JP-7856034-B2 - Method for determining defective areas

JP7856034B2JP 7856034 B2JP7856034 B2JP 7856034B2JP-7856034-B2

Inventors

米谷史音

Assignees

信越半導体株式会社

Dates

Publication Date: 20260511
Application Date: 20230328

Claims (12)

The process includes: an image acquisition step in which a surface inspection device having a high-angle mode and a low-angle mode irradiates the surface of a silicon single crystal substrate having at least one mirror-polished (100) surface with laser light in the low-angle mode, and a two-dimensional detector detects scattered light and photoluminescence from defects on the surface of the silicon single crystal substrate to acquire an image of the defects; an image determination step in which it is determined whether the acquired image has features that are seen in the I-rich region; and a defect region determination step in which, if it is determined in the image determination step that the image has features that are seen in the I-rich region, a defect index is calculated from the image, and the region in which the defect index exceeds a predetermined threshold is determined to be the I-rich region . The first method for determining whether the defect has features observed in the I-rich region in the image determination step is to determine that the defect has features observed in the I-rich region if the image of the defect obtained in the image acquisition step is a bright line along the <011> direction. A method for determining the I-rich region of a silicon single crystal substrate, characterized in that, when the determination is made by the first method, the indicator of defects is at least one of the number of defects determined to have characteristics observed in the I-rich region by the first method, the density of defects determined to have characteristics observed in the I-rich region by the first method, and the ratio of the number of defects determined to have characteristics observed in the I-rich region by the first method to the total number of defects detected by the surface inspection device.
The method for determining an I-rich region of a silicon single crystal substrate according to claim 1 , characterized in that the image of the defect is rotated to align with the crystal orientation of the silicon single crystal substrate before determination is performed.
The process includes: an image acquisition step in which a surface inspection device having a high-angle mode and a low-angle mode irradiates the surface of a silicon single crystal substrate having at least one mirror-polished (100) surface with laser light in the low-angle mode, and a two-dimensional detector detects scattered light and photoluminescence from defects on the surface of the silicon single crystal substrate to acquire an image of the defects; an image determination step in which it is determined whether the acquired image has features that are seen in the I-rich region; and a defect region determination step in which, if it is determined in the image determination step that the image has features that are seen in the I-rich region, a defect index is calculated from the image, and the region in which the defect index exceeds a predetermined threshold is determined to be the I-rich region. A second method for determining whether the image has features observed in the I-rich region in the image determination step involves detecting scattered light and photoluminescence at a first angle (low angle) and a second angle (high angle) in the image acquisition step, and determining that the image has features observed in the I-rich region if an image with defects is obtained only in the scattered light and photoluminescence at the first angle. A method for determining the I-rich region of a silicon single crystal substrate, characterized in that, when the determination is made by the second method described above, the defect index is the ratio of the number of defects determined to have characteristics observed in the I-rich region by the second method to the total number of defects detected by the surface inspection device.
The method for determining the I-rich region of a silicon single crystal substrate according to claim 1, characterized in that, in the image determination step, at least one image processing, such as cropping, pseudo-colorization, or binarization, is performed on the image before determination.
The method for determining the I-rich region of a silicon single crystal substrate according to claim 3, characterized in that, in the image determination step, at least one image processing, such as cropping, pseudo-colorization, or binarization, is performed on the image before determination.
The method for determining the I-rich region of a silicon single-crystal substrate according to claim 1, characterized in that the threshold used for determining the I-rich region is predetermined from the defect index of the image determined to have the characteristics observed in the I-rich region, obtained by acquiring an image of a silicon single-crystal substrate having a mirror-polished (100) surface with known defect regions under the same conditions as the image acquisition step, and determining the image in the same manner as the image determination step.
The method for determining an I-rich region of a silicon single crystal substrate according to claim 3, characterized in that the threshold used for determining the I-rich region is predetermined from the defect index of the image determined to have the characteristics observed in the I-rich region, obtained by acquiring an image of a silicon single crystal substrate having a mirror-polished (100) surface with known defect regions under the same conditions as the image acquisition step, determining the image in the same manner as the image determination step.
The method for determining the I-rich region of a silicon single crystal substrate according to claim 1, characterized in that the silicon single crystal substrate is cleaned after mirror polishing.
The method for determining the I-rich region of a silicon single crystal substrate according to claim 3, characterized in that the silicon single crystal substrate is cleaned after mirror polishing.
The method for determining the I-rich region of a silicon single crystal substrate according to claim 1, characterized in that the image acquired in the image acquisition step is an image of multiple defects randomly selected from the detected defects.
The method for determining the I-rich region of a silicon single crystal substrate according to claim 3, characterized in that the image to be acquired in the image acquisition step is an image of a plurality of defects randomly selected from the detected defects.
The method for determining an I-rich region of a silicon single crystal substrate according to any one of claims 1 to 11 , wherein the defect region determination step determines a defect region in a predetermined range of the silicon single crystal substrate, and the predetermined range is an arbitrary region containing the number of defects necessary for determining the defect region.

Description

This invention relates to a method for determining defect regions in a silicon single-crystal substrate. In recent years, with the advancement of devices, high-precision control and evaluation of defect regions in semiconductor substrates (hereinafter sometimes simply referred to as "substrates") have become increasingly important. If the defect regions of the substrate differ from the desired defect regions, it can cause device failure. Such defect regions include, for example, regions with excess interstitial silicon (hereinafter referred to as I-rich regions), void generation regions (hereinafter referred to as V-rich regions), regions where oxygen precipitates are easily formed (hereinafter referred to as OSF regions), and regions with few defects (hereinafter referred to as N regions). The type of defects present varies depending on the defect region. It is known that the presence of different defect regions changes depending on the single crystal manufacturing conditions. Therefore, it is necessary to determine the defect regions of the substrate during the substrate manufacturing stage and, if undesirable crystal defects are present, to quickly provide feedback to the single crystal manufacturing process to prevent the occurrence of such defect regions. As a technique for determining defect regions, for example, Patent Document 1 discloses a technique for revealing B-band regions and dislocation cluster regions in a silicon single-crystal substrate through metal contamination and heat treatment. Furthermore, Patent Document 2 discloses a technique for measuring the number and/or defect density of defects on the surface of a silicon single-crystal substrate using a surface inspection device, and for determining the defect region of the substrate from the number and/or defect density. Furthermore, as a method for evaluating defects, for example, Patent Document 3 discloses a technique in which multiple photodetectors installed at different angles detect the intensity of scattered light due to a defect at each detector, and then evaluate whether the defect is located on the surface or inside the material based on the ratio of these scattering intensities. Furthermore, Patent Document 4 discloses a technique for separating and detecting attached particles and concave defects using a surface inspection device having two incident and two receiving systems. Furthermore, Patent Document 5 discloses a surface inspection device having multiple light-receiving systems with different light-receiving angles, which determines the type of defect based on the light-receiving intensity ratio in the multiple light-receiving systems. By applying this technique to a mirror-polished silicon single-crystal substrate, defects can be classified into three groups: scratches or blemishes or shallow pits, adhering particles or COP (Crystal Originated Particle), and internal defects near the surface. Furthermore, some of the latest surface inspection systems are equipped with two-dimensional detectors. These detectors capture scattered light and photoluminescence from defects as images, making it possible to identify scratches and stacking faults in epitaxial layers. Japanese Patent Publication No. 2021-075403Japanese Patent Publication No. 2017-092400Japanese Patent Publication No. 2015-070116Japanese Patent Publication No. 2001-153635WO01/027600 This is a flowchart showing an example of the first embodiment of the present invention.This is a flowchart showing an example of a second embodiment of the present invention.This is a schematic diagram showing an example of a surface inspection apparatus according to the first embodiment of the present invention.This is a schematic diagram showing an example of a surface inspection apparatus according to a second embodiment of the present invention.This figure shows an example of an image obtained by a two-dimensional detector of a surface inspection device, in which the defect image is a bright line along <011>.This figure shows an example of an image including a defect, acquired by a two-dimensional detector that detects scattered light and photoluminescence at a first angle, which is a low angle, of the surface inspection device.This figure shows an example of an image free of defects, acquired by a two-dimensional detector that detects scattered light and photoluminescence at a high angle (second angle) of the surface inspection device. The following describes embodiments of the present invention, but the present invention is not limited thereto. [First Embodiment] Figure 3 shows an example of a surface inspection apparatus for determining defective areas on a substrate according to the first embodiment of the present invention. As shown in Figure 3, this surface inspection apparatus 11 includes a laser light irradiation means 2 that irradiates the surface of the substrate (silicon single crystal substrate) W to be evaluated with laser light of a wavelength of 266 nm in low-angle