A method for determining the front and back of an x-cut lithium niobate wafer

Abstract

The application discloses a method for determining the front and back surfaces of an X-cut lithium niobate wafer. The Y axis of the X-cut lithium niobate wafer is rotated by an angle alpha along the Z axis of the X-cut lithium niobate wafer, and then the X-cut lithium niobate wafer is clamped between an upper test probe and a lower test probe of an X-cut lithium niobate wafer front and back surface determination device. An electromagnetic driver in the X-cut lithium niobate wafer front and back surface determination device is used to exert a low-frequency alternating force on the X-cut lithium niobate wafer, so that the X-cut lithium niobate wafer generates alternating charges, and a measured output voltage of the X-cut lithium niobate wafer is obtained. The measured output voltage of the X-cut lithium niobate wafer is used to calculate a longitudinal piezoelectric strain constant of the X-cut lithium niobate wafer. Based on the longitudinal piezoelectric strain constant of the X-cut lithium niobate wafer, the front and back surface state of the X-cut lithium niobate wafer is determined. The front and back surface state is that the +X surface of the X-cut lithium niobate wafer faces upward or the -X surface of the X-cut lithium niobate wafer faces upward. The method can successfully identify the front and back surfaces of the X-cut lithium niobate wafer.

Description

TECHNICAL FIELD

[0001] The application relates to a method for determining the front and back surfaces of an X-cut lithium niobate wafer and belongs to the technical field of determining the front and back surfaces of an X-cut lithium niobate wafer. BACKGROUND

[0002] With the technological innovation in the field of semiconductor manufacturing, wafer bonding plays an increasingly important role in the field of semiconductor hetero-integrated manufacturing. For example, lithium niobate, lithium tantalate and other ferroelectric single crystals are widely used in filters, photoelectric modulators, optical waveguides, frequency doubling converters and holographic storage due to their excellent performance as ferroelectric single crystal semiconductors and their good photoelectric, acousto-optic, piezoelectric, birefringent and nonlinear physical properties as well as their high temperature resistance, corrosion resistance and stable mechanical properties. In recent years, with the improvement of rare earth doping engineering, domain engineering, near stoichiometric ratio growth and processing technology, lithium niobate optoelectronic devices have developed rapidly in the fields of all-optical signal processing, optical data storage and optical sensing.

[0003] At present, before lithium niobate single crystal bonding, cleaning treatment is required, and then the front surface of the lithium niobate single crystal wafer is bonded to the substrate layer. After cleaning treatment, the front and back surfaces of the lithium niobate single crystal wafer may be reversed. The front and back surfaces of the lithium niobate single crystal wafer cannot be distinguished by the naked eye, and it is difficult to distinguish the front and back surfaces of the lithium niobate single crystal wafer.

[0004] For Y-cut lithium niobate wafers and Z-cut lithium niobate wafers, the specific method for identifying the front and back surfaces of the Y-cut lithium niobate wafer and the Z-cut lithium niobate wafer is to horizontally place the Y-cut lithium niobate wafer or the Z-cut lithium niobate wafer between the upper and lower test probes of a quasi-static D33 piezoelectric coefficient measuring instrument. However, this device can only successfully identify the front and back surfaces of the Y-cut lithium niobate wafer and the Z-cut lithium niobate wafer under the condition that the Y-cut lithium niobate wafer and the Z-cut lithium niobate wafer have strong conductive properties. Since the X-cut lithium niobate wafer has poor conductive properties, the longitudinal piezoelectric strain constant of the X-cut lithium niobate wafer is 0C / N when the above method is used to test the X-cut lithium niobate wafer. Therefore, the quasi-static D33 piezoelectric coefficient measuring instrument cannot identify the front and back surfaces of the X-cut lithium niobate wafer. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the defects of the prior art and provide a method for determining the front and back surfaces of an X-cut lithium niobate wafer. The Y-axis of the X-cut lithium niobate wafer is rotated by an angle alpha around the Z-axis center and then placed in a quasi-static D33 piezoelectric coefficient measuring instrument to measure the measured output voltage V of the X-cut lithium niobate wafer. The longitudinal piezoelectric strain constant of the X-cut lithium niobate wafer is calculated based on the measured output voltage V of the X-cut lithium niobate wafer. The present method can successfully identify the front and back surfaces of the X-cut lithium niobate wafer.

[0006] In a first aspect, the present application provides a method for determining the front and back surfaces of an X-cut lithium niobate wafer, comprising:

[0007] rotating the Y axis of the X-cut lithium niobate wafer by an angle of α around the Z axis of the X-cut lithium niobate wafer, and then clamping the X-cut lithium niobate wafer between the upper test probe and the lower test probe of the X-cut lithium niobate wafer front and back surface determination device;

[0008] applying a low-frequency alternating force on the X-cut lithium niobate wafer using an electromagnetic driver in the X-cut lithium niobate wafer front and back surface determination device, generating an alternating electric charge on the X-cut lithium niobate wafer, and measuring the measured output voltage of the X-cut lithium niobate wafer;

[0009] calculating the longitudinal piezoelectric strain constant of the X-cut lithium niobate wafer using the measured output voltage of the X-cut lithium niobate wafer;

[0010] determining the front and back surface state of the X-cut lithium niobate wafer based on the longitudinal piezoelectric strain constant of the X-cut lithium niobate wafer, wherein the front and back surface state is either the +X surface of the X-cut lithium niobate wafer facing up or the -X surface of the X-cut lithium niobate wafer facing up.

[0011] In combination with the first aspect, the angle α is in the range of 30-60°.

[0012] In combination with the first aspect, the longitudinal piezoelectric strain constant d 33 of the X-cut lithium niobate wafer is calculated using the measured output voltage V1 of the X-cut lithium niobate wafer.

[0013] d 33 = V1 / (h×D),

[0014] wherein V1 is the measured output voltage of the X-cut lithium niobate wafer, h is the thickness of the X-cut lithium niobate wafer, and D is the mechanical strain coefficient.

[0015] In combination with the first aspect, if the longitudinal piezoelectric strain constant d 33 of the X-cut lithium niobate wafer is positive, it is determined that the +X surface of the X-cut lithium niobate wafer is facing up.

[0016] In combination with the first aspect, if the longitudinal piezoelectric strain constant d 33 of the X-cut lithium niobate wafer is negative, it is determined that the -X surface of the X-cut lithium niobate wafer is facing up.

[0017] In a second aspect, an X-cut lithium niobate wafer front and back surface determination device is provided for performing the steps of any one of the methods of the first aspect, comprising an electromagnetic driver, a comparison transducer electrode, an insulating column, and test probes, wherein the test probes comprise an upper test probe and a lower test probe located below the upper test probe, the X-cut lithium niobate wafer is placed between the upper test probe and the lower test probe, and the lower test probe is fixedly connected to the comparison transducer electrode through the insulating column.

[0018] In combination with the second aspect, the measured resonator parallel capacitor C1 is connected to the upper test probe at one end and to the upper test probe at the other end.

[0019] In combination with the second aspect, the comparison resonator electrode comprises a comparison resonator upper electrode and a comparison resonator lower electrode, and the comparison resonator is fixedly arranged between the comparison resonator upper electrode and the comparison resonator lower electrode.

[0020] In the second aspect, the present application provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps of the method of any one of the first aspect when executing the program.

[0021] In the third aspect, the present application provides a computer readable storage medium, which stores a computer program, and the computer program is executable on the processor to implement the steps of the method of any one of the first aspect.

[0022] The present application has the following beneficial effects:

[0023] In the present application, the Y axis of the X-cut lithium niobate wafer is rotated by an angle of a around the Z axis of the X-cut lithium niobate wafer, and then the X-cut lithium niobate wafer is clamped between the upper test probe and the lower test probe of the X-cut lithium niobate wafer front and back determination device. The placement of rotating the X-cut lithium niobate wafer around the Z axis or the Y axis enhances the conductivity of the X-cut lithium niobate wafer. The measured longitudinal piezoelectric strain constant of the X-cut lithium niobate wafer is a positive or negative number rather than zero. Therefore, the present application can successfully identify the front and back of the X-cut lithium niobate wafer, and overcome the technical problem that the longitudinal piezoelectric strain constant of the X-cut lithium niobate wafer cannot be successfully measured due to poor conductivity of the X-cut lithium niobate wafer. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings needed in the embodiments. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0025] Figure 1 is a sectional view in some embodiments of the present application;

[0026] Figure 2 is a perspective view of the X-cut lithium niobate wafer in some embodiments of the present application;

[0027] Figure 3 is a schematic diagram of the rotation angle a of the X-cut lithium niobate wafer in some embodiments of the present application.

[0028] The meaning of the reference signs is as follows: 1 - electromagnetic driver; 2 - comparison vibrator electrode; 21 - upper comparison vibrator electrode; 22 - lower comparison vibrator electrode; 3 - comparison vibrator; 4 - insulating column; 5 - test probe; 51 - upper test probe; 52 - lower test probe; 6 - X-cut lithium niobate wafer. DETAILED DESCRIPTION

[0029] In order to facilitate the technical solutions of the application, the following first explains some concepts related to the present application.

[0030] Reference Figure 1 The present application provides a method for determining the front and back of an X-cut lithium niobate wafer, which comprises: rotating the Y axis of the X-cut lithium niobate wafer by an angle of a around the Z axis of the X-cut lithium niobate wafer, and then clamping the X-cut lithium niobate wafer between the upper test probe and the lower test probe of the X-cut lithium niobate wafer front and back determination device, as shown in Figure 2 The electromagnetic driver in the X-cut lithium niobate wafer front and back determination device is used to apply a low-frequency alternating force on the X-cut lithium niobate wafer, so that the X-cut lithium niobate wafer generates alternating charges, and the measured output voltage of the X-cut lithium niobate wafer is obtained. The longitudinal piezoelectric strain constant of the X-cut lithium niobate wafer is calculated based on the measured output voltage of the X-cut lithium niobate wafer. Based on the longitudinal piezoelectric strain constant of the X-cut lithium niobate wafer, the front and back state of the X-cut lithium niobate wafer is determined, which is the +X surface of the X-cut lithium niobate wafer facing up or the -X surface of the X-cut lithium niobate wafer facing up. In the examples of the present application, the angle of a is in the range of 30-60°, and in the present embodiment, the value can be 45°. If the longitudinal piezoelectric strain constant d 33 of the X-cut lithium niobate wafer is positive, it is determined that the +X surface of the X-cut lithium niobate wafer faces up. If the longitudinal piezoelectric strain constant d 33 of the X-cut lithium niobate wafer is negative, it is determined that the -X surface of the X-cut lithium niobate wafer faces up. Since the X-cut lithium niobate wafer has poor conductivity, as shown in Figure 3 the present application adopts the method of rotating the Y axis of the X-cut lithium niobate wafer by an angle of a around the Z axis of the X-cut lithium niobate wafer, and then clamping the X-cut lithium niobate wafer between the upper test probe and the lower test probe of the X-cut lithium niobate wafer front and back determination device. This placement method enhances the conductivity of the X-cut lithium niobate wafer, and the measured longitudinal piezoelectric strain constant of the X-cut lithium niobate wafer is positive or negative rather than zero, so the present application can successfully identify the front and back of the X-cut lithium niobate wafer.

[0031] In the examples of the present application, the longitudinal piezoelectric strain constant d 33 of the X-cut lithium niobate wafer is calculated based on the measured output voltage V1 of the X-cut lithium niobate wafer: d 33 = V1 / (h x D), where V1 is the measured output voltage of the X-cut lithium niobate wafer, h is the thickness of the X-cut lithium niobate wafer, and D is the mechanical strain coefficient.

[0032] In the embodiment of the present application, the X-cut lithium niobate wafer front-back face determination device for performing the steps of any of the above-mentioned methods comprises an electromagnetic driver, a comparison vibrator electrode, an insulating column and a test probe, the test probe comprising an upper test probe and a lower test probe located below the upper test probe, the X-cut lithium niobate wafer being placed between the upper test probe and the lower test probe, and the lower test probe being fixedly connected to the comparison vibrator electrode through the insulating column.

[0033] In the embodiment of the present application, the comparison vibrator electrode comprises a comparison vibrator upper electrode and a comparison vibrator lower electrode, and the comparison vibrator is fixedly arranged between the comparison vibrator upper electrode and the comparison vibrator lower electrode. The present application comprises a measured vibrator parallel capacitor C1, one end of the measured vibrator parallel capacitor C1 being connected to the upper test probe, and the other end of the measured vibrator parallel capacitor C1 being connected to the upper test probe. The present application establishes a measured output voltage V1 on the measured vibrator parallel capacitor C1; and the piezoelectric charge Q2 released by the comparison vibrator 3 establishes a voltage V2 on the comparison vibrator parallel capacitor C2, C1 = C2 > 100C T T , C 33 is the free capacitance of the vibrator.

[0034] The X-cut lithium niobate wafer front-back face determination device is an instrument for measuring the piezoelectric coefficient d33 of a piezoelectric material. In the measurement, a mechanical strain is applied to the X-cut lithium niobate wafer, and the piezoelectric material (X-cut lithium niobate wafer) is strained under the action of an applied electric field. The direction of the mechanical strain can be determined, and the polarity of the electric field can be controlled by the instrument. Therefore, the determination of the sign of the X-cut lithium niobate wafer in the measurement depends on the relative direction relationship between the mechanical strain and the electric field, i.e. when the mechanical strain and the electric field are in the same direction, the positive strain of the X-cut lithium niobate wafer corresponds to the positive electric field, and vice versa, the negative strain of the X-cut lithium niobate wafer corresponds to the negative electric field.

[0035] The X-cut lithium niobate wafer front-back face determination device in the measurement will apply a mechanical strain, and the piezoelectric material (X-cut lithium niobate wafer) will be strained under the action of an applied electric field. The direction of the mechanical strain can be determined, and the polarity of the electric field can be controlled by the instrument. Therefore, the determination of the sign of the X-cut lithium niobate wafer in the measurement depends on the relative direction relationship between the mechanical strain and the electric field, i.e. when the mechanical strain and the electric field are in the same direction, the positive strain of the X-cut lithium niobate wafer corresponds to the positive electric field, and vice versa, the negative strain of the X-cut lithium niobate wafer corresponds to the negative electric field.

[0036] In the embodiment of the present application, the present application provides an electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor executes the program to implement the steps of any of the above-mentioned methods. ​

[0037] In the embodiments of the present application, a computer readable storage medium is provided, and the computer readable storage medium stores a computer program. The computer program is executed by a processor to implement the steps of the method according to any one of the preceding embodiments.

[0038] Each of the embodiments in the specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other. Each of the embodiments mainly describes the difference from other embodiments.

[0039] Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the present application cover any and all variations of the application that come within the scope of the following claims and their equivalents. It is intended that the specification and examples be considered exemplary only, with the true scope and spirit of the application being indicated by the following claims.

[0040] The above detailed description of the application is further detailed for the purpose of the application, technical solutions and beneficial effects. It should be understood that the above is only a specific embodiment of the application, and is not used to limit the protection scope of the application. Any modification, equivalent replacement, improvement, etc. made on the basis of the technical solutions of the application shall be included in the protection scope of the application.

Claims

1. A method for determining the front and back surfaces of an X-cut lithium niobate wafer, characterized by, The application relates to an X-cut lithium niobate wafer front-back face judging device and a judging method thereof. The X-cut lithium niobate wafer is clamped between an upper test probe (51) and a lower test probe (52) of the X-cut lithium niobate wafer front-back face judging device after the Y-axis of the X-cut lithium niobate wafer is rotated by an angle alpha along the Z-axis of the X-cut lithium niobate wafer, the X-cut lithium niobate wafer front-back face judging device comprising an electromagnetic driver (1), a comparison vibrator electrode (2), an insulating column (4) and a test probe (5), the test probe (5) comprising the upper test probe (51) and the lower test probe (52) located below the upper test probe (51), and the lower test probe (52) being fixedly connected with the comparison vibrator electrode (2) through the insulating column (4); An electromagnetic driver (1) in the X-cut lithium niobate wafer front-back face judging device is used to exert low-frequency alternating force on the X-cut lithium niobate wafer, and the X-cut lithium niobate wafer generates alternating electric charges, and the measured output voltage of the X-cut lithium niobate wafer is obtained; The longitudinal piezoelectric strain constant of the X-cut lithium niobate wafer is calculated according to the measured output voltage of the X-cut lithium niobate wafer. Based on the longitudinal piezoelectric strain constant of the X-cut lithium niobate wafer, the front and back surface state of the X-cut lithium niobate wafer is determined, and the front and back surface state is that the +X surface of the X-cut lithium niobate wafer faces up or the -X surface of the X-cut lithium niobate wafer faces up, wherein if the longitudinal piezoelectric strain constant d 33 of the X-cut lithium niobate wafer is a positive value, it is determined that the +X surface of the X-cut lithium niobate wafer faces up, and if the longitudinal piezoelectric strain constant d 33 of the X-cut lithium niobate wafer is a negative value, it is determined that the -X surface of the X-cut lithium niobate wafer faces up.

2. The X-cut lithium niobate wafer front-back face judging method according to claim 1, wherein the angle alpha is 30-60 degrees.

3. The X-cut lithium niobate wafer front-back face judging method according to claim 2, wherein V1 is the measured output voltage of the X-cut lithium niobate wafer, h is the thickness of the X-cut lithium niobate wafer, and D is the mechanical strain coefficient.

4. The X-cut lithium niobate wafer front-back face judging method according to claim 1, wherein the X-cut lithium niobate wafer front-back face judging device comprises a measured vibrator parallel capacitor C1, one end of the measured vibrator parallel capacitor C1 is connected with the upper test probe (51), and the other end of the measured vibrator parallel capacitor C1 is connected with the lower test probe (52). The longitudinal piezoelectric strain constant d of the X-cut lithium niobate wafer is calculated by using the measured output voltage V1 of the X-cut lithium niobate wafer 33 : d 33 = V1 / (h x D), 5. The X-cut lithium niobate wafer front-back face judging method according to claim 1, wherein the comparison vibrator electrode (2) comprises a comparison vibrator upper electrode (21) and a comparison vibrator lower electrode (22), and the comparison vibrator (3) is fixedly arranged between the comparison vibrator upper electrode (21) and the comparison vibrator lower electrode (22). The processor executes the program to realize the steps of the method in any one of claims 1 to 5. The computer program is executed by the processor to realize the steps of the method in any one of claims 1 to 5. ​ ​ 6. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, ​ 7. A computer readable storage medium having stored thereon a computer program, characterized in that ​

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