Chip defect detection device and detection method
View Patent ↗An apparatus and method for die defect detection are disclosed. The apparatus includes: a light source unit ( 10 ) for emitting light of at least two wavelengths; a beam splitter ( 40 ) for receiving the light emitted by the light source unit ( 10 ) and splitting it into a first portion and a second portion, the first portion of the light reflected by a die ( 60 ) surface under inspection and thereby forming a detection beam; a reference unit ( 70 ) for receiving the second portion of the light and processing it into a reference beam; and a detection unit ( 90 ) for receiving the detection beam and the reference beam. The reference beam crosses the detection beam at an angle and thus produces interference fringes on a sensing surface of the detection unit ( 90 ), based on which a defect parameter of the die ( 60 ) surface under inspection is determined. This apparatus is capable of measuring a die with improved accuracy and efficiency and is suitable for the measurement of large dies.
1. An apparatus for die defect detection, comprising:
a light source unit for emitting light of two wavelengths;
a beam splitter for splitting the light emitted by the light source unit into a first portion and a second portion, the first portion reflected by a die surface under inspection and thereby forming a detection beam;
a reference unit having a surface configured to receive the second portion of the light and thereby form a reference beam; and
a detection unit for receiving the detection beam and the reference beam, wherein the reference beam crosses the detection beam at an angle and thus forming interference signals on a sensing surface of the detection unit, and wherein a defect parameter of the die surface under inspection is determined based on the interference signals;
wherein intensities, detected by the detection unit, of light with a shorter wavelength and of light with a synthetic wavelength generated from the two wavelengths respectively satisfy:
I
1
≈
cos
(
2
π
λ
1
·
2
(
z
+
x
·
sin
θ
)
)
;
I
2
≈
cos
[
(
2
π
λ
1
-
2
π
λ
2
)
·
2
(
z
+
x
·
sin
θ
)
]
=
cos
[
2
π
λ
2
-
λ
1
λ
1
λ
2
·
2
(
z
+
x
·
sin
θ
)
]
,
where: I 1 represents the intensity of the light with the shorter wavelength λ 1 ; I 2 represents the intensity of the light with the synthetic wavelength generated from the two wavelengths λ 1 and λ 2 ; θ represents an angle at which the surface of the reference unit is inclined with respect to a vertical direction perpendicular to the die surface under inspection; z represents a height of a measurement point on the die surface under inspection; and x represents a horizontal position of a sensing pixel in the detection unit.
2. The apparatus for die defect detection of claim 1 , wherein the detection unit comprises at least one detector for detecting the interference signals.
3. The apparatus for die defect detection of claim 2 , wherein the detection unit comprises a plurality of detectors, each configured for the detection of light with a corresponding one of the wavelengths.
4. The apparatus for die defect detection of claim 2 , wherein the detector is implemented as a complementary metal oxide semiconductor or charge-coupled device image sensor.
5. The apparatus for die defect detection of claim 1 , wherein the reference unit comprises a reflective element having a surface for receiving the second portion of the light and forming the reference beam, the surface of the reflective element inclined at an angle with respect to a vertical direction perpendicular to the die surface under inspection.
6. The apparatus for die defect detection of claim 1 , wherein the light with the shorter wavelength λ 1 determines a resolution of the apparatus for die defect detection, with the light with the synthetic wavelength generated from the two wavelengths determining a vertical measurement range of the apparatus for die defect detection, the resolution and the vertical measurement range of the apparatus for die defect detection given by the following equations:
R 0 =λ 1 /2/SNR;
Z 0 =λ S /2,
where: R 0 represents the resolution of the apparatus for die defect detection; SNR represents a signal-to-noise ratio of the apparatus for die defect detection; Z 0 represents the vertical measurement range of the apparatus for die defect detection; and λ S represents the synthetic wavelength generated from the two wavelengths λ 1 and λ 2 .
7. The apparatus for die defect detection of claim 1 , further comprising an objective lens for magnifying the die surface under inspection, the objective lens disposed between the beam splitter and the die surface under inspection.
8. A method for die defect detection using the apparatus for die defect detection as defined in claim 1 , the method comprising:
emitting light of two wavelengths by a light source unit;
splitting, by a beam splitter, the light emitted by the light source unit into a first portion and a second portion, the first portion reflected by a die surface under inspection and thereby forming a detection beam, the second portion forming a reference beam through a reference unit; and
detecting, by a detection unit, interference signals generated by the detection beam and the reference beam, and determining a defect parameter of the die surface under inspection.
9. An apparatus for die defect detection, comprising:
a light source unit for emitting light of three wavelengths denoted respectively as λ 1 , λ 2 and λ 3 ;
a beam splitter for splitting the light emitted by the light source unit into a first portion and a second portion, the first portion reflected by a die surface under inspection and thereby forming a detection beam;
a reference unit having a surface configured to receive the second portion of the light and thereby form a reference beam; and
a detection unit for receiving the detection beam and the reference beam, wherein the reference beam crosses the detection beam at an angle and thus forming interference signals on a sensing surface of the detection unit, and wherein a defect parameter of the die surface under inspection is determined based on the interference signals;
wherein the detection unit comprises a number of superpixels, each of the superpixels comprising a plurality of pixels, each of the pixels configured to measure an intensity given by:
I
(
x
,
y
)
=
A
1
2
+
B
1
2
+
2
A
1
B
1
cos
(
θ
x
,
y
,
1
+
φ
1
)
+
A
2
2
+
B
2
2
+
2
A
2
B
2
cos
(
θ
x
,
y
,
2
+
φ
2
)
+
A
3
2
+
B
3
2
+
2
A
3
B
3
cos
(
θ
x
,
y
,
3
+
φ
3
)
;
where: (x, y) represents a coordinate of the pixel; B 1 , B 2 and B 3 represent coefficients of the wavelengths λ 1 , λ 2 and λ 3 of the light in relation to transmission and reflection thereof; A 1 , A 2 and A 3 represent coefficients of the wavelengths λ 1 , λ 2 and λ 3 of the light in relation to reflectance of the die surface under inspection; φ 1 , φ 2 and φ 3 represent initial phases of the wavelengths λ 1 , λ 2 and λ 3 of the light; I(x, y) represents the intensity detected by the pixel at the coordinate (x, y); and θ x,y,i represents an angle between light with the wavelength λ i reflected back from the reference unit and light with the wavelength λ i reflected back from the die surface under inspection, measured by the pixel at the coordinate (x, y), where i=1, 2, 3.
10. The apparatus for die defect detection of claim 9 , wherein the defect parameter of the die surface under inspection is determined by an FFT algorithm.