrolyte solution flow to the substrate. Examples of various constructions are illustrated in
A third embodiment of the apparatus according to the invention is shown in
As discussed earlier, the apparatus using a shaped pad can perform electro-etching or workpiece surface modification. In this case, channels/holes/openings/slits or the like may be placed on the pad in substantially linear and non-linear fashion as shown in
Other embodiments preferably use a slit fabricated into a pad such as by punching or cutting, as illustrated in
During electro-etching applications, the substrate is at a more positive potential than the anode. It is essential that the electrolyte and the electric field communicate to the substrate through the channels/holes/openings/slits, etc. in the pad material. During the etching removal process, either the anode carrying the pad or the substrate may be stationary, while the other component, disposed in close proximity, may rotate. The rotation of the substrate depends on the current density applied thereto. Thus, the material of interest may be completely removed in ½ to one full rotation of the substrate. At lower current densities, several rotations of the substrate around the anode may be needed. Also, only portions of the material on the substrate may be removed. In some applications the substrate may come into contact with the pad during the process operation. The combination of the electrolyte and mechanical work of the pad on the substrate may be used to modify the surface of the substrate.
Returning to the material removal or deposition process, the linear or non-linear openings in the non-porous pad allow electric field distribution only through the openings. As the substrate or the pad is slowly rotated, the openings sweep over the substrate surface to be processed. The regions or portions of the substrate directly across from the openings in the pad are therefore plated in the case of deposition, etched in the case of substrate electro-removal (etch or polish), or just oxidized and then dissolved in the electrolyte with or without the mechanical actions of the pad. The openings can have various shapes. However, for uniform material removal or deposition/surface modifications, it is important that the pad and/or the substrate be rotated, such that all portions of the substrate surface are exposed to the electric field for some period of time.
In certain preferred embodiments of the invention, the channel openings (orifices or perforations) in the pad support member 320 (anode portion) and the orifices in the pad material 330 arranged directly above can be of different dimensions. For example,
The surface of the pad support member 320 (anode portion) arranged between the pad support member 320 and the pad material 330 as shown in
In a preferred embodiment, portions of the pad material in contact with the substrate act as insulators, however, in other embodiments ferroelectric or, magnetic materials may be incorporated or laminated within the pad material. The incorporation of a magnetic material within the pad material may be used to filter or shield magnetic field communications through the material during the deposition of a magnetic film on the workpiece.
Besides using circular or cylindrical channels or orifices in the various components, other geometries or combinations of geometries may be used. It is found particularly helpful to use slits and circular or cylindrical openings in the pad material to control local uniformity.
In certain material removal applications, it is often preferred that the material removal process proceed from at or near the center of the workpiece and decrease outwardly towards the periphery. In this case, it is especially advantageous that the larger sized channels in the pad material be arranged at or close to the center of the pad material as shown in
In yet another embodiment, the diameter or size of the pad material or the pad support member (or even the anode) may be smaller than the size of the substrate. For example, the diameter of the pad may be about 40% to 70% of the substrate. During material deposition, in the case when the anode and pad is preferentially arranged to one side of the chamber relative to the substrate, excessive material deposits may be observed on the portion of the substrate that continuously overlaps with the anode or pad material. This excess local deposit is a major source of deposit non-uniformity. This poor deposit uniformity is drastically reduced by shaping the pad material in such a manner that fewer and smaller holes or perforations are fabricated around the center of the pad, especially in the region of continuous overlap between the pad and the substrate. While large perforations may be fabricated away from the region of overlap and towards the periphery of the pad as shown in
The above-described channel or perforation distribution selectively enhances more electrolyte and electric field communication towards the larger openings in the pad, thus increasing metal deposition to this region.
In the previous descriptions, numerous specific details are set forth, such as specific materials, structures, chemicals, processes, etc., in order to provide a thorough understanding of the present invention. However, as one having ordinary skill in the art recognizes, the present invention can be practiced without resorting to the details or specific embodiments set forth.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.