TWI672492B - Inspection method and inspection device for hexagonal crystal single crystal substrate - Google Patents

Abstract

An object of the present invention is to provide a method and an apparatus for inspecting a hexagonal crystal single crystal that can accurately detect a direction in which an off-angle is formed (that is, a direction in which the c-axis is inclined). The solution is an inspection method of a hexagonal crystal single crystal substrate that detects the direction in which the c-axis is inclined with respect to the vertical line of the upper surface. The method is a laser beam generating mechanism for preparing a linearly polarized laser beam, and the linearly polarized laser beam It has a wavelength that penetrates a hexagonal crystal single crystal substrate and a polarizing surface in a predetermined direction. Then, the upper surface of the hexagonal crystal single crystal substrate is maintained to be positioned vertically with respect to the optical path of the laser beam, and the laser beam is made to penetrate the hexagonal crystal single crystal substrate, and the hexagonal crystal single crystal substrate is opposed to the laser beam. The polarization plane of the laser beam generated by the generating mechanism is relatively rotated with the center of the laser beam as a rotation center, and the laser beam that has penetrated the hexagonal crystal single crystal substrate is divided into P-polarized light and S-polarized light. It further includes a calculation step and a tilt detection step. This calculation step uses a first light receiving element that measures the amount of P-polarized light split by the polarized beam splitter and a second light receiving element that measures the amount of S-polarized light. The ratio of the light quantity measured by the first light-receiving element and the second light-receiving element. The inclination detection step is to calculate the relative rotation angle of the hexagonal crystal single crystal substrate with respect to the polarization plane of the laser beam, and the angle calculated by the calculation step. The light quantity ratio is compared and displayed, and the direction in which the c-axis is inclined with respect to the vertical line of the upper surface is detected.

Description

Inspection method and inspection device of hexagonal crystal single crystal substrate Field of invention

The invention relates to an inspection method and an inspection device of a hexagonal crystal single crystal substrate such as a SiC substrate and a GaN substrate.

Background of the invention

Optical devices such as power devices, LEDs, and LDs are formed on the surface area layer of a wafer using hexagonal single crystals of SiC, GaN, and other materials as a material, and are formed by forming a plurality of divided predetermined line divisions in a grid shape. Functional layer of the layer.

The wafer on which the device is formed is generally produced by slicing an ingot with a wire saw, and polishing the front and back surfaces of the sliced wafer to produce a mirror surface (see, for example, Japanese Patent Laid-Open No. 2000-94221).

The hexagonal crystal single crystal substrate has a first orientation plane and a second orientation plane orthogonal to the first orientation plane. For example, the length of the first orientation plane may be shorter than the length of the second orientation plane.

The hexagonal crystal single crystal substrate has a c-axis that is inclined at an off-angle α from the vertical line of the upper surface in the direction of the first orientation plane, and a c-plane orthogonal to the c-axis. The c-plane is inclined at an off-angle α with respect to the upper surface of the substrate. Generally, in a hexagonal crystal single crystal substrate, a square orthogonal to the elongation direction of the short first orientation plane To the tilt direction of the c-axis.

In the hexagonal crystal single crystal substrate, the c-plane is set to an infinite number at the molecular level of the substrate. The deflection angle α is freely set in a range of, for example, 1 ° to 6 °, and a substrate is manufactured.

Prior art literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. 2000-94221

Summary of invention

As described above, in the hexagonal crystal single crystal substrate, the substrate is manufactured such that the direction orthogonal to the elongation direction of the shorter first orientation plane is the oblique direction of the c-axis. However, due to manufacturing errors, the orientation plane may be manufactured with an error of about ± 5 ° with respect to the direction orthogonal to the tilt direction of the c-axis direction. Therefore, there is a problem that desired processing cannot be performed after processing with the orientation plane as a reference.

The present invention has been made in view of such problems, and an object thereof is to provide an inspection method and inspection of a hexagonal crystal single crystal substrate that can accurately detect a direction in which an off-angle is formed (that is, a tilt direction of a c-axis). Device.

The invention according to the first aspect is to provide a method for inspecting a hexagonal crystal single crystal substrate, the hexagonal crystal single crystal substrate having a first surface and a second surface opposite to the first surface, from the first surface to The c-axis of the second surface, and A c-plane orthogonal to the c-axis, and the inspection method of the hexagonal crystal single crystal substrate is to detect a direction in which the c-axis is inclined with respect to a vertical line of the first surface. A laser beam generating mechanism for a laser beam, and the linearly polarized laser beam has a wavelength that penetrates a hexagonal crystal single crystal substrate and a polarizing plane in a predetermined direction; a holding step that holds the first surface of the hexagonal crystal single crystal substrate Positioned perpendicular to the optical path of the laser beam, and allowing the laser beam to penetrate the hexagonal crystal single crystal substrate; the rotation step causes the hexagonal crystal single crystal substrate to be polarized with respect to the laser beam generated by the laser beam generating mechanism Plane, rotates relatively with the center of the laser beam as the rotation center; the branching step divides the laser beam that has penetrated the hexagonal crystal single crystal substrate into a polarized beam splitter into P polarized light and S polarized light; a calculation step, the amount of use The first light receiving element that measures the amount of P-polarized light split by the polarized beam splitter and the second light receiving element that measures the amount of S-polarized light, and calculates the first light receiving element and the second light receiving The light quantity ratio of the light quantity measured by the element; and the tilt detection step, comparing and displaying the relative rotation angle of the hexagonal crystal single crystal substrate with respect to the polarization plane of the laser beam with the light quantity ratio calculated by the calculation step While detecting the direction in which the c-axis is inclined with respect to the vertical line of the first surface.

Ideally, it is further provided with an orientation plane detection step for detecting the orientation plane of the hexagonal crystal single crystal substrate in the rotation step, and In the plane detection step, the rotation angle at which the peak value of the light amount ratio appears at a rotation angle that is similar to the rotation angle at which the orientation plane is detected is taken as the direction in which the c-axis is inclined.

According to the invention described in item 3, there is provided an inspection device for a hexagonal crystal single crystal substrate, the hexagonal crystal single crystal substrate having a first surface and a second surface opposite to the first surface, from the first surface to The c-axis of the second surface and the c-plane orthogonal to the c-axis, the inspection device for the hexagonal crystal single crystal substrate detects a direction in which the c-axis is inclined with respect to a vertical line of the first surface, and is characterized in that: : The laser beam generating mechanism generates a linearly polarized laser beam, and the linearly polarized laser beam has a wavelength that penetrates the hexagonal crystal single crystal substrate and a polarization plane in a predetermined direction; a holding mechanism converts the hexagonal crystal single crystal substrate The first surface of is maintained to be positioned vertically with respect to the optical path of the laser beam generated by the laser beam generating mechanism, and the laser beam penetrates the hexagonal crystal single crystal substrate; the rotation mechanism makes the hexagonal crystal single crystal substrate opposite to The polarizing surface of the laser beam generated by the laser beam generating mechanism is relatively rotated with the center of the laser beam as a rotation center; the polarization beam splitter splits the laser beam that has penetrated the hexagonal crystal single crystal substrate. The P polarized light and S-polarized light; a first light receiving element, measurement of light amount P polarized light of to the polarizing beam splitter being imprisoned by; the second light receiving element, measuring the amount of light polarization them with the divergence of the polarization beam splitter S by; A calculation mechanism calculates a light quantity ratio of the light quantity measured by the first light receiving element and the second light receiving element; and a display mechanism that will act as a hexagonal crystal single crystal with respect to the polarization plane of the laser beam by the operation of the rotation mechanism. The relative rotation angle of is compared with the light amount ratio calculated by the calculation mechanism and displayed.

Preferably, a detection mechanism for detecting an orientation plane of a hexagonal crystal single crystal substrate is further provided, and the display mechanism uses a rotation angle of a peak value of a light amount ratio that appears at a rotation angle similar to the rotation angle of the detected orientation plane as c The axis is tilted.

According to the present invention, the first surface is positioned vertically with respect to the laser beam, so that the c-plane of the hexagonal crystal single crystal substrate inclined at an off-angle with respect to the first surface is a polarizing surface of the laser beam and refracted, and The refraction direction is changed by the rotation of the opposite hexagonal crystal single crystal substrate, whereby the light amount ratio of the P-polarized light and the S-polarized light divided by the polarizing beam splitter is changed as a sinusoid according to the rotation angle, and the most The angular position of the peak or trough of the sine curve near the angular position of the orientation plane is detected as the direction of the tilt of the c-axis with respect to the vertical line of the first surface.

Therefore, if the angular position of the orientation plane is consistent with the angular position of the crest or trough of the sinusoidal curve, the orientation plane can be trusted to perform processing. The angular difference is used as a correction value for the orientation plane, and processing is performed to perform the desired processing.

10‧‧‧Hexagonal crystal single crystal substrate inspection device

11‧‧‧Hexagonal crystal single crystal substrate (SiC substrate)

11a‧‧‧First side (upper surface)

11b‧‧‧ 2nd side (back)

12‧‧‧ base

13‧‧‧The first orientation plane

14‧‧‧ holding table

15‧‧‧ 2nd orientation plane

22‧‧‧ Motor

24‧‧‧ Pinion

26‧‧‧Gear

28‧‧‧ scale

30‧‧‧Rotary encoder

32‧‧‧He-Ne laser oscillator

34‧‧‧1 / 2 wavelength plate

36‧‧‧Polarization separation film

38‧‧‧ Polarized Beamsplitter

40‧‧‧1st light receiving element

42‧‧‧ 2nd light receiving element

44‧‧‧directional plane detector

46‧‧‧Calculation Agency

50‧‧‧Monitor (display mechanism)

α, β‧‧‧ declination

P1, P2, P3, P4‧‧‧ peak

R1‧‧‧arrow

FIG. 1 is a perspective view of an inspection device for a hexagonal crystal single crystal substrate according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a vertical line on a first surface of a hexagonal crystal single crystal substrate and a c-axis.

FIG. 3 is a perspective view illustrating an inspection method performed by the inspection device shown in FIG. 1.

FIG. 4 is a plan view illustrating a method of detecting an orientation plane.

FIG. 5 is a graph showing a light amount ratio of P-polarized light to S-polarized light with respect to a rotation angle.

Forms used to implement the invention

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a perspective view of an inspection device 10 for a hexagonal crystal single crystal substrate according to an embodiment of the present invention is shown. The inspection apparatus 10 includes a base 12.

A holding table 14 is rotatably mounted on the base 12. The holding table 14 has a central opening 16 and an annular suction groove 18. A plurality of suction holes 20 are opened in the annular suction groove 18. The suction hole 20 is selectively connected to a suction source (not shown) through an electromagnetic switching valve.

A motor 22 is mounted on the base 12, and a pinion gear 24 fixed to an output shaft of the motor 22 is meshed with a gear 26 formed at a lower end portion of the holding table 14. A scale 28 for detecting a rotation angle is arranged on the outer periphery of the holding table 14.

The rotation angle of the holding table 14 is detected by reading the scale 28 with the rotary encoder 30 mounted on the base 12. Here, although the angular resolution of the rotary encoder 30 used is 0.5 °, it is also possible to use Rotary encoder with parsing capabilities.

Reference numeral 44 is an orientation plane detector, and for example, the following detectors can be used: a laser beam is emitted to detect the orientation plane 13 or 15 from the hexagonal crystal single crystal substrate 11 attracted and held on the holding table 14 as shown in FIG. 2. Laser detectors for reflected light, or ultrasonic detectors that detect reflected waves that have been generated.

32 is a He-Ne laser oscillator, which oscillates and generates a laser beam with a wavelength of 632nm. Although the He-Ne laser oscillator of this embodiment oscillates to produce a laser beam with an average output of 0.1 W, the output is not limited to this. He-Ne laser oscillations that generate other output laser beams by oscillation may also be used. Instead of the He-Ne laser oscillator 32, other types of laser oscillators that oscillate and generate laser beams with different wavelengths may be used.

A half-wavelength plate 34 is mounted between the He-Ne laser oscillator 32 and the hexagonal crystal single crystal substrate 11 held on the holding table 14. In this embodiment, a He-Ne laser oscillator 32 and a half-wavelength plate 34 constitute a laser beam generating mechanism capable of generating a laser beam having a polarization plane with a predetermined direction.

38 is a polarization beam splitter having a polarization separation film 36, and a first light receiving element 40, such as a photodiode, which detects a P-polarized laser beam that penetrates the polarization separation film 36, and a detection beam polarization detector 36 A second light receiving element 42 such as a photodiode of the reflected S-polarized laser beam. The outputs of the first light-receiving element 40 and the second light-receiving element 42 are input to the calculation mechanism 46 shown in FIG. 3.

Next, the relationship between the c-axis of the hexagonal crystal single crystal substrate 11 and the orientation plane 13 will be described with reference to FIG. 2. Hexagonal crystal single crystal substrate 11 can use SiC The substrate or the GaN substrate will be described below using a substrate using the SiC substrate 11.

The SiC substrate 11 has a first surface (upper surface) 11a and a second surface (back surface) 11b opposite to the first surface. The upper surface 11a of the substrate 11 is a mirror surface polished to become an irradiation surface of a laser beam.

The SiC substrate 11 includes a first alignment plane 13 and a second alignment plane 15 that is orthogonal to the first alignment plane 13. The length of the first orientation plane 13 is shorter than the length of the second orientation plane 15.

The SiC substrate 11 has a c-axis 19 which is inclined at an off-angle α from the vertical line 17 of the upper surface 11 a in the direction of the first orientation plane 13, and a c-plane (not shown) orthogonal to the c-axis 19. The c-plane is inclined at an off-angle α with respect to the upper surface 11 a of the SiC substrate 11. In general, in the SiC substrate 11, a direction orthogonal to the elongation direction of the short first alignment plane 13 is an oblique direction of the c-axis 19.

The c-plane in the substrate 11 is set to an infinite number at the molecular level of the substrate 11. In this embodiment, the deflection angle α is set to 4 °. However, the deflection angle α is not limited to 4 °, and the SiC substrate 11 can be freely set within a range of, for example, 1 ° to 6 °.

As described above, although the first orientation plane 13 and the second orientation plane 15 are formed so that the inclination direction of the c-axis 19 and the elongation direction of the first orientation plane 13 are orthogonal, there may be a manufacturing error of the substrate 11 and there may be In the following case, the inclination direction of the c-axis is not necessarily strictly orthogonal to the elongation direction of the first orientation plane 13 and deviates from the orthogonal direction at a very small angle, for example, about 1 ° to 2 °.

In such a case, when the processing is performed based on the elongation direction of the first orientation plane 13, the desired processing may not be performed in some cases. Problem. The present invention solves this problem by strictly inspecting the direction of the deflection angle α of the c-axis 19 inclined with respect to the elongation direction of the first orientation plane 13.

Next, the inspection method according to this embodiment will be described in detail with reference to FIG. 3. In the following description, an example is described in which a SiC substrate is used as a hexagonal crystal single crystal substrate 11 and the deflection angle α is 4 ° with respect to the vertical line 17 of the upper surface 11 a of the SiC substrate 11.

The suction hole 20 of the holding stage 14 is connected to a suction source so that the holding stage 14 sucks and holds the SiC substrate 11 already placed on the holding stage 14. Then, the He-Ne laser oscillator 32 is operated, and the He-Ne laser oscillator 32 is oscillated to generate a laser beam with a wavelength of 632 nm and an average output of 0.1 W. The polarization plane is rotated by a 1/2 wavelength plate 34, and The laser beam is converted into a P-polarized laser beam, and irradiates the first surface (upper surface) 11 a of the SiC substrate 11 held on the holding table 14 vertically.

While irradiating the laser beam, the motor 22 is driven to rotate the holding table 14 holding the SiC substrate 11 in the direction of the arrow R1. The laser beam that has penetrated the SiC substrate 11 is a polarization beam splitter (PBS) 38, and is split into a P-polarized laser beam that penetrates the polarization separation film 36 and an S-polarized laser that is reflected by the polarization separation film 36. beam.

The P-polarized laser beam is detected by the first light receiving element 40, and the S-polarized laser beam is detected by the second light receiving element 42. The light amount of the P-polarized laser beam detected by the first light receiving element 40 is converted into, for example, a voltage value, and is input to the calculation mechanism 46. The light amount of the S-polarized laser beam detected by the second light receiving element 42 is Will be converted to, for example, a voltage value and input to a computer 建 46.

The calculation mechanism 46 calculates the ratio of the amount of P-polarized light detected by the first light-receiving element 40 to the amount of S-polarized light detected by the second light-receiving element 42, that is, (the amount of P-polarized light) / (Light quantity of S polarized light). Then, the calculation result is displayed on a monitor (display mechanism) 50 as shown in FIG. 5.

The light quantity ratio displayed on the display mechanism 50 has a sinusoidal curve because the refractive index in the c-axis 19 direction is different from the refractive index in the c-plane direction, and appears in four directions while rotating the SiC substrate 11 by one turn. Peak. That is, as shown in FIG. 5, four peaks P1 to P4 appear in a range of 360 °.

On the other hand, the rotation angle when the first orientation plane 13 is detected by the orientation plane detector 44 during the rotation of the SiC substrate 11 is 42.5 ° as shown in FIG. 5.

Since the SiC substrate 11 is manufactured so that the first orientation plane 13 is orthogonal to the direction in which the deflection angle α is formed (that is, the direction in which the c-axis 19 is inclined with respect to the vertical line 17 of the upper surface 11a of the substrate 11), The rotation angle (the rotation angle of 44 ° in this embodiment) at which the peak value P1 of the light quantity ratio appears from the rotation angle of the first orientation plane 13 approximately 42.5 ° is determined as the direction in which the c-axis 19 is inclined.

Therefore, as shown in FIG. 4, the direction of the deflection angle of the vertical line 21 with respect to the first orientation plane 13 (that is, the direction β in which the c-axis 19 is inclined) is calculated as 42.5 ° -44 ° = -1.5 °. Accordingly, as long as the vertical line 21 of the first orientation plane 13 is processed with a correction value of -1.5 °, a desired processing can be performed.

Furthermore, when an S-polarized laser beam is irradiated onto the SiC substrate 11 Later, (the amount of light of P polarized light) / (the amount of light of S polarized light) appears as a trough of a sinusoidal curve. Therefore, in this case, the calculation mechanism 46 calculates (the amount of light of P polarized light) / (the amount of light of S polarized light) so that the c-axis direction appears near the bottom of the trough of the sine curve.

When the deflection angle α is 0, that is, when the vertical line 17 of the upper surface 11a of the SiC substrate 11 coincides with the c-axis 19, in the case where the laser beam of P polarization has been irradiated on the SiC substrate 11, regardless of the rotation angle , Both make (the amount of light of P polarized light) / (the amount of light of S polarized light) fixed, and are about 2.

In the above-mentioned embodiment, although the laser beam is irradiated with P-polarized light while the holding table 14 holding the SiC substrate 11 is rotated, the holding table 14 may be fixed without rotating it. While irradiating the laser beam on the SiC substrate 11 already held on the holding table 20 while rotating the 1/2 wavelength plate 34. In this case, the light amount ratio of the P-polarized light and the S-polarized light also forms a sinusoidal curve, and the c-axis appears at the rotation angle of the peak of the sinusoidal curve.

Claims (4)

An inspection method of a hexagonal crystal single crystal substrate, the hexagonal crystal single crystal substrate having a first surface and a second surface opposite to the first surface, a c-axis from the first surface to the second surface, and and The c-plane orthogonal to the c-axis, and the inspection method of the hexagonal crystal single crystal substrate is to detect the direction in which the c-axis is inclined with respect to the vertical line of the first surface. A laser beam generating mechanism for a radiating beam, and the linearly polarized laser beam has a wavelength that penetrates a hexagonal crystal single crystal substrate and a polarization plane in a predetermined direction; a maintaining step of maintaining the first surface of the hexagonal crystal single crystal substrate as Positioned perpendicular to the optical path of the laser beam, and allowing the laser beam to penetrate the hexagonal crystal single crystal substrate; the rotation step causes the hexagonal crystal single crystal substrate to be polarized with respect to the laser beam generated by the laser beam generating mechanism , With the center of the laser beam as the rotation center and rotate relatively; the branching step divides the laser beam that has penetrated the hexagonal crystal single crystal substrate into a polarized beam splitter into P polarized light and S polarized light; the calculation step uses The first light receiving element that measures the amount of P-polarized light split by the polarized beam splitter and the second light receiving element that measures the amount of S-polarized light, and calculates the light amounts measured by the first and second light receiving elements. A light amount ratio; and an inclination detection step of comparing a relative rotation angle of a hexagonal crystal single crystal substrate with respect to a polarization plane of the laser beam with the calculation step The calculated light quantity ratio is compared and displayed, and the direction in which the c-axis is inclined with respect to the vertical line of the first surface is detected. For example, the inspection method for a hexagonal crystal single crystal substrate of claim 1 further includes an orientation plane detection step for detecting the orientation plane of the hexagonal crystal single crystal substrate in the rotation step, and in the orientation plane detection step, The rotation angle at which the peak value of the light quantity ratio appears from the rotation angle approximating the rotation angle of the orientation plane is taken as the direction in which the c-axis is inclined. An inspection device for a hexagonal crystal single crystal substrate, the hexagonal crystal single crystal substrate having a first surface and a second surface opposite to the first surface, a c-axis from the first surface to the second surface, and The c-axis is orthogonal to the c-plane, and the hexagonal crystal single crystal substrate inspection device detects a direction in which the c-axis is inclined with respect to a vertical line of the first surface, and is characterized by including a laser beam generating mechanism that generates linearly polarized light. Laser beam, and the linearly polarized laser beam has a wavelength that penetrates the hexagonal crystal single crystal substrate and a polarization plane in a predetermined direction; a holding mechanism that maintains the first surface of the hexagonal crystal single crystal substrate relative to the laser The optical path of the laser beam generated by the laser beam generating mechanism is vertically positioned, and the laser beam penetrates the hexagonal crystal single crystal substrate; the rotation mechanism makes the hexagonal crystal single crystal substrate relative to the laser generated by the laser beam generating mechanism. The polarizing surface of the beam is rotated relatively with the center of the laser beam as the rotation center; the polarizing beam splitter divides the laser beam that has penetrated the hexagonal crystal single crystal substrate into P-polarized light and S-polarized light; The first light-receiving element measures the amount of P-polarized light split by the polarized beam splitter; the second light-receiving element measures the amount of S-polarized light split by the polarized beam splitter; a calculation mechanism that calculates the first light A light quantity ratio between the light quantity measured by the element and the second light receiving element; and a display mechanism that rotates the relative rotation angle of the hexagonal crystal single crystal with respect to the polarization plane of the laser beam by the operation of the rotation mechanism, and The light amount ratio calculated by this calculation means is compared and displayed. For example, the inspection device for a hexagonal crystal single crystal substrate of claim 3 further includes a detection mechanism for detecting an orientation plane of the hexagonal crystal single crystal substrate, and the display mechanism is based on a rotation angle similar to the rotation angle of the detected orientation plane. The rotation angle of the peak value of the apparent light quantity ratio is displayed as the direction in which the c-axis is inclined.