Lithium niobate wafer CMP processing method

Abstract

The invention relates to the technical field of lithium niobate wafers, in particular to a lithium niobate wafer CMP (chemical mechanical polishing) processing method which comprises the following steps: performing double-sided grinding on a cut 4 / 6-inch lithium niobate wafer, and then performing ultrasonic cleaning to obtain a 4 / 6-inch lithium niobate double-sided grinding wafer with a rough structure on the surface; performing CMP rough polishing on the 4 / 6-inch lithium niobate double-sided grinding sheet by using a double-sided polishing machine and a polishing solution matched with a polishing pad, and then performing ultrasonic cleaning to obtain a 4 / 6-inch lithium niobate rough polishing sheet; and carrying out CMP fine polishing on the 4 / 6-inch lithium niobate rough polishing sheet by using a double-sided polishing machine and a polishing solution matched with a polishing pad, and then carrying out ultrasonic cleaning to obtain the 4 / 6-inch lithium niobate double-polished sheet. According to the method, after the obtained lithium niobate grinding sheet is directly subjected to CMP double-sided polishing, the final lithium niobate double-polished sheet with higher surface precision can be obtained, the lithium niobate processing technology is simplified, the production efficiency is improved, the method is suitable for a double-polishing machine and batch production, the universality to a polishing pad is high, the polishing speed is high, the double-polished surface precision is high, and the production cost is low. The polishing machine is suitable for the field of efficient polishing of 4 / 6-inch lithium niobate wafers.

Description

Technical Field

[0001] The invention relates to the technical field of lithium niobate wafers, in particular to a CMP processing method for lithium niobate wafers. Background Art

[0002] Lithium niobate (LiNbO3, LN for short) is a chemical substance with a trigonal crystal system, an ilmenite-type (distorted perovskite-type) structure, and a relative density of 4.30 g / cm 3 , Mohs hardness 5, Curie point 1140℃, is a multifunctional material integrating piezoelectric, ferroelectric, pyroelectric, nonlinear, optoelectronic, photoelastic, photorefractive and other functions. LN has received more and more attention due to its excellent physical properties, and has been widely used in aviation, aerospace, civilian optoelectronic products and other fields. In the field of optical communications, lithium niobate is suitable for making various control coupling and transmission devices of light, such as optical isolation, amplification, waveguide, modulation, etc. LN is characterized by extremely low fracture toughness and hardness. 4 / 6-inch lithium niobate wafers are very easy to break during processing, resulting in a high scrap rate, extremely low processing efficiency, and low surface accuracy, resulting in low production efficiency and increased production costs.

[0003] In the existing lithium niobate processing method, the LN processing technology is relatively complicated. The cut 4 / 6-inch lithium niobate wafer is double-sided ground to obtain a lithium niobate double-sided ground sheet with a rough surface structure, and then double-sided thinning is performed to obtain a lithium niobate double-sided thinned sheet with a rough surface structure; chemical etching is directly performed in a closed container containing a uniform mixture of nitric acid, hydrofluoric acid and a sustained-release agent to obtain a lithium niobate etching sheet with a random and disordered pit structure on the surface; double-sided polishing is then performed using a double-sided polishing machine and a polishing liquid, and ultrasonic cleaning is performed to obtain the final lithium niobate double-polished sheet. Especially when the 4 / 6-inch lithium niobate wafer is polished, the processing efficiency is low and the double-sided polished surface roughness cannot meet the requirements. Summary of the invention

[0004] The purpose of the present invention is to provide a CMP processing method for lithium niobate wafers in view of the problems existing in the prior art.

[0005] In order to achieve the above object, the technical solution provided by the present invention is as follows:

[0006] A CMP processing method for a lithium niobate wafer, characterized by comprising the following steps:

[0007] Step 1: Double-sided grinding of the cut 4 / 6-inch lithium niobate wafer, the surface roughness Sa of the lithium niobate wafer after grinding is less than 200nm, and the flatness is less than 7um, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-sided grinding sheet with a rough surface structure;

[0008] Step 2: Use a double-sided polishing machine and polishing liquid with a polishing pad to perform CMP rough polishing on a 4 / 6-inch lithium niobate double-sided polishing sheet. The polishing unit surface pressure is 100g / cm 2 ~600g / cm 2 , the polishing upper and lower discs rotate at 30rpm to 60rpm, the polishing temperature is 32 to 38°C, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 1nm, the flatness is less than 2um, the wafer surface has ≤3 scratches and ≤10 pits, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate rough polished wafer;

[0009] Step 3: Use a double-sided polishing machine and polishing liquid with a polishing pad to perform CMP fine polishing on the 4 / 6-inch lithium niobate rough polishing sheet. The polishing unit surface pressure is 200g / cm 2 ~250g / cm 2 The polishing upper and lower disc speeds are 35rpm~40rpm, and the polishing temperature is 38~40℃, so that the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 0.2nm, the flatness is less than 1um, and there are no scratches or pits on the wafer surface. Ultrasonic cleaning is then performed to obtain a 4 / 6-inch lithium niobate double-polished wafer.

[0010] Preferably, in step one, the grinding abrasive is a mixture of one or more of boron carbide, diamond, aluminum oxide or silicon carbide.

[0011] Preferably, in step 2 and step 3, the polishing liquid is alkaline cerium oxide.

[0012] Preferably, the polishing pad is a synthetic fiber polishing pad or a damping cloth.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. The present invention provides a CMP processing method for a lithium niobate wafer, wherein the chemical formula of the lithium niobate single crystal is LiNbO3, the diameter of the lithium niobate single crystal is 100 mm to 200 mm, the roughness Sa of the lithium niobate wafer is less than 0.2 nm, and the flatness is less than 1 um.

[0015] 2. The present invention provides a CMP processing method for lithium niobate wafers. The processing of lithium niobate by this method has the characteristics of simplified processing technology, fast polishing rate, high double-polishing surface accuracy, etc., and is suitable for efficient polishing of lithium niobate wafers.

[0016] 3. After obtaining the lithium niobate grinding sheet, the present invention directly performs CMP double-sided polishing to obtain a lithium niobate double-polished sheet with higher final surface accuracy, thereby simplifying the lithium niobate processing technology and improving production efficiency. The present invention is suitable for double-polishing machines and batch production, has strong versatility for polishing pads, has the characteristics of fast polishing rate and high double-polishing surface accuracy, and is suitable for the field of efficient polishing of 4 / 6-inch lithium niobate wafers. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The same processing pressure (pressure 200g / cm 2 ), the change of removal rate and surface roughness at different rotation speeds of upper and lower plates;

[0018] Figure 2 The same processing pressure (pressure 350g / cm 2 ), the change of removal rate and surface roughness at different rotation speeds of upper and lower plates;

[0019] Figure 3 The same processing pressure (pressure 500g / cm 2 ), the change of removal rate and surface roughness at different rotation speeds of upper and lower plates;

[0020] Figure 4 This is a graph showing the effect of different pressures on the removal rate and surface roughness at the same upper and lower disk speeds (30-40 rpm) in an embodiment of the present invention;

[0021] Figure 5 This is a graph showing the effect of different pressures on the removal rate and surface roughness at the same upper and lower disk speeds (speed 40-50 rpm) in an embodiment of the present invention;

[0022] Figure 6 This is a graph showing the effect of different pressures on the removal rate and surface roughness at the same upper and lower disk speeds (speed 50-60 rpm) in an embodiment of the present invention;

[0023] Figure 7 This is a picture of the optimal surface roughness of the lithium niobate double-polished sheet in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Example 1

[0026] A CMP processing method for a lithium niobate wafer comprises the following steps:

[0027] Step 1: The cut 4 / 6-inch lithium niobate wafer is double-sided ground, and the surface roughness Sa of the lithium niobate wafer after grinding is less than 200nm, and the flatness is less than 7um, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-sided ground sheet with a rough surface structure;

[0028] Step 2: Use a double-sided polishing machine and polishing liquid with a synthetic fiber polishing pad to perform CMP rough polishing on a 4 / 6-inch lithium niobate double-sided grinding sheet. The polishing unit surface pressure is 200g / cm 2 , the polishing upper and lower discs rotate at 30rpm to 40rpm, the polishing temperature is 32 to 38°C, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 1nm, the flatness is less than 2um, the wafer surface has ≤3 scratches and ≤10 pits, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate rough polished wafer;

[0029] Step 3: Use a double-sided polishing machine and polishing liquid with a damping cloth to perform CMP fine polishing on the 4 / 6-inch lithium niobate rough polishing sheet. The polishing unit surface pressure is 200g / cm 2 ~250g / cm 2 , the polishing upper and lower discs rotate at 35rpm-40rpm, the polishing temperature is 38-40℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 0.2nm, the flatness is less than 1um, and there are no scratches or pits on the wafer surface, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-polished wafer;

[0030] like Figure 1 and Figure 4 As shown, the double-sided removal rate of lithium niobate double-polished sheet in Example 1 is 20.24 μm / h, and the surface roughness Sa is 0.279 nm; Example 2

[0031] Step 1: The cut 4 / 6-inch lithium niobate wafer is double-sided ground, and the surface roughness Sa of the lithium niobate wafer after grinding is less than 200nm, and the flatness is less than 7um, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-sided ground sheet with a rough surface structure;

[0032] Step 2: Use a double-sided polishing machine and polishing liquid with a synthetic fiber polishing pad to perform CMP rough polishing on a 4 / 6-inch lithium niobate double-sided grinding sheet. The polishing unit surface pressure is 200g / cm 2 , the polishing upper and lower disc speeds are 40rpm~50rpm, the polishing temperature is 32~38℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 1nm, the flatness is less than 2um, the wafer surface has ≤3 scratches and ≤10 pits, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate rough polished wafer;

[0033] Step 3: Use a double-sided polishing machine and polishing liquid with a damping cloth to perform CMP fine polishing on the 4 / 6-inch lithium niobate rough polishing sheet. The polishing unit surface pressure is 200g / cm 2 ~250g / cm 2, the polishing upper and lower discs rotate at 35rpm-40rpm, the polishing temperature is 38-40℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 0.2nm, the flatness is less than 1um, and there are no scratches or pits on the wafer surface, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-polished wafer;

[0034] like Figure 1 and Figure 5 As shown, the double-sided removal rate of the lithium niobate double-polished sheet in Example 2 is 25.85 μm / h, and the surface roughness Sa is 0.243 nm; Example 3

[0035] Step 1: The cut 4 / 6-inch lithium niobate wafer is double-sided ground, and the surface roughness Sa of the lithium niobate wafer after grinding is less than 200nm, and the flatness is less than 7um, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-sided ground sheet with a rough surface structure;

[0036] Step 2: Use a double-sided polishing machine and polishing liquid with a synthetic fiber polishing pad to perform CMP rough polishing on a 4 / 6-inch lithium niobate double-sided grinding sheet. The polishing unit surface pressure is 200g / cm 2 , the polishing upper and lower discs rotate at 50rpm-60rpm, the polishing temperature is 32-38℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 1nm, the flatness is less than 2um, the wafer surface has ≤3 scratches and ≤10 pits, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate rough polished wafer;

[0037] Step 3: Use a double-sided polishing machine and polishing liquid with a damping cloth to perform CMP fine polishing on the 4 / 6-inch lithium niobate rough polishing sheet. The polishing unit surface pressure is 200g / cm 2 ~250g / cm 2 , the polishing upper and lower discs rotate at 35rpm-40rpm, the polishing temperature is 38-40℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 0.2nm, the flatness is less than 1um, and there are no scratches or pits on the wafer surface, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-polished wafer;

[0038] like Figure 1 and Figure 6 As shown, the double-sided removal rate of the lithium niobate double-polished sheet in Example 3 is 31.51 μm / h, and the surface roughness Sa is 0.225 nm;

[0039] Example 4

[0040] Step 1: The cut 4 / 6-inch lithium niobate wafer is double-sided ground, and the surface roughness Sa of the lithium niobate wafer after grinding is less than 200nm, and the flatness is less than 7um, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-sided ground sheet with a rough surface structure;

[0041] Step 2: Use a double-sided polishing machine and polishing liquid with a synthetic fiber polishing pad to perform CMP rough polishing on a 4 / 6-inch lithium niobate double-sided grinding sheet. The polishing unit surface pressure is 350g / cm 2 , the polishing upper and lower discs rotate at 30rpm to 40rpm, the polishing temperature is 32 to 38°C, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 1nm, the flatness is less than 2um, the wafer surface has ≤3 scratches and ≤10 pits, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate rough polished wafer;

[0042] Step 3: Use a double-sided polishing machine and polishing liquid with a damping cloth to perform CMP fine polishing on the 4 / 6-inch lithium niobate rough polishing sheet. The polishing unit surface pressure is 200g / cm 2 ~250g / cm 2 , the polishing upper and lower discs rotate at 35rpm-40rpm, the polishing temperature is 38-40℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 0.2nm, the flatness is less than 1um, and there are no scratches or pits on the wafer surface, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-polished wafer;

[0043] like Figure 2 and Figure 4 As shown, the double-sided removal rate of lithium niobate double-polished sheet in Example 4 is 35.09 μm / h, and the surface roughness Sa is 0.256 nm; Example 5

[0044] Step 1: The cut 4 / 6-inch lithium niobate wafer is double-sided ground, and the surface roughness Sa of the lithium niobate wafer after grinding is less than 200nm, and the flatness is less than 7um, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-sided ground sheet with a rough surface structure;

[0045] Step 2: Use a double-sided polishing machine and polishing liquid with a synthetic fiber polishing pad to perform CMP rough polishing on a 4 / 6-inch lithium niobate double-sided grinding sheet. The polishing unit surface pressure is 350g / cm 2 , the polishing upper and lower disc speeds are 40rpm~50rpm, the polishing temperature is 32~38℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 1nm, the flatness is less than 2um, the wafer surface has ≤3 scratches and ≤10 pits, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate rough polished wafer;

[0046] Step 3: Use a double-sided polishing machine and polishing liquid with a damping cloth to perform CMP fine polishing on the 4 / 6-inch lithium niobate rough polishing sheet. The polishing unit surface pressure is 200g / cm 2 ~250g / cm 2, the polishing upper and lower discs rotate at 35rpm-40rpm, the polishing temperature is 38-40℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 0.2nm, the flatness is less than 1um, and there are no scratches or pits on the wafer surface, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-polished wafer;

[0047] like Figure 2 and Figure 5 As shown, the double-sided removal rate of the lithium niobate double-polished sheet in Example 5 is 40.44 μm / h, and the surface roughness Sa is 0.198 nm;

[0048] Step 1: The cut 4 / 6-inch lithium niobate wafer is double-sided ground, and the surface roughness Sa of the lithium niobate wafer after grinding is less than 200nm, and the flatness is less than 7um, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-sided ground sheet with a rough surface structure;

[0049] Step 2: Use a double-sided polishing machine and polishing liquid with a synthetic fiber polishing pad to perform CMP rough polishing on a 4 / 6-inch lithium niobate double-sided grinding sheet. The polishing unit surface pressure is 350g / cm 2 , the polishing upper and lower discs rotate at 50rpm-60rpm, the polishing temperature is 32-38℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 1nm, the flatness is less than 2um, the wafer surface has ≤3 scratches and ≤10 pits, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate rough polished wafer;

[0050] Step 3: Use a double-sided polishing machine and polishing liquid with a damping cloth to perform CMP fine polishing on the 4 / 6-inch lithium niobate rough polishing sheet. The polishing unit surface pressure is 200g / cm 2 ~250g / cm 2 , the polishing upper and lower discs rotate at 35rpm-40rpm, the polishing temperature is 38-40℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 0.2nm, the flatness is less than 1um, and there are no scratches or pits on the wafer surface, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-polished wafer;

[0051] like Figure 2 and Figure 6 As shown, the double-sided removal rate of lithium niobate double-polished sheet in Example 6 is 42.03 μm / h, and the surface roughness Sa is 0.221 nm; Example 7

[0052] Step 1: The cut 4 / 6-inch lithium niobate wafer is double-sided ground, and the surface roughness Sa of the lithium niobate wafer after grinding is less than 200nm, and the flatness is less than 7um, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-sided ground sheet with a rough surface structure;

[0053] Step 2: Use a double-sided polishing machine and polishing liquid with a synthetic fiber polishing pad to perform CMP rough polishing on a 4 / 6-inch lithium niobate double-sided polishing sheet. The polishing unit surface pressure is 500g / cm 2 , the polishing upper and lower discs rotate at 30rpm to 40rpm, the polishing temperature is 32 to 38°C, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 1nm, the flatness is less than 2um, the wafer surface has ≤3 scratches and ≤10 pits, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate rough polished wafer;

[0054] Step 3: Use a double-sided polishing machine and polishing liquid with a damping cloth to perform CMP fine polishing on the 4 / 6-inch lithium niobate rough polishing sheet. The polishing unit surface pressure is 200g / cm 2 ~250g / cm 2 , the polishing upper and lower discs rotate at 35rpm-40rpm, the polishing temperature is 38-40℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 0.2nm, the flatness is less than 1um, and there are no scratches or pits on the wafer surface, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-polished wafer;

[0055] like Figure 3 and Figure 4 As shown, the double-sided removal rate of lithium niobate double-polished sheet in Example 7 is 38.39 μm / h, and the surface roughness Sa is 0.262 nm; Example 8

[0056] Step 1: The cut 4 / 6-inch lithium niobate wafer is double-sided ground, and the surface roughness Sa of the lithium niobate wafer after grinding is less than 200nm, and the flatness is less than 7um, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-sided ground sheet with a rough surface structure;

[0057] Step 2: Use a double-sided polishing machine and polishing liquid with a synthetic fiber polishing pad to perform CMP rough polishing on a 4 / 6-inch lithium niobate double-sided polishing sheet. The polishing unit surface pressure is 500g / cm 2 , the polishing upper and lower disc speeds are 40rpm~50rpm, the polishing temperature is 32~38℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 1nm, the flatness is less than 2um, the wafer surface has ≤3 scratches and ≤10 pits, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate rough polished wafer;

[0058] Step 3: Use a double-sided polishing machine and polishing liquid with a damping cloth to perform CMP fine polishing on the 4 / 6-inch lithium niobate rough polishing sheet. The polishing unit surface pressure is 200g / cm 2 ~250g / cm 2, the polishing upper and lower discs rotate at 35rpm-40rpm, the polishing temperature is 38-40℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 0.2nm, the flatness is less than 1um, and there are no scratches or pits on the wafer surface, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-polished wafer;

[0059] like Figure 3 and Figure 5 As shown, the double-sided removal rate of lithium niobate double-polished sheet in Example 8 is 42.80 μm / h, and the surface roughness Sa is 0.230 nm; Example 9

[0060] Step 1: The cut 4 / 6-inch lithium niobate wafer is double-sided ground, and the surface roughness Sa of the lithium niobate wafer after grinding is less than 200nm, and the flatness is less than 7um, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-sided ground sheet with a rough surface structure;

[0061] Step 2: Use a double-sided polishing machine and polishing liquid with a synthetic fiber polishing pad to perform CMP rough polishing on a 4 / 6-inch lithium niobate double-sided polishing sheet. The polishing unit surface pressure is 500g / cm 2 , the polishing upper and lower discs rotate at 50rpm-60rpm, the polishing temperature is 32-38℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 1nm, the flatness is less than 2um, the wafer surface has ≤3 scratches and ≤10 pits, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate rough polished wafer;

[0062] Step 3: Use a double-sided polishing machine and polishing liquid with a damping cloth to perform CMP fine polishing on the 4 / 6-inch lithium niobate rough polishing sheet. The polishing unit surface pressure is 200g / cm 2 ~250g / cm 2 , the polishing upper and lower discs rotate at 35rpm-40rpm, the polishing temperature is 38-40℃, the roughness Sa of the 4 / 6-inch lithium niobate wafer is less than 0.2nm, the flatness is less than 1um, and there are no scratches or pits on the wafer surface, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-polished wafer;

[0063] like Figure 3 and Figure 6 As shown, the double-sided removal rate of the lithium niobate double-polished sheet in Example 9 is 45.01 μm / h, and the surface roughness Sa is 0.249 nm;

[0064] Comparative Examples and Test Results Analysis: In the CMP processing method for lithium niobate wafers, under normal polishing conditions after grinding, the removal rate of lithium niobate is proportional to the rotation speed of the upper and lower plates of the double polishing machine and the polishing pressure per unit area. The higher the polishing machine speed, the greater the polishing pressure per unit area, and the faster the lithium niobate removal rate. The surface roughness of the lithium niobate wafer is uneven when the machine speed is too high and the polishing pressure per unit area is too high, and the surface roughness increases. Comprehensive comparison of 9 examples, such as Figure 7 As shown, the best performance is Example 5, with a polishing double-side removal rate MRR of 40.44 μm / h and a surface roughness Sa of 0.198 nm.

[0065] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A CMP processing method for lithium niobate wafers, characterized in that: The steps include: Step 1: Double-sided grinding of the cut 4 / 6-inch lithium niobate wafer is performed, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate double-sided grinding sheet with a rough surface structure; Step 2: CMP rough polishing of a 4 / 6-inch lithium niobate double-sided grinding sheet is performed using a double-sided polishing machine, a polishing liquid and a polishing pad, and then ultrasonic cleaning is performed to obtain a 4 / 6-inch lithium niobate rough polishing sheet; Step 3: Use a double-sided polishing machine and a polishing liquid with a polishing pad to perform CMP fine polishing on the 4 / 6-inch lithium niobate rough-polished sheet, and then perform ultrasonic cleaning to obtain a 4 / 6-inch lithium niobate double-polished sheet.

2. A lithium niobate wafer CMP processing method according to claim 1, characterized in that: In step one, the grinding abrasive is a mixture of one or more of boron carbide, diamond, aluminum oxide or silicon carbide.

3. A lithium niobate wafer CMP processing method according to claim 1, characterized in that: In step one, the roughness Sa of the 4 / 6-inch lithium niobate wafer obtained by grinding is less than 200 nm, and the flatness is less than 7 um.

4. The CMP processing method for lithium niobate wafer according to claim 1, characterized in that: In step 2, the CMP rough polishing unit surface pressure is 100g / cm 2 ~600g / cm 2 The polishing upper and lower disk speeds are 30rpm~60rpm, and the polishing temperature is 32~38℃.

5. The CMP processing method for lithium niobate wafer according to claim 1, characterized in that: In step 2, the roughness Sa of the 4 / 6-inch lithium niobate wafer obtained by rough polishing is less than 1 nm, the flatness is less than 2 um, and the number of scratches on the wafer surface is ≤3 and the number of pits is ≤10.

6. A lithium niobate wafer CMP processing method according to claim 1, characterized in that: In step 3, the polishing unit surface pressure of the CMP fine polishing is 200g / cm 2 ~250g / cm 2 The polishing upper and lower disk speeds are 35rpm~40rpm, and the polishing temperature is 38~40℃.

7. The CMP processing method for lithium niobate wafer according to claim 1, characterized in that: In step three, the roughness Sa of the 4 / 6-inch lithium niobate wafer obtained by the precision polishing is less than 0.2 nm, the flatness is less than 1 um, and there are no scratches or pits on the surface of the wafer.

8. The CMP processing method for lithium niobate wafer according to claim 1, characterized in that: In step 2 and step 3, the polishing liquid is alkaline cerium oxide.

9. A lithium niobate wafer CMP processing method according to claim 1, characterized in that: The polishing pad is a synthetic fiber polishing pad or a damping cloth.

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