POLISHING OF POLYCRYSTALLINE MATERIALS

Abstract

The invention provides methodology for final finishing of hard surfaces such as diamond surfaces. In this method, a smooth pad having a surface roughness of about 0.2 nm to about 100 nm, having, for example a thickness ranging from about 0.02 mm to about 5 mm, and a Shore D hardness of 30 or higher, is utilized in conjunction with known polishing slurries to provide diamond surfaces having superior smooth finishes.

Claims

1. A method for polishing a diamond surface, the method comprising: a. contacting the surface with a slurry composition comprising abrasive particles effective for abrading a diamond surface; b. moving the composition relative to the surface using a chemical mechanical polishing apparatus having a rotating polishing pad, wherein the pad has a surface roughness of about 0.2 to about 100 nm and a Shore D hardness of at least about 30, and c. abrading the surface to remove a portion of the surface, thereby providing a polished diamond surface.

2. The method of claim 1, wherein the diamond surface comprises a single diamond crystal.

3. The method of claim 1, wherein the diamond surface comprises polycrystalline diamond.

4. The method of claim 1, wherein the polishing pad is comprised of a polymeric material.

5. The method of claim 4, wherein the polymeric material is chosen from poly(vinyl chloride), high density polyethylene, and cross-linked polyethylene.

6. The method of claim 1, wherein the slurry composition comprises diamond abrasives.

7. A method for polishing a polycrystalline alumina surface, the method comprising: a. contacting the surface with a slurry composition comprising abrasive particles effective for abrading a polycrystalline alumina surface; b. moving the composition relative to the surface using a chemical mechanical polishing apparatus having a rotating polishing pad, wherein the pad has a surface roughness of about 0.2 to about 100 nm and a Shore D hardness of at least about 30, and c. abrading the surface to remove a portion of the surface, thereby providing a polished polycrystalline alumina surface.

8. The method of claim 7, wherein the polishing pad is comprised of a polymeric material.

9. The method of claim 8, wherein the polymeric material is chosen from poly(vinyl chloride), high density polyethylene, and cross-linked polyethylene.

10. The method of claim 7, wherein the slurry composition comprises diamond abrasives.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 (Comparative) is an optical profilometer 3D view of a polished diamond substrate using different sized grains for a polycrystalline diamond substrate. The initial roughness varies from 10-50 nm. Conventional pads were utilized to achieve up to 3-5 nm of roughness with high within-wafer nonuniformity

[0010] FIG. 2 is an optical profilometer 3D view of a polished polycrystalline diamond (PCD) substrate utilizing ultra-smooth PVC pads. In this Example, a roughness of about 0.3-1 nm can be achieved.

[0011] FIG. 3 is a depiction of the utilization of an ultra-smooth pad, with and without a standard polymeric pad backing.

DETAILED DESCRIPTION

[0012] As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

[0013] The term “about” generally refers to a range of numbers that is considered equivalent to the recited value (e.g., having the same function or result). In many instances, the term “about” may include numbers that are rounded to the nearest significant figure.

[0014] Numerical ranges expressed using endpoints include all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4 and 5).

[0015] In a first aspect, the invention provides a method for polishing a diamond surface, the method comprising: [0016] a. contacting the surface with a slurry composition comprising abrasive particles effective for abrading a diamond surface; [0017] b. moving the composition relative to the surface using a chemical mechanical polishing apparatus having a rotating polishing pad, wherein the pad has a surface roughness of about 0.2 to about 100 nm and a Shore D hardness of at least about 30, and [0018] c. abrading the surface to remove a portion of the surface, thereby providing a polished diamond surface.

[0019] In one embodiment, the diamond surface comprises a single diamond crystal.

[0020] In one embodiment, the diamond surface comprises polycrystalline diamond (PCD).

[0021] In another aspect, the invention provides a method for polishing a polycrystalline alumina surface, the method comprising: [0022] a. contacting the surface with a slurry composition comprising abrasive particles effective for abrading a polycrystalline alumina surface; [0023] b. moving the composition relative to the surface using a chemical mechanical polishing apparatus having a rotating polishing pad, wherein the pad has a surface roughness of about 0.2 to about 100 nm and a Shore D hardness of at least about 30, and [0024] c. abrading the surface to remove a portion of the surface, thereby providing a polished polycrystalline alumina surface.

[0025] In one embodiment, the polishing pad is comprised of a polymeric material. In one embodiment the polymeric material is chosen from poly(vinyl chloride), high density polyethylene (HDPE), and the like.

[0026] As noted above, the surface roughness (Ra) is about 0.2 to about 100 nm. In certain embodiments, the roughness is less than about 90, less than about 80, less than about 70, less than about 60, or less than about 50 nm.

[0027] In one embodiment, the porosity of the pad is about 0-50 m.Math.s/Kg. In one embodiment, the pad thickness is about 50 microns to about 15 mm. In one embodiment, the pad can be stacked or non-stacked, as depicted in FIG. 3; the base of the stacked pad can be a standard (hard or soft) polymeric pad.

[0028] In one embodiment, the slurry compositions effective for abrading a diamond surface are those which are known, many of which are commercially available. For example, slurry compositions comprising abrasives such as diamond, silicon carbide, alumina, silica, ceria, titania, zirconia, and the like can be utilized. Commercially available slurries include those containing diamond. Further examples of known slurries include those described in U.S. Pat. No. 9,567,492, incorporated herein by reference.

EXAMPLES

[0029] Examples 1, 2 & 3 were performed on Buehler Automet-250, with platen RPM of 120 and head RPM of 60. The pressure used was 4 psi for the PolySiC, Poly Diamond and Poly-Crystalline Alumina. The slurry flow rate was maintained at 30 mL/min and the surface finish was measured on Wyko optical profilometer with scan size of 300 um×255 um size.

[0030] Example 4 is performed on the same parameters as above at different pressure conditions on the ST-PCF-B pad.

[0031] ST-PCF-B is a non-porous ultra-smooth pad with a standard polymeric pad backing, having a Shore-D of 70 and a surface roughness of about 55 nm (Ra).

Example-1: Poly-Crystalline SiC Data on Different Pads with SND-9200-FA Slurry

[0032]

TABLE-US-00001 Surface finish Pad Optical Profilometer Suba-800 (DuPont) 2.2 nm IC-1000(DuPont) 1.8 nm D-100(Cabot) 1.2 nm ST-PCF-B 0.5 nm

Example-2: Poly-Crystalline Diamond Data on Different Pads with SND-9200-FA Slurry

[0033]

TABLE-US-00002 Surface finish Pad Optical Profilometer Suba-800 4.6 nm IC-1000 3.7 nm D100 1.8 nm ST-PCF-B 0.8 nm

Example-3: Poly-Crystalline Alumina Data on Different Pads with SND-9500-PCA Slurry

[0034]

TABLE-US-00003 Surface finish Pad Optical Profilometer Suba-800 8.8 nm IC-1000 5.8 nm D100 5.2 nm ST-PCF-B 2.2 nm

Example-4: Poly-Crystalline SiC Data on ST-PCF-B Pad with SND-9200-FA Slurry with a Pressure Ladder

[0035]

TABLE-US-00004 Surface finish Pressure (psi) Optical Profilometer 2 0.7 nm 4 0.5 nm 6 0.4 nm 8 0.6 nm

[0036] Having thus described several illustrative embodiments of the present disclosure, those of skill in the art will readily appreciate that yet other embodiments may be made and used within the scope of the claims hereto attached. Numerous advantages of the disclosure covered by this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many respects, only illustrative. The disclosure's scope is, of course, defined in the language in which the appended claims are expressed.