JPS5947254B2 - Single crystal cutting plane deviation angle measurement method - Google Patents

Description

Detailed Description of the Invention For example, a crystal resonator used in a communication device or a reference oscillator for obtaining a time reference, or a crystal or other single crystal plate for obtaining a semiconductor electric device, is made of a crystal with a predetermined surface index. It is necessary to cut at a certain angle with a certain orientation to the lattice plane.

An X-ray diffraction phenomenon is used to measure the angle between a cut plane of a single crystal and a crystal lattice plane. Conventionally, the direction of inclination of the crystal lattice plane with respect to the cut surface was determined by measurement, and the angle at which diffraction occurred was determined by making X-rays incident on the cut surface of the sample from that direction and simultaneously changing the incident angle. . Therefore, if there is an error in the above measurements, there is a risk that a good product may be treated as a defective product or a defective product may be treated as a non-defective product, and in order to indicate the direction of inclination during measurement, the sample should be shaped into a square or rectangle with parallel sides. It was necessary to cut one or two corners diagonally to provide further direction. For this reason, there have been drawbacks such as a poor utilization rate of the sample when manufacturing a resonator or the like by cutting out a plate-like sample into a predetermined shape. The present invention provides a measuring method that does not have the above-mentioned drawbacks and can simplify the mechanism of the measuring device. Figure 1 shows an example of a single crystal sample cut into a rectangular plate, with crystal lattice plane 1 and cut plane 2.
have deviation angles ε and η in a plane that includes two adjacent sides of the sample and is orthogonal to the cut surface 2, respectively.

In other words, when the normal line to the cut plane passing through approximately the center of the sample is 3, the crystal lattice plane 1 is inclined in a plane including this normal line 3 and the straight line 4 on the cut plane. The inclination angle and therefore the deviation angle δ between the crystal lattice plane 1 and the fold plane 2
It is used to measure. For example, in an AT-cut crystal resonator, even if η is exactly the predetermined angle 2058', the inclination angle δ will be larger than η unless ε is 0. ε
is 15', δ becomes 3 larger than η. FIG. 2 is a schematic vertical cross-sectional view showing the configuration of a measurement system according to the method of the present invention for the sample 5 as described above, and FIG. 3 is a plan view thereof.

In this way, divergent X-rays are projected from the X-ray source 6 through the slit T in a plane including the normal line 3 passing through approximately the center of the sample 5,
The divergent X-rays are made incident on the cut surface 2 of the sample. The X-ray source 6 is in the form of a short line segment perpendicular to the normal line 3, and the slit T is also perpendicular to the normal line 3. Therefore, the maximum incident angle of X-rays incident on the cut surface 2 of the sample is ctl,
The minimum incident angle is α2, and in this state, the sample 5 is rotated about the normal line 3 as indicated by the arrow φ. In addition, an X-ray detector 8 is provided within a plane including the normal line 3 and the X-rays incident on the sample surface to detect X-rays diffracted by the cut surface of the sample. That is, when the diffraction angle of X-rays by the crystal lattice plane 1 is 2θ0, the X-ray source 6 is arranged so that the angle formed by two straight lines connecting the center of the cut surface of the sample, the X-ray source 6, and the detector 8 is 2θo. and a detector 8 are arranged.
In such a measurement system, X with respect to the cut surface 2 of the sample
If the incident angle of the line is α, the deviation angle between the cut plane 2 and the crystal lattice plane 1 is δ, and the rotation angle about the normal 3 of the cut plane 2 is ψ, Black's diffraction conditions are as follows. , if the deviation angle δ is within a few degrees, it can be expressed as with very good approximation.

Therefore, assuming that the minimum incident angle α2 is sufficiently small,
In the range where the conditions during rotation of sample 5 are satisfied, α is applied to the cut surface.
A part of the X-rays incident at each incident angle in the range from 2 to (: tl) satisfies the diffraction condition of equation (2) and is detected by the detector 8. This is a curve showing the relationship of equation (2). When the deviation angle δ between the cut plane 2 and the crystal lattice plane 1 changes, the curve becomes like the broken lines B and C. In other words, the above curve becomes the maximum and Diffracted X-rays are detected in the rotation angle range from -φ1 to +ψ1, which falls between the minimum incident angles D and D2.The intensity of the detected X-rays is almost related to the rotation angle of the sample. Therefore, the relationship between deflection intensity s and rotation angle ψ is expressed in Figure 4b. Therefore, if curve A in Figure 4a changes as shown in B and C due to a change in deviation angle δ, the diffracted X-ray The detected rotation angle range W is w'
, W'. Figure 5 shows the waveform of Figure 4b that is actually observed, but as mentioned above, its width W
changes depending on the deviation angle δ, so the deviation angle δ can be known from this width. In addition, in order to find the width W,
For example, you can rotate the sample at a constant speed and measure the time from when the detector starts sending output to when the output disappears, or you can calculate the total number of output pulses from the detector during the above period or convert it to a capacitor. There are various methods such as a method of accumulating the charges and calculating the area surrounded by the curve and the horizontal axis in FIG. 5. As explained above, the present invention allows the deviation angle between the crystal lattice plane and the cut plane of the sample to be determined without knowing in advance the inclination direction of the crystal lattice plane with respect to the cut plane of the sample.

Therefore, in order to measure the angle of inclination, it is not necessary to first determine the direction of inclination and then to precisely place the sample in a predetermined orientation, which is a complicated operation, and it is possible to prevent erroneous measurements due to errors in this operation. Moreover, since there is no need to cut off the corners of the rectangular plate in order to display the inclination direction for each sample, the utilization rate of the sample is improved. Moreover, since the sample is simply rotated around one axis, measurements can be performed using a device with a simple mechanism.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a sample, FIG. 2 is a schematic vertical cross-sectional view of a measurement system according to the method of the present invention, and FIG. 3 is a plan view thereof.
FIG. 4 is a diagram explaining the principle of the present invention, and FIG. 5 is an example of an observed curve.

Claims (1)

[Claims] 1. Rotate the single crystal sample whose deviation angle between the crystal lattice plane and the cut plane is to be measured around the normal to the cut plane, irradiate the cut plane with divergent X-rays, and perform diffraction at the cut plane. A detector for diffracted X-rays is provided, and the detector detects diffracted X-rays.
A single crystal cutting plane deviation angle measurement method characterized by observing the rotation angle range of a sample in which a line is detected.