A sapphire wafer and a method for manufacturing the same

Abstract

The application relates to the technical field of sapphire processing, in particular to a sapphire wafer and a preparation method thereof. The method comprises the following steps: first contact of a sapphire raw wafer with a resin copper disc I on a polishing machine to obtain an intermediate wafer; second contact of an unpolished surface of the intermediate wafer with a resin copper disc II on the polishing machine; the resin copper disc is prepared from raw materials containing the following components: 25-30 wt% of a resin binder, 64-69 wt% of copper powder, 3-8 wt% of artificial diamond, 0.8-1 wt% of a curing agent and 2-3 wt% of a filling agent. The sapphire wafer is prepared by using a specific resin copper disc, the sapphire processing procedure is optimized under the premise of ensuring the processing quality, and the double-side grinding procedure in the traditional process is omitted; the sapphire wafer processing rate is improved, and the sapphire processing cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of sapphire processing technology, specifically to a sapphire wafer and its preparation method. Background Technology

[0002] Sapphire possesses superior mechanical properties, chemical stability, high hardness, and excellent light transmittance, making it widely used in semiconductor lighting, smart wearables, and precision instruments. All sapphire applications require cutting, grinding, and polishing processes. Cutting involves using diamond wire to cut sapphire ingots / blocks into wafers. Grinding involves double-sided grinding to remove wire cut marks; for single-sided polishing of substrates, it's necessary to determine if the back roughness meets customer requirements. Polishing is further divided into copper polishing and soft polishing. The main purpose of copper polishing is to remove the grinding damage layer. Taking sapphire substrates as an example, the grinding process takes longer than copper polishing and removes a larger amount of material. The amount of boron carbide powder used in the grinding process is also larger, resulting in higher costs, especially for large-size sapphire substrates. This is because the thickness of the sapphire increases with size. The amount of material removed in each process also increases. Taking a 4-inch sapphire substrate as an example, the grinding process removes 80μm, and to ensure the back roughness of the substrate, the grinding removal rate is 0.9μm / min; the grinding process takes approximately 89 minutes. For a 6-inch sapphire substrate, the grinding process removes 130μm, with a grinding removal rate of 0.9μm / min; the grinding process takes approximately 144 minutes. Therefore, the processing time for each process of large-size sapphire is longer, resulting in a longer processing cycle for large-size sapphire parts, thus affecting the total output. In addition, due to the increased processing volume in each process, the processing cost of large-size sapphire will also increase accordingly. Therefore, it is particularly important to reduce the production cost of large-size sapphire substrates and other large-size window wafers while ensuring quality requirements, and at the same time improve the processing efficiency of large-size wafers.

[0003] The existing copper polishing process for sapphire parts involves creating annular grooves on a resin copper disc. These grooves serve as a carrier for the diamond polishing slurry. During processing, a spraying device continuously sprays diamond polishing slurry onto the disc surface, ensuring full contact between the sapphire surface and the sapphire slurry, thus guaranteeing a high removal rate. However, as the grooves wear down, the removal rate of the copper polishing gradually decreases, and the processing time increases. When the resin copper disc wears to a certain extent (and can no longer hold a certain amount of polishing slurry), the grooves need to be re-grooved. This repeated grooving wastes the resin copper disc and affects the efficiency of continuous operation.

[0004] CN107282931A discloses a special grinding resin copper disc, comprising 15-37% resin binder, 60-85% copper powder, 0.4-1.5% curing agent, and 0.6-2% additives. This special grinding resin copper disc can improve the grinding efficiency and accuracy of workpieces, and save grinding costs, and can replace imported resin copper discs. However, when used in gemstone processing, the spraying of diamond polishing fluid cannot guarantee a uniform distribution of the diamond fluid on the disc surface, easily causing the diamond fluid to accumulate in the grooves of the copper disc. This cannot guarantee uniform contact between the wafer surface and the polishing material during processing. Moreover, copper polishing has a high grinding speed, and the thickness difference of the finished product at the copper polishing station is measured in micrometers. Uneven contact during grinding cannot guarantee the flatness of the wafer surface, and the disc tilting commonly seen in polishing processes is prone to occur.

[0005] CN116394154A discloses a novel method for preparing a grinding copper disc. The method includes: preparing a grinding copper disc blank; opening grooves in the prepared grinding copper disc, the spacing between the grooves forming a cube, and abrasive holes being provided on the cube; preparing bonded abrasive; embedding the bonded abrasive containing a metal binder into the abrasive holes, the abrasive particle size being between 800# and 2000#; and correcting the grinding disc to achieve a certain flatness after the abrasive is embedded, thus completing the finished product. Its advantages are that by replacing the original pure copper disc with free diamond slurry for grinding with a bonded abrasive copper disc, no additional abrasive needs to be added during use; only water needs to be added. The process is clean and pollution-free, with a long service life, making it an environmentally friendly consumable. However, when this grinding copper disc is used in gemstone processing, just like the traditional method of spraying diamond polishing fluid, it cannot guarantee uniform contact between the wafer surface and the polishing material during processing. Moreover, the grinding speed of copper polishing is fast, and the thickness difference of the finished product after copper polishing is measured in micrometers. Therefore, this inlaid copper disc, like the method of spraying diamond fluid, cannot guarantee the flatness of the wafer surface and is prone to the common problem of slanted discs during polishing. Summary of the Invention

[0006] The purpose of this invention is to reduce the cost of producing large-size sapphire substrates and other large-size window wafers while ensuring processing quality, and at the same time improve processing efficiency.

[0007] To achieve the above objectives, the present invention provides a method for preparing sapphire wafers, the method comprising the following steps:

[0008] (1) The sapphire raw material wafer is brought into first contact with the resin copper disk I on the polishing machine, so that the raw material wafer is thinned to obtain an intermediate wafer;

[0009] (2) The unpolished surface of the intermediate wafer is brought into a second contact with the resin copper disk II on the polishing machine to thin the intermediate wafer and obtain the sapphire wafer;

[0010] The resin copper disk is prepared from raw materials containing the following components: based on the total weight of the resin copper disk, 25-30 wt% resin binder, 64-69 wt% copper powder, 3-8 wt% artificial diamond, 0.8-1 wt% curing agent, and 2-3 wt% filler.

[0011] The average grain size of the synthetic diamond is less than 6 μm;

[0012] The average size of the synthetic diamonds in resin copper disk I and resin copper disk II are different.

[0013] Preferably, in the resin copper disk I, the mass of synthetic diamonds with an average particle size of 3.5-4 μm accounts for more than 90 wt% of the total mass of synthetic diamonds; and in the resin copper disk II, the mass of synthetic diamonds with an average particle size of 5.5-6 μm accounts for more than 90 wt% of the total mass of synthetic diamonds.

[0014] Preferably, the resin binder is an epoxy resin and a polyurethane adhesive in a mass ratio of 1:0.2-0.3.

[0015] Preferably, the average particle size of the copper powder is 75-120 μm.

[0016] Preferably, the curing agent is selected from at least one of aliphatic amine curing agents, aromatic amine curing agents, and amide amine curing agents.

[0017] Preferably, the filler is selected from at least one of talc powder and aluminum powder.

[0018] Preferably, the conditions for the first contact include: a pressure of 0.4-1 kgf / cm². 2 .

[0019] Preferably, the conditions for the second contact include: a pressure of 0.4-1 kgf / cm². 2 .

[0020] Preferably, during the first and second contact processes, the rotation speed of the copper disc on the polishing machine is controlled independently to be 30-50 rpm.

[0021] Preferably, the amount of material removed from the wafer by the first contact is 75-85 μm.

[0022] Preferably, the amount of material removed from the intermediate wafer by the second contact is 75-85 μm.

[0023] Preferably, the method further includes: before making the first contact, first attaching the back side of the sapphire raw material wafer to a ceramic disk using a wax-coating process, and then placing the ceramic disk with the raw material wafer attached facing down on the resin copper disk I of the polishing machine, so that the raw material wafer and the resin copper disk I can make the first contact.

[0024] Preferably, the method further includes: sequentially dewaxing, cleaning, and soft polishing the wafer obtained after the second contact to obtain a sapphire wafer.

[0025] A second aspect of the present invention provides a sapphire wafer prepared by the method described in the first aspect.

[0026] This invention utilizes a specific resin-copper disk for sapphire wafer fabrication, optimizing the sapphire processing steps while ensuring quality. It eliminates the need for continuous diamond spraying during the copper polishing process in traditional methods. Furthermore, it eliminates double-sided grinding, employing a double copper polishing method to increase the processing speed of sapphire wafers and reduce processing costs. Simultaneously, this method achieves micron-level reductions in total thickness variation (TTV) and local flatness (LTV) on the wafer surface. Detailed Implementation

[0027] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] As previously described, a first aspect of the present invention provides a method for preparing a sapphire wafer, the method comprising the following steps:

[0029] (1) The sapphire raw material wafer is brought into first contact with the resin copper disk I on the polishing machine, so that the raw material wafer is thinned to obtain an intermediate wafer;

[0030] (2) The unpolished surface of the intermediate wafer is brought into a second contact with the resin copper disk II on the polishing machine to thin the intermediate wafer and obtain the sapphire wafer;

[0031] The resin copper disk is prepared from raw materials containing the following components: based on the total weight of the resin copper disk, 25-30 wt% resin binder, 64-69 wt% copper powder, 3-8 wt% artificial diamond, 0.8-1 wt% curing agent, and 2-3 wt% filler.

[0032] The average grain size of the synthetic diamond is less than 6 μm;

[0033] The average size of the synthetic diamonds in resin copper disk I and resin copper disk II are different.

[0034] Preferably, in the resin copper disk I, the mass of synthetic diamonds with an average particle size of 3.5-4 μm accounts for more than 90 wt% of the total mass of synthetic diamonds; and in the resin copper disk II, the mass of synthetic diamonds with an average particle size of 5.5-6 μm accounts for more than 90 wt% of the total mass of synthetic diamonds. Under these preferred conditions, the inventors of the present invention have discovered that, while ensuring the processing quality of the front and back sides of the sapphire substrate wafer, the obtained resin copper disk has a higher removal rate, higher processing efficiency, longer service life, and can better reduce the cost of sapphire.

[0035] Preferably, the synthetic diamond is synthetic diamond powder.

[0036] Preferably, the resin copper disk is prepared from raw materials containing the following components: 25-27 wt% resin binder, 64-66 wt% copper powder, 6-8 wt% synthetic diamond, 0.8-1 wt% curing agent, and 2-3 wt% filler, based on the total weight of the resin copper disk. The inventors have found that the resin copper disk obtained under this preferred condition has a higher removal rate, which can better reduce the cost of sapphire.

[0037] In a preferred embodiment, the resin binder is an epoxy resin and a polyurethane adhesive in a mass ratio of 1:0.2-0.3.

[0038] Preferably, the average particle size of the copper powder is 75-120 μm.

[0039] Preferably, the curing agent is selected from at least one of aliphatic amine curing agents, aromatic amine curing agents, and amide amine curing agents. More preferably, the curing agent is selected from 3-dimethylaminopropylamine.

[0040] Preferably, the filler is selected from at least one of talc powder and aluminum powder.

[0041] More preferably, the filler is talc powder and aluminum powder, and the mass ratio of talc powder to aluminum powder is 1:1.8-2.2. Under these preferred conditions, the resin copper disc has higher density, longer service life, and better durability.

[0042] In a preferred embodiment, the conditions for the first contact include: a pressure of 0.4-1 kgf / cm². 2 .

[0043] Preferably, the conditions for the second contact include: a pressure of 0.4-1 kgf / cm². 2 .

[0044] In a preferred embodiment, during the first and second contact processes, the rotation speed of the copper disc on the polishing machine is controlled independently to be 30-50 rpm.

[0045] Preferably, the amount of material removed from the wafer by the first contact is 75-85 μm.

[0046] In a preferred embodiment, the amount of material removed from the intermediate wafer by the second contact is 75-85 μm.

[0047] Preferably, the method further includes: before making the first contact, first attaching the back side of the sapphire raw material wafer to a ceramic disk using a wax-coating process, and then placing the ceramic disk with the raw material wafer attached facing down on the resin copper disk I of the polishing machine, so that the raw material wafer and the resin copper disk I can make the first contact.

[0048] The present invention does not impose any particular limitation on the wax application process, and those skilled in the art can perform it according to known wax application techniques.

[0049] Preferably, the method further includes: before making the second contact, removing the intermediate wafer from the ceramic disk and washing off the wax layer on the intermediate wafer; then applying the polished surface of the intermediate wafer (i.e. the side of the raw material wafer that has made the first contact) to the ceramic disk using a wax-applying process; and then placing the ceramic disk with the intermediate wafer attached face down on the resin copper disk II of the polishing machine, so that the unpolished surface of the intermediate wafer and the resin copper disk II can make the second contact.

[0050] In a preferred embodiment, the method further includes: sequentially dewaxing, cleaning, and soft polishing the wafer obtained after the second contact to obtain a sapphire wafer.

[0051] The present invention does not impose any particular limitation on the methods of dewaxing, cleaning, and soft polishing, and those skilled in the art can perform these methods according to known techniques.

[0052] The resin copper disk I and resin copper disk II described in this invention can be custom-made or prepared using methods known in the art. This invention exemplarily provides a method for preparing a resin copper disk, the method comprising:

[0053] S1: The resin binder and copper powder are mixed in a first step to obtain the base material; and

[0054] The synthetic diamond, hardener, and filler are mixed a second time to obtain the grinding aid;

[0055] S2: The base material and the grinding aid are mixed for the third time to obtain mixture I;

[0056] S3: The mixture I is injected into a mold for pressing and then cooled and shaped.

[0057] It should be noted that the definitions and dosages of the resin binder, copper powder, artificial diamond, curing agent, and filler described in this invention are the same as the definitions and contents of the corresponding components described in the first aspect, and will not be repeated here. Those skilled in the art should not understand this as a limitation of the invention.

[0058] According to a preferred embodiment, the conditions for the first mixing include: a stirring speed of 500-800 rpm, a time of 1.5-2.5 h, and a vibration frequency of 10-20 Hz.

[0059] According to another preferred embodiment, the conditions for the second mixing include: a stirring speed of 300-600 rpm and a time of 30-60 min.

[0060] Preferably, the specific operation of the third mixing includes: dividing the base material into three equal parts and the grinding aid into three equal parts; adding one part of the base material and one part of the grinding aid to each vibrating barrel for mixing; then pouring the base material and grinding aid mixed in the three vibrating barrels into the same vibrating barrel and continuing to mix and stir for 1-2 hours to obtain mixture I;

[0061] The mixing speed is 800-1000 rpm, the vibration time is 0.5-1 h, and the vibration frequency is 15-30 Hz.

[0062] The present invention does not impose any particular limitation on the conditions of the third mixing, as long as the base material and the grinding aid are mixed evenly, those skilled in the art can make the selection as needed.

[0063] In a preferred embodiment, the pressing conditions include: a temperature of 150-160°C and a time of 90-120 minutes.

[0064] Preferably, the cooling and molding time is 8-12 hours.

[0065] A second aspect of the present invention provides a sapphire wafer prepared by the method described in the first aspect.

[0066] Compared with traditional sapphire wafer processing procedures, the method of the present invention has the following advantages:

[0067] (1) The method of the present invention does not require a double-sided grinding process during the copper polishing (i.e., the first contact and the second contact) process, and does not require the spraying of diamond liquid, thus avoiding the problem of uneven distribution of diamond polishing liquid causing slant plate; the method can achieve the quality of the original process or even better.

[0068] (2) In traditional processes, the roughness of the wafer is determined by grinding, while the method of the present invention can achieve the required roughness of the wafer by controlling the particle size of the artificial diamond in the resin copper disk.

[0069] (3) Since the copper polishing rate is higher than the grinding rate, the processing time of the method of the present invention is shorter than that of the conventional method; moreover, the boron carbide used in the grinding of the conventional method is expensive, and its total processing cost is higher than that of the present invention when the wafer removal amount is the same.

[0070] The present invention will be described in detail below through examples. Unless otherwise specified, the instruments, reagents, and materials involved in the following examples are all conventional instruments, reagents, and materials already existing in the prior art and can be obtained through legitimate commercial channels. Unless otherwise specified, the experimental methods and detection methods involved in the following examples are all conventional experimental methods and detection methods already existing in the prior art.

[0071] The main materials used in the examples and comparative examples are all commercially available, as detailed below.

[0072] Epoxy resin: Grade E-44, purchased from Henan Huineng Resin Co., Ltd.;

[0073] Polyurethane adhesive: Product No. Changming 019, purchased from Langfang Puming Chemical Technology Co., Ltd.;

[0074] Copper powder: average particle size 100μm, purchased from Nangong Ruili Alloy Welding Materials Co., Ltd.

[0075] Curing agent: 3-Dimethylaminopropylamine, purchased from Jiangsu Runfeng Synthetic Technology Co., Ltd.;

[0076] Filler:

[0077] Talc powder: average particle size 120μm, purchased from Lingshou County Junkai New Material Co., Ltd.;

[0078] Aluminum powder: average particle size 120μm, purchased from Lingshou County Junkai New Material Co., Ltd.

[0079] Synthetic diamonds:

[0080] Synthetic Diamond I: Synthetic diamond powder with an average particle size of 3.5 μm, purchased from Dongguan Chuangli Abrasive Technology Co., Ltd.

[0081] Synthetic Diamond II: Synthetic diamond powder with an average particle size of 6.0 μm, purchased from Dongguan Chuangli Abrasive Technology Co., Ltd.

[0082] Preparation Example 1

[0083] In this preparation example, resin copper disk A1 was prepared according to the formulation in Table 1:

[0084] Table 1

[0085]

[0086] Preparation method of resin copper disk:

[0087] S1: The resin binder and copper powder are first mixed in a vibrating drum to obtain a base material; and the synthetic diamond, curing agent, and filler are second mixed to obtain a grinding aid; wherein...

[0088] The conditions for the first mixing were: stirring speed of 800 rpm, time of 2 hours, and vibration frequency of 15 Hz.

[0089] The conditions for the second mixing are: stirring speed of 500 rpm and time of 60 min;

[0090] S2: Divide the base material into three equal parts and the grinding aid into three equal parts; add one part of the base material and one part of the grinding aid to each vibrating barrel for mixing, then pour the base material and grinding aid mixed in the three vibrating barrels into the same vibrating barrel, and continue mixing and stirring for 2 hours to obtain mixture I;

[0091] The mixing speed of the mixture is 800 rpm, the vibration time is 1 hour, and the vibration frequency is 30 Hz.

[0092] S3: The mixture I is injected into a mold for pressing, and then cooled and shaped for 10 hours to obtain the resin copper disk A1;

[0093] The pressing conditions include a temperature of 150℃ and a time of 120 minutes.

[0094] Preparation Example 2

[0095] In this preparation example, the resin copper disk A2 was prepared according to the formulation of Preparation Example 1, except that the particle size of the artificial diamonds was different; the specific formulation is shown in Table 2.

[0096]

[0097] Preparation Example 3

[0098] In this preparation example, resin copper disk A3 was prepared according to the formulation in Table 3:

[0099] Table 3

[0100]

[0101] Preparation method of resin copper disk:

[0102] S1: The resin binder and copper powder are first mixed in a vibrating drum to obtain a base material; and the synthetic diamond, curing agent, and filler are second mixed to obtain a grinding aid; wherein...

[0103] The conditions for the first mixing were: stirring speed of 500 rpm, time of 2.5 h, and vibration frequency of 20 Hz.

[0104] The conditions for the second mixing are: stirring speed of 400 rpm and time of 60 min;

[0105] S2: Divide the base material into three equal parts and the grinding aid into three equal parts; add one part of the base material and one part of the grinding aid to each vibrating barrel for mixing, then pour the base material and grinding aid mixed in the three vibrating barrels into the same vibrating barrel, and continue mixing and stirring for 2 hours to obtain mixture I;

[0106] The mixing speed of the mixture is 800 rpm, the vibration time is 1 hour, and the vibration frequency is 30 Hz.

[0107] S3: The mixture I is injected into a mold for pressing, and then cooled and shaped for 10 hours to obtain the resin copper disk II;

[0108] The pressing conditions include a temperature of 160℃ and a time of 90 minutes.

[0109] Preparation Example 4

[0110] In this preparation example, the resin copper disk A4 was prepared using a method similar to that in Preparation Example 3, except that the particle size of the synthetic diamonds was different; the specific formulation is shown in Table 4.

[0111] Table 4

[0112]

[0113] Preparation Example 5

[0114] This preparation example uses a similar method to Preparation Example 3 to prepare the resin copper disk A5, except that the particle size of the artificial diamonds is different; the specific formula is shown in Table 5.

[0115] Table 5

[0116]

[0117]

[0118] The resin copper disks A1 and A3 prepared in the above preparation example are used as resin copper disk I; resin copper disks A2, A4 and A5 are used as resin copper disk II, and are used to prepare sapphire wafers in subsequent embodiments.

[0119] Example 1

[0120] A method for preparing sapphire wafers, the method comprising the following steps:

[0121] (1) Four 6-inch sapphire raw material wafers (1390mm thick) are attached to a ceramic disk by a waxing process. The ceramic disk with the raw material wafers attached is placed face down on the resin copper disk I of the polishing machine. The sapphire raw material wafers make the first contact with the resin copper disk I on the polishing machine, so that the wafers are thinned to obtain an intermediate wafer.

[0122] The conditions for the first contact were: a pressure of 0.6 kgf / cm². 2 The rotation speed of the copper disk on the polishing machine is controlled at 40 rpm; the removal amount of the first contact on the wafer is 80 μm; the resin copper disk I is resin copper disk A1;

[0123] (2) Remove the intermediate wafer from the ceramic disk and wash off the wax layer on the intermediate wafer; then apply the polished surface of the intermediate wafer (that is, the side of the raw material wafer that has made the first contact) to the ceramic disk through the wax application process, and then place the ceramic disk with the intermediate wafer attached face down on the resin copper disk II of the polishing machine, so that the unpolished surface of the intermediate wafer makes a second contact with the resin copper disk II on the polishing machine, thereby thinning the intermediate wafer.

[0124] The conditions for the second contact are: pressure of 0.6 kgf / cm². 2 The rotation speed of the copper disk on the polishing machine is controlled at 40 rpm; the removal amount of the intermediate wafer by the second contact is 80 μm; the resin copper disk II is resin copper disk A2;

[0125] (3) The wafer obtained after the second contact is dewaxed, cleaned and soft polished in sequence to obtain a sapphire wafer.

[0126] Example 2

[0127] A method for preparing sapphire wafers, the method comprising the following steps:

[0128] (1) Four 6-inch sapphire raw material wafers (1390mm thick) are attached to a ceramic disk by a waxing process. The ceramic disk with the raw material wafers attached is placed face down on the resin copper disk I of the polishing machine. The sapphire raw material wafers make the first contact with the resin copper disk I on the polishing machine, so that the wafers are thinned to obtain an intermediate wafer.

[0129] The conditions for the first contact were: a pressure of 0.6 kgf / cm². 2 The rotation speed of the copper disk on the polishing machine is controlled at 40 rpm; the removal amount of the first contact on the wafer is 80 μm; the resin copper disk I is resin copper disk A3;

[0130] (2) Remove the intermediate wafer from the ceramic disk and wash off the wax layer on the intermediate wafer; then apply the polished surface of the intermediate wafer (that is, the side of the raw material wafer that has made the first contact) to the ceramic disk through the wax application process, and then place the ceramic disk with the intermediate wafer attached face down on the resin copper disk II of the polishing machine, so that the unpolished surface of the intermediate wafer makes a second contact with the resin copper disk II on the polishing machine, thereby thinning the intermediate wafer.

[0131] The conditions for the second contact are: pressure of 0.6 kgf / cm². 2 The rotation speed of the copper disk on the polishing machine is controlled at 40 rpm; the removal amount of the intermediate wafer by the second contact is 80 μm; the resin copper disk II is resin copper disk A4;

[0132] (3) The wafer obtained after the second contact is dewaxed, cleaned and soft polished in sequence to obtain a sapphire wafer.

[0133] Example 3

[0134] This embodiment uses a method similar to that of embodiment 1, except that in step (2), the resin copper disk A2 on the polishing machine is replaced with resin copper disk A5;

[0135] The remaining steps are the same as in Example 1.

[0136] Example 4

[0137] This comparative example was carried out using a method similar to that of Example 1, except that resin copper disk I was resin copper disk A3, and resin copper disk II was resin copper disk A2.

[0138] The remaining steps are the same as in Example 1.

[0139] Example 5

[0140] This comparative example was carried out using a method similar to that of Example 1, except that resin copper disk I was resin copper disk A1 and resin copper disk II was resin copper disk A4.

[0141] The remaining steps are the same as in Example 1.

[0142] Comparative Example 1

[0143] This comparative example is carried out using a method similar to that of Example 1. The difference is that when making the first contact and the second contact in this comparative example, the resin copper disk I and the resin copper disk II used are both resin copper disk A1.

[0144] The remaining steps are the same as in Example 1.

[0145] Comparative Example 2

[0146] This comparative example was carried out in a similar manner to Example 1. The difference is that when the first contact and the second contact were carried out in this comparative example, both the resin copper disc I and the resin copper disc II used were resin copper disc A2;

[0147] The remaining steps were the same as those in Example 1.

[0148] Test example

[0149] The TTV and LTV values of the sapphire wafers prepared in the above examples and comparative examples were tested using an FRT wafer full inspection instrument. The specific test results are shown in Table 6;

[0150] The standard for a qualified product is TTV ≤ 3μm, LTV ≤ 1.5μm, and the back roughness is 1 - 1.15μm; other cases are regarded as unqualified.

[0151] To avoid the randomness of product yield, each group of experiments was repeated 10 times, and a total of 40 sapphire wafers were prepared. Then, the product yield was calculated according to the formula: product yield = number of qualified wafers / total number of wafers × 100%.

[0152] Table 6

[0153]

[0154] Compared with the original process, the cost difference of the method provided by the present invention mainly lies in the copper polishing and grinding processes. The consumable cost of a single 6-inch wafer in the original process: the grinding cost is 6.5 yuan per wafer; the copper polishing cost is 3.9 yuan per wafer.

[0155] The cost of a single resin copper polishing disc provided by the present invention is about 39,000 yuan; one resin copper disc can process about 13,000 wafers; therefore, the consumable cost of a single 6-inch wafer is about 6.0 yuan. Compared with the original process, the method provided by the present invention saves 42% in consumable cost when preparing 6-inch wafers.

[0156] The existing grinding removal rate is 0.9μm / min; the grinding removal amount of a 6-inch wafer is about 130μm, and the processing time is about 144 min; the copper polishing removal amount is 50μm, the removal rate is about 1.3μm / min, and the processing time is about 38 min; the total processing time of grinding and copper polishing requires 182 min. However, using the resin copper disc provided by the present invention can reduce the processing time of producing large-size sapphire substrates and other large-size window wafers while ensuring the processing quality, and at the same time reduce the processing cost. Moreover, the total thickness variation (TTV) and local flatness (LTV) of the processed sapphire wafers can both reach the micron level and meet the customer's requirements.

[0157] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing sapphire wafers, characterized in that, The method includes the following steps: (1) The sapphire raw material wafer is brought into first contact with the resin copper disk I on the polishing machine to thin the raw material wafer and obtain an intermediate wafer; (2) The unpolished surface of the intermediate wafer is brought into a second contact with the resin copper disk II on the polishing machine to thin the intermediate wafer and obtain the sapphire wafer; The resin copper disk is prepared from raw materials containing the following components: based on the total weight of the resin copper disk, 25-30 wt% resin binder, 64-69 wt% copper powder, 3-8 wt% artificial diamond, 0.8-1 wt% curing agent, and 2-3 wt% filler. The average grain size of the synthetic diamond is less than 6 μm; The average grain size of the synthetic diamonds in resin copper disk I and resin copper disk II are different. In the resin copper disk I, the mass of synthetic diamonds with an average particle size of 3.5-4 μm accounts for more than 90 wt% of the total mass of synthetic diamonds; in the resin copper disk II, the mass of synthetic diamonds with an average particle size of 5.5-6 μm accounts for more than 90 wt% of the total mass of synthetic diamonds.

2. The method according to claim 1, characterized in that, The resin binder is an epoxy resin and a polyurethane adhesive in a mass ratio of 1:0.2-0.3; and / or The average particle size of the copper powder is 75-120 μm.

3. The method according to claim 1 or 2, characterized in that, The curing agent is selected from at least one of aliphatic amine curing agents, aromatic amine curing agents, and amide amine curing agents; and / or The filler is selected from at least one of talc powder and aluminum powder.

4. The method according to claim 1 or 2, characterized in that, The conditions for the first contact include: a pressure of 0.4-1 kgf / cm². 2 ; The conditions for the second contact include: a pressure of 0.4-1 kgf / cm². 2 .

5. The method according to claim 1 or 2, characterized in that, During the first and second contact processes, the rotation speed of the copper disc on the polishing machine is independently controlled to 30-50 rpm.

6. The method according to claim 1 or 2, characterized in that, The first contact removes 75-85 μm of material from the wafer; and / or The second contact removes 75-85 μm of the intermediate wafer.

7. The method according to claim 1 or 2, characterized in that, The method further includes: before making the first contact, first attaching the back of the sapphire raw material wafer to a ceramic disk using a wax-coating process, and then placing the ceramic disk with the raw material wafer attached facing down on the resin copper disk I of the polishing machine, so that the raw material wafer and the resin copper disk I can make the first contact.

8. The method according to claim 1 or 2, characterized in that, The method also includes: sequentially dewaxing, cleaning, and soft polishing the wafer obtained after the second contact to obtain a sapphire wafer.

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