Patent Application
20080014845
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of 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.
To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the figures. It is also contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.
Embodiments described herein relate to a conditioning disk for conditioning, which includes scoring and/or dressing, a polishing surface of a polishing pad used in an electrochemical mechanical polishing (ECMP) process. Specifically, the conditioning disk is suitable for conditioning processing pads having delicate conductive surfaces that are more typically used in ECMP systems. The inventive pad dresser comprises an annular body disposed on a backing plate. The backing plate is adapted to be coupled to a conditioning head assembly that is used to urge the pad dresser against the polishing surface of the polishing pad. The annular body comprises a polycrystalline diamond covering or coating that is adapted to refresh, score, or condition the polishing surface when in contact with the polishing surface. In some embodiments, the polycrystalline diamond covering is machined to include a plurality of substantially identical structures which condition the polishing surface of the polishing pad. The size, pitch, and height of the plurality of structures are controlled with tight tolerances to enhance the cut rate without adversely increasing surface roughness of the polishing surface, and to prevent clogging or accumulation of polishing by-products, such as metal particles and/or portions of the polishing surface that may be spent and/or torn away from the polishing surface.
The conditioning device 115 is disposed proximate each polishing station 120A-120C and is adapted to condition the polishing material 125 disposed on each platen 130. Each conditioning device 115 is adapted to move between a position clear of the polishing material 125 and platen 130 as shown in
The polishing material 125 includes a polishing surface that is at least partially conductive. Examples of polishing material 125 may include a combination of dielectric and conductive materials. In one embodiment, the polishing material 125 may include dielectric or conductive materials having conductive elements disposed therein. The conductive elements may be flakes, particles, and the like that are disposed in a dielectric or conductive material, such as a polymer material. Examples of conductive materials used as conductive elements and/or the conductive material are copper, carbon based materials, gold, platinum, silver, tin, zinc, nickel, cobalt, and combinations thereof, among other conductive materials that are resistant to polishing chemistry. Carbon-based material includes carbon black, graphite, and carbon particles. Examples of conductive carbon-based materials include carbon powder, carbon fibers, carbon nanotubes, carbon nanofoam, carbon aerogels, graphite, and combinations thereof. In one embodiment, a conductive polishing material may include conductive foils, polymers polymer materials with conductive materials disposed therein, conductive meshes, conductive flakes, conductive fibers, or a fabric of interwoven conductive fibers. The conductive materials, fibers, or fabric may be disposed in a polymeric material.
The pad dresser 110 is coupled to the conditioning head assembly 202 and may be selectively pressed against the polishing material 125 while rotating to condition the polishing material 125. The pad dresser 110 includes a backing plate and a conditioning surface. The backing plate and/or the conditioning surface are typically round, disk-shaped, or annular to facilitate rotation of the pad dresser 110 and enhance conditioning of the polishing material 125 and/or control of the conditioning process.
In this embodiment, the polishing material 125 comprises a polishing pad having a first conductive layer 270 and a second conductive layer 272 separated by an insulative layer 274. The first conductive layer 270 functions as an electrode and includes a polishing surface 276 that is at least partially conductive as described above, and is adapted to contact a substrate during a polishing process. A conductive carrier 278 may be disposed between the first conductive layer 270 and the insulative layer 274 to provide additional support for the first conductive layer 270. The conductive carrier 278 may be a mesh, cloth, fabric, and the like as described above, and may be coated with a conductive material. An example of a conductive carrier is a mesh or fabric made of nylon that is coated with a conductive material, such as gold. A terminal (not shown) coupled to a power supply (not shown) may be attached to one or both of the conductive carrier 278 and the first conductive layer 270 to provide a voltage to the first conductive layer 270. The second conductive layer 272 functions as a counterelectrode to the first conductive layer 270 and may include a terminal (not shown) coupled to a different pole of the power supply.
The first conductive layer 270 may be a polymer material that includes conductive elements 280 embedded therein as described above. During polishing, a substrate (not shown) is urged against the polishing material 125, the first conductive layer 270 is electrically coupled to conductive material deposited on the face of the substrate. The first conductive layer 270 and/or the conductive material on the substrate are in electrical communication with the second conductive layer 272 through an electrolyte provided to the surface of the polishing material 125. In one embodiment, the electrolyte flows through openings 282 formed through a portion of the polishing material at least to an upper surface of the second conductive layer 272. As one or both of the platen 130 and substrate are rotated, conductive material is removed from the face of the substrate by electrochemical and mechanical forces.
Before, during, or after the polishing process, the polishing surface 276 may require conditioning of the pad polishing surface in order to maintain predefined processing results. Conditioning may create, reform, and/or clear grooves and/or asperities in the polishing surface 276. In another application, conditioning of the polishing surface 276 refreshes the polishing surface 276. Refreshing may include at least one of exposing new or unused material on the polishing surface 276, removing polishing by-products, removing spent or torn portions of the polishing surface 276, and/or removal or minimization of oxides disposed in or on the polishing surface 276. The conditioning of the polishing surface 276 may be performed prior to polishing with a new polishing pad, during the polishing process to maintain and/or enhance surface roughness and removal rate of the polishing surface 276, or post-processing to prepare the polishing surface 276 for a new substrate to be polished.
In one embodiment, the backing plate 305 comprises a rigid material, such as a ceramic or metal, for example stainless steel, aluminum, among other metals. The first surface 317 of the backing plate 305 is adapted to abut with the face 317 of the conditioning head 250. Openings 319 are formed in the backing plate 305 to facilitate coupling of the backing plate 305 to the conditioning head 250. The openings 319 may be adapted to receive alignment pins or fasteners (not shown) that engage with mating holes 322 and/or 324. In one embodiment, at least one of the mating holes 322 and 324 include female threads. For example, the backing plate 305 may have one or more openings 319 formed in the outer portion 306 to facilitate coupling to the conditioning head 250 via fasteners, such as screws, bolts, pins, or the like. In the embodiment depicted in
The annular member 310 generally comprises an annular body 320 and a conditioning surface 315 formed thereon. In an alternative embodiment (not shown), the annular body 320 may be a solid flat cylindrical member having the conditioning surface 315 disposed thereon. The annular body 320 comprises a carbide material, such as tungsten carbide, that is coupled to the second surface 318 of the backing plate 305. The annular body 320 may be adhered to the backing plate 305 by an adhesive 328, such as an epoxy material or other suitable adhesive material. In one embodiment, the thickness of the annular member 310 is about 2.0 mm to about 3.5 mm, and the thickness of the conditioning surface 315 is greater than or equal to about 0.3 mm. In one application, the ratio of the outside diameter of the annular member 310 to the inside diameter of the annular member 310 is about 1.84:1. In one embodiment, the backing plate 305 includes an annular channel 326 formed therein, and the annular body 320 is configured to be received by the annular channel 326.
In one embodiment, the annular member 310 is sloped or convex relative to the plane of the second surface 318 of the backing plate 305. For example, the annular member 310 may be center-thick and slope or curve radially outward (and upward as shown in
In one embodiment, the annular member 310 includes a dimension 355 that includes a delta from the center portion of the annular member 310 to a perimeter thereof. The dimension 355 may be a linear delta or curved delta of less than or equal to about 50 μm, such as less than or equal to about 40 μm. Additionally, the perimeter of the annular body 320 may be relieved to minimize or avoid damaging the polishing surface of a polishing pad (not shown) through contact during conditioning. As an example, the outer diameter and/or inside diameter of the annular body may be beveled, rounded, chamfered, and the like to relieve edges at the perimeter of the annular body 320. The conditioning surface 315 disposed thereon may follow any relieved portions of the annular body 320 to prevent or minimize damage to the polishing surface of the polishing pad.
The conditioning surface 315 comprises a polycrystalline diamond coating or layer having structures 350 formed therein and extending therefrom. In one embodiment, the conditioning surface 315 is made of polycrystalline diamond coating that is formed by fusing fine diamond powder at high temperatures and pressures to form a monolithic diamond coating. In one embodiment, micron diamond powder having micron sized grains is sintered to form the conditioning surface 315. Temperatures of greater than 1300° C. and pressures of greater than 5 gigapascals are generally used to sinter the coating. In one embodiment, molten cobalt is used to aid the fusing process, which results in trace amounts of conductive cobalt being left in the polycrystalline diamond surface. In this embodiment, the plurality of structures 350 may be formed by wire electromotive discharge (WEMD) machining to produce many different sizes, shapes, and patterns of structures 350.
The backing plate 305 may be any shape, such as circular, annular, or disk-shaped. In one embodiment, the backing plate 305 has a diameter between about 100 mm and about 110 mm, such as about 108 mm. The backing plate 305 is generally stiff or rigid enough to minimize flexing under processing conditions. The rigidity of the backing plate 305 may be obtained by material selection and/or the thickness of the backing plate 305. For example, the backing plate 305 may be made of a rigid material and have a thickness of between about 6 mm and about 7 mm.
In one embodiment, each structure 350 comprises a pyramidal shape having a four sided base 352, although the base may be any polygonal shape having three sides or more than four sides. In this embodiment, the base 352 of each structure 350 has a substantially rectangular shape with a width between about 0.1 mm and about 0.2 mm, such as between about 0.15 and about 0.17 mm, or about 0.16 mm. Shapes of structures 350 other than pyramids may be used, such cubes, three-dimensional rectangles, cones, frustrums, cylinders, or combinations thereof. The structures 350 may have a spacing or pitch, measured between the tips 354, between about 450 microns (μm) and about 550 μm, such as between about 475 μm and about 525 μm. In one application, each base 352 is adjacent other bases 352 such that where one structure 350 ends, another structure 350 begins.
In one embodiment, the structures 350 are configured as cutting edges adapted to form grooves or channels in the polishing surface 276 (
The backing plate 305 may be any shape, such as circular, annular, or disk-shaped. In one embodiment, the backing plate 305 has a diameter between about 100 mm and about 110 mm, such as about 108 mm. The backing plate 305 is generally stiff or rigid enough to minimize flexing under processing conditions. The rigidity of the backing plate 305 may be obtained by material selection and/or the thickness of the backing plate 305. For example, the backing plate 305 may be made of a rigid material and have a thickness of between about 6 mm and about 7 mm.
In this embodiment, the structures 350 are of a substantially equal height “H” above the bottom 400 and are distributed in a substantially equidistant pattern across the conditioning surface 315. In this embodiment, each of the structures are of a substantially equal height, such as within about ±30 μm. For example, the height H of each structure 350 may be about 170 μm with a deviation of ±30 μm. In one embodiment, the deviation in height between any two adjacent tips 354 is less than or equal to about 30 μm, such as less than or equal to about 25 μm.
While not shown, at least a portion of the plurality of structures 350 may be flattened at the tip 354. Further, a portion of the flattened tips 354 may be grooved, rounded, or include a sharp transition from the flat tip to the sidewall of the structure 350. Additionally, spaces between the structures 350 may be formed in the conditioning surface 315 by spacing the bases 352 of the structures 350 leaving a flat and/or groove therebetween.
A polycrystalline diamond surface is very durable to resist crystal breakage and/or crystal dislodgment during conditioning. Polycrystalline diamond layers or coatings comprising the conditioning surface 315 as described herein can be machined to produce any configuration and combination of structure and/or tip size, shape, and spacing. The heights of the structures and/or tips may be controlled to form uniform or non-uniform sizes. Structures may be organized with uniform spacing according to a geometric pattern, or spacing may be controllably non-uniform. The uniformity and control of structure shape and height may be selected to provide more structures contacting the polishing surface during conditioning. Additionally, individual structures 350 are subjected to less mechanical stress, which extends the life of the pad dresser 110. The frequency, pitch, height, and shape of the structures 350 are also selected to minimize or eliminate accumulation of by-products, for example conductive elements and other objects from the polishing surface 125. This results in a highly repeatable scoring or conditioning pattern on the polishing pad. Thus, conditioning of the polishing pad is more uniform, and load distribution is spread more evenly among the structures 350, which also extends the service life of the pad dresser 110.
Likewise, the conditioning of the delicate polishing surface 125 of the polishing pad is less aggressive and creates substantially uniform asperities in the polishing surface 125. This results in longer pad lifetime. Experimental results have shown that using a polycrystalline diamond coating as the conditioning surface 315 has doubled the usable life of the polishing material of the polishing pad. The spacing and/or size of the structures produce uniform cuts and grooving of the polishing material and has been shown to be substantially uniform, thus producing substantially uniform asperities in the polishing material. This has resulted in an increase in polishing pad life from about 1500 wafers to about 3000 wafers, which results in lower cost of ownership and higher throughput as pad replacement is minimized. Further, the uniform conditioning of the polishing surface provides an acceptable surface roughness of the polishing surface in faster conditioning periods, which results in enhanced throughput of the system.
The use of a polycrystalline diamond coating as the conditioning surface 315 also enables the pad dresser 110 to be resurfaced. The polycrystalline diamond coating may be re-worked to reproduce the original geometry of the structures 350 many times before the polycrystalline diamond coating is worn away. This results in lower cost of ownership as used conditioning elements may be refurbished instead of replaced.
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.
This application claims benefit of U.S. Provisional Patent Application Ser. No. 60/807,066 (Attorney Docket No. 11271L), filed Jul. 11, 2006, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60807066 | Jul 2006 | US |
