Method for inspecting a foreign matter on mirror-finished substrate
View Patent ↗Provided is a foreign matter inspection method for positively detecting a foreign matter in the neighborhood of the edge of a mirror-finished substrate without fail. Edge-emphasis and binarization are performed following the taking of an image of a substrate-under-inspection at a contour of its inspection area, to further detect a plurality of sampling points representative of a contour of the inspection area. An estimated inspection area is determined by determining the size, position and rotation angle of contour lines defined, size-reducibly, from the coordinates of the plurality of sampling points. After applying a mask to the binary image data in an area other than the estimated inspection area, a foreign-matter detection step is performed.
1. A method for inspecting foreign matter on a mirror-finished substrate-under-inspection, comprising:
emitting illumination light to the substrate-under-inspection;
obtaining image data based on an image which includes irregular reflection light that has been irregularly reflected from the substrate-under-inspection;
performing arithmetic operation, using a microprocessor, based on either one of operational expressions given in (equation 1), (equation 2) or (equation 3) provided that a light-intensity value of a desired one pixel of the image data as P(i, j) (where “i”, “j”: an integer for specifying a desired position wherein “i” indicates an arrangement order in a direction of X-axis while “j” indicates an arrangement order in a direction of Y-axis), a mean value over a desired pixel and its peripheral pixels of the image data as M(i, j) and a deviation value over a desired pixel and its peripheral pixels of the image data as S(i, j),
P
(
i
,
j
)
=
max
[
P
(
i
+
1
,
j
-
1
)
-
P
(
i
-
1
,
j
-
1
)
+
P
(
i
+
1
,
j
)
-
P
(
i
-
1
,
j
)
+
P
(
i
+
1
,
j
+
1
)
-
P
(
i
-
1
,
j
+
1
)
,
P
(
i
-
1
,
j
+
1
)
-
P
(
i
-
1
,
j
-
1
)
+
P
(
i
,
j
+
1
)
-
P
(
i
,
j
-
1
)
+
P
(
i
+
1
,
j
+
1
)
-
P
(
i
+
1
,
j
-
1
)
]
Equation
1
(where right-side operation represents to employ the greater one of two term's values (absolute value) segmented by an in-bracket commas, i.e. of the upper and lower terms)
P
(
i
,
j
)
=
max
[
P
(
i
+
1
,
j
-
1
)
-
P
(
i
-
1
,
j
-
1
)
+
2
P
(
i
+
1
,
j
)
-
2
P
(
i
-
1
,
j
)
+
P
(
i
+
1
,
j
+
1
)
-
P
(
i
-
1
,
j
+
1
)
,
P
(
i
-
1
,
j
+
1
)
-
P
(
i
-
1
,
j
-
1
)
+
2
P
(
i
,
j
+
1
)
-
2
P
(
i
,
j
-
1
)
+
P
(
i
+
1
,
j
+
1
)
-
P
(
i
+
1
,
j
-
1
)
]
Equation
2
(where right-side operation represents to employ the greater one of two term's values (absolute value) segmented by an in-bracket commas, i.e. of the upper and lower terms),
If | P (i,j) −M (i,j) |>S (i,j) , Equation 3
then P (i,j) =P (i,j) .
If | P (i,j) −M (i,j) |<S (i,j) ,
then P (i,j) =M (i,j) .
Here,
M (i,j) = 1/9( P (i−1,j−1) +P (i,j−1) +P i+1,j−1) +P (i−1,j) +P (i,j) +P i+1,j) +P (i−1,j+1) +P (i,j+1) +P (i+1,j+1) )
S 2 (i,j) = 1/9( P 2 (i−1,j−1) +P 2 (i,j−1) +P 2 (i+1,j−1) +P 2 (i−1,j) +P 2 (i,j) +P 2 (i+1,j) +P 2 (i−1,j+1) +P 2 (i,j+1) +P 2 (i+1,j+1) )− M 2 (i,j)
detecting coordinates of a plurality of contour sampling points indicative of a contour of an inspection area from the image data;
estimating the inspection area from the coordinates of the plurality of contour sampling points;
preparing mask image data where masking is applied to an area other than the inspection area by use of the image data the image-processing has been done; and
performing foreign-matter detection on the image data by using the mask image data.
2. The method of claim 1 , wherein the image data, where the contour of the inspection area of the substrate-under-inspection has been taken an image, is binary image that binarization has been done.
3. The method of claim 1 , wherein the contour line is estimated so as to minimize a square sum of distances between coordinates of the plurality of contour sampling points and the contour line of the inspection area of the substrate-under-inspection.
4. The method of claim 1 , wherein a reflection member that has been irregularly reflective of light or a light-emission member for emitting light spontaneously is provided in a neighborhood of the substrate-under-inspection, and
the image data being produced such that an image of the reflection member or light-emission member is displayed in a background of the substrate-under-inspection, in the image data where an area broader than the inspection area of the substrate-under-inspection has been taken an image.
5. The method of claim 2 , wherein the contour line is estimated so as to minimize a square sum of distances between coordinates of the plurality of contour sampling points and the contour line of the inspection area of the substrate-under-inspection.
6. The method of claim 2 , wherein a reflection member that has been irregularly reflective of light or a light-emission member for emitting light spontaneously is provided in a neighborhood of the substrate-under-inspection, and
the image data being produced such that an image of the reflection member or light-emission member is displayed in a background of the substrate-under-inspection, in the image data where an area broader than the inspection area of the substrate-under-inspection has been taken an image.