An indium phosphide polishing liquid and a polishing method

Abstract

The present invention discloses an indium phosphide polishing liquid and a polishing method. An indium phosphide polishing liquid includes a rough polishing liquid 1 and a fine polishing liquid 2 used in combination; the rough polishing liquid 1 is composed of trichloroisocyanuric acid, silicon dioxide abrasive A and high-purity water. Among them, the weight ratio of trichloroisocyanuric acid, silicon dioxide abrasive A and high-purity water is (18-36):(80-120):(3000-5000); the fine polishing liquid 2 is composed of trichloroisocyanuric acid, organic acid, silicon dioxide abrasive B, high-purity water and an acidic activator sodium benzenesulfonate. Among them, the organic acid is at least one of malic acid, lactic acid or citric acid. The weight ratio of trichloroisocyanuric acid, organic acid, silicon dioxide abrasive B, high-purity water and the acidic activator is (60-120):(60-300):(100-300):(20000-50000):(60-150). The rough polishing liquid of the present invention has simple composition, less dosage of effective components in the raw materials, high removal efficiency, effectively improves production efficiency, reduces production cost, improves polishing quality, and reduces dependence on foreign enterprises.

Description

Technical Field

[0001] The present invention relates to an indium phosphide polishing liquid and a polishing method, belonging to the technical field of indium phosphide polishing. Background Art

[0002] Indium phosphide is an important semiconductor material, which enables optical systems to provide the performance required for data centers, mobile backhaul, subway, and long-haul applications. Lasers, photodiodes, and waveguides fabricated on InP operate in the optimal transmission window of glass fibers, thus enabling efficient fiber optic communication. Indium phosphide is an important substrate material for fabricating high-speed devices, circuits, and optoelectronic integrated circuits. The surface quality of its polished wafers has an important impact on subsequent epitaxy and device performance. As an important parameter index for characterizing surface quality, surface roughness needs to be strictly controlled during the polishing process.

[0003] The growth method of VGF is used to provide high-performance indium phosphide wafers, which are sliced, ground, polished, and cleaned to meet the "ready-to-use" requirement. To meet the epitaxy requirements, polishing includes two steps: rough polishing and fine polishing. The existing rough polishing process has a removal rate of 0.3 - 0.5 μm / min, with low rough polishing efficiency, and the components of the rough polishing liquid are complex and costly; for fine polishing, an imported polishing liquid mixture is used to polish indium phosphide wafers to make the wafer surface meet the requirement of 0.3 nm. Due to the high price and long transportation cycle of the imported polishing mixture, the processing cost of indium phosphide wafers is high. Summary of the Invention

[0004] The present invention provides an indium phosphide polishing liquid and a polishing method. The components of the polishing liquid are simple, easy to configure, improve the rough polishing efficiency, and reduce the fine polishing cost.

[0005] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0006] An indium phosphide polishing liquid includes a rough polishing liquid 1 and a fine polishing liquid 2 used in combination;

[0007] The rough polishing liquid 1 is composed of trichloroisocyanuric acid, silica abrasive A, and high-purity water. Among them, the weight ratio of trichloroisocyanuric acid, silica abrasive A, and high-purity water is (18 - 36):(80 - 120):(3000 - 5000);

[0008] The fine polishing liquid 2 is composed of trichloroisocyanuric acid, organic acid, silica abrasive B, high-purity water, and acidic activator sodium benzenesulfonate. Among them, the organic acid is at least one of malic acid, lactic acid, or citric acid. The weight ratio of trichloroisocyanuric acid, organic acid, silica abrasive B, high-purity water, and acidic activator is (60 - 120):(60 - 300):(100 - 300):(20000 - 50000):(60 - 150).

[0009] When preparing the rough polishing liquid 1, mix all components evenly to obtain the rough polishing liquid 1; when preparing the fine polishing liquid 2, first mix trichloroisocyanuric acid, organic acid, silicon dioxide abrasive B and high-purity water evenly, and then add an acidic surfactant and mix evenly to obtain the fine polishing liquid 2.

[0010] The rough polishing liquid 1 and the fine polishing liquid 2 of this application need to be used in combination. That is, during the polishing process of indium phosphide, the rough polishing requires the use of the rough polishing liquid 1, and the fine polishing requires the use of the fine polishing liquid 2. The two are used in combination. Only in this way can the polishing effect be ensured, and this application only needs two steps of rough polishing and fine polishing to complete the polishing process, and no other polishing processes are required between or before and after rough polishing and fine polishing.

[0011] Trichloroisocyanuric acid provides oxidant and acid radical ions for the rough polishing liquid 1 and the fine polishing liquid 2, silicon dioxide A provides abrasive for the rough polishing liquid 1, and silicon dioxide B provides abrasive for the fine polishing liquid 2; the acidic surfactant uses sodium benzenesulfonate, which can increase the dispersion effect and lubricity during polishing and improve the surface quality.

[0012] The organic acid in the fine polishing liquid 2 is at least one of malic acid, lactic acid or citric acid, which is used to provide pH adjustment for the fine polishing liquid 2 and adjust the rate of chemical corrosion.

[0013] For the rough polishing liquid 1 and the fine polishing liquid 2 of the present invention, the raw materials used are convenient to obtain and can completely replace imported products, reducing the dependence on foreign companies.

[0014] The components of the rough polishing liquid 1 and the fine polishing liquid 2 of this application are simple and convenient to prepare, which improves the chemical reaction speed of the rough polishing liquid, improves the rough polishing efficiency, and reduces the fine polishing cost.

[0015] It should be noted that: the polishing processes of other wafers cannot be applied to indium phosphide wafers. For example, currently, germanium polishing liquid mainly uses a mixture of sodium bicarbonate + sodium hypochlorite + silicon dioxide abrasive. When it is used to polish indium phosphide wafers, since the alkaline solution does not react with indium phosphide, the formed oxide adheres to the wafer surface, resulting in basically no removal amount during polishing; another example is that gallium arsenide polishing liquid is composed of sodium dichloroisocyanurate + sodium sulfate + sodium polyphosphate + sodium bicarbonate + silicon dioxide abrasive. When it is used to polish indium phosphide, the surface of indium phosphide is oxidized but cannot be removed, so there is no removal amount during polishing. Therefore, for wafers of different materials, due to the differences in material properties, different polishing liquids need to be prepared.

[0016] In order to further improve the polishing effect, in the above-mentioned fine polishing liquid 2, when the organic acid is malic acid, the weight ratio of trichloroisocyanuric acid, organic acid, silica abrasive B, high-purity water and acidic surfactant is (60 - 120):(100 - 300):(100 - 300):(20000 - 50000):(60 - 150); when the organic acid is lactic acid, the weight ratio of trichloroisocyanuric acid, organic acid, silica abrasive B, high-purity water and acidic surfactant is (60 - 120):(80 - 240):(100 - 300):(20000 - 50000):(60 - 150); when the organic acid is citric acid, the weight ratio of trichloroisocyanuric acid, organic acid, silica abrasive B, high-purity water and acidic surfactant is (60 - 120):(60 - 180):(100 - 300):

[0017] (20000 - 50000):(60 - 150).

[0018] The selection of raw material grades will also directly affect the polishing effect. In order to better ensure the polishing effect, in the rough polishing liquid 1, the effective chlorine content of trichloroisocyanuric acid is greater than 90%, and the purity requirement is AR grade; the particle size of silica abrasive is required to be 60 - 140 nm, the effective abrasive concentration is 29 - 45%, and the chemical grade of the abrasive is EL grade; the purity requirement of high-purity water is not less than 18 MΩ.cm; in the fine polishing liquid 2, the effective chlorine content of trichloroisocyanuric acid is greater than 90%, and the purity requirement is AR grade; the purity requirement of organic acid is AR grade; the particle size of silica abrasive is required to be 10 - 30 nm, the effective abrasive concentration is 25 - 35%, and the chemical grade of the abrasive is EL grade; the purity requirement of high-purity water is not less than 18 MΩ.cm; the acidic surfactant used is sodium benzenesulfonate, and the purity requirement is AR grade.

[0019] A polishing method for indium phosphide wafers includes the following steps:

[0020] Step 1: Disk loading operation. Paste an acid-proof wax-free pad on the ceramic disk, place the wafer to be rough-polished into the holes of the acid-proof wax-free pad, and press the wafer tightly.

[0021] Step 2: Adsorb the ceramic disk with the wafer on the rough polishing machine head, lower the rough polishing machine head, turn on the peristaltic pump of the rough polishing liquid 1. When the rough polishing liquid 1 flows out, turn on the operation button of the polishing machine to complete rough polishing. Among them, the rotation speed of the rough polishing machine head is 50 - 70 rpm, the rotation speed of the fixed disk of the polishing machine is 60 - 90 rpm, the liquid outlet speed of the rough polishing liquid 1 is 700 - 800 ml / min, and the rough polishing removal amount is 1.5 - 2 μm / min.

[0022] Step 3: Adsorb the ceramic disc on the fine polishing machine head, lower the fine polishing machine head, turn on the peristaltic pump of the fine polishing liquid 2. When the fine polishing liquid 2 flows out, turn on the polishing machine button to complete fine polishing. Among them, the rotation speed of the fine polishing machine head is 40 - 80 revolutions / min, the rotation speed of the polishing machine's fixed disc is 50 - 90 revolutions / min, the liquid outlet speed of the fine polishing liquid 2 is 500 - 600 ml / min, and the fine polishing time is 8 - 15 minutes;

[0023] Step 4: Place the cassette in the sorting box of overflow high-purity water. After fine polishing, remove the ceramic disc, rinse it with a shower for 10 - 15 seconds, then use the wafer picker to pick up and hold the wafer, rinse it with a shower for 10 - 15 seconds, then insert the wafer into the cassette. After all the wafers on the ceramic disc are removed, put the cassette with the wafers into the spin dryer and spin dry.

[0024] The rough polishing machine head has a vacuum to adsorb the ceramic disc. An acid-proof wax-free pad is pasted on the ceramic disc, and indium phosphide wafers are placed in the holes of the wax-free pad. The rough polishing machine head descends and presses on the polishing machine's fixed disc. The rough polishing machine head and the polishing machine's fixed disc rotate in the same direction to achieve the polishing effect. The same is true for the fine polishing process.

[0025] The above steps are simple and convenient to operate.

[0026] To further ensure the polishing effect, in the above Step 1, the flatness (TTV) of the ceramic disc is not greater than 2 μm; the acid-proof wax-free pad is made of polyurethane foam, and the TTV requirement is not greater than 10 μm.

[0027] In Step 2, a Reed X62 - 360 - copper type polishing machine is used for rough polishing. The model of the peristaltic pump is BT600L type, and the pump head rotation speed is adjustable from 0 to 500 revolutions.

[0028] In Step 3, an AM - ADL810 single-sided polishing machine is used for fine polishing. The model of the peristaltic pump is BT600L type, and the pump head rotation speed is adjustable from 0 to 500 revolutions.

[0029] In Step 5, a CXS - 2150 type spin dryer is used. When spin drying, first rinse, then dry with nitrogen. The rinsing water pressure is 0.2 - 0.3 kg / cm2, the rinsing rotation speed is 600 ± 50 revolutions / minute, and the rinsing time is 100 ± 10 seconds; the nitrogen drying temperature is 30 - 40 °C, the drying time is 300 ± 10 seconds, and the drying rotation speed is 1500 ± 50 revolutions.

[0030] For technologies not mentioned in the present invention, refer to the prior art.

[0031] The present invention has the following beneficial effects:

[0032] 1. The composition of the rough polishing liquid of the present invention is simple, the dosage of the active ingredient in the raw materials is small, the removal efficiency is high, the production efficiency is effectively improved, the production cost is reduced, and mass production is easily achieved.

[0033] 2. The present invention uses a rough polishing liquid 1 and a fine polishing liquid 2 with specific compositions, and combines them with the parameters of a polishing machine to polish indium phosphide wafers. The composition of the polishing liquid is simple, all raw materials are domestic, convenient to purchase, short procurement cycle, low cost, no need to store a large amount of drugs, effectively reducing the cost of material hoarding and reducing the dependence on foreign companies.

[0034] 3. The polished wafers obtained by the present invention have a low surface roughness. After cleaning, the measured surface roughness is less than 0.2 nanometers, fully meeting the requirements of chip epitaxial wafers and meeting the requirement of "ready to use out of the box".

[0035] 4. The present invention adopts an acid-proof wax-free pad polishing method, effectively solving the pollution of organic matter in wax polishing, facilitating wax-free cleaning, and improving the cleaning quality of the wafer surface. Description of the Drawings

[0036] Figure 1 It is a micrograph of the roughness of the indium phosphide wafer obtained in Example 1;

[0037] Figure 2 It is a surface particle diagram of the indium phosphide wafer obtained in Example 1;

[0038] Figure 3 It is a scratch characterization diagram of the indium phosphide wafer obtained in Example 1;

[0039] Figure 4 It is a flatness characterization diagram of the indium phosphide wafer obtained in Example 1; Detailed Description of the Invention

[0040] In order to better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments. However, the content of the present invention is not limited to the following embodiments.

[0041] Example 1

[0042] Prepare 24 3-inch indium phosphide wafers to be polished. The electrical parameters of the wafers are: carrier concentration: 0.4 - 8 * 10 18 cm-3 (the equilibrium concentration of free electrons and free holes in an intrinsic semiconductor material, the common value is at 300K), mobility 1000 - 2000 cm 2 / V s (mobility is the average drift velocity of carriers generated under a unit electric field strength. Its unit is centimeter 2 / (volt · second), that is, cm 2 / V s); the wafer thickness is: 625 ± 25 μm.

[0043] Preparation of rough polishing liquid 1: Add 100 L of high-purity water into a 10 L chemical mixing tank. Weigh 400 g of trichloroisocyanuric acid and put it into the high-purity water and stir until dissolved. Weigh 2 kg of silicon dioxide abrasive and pour it into the chemical mixing tank and stir until dissolved. After stirring, take a sample to measure the pH value between 2.5 and 3.5. Among them, the available chlorine content of trichloroisocyanuric acid is greater than 95%, the purity requirement is AR grade, produced by Shanghai Aladdin Biochemical Technology Co., Ltd.; the particle size requirement of silicon dioxide abrasive is 80 - 120 nm, the effective abrasive concentration is 39 - 41%, the chemical grade of the abrasive is EL grade, produced by Beijing Aerospace Saide Technology Development Co., Ltd.; the resistivity of high-purity water is not less than 18 MΩ.cm.

[0044] Preparation of fine polishing liquid 2: Add 100 L of high-purity water into a 100 L chemical mixing tank. Weigh 160 g of trichloroisocyanuric acid and put it into the high-purity water and stir until dissolved. Weigh 0.4 kg of malic acid and put it into the high-purity water and stir until dissolved. Then weigh 0.4 kg of silicon dioxide abrasive and pour it into the chemical mixing tank and stir until dissolved. Add 200 g of acidic surfactant sodium benzenesulfonate into the solution and stir evenly; After stirring, take a sample to measure the pH value between 3 and 4. Among them, the available chlorine content of trichloroisocyanuric acid is greater than 95%, the purity requirement is AR grade, produced by Shanghai Aladdin Biochemical Technology Co., Ltd.; the purity requirement of organic acid is AR grade; the particle size requirement of silicon dioxide abrasive is 20 - 30 nm, the effective abrasive concentration is 29 - 31%, the chemical grade of the abrasive is EL grade, produced by Beijing Aerospace Saide Technology Development Co., Ltd.; the resistivity of high-purity water is not less than 18 MΩ.cm, and the acidic surfactant used is sodium benzenesulfonate, the purity requirement is AR grade, produced by Tianjin Guangfu Fine Chemical Research Institute.

[0045] A polishing method for indium phosphide wafers, comprising the following steps:

[0046] Step 1: Loading operation. Paste acid-proof wax-free pads on the ceramic disk. This time, the selected acid-proof wax-free pads are 3 inches. 6 acid-proof wax-free pads can be pasted on one ceramic disk. Each acid-proof wax-free pad has a hole. The depth of the wax-free pad hole is 500 μm, and the hole diameter is 76.8 mm. Place the wafer to be rough polished into the wax-free pad hole and press the wafer tightly by hand; Among them, the flatness (TTV) of the ceramic disk is 1 - 1.5 μm; the acid-proof wax-free pad is made of polyurethane foam, and the TTV is 5 - 10 μm.

[0047] Step 2: Adsorb the 4 ceramic disks with wafers on the rough polishing machine head, lower the rough polishing machine head, turn on the peristaltic pump of the rough polishing liquid 1, and the rotation speed of the peristaltic pump is 160 revolutions per minute. When the polishing liquid flows out, turn on the operation button of the polishing machine to start polishing. The rough polishing of the polishing machine uses a Reid X62 - 360 - copper type polishing machine, the rotation speed of the polishing head is 60 revolutions / min, and the rotation speed of the polishing disk is 70 revolutions / min; the model of the peristaltic pump: BT600L type, the liquid outlet speed of the rough polishing liquid 1 is 750 ml / min, the rough polishing removal amount is 30 μm, and the removal rate is 2 μm / min. The composition of the rough polishing liquid 1 is simple, the raw materials used are few, the removal efficiency is high, and the cost is low.

[0048] Step 3: Measure the thickness of 2 wafers. When the thickness meets the requirements of fine polishing, put the measured wafers back into the wax-free pad hole, adsorb the ceramic disc on the fine polishing machine head, lower the polishing head, turn on the peristaltic pump of fine polishing solution 2, control the speed of the peristaltic pump to 120 rpm, and turn on the polishing machine button when the polishing liquid flows out. Use AM-ADL810 single-sided polishing machine for fine polishing, with a polishing head speed of 50 rpm and a polishing disc speed of 60 rpm. Set the fine polishing time according to the requirements, and select a polishing time of 10 minutes. The peristaltic pump model is BT600L, and the liquid outlet rate of fine polishing solution 2 is 550ml / min.

[0049] Step 4: When the fine polishing time is up, quickly remove the polishing disc, flush with water for 12 seconds, remove the wafer with the wafer remover and hold the wafer, flush with water for 4 circles, insert the plug, place the plug in a 5L storage box, and overflow the storage box with high-purity water.

[0050] Step 5: Put the card with the wafer into the spin dryer, select the spin program, turn on the spin dryer button to spin dry, and complete the polishing step; the spin dryer uses a CXS-2150 type spin dryer, and the flushing water pressure is 0.2-0.3kg / cm 2 , flushing speed 600 rpm; nitrogen drying temperature 30-40℃, drying time 300S, drying speed 1500 rpm.

[0051] The surface roughness of the wafer after the polishing step was tested under an atomic force microscope, Ra = 0.100nm, and the test results are as follows Figure 1 Display: The surface particles of the wafer after the polishing step are tested by Candlea CS20. There are no particles with a size of ≥0.3μm. Figure 2 ; Check the surface scratches of the wafer after the polishing step under a strong light and microscope. There are no surface scratches. Figure 3 ; Use a flatness tester to test the flatness of the wafer after the polishing step. The wafer has high flatness, TTV test 3-5μm, see Figure 4 The above scheme was scaled up for production, with a production output of 480 wafers and a yield of 100%. The wafers that completed the polishing step all met or even exceeded the above test results, proving that the above scheme has stable operation, meets production requirements, and fully meets the requirements of chip substrates.

[0052] Comparative Example 1

[0053] Replace the dosage of trichloroisocyanuric acid in the rough polishing liquid 1 in Example 1 with 300 g, and the rest refer to Example 1. The rough polishing removal rate is 1.0 - 1.3 μm / min, and the removal rate decreases significantly. The surface quality of rough polishing is basically the same as that with a dosage of 400 g. Replace the dosage of trichloroisocyanuric acid in the rough polishing liquid 1 in Example 1 with 750 g, and the rest refer to Example 1. The dissolution rate of trichloroisocyanuric acid slows down, and a small amount of solid at the bottom does not dissolve. Compared with Example 1, the removal rate does not increase. The surface quality of the rough polished wafer is worse than that with a dosage of 400 g, with a little scratch.

[0054] Comparative Example 2

[0055] Replace the dosage of trichloroisocyanuric acid in the fine polishing liquid 1 in Example 1 with 110 g, and the rest refer to Example 1. The fine polishing removal rate decreases, with fewer scratches. The edge of the wafer surface is not sufficiently removed during the same fine polishing time, and the surface roughness Ra1 = 0.197. When the dosage of trichloroisocyanuric acid in the fine polishing liquid 1 in Example 1 is replaced with 250 g, the fine polishing removal amount increases compared with the original, the surface removal is sufficient, the surface roughness of the fine polished wafer Ra2 = 0.159, and there is an increasing trend.

[0056] Comparative Example 3

[0057] Replace the rough polishing liquid 1 in Example 1 with a conventional indium phosphide rough polishing liquid: 100 L of high-purity water + sodium dichloroisocyanurate (1000 g) + sodium bicarbonate (500 g) + silicon dioxide abrasive (2 L) + citric acid (50 L). The rest refer to Example 1. The flow rate of the polishing liquid is 750 ml / min, and the polishing removal rate is 0.4 μm / min. The removal rate is slow, the efficiency is low, and the consumption of citric acid is large, resulting in high cost.

Claims

1. An indium phosphide polishing liquid, characterized in that: It includes a rough polishing liquid 1 and a fine polishing liquid 2 used in combination; The rough polishing liquid 1 is composed of trichloroisocyanuric acid, silicon dioxide abrasive A and high-purity water. Among them, the weight ratio of trichloroisocyanuric acid, silicon dioxide abrasive A and high-purity water is (18 - 36):(80 - 120):(3000 - 5000); The fine polishing liquid 2 is composed of trichloroisocyanuric acid, organic acid, silicon dioxide abrasive B, high-purity water and an acidic activator. Among them, the organic acid is one of malic acid, lactic acid or citric acid; In the fine polishing liquid 2, when the organic acid is malic acid, the weight ratio of trichloroisocyanuric acid, organic acid, silicon dioxide abrasive B, high-purity water and acidic activator is (60 - 120):(100 - 300):(100 - 300):(20000 - 50000):(60 - 150); When the organic acid is lactic acid, the weight ratio of trichloroisocyanuric acid, organic acid, silicon dioxide abrasive B, high-purity water and acidic activator is (60 - 120):(80 - 240):(100 - 300):(20000 - 50000):(60 - 150); When the organic acid is citric acid, the weight ratio of trichloroisocyanuric acid, organic acid, silicon dioxide abrasive B, high-purity water and acidic activator is (60 - 120):(60 - 180):(100 - 300):(20000 - 50000):(60 - 150).

2. The indium phosphide polishing liquid according to claim 1, wherein: In the rough polishing liquid 1, the effective chlorine content of trichloroisocyanuric acid is greater than 90%, and the purity requirement is AR grade; the particle size requirement of silicon dioxide abrasive is 60 - 140 nm, the effective abrasive concentration is 29 - 45%, and the abrasive chemical grade is EL grade; the purity requirement of high-purity water is not less than 18 MΩ.cm.

3. The indium phosphide polishing liquid according to claim 1 or 2, characterized in that: In the fine polishing liquid 2, the effective chlorine content of trichloroisocyanuric acid is greater than 90%, and the purity requirement is AR grade; the purity requirement of organic acid is AR grade; the particle size requirement of silicon dioxide abrasive is 10 - 30 nm, the effective abrasive concentration is 25 - 35%, and the abrasive chemical grade is EL grade; the purity requirement of high-purity water is not less than 18 MΩ.cm; the acidic activator uses sodium benzenesulfonate, and the purity requirement is AR grade.

4. A polishing method for indium phosphide wafers, using the indium phosphide polishing liquid medicine according to any one of claims 1-3, characterized in that: It includes the following steps: Step 1: Disk loading operation. Paste an acid-proof wax-free pad on the ceramic disk, place the wafer to be rough-polished into the hole of the acid-proof wax-free pad, and press the wafer tightly; Step 2: Adsorb the ceramic disk with the wafer on the rough polishing machine head, lower the rough polishing machine head, turn on the peristaltic pump of the rough polishing liquid 1. When the rough polishing liquid 1 flows out, turn on the operation button of the polishing machine to complete rough polishing. Among them, the rotation speed of the rough polishing machine head is 50 - 70 r / min, the rotation speed of the fixed disk of the polishing machine is 60 - 90 r / min, the liquid outlet speed of the rough polishing liquid 1 is 700 - 800 ml / min, and the rough polishing removal amount is 1.5 - 2 μm / min; Step 3: Adsorb the ceramic disk on the fine polishing machine head, lower the fine polishing machine head, turn on the peristaltic pump of the fine polishing liquid 2. When the fine polishing liquid 2 flows out, turn on the button of the polishing machine to complete fine polishing. Among them, the rotation speed of the fine polishing machine head is 40 - 80 r / min, the rotation speed of the fixed disk of the polishing machine is 50 - 90 r / min, the liquid outlet speed of the fine polishing liquid 2 is 500 - 600 ml / min, and the fine polishing time is 8 - 15 minutes; Step 4: Place the cassette in the sorting box of overflow high-purity water. After the fine polishing is completed, remove the ceramic disc, flush it with a shower for 10 - 15 seconds, then use the wafer picker to pick up and hold the wafer, and flush it with a shower for 10 - 15 seconds. Then insert the wafer into the cassette. After all the wafers on the ceramic disc are removed, put the cassette with the wafers into the dryer and dry it.

5. The polishing method of an indium phosphide wafer according to claim 4, characterized in that: In Step 1, the flatness of the ceramic disc is not greater than 2μm; the acid-proof wax-free pad is made of polyurethane foam, and its flatness is not greater than 10μm.

6. The polishing method of an indium phosphide wafer according to claim 4 or 5, characterized in that: In Step 2, for rough polishing, use the Reid X62-360 copper-type polishing machine. The peristaltic pump model is BT600L, and the pump head speed is adjustable from 0 to 500 revolutions.

7. The polishing method of an indium phosphide wafer according to claim 4 or 5, characterized in that: In Step 3, for fine polishing, use the AM-ADL810 single-sided polishing machine. The peristaltic pump model is BT600L, and the pump head speed is adjustable from 0 to 500 revolutions.

8. The polishing method of an indium phosphide wafer as claimed in claim 4 or 5, characterized in that: In Step 4, use the CXS-2150 type dryer. When drying, first rinse, then dry with nitrogen. The rinsing water pressure is 0.2 - 0.3 kg / cm2, the rinsing speed is 600 ± 50 revolutions per minute, and the rinsing time is 100 ± 10 seconds; the nitrogen drying temperature is 30 - 40°C, the drying time is 300 ± 10 seconds, and the drying speed is 1500 ± 50 revolutions.

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