Defect inspection apparatus and defect inspection method

Patent metadata

Field	Value
Publication number	US-12578281-B2
Application number	US-202418627697-A
Country	US
Kind code	B2
Filing date	Apr 5, 2024
Priority date	Apr 5, 2023
Publication date	Mar 17, 2026
Grant date	Mar 17, 2026

Abstract

A defect inspection apparatus according to the present embodiment includes: an irradiation optical system configured to irradiate a sample including a SiC substrate, a buffer layer formed on the SiC substrate, and a drift layer formed on the buffer layer with excitation light; a filter unit configured to control a wavelength band to transmit photoluminescence light generated from the sample; a detection optical system configured to detect the photoluminescence light transmitted through the filter unit; and an image processing unit configured to form an image from the detected photoluminescence light and to discriminate a defect captured in the formed image, and the image processing unit discriminates the defect based on whether a length of the defect is L 1 =(D 1 +D 2 )/tan θ or L 2 =D 2 /tan θ.

First claim

What is claimed is:

1 . A defect inspection apparatus comprising:
an irradiation optical system configured to irradiate a sample including a silicon carbide substrate, a buffer layer formed on the silicon carbide substrate, and a drift layer formed on the buffer layer with excitation light; a filter unit configured to control a wavelength band to transmit photoluminescence light generated from the sample; a detection optical system configured to detect the photoluminescence light transmitted through the filter unit; and an image processing unit configured to form an image from the detected photoluminescence light and to discriminate a defect captured in the formed image, wherein the filter unit transmits the wavelength band including 420 nm or longer and 430 nm or shorter in the photoluminescence light, and when a thickness of the drift layer is defined as D 1 , a thickness of the buffer layer is defined as D 2 , an offset angle is defined as θ, and a first length and a second length are defined as L 1 and L 2 indicated respectively as follows:

L
⁢
1

=

(

D
⁢
1

+

D
⁢
2

)

/
tan
⁢
θ

L
⁢
2

=

D
⁢
2
/
tan
⁢
θ

,

the image processing unit
discriminates the defect as the defect including a basal plane dislocation continuing from the buffer layer to the drift layer in a case where a length of the defect belongs to a predetermined first range including the first length, and
discriminates the defect as the defect including the basal plane dislocation in the buffer layer and an edge dislocation in the drift layer in the case where the length of the defect belongs to a predetermined second range including the second length, the second range being different from the first range.

2 . The defect inspection apparatus according to claim 1 , wherein
the filter unit changes the wavelength band to be transmitted from the wavelength band including 420 nm or longer and 430 nm or shorter to the wavelength band including near infrared light, the detection optical system detects the near infrared light transmitted through the changed filter unit, and the image processing unit, when forming a near infrared image from the detected near infrared light and discriminating the defect captured in the formed near infrared image, in the case where a third length is defined as L 3 indicated as follows:

L
⁢
3

=

D
⁢
1
/
tan
⁢
θ

,

discriminates the defect as the defect including the basal plane dislocation in the drift layer in the case where the length of the defect belongs to a predetermined third range including the third length, the third range being different from the first range and the second range.

3 . The defect inspection apparatus according to claim 2 , wherein the image processing unit calculates accuracy of the discriminated defect by comparing the number of the defects having the length belonging to the first range and the number of the defects having the length belonging to the third range.

4 . The defect inspection apparatus according to claim 1 , wherein the image processing unit discriminates the defect captured in the image by using an algorithm for which the plurality of defects belonging to the first range and the plurality of defects belonging to the second range are machine-learned beforehand as learning data.

5 . The defect inspection apparatus according to claim 1 , wherein
an impurity concentration of the drift layer is 1×10 15 cm −3 or higher and lower than 5×10 17 cm −3 , and the impurity concentration of the buffer layer is 5×10 17 cm −3 or higher and 1×10 19 cm −3 or lower.

6 . A defect inspection method comprising:
a step of irradiating a sample including a silicon carbide substrate, a buffer layer formed on the silicon carbide substrate, and a drift layer formed on the buffer layer with excitation light; a step of transmitting photoluminescence light generated from the sample through a filter unit that controls a wavelength band to be transmitted; a step of detecting the photoluminescence light transmitted through the filter unit; a step of forming an image from the detected photoluminescence light; and a step of discriminating a defect captured in the formed image, wherein in the step of transmitting the photoluminescence light, the filter unit transmits the wavelength band including 420 nm or longer and 430 nm or shorter in the photoluminescence light, and in the step of discriminating the defect, when a thickness of the drift layer is defined as D 1 , a thickness of the buffer layer is defined as D 2 , an offset angle is defined as θ, and a first length and a second length are defined as L 1 and L 2 indicated respectively as follows:

L
⁢
1

=

(

D
⁢
1

+

D
⁢
2

)

/
tan
⁢
θ

L
⁢
2

=

D
⁢
2
/
tan
⁢
θ

,

the defect is discriminated as the defect including a basal plane dislocation continuing from the buffer layer to the drift layer in a case where a length of the defect belongs to a predetermined first range including the first length, and
the defect is discriminated as the defect including the basal plane dislocation in the buffer layer and an edge dislocation in the drift layer in the case where the length of the defect belongs to a predetermined second range including the second length, the second ran

Assignees

• Lasertec Corp

Inventors

• Fujiki Shota
• Ozaki Yoshito

Classifications

• H10P74/235

  comprising optical enhancement of defects or not-directly-visible states · CPC title

• H10P74/203 Primary

  Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects · CPC title

• G01N2021/646

  Detecting fluorescent inhomogeneities at a position, e.g. for detecting defects · CPC title

• G01N2021/8887

  based on image processing techniques · CPC title

• G01N2021/8477

  Investigating crystals, e.g. liquid crystals · CPC title