Polishing of polycrystalline materials

Abstract

The present invention provides a methodology for final finishing of hard surfaces such as diamond surfaces, in which a smooth pad having a surface roughness of about 0.2 nm to about 100 nm, e.g., a thickness in the range of about 0.02 mm to about 5 mm, and a Shore D hardness of 30 or greater is used in combination with a known polishing slurry to provide a diamond surface with an excellent smooth finish.

Description

[Technical Field]

[0001] The present invention relates generally to an improved method for polishing diamond and other hard surfaces. [Background technology]

[0002] Microelectronic device wafers are used to form integrated circuits. Microelectronic device wafers include a substrate (e.g., silicon) in which areas are patterned for the deposition of different materials with insulating, conductive, or semiconducting properties. To achieve accurate patterning, excess material used in forming layers on the substrate must be removed. Furthermore, creating a flat or planar microelectronic wafer surface prior to subsequent processing is often critical to creating functional and reliable circuits. Thus, it is necessary to planarize and / or polish certain surfaces of microelectronic device wafers.

[0003] Chemical-mechanical polishing or planarization (CMP) is a process in which material is removed from the surface of a microelectronic device wafer and the surface is planarized and polished by a combination of physical (e.g., polishing) and chemical (e.g., oxidation or chelation) processes. In its most basic form, CMP involves applying a slurry (e.g., a solution of abrasives and active chemicals) to a polishing pad that buffs the surface of the microelectronic device wafer, performing the removal, planarization, and polishing process. It is usually undesirable for the removal or polishing process to consist purely of physical or chemical action; rather, a synergistic combination of both is required to provide rapid and uniform removal. In integrated circuit fabrication, it is also desirable for CMP slurries to be able to preferentially remove films, including composite layers of metals and other materials, thereby producing a more highly planar surface for subsequent photolithography, patterning, etching, and thin-film processing. In a conventional CMP operation, a substrate carrier or polishing pad is attached to a carrier assembly and placed in contact with the polishing pad in a CMP apparatus. The carrier assembly provides a controllable pressure to the substrate, pressing the substrate against the polishing pad, which moves relative to the substrate.

[0004] There is a need to improve the CMP polishing rate of hard materials, such as diamond. In particular, diamond materials can be used as dielectrics, etch stops, or related functional elements for integrated circuits (ICs) and other related applications. In general, it is important that the overall friction of the CMP process is low and that polishing defects are substantially eliminated on the substrate surface. Furthermore, as the pressure and speed during polishing increase, there is a need to reduce the temperature rise during the polishing process. Reducing the temperature rise during the polishing process makes the process more stable and reproducible.

[0005] In particular, small-area single-crystal diamond substrates (e.g., 5 mm to 50 mm) and large-area polycrystalline diamond substrates (e.g., 25 mm to 150 mm) are being developed for many emerging applications (e.g., EUV lithography, gallium nitride (GaN) fabrication on diamond substrates for 6G communications, and diamond seeds for chemical vapor deposition of diamond for jewelry applications). A major challenge faced while polishing such materials involves the non-flatness of diamond particles. Because diamond particles have different orientations, chemical effects vary depending on the crystal direction, resulting in non-flat surfaces. New methods need to be developed to address these issues.

[0006] Certain hard slurry particles (e.g., diamond, cubic boron nitride, silicon carbide, and boron carbide) are commonly used to polish hard substrates (e.g., diamond) by mechanical processes (e.g., lapping and grinding). Generally, the size of the particles controls the polishing rate (i.e., material removal). However, because larger particles tend to cause greater surface and subsurface damage, multiple steps may be employed in the mechanical polishing process. For example, to improve removal rate while limiting undesired surface damage, initially, larger particles may be used in the initial CMP step(s), and then smaller particles may be used in the subsequent CMP step(s). Nevertheless, there remains a need to improve the overall surface finish of hard materials (e.g., diamond).

[0007] overview In summary, the present invention provides a method for final finishing of hard surfaces, such as diamond surfaces. In this method, a smooth pad having a surface roughness (Ra) of about 0.2 nm to about 100 nm, e.g., a thickness in the range of about 0.02 mm to about 5 mm, and a Shore D hardness of 30 or greater is used in combination with a known polishing slurry to provide a diamond surface with an excellent smooth finish. The pad may be made of a synthetic material, such as poly(vinyl chloride) (PVC) or other polymer. The pad used in the method of the present invention is extremely smooth (average roughness (Ra) of 0.2 nm to 100 nm) compared to conventional pads used in the final finishing of diamond surfaces, which have a relatively high roughness profile of >100 nm. When the diamond surface was polished using a CMP slurry in the method of the present invention, it was found that the diamond surface had a flatter topography and lower roughness for the polycrystalline diamond film and polycrystalline silicon carbide. [Brief explanation of the drawings]

[0008] [Figure 1] This is a 3D optical profilometer image of a diamond substrate polished with different particle sizes on a polycrystalline diamond surface (Comparative Example). The initial roughness ranges from 10 to 50 nm. Using a conventional pad, the within-wafer non-uniformity is high, resulting in a maximum roughness of 3 to 5 nm. [Figure 2] This is a 3D optical profiler image of a polycrystalline diamond (PCD) substrate polished using an ultra-smooth PVC pad. In this example, a roughness of approximately 0.3-1 nm is achievable. [Figure 3] 1 depicts the use of an ultra-smooth pad (with and without a standard polymer pad liner).

[0009] Detailed Description As used in this specification and the appended claims, the singular forms "a," "an," and "the" include the plural forms unless the content expressly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally used in its sense to include "and / or" unless the content expressly dictates otherwise.

[0010] The term "about" generally refers to a range of numbers considered equivalent to a stated value (e.g., having the same function or result). In many instances, the term "about" may include numbers rounded to the nearest significant figure.

[0011] Numerical ranges expressed using endpoints include all numbers subsumed within that range (eg, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

[0012] In a first aspect, the present invention provides a method of polishing a diamond surface, the method comprising: a. contacting the surface with a slurry composition comprising abrasive particles effective to polish the diamond surface; b. moving the slurry composition against the surface using a chemical mechanical polishing apparatus having a rotating polishing pad with a surface roughness of about 0.2-100 nm and a Shore D hardness of at least about 30; and c. polishing the surface to remove a portion of the surface, thereby providing a polished diamond surface; It includes:

[0013] In one embodiment, the diamond surface comprises a single crystal diamond.

[0014] In one embodiment, the diamond surface comprises polycrystalline diamond (PCD).

[0015] In another aspect, the present invention provides a method for polishing a polycrystalline alumina surface, the method comprising: a. contacting the surface with a slurry composition comprising abrasive particles effective to polish polycrystalline alumina surfaces; b. moving the slurry composition against the surface using a chemical mechanical polishing apparatus having a rotating polishing pad with a surface roughness of about 0.2-100 nm and a Shore D hardness of at least about 30; and c. polishing the surface to remove a portion of the surface, thereby providing a polished polycrystalline alumina surface; It includes:

[0016] In one embodiment, the polishing pad is composed of a polymeric material, hi one embodiment, the polymeric material is selected from poly(vinyl chloride), high density polyethylene (HDPE), and the like.

[0017] As noted above, the surface roughness (Ra) is from about 0.2 to about 100 nm. In certain embodiments, the surface roughness is less than about 90, less than about 80, less than about 70, less than about 60, or less than about 50 nm.

[0018] In one embodiment, the pad has a porosity of about 0 to 50 m.s / Kg. In one embodiment, the pad has a thickness of about 50 microns to about 15 mm. In one embodiment, the pads may or may not be stacked (as shown in Figure 3). The base of the stacked pads may be a standard (hard or soft) polymer pad.

[0019] In one embodiment, the slurry composition that is effective for polishing diamond surface is known, and many of them are commercially available.For example, the slurry composition that contains abrasive (for example, diamond, silicon carbide, alumina, silica, ceria, titania, zirconia, etc.) can be used.Commercially available slurries include those that contain diamond.Further examples of known slurries include those described in US Patent No. 9,567,492, which is incorporated by reference. [Example]

[0020] Examples 1, 2, and 3 were performed on a Buehler Automet-250 (120 platen RPM, 60 head RPM). The operating pressure was 4 psi for polycrystalline SiC, polycrystalline diamond, and polycrystalline alumina. The slurry flow rate was maintained at 30 mL / min, and the surface finish was measured with a Wyko optical profiler (scan size 300 μm x 255 μm).

[0021] Example 4 is carried out with the same parameters as previously described, but with different pressure conditions on the ST-PCF-B pad.

[0022] The ST-PCF-B is a non-porous, ultra-smooth pad with a standard polymer pad backing, a Shore D hardness of 70, and a surface roughness of approximately 55 nm (Ra).

[0023] Example 1: Polycrystalline SiC data on different pads using SND-9200-FA slurry TIFF0007801444000001.tif44170

[0024] Example 2: Polycrystalline diamond data with different pads using SND-9200-FA slurry TIFF0007801444000002.tif44170

[0025] Example 3: Polycrystalline Alumina Data on Different Pads Using SND-9200-FA Slurry TIFF0007801444000003.tif44170

[0026] Example 4: Polycrystalline SiC data on ST-PCF-B pad (with pressure ladder) using SND-9200-FA slurry TIFF0007801444000004.tif44170

[0027] Having thus described several exemplary embodiments of the present disclosure, those skilled in the art will immediately appreciate that still other embodiments may be made and used within the scope of the claims appended hereto. Many advantages of the disclosure covered by this document have been described above. It will be understood, however, that this disclosure is, in many respects, merely illustrative. The scope of the present disclosure will, of course, be defined in the language in which the appended claims are expressed.

Claims

1. 1. A method of polishing a diamond surface, comprising: contacting the diamond surface with a slurry composition comprising abrasive particles effective to polish the diamond surface; b. moving the slurry composition against the diamond surface using a chemical mechanical polishing apparatus having a rotating polishing pad with a surface roughness of 0.2 to 90 nm and a Shore D hardness of at least 30; and c. polishing the diamond surface to remove a portion of the diamond surface, thereby providing a polished diamond surface; A method comprising:

2. The method of claim 1 , wherein the diamond surface comprises a diamond single 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 constructed from a polymeric material.

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

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

7. 1. A method for polishing a polycrystalline alumina surface, comprising: contacting the polycrystalline alumina surface with a slurry composition comprising abrasive particles effective to polish the polycrystalline alumina surface; b. moving the slurry composition against the polycrystalline alumina surface using a chemical mechanical polishing apparatus having a rotating polishing pad with a surface roughness of 0.2 to 90 nm and a Shore D hardness of at least 30; and c. polishing the polycrystalline alumina surface to remove a portion of the polycrystalline alumina surface, thereby providing a polished polycrystalline alumina surface; A method comprising:

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

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

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

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