JP2022068748A - Oxide single-crystal wafer, wafer for composite substrate, composite substrate, method for processing oxide single-crystal wafer, method for producing oxide single-crystal wafer, method for producing wafer for composite substrate, and method for producing composite substrate - Google Patents

Abstract

To provide an oxide single-crystal wafer, a wafer for composite substrate, a composite substrate, a method for processing an oxide single-crystal wafer, a method for producing an oxide single-crystal wafer, a method for producing a wafer for composite substrate, and a method for producing composite substrate, making it possible to improve the yield of lamination with a support substrate.SOLUTION: An oxide single-crystal wafer has a front face and a back face. The front face and the back face are subjected to the same wrapping processing. The oxide single-crystal wafer has a warpage of 20.5 μm or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for processing an oxide single crystal wafer, a wafer for a composite substrate, a composite substrate, a method for processing an oxide single crystal wafer, a method for manufacturing an oxide single crystal wafer, a method for manufacturing a wafer for a composite substrate, and a method for manufacturing a composite substrate. .. For example, the present invention relates to a piezoelectric oxide single crystal wafer, and more particularly to a lithium tantalate single crystal wafer and a lithium niobate single crystal wafer.

Examples of the oxide single crystal wafer include a lithium tantalate (LT) single crystal and a lithium niobate (LN) single crystal, and these oxides have melting points of about 1650 ° C and about 1255 ° C, respectively, and are curly. The points are about 600 ° C. and about 1200 ° C., respectively, and they are ferroelectrics and have piezoelectricity. LT single crystal wafers and LN single crystal wafers manufactured using these LT single crystals or LN single crystals are used for elastic surface wave (SAW) filters for removing signal noise of mobile phones, filters for televisions, optical elements, and the like. It is mainly used as a device material. One of the single crystal wafers is selected depending on the characteristics required by the device.

Next, an example of the manufacturing process of the LT single crystal wafer and the LN single crystal wafer will be described. Since these single crystals can be manufactured by the same process both crystallographically and in terms of the manufacturing process. , The manufacturing process of the LT single crystal wafer will be mainly described.

The LT single crystal is grown in an ingot state by a single crystal growth method such as the Czochralski method (CZ method) (LN / LT single crystal growth). Next, in the state of the ingot, after cutting the end portion of the single crystal having a short diameter, the ingot of the LT single crystal is subjected to a single polarization treatment (polling). This polling process polarizes the LT single crystal by applying a voltage in the <001> axial direction of the LT single crystal at a temperature equal to or higher than the Curie point.

Next, a circumferential grinding process is performed in which an orientation flat (OF), which is a reference surface for manufacturing a surface acoustic wave element or the like, that is, a surface indicating a crystal orientation or a surface acoustic wave propagation direction, is processed to adjust the outer diameter. , LT single crystal ingot. After performing these processes, the LT single crystal is sliced into a disk-shaped wafer having a predetermined thickness along a desired crystal orientation by a cutting device such as a wire saw (wire saw cutting).

The obtained LT single crystal wafer is further processed as follows. First, the outer periphery of the LT single crystal wafer is chamfered by beveling using a diamond grindstone of about # 600 to # 1000 to prevent cracking in the subsequent process and to determine the diameter of the LT single crystal wafer. Mold to the size of.

In the case of an LT single crystal wafer for an elastic surface wave filter, a single-sided lapping process or a blast process using # 240 to # 2500 slurry abrasive grains further causes differences in spurious characteristics depending on the purpose. The back surface of the crystal wafer is roughened as necessary to reduce bulk spurious. Then, as a finish, the surface corresponding to the opposite side of the roughened surface is mirror-polished by mechanochemical polishing using a slurry such as colloidal silica.

On the other hand, in the case of optical element applications, roughening is not necessary, and after wrapping both sides of an LT single crystal wafer, both sides are often mirror-polished by mechanochemical polishing using a slurry such as colloidal silica. ..

The LT single crystal wafer thus obtained is usually in the shape of a disk having a diameter of 3 inches to 6 inches (76.2 mm to 152.4 mm) and a thickness of about 0.1 mm to 0.5 mm. For example, when obtaining an elastic surface wave filter, the LT single crystal wafer is separated into a large number by dicing to form LT single crystal pieces, and an excitation electrode composed of a pair of comb-shaped electrodes intersecting each other is provided on the mirror-polished surface side thereof. It will be provided.

In particular, cracks in LT single crystal wafers and LN single crystal wafers may be caused by warpage of these single crystal wafers. Conventionally, since warpage occurs in these single crystal wafers after a single-sided wrapping step or a single-sided mirror polishing step, countermeasures against such warpage have been taken. For example, in Patent Document 1, after a single-sided wrapping step for roughening the back surface, a 60 mmφ wafer in which a warp of about 80 μm to 120 μm is generated by this step is prepared by mixing hydrofluoric acid and nitric acid at a volume ratio of 1: 2. It is described that the single crystal wafer is put into a mixed mixed acid, heated to about 60 ° C. to 120 ° C., held for 1 hour, and then etched (hydrofluoric acid etching) to the single crystal wafer to make the warp about 15 μm. ..

The warp caused by such a single-sided lapping process or a single-sided mirror polishing process is generally known as the Twiman effect. The Twiman effect is a phenomenon in which a wafer is warped so as to compensate for the difference in residual stress on both sides after processing the wafer. That is, in LT single crystal wafers and LN single crystal wafers, there is a difference in surface roughness or processing distortion between the front surface (main surface) and the back surface of the wafer due to processing such as single-sided lapping treatment and single-sided mirror polishing treatment. When it occurs, the entire wafer is deformed so as to form a convex shape when viewed from a surface having a large surface surface and a large roughness or a surface having a large processing strain.

Special Publication No. 56-36808

When LN single crystal wafers and LT single crystal wafers are used for surface elastic wave filters, these single crystal wafers and support substrates may be bonded together, and the rough surface of these single crystal wafers may be bonded when the support substrates are bonded together. For example, it is necessary to form a film of SiO ₂ or the like on the side (back surface side). The rough surface side of the LN single crystal wafer and the LT single crystal wafer obtained by the above-mentioned conventional manufacturing process is warped convexly due to the above-mentioned Twiman effect. Therefore, when a film formation of SiO ₂ or the like is applied to the rough surface side, the rough surface side is further convexly warped, and it becomes difficult to bond the film formation surface of SiO ₂ or the like and the support substrate after that, and the support substrates are bonded together. There is a risk that the yield of the single crystal wafer will decrease.

The present invention has been proposed in view of such circumstances, and can improve the yield of bonding with a support substrate, such as an oxide single crystal wafer, a composite substrate wafer, a composite substrate, and an oxide single crystal. It is an object of the present invention to provide a method for processing a wafer, a method for manufacturing an oxide single crystal wafer, a method for manufacturing a wafer for a composite substrate, and a method for manufacturing a composite substrate.

In order to solve the above problems, the oxide single crystal wafer of the present invention is an oxide single crystal wafer provided with a front surface and a back surface, and the front surface and the back surface are both wrapped in the same manner. It is a treated surface, and the warp of the oxide single crystal wafer is 20.5 μm or less.

Further, in order to solve the above problems, the oxide single crystal wafer of the present invention is an oxide single crystal wafer having a front surface and a back surface, and the oxide single crystal wafer is the front surface. All of the back surfaces are wafers that have been subjected to the same wrapping treatment and then etched, and the warpage of the oxide single crystal wafer is 20.5 μm or less.

The oxide single crystal wafer may be a lithium tantalate single crystal wafer or a lithium niobate single crystal wafer.

Further, in order to solve the above problems, the wafer for a composite substrate of the present invention includes the oxide single crystal wafer of the present invention and a silicon oxide film formed on the back surface of the oxide single crystal wafer. ..

Further, in order to solve the above problems, the composite substrate of the present invention includes the wafer for the composite substrate of the present invention and a support substrate bonded to the silicon oxide film.

The support substrate may be a silicon substrate, a sapphire substrate, or a spinel substrate.

Further, in order to solve the above-mentioned problems, the method for processing an oxide single crystal wafer of the present invention is a method for processing an oxide single crystal wafer for obtaining the above-mentioned oxide single crystal wafer of the present invention. It is a processing method that includes a wrapping process for wrapping the front and back surfaces of an oxide single crystal wafer cut out from a crystal ingot with a wire saw, and does not perform etching, surface grinding, or chemical mechanical polishing. ..

Further, in order to solve the above-mentioned problems, the method for processing an oxide single crystal wafer of the present invention is a method for processing an oxide single crystal wafer for obtaining the above-mentioned oxide single crystal wafer of the present invention. A processing method that includes an etching process that etches an oxide single crystal wafer whose front surface and back surface are wrapped after being cut out from a crystal ingot with a wire saw, and does not perform surface grinding or chemical mechanical polishing. Is.

Further, in order to solve the above-mentioned problems, the method for producing an oxide single crystal wafer of the present invention is the above-mentioned method for producing an oxide single crystal wafer of the present invention, in which an oxide is formed from an oxide single crystal ingot with a wire saw. It is a manufacturing method including a cutting step of cutting out a single crystal wafer and a wrapping step of wrapping the front surface and the back surface of the cut out oxide single crystal wafer without performing surface grinding and chemical mechanical polishing.

The method for producing an oxide single crystal wafer of the present invention may include an etching step of etching the oxide single crystal wafer after the wrapping step.

The method for producing an oxide single crystal wafer of the present invention includes a growing step of growing the ingot of the oxide single crystal and a surfaced cylindrical processing step of performing the surfaced cylindrical processing of the ingot before the cutting step. , May be included.

Further, in order to solve the above problems, the method for manufacturing a wafer for a composite substrate of the present invention is the method for manufacturing a wafer for a composite substrate of the present invention, and silicon is formed on the back surface of the oxide single crystal wafer of the present invention. A film forming step for forming an oxide film is provided.

Further, in order to solve the above problems, the method for manufacturing a composite substrate of the present invention is the method for manufacturing a composite substrate of the present invention, wherein the silicon oxide film of the wafer for the composite substrate of the present invention and the support substrate are used. Includes a bonding process.

According to the present invention, an oxide single crystal wafer, a wafer for a composite substrate, a composite substrate, a processing method for an oxide single crystal wafer, and a production of an oxide single crystal wafer capable of improving the yield of bonding with a support substrate can be obtained. A method, a method for manufacturing a wafer for a composite substrate, and a method for manufacturing a composite substrate can be provided.

FIG. 1 is a schematic view of an oxide single crystal wafer 100 according to an embodiment of the present invention. FIG. 2 is a flow chart showing a manufacturing flow from the growth of the LN single crystal or the LT single crystal to the etching process.

The present inventor repeated diligent studies on the warp of the wafer in the manufacturing process of the oxide single crystal wafer, and reexamined the property of the warp of the wafer cut out from the ingot of the oxide single crystal. As a result, the front surface and the back surface of the oxide single crystal wafer cut out from the oxide single crystal ingot with a wire saw are wrapped to alleviate the warped state of the wafer, and then after the wrapping process. By forming a silicon oxide film (SiO ₂ film) on the back surface without performing surface grinding and chemical mechanical polishing on the front surface and back surface, a silicon oxide film is formed for a composite substrate after film formation. The present invention has been completed based on the finding that the warpage of the wafer can be alleviated and the yield of bonding with the support substrate can be improved.

That is, when the front surface and the back surface of the oxide single crystal wafer cut out with a wire saw are wrapped, the residual stress on both sides of the oxide single crystal wafer is unlikely to differ, so that the Twiman effect is obtained. It is difficult to develop and the warp of the oxide single crystal wafer becomes small. In this state, when a silicon oxide film is formed on the back surface side for bonding to the support substrate, the front surface side of the oxide single crystal wafer warps in a concave shape, but the conventional method is mainly used. The warped state of the oxide single crystal wafer is clearly alleviated as compared with the case where the silicon oxide film is formed on the back surface side of the oxide single crystal wafer mirror-processed only on the front surface side. As a result, the yield of bonding with the support substrate can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view of an oxide single crystal wafer 100 according to an embodiment of the present invention. Further, FIG. 2 is a flow chart showing the flow of production from the growth of the LN single crystal or the LT single crystal to the etching step in the present invention. However, the present invention is not limited to the following embodiments.

[Oxide single crystal wafer A]
FIG. 1A is a front view of the oxide single crystal wafer 100 as viewed from the front surface, and includes an orientation flat 130. The oxide single crystal wafer 100 has, for example, a disk shape having a diameter of 3 inches to 8 inches (76.2 mm to 203.2 mm) and a thickness of about 0.1 mm to 0.5 mm, and is mainly a main surface. It has a front surface and a back surface that is the opposite of the front surface.

FIG. 1B is a side view of the oxide single crystal wafer 100, in which the upper surface is a front surface 110 and the lower surface is a back surface 120. In the oxide single crystal wafer 100, the front surface 110 is curved in a convex shape and the back surface 120 is curved in a concave shape. However, in the oxide single crystal wafer 100 of the present invention, the front surface 110 may be curved in a concave shape and the back surface 120 may be curved in a convex shape.

However, the warp w of the oxide single crystal wafer 100 is 20.5 μm or less. The warp w of the oxide single crystal wafer 100 indicates the warp value in the portion having the largest warp, for example, in the thickness direction of the top portion 120a and the edge portion 120b in the portion having the largest warp of the back surface 120. The distance. When a silicon oxide (SiO ₂ ) or the like is formed on the back surface 120, a stress is generated so that the back surface 120 becomes convex. However, when the warp w is 20.5 μm or less, the warp of the oxide single crystal wafer 100 after forming the SiO ₂ or the like can be reduced to such an extent that the bonding with the support substrate is not hindered. Therefore, the bonding with the support substrate becomes easy, and the yield of bonding with the support substrate can be improved.

If the warp w is larger than 20.5 μm, the warp w of the oxide single crystal wafer 100 after forming the SiO ₂ or the like on the back surface 120 becomes too large, and it is difficult to bond the wafer to the support substrate. Therefore, there is a possibility that the yield of bonding with the support substrate will not be improved.

[Oxide single crystal wafer B]
Further, one embodiment of the oxide single crystal wafer 100 is an oxide single crystal wafer provided with a front surface 110 and a back surface 120, and the front surface 110 and the back surface 120 are both wrapped in the same manner. Wafers that have been treated and then etched can also be mentioned. Also in this case, the warp of the oxide single crystal wafer 100 is 20.5 μm or less as described above.

The lapping process may cause processing strain on the front surface 110 and the back surface 120 of the oxide single crystal wafer 100. Oxidation in which the processing strain is removed by dissolving the surface of the wafer by the etching process. It can be a single crystal wafer 100. Further, with respect to the warp w of the oxide single crystal wafer 100, the variation between the wafers can be controlled more strictly by the etching process, and the warp w can be controlled more evenly to 20.5 μm or less.

That is, in the case of the oxide single crystal wafer B, since there is little variation in the warp w for each wafer, the film forming conditions of the silicon oxide film and the bonding conditions with the support substrate can be made almost the same, so that these operations can be performed more. It will be easier.

Specific examples of the oxide single crystal wafer 100 include a lithium tantalate single crystal wafer and a lithium niobate single crystal wafer. However, the present invention is not limited to these, and examples of the oxide single crystal wafer 100 include quartz.

[Wafer for composite board]
The wafer for a composite substrate includes an oxide single crystal wafer 100 and a silicon oxide film formed on the back surface 120 of the oxide single crystal wafer 100. By providing the silicon oxide film, the adhesion to the support substrate is improved.

[Manufacturing method of wafer for composite substrate]
The method for manufacturing the wafer for the composite substrate is not particularly limited as long as it is a method capable of forming a silicon oxide film on the back surface 120 of the oxide single crystal wafer 100. For example, as a film forming step of forming a silicon oxide film on the back surface 120 of the oxide single crystal wafer 100, a step of forming a film by chemical vapor deposition (CVD) can be included.

[Composite board]
The composite substrate includes the above-mentioned wafer for composite substrate and a support substrate bonded to the silicon oxide film of the wafer for composite substrate. As the support substrate, a silicon substrate, a sapphire substrate, or a spinel substrate can be used. However, the present invention is not limited to these substrates.

[Manufacturing method of composite substrate]
The method for manufacturing the composite substrate is not particularly limited as long as it is a method capable of bonding the silicon oxide film of the wafer for the composite substrate and the support substrate. For example, a step of laminating these with an organic adhesive can be included.

[Manufacturing method of oxide single crystal wafer]
Examples of the method for manufacturing the oxide single crystal wafer 100 include a method including the following steps shown in FIG.

<S3: Cutting process>
The cutting step is a step of cutting out the oxide single crystal wafer 100 from the oxide single crystal ingot with a wire saw. For example, a wire saw cutting device can be used to cut an ingot into a wafer shape with a wire saw to obtain a wafer having a predetermined thickness.

<S4: Wrapping process>
The wrapping step is a step of wrapping the front surface 110 and the back surface 120 of the cut out oxide single crystal wafer 100. The oxide single crystal wafer 100 cut out by the wire saw in the cutting step has waviness on the front surface 110 and the back surface 120 due to cutting, and this step is performed to remove the waviness. Can be done. Further, by this step, the thickness and the surface roughness of the oxide single crystal wafer 100 can be adjusted and flattened.

Examples of the wrapping step include a step of simultaneously polishing the front surface 110 and the back surface 120 of the oxide single crystal wafer 100 by using free abrasive grains such as a SiC slurry for polishing. Specifically, using a lapping machine, the oxide single crystal wafer 100 can be sandwiched from above and below by a surface plate, and polishing can be performed while flowing a SiC slurry.

Further, in the method for manufacturing the oxide single crystal wafer 100, the front surface 110 and the back surface 120 are not subjected to surface grinding and chemical mechanical polishing.

As a specific example of the surface grinding process, there is an example in which a single-wafer surface grinding machine is used and the front surface 110 is ground by a grinding wheel equipped with a high-count diamond grindstone. When the surface grinding process is performed, the front surface 110 is warped in a convex shape and the back surface 120 is warped in a concave shape due to the Twiman effect.

In addition, chemical mechanical polishing has conventionally been performed using a batch type CMP processing machine such as a polish machine. Dozens of wafers are attached to multiple ceramic plates, and the wafers are polished with colloidal silica and a polish pad. The front surface is mirror-finished. In the case of such batch type chemical mechanical polishing, the thickness between the wafers varies by about 5 μm to 10 μm.

When the oxide single crystal wafer 100 is LT or LN, the composite substrate to which the support substrates are bonded is further ground by about a dozen μm in order to adjust the thickness after the support substrates are bonded to each other. The front surface 110 is mirror-finished by chemical mechanical polishing, and then the comb-shaped electrode is patterned to impart a function as a SAW filter. Therefore, the front surface 110 of the oxide single crystal wafer 100 before being bonded to the support substrate does not necessarily have to be mirror-finished by chemical mechanical polishing. Therefore, even in the present invention, which is not subjected to chemical mechanical polishing. For example, the LT or LN oxide single crystal wafer 100 can be manufactured at a lower cost than the conventional method.

According to the method for producing an oxide single crystal wafer of the present invention described above, the oxide single crystal wafer 100 can be produced.

Further, the method for manufacturing the oxide single crystal wafer 100 may include the following steps shown in FIG.

<S5: Etching process>
The etching step is a step of etching the oxide single crystal wafer 100 after the wrapping step. The wrapping step may cause processing strain on the front surface 110 and the back surface 120 of the oxide single crystal wafer 100, but this processing strain can be removed by melting the surface of the wafer in this step. can. In addition, the warp of the oxide single crystal wafer 100 can be controlled.

In particular, by appropriately adjusting the mixing ratio of HF and HNO ₃ of fluorinated nitric acid, the immersion time, etc. in the etching process, the variation w of the oxide single crystal wafer 100 can be controlled more strictly for each wafer. It can be uniformly controlled to 20.5 μm or less.

That is, in the case of the oxide single crystal wafer B, since there is little variation in the warp w for each wafer, the film forming conditions of the silicon oxide film and the bonding conditions with the support substrate can be made almost the same, so that these operations can be performed more. It will be easier.

Specific examples of the etching step include a step of immersing the oxide single crystal wafer 100 in the etching solution in the draft for a long time. When the oxide single crystal wafer 100 is LT or LN, processing strain is sufficiently removed by using fluorinated nitric acid, which is a mixed acid of HF and _HNO3 , as an etching solution and immersing the oxide single crystal wafer 100 in the etching solution. can do. The mixing ratio of HF and HNO ₃ is not particularly limited, but can be, for example, HF: HNO ₃ = 1: 9 to 9: 1 in volume ratio, for example, HF: HNO ₃ = 1: 1 in volume ratio.

When the oxide single crystal wafer 100 is LT, it is preferable to immerse the oxide single crystal wafer 100 in the fluorine for 4 hours or more while keeping the nitrogen at room temperature.

When the oxide single crystal wafer 100 is LN, it is preferable to immerse the oxide single crystal wafer 100 in the fluorine for 25 minutes or more while keeping the nitrogen at room temperature.

<S1: Growth process>
The growing step is a step of growing an oxide single crystal ingot. For example, the ingot can be grown by a single crystal growing method such as the Cz method.

<S2: Surfaced cylinder processing process>
The surface cylinder processing step is a step of performing surface cylinder processing of the ingot before the cutting process. Specifically, a band saw, a cylindrical grinder, and an end face grinder can be used to orient the ingot crystals, perform cylindrical grinding, and perform orientation flat processing. By this step, the plane orientation, the diameter of the ingot, and the orientation flat can be adjusted as required.

(Other processes)
Further, the method for producing the oxide single crystal wafer 100 may include steps other than the above. For example, the ingot is heated in an electric furnace or the like in order to remove the distortion of the ingot after the growing process and prevent the ingot from cracking. Annealing process for annealing, polling process for aligning the polarization direction of single crystals by heating and energizing the ingot after annealing process, black processing process for reducing wafers, beveling process for chamfering the end face of the wafer, cleaning to clean the wafer It can include a process, an inspection process for inspecting the shape and appearance of the wafer, and the like.

[Processing method A for oxide single crystal wafer]
In order to obtain the oxide single crystal wafer 100 of the present invention, the above manufacturing method may be carried out, but as one embodiment of the present invention, for example, an oxide single crystal cut out from an oxide single crystal ingot with a wire saw. The oxide single crystal wafer 100 of the present invention can also be obtained by a processing method in which a crystal wafer 100 is obtained and a wrapping process is performed on the crystal wafer 100.

That is, it includes a lapping process in which the front surface 110 and the back surface 120 of the oxide single crystal wafer 100 cut out from the ingot of the oxide single crystal with a wire saw are lapping, and the etching process and the front surface 110 are included. The oxide single crystal wafer 100 can be obtained by a processing method in which the back surface 120 is not subjected to surface grinding and chemical mechanical polishing. Since a specific example of the wrapping process has been described in the above manufacturing method, the description thereof will be omitted here.

[Processing method B for oxide single crystal wafer]
Further, in order to obtain the oxide single crystal wafer 100 of the present invention, instead of the above-mentioned processing method A for the oxide single crystal wafer, for example, the front surface is cut out from an oxide single crystal ingot with a wire saw. The oxide single crystal wafer 100 of the present invention can also be obtained by obtaining an oxide single crystal wafer 100 having a back surface wrapping processed and performing an etching process on the oxide single crystal wafer 100.

That is, it includes an etching step of etching the oxide single crystal wafer 100 having the front surface and the back surface lapping after being cut out from the oxide single crystal ingot with a wire saw, and includes the front surface 110 and the front surface 110. The oxide single crystal wafer 100 can be obtained by a processing method in which the back surface 120 is not subjected to surface grinding and chemical mechanical polishing. Since a specific example of the etching process has been described in the above manufacturing method, the description thereof will be omitted here.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

(Example 1)
The oxide single crystal wafer 100 was cut out with a wire saw from 16 LT single crystal ingots grown by the Cz method and processed into a surface cylinder, and the oxide single crystal wafer 100 was formed by using a lapping machine. It was sandwiched between upper and lower plates and polished while flowing a SiC slurry to perform a lapping step. Next, an etching step was performed in which the oxide single crystal wafer 100 was immersed in the nitrogen for 4 hours while the nitrogen mixed at a volume ratio of HF: HNO ₃ = 1: 1 was maintained at room temperature. By these steps, a 6-inch LT wafer was manufactured.

After cleaning the obtained LT wafers, warpage w was measured using a surface roughness measuring machine Surfcom manufactured by Tosei Engineering Co., Ltd. for a total of 32 LT wafers, 2 per LT single crystal ingot. bottom. Two measurement points intersect at an angle of 45 degrees with respect to a straight line (dotted line L in FIG. 1A) from the orientation flat of the LT wafer on the front surface 110 to the opposite end through the center. On the straight lines A and B, 2 points at the end, 1 point at the center, and 2 points equidistant from the end and the center, for a total of 5 points, and a total of 10 points for the straight lines A and B. .. Table 1 shows the measurement results of the warp w.

It was confirmed that the warp w of the LT wafer of Example 1 was in the range of 2 μm to 20.5 μm, and the warp w could be controlled to an average value of about 10 μm.

(Conventional example 1)
Using a lap machine, an oxide single crystal wafer 100 cut out from 18 LT single crystal ingots grown by the Cz method in the same manner as in Example 1 and processed into a surface cylinder with a wire saw is oxidized. The single crystal wafer 100 was sandwiched from above and below with a platen, and polishing was performed while flowing a SiC slurry to perform a wrapping step. Next, an etching step was performed in which the oxide single crystal wafer 100 was immersed in the nitrogen for 4 hours while the nitrogen mixed at a volume ratio of HF: HNO ₃ = 1: 1 was maintained at room temperature. Then, using a single-wafer type surface grinder for wafers, only the front surface 110 was ground by a grinding wheel equipped with a diamond grindstone. Then, only the front surface 110 was mirror-finished by chemical mechanical polishing with a polishing machine. By these steps, a 6-inch LT wafer was manufactured.

After cleaning the obtained LT wafer, warpage w was measured for a total of 144 LT wafers, 8 per LT single crystal ingot, by surface roughness measurement manufactured by Tosei Engineering Co., Ltd. in the same manner as in Example 1. It was measured using a machine Surfcom. The measurement points were 10 points in total on the straight lines A and B as in Example 1.

The warp w of the LT wafer of the conventional example 1 was in the range of 22 μm to 49 μm, and the warp w was generated in an average value of about 33 μm.

[summary]
According to Example 1, it was confirmed that the oxide single crystal wafer 100 capable of improving the yield of bonding with the support substrate can be obtained.

In the wrapping process and the etching process in the first embodiment, the film thickness of the wafer for the composite substrate is extremely different from that of the conventional example 1 in which the front surface 110 is further subjected to surface grinding and chemical mechanical polishing. Can be made smaller. Therefore, when grinding a wafer for a composite substrate after forming a silicon oxide film, the conditions can be easily set, and the grinding time can be shortened as compared with the conventional method of performing chemical mechanical polishing. Can be done.

Further, as described above, the front surface 110 of the oxide single crystal wafer 100 before being bonded to the support substrate does not necessarily have to be mirror-finished by chemical mechanical polishing, and therefore is not subjected to chemical mechanical polishing. According to the first embodiment, the oxide single crystal wafer 100 can be manufactured at a lower cost than the conventional example 1.

In the embodiment, the LT wafer was manufactured and measured, but the LN wafer can also be manufactured by a manufacturing method suitable for the LT wafer, and a wafer having the same tendency as the LT wafer can be obtained. However, the same effect as the description in [Summary] above can be obtained.

100 Oxide single crystal wafer 110 Front surface 120 Back surface 130 Orientation flat

Claims (13)

An oxide single crystal wafer having a front surface and a back surface.
Both the front surface and the back surface are surfaces that have been subjected to the same wrapping treatment.
The warp of the oxide single crystal wafer is 20.5 μm or less.
Oxide single crystal wafer. An oxide single crystal wafer having a front surface and a back surface.
The oxide single crystal wafer is a wafer in which both the front surface and the back surface are subjected to the same wrapping treatment and then etched.
The warp of the oxide single crystal wafer is 20.5 μm or less.
Oxide single crystal wafer. The oxide single crystal wafer according to claim 1 or 2, wherein the oxide single crystal wafer is a lithium tantalate single crystal wafer or a lithium niobate single crystal wafer. The oxide single crystal wafer according to any one of claims 1 to 3 and
A silicon oxide film formed on the back surface of the oxide single crystal wafer and
A wafer for a composite substrate. The wafer for a composite substrate according to claim 4,
A support substrate bonded to the silicon oxide film and
A composite substrate. The composite substrate according to claim 5, wherein the support substrate is a silicon substrate, a sapphire substrate, or a spinel substrate. The method for processing an oxide single crystal wafer for obtaining the oxide single crystal wafer according to claim 1.
It includes a wrapping process for wrapping the front and back surfaces of an oxide single crystal wafer cut out from an oxide single crystal ingot with a wire saw.
A method for processing oxide single crystal wafers without etching, surface grinding and chemical mechanical polishing. The method for processing an oxide single crystal wafer for obtaining the oxide single crystal wafer according to claim 2.
It includes an etching step of etching an oxide single crystal wafer having a front surface and a back surface lapping after being cut out from an oxide single crystal ingot with a wire saw.
A method for processing oxide single crystal wafers without surface grinding and chemical mechanical polishing. The method for producing an oxide single crystal wafer according to any one of claims 1 to 3.
The cutting process of cutting out an oxide single crystal wafer from an oxide single crystal ingot with a wire saw,
Including a wrapping step of wrapping the front surface and the back surface of the cut out oxide single crystal wafer.
A method for manufacturing an oxide single crystal wafer without surface grinding and chemical mechanical polishing. The method for producing an oxide single crystal wafer according to claim 9, further comprising an etching step of etching the oxide single crystal wafer after the wrapping step. A growing step for growing the ingot of the oxide single crystal, and
Prior to the cutting step, a surfaced cylindrical processing step of performing the surfaced cylindrical processing of the ingot, and a surfaced cylindrical processing step.
The method for producing an oxide single crystal wafer according to claim 9 or 10. The method for manufacturing a wafer for a composite substrate according to claim 4.
A method for manufacturing a wafer for a composite substrate, comprising a film forming step of forming a silicon oxide film on the back surface of the oxide single crystal wafer according to any one of claims 1 to 3. The method for manufacturing a composite substrate according to claim 5.
A method for manufacturing a composite substrate, which comprises a bonding step of bonding the silicon oxide film of the wafer for a composite substrate according to claim 4 and the support substrate.

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