JP2691663B2 - Measuring method of interstitial oxygen concentration distribution of silicon wafer - 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 measuring an interstitial oxygen concentration distribution of a silicon wafer, and more particularly to a red color obtained by combining a pulling silicon wafer to be measured and a reference floating zone silicon wafer (containing no oxygen). The present invention relates to a method for measuring the interstitial oxygen concentration distribution of a silicon wafer by external absorption spectroscopy.

[0002]

2. Description of the Related Art The present inventor has, as a method of measuring the interstitial oxygen concentration of a silicon wafer of this type, measures the infrared light transmission characteristics of a measurement wafer and the infrared light transmission characteristic of a reference wafer to measure We proposed to obtain the oxygen concentration (Japanese Patent Application No. 2-204316, etc.). Further, the present inventor has further proposed that when the measurement wafer and the reference wafer have different thicknesses, the thickness correction is performed in calculating the interstitial oxygen concentration of the measurement wafer (Japanese Patent Application No. 4-
No. 75561). That is, the present inventor has the first step of measuring the incident parallel polarized light intensity, the second step of measuring the light transmission characteristics of the reference wafer by making parallel polarized light incident on the reference wafer at Brewster's angle, and the measurement wafer. The third step of measuring the light transmission characteristics of the measurement wafer by injecting parallel polarized light at a Brewster's angle with respect to
The interstitial oxygen concentration of the measurement wafer is calculated from the incident parallel polarization intensity measured in the step, the light transmission characteristic of the reference wafer measured in the second step, and the light transmission characteristic of the measurement wafer measured in the third step. A silicon wafer interstitial oxygen concentration measurement method including a fourth step was proposed.

The silicon wafer referred to in this specification is 1
Not only those having a thickness of 1 mm or less but also those having a thickness of 1 mm or more are included.

[0004]

In measuring the interstitial oxygen concentration distribution of a silicon wafer, incident light is measured when the light transmission characteristic of the silicon wafer is measured by making parallel polarized light incident on the silicon wafer at Brewster's angle. When the movement of the incident spot on the surface of the silicon wafer formed by the beam was changed in various directions, it was found that the spatial resolution in measuring the interstitial oxygen concentration distribution of the silicon wafer was significantly different.

It has also been discovered that the shape of the incident spot formed on the surface of the silicon wafer by the incident light beam causes a significant difference in the spatial resolution in measuring the interstitial oxygen concentration distribution of the silicon wafer.

Therefore, an object of the present invention is to improve the moving direction and shape of the incident spot on the surface of the silicon wafer formed by the incident light beam, and to improve the spatial resolution in measurement. An object of the present invention is to provide a method for measuring an oxygen concentration distribution.

[0007]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a method for measuring the oxygen concentration distribution between silicon wafer lattices, which measures the light transmission characteristics of a silicon wafer by making parallel polarized light incident on the silicon wafer at Brewster's angle. , The incident spot on the surface of the silicon wafer is made thin so that the ratio of the long axis to the short axis is 3 to 4, and the short axis of the incident spot is arranged in the radial direction of the silicon wafer to make the incident spot. It is a method for measuring the interstitial oxygen concentration distribution of a silicon wafer, which is characterized by moving in the short axis direction.

[0008]

The interstitial oxygen concentration distribution of a silicon wafer tends to be point-symmetrical with respect to the center of the silicon wafer due to the manufacturing process of the silicon wafer. When the ratio of the minor axis to the minor axis is 3 to 4, and the minor axis of the incident spot is arranged in the radial direction of the silicon wafer and the incident spot is moved in the minor axis direction, The incident spots are arranged along the circumferential direction of the same density, and even if the measurement interval is made small, a large number of incident spots are arranged without overlapping each other, and the measurement resolution is improved.

According to the present invention, the distribution measurement of interstitial oxygen concentration of a silicon wafer can theoretically be performed with the highest spatial resolution.

[0010]

EXAMPLE In a preferred embodiment of the present invention, the incident parallel polarized light intensity is measured, and the light transmission characteristic of the reference wafer is measured by making parallel polarized light incident on the reference wafer at Brewster's angle. On the other hand, the light transmission characteristics of the measurement wafer are measured by making parallel polarized light incident at Brewster's angle, and from the measured incident parallel polarization intensity, the light transmission characteristics of the reference wafer, and the light transmission characteristics of the measurement wafer, the measurement wafer Calculate the interstitial oxygen concentration. At that time, the incident spot on the surface of the silicon wafer is made into a thin shape in which the ratio of the major axis and the minor axis is 3 to 4, and the minor axis of the incident spot is arranged in the radial direction of the silicon wafer to make incident light. Move the spot along its minor axis.

Assuming that the incident spots have the same area, it is effective in terms of resolution that the incident spot has a thin shape having a major axis and a minor axis.

A preferable example of the thin shape is an ellipse or a rectangle. For example, when the cross section of the incident light beam is a perfect circle, the Brewster angle of the silicon wafer is set to 73.7 degrees, so that the incident spot formed on the surface of the silicon wafer by the incident light beam is long. It becomes an ellipse with a ratio of the axis to the minor axis of about 3.56. Further, when the cross section of the incident light beam is square, the Brewster angle of the silicon wafer is set to 73.7 degrees, so that the incident spot formed on the surface of the silicon wafer by the incident light beam has a long axis. And the minor axis ratio becomes a rectangle of about 3.56. It is preferable to set the ratio of the major axis to the minor axis of the incident spot on the wafer surface formed by the incident light beam to about 3 to 4, not to mention ellipses and rectangles as well as any other thin shapes. .

It is optimal to arrange the minor axis of the incident spot in the radial direction of the silicon wafer and move the incident spot in the minor axis direction.

Illustrative Example FIG. 1 conceptually shows a state in which the light transmission characteristics of the silicon wafer 1 are measured by making an incident light beam 2 of parallel polarization incident on the silicon wafer 1 at a Brewster's angle B.

In FIG. 1, the silicon wafer 1 is in the XY plane, and the center of the silicon wafer 1 is located at the origin O. The optical path L of the incident light beam 2 lies in the YZ plane.
In this illustrated example, the YZ plane is the incident surface of the incident light beam 2. The incident spot 3 on the surface of the silicon wafer 1 formed by the incident light beam 2 has the Brewster angle B of the silicon wafer 1 set to 73.7 degrees, so that the incident spot 3 has the major axis and the minor axis. Ratio is about 3.56
Becomes an ellipse. The major axis of the elliptical incident spot 3 is on the Y axis and its minor axis is on the X axis. The incident spot 3 is moved in the short axis direction, that is, the X axis direction, and the oxygen concentration distribution between the silicon wafer lattices is measured. For example, when the diameter of the incident light beam 2 is 4 mm, the major axis length of the incident spot 3 is about 7 mm and the minor axis length is 2 mm. Incident spot 3
Is moved in the short axis direction, that is, the X axis direction at intervals of 5 mm to measure the oxygen concentration distribution between silicon wafer lattices.

FIG. 2 schematically shows a procedure for measuring such an oxygen concentration distribution between silicon wafer lattices. The incident spot 3 is moved in the short axis direction, that is, the X axis direction at intervals of 5 mm, and the oxygen concentration distribution between the silicon wafer lattices is measured. In addition to the incident spot 3 at the center position, FIG. 2 shows two incident spots 3 as a representative in the minor axis direction of the incident spot 3, that is, in the X-axis direction.

Although two incident spots 3 are also shown in FIG. 2 in the major axis direction of the incident spot 3, that is, in the Y-axis direction,
Such movement of the incident spot 3 in the Y-axis direction is outside the scope of the present invention.

Due to the manufacturing process of the silicon wafer 1, the interstitial oxygen concentration distribution of the silicon wafer 1 tends to be point-symmetrical. In other words, the interstitial oxygen concentration distribution of the silicon wafer 1 is substantially the same on the circumference 4 having the same radius when viewed from the center (the origin O). Therefore, when the incident spot 3 is moved in the short axis direction (X axis direction) and the interstitial oxygen concentration distribution of the silicon wafer 1 is measured, the incident spot 3 is moved in the long axis direction (Y axis direction). The spatial resolution is far superior to that of measuring the interstitial oxygen concentration distribution of the wafer 1. The highest resolution is
This is when the major axis of the elliptical incident spot 3 is accurately located in the tangential direction of the circle 4 centered on the origin O.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining the relationship between a measurement wafer, an incident light beam, and an incident spot in the method of the present invention.

FIG. 2 is a schematic diagram for explaining a moving direction of an incident spot with respect to a measurement wafer.

[Explanation of symbols]

 1 Silicon wafer 2 Incident light beam 3 Incident spot O Origin B Brewster angle L Optical path

Claims (1)

(57) [Claims] 1. A method for measuring a distribution of oxygen concentration between lattices of a silicon wafer, comprising measuring incident light spots on a surface of a silicon wafer by measuring parallel light incident on the silicon wafer at Brewster's angle to measure light transmission characteristics of the silicon wafer. Characterized by making a thin shape in which the ratio of the major axis to the minor axis is 3 to 4, and arranging the minor axis of the incident spot in the radial direction of the silicon wafer and moving the incident spot in the minor axis direction. Measuring method of interstitial oxygen concentration distribution of silicon wafer.