Debris determination method
A debris determination method of determining, using an image obtained by an appearance inspection device, debris that occurs around a hard laser mark (HLM) on a backside of a wafer, including: a step of calculating reference luminance from a grayscale image obtained by the appearance inspection device; a step of extracting a printed region including the HLM from the grayscale image; a step of excluding a dot portion of the HLM from the printed region; a step of extracting, with reference to the reference luminance, a debris region from the printed region from which the dot portion of the HLM has been excluded; and a step of determining the presence or absence of debris in the printed region based on the debris region. This provides a debris determination method that can reliably detect debris that cannot be detected by shape measuring devices and determine the presence or absence of debris.
1 . A debris determination method of determining, using an image obtained by an appearance inspection device, debris that occurs around a hard laser mark on a backside of a wafer after the hard laser mark is formed on the backside or after the backside is polished after formation of the hard laser mark, comprising:
a step A of calculating reference luminance from a grayscale image obtained by the appearance inspection device;
a step B of extracting a hard laser mark-printed region including the hard laser mark from the grayscale image;
a step C of excluding a dot portion of the hard laser mark from the extracted hard laser mark-printed region;
a step D of extracting, with reference to the reference luminance, a region of the debris from the hard laser mark-printed region from which the dot portion of the hard laser mark has been excluded; and
a step E of determining presence or absence of the debris in the hard laser mark-printed region based on the extracted region of the debris.
2 . The debris determination method according to claim 1 ,
wherein in the step A,
an average value of luminance of a portion in the grayscale image where the hard laser mark is not imprinted is calculated as the reference luminance.
3 . The debris determination method according to claim 1 ,
wherein in the step B,
a threshold (identification frame) of pixel luminance is set in advance that enables detection of a white identification frame appearing to surround the hard laser mark-printed region in the grayscale image,
a region at or above the threshold (identification frame) is determined and detected as the white identification frame, and
a region surrounded by the detected white identification frame is extracted as the hard laser mark-printed region.
4 . The debris determination method according to claim 2 ,
wherein in the step B,
a threshold (identification frame) of pixel luminance is set in advance that enables detection of a white identification frame appearing to surround the hard laser mark-printed region in the grayscale image,
a region at or above the threshold (identification frame) is determined and detected as the white identification frame, and
a region surrounded by the detected white identification frame is extracted as the hard laser mark-printed region.
5 . The debris determination method according to claim 1 ,
wherein in the step C,
from a relationship between a dot region that constitutes the hard laser mark and pixel luminance of the dot region, a threshold (dot region) of pixel luminance is set in advance that enables extraction of only the dot region,
a region with pixel luminance at or below the threshold (dot region) is determined and extracted as the dot region, and
a region expanded by one or more pixels around a periphery of the extracted dot region is excluded as the dot portion.
6 . The debris determination method according to claim 2 ,
wherein in the step C,
from a relationship between a dot region that constitutes the hard laser mark and pixel luminance of the dot region, a threshold (dot region) of pixel luminance is set in advance that enables extraction of only the dot region,
a region with pixel luminance at or below the threshold (dot region) is determined and extracted as the dot region, and
a region expanded by one or more pixels around a periphery of the extracted dot region is excluded as the dot portion.
7 . The debris determination method according to claim 3 ,
wherein in the step C,
from a relationship between a dot region that constitutes the hard laser mark and pixel luminance of the dot region, a threshold (dot region) of pixel luminance is set in advance that enables extraction of only the dot region,
a region with pixel luminance at or below the threshold (dot region) is determined and extracted as the dot region, and
a region expanded by one or more pixels around a periphery of the extracted dot region is excluded as the dot portion.
8 . The debris determination method according to claim 4 ,
wherein in the step C,
from a relationship between a dot region that constitutes the hard laser mark and pixel luminance of the dot region, a threshold (dot region) of pixel luminance is set in advance that enables extraction of only the dot region,
a region with pixel luminance at or below the threshold (dot region) is determined and extracted as the dot region, and
a region expanded by one or more pixels around a periphery of the extracted dot region is excluded as the dot portion.
9 . The debris determination method according to claim 1 ,
wherein in the step D,
a relationship between a higher luminance debris which is debris with higher luminance than the reference luminance and pixel luminance of the higher-luminance debris and a relationship between a lower-luminance debris which is debris with lower luminance than the reference luminance and pixel luminance of the lower-luminance debris are obtained in advance, and a threshold (higher-luminance debris) of pixel luminance that enables extraction of the higher-luminance debris with reference to the reference luminance and a threshold (lower-luminance debris) of pixel luminance that enables extraction of the lower-luminance debris with reference to the reference luminance are set in advance, and
a region with pixel luminance at or above the threshold (higher-luminance debris) and a region with pixel luminance at or below the threshold (lower-luminance debris) are determined and extracted as the region of debris.
10 . The debris determination method according to claim 2 ,
wherein in the step D,
a relationship between a higher-luminance debris which is debris with higher luminance than the reference luminance and pixel luminance of the higher-luminance debris and a relationship between a lower luminance debris which is debris with lower luminance than the reference luminance and pixel luminance of the lower-luminance debris are obtained in advance, and a threshold (higher-luminance debris) of pixel luminance that enables extraction of the higher-luminance debris with reference to the reference luminance and a threshold (lower-luminance debris) of pixel luminance that enables extraction of the lower-luminance debris with reference to the reference luminance are set in advance, and
a region with pixel luminance at or above the threshold (higher-luminance debris) and a region with pixel luminance at or below the threshold (lower-luminance debris) are determined and extracted as the region of debris.
11 . The debris determination method according to claim 3 ,
wherein in the step D,
a relationship between a higher-luminance debris which is debris with higher luminance than the reference luminance and pixel luminance of the higher-luminance debris and a relationship between a lower luminance debris which is debris with lower luminance than the reference luminance and pixel luminance of the lower-luminance debris are obtained in advance, and a threshold (higher-luminance debris) of pixel luminance that enables extraction of the higher-luminance debris with reference to the reference luminance and a threshold (lower-luminance debris) of pixel luminance that enables extraction of the lower-luminance debris with reference to the reference luminance are set in advance, and
a region with pixel luminance at or above the threshold (higher-luminance debris) and a region with pixel luminance at or below the threshold (lower-luminance debris) are determined and extracted as the region of debris.
12 . The debris determination method according to claim 4 ,
wherein in the step D,
a relationship between a higher-luminance debris which is debris with higher luminance than the reference luminance and pixel luminance of the higher-luminance debris and a relationship between a lower luminance debris which is debris with lower luminance than the reference luminance and pixel luminance of the lower-luminance debris are obtained in advance, and a threshold (higher-luminance debris) of pixel luminance that enables extraction of the higher-luminance debris with reference to the reference luminance and a threshold (lower-luminance debris) of pixel luminance that enables extraction of the lower-luminance debris with reference to the reference luminance are set in advance, and
a region with pixel luminance at or above the threshold (higher-luminance debris) and a region with pixel luminance at or below the threshold (lower-luminance debris) are determined and extracted as the region of debris.
13 . The debris determination method according to claim 5 ,
wherein in the step D,
a relationship between a higher luminance debris which is debris with higher luminance than the reference luminance and pixel luminance of the higher-luminance debris and a relationship between a lower luminance debris which is debris with lower luminance than the reference luminance and pixel luminance of the lower-luminance debris are obtained in advance, and a threshold (higher-luminance debris) of pixel luminance that enables extraction of the higher-luminance debris with reference to the reference luminance and a threshold (lower-luminance debris) of pixel luminance that enables extraction of the lower-luminance debris with reference to the reference luminance are set in advance, and
a region with pixel luminance at or above the threshold (higher-luminance debris) and a region with pixel luminance at or below the threshold (lower-luminance debris) are determined and extracted as the region of debris.
14 . The debris determination method according to claim 6 ,
wherein in the step D,
a relationship between a higher-luminance debris which is debris with higher luminance than the reference luminance and pixel luminance of the higher-luminance debris and a relationship between a lower luminance debris which is debris with lower luminance than the reference luminance and pixel luminance of the lower-luminance debris are obtained in advance, and a threshold (higher-luminance debris) of pixel luminance that enables extraction of the higher-luminance debris with reference to the reference luminance and a threshold (lower-luminance debris) of pixel luminance that enables extraction of the lower-luminance debris with reference to the reference luminance are set in advance, and
a region with pixel luminance at or above the threshold (higher-luminance debris) and a region with pixel luminance at or below the threshold (lower-luminance debris) are determined and extracted as the region of debris.
15 . The debris determination method according to claim 7 ,
wherein in the step D,
a relationship between a higher-luminance debris which is debris with higher luminance than the reference luminance and pixel luminance of the higher-luminance debris and a relationship between a lower luminance debris which is debris with lower luminance than the reference luminance and pixel luminance of the lower-luminance debris are obtained in advance, and a threshold (higher-luminance debris) of pixel luminance that enables extraction of the higher-luminance debris with reference to the reference luminance and a threshold (lower-luminance debris) of pixel luminance that enables extraction of the lower-luminance debris with reference to the reference luminance are set in advance, and
a region with pixel luminance at or above the threshold (higher-luminance debris) and a region with pixel luminance at or below the threshold (lower-luminance debris) are determined and extracted as the region of debris.
16 . The debris determination method according to claim 8 ,
wherein in the step D,
a relationship between a higher-luminance debris which is debris with higher luminance than the reference luminance and pixel luminance of the higher-luminance debris and a relationship between a lower luminance debris which is debris with lower luminance than the reference luminance and pixel luminance of the lower-luminance debris are obtained in advance, and a threshold (higher-luminance debris) of pixel luminance that enables extraction of the higher-luminance debris with reference to the reference luminance and a threshold (lower-luminance debris) of pixel luminance that enables extraction of the lower-luminance debris with reference to the reference luminance are set in advance, and
a region with pixel luminance at or above the threshold (higher-luminance debris) and a region with pixel luminance at or below the threshold (lower-luminance debris) are determined and extracted as the region of debris.
17 . The debris determination method according to claim 1 ,
wherein in the step E,
a relationship between an area ratio of the region of debris in the hard laser mark-printed region and quality defects caused by debris in a device manufacturing process is obtained in advance, and a threshold (presence of debris) of the area ratio of the region of debris at which the quality defects caused by debris occur is set in advance,
the area ratio of the region of debris in the hard laser mark-printed region is obtained from a number of pixels in the extracted region of debris, and
when the area ratio of the region of debris which is obtained from the number of pixels in the extracted region of debris is at or above the threshold (presence of debris), it is determined that debris is present.