US2008137078A1PendingUtilityA1
Measuring a damaged structure formed on a wafer using optical metrology
Est. expiryMar 30, 2026(expired)· nominal 20-yr term from priority
H10P 74/203G01N 21/88G01N 21/00G01N 21/9501G01N 21/4788G01N 21/95607
53
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Claims
Abstract
A method of measuring a damaged structure formed on a semiconductor wafer using optical metrology, the method includes obtaining a measured diffraction signal from a damaged periodic structure. A hypothetical profile of the damaged periodic structure is defined. The hypothetical profile having an undamaged portion, which corresponds to an undamaged area of a first material in the damaged periodic structure, and a damaged portion, which corresponds to a damaged area of the first material in the damaged periodic structure. The undamaged portion and the damaged portion have different properties associated with them. A simulated diffraction signal is calculated for the hypothetical damaged periodic structure using the hypothetical profile. The measured diffraction signal is compared to the simulated diffraction signal. If the measured diffraction signal and the simulated diffraction signal match within a matching criterion, then a damage amount for the damaged periodic structure is established based on the damaged portion of the hypothetical profile used to calculate the simulated diffraction signal.
Claims
exact text as granted — not AI-modified1 - 16 . (canceled)
17 : A method of generating the diffracted reflectivity associated with diffraction of electromagnetic radiation off a damaged periodic structure, the method comprising:
defining a hypothetical profile of the damaged periodic structure, the hypothetical profile having an undamaged portion, which corresponds to an undamaged area of a first material in the damaged periodic structure, and a damaged portion, which corresponds to a damaged area of the first material in the damaged periodic structure damaged, and wherein the undamaged portion and the damaged portion have different properties associated with them; dividing the hypothetical profile of the damaged periodic structure into a plurality of hypothetical layers, wherein each hypothetical layer comprises a first material, or a second material, or a damaged dielectric material, or an undamaged dielectric material, or a combination of two or more thereof, wherein at least one of the hypothetical layers comprises a first material, a damaged dielectric material, and an undamaged dielectric material; generating sets of hypothetical layer data, each set of hypothetical layer data corresponding to a separate one of the plurality of hypothetical layers; and processing the generated sets of hypothetical layer data to generate the diffracted reflectivity that would occur by reflecting electromagnetic radiation off the damaged periodic structure.
18 : The method of claim 17 , further comprising subdividing the hypothetical layers into a plurality of slabs, each slab corresponding to the intersection of one of the plurality of layers with one of at least the first material, the second material, the undamaged material, and the damaged material.
19 : The method of claim 17 , wherein hypothetical profile is divided into the plurality of hypothetical profile in a direction corresponding to a direction of periodicity of the damaged periodic structure.
20 : The method of claim 17 , wherein the step of generating sets of hypothetical layer data includes expanding at least one of either a function of a real space permittivity and a function of a real space inverse permittivity of the hypothetical layers in a one-dimensional Fourier transformation along a direction of periodicity of the damaged periodic structure to provide harmonic components of the at least one of either a function of a real space permittivity and a function of a real space inverse permittivity of the hypothetical layers.
21 : The method of claim 17 , wherein the step of generating sets of hypothetical layer data includes computing at least one of:
permittivity properties including a function of a permittivity ∈ l (x) of each of the hypothetical layers, the harmonic components ∈ l,I of the function of the permittivity π 1 (x), and a permittivity harmonics matrix [π 1 ]; and inverse-permittivity properties including a function of an inverse-permittivity π 1 (x) of each of the hypothetical layers, the harmonic components π l,i of the function of the inverse-permittivity π l (x), and an inverse-permittivity harmonics matrix [P l ].
22 : The method of claim 21 , wherein the step of processing the generated sets of hypothetical layer data includes:
computing a wave-vector matrix [A l ] by combining a series expansion of the electric field of each of the hypothetical layers with at least one of at least the permittivity harmonics matrix [E l ] and inverse-permittivity harmonics matrix [P l ]; and computing the i th entry w l,i,m of the m th eigenvector of the wave-vector matrix [A l ] and the m th eigenvalue τ l,m of the wave-vector matrix [A l ] to form an eigenvector matrix [W l ] and a root-eigenvalue matrix [Q l ].
23 : The method of claim 17 , wherein the step of generating sets of hypothetical layer data includes expanding at least one of a function of a permittivity ∈ l (x), and a function of an inverse-permittivity π l (x)=1/∈ l (x) of at least one of the hypothetical layers that comprises a first material, or a second material, or an undamaged material, or a damaged material, or a combination of two or more thereof in a one-dimensional Fourier transformation, the expansion performed along a direction of periodicity of the damaged periodic structure according to at least one of:
ɛ
l
(
x
)
=
∑
i
=
-
∞
∞
ɛ
l
,
i
exp
(
j
2
π
D
x
)
where
ɛ
l
,
i
=
∑
k
=
1
r
n
k
2
-
j2π
[
(
cos
(
2
π
D
x
k
)
-
cos
(
2
π
D
x
k
-
1
)
)
-
j
(
sin
(
2
π
D
x
k
)
-
sin
(
2
π
D
x
k
-
1
)
)
]
and
π
l
(
x
)
=
1
ɛ
l
(
x
)
=
∑
i
=
-
∞
∞
π
l
,
i
exp
(
j
2
π
D
x
)
where
π
l
,
i
=
∑
k
=
1
r
1
-
j2π
1
n
k
2
(
(
cos
(
2
π
D
x
k
)
-
cos
(
2
π
D
x
k
-
1
)
)
-
j
(
sin
(
2
π
D
x
k
)
-
sin
(
2
π
D
x
k
-
1
)
)
)
where D is the pitch of the damaged periodic structure, n k is the index of refraction of a material between material boundaries at x k and x k-1 , j is the imaginary number defined as the square root of −1, and there are r of the material boundaries within each period of the damaged periodic structure.
24 : The method of claim 17 , wherein the step of processing the generated sets of hypothetical layer data includes:
constructing a matrix equation from the intermediate data corresponding to the hypothetical layers; and solving the constructed matrix equation to determine the diffracted reflectivity value R i for each harmonic order i.
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