JP2022181230A - Piezoelectric single crystal substrate and method for manufacturing the same - Google Patents

Abstract

To provide a piezoelectric single crystal substrate capable of surely determining the front and rear of the piezoelectric single crystal substrate having a notch and both mirror-polished surfaces, and a method for manufacturing the same.SOLUTION: A piezoelectric single crystal substrate has a notch in a chamfered periphery. The periphery has a first notch formed in a crystal orientation direction using the center of the piezoelectric single crystal substrate as a reference and a second notch located at a position asymmetrical to the first notch, and the second notch has a surface roughness different from that of the first notch and allows visual determination.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a piezoelectric single crystal substrate and a manufacturing method thereof.

Substrates obtained from single crystals are used as various materials. For example, a lithium tantalate single crystal substrate (LT single crystal substrate) obtained from a lithium tantalate (LT) single crystal, a lithium niobate single crystal substrate (LN single crystal substrate) obtained from a lithium niobate (LN) single crystal, etc. The piezoelectric single crystal substrate (single crystal substrate) is used as a material for a surface acoustic wave element (SAW filter) for removing electrical signal noise used in mobile communication equipment.

LT single crystals and LN single crystals are mainly produced by the Czochralski method, and are usually grown in an electric furnace using a precious metal crucible with a high melting point, cooled at a predetermined cooling rate, and then removed from the electric furnace. taken out. In order to remove residual strain due to thermal stress, the grown single crystal is subjected to heat treatment under soaking near the melting point, and further poling treatment to achieve single polarization. A series of processes are performed in which the temperature is raised to a temperature, a voltage is applied to the single crystal, the temperature is lowered to a predetermined temperature below the Curie temperature while the voltage is applied, the voltage application is stopped, and the crystal is cooled to room temperature. After the poling treatment, the grown single crystal is ground on the outer surface to adjust the outer shape, and the single crystal ingot processed into a cylindrical shape is processed into a wafer-shaped single crystal substrate.

As a procedure for processing a cylindrical single crystal ingot, machining such as a cylindrical grinding process, a slicing process, a beveling process, a lapping process, and a polishing process is normally performed in order. Etching may also be performed between the lapping and polishing steps. Wafer-shaped single crystal substrates are manufactured from the single crystal ingot through the above-described machining and the like.

Conventionally, a single crystal substrate having a diameter of 150 mmφ or less has a linear portion called an orientation flat (OF) at a predetermined position on the outer circumference for identifying the crystal orientation, as shown in FIG. Further, a linear portion called an index flat (IF), which is shorter than OF, is provided for determining the front and back sides in the processing process and for determining the front and back sides of a double-sided mirror substrate.

However, in single crystal substrates with a diameter exceeding 150 mmφ, the provision of OF and IF reduces the effective area for cutting out devices from the substrate. It has been found that when a single crystal substrate provided with is processed by rotating it at high speed with a spin coater or the like in the device manufacturing process, troubles due to lack of OF or IF occur. That is, the single-crystal substrate provided with the OF and IF naturally does not have a perfect circular outer periphery, and the OF and IF are notched. When such a single crystal substrate having a notched outer periphery is rotated at high speed by a spin coater or the like, an unbalanced load is generated. Problems such as scattering occur.

Therefore, instead of the single crystal substrate shown in FIG. 9 having OF and IF, a single crystal substrate shown in FIG. 10 having a V-shaped notch was developed. This single crystal substrate is provided with a notch formed by cutting at one end of the outer circumference of the single crystal substrate as a crystal orientation identification method instead of OF.

A single crystal substrate having a notch is processed according to the following procedure as described in Patent Document 1, for example. In the cylindrical grinding process, the surface of the single crystal is cylindrically ground, processed into a cylindrical single crystal ingot (ingot), and a V-shaped groove is formed in a specific direction on the side surface of the ingot (this groove slices the ingot). It becomes a temporary notch when In the slicing step, the ingot is sliced with a wire saw using free abrasive grains so as to form a disk-shaped substrate. In the beveling process, the substrate with the temporary notch formed in the slicing process is held on a rotatable substrate grinding stage, and the stage is brought close to the rotating grindstone while the substrate is rotated to grind the outer periphery of the substrate. Chamfer the end face. After the chamfering operation is completed, the stage is stopped from rotating, the stage is separated from the rotary grindstone, the notch grinding grindstone is rotated instead of the rotary grindstone, and the stage is brought closer to the notch forming position to form a notch. After the formation of the notch is completed, both the front and back surfaces are lapped using loose abrasive grains in the lapping process, the processing strain is removed in the etching process, and then the surface is mirror-polished on one side in the polishing process.

In the case of the piezoelectric single crystal substrate having the front surface side mirror-polished and the back surface side not mirror-polished as described above, it is possible to distinguish between the front and back surfaces by visually observing the degree of polishing.

Japanese Patent No. 4151155

On the other hand, in recent years, SAW filters have become more and more sophisticated. In such high-performance SAW filters, the line width of the circuit drawn on the piezoelectric single crystal substrate has become more precise. Crystal substrates are required to further improve their flatness. In order to further improve the flatness of the piezoelectric single crystal substrate, both surfaces of the recent piezoelectric single crystal substrate are often mirror-polished at the same time. However, in such a piezoelectric single crystal substrate having both sides mirror-polished, there is a problem that the front and back cannot be distinguished by the degree of grinding of the surface.

Conventionally, in a single crystal substrate provided with an OF or an IF, the front and back sides can be distinguished by the position of the IF on the basis of the OF. Therefore, even if the piezoelectric single crystal substrate is mirror-polished on both sides, the OF and IF are always present, and it is possible to easily distinguish between the front and back sides of the substrate (the front side and the back side).

On the other hand, when a notched single crystal substrate is mirror-polished on both sides, the appearance of the front and back surfaces is exactly the same.

Therefore, the present invention can easily and reliably discriminate between the front and back sides of a piezoelectric single crystal substrate having a notch, and in particular, can reliably discriminate between the front and back sides of a piezoelectric single crystal substrate having a notch and having both sides mirror-polished. It is an object of the present invention to provide a piezoelectric single crystal substrate and a method for manufacturing the same.

According to the aspect of the present invention, the piezoelectric single crystal substrate has a chamfered outer peripheral portion and a notch in the outer peripheral portion, and the outer peripheral portion has a crystal orientation direction with the center of the piezoelectric single crystal substrate as a reference. The formed first notch has a second notch at a position asymmetrical to the first notch, and the second notch has a different surface roughness from the first notch and is visually distinguishable. A piezoelectric single crystal substrate is provided.

In the piezoelectric single crystal substrate according to the aspect of the present invention, the second notch may form an angle of 45° or less with respect to the first notch with respect to the center of the piezoelectric single crystal substrate. The second notch may also be translucent. Also, the piezoelectric single crystal substrate may have a configuration in which both surfaces are mirror surfaces.

Further, according to an aspect of the present invention, there is provided a method for manufacturing a piezoelectric single crystal substrate, in which a piezoelectric single crystal thin plate having a beveled outer peripheral portion is subjected to bevel processing in the outer peripheral portion with the center of the thin plate as a reference. A first notch is formed in the crystal orientation direction, and a second notch that is different in surface roughness from the first notch and that can be visually distinguished is formed at a position asymmetrical to the first notch. A method for manufacturing a piezoelectric single crystal substrate is provided, comprising:

According to the present invention, it is possible to easily and reliably discriminate between the front and back of a piezoelectric single crystal substrate having a notch, and in particular, to reliably discriminate the front and back of a piezoelectric single crystal substrate having both surfaces mirror-polished and having a notch. It is possible to provide a piezoelectric single crystal substrate and a method for manufacturing the same.

(A) and (B) are diagrams showing an example of a piezoelectric single crystal substrate according to an embodiment. (A) is a plan view. (B) is a side view seen in the A direction shown in (A). 1 is a flow chart showing an example of a method for manufacturing a piezoelectric single crystal substrate according to an embodiment; It is a figure which shows an example of a cylindrical grinding process. It is a figure which shows an example of a groove|channel formation process. It is a figure which shows an example of a marking process, (A) is a perspective view, (B) is sectional drawing. It is a figure which shows an example of a slicing process. FIG. 10A is a diagram showing an example of a beveling process, in which (A) is a diagram showing a state in which the upper end of the outer peripheral portion of a thin plate is beveled, and (B) and (C) are diagrams showing an example of the outer peripheral portion of a thin plate after beveling. It is a figure showing, (B) is a side view, (C) is a top view. It is a figure which shows an example of a lapping process and a polishing process. It is a figure which shows an example of the conventional single-crystal substrate with OF. It is a figure which shows an example of the conventional single-crystal substrate with a notch. It is a figure which shows an example of a LT single crystal substrate.

Specific embodiments of the present invention will be described in detail below. In addition, the present invention is not limited to the following embodiments, and can be modified as appropriate without changing the gist of the present invention. In addition, in each drawing, a part or the whole is shown schematically and the scale is changed as appropriate. Further, in the following description, the description “A to B” means “A or more and B or less”.

As described above, piezoelectric single crystal substrates are used as materials for surface acoustic wave devices (SAW filters). For the SAW filter, for example, an LT single crystal substrate processed with a substrate main surface orientation of about 42° RY or an LN single crystal substrate processed with a main surface orientation of about 128° RY is used. Here, for example, 42° RY is a direction rotated 42° from the Y-axis to the Z-axis direction on the YZ plane with the X-axis as the rotation axis, as shown in FIG. A substrate processed perpendicularly to such an orientation is called a substrate with a main surface orientation of 42° RY. Since such a single crystal substrate has a tilted crystal axis and uses only a plane with a predetermined crystal orientation, it is necessary to identify the front and back of the substrate. A single crystal substrate provided with an OF and an IF can be distinguished from the front and back by the position of the IF with the OF as a reference. Therefore, even if the piezoelectric single crystal substrate is mirror-polished on both sides, OF and IF are always present, so that it is possible to easily distinguish between the front and back sides (the front side and the back side) of the single crystal substrate.

However, as described above, substrates with notches instead of OF and IF are becoming more popular as the diameter of substrates increases. In particular, it was impossible to determine the front and back of a notched substrate having both sides mirror-polished.

The piezoelectric single crystal substrate according to the present embodiment makes it possible to easily determine the front and back sides of a notched substrate having both sides mirror-polished, which had the problem of being unable to determine the front and back sides as described above. . The piezoelectric single crystal substrate according to this embodiment will be described below. FIGS. 1A and 1B are diagrams showing an example of a piezoelectric single crystal substrate according to an embodiment. (A) is a plan view. (B) is a side view seen in the A direction shown in (A).

The piezoelectric single crystal substrate CPX (hereinafter sometimes abbreviated as “single crystal substrate”) according to the present embodiment is a piezoelectric single crystal substrate having a chamfered outer peripheral portion 10 and a notch 11 in the outer peripheral portion 10 . In the peripheral portion 10, a first notch 11 is formed in the crystal orientation direction with respect to the center of the piezoelectric single crystal substrate CPX, and a second notch 12 is formed at a position asymmetrical to the first notch 11. The second notch 12 has a different surface roughness from the first notch 11 and is characterized by being a notch that can be visually distinguished.

The piezoelectric single crystal used for the single crystal substrate CPX of the present embodiment has piezoelectric properties such as lithium tantalate (LT) single crystal (LT single crystal), lithium niobate (LN) single crystal (LN single crystal), and the like. Single crystal.

The peripheral portion 10 of the single-crystal substrate CPX of the present embodiment is a beveled surface that is beveled in order to prevent cracking and chipping of the substrate. The outer peripheral portion 10 has a chamfered shape by beveling. The chamfered shape is not particularly limited as long as the corners are chamfered. Bevel processing is a processing for forming the chamfered shape described above. Beveling is performed by grinding with a whetstone or the like.

In the single crystal substrate CPX of the present embodiment, two notches are provided in part of the outer peripheral portion 10 of the single crystal substrate CPX. The single crystal substrate CPX of this embodiment has a first notch 11 and a second notch. A first notch 11 is formed in the direction of a predetermined crystal orientation in the peripheral portion 10 of the substrate. The shape of the first notch 11 is not particularly limited as long as it is visually recognizable. The shape of the first notch 11 may be V-shaped or U-shaped in cross section, for example. Although the depth of the first notch 11 is not particularly limited, it is preferably 0.7 mm to 1.5 mm.

The second notch 12 is formed at a position asymmetrical to the first notch 11 in the outer peripheral portion 10 of the substrate, similarly to the first notch 11 . It may be formed at a position other than the direction P1 (see FIG. 1A) which is 180° from the position of the first notch 11 with respect to the center C of the substrate. In other words, the position of the second notch 12 is not particularly limited as long as it is asymmetrical with the first notch 11 with respect to the center C of the single crystal substrate CPX.

The position of the second notch 12 is preferably formed at a position where the angle θ1 formed with the first notch 11 with respect to the center C of the single crystal substrate CPX is 45° or less. Further, the position of the second notch 12 is more preferably a position on the circumference (on the outer peripheral portion 10) at a distance L1 from the first notch 11 by 1 cm to 3 cm. By forming the first notch 11 and the second notch 12 close to each other, they are within the same field of view, and the front and back of the single crystal substrate can be easily identified.

The shape of the second notch 12 is not particularly limited. As with the first notch 11, the second notch 12 may have, for example, a V-shaped cross section or a U-shaped cross section. Although the depth of the second notch 12 is not particularly limited, it is preferably 0.7 mm to 1.5 mm. The shapes of the first notch 11 and the second notch 12 may be changed, or may be the same shape. It is more preferable to change the shape of the first notch 11 and the second notch 12 because the front and back sides of the single crystal substrate can be more easily identified.

The first notch 11 and the second notch 12 have different surface roughnesses and are visually distinguishable notches. A peripheral portion 10 of the single-crystal substrate CPX is chamfered by bevel processing (see FIG. 1B).

Beveling is performed by grinding with a whetstone or the like. The ground surface at this time is generally a dull and opaque surface. The machined surface on which the notch is to be formed is the same as the beveled ground surface because it is machined using a whetstone used for beveling.

Therefore, in the present embodiment, the number of the grindstone used when processing either the first notch 11 or the second notch 12 is changed, and the processing surface of the first notch 11 and the second notch 12 is changed. It is characterized by changing the surface state.

The outer peripheral portion 10 of the single-crystal substrate CPX is beveled with a grindstone of about #800, and the surface is dull and opaque, including the notch portion. For this reason, one of the processing surfaces of the first notch 11 and the second notch 12 is made by using a grindstone with a high number so that it can be easily distinguished visually. It is preferable to make the state translucent. In other words, one of the surface roughness of the first notch 11 and the surface roughness of the second notch 12 is preferably opaque and the other is translucent. The surface condition (surface roughness) of the notch is not particularly limited as long as there is a difference that can be visually recognized. For example, the grindstone used for processing the first notch 11 and the second notch 12 is preferably #1200 or higher when one grindstone has a count of #800, and the other grindstone has a higher count, and #1500. #2000 or less is more preferable, and the surface roughness Ra at this time is 0.05 μm to 0.1 μm.

As described above, it is possible to distinguish between the front and back sides of the single crystal substrate CPX by changing the size of the notch. The change in size (difference) is difficult to distinguish by visual inspection. However, as in the present embodiment, discrimination by the surface state of the notch portion (the first notch 11 and the second notch 12 are collectively referred to as the “notch portion”), especially in the case of opaqueness and translucency, is visually recognizable. is easier to distinguish by In addition, in the single crystal substrate CPX, the first notch 11 and the second notch 12 are changed (differences) in the surface state as described above and in combination with the changes (differences) in the size of the notches. This is more preferable because discrimination (identification) becomes easier.

As described above, the single-crystal substrate CPX according to the present embodiment has the first notch 11 formed in the crystal orientation direction with the center C of the piezoelectric single-crystal substrate CPX as a reference, and the first A second notch 12 is provided at a position asymmetrical to the notch 11. The second notch 12 is different in surface roughness from the first notch 11 and is visually distinguishable. In addition, in the single crystal substrate CPX of the present embodiment, configurations other than the above are arbitrary configurations. With the single crystal substrate CPX according to the present embodiment, it is possible to reliably determine the front and back sides of the single crystal substrate CPX based on the relative positions and surface states of the first notch 11 and the second notch 12 . In particular, with the single crystal substrate CPX according to the present embodiment, it is possible to reliably distinguish between the front and back of the substrate, even if the front and back of the substrate are mirror-polished on both sides, which was conventionally impossible to distinguish between the front and back. Since the single crystal substrate according to the present embodiment can reliably determine the front and back sides of the substrate, it is possible to prevent the problem that the front side and the back side cannot be used as a material for a surface acoustic wave device or the like.

Note that the state of the front surface or the rear surface of the single crystal substrate CPX is not particularly limited. For example, in the single crystal substrate CPX, the front surface or the back surface may or may not be a mirror surface. When the front and back surfaces of the single crystal substrate CPX are mirror surfaces, as described above, it is possible to reliably determine the front and back surfaces of the substrate, which could not be visually determined in the conventional art. The effect of the single crystal substrate CPX is more remarkable. In addition, even if the front surface or the back surface of the single crystal substrate CPX is not a mirror surface, the front surface and back surface of the substrate can be reliably determined.

An example of the method for manufacturing the single crystal substrate of this embodiment will be described below. FIG. 2 is a flow chart showing an example of a method for manufacturing a single crystal substrate. Note that the method for manufacturing a single crystal substrate described below is an example, and does not limit the method for manufacturing a single crystal substrate according to this embodiment. In addition, in the method for manufacturing the single crystal substrate of the present embodiment, the items described for the single crystal substrate of the present embodiment are applicable, and the description thereof will be omitted or simplified as appropriate. In addition, the items described in the method for manufacturing the single crystal substrate of this embodiment are also applicable to the single crystal substrate of this embodiment described above.

As shown in FIG. 2, the method for manufacturing a single crystal substrate of this embodiment includes a cylindrical grinding step S1, a groove forming step S2, a marking step S3, a slicing step S4, a beveling step S5, and a lapping step S6. , and a polishing step S7.

(Cylindrical grinding step S1)
FIG. 3 is a diagram showing an example of the cylindrical grinding step S1. Cylindrical grinding step S1 is a step of subjecting a side surface (column side surface, outer peripheral surface) of a grown piezoelectric single crystal ingot (hereinafter abbreviated to ingot) to cylindrical grinding to obtain a single crystal ingot C1 having a uniform outer diameter. is. Cylindrical grinding can be carried out by known methods. It should be noted that the method for manufacturing a single crystal substrate according to the present embodiment may not include the cylindrical grinding step S1. For example, the method for manufacturing a single crystal substrate of the present embodiment can be carried out using a previously manufactured piezoelectric single crystal ingot subjected to cylindrical grinding.

(Groove forming step S2)
FIG. 4 is a perspective view showing an example of the groove forming step S2. The groove forming step S2 is a step of forming a predetermined groove 14 on the side surface of the ingot C1 that has been cylindrically ground. The grooves 14 can be formed by a known method such as forming the grooves by grinding the side surface of the ingot C1.

Groove 14 is formed to extend in the direction of central axis AX1 of ingot C1. The grooves 14 are formed at two locations, a first groove 14a serving as the first notch 11 and a second groove 14b serving as the second notch 12. As shown in FIG. The first groove 14a is formed at a position indicating a predetermined crystal orientation and used for identifying the predetermined crystal orientation. The second groove 14b is formed at a position asymmetrical to the first groove 14a. If the second groove 14b is positioned in a direction other than 180° from the position of the first groove 14a, in other words, the position of the second groove 14b is positioned in the first direction with respect to the center AX1 of the single crystal C2. There is no particular limitation as long as the position is asymmetrical with the groove 14a. The position of the second groove 14b is preferably formed so that the angle θ1 between the center AX1 of the single crystal and the first groove 14a is 45° or less. Further, the position of the second groove 14b is more preferably a position on the circumference (on the outer peripheral portion 10) 1 cm to 3 cm away from the first groove 14a.

The first groove 14a and the second groove 14b remain without being removed in the beveling step S5, and the first notch 11 and the second notch 12 (see FIG. 1) are finally used for identification of a predetermined crystal orientation. (A)). The first notch 11 and the second notch 12 are processed into final shapes by a beveling step S5 based on the shapes of the first groove 14a and the second groove 14b, respectively. The depths of the first grooves 14a and the second grooves 14b and the machining allowance in the beveling step S5 are such that the first grooves 14a and the second grooves 14b are not removed in the beveling step S5, and the first grooves 14a and 14b are not removed in the beveling step S5. notch 11 and second notch 12. In the case of the LT single crystal, the first groove 14a is formed so as to exhibit the crystal orientation in the +X direction shown in FIG.

The cross-sectional shapes of the first groove 14a and the second groove 14b are preferably V-shaped, as shown in FIG. In addition, the cross-sectional shape of the first groove 14a and the second groove 14b is not limited to the V-shape, and may be, for example, a U-shape. Although the depth of the first groove 14a and the second groove 14b is not particularly limited, it is preferably 0.7 mm to 1.5 mm, for example, from the viewpoint of ease of recognition and processing loss. Also, the shape of the first groove 14a and the second groove 14b may be changed.

(Marking step S3)
5A and 5B are diagrams showing an example of the marking process, where (A) is a perspective view and (B) is a cross-sectional view. The marking step S3 is a step of forming a mark M1 on a side surface (peripheral surface) of the ingot C1 in a portion that is asymmetrical with the grooves 14 (first groove 14a and second groove 14b) with respect to the axis AX1 of the ingot C1. is.

The mark M1 is formed on the outer peripheral side of the bottoms of the first groove 14a and the second groove 14b. The mark M1 is formed at a position where the front and back of the substrate can be distinguished. For example, when the mark M1 is rotated around the central axis AX1 from the position of the first groove 14a shown in FIG. 14b is arranged at a position that does not interfere with it. This makes it possible to determine the front and back of the substrate from the positional relationship (relative position) between the first groove 14a, the second groove 14b, and the mark M1. If the first groove 14a, the second groove 14b, and the mark M1 are symmetrical with respect to the central axis AX1, it becomes difficult to distinguish the front and back of the substrate after the slicing step S4, which will be described later. The position of the mark M1 is not particularly limited, but if the distance L2 (see FIG. 5B) from the first groove 14a or the second groove 14b to the mark M1 is 1 to 5 cm, the front and back can be distinguished. It is preferred because it is easy. For example, in the case of the example shown in FIG. 5B, the positions of the marks M1 with respect to the first grooves 14a and the second grooves 14b in the thin plate CP1 after the slicing step S4, which will be described later, are in the clockwise direction on the surface, and in the reverse direction. In the case of the clockwise direction, it is the back side, and it becomes easy to distinguish the front and back sides of the substrate. Note that the position of the mark M1 is not limited as long as it is a position at which the front and back of the substrate can be discriminated.

A method of forming (marking) the mark M1 is not particularly limited. For example, the mark M1 can be formed by laser marker processing, blast processing, paint application with a pen, or the like. For example, in the case of laser marker processing, CO2 laser (λ = 10.6 µm), YAG laser (λ = 1.06 µm), YVO4 SHG laser (λ = 532 nm), and YAG fourth harmonic laser (λ = 265 nm) are used. be able to. In the case of blasting, sandblasting or the like using FO abrasive grains of about #4000 can be used. In the present embodiment, the marking is performed by applying paint (ink) with a pen so that the front and back can be identified after the slicing step S4, which is a later step, and can be removed in the beveling step S5, which is a later step. This is preferable because the number of processing man-hours is small. In the above marking, the types of pen and paint (ink) are not particularly limited, but pens such as markers can be used, for example. In the case of marking with a pen, the position and size of the mark M1 are not limited. The mark M1 may be formed by marking with a pen.

(Slicing step S4)
FIG. 6 is a diagram showing an example of the slicing step S4. The slicing step S4 is a step of slicing the ingot C2 in which the first groove 14a and the second groove 14b and the marks M1 are formed, and processing it into the thin plate CP1. Slicing process S4 can be implemented by a well-known method. The slicing step S4 can be performed by, for example, a known wire saw device such as a multi-wire saw device. A first groove 14a, a second groove 14b, and a mark M1 are formed in the thin plate CP1 formed by the slicing step S4. As a result, the thin plate CP1 formed in the slicing step S4 can be distinguished from the front and back of the substrate. For example, when marking is performed using a pen (paint, ink) or the like at a position 2 cm away in the clockwise direction from the second groove 14b, the position of the mark M1 is in the clockwise direction with respect to the second groove 14b. It is easy to distinguish between the front and back sides of the substrate when the direction is in the direction of the counterclockwise direction.

(Beveling step S5)
FIGS. 7A to 7C are diagrams showing an example of the beveling step S5. FIG. 7A is a diagram showing a state in which the upper end of the outer peripheral portion of the thin plate is beveled, and FIGS. ) is a diagram showing an example of a peripheral portion of a thin plate after beveling, (B) is a cross-sectional view, and (C) is a plan view. The beveling step S5 is a step of chamfering the outer peripheral portion 10 of the thin plate CP1, forming the first notch 11 and the second notch 12, and removing the mark M1. In the beveling step S5, the outer peripheral portion 10 of the thin plate CP1 is ground to form the first notch 11 and the second notch 12 at the positions of the first groove 14a and the second groove 14b. By the beveling step S5, a thin plate CP3 in which the first notch 11 and the second notch 12 shown in FIG. 7C are formed and the marks M1 are removed can be obtained. Note that this thin plate CP3 is included in the above-described single crystal substrate CPX of the present embodiment.

The beveling step S5 can be performed using a device similar to that used for conventional beveling. In the beveling step S5, for example, as shown in FIG. 7A, an apparatus is used in which a ring-shaped chamfering grindstone 32 is fixed to a groove on the peripheral surface of the core disk. In the beveling step S5, as shown in FIG. 7A, the outer peripheral portion 10 of the thin plate CP1 held on the substrate holding table 31 is pressed against the upper inclined surface of the rotating grindstone 32 for chamfering, and the upper edge of the thin plate CP1 is pressed. After grinding the corners of the thin plate CP1, the substrate holder 31 is lowered by a predetermined amount, and the corners of the lower edge of the thin plate CP1 are pressed against the lower inclined surface of the chamfering grindstone 32 and ground. As a result, the outer peripheral portion of the thin plate CP1 is chamfered, and the thin plate CP2 from which the marks M1 are removed is obtained.

The notch portions (the first notch 11 and the second notch 12) are processed by stopping the rotation of the thin plate CP2 whose outer peripheral portion has been chamfered and placing it at the predetermined positions of the first groove 14a and the second groove 14b. It is formed by processing using a whetstone of the shape of When machining the first notch 11 (first groove 14a) and the second notch 12 (second groove 14b), one of them is machined using a whetstone with a different grindstone count. As for one of the whetstones, it is preferable to use a whetstone with a high count. By using a high-count grindstone, as described above, the first notch 11 and the second notch 12 can be formed so as to have different surface conditions (surface roughness), and the difference in surface roughness , it is possible to visually distinguish the front and back of the substrate (the first notch 11 and the second notch 12). Above all, by making the surface state of either the first notch 11 or the second notch 12 translucent (processing so as to reduce the surface roughness), the first notch 11 and the second notch 12 can be visually recognized. The notch 12 can be easily distinguished, and as a result, the front and back of the substrate can be easily distinguished. For example, the first groove 14a is processed using a #800 grindstone to form the first notch 11, and the second groove 14b is processed with a grindstone of #1200 or more, preferably a grindstone of #1500 or more and #2000 or less. may be used to form the second notch 12 . By making a difference in the grit number of the grindstone used for forming the first notch 11 and the second notch 12, the surface state of the first notch 11 and the second notch 12 after processing is changed, and the surface roughness is different. As a result, it is possible to easily distinguish between the first notch 11 and the second notch 12 by visual recognition (discrimination of the front and back of the substrate). By the above processing, the thin plate CP3 is obtained in which the second notches 12 are formed with notches that are different in surface roughness from the first notches 11 and can be visually distinguished. This thin plate CP3 is included in the piezoelectric single crystal substrate CPX of the above-described lower present embodiment.

In the beveling step S5, as described above, the machining allowance is adjusted so as to remove the mark M1. The machining allowance in the beveling step S5 is not particularly limited, but from the viewpoint of reducing the loss due to processing, the smaller the machining allowance, the better. When the mark M1 is formed with the above pen (paint, ink), it is possible to reduce the machining allowance for beveling, which is preferable because it is easy.

(Lapping step S6)
FIG. 8 is a plan view showing an example of lapping step S6 and polishing step S7. The lapping step S6 is a step of polishing the thin plate CP3 obtained in the beveling step S5 to adjust the surface shape and thickness.

In this embodiment, in the steps after the beveling step S5, the front and back of the substrate can be determined by the first notch 11 and the second notch 12 formed in the beveling step. That is, in the present embodiment, the steps after the bevel step S5 can be performed after the front and back sides of the substrate are easily determined visually.

The lapping step S6 can be performed after determining the front and back of the substrate. The lapping step S6 can be performed by a known lapping method. For example, the lapping step S6 can use a double-sided lapping device. Conditions for the lapping step S6 are not particularly limited.

After the lapping step S6, a thin plate CP4 is obtained in which the surface shape and thickness of the substrate are adjusted. The sheet CP4 comprises a first notch 11 and a second notch 12 . The thin plate CP4 corresponds to the single crystal substrate CPX of this embodiment described above.

After the lapping step S6, an etching step (etching treatment) may be performed as necessary. The etching process is a process for removing processing strain. The etching process is, for example, chemical etching using acid. The etching amount in the etching step is not particularly limited as long as the surface roughness of the first notch 11 and the second notch 12 are different and can be visually identified.

(Polishing step S7)
The polishing step S7 is a step of polishing the lapped thin plate CP4 to a mirror surface by polishing the main surface F or both surfaces F and R (see FIG. 1B) of the thin plate. The polishing step S7 of this example is a step of mirror-polishing the main surface F side or both surfaces (main surface F and back surface R) of the thin plate CP4 whose surface shape and thickness have been adjusted in the lapping step S6. The thin plate CP5 obtained by the polishing step S7 is a substrate having the first notch 11 and the second notch 12 and mirror-polished surfaces on both sides. This thin plate CP5 corresponds to the single crystal substrate CPX of the present embodiment described above.

The polishing step S7 can be performed using a known single-sided polishing device or double-sided polishing device. For example, a single-sided polishing machine attaches the back surface of the thin plate to a block, fixes the block to the head of the single-sided polishing machine, presses the lower side of the thin plate (the front side of the thin plate) against a lower surface plate on which a polishing cloth is pasted, and polishes the surface of the thin plate. A polishing liquid is supplied between the plate and the polishing cloth, and the thin plate and the polishing cloth are rotated to mirror-finish one side of the thin plate.

As described above, in the method of manufacturing a piezoelectric single crystal substrate according to the present embodiment, a piezoelectric single crystal thin plate whose outer peripheral portion is beveled is subjected to bevel processing in the outer peripheral portion in the crystal orientation direction with the center of the thin plate as a reference. A first notch 11 is formed in the first notch 11, and a second notch 12 that is different in surface roughness from the first notch 11 and that can be visually distinguished is formed at a position that is asymmetrical with the first notch 11. Including. In addition, in the manufacturing method of the piezoelectric single crystal substrate of the present embodiment, configurations other than the above are arbitrary configurations. According to the method of manufacturing the piezoelectric single crystal substrate of the present embodiment, it is possible to easily and reliably distinguish between the front and back sides of the piezoelectric single crystal substrate having the notch. It is possible to provide a piezoelectric single-crystal substrate and a method of manufacturing the same that can reliably determine the front and back of a crystal substrate.

EXAMPLES The present invention will be more specifically described below with reference to examples, but the present invention is not limited to the following examples.

[Example 1]
A lithium tantalate single crystal 36° RY grown ingot with a diameter of 210 mm was prepared as a piezoelectric single crystal. This ingot was surfaced on the 42° RY plane and cylindrically ground to a diameter of 201 mmφ. A V-shaped first groove 14a (V groove) having a depth of 1 mm is provided in the cylindrically ground ingot in the +X direction of FIG. 11, and the angle rotated around the central axis AX1 from the position of the first groove 14a is θ1, a V-shaped second groove 14b (V groove) having a depth of 1 mm is provided at a position where θ1 is 20°, and is 2 cm away from the second groove 14b in the clockwise direction when viewed from the surface. Marking was performed with a marker with a thickness of 5 mm at the position. In the slicing step, 80 sheets of 580 μm-thick thin plates were obtained by slicing using a wire saw cutting device. It was ground to a diameter of 200.05 mmφ in a bevel process, and notched at the positions of the first groove 14a and the second groove 14b. At this time, the first notch 11 and the second notch 12 were formed by processing the first groove 14a using a #800 grindstone and the second groove 14b using a #1500 grindstone. The surface roughness of the first notch 11 was Ra 0.3 μm, and the surface roughness of the second notch 12 was Ra 0.05 μm. As for the surface state, the first notch 11 was opaque, and the second notch 12 was translucent and easily visually recognized. In the lapping process, GC#1000 was used to polish both the front and back surfaces to a thickness of 25 μm. In the etching process, 0.5 μm etching was performed, and in the polishing process, the front surface and the back surface were each mirror-polished to 15 μm. As described above, the first notch 11 and the second notch 12 at a position asymmetrical to the first notch 11 are provided, and the second notch 12 is different in surface roughness from the first notch 11 and A piezoelectric single crystal substrate CPX that can be visually distinguished was obtained.

When the obtained piezoelectric single crystal substrates were put into a CPX device forming apparatus, all 80 substrates had devices formed on their front surfaces (principal surfaces), and not a single substrate was found to be upside down.

[Comparative Example 1]
A lithium tantalate single crystal 36° RY grown ingot with a diameter of 210 mm was prepared as a piezoelectric single crystal. This ingot was surfaced on the 42° RY plane and cylindrically ground to a diameter of 201 mmφ. A V-shaped groove (V groove) with a depth of 1 mm was provided in the +X direction of FIG. Marked with magic. In the slicing step, 80 sheets of 580 μm-thick thin plates were obtained by slicing using a wire saw cutting device. Marking was performed with a marker near the V-groove on the surface after slicing. It was ground to a diameter of 200.05 mmφ in a bevel process, and notched at the position of the V groove. In the lapping process, GC#1000 was used to polish both the front and back surfaces to a thickness of 25 μm. In the etching process, 0.5 μm etching was performed, and in the polishing process, the front surface and the back surface were each mirror-polished to 15 μm. A piezoelectric single crystal substrate was obtained as described above.

When the obtained piezoelectric single crystal substrates were put into a device forming apparatus, 5 out of 80 substrates had a device formed on the back surface, and 5 substrates were reversed.

From the results of the above-described examples and comparative examples, the piezoelectric single crystal substrate according to the present embodiment has the front and back sides of the piezoelectric single crystal substrate having a notch, depending on the relative position and surface state of the first notch and the second notch. It has been confirmed that it is possible to reliably discriminate between the front and back of the substrate, and it is possible to reliably determine the front and back of the substrate even in a substrate having a notch and having both sides mirror-polished, which was impossible to visually distinguish between the front and back. confirmed that it can be done.

Note that the technical scope of the present invention is not limited to the aspects described in the above-described embodiments and the like. One or more of the requirements described in the above embodiments and the like may be omitted. In addition, the requirements described in the above embodiments and the like can be combined as appropriate. In addition, as long as it is permitted by law, the disclosure of all the documents cited in the above-described embodiments and the like is incorporated into the description of the text.

According to the present invention, it is possible to prevent defects due to the wrong side in the device process of a notched double-sided polished piezoelectric single crystal substrate.

C1, C2: piezoelectric single crystal ingots CP1 to CP2: thin plates (piezoelectric single crystal thin plates)
CPX, CP3 to CP5: Piezoelectric Single Crystal Substrate 10: Outer Periphery 11: First Notch 12: Second Notch 14: Groove 14a: First Groove 14b: Second Groove

Claims (5)

A piezoelectric single crystal substrate having a chamfered outer peripheral portion and a notch in the outer peripheral portion,
In the outer peripheral portion, a first notch formed in a crystal orientation direction with respect to the center of the piezoelectric single crystal substrate, and a second notch at a position asymmetrical to the first notch,
The piezoelectric single crystal substrate, wherein the second notch has a surface roughness different from that of the first notch and is visually distinguishable. 2. The piezoelectric single crystal substrate according to claim 1, wherein said second notch forms an angle of 45° or less with respect to said first notch with respect to the center of said piezoelectric single crystal substrate. 3. The piezoelectric single crystal substrate according to claim 1, wherein said second notch is translucent. 4. The piezoelectric single crystal substrate according to claim 1, wherein both surfaces of said piezoelectric single crystal substrate are mirror surfaces. A method for manufacturing a piezoelectric single crystal substrate,
forming a first notch in a crystal orientation direction with the center of the thin plate as a reference in the outer peripheral portion of a piezoelectric single crystal thin plate having a beveled outer peripheral portion;
A method of manufacturing a piezoelectric single crystal substrate, comprising forming a second notch that is different in surface roughness from the first notch and that is visually distinguishable from the first notch at a position that is asymmetric with the first notch. .

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