JPH11190705A - Method for measuring crystal orientation of single crystal silicon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for measuring a crystal orientation for accurately specifying the orientation as compared with a prior art irrespective of presence or absence of a mirror surface. SOLUTION: A single crystal ingot is rotated at 360 deg.C. Four peal values X1 to X4 in a plane (220) are existed at each about 90 deg. of an X-ray diffracted light intensity are confirmed with low threshold values, and an axis in plane (100) is collated. Further, the ingot is rotated at 60 deg.. It is confirmed that only the peak values X1 , X2 in the plane (220) of the four peak values X1 to X4 in plane arrive at high threshold values, and a 4 deg. offset is collated. Further, the ingot is rotated. Again, the latter obtained peak value X2 in the plane (220) of the value X1 , X2 arriving at the high threshold values is selected. A center of a rotating angle of the value X2 in plane of the high threshold value is specified as a notch forming position N.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for cutting a notch or an orientation flat surface by determining a cut surface when cutting this crystal at a certain angle with respect to a reference axis of a crystal orientation of single crystal silicon. And a method for measuring the crystal orientation of the single crystal silicon.

[0002]

2. Description of the Related Art In manufacturing semiconductor wafers,
It is obtained by cutting a single crystal ingot pulled up by a CZ method or the like and subjecting it to processing such as chamfering and polishing. In the cutting of the ingot, it may be required to cut at a certain angle with respect to the reference axis of the crystal orientation in accordance with a request from a device process. For example,
The axis exactly in the 100 (one zero zero) direction (hereinafter,
This is referred to as “<100> axis”. In some cases, the silicon ingot pulled up in step (1) is cut at a plane perpendicular to an angle of 4 degrees with respect to the <100> axis. In this case, if the silicon ingot is simply cut at the angle of 4 degrees, the following problem occurs. (1) Since the cross-sectional shape is elliptical, more parts are discarded during processing into a perfect circular semiconductor wafer, and more waste is caused in the processing step. (2) When the ingot is cut, both end faces become wedge-shaped, and when the diameter becomes large, the amount cannot be ignored.

[0003] Therefore, the center axis of the shape is already 4
If the crystal inclined at an angle is cut at a right angle to the central axis of the shape, the above-mentioned problems (1) and (2) can be solved.

However, in performing such a cutting, unless a crystal orientation is accurately specified and this inclined surface is cut accurately according to the crystal orientation, a required cut surface cannot be obtained. Is clear. Therefore, as a conventional method of specifying this crystal orientation, a specific shape called a mirror surface formed on the upper part of the ingot after pulling up the ingot, visually mark the approximate position, after processing the outer peripheral surface , (22
In addition to measuring the X-ray diffraction light intensity of the 0) plane, the crystal orientation and the (110) plane were specified with reference to the marking, and the orientation flat or notch was formed according to this direction. That is, the wafer is cut on the basis of the orientation flat or the notch, and when the processed semiconductor wafer is subjected to device processing, the orientation flat or the notch is used as a reference for determining the direction.

[0005] The reason why the above marking is required is as follows.
In order to specify the (110) plane having a specific positional relationship with respect to the center axis of the shape, simply measuring the X-ray diffraction light intensity of the (220) plane indicates that the crystal axis is inclined with respect to the center axis of the shape. Since the mirror plane position cannot be specified, the (110) plane can be specified by using the mirror surface position as another judgment material.

[0006]

However, the marking by the mirror surface largely depends on the determination of the shape of the mirror surface, and has to be visually determined, which is difficult to automate. Further, this conventional method is based on the premise that there is a mirror surface, and it is impossible to specify the crystal orientation again in a state where the mirror surface has disappeared by cutting off the upper part of the ingot. Furthermore, when the above-mentioned marking is not accurate or the judgment is wrong, there is a problem that it is difficult to accurately measure the crystal orientation. The present invention
The present invention has been made in view of the above problems, and has as its object to provide a method of measuring a crystal orientation that can specify a crystal orientation more accurately than in the related art regardless of the presence or absence of a mirror surface.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a method for obtaining a predetermined cut surface in consideration of a tilt angle from single crystal silicon pulled at a certain tilt angle with respect to a reference axis of a crystal orientation. In the method for measuring the crystal orientation, after forming the outer peripheral surface of the single crystal silicon, at least 360 ° around the central axis of the single crystal silicon in a radial direction about the central axis on the shape of the single crystal silicon. By measuring the X-ray diffraction light intensity of
The crystal orientation is identified by determining the intensity of the peak value of the line diffraction light intensity.

Further, regarding single-crystal silicon formed at an inclination angle of 4 degrees with respect to the (100) plane reference axis,
X-ray diffraction light intensity in a radial direction about the shape center axis is measured at least 360 ° around the shape center axis,
The position of the (110) plane is specified based on the measured values, and the position of the arbitrary (110) plane is selected by comparing the diffraction intensity difference between the respective (220) planes.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In order to accurately cut a single crystal ingot that has been pulled up with its crystal center axis inclined beforehand so as to have a cut surface required in a device process, the crystal orientation of the ingot before cutting is determined. Is a method of measuring the crystal orientation that accurately specifies the crystal orientation, even if it is surface-processed and cut into blocks, without relying on the shape specific to a pulled single crystal such as a mirror surface, and accurately specifying the crystal orientation Is what you can do.

As a specific method, the intensity of the X-ray diffraction light in each circumferential direction around the center of the shape of the ingot is continuously measured at least 360 °, and the peak value obtained by the measurement is approximately 90 °. In addition, by taking advantage of the fact that these peak values rise and fall regularly as a characteristic of this ingot, two thresholds are set, and two of the peak value positions that reach the higher threshold are obtained. By selecting any one of them, it is possible to always specify the crystal orientation under the same conditions and accurately form a notch or orientation flat which is a reference for a required cut surface.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a crystal orientation of a single crystal ingot, and FIG. 2 is a graph showing a method of specifying a notch formation position by comparing X-ray diffraction intensities. The single crystal ingot of this embodiment is a crystal pulled up by offset by 4 ° with respect to the <100> axis direction. As shown in FIG. 1, the single crystal ingot is rotated around a center axis C,
By measuring the X-ray diffraction intensity, (220) plane peak X ₁ to X ₄ are obtained approximately every 90 °.

When measuring the intensity of the X-ray diffraction light, the single crystal ingot is chucked at the center axis C of the shape, and an X-ray diffractometer (shown in FIG. And the single crystal ingot is rotated on a rotation axis (shape central axis C) controlled by a numerical controller with an accuracy of 1 ° / 1,000 to measure the X-ray diffraction light intensity.

In this measurement, four (110) plane peak values X _{1 to} X ₄ are obtained at intervals of about 90 ° as shown in FIG. In analyzing the measured values, a high threshold of 70% diffraction intensity and a diffraction intensity of 3%
Set a low threshold of 0%.

Therefore, in order to actually specify the notch formation position, the following procedure is performed. (1) The single crystal ingot is rotated 360 °, and the obtained X-ray diffraction light intensity shows four (220) plane peak values X _{1 to} X ₄
Is checked at a low threshold value at about every 90 °, and the <100> axis is collated. (2) Following this, a single crystal ingot is further added to 360.
And rotate it to confirm that only the (220) plane peak values X ₁ and X _{2 of} the four (220) plane peak values X _{1 to} X ₄ obtained in the same manner have reached the high threshold. Thus, it is verified that the offset is 4 °. (3) Further, continuously rotate the single crystal ingot,
(220) plane peak value X ₁ reaching the high threshold again obtained,
Among X _2, selects the latter (220) plane peak X _2, identifies the center of the rotation angle of the high threshold (220) plane peak value X ₂ as a notch forming position N.

In the above embodiment, a high threshold value of 70% for the diffraction intensity and a low threshold value of 30% for the diffraction intensity are set, but discrimination is possible if the difference between the diffraction intensities is 10% or more.

[0016]

According to the present invention, the configuration is as described above.
The crystal orientation of the single crystal ingot pulled up by the offset can be measured even if it has no shape characteristic such as a mirror surface. In addition, the crystal orientation can be made accurate, and particularly, 4 °
About the offset pulled single crystal ingot,
There is an excellent effect that the (110) plane can be reliably differentiated, so that the (110) plane under the same conditions can be selected.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a crystal orientation of a single crystal ingot.

FIG. 2 is a graph showing a method of specifying a notch formation position by comparing X-ray diffraction intensities.

[Explanation of symbols]

C ‥‥‥ shape the central axis X ₁ ~X ₄ ‥‥‥ (220) plane peak value N ‥‥‥ notching position

Claims (5)

[Claims] 1. A method for measuring a crystal orientation in order to obtain a predetermined cut surface in consideration of the inclination angle from single crystal silicon pulled up at a certain inclination angle with respect to a reference axis of the crystal orientation, After forming the outer peripheral surface of the single crystal silicon, measuring an X-ray diffraction light intensity of at least 360 ° around the central axis of the single crystal silicon in a radiation direction centered on the central axis of the single crystal silicon. And determining the crystal orientation by determining the intensity of the peak value of the X-ray diffraction light intensity. 2. A high threshold and a low threshold are set, and an X-ray diffraction light intensity position at which the high threshold is reached and an X-ray diffraction light position at which the low threshold is reached
2. The method for measuring a crystal orientation according to claim 1, wherein the crystal orientation is specified by comparing with a line diffraction light intensity position. 3. An X-ray diffraction light intensity of a single crystal silicon formed at an inclination angle of 4 degrees with respect to a (100) plane reference axis in a radial direction about a center axis of the shape.
By measuring at least 360 ° around the central axis of the shape, the position of the (110) plane is specified by the measured values, and the difference in diffraction intensity between the respective (220) planes is compared to determine the position of the arbitrary (110) plane. A method for measuring a crystal orientation, characterized by selecting. 4. A high threshold value and a low threshold value having a level difference of 10% or more for determining the X-ray diffraction intensity are set, and the X-ray diffraction light intensity position reaching the high threshold value and the low threshold value are determined. 4. The method of measuring a crystal orientation according to claim 3, wherein the position of the arbitrary (110) plane is selected by comparing the position of the X-ray diffraction light intensity that has reached the maximum value. 5. A high threshold value and a low threshold value having a level difference of 10% or more for determining the X-ray diffraction intensity are set, and the first and second diffraction light intensity measurements at 360 ° around the central axis of the shape are performed. 1
10) After confirming the position of the plane, the second diffraction light intensity measurement at 360 ° around the central axis of the shape confirms a tilt angle of 4 ° with respect to the (100) plane reference axis, followed by 180 ° around the central axis of the shape. 4. The method for measuring a crystal orientation according to claim 3, wherein an arbitrary position of the (110) plane is selected based on a measured value obtained by the diffraction light intensity measurement at 360 °.