JP2567840B2 - Crystal orientation determination device - Google Patents

Description

The present invention relates to a crystal orientation determination apparatus for determining the crystal orientation of a single crystal sample such as silicon or quartz by using X-ray diffraction. .

(Prior Art) In order to use a single crystal such as silicon or quartz as an industrial product such as a semiconductor or an oscillator, it is necessary to cut it so that its surface forms a specific angle with respect to a crystal lattice plane. Therefore, it is necessary to know the crystal lattice plane of the sample, but the most commonly used crystal lattice plane determination method is to use X-ray diffraction. The method for determining the crystal lattice plane of the sample using this X-ray diffraction is shown in FIG. That is, when an X-ray is incident on the sample 2, the X-ray is diffracted by the atom A when the incident angle of the X-ray becomes a certain angle θ. The angle at this time is called a diffraction angle, and the angle θ is obtained by the following (1).

nλ = 2d sinθ (1) n = 1,2,3, ... Integer λ = wavelength of X-ray (Å) d = lattice spacing (Å) θ = diffraction angle (degree) Therefore, generally, for semiconductor substrates Silicon or the like grows a seed crystal to form an ingot-shaped single crystal. Conventionally, the goniometer shown in FIG. 4 utilizing X-ray diffraction has been used to measure the crystal lattice plane in the longitudinal direction of the ingot. There is.

In this conventional goniometer, the point where the center of the incident X-ray flux of the X-ray tube 1 is the surface of the sample ingot 2 is the goniometer center P, and the line connecting the center of the incident X-ray flux and the goniometer center P is taken as the x-axis. The axis that passes through P and is perpendicular to this x-axis is the y-axis. If the radius of the ingot 2 is r, then from the goniometer center P, X [= rsin θ], Y [= rc
osθ] is the center O of the ingot. Then, the ingot 2 is rotated by the sample rotating mechanism 3 with the center of the ingot as an axis. Further, in the goniometer, the X-ray detector 4 is arranged around the rotation center P so as to be rotatable by a predetermined angle.

In such a conventional crystal orientation determination apparatus, the X-ray detector 4 is first installed at a position of 2θ with respect to the diffraction angle (θ), and the incident X-ray beam is irradiated from the X-ray tube 1 onto the surface of the sample 2. While doing so, the sample 2 is rotated around the center O of the ingot. Then, when the crystal lattice plane of the sample ingot 2 becomes θ degrees with respect to the X axis, the detector 4 installed at a position of 2 degrees toward the goniometer center P detects the diffracted X-rays and detects the maximum X-ray intensity. Indicates. Therefore, the rotation position of the ingot 2 when the maximum X-ray intensity is shown is determined to be the crystal lattice plane.

However, in such a conventional crystal orientation determination apparatus, since the rotation center O of the sample ingot is located at a position different from the rotation center P of the goniometer, in addition to the incident X-ray flux center and the goniometer center, The positional relationship with the center of rotation of the sample must also be set accurately.
Furthermore, since the center of rotation of the sample is determined by the two elements of XY as shown in FIG. 4, an XY table is usually used as such an XY axis position determining mechanism. If the angle is not perfect, X and Y cannot be set independently. However, for example, when a silicon ingot of 8 inches x 650 mm is used as a sample, its weight becomes about 50 kg.

Therefore, as described above, in addition to the goniometer rotation mechanism, a highly accurate ingot rotation and X, Y direction movement mechanism is required, but the ingot rotation mechanism has small eccentricity, and the rotation center axis is the same as the rotation center axis of the goniometer. It is necessary to maintain a high degree of parallelism, and also for the XY table, it is necessary to maintain high X-axis and Y-axis right angle accuracy, and to set the X and Y dimensions with high accuracy. Therefore, it is extremely difficult to realize a mechanical structure for determining the position of a sample having a weight of about 50 kg with high accuracy as described above, and there is a problem that an error occurs. Moreover, when efforts are made to minimize the error, there is a problem that the mechanism becomes complicated and large.

(Problems to be Solved by the Invention) In the conventional crystal orientation determination apparatus as described above, since the rotation center of the sample is located at a position different from the rotation center of the goniometer, the incident X-ray flux center and the goniometer are In addition to the center, the positional relationship between the goniometer center and the sample center must be set accurately, and a complicated X and Y axis moving table is used for the position determining mechanism of the sample center. There was a problem to turn.

The present invention has been made in view of such a conventional problem, and provides a crystal orientation determination apparatus that simplifies a mechanism for setting the positional relationship of each component and enables miniaturization. With the goal.

[Structure of the Invention] (Means for Solving Problems) From an X-ray source that emits X-rays irradiated to a sample, a collimator that determines the traveling direction of an X-ray flux emitted from this X-ray source, and this collimator A goniometer having an X-ray detector for detecting a diffracted X-ray that is incident on the surface of the sample, the X-ray flux emitted at a predetermined angle, and the sample is mounted so that the central axis is common to the goniometer. A sample stage having a sample rotation mechanism for rotating the mounted sample by a predetermined angle, and the X-ray source and the collimator are rotated by a predetermined angle around the center of the X-ray source to determine the traveling direction of the X-ray flux. A radiation source rotation mechanism, a detector rotation mechanism that rotates the X-ray detector around a center of a detection surface of the X-ray detector, and a predetermined angle around the center of the goniometer. With line detector ; And a rotating mechanism for rotating at least one, and to rotate each independently and said X-ray source and an X-ray detector samples.

(Operation) In the crystal orientation determination device of the present invention, the center of the sample is aligned with the center of the goniometer, the X-ray tube or the detector is rotated around the center of the goniometer by a predetermined angle, and the X-ray tube angle setting mechanism is further provided. The X-ray tube is rotated by a predetermined angle by the detector, the detector is rotated by the detector angle setting mechanism by a predetermined angle, and the incident X-ray flux from the X-ray tube is incident on the surface of the sample at a predetermined diffraction angle. The crystal lattice plane of the sample is determined by setting the incidence on the detector, rotating the goniometer or the sample around its rotation center in this state, and detecting the maximum amount of the diffracted X-rays by the detector.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 1 shows an embodiment of the X-ray tube 11 and the X-ray tube.
In the goniometer 13 including the line detector 12, a rotating mechanism 14 including a worm / worm gear mechanism is provided so that the X-ray detector 12 rotates about the goniometer center P by a desired angle.
Is provided. The X-ray detector 12 is attached to the rotating mechanism 14 via the rotating arm 21, and the X-ray detector 12 can be rotated around the goniometer center P together with the rotating arm 21 by rotating the rotating mechanism 14. Of.

Also, on the goniometer 13, replace the X-ray tube 11 with the X-ray tube.
An X-ray tube angle setting mechanism 15 consisting of a worm / worm gear mechanism for rotating the center Q of 11 by a predetermined angle, and an X-ray detector 12 is rotated by a predetermined angle around the center R of the detection surface of the detector 12. A detector angle setting mechanism 16 including a worm / worm gear mechanism is provided.

The sample stage 17 having the same central axis as the goniometer 13 is provided with a sample rotating mechanism 18 composed of a worm / worm gear mechanism similar to the mechanism shown in FIG. 4 shown as a conventional example. Sample on sample table 17 by mechanism 18
19 is rotated by a predetermined angle.

The incident X-ray flux of the X-ray tube 11 has its traveling direction determined by a collimator 20, and the X-ray tube angle setting mechanism 15
The collimator 20 is also rotated with the rotation of the X-ray tube 11, and the traveling direction of the incident X-ray flux is determined by the X-ray tube angle setting mechanism 15.

The operation of the crystal orientation determination device having the above configuration will be described next. As shown in FIG. 2, a cylindrical sample ingot 19 is placed on the sample table 17 and its center is the rotation center P of the goniometer 13.
Install it to match. Sample 19 on this sample stand 17
Is installed by a conventional method as in the conventional example shown in FIG. The diffraction angle of the sample 19 is the value θ shown in the above formula (1), the distance l _{1 from} the rotation center P to the center Q of the X-ray tube 11, and the center of the detection surface of the detector 12 from the rotation center P. When the distance to the R is l ₂ and the radius of the sample 19 is r, the X-ray tube angle setting mechanism 15 with the center of the X-ray tube 11 as the axis 15
To rotate β ₁ degree. Further, the detector 12 is rotated from the rotation center P of the goniometer 13 by β ₂ degrees by the detector angle setting mechanism 16. The rotation angles β ₁ and β ₂ are determined by the following equations (2) and (3).

Further, the X-ray detector 12 is rotated about the center P of the goniometer 13 by (2θ + β ₁ + β ₂ ) degrees from the X-axis in the clockwise direction by the rotating mechanism 14 and set to the position shown in FIG.

When the positional relationship among the X-ray tube 11, the detector 12, and the sample 19 is set in this way, the incident X-ray flux from the X-ray tube 11 is incident on the surface of the sample 19 by the collimator 20 at the diffraction angle θ of the sample 19. Will be done.

Then, by driving the sample rotation mechanism 18, the sample 19
When the crystal lattice plane is rotated with respect to the incident X-ray flux as shown in FIG. Therefore, when rotating the sample 19 while detecting the incident X-ray dose by the detector 12, when the X-ray dose indicated by the detector 12 has the maximum value, the crystal lattice plane of the sample can be determined.

In the above embodiment, the sample ingot 19 is rotated by the sample rotating mechanism 18, and the diffraction X-ray incident on the X-ray detector 12 is detected.
I tried to measure the maximum dose, but on the contrary,
Considering the case where the sample ingot is a heavy object and its rotation control is difficult, the sample 19 is placed fixed, and the X-ray tube 11 and the detector 12 are kept in the positional relationship shown in FIG. It is also possible to provide a rotation mechanism that rotates around the center P of 13. In this way, when rotating the X-ray tube and the detector, since these devices are lighter in weight than silicon or crystal ingots, the rotating mechanism can be simplified.

Further, the angle setting of the X-ray detector 12 does not have to be so strict, and it is sufficient if it is enough to know the maximum value of the incident X-ray dose. Therefore, the angle accuracy of the detector angle setting mechanism 16 is compared. The rough one is enough.

[Effect of the Invention] The present invention makes the center of the sample coincide with the center of the goniometer, and enables one of the X-ray tube and the detector to rotate by a predetermined angle with respect to the center of the goniometer by using the rotating mechanism. The X-ray detector can be rotated by a predetermined angle around the center of the radiation source, and the X-ray detector can be rotated by a predetermined angle around the center of the detection surface of the detector, and the incident X-ray flux from the X-ray tube is incident on the sample surface. So that the diffracted X-rays from the sample surface are incident on the detector, and one of the X-ray tube and the detector and the sample is rotated around the goniometer center relative to the other. It was made possible.

Therefore, since the center of the goniometer and the center of rotation of the sample are displaced as in the conventional case, an XY biaxial translation mechanism for setting the positional relationship between the center of the sample and the center of the goniometer by the radius of the sample is not required. Therefore, for heavy samples
The high-accuracy XY2-axis control mechanism required for XY2-axis movement can be omitted, the entire device can be simplified, and the size and cost can be reduced.

[Brief description of drawings]

FIG. 1 is a mechanism diagram of an embodiment of the present invention, FIG. 2 is an operation explanatory diagram of the above embodiment, FIG. 3 is an explanatory diagram of X-ray diffraction phenomenon of a sample, and FIG. 4 is a mechanism diagram of a conventional example. is there. 11 …… X-ray tube, 12 …… X-ray detector 13 …… Goniometer, 14 …… Rotation mechanism 15 …… X-ray tube angle setting mechanism 16 …… Detector angle setting mechanism 18 …… Sample rotation mechanism, 19… …sample

Claims (1)

(57) [Claims] 1. An X-ray source that emits X-rays that irradiates a sample, a collimator that determines the traveling direction of the X-ray flux emitted from the X-ray source, and an X-ray flux that is emitted from the collimator at a predetermined angle. A goniometer having an X-ray detector for detecting diffracted X-rays incident on the surface of the sample, and the sample is mounted so that the central axis is common to the goniometer,
A sample stage having a sample rotating mechanism that rotates the mounted sample by a predetermined angle, and an X-ray that determines the traveling direction of the X-ray flux by rotating the X-ray source and the collimator around the center of the X-ray source by a predetermined angle. A source rotation mechanism, a detector rotation mechanism that rotates the X-ray detector at a predetermined angle around the center of the detection surface of the X-ray detector, and a predetermined angle around the center of the goniometer. A crystal orientation determining apparatus, comprising: a rotating mechanism that rotates at least one of a detector and rotating the X-ray source, the X-ray detector, and the sample independently.