JP3245235B2 - Crystal orientation discrimination method for single crystal ingot - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the crystal orientation of a cylindrical single crystal ingot by X-ray diffraction.

[0002]

2. Description of the Related Art An Si single crystal ingot for manufacturing a Si wafer is manufactured to have a predetermined crystal orientation. For example, with respect to the axial direction of the ingot, the crystal orientation [1]
10]. Here, the crystal orientation [110]
Is the direction of the normal to the lattice plane (110). Further, an orientation flat surface (hereinafter, abbreviated as an orientation flat surface) is formed in the Si single crystal ingot, and a normal line of the orientation flat surface matches a specific crystal orientation.

[0003] The ingot processed in this way is inspected by X-ray diffraction measurement to determine how much the orientation flat surface and the outer peripheral surface deviate from a predetermined crystal orientation. This inspection method will be described with reference to FIG. The following describes how to measure the angle δ1 between the normal direction 20 of the orientation flat surface 16 and a specific crystal orientation (for example, the crystal orientation [110]). In a plane perpendicular to the orientation flat surface 16, X-rays 22 are irradiated onto the orientation flat surface 16 at an incident angle θ1, and the diffracted X-rays are measured by an X-ray detector at an angle θ1 from the orientation flat surface. However, actually, the orientation flat 16 is placed on the reference surface, and the same measurement is often performed on the outer peripheral surface opposite to the orientation flat 16. The angle θ1 is set to the diffraction angle of the (110) plane of Si. The relative position between the X-ray source and the X-ray detector is fixed, and the angular position of the diffraction peak is searched for while rotating the entire X-ray optical system around the rotation axis 21 to find the above-mentioned deviation angle δ1. Can be found.

In order to inspect the angle δ2 between the central axis 24 of the outer peripheral surface 18 and a specific crystal orientation (for example, a crystal orientation [111]), X in a plane perpendicular to the end face 13 is determined. A line 26 is irradiated on the end face 13 at an incident angle θ2, and the diffracted X-ray is measured by an X-ray detector at the angle θ2. The angle θ2 is set to the diffraction angle of the (111) plane of Si. Then, the relative position between the X-ray source and the X-ray detector is fixed and the angular position of the diffraction peak is searched for while rotating the entire X-ray optical system around the rotation axis 25, thereby obtaining the above-mentioned deviation angle δ2. Can be found. Actually, the lattice plane (1
11) is not necessarily inclined in the direction including the X-ray optical system, so that the ingot is further rotated around the central axis 24 by, for example, 90 degrees, and the shift angle δ2 is measured in the same manner. The true deviation angle δ2 and the inclination direction are obtained from the plurality of measurement results.

By the way, Si belongs to the cubic system. In the cubic system, (101) and (011) planes are equivalent to the lattice plane (110) in X-ray diffraction. Let these equivalent lattice planes be represented by {110}. The plane spacings of these equivalent lattice planes are all the same and diffract at the same diffraction angle. Therefore, it is not possible to distinguish these equivalent lattice planes only by specifying the diffraction angle. In a simple cubic system, these equivalent lattice planes are completely equivalent, and there is no point in distinguishing them. However, since Si has a diamond structure, the equivalent lattice planes described above are not completely equivalent, and it is significant to distinguish between them. That is, when considered as a simple cubic crystal, six equivalent {110} planes can be distinguished into two types of three lattice planes. These will be referred to as (110) A (110) B. In an actual Si ingot, for example, when the normal direction of the orientation flat surface coincides with the {110} surface, (11
Since 0) A or (110) B is specified, it is necessary to distinguish these two types of lattice planes when forming the orientation flat surface.

Conventionally, in order to discriminate between the above (110) A and (110) B, these are discriminated by using an optical image method, and thereafter, the (110) plane of the (110) plane is used by using X-ray diffraction. Accurate azimuth measurement was performed.

[0007]

If the direction is determined by using the optical image method and then the direction is measured by using the X-ray diffraction, it takes a long time and the apparatus of the optical image method and the X-ray diffraction are required. The disadvantage is that both devices have to be prepared.

An object of the present invention is to provide a method for determining the crystal orientation of a single crystal ingot, which can determine the lattice plane using X-ray diffraction.

[0009]

SUMMARY OF THE INVENTION The first invention is a crystal orientation determination method for determining the crystal orientation of the cylindrical single crystal ingot by X-ray diffraction, in the single crystal ingot
In a plane perpendicular to the central axis, the distance from the first crystal lattice plane
X-ray source and first X-ray detector for detecting diffracted X-rays
And arranging, with respect to a plane perpendicular to the central axis
Diffraction from the second crystal lattice plane in the inclined plane
X-ray source and second X-ray detector so as to detect X-rays
And arranging, on the outer peripheral surface of the single crystal ingot
It said single crystal ingot is irradiated with X-rays from the X-ray source
By rotating about said central axis, and at the same time obtain a <br/> first diffraction pattern from the first crystal lattice plane in the first X-ray detector quiescent said stationary Obtaining a second diffraction pattern from the second crystal lattice plane with a second X-ray detector, and comparing a peak position of the first diffraction pattern with a peak position of the second diffraction pattern. Determining the crystal orientation of the single crystal ingot.

[0010] Delete

The second invention is characterized in that, in the first invention, the crystal structure of the single crystal ingot is a diamond structure.

[0012]

The first X-ray detector measures the diffracted X-rays from the lattice plane for which the lattice plane is to be determined. On the obtained first diffraction pattern, diffraction peaks appear in a six-fold or four-fold symmetry. These diffraction peaks are equivalent on the first diffraction pattern and cannot be distinguished on this pattern. The second X-ray detector measures diffracted X-rays from a lattice plane outside the lattice plane discrimination target. Comparing the obtained peak position on the second diffraction pattern with the above-mentioned peak position on the first diffraction pattern, the equivalent peaks on the first diffraction pattern are Two or more types can be determined in relation to the peak position.

[0013]

FIG. 1 is a schematic perspective view of an apparatus used in the crystal orientation measuring method of the present invention. This crystal orientation measuring device is a device for determining the crystal orientation of a Si ingot, and includes two X-ray detectors 40 and 44. First
The X-ray detector 40 and the X-ray source 38 are disposed on a plane perpendicular to the z1 axis which is the center axis of the ingot 28 (ie, an xy plane). Second X-ray detector 44 and X-ray source 3
8 is arranged in a plane inclined with respect to a plane perpendicular to the z1 axis. The X-rays from the X-ray source 38 are diffracted on the outer peripheral surface of the ingot 28 and the first X-ray detector 40 or the second X-ray
The light is detected by the line detector 44. Although not shown, in the crystal orientation measuring apparatus, the ingot 28 can be supported by the sample holder and the ingot 28 can be rotated by the sample rotating mechanism. The control of the rotation angle of the ingot 28 is performed based on a pulse signal of a pulse encoder in contact with the outer periphery of the ingot 28.

Next, a description will be given of a direction discriminating method for processing the orientation flat surface of a Si ingot using this apparatus.
The Si ingot used is a <111> pull-up ingot. Also, the normal direction of the orientation flat surface to be processed is
<110>. Therefore, the orientation flat surface is set to be parallel to the lattice plane {110}. However, $ 11
0 ° is equal to 2 of (110) A and (110) B as described above.
There are types, and the present apparatus can distinguish these two types. (110) belonging to the A, the lattice plane (1 01),
(01 1 ), (1 10 ), and belonging to (110) B are the lattice planes ( 1 10), (10 1 ), and (0 11 1). In addition, usually, when the Miller index representing the lattice plane is negative, a line is drawn over the number, but in the specification of the patent application, it is not possible to draw a line over the number. Let's draw a line below the numbers to represent negative numbers.

When the xyz coordinate axis is set as shown in FIG. 1, the direction of the incident X-ray is on the xy plane and is θ from the y axis.
_The direction is rotated by ₍₂₂₀₎ . Angle θ ₍₂₂₀₎ is ｛11
The Bragg angle corresponding to the diffraction plane {220} plane parallel to the 0 ° plane (about 23.65 in the case of using CuKα X-rays)
Degree). The first X-ray detector 40 is installed at a position where diffraction X-rays from the {110} plane can be detected, that is, at an angular position of 2θ ₍₂₂₀₎ with respect to the incident X-rays. Also, the second X
The line detector 44 is installed at a position where diffraction X-rays from the {311} plane can be detected. Since the {311} plane is not a plane parallel to the z-axis, diffracted X-rays from the {311} plane are reflected above the xy plane.

After arranging the X-ray detectors 40 and 44 as described above, the ingot 28 is rotated once around the z1 axis while irradiating the outer peripheral surface of the ingot 28 with two X-rays. The diffraction patterns are measured by the detectors 40 and 44.
FIG. 2 is a stereo projection of this Si ingot.
As is apparent from this figure, during one rotation of the ingot 28, the first X-ray detector 40 corresponding to the {110} plane has a six-fold symmetric diffraction peak, which corresponds to the {311} plane. A three-fold symmetric diffraction peak appears on the second X-ray detector 44.

FIG. 3A shows a diffraction pattern measured by the first X-ray detector 40, and FIG. 3B shows a diffraction pattern measured by the second X-ray detector 44. The horizontal axis is the rotation angle of the ingot 28. During one rotation of the ingot 28, (A) shows six diffraction peaks corresponding to the {110} plane, and (B) shows three diffraction peaks corresponding to the {311} plane. Here, with reference to the position of the diffraction peak appearing in (b), how much the diffraction peak appearing in (a) is shifted is examined. Then, a peak (shown as A) shifted from the peak of (b) by +25.1 degrees and a peak (shown as B) shifted by -34.9 degrees from the peak of (b) It can be seen that it can be classified into two types. The former belongs to (110) A and the latter belongs to (110) B. Also, as another determination method,
In (a), two types can be discriminated based on whether or not the peak (b) exists between two adjacent peaks. That is, when the peak of (b) exists between two adjacent peaks of (a), the peak of (a) preceding the peak of (b) belongs to (110) B,
The peak of (a) after the peak of (b) is (1)
10) It belongs to A.

As described above, (110) A and (11)
0) Since B can be determined, the ingot 28 can be rotated in a desired direction depending on which surface the orientation flat surface is formed. Further, subsequently, using the first X-ray detector 40, (110) A or (110) A
The azimuth of B can be measured accurately, and thereby the rotation angle of the ingot 28 can be finely adjusted. Thereafter, processing for forming the orientation flat surface is performed.

Next, a description will be given of a method of determining a bearing when a <511> pull-up ingot is used as the Si ingot. In this case, there are only two {110} planes parallel to the axis of the ingot: (0 1 1) and (01 1 ). Since the orientation flat surface is processed so as to be parallel to any one of the surfaces, it is sufficient that the difference between the two can be determined. The stereo projection in this case is as shown in FIG. (0 1 1) and (0
To determine 1 1 ), (02) parallel to the (011) plane
2) Use reflection from the surface. Therefore, the second X-ray detector 44 is positioned above the xy plane (022).
It is arranged at a position where X-ray diffraction from the surface can be detected. The position of the first X-ray detector 40 is the same as in the case of the <111> lifting ingot.

FIG. 5A shows a diffraction pattern measured by the first X-ray detector 40 for the <511> pulled ingot, and FIG. 5B shows a diffraction pattern measured by the second X-ray detector 44. It is a pattern. During one revolution of ingot 28,
(B) the two diffraction peaks (01 1) and (0 1 1) appears, appear (b) in one of the diffraction peak (022). Here, with reference to the position of the diffraction peak appearing in (b), how much the diffraction peak appearing in (a) is shifted is examined. Then, there is a peak shifted by +91.0 degrees from the peak of (b) and a peak shifted by -89.0 degrees from the peak of (b). The former is (0 1 1) and the latter is (01 1 ). As another discrimination method, (b) between two adjacent peaks appearing in (a).
The two types can also be determined based on whether or not the peak exists. That is, when the peak of (b) exists between two adjacent peaks of (a), the peak of (a) preceding the peak of (b) is (01 1 ),
The peak of (a) after the peak of (b) is (0)
11 ).

Although the method of determining the orientation of a Si ingot has been described above, the method of the present invention can be applied to other single crystal ingots (eg, Ge) having a diamond structure similar to Si.

[0022]

According to the method for determining the crystal orientation of the present invention, diffraction X
Since the orientation can be determined using the line, the orientation of the ingot and the subsequent accurate orientation measurement can be continuously performed by one crystal orientation measuring device.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of an apparatus for performing the method of the present invention.

FIG. 2 is a stereo projection of a <111> pull-up ingot.

FIG. 3 is a graph showing a diffraction pattern of a <111> pull-up ingot.

FIG. 4 is a stereographic view of a <511> pull-up ingot.

FIG. 5 is a graph showing a diffraction pattern of a <511> pull-up ingot.

FIG. 6 is a perspective view for explaining the crystal orientation measurement of the ingot.

[Explanation of symbols]

 28 single crystal ingot 40 first X-ray detector 44 second X-ray detector

Claims (2)

(57) [Claims] In a crystal orientation discrimination method for discriminating the crystal orientation of a cylindrical single crystal ingot by X-ray diffraction, the crystal orientation is determined within a plane perpendicular to the central axis of the single crystal ingot.
To detect diffracted X-rays from the first crystal lattice plane.
Arranging an X-ray source and a first X-ray detector in a plane which is inclined with respect to a plane perpendicular to the central axis.
To detect diffracted X-rays from the second crystal lattice plane.
The X-ray source and the step of arranging the second X-ray detector, the single crystal ingot is irradiated with X-rays from the X-ray source on the outer peripheral surface of the single crystal ingot about the central axis by rotating <br/> rotation, at the same time obtaining a first diffraction pattern from the first crystal lattice plane in the first X-ray detector quiescent said second X-ray quiescent wherein the detector
Obtaining a second diffraction pattern from a second crystal lattice plane; and comparing the peak position of the first diffraction pattern with the peak position of the second diffraction pattern to determine the crystal orientation of the single crystal ingot. Determining a crystal orientation of a single crystal ingot. 2. The crystal structure of the single crystal ingot has a die structure.
2. The method according to claim 1, wherein the crystal orientation is a diamond structure .