Interferometry method and apparatus for producing lateral metrology images
AssigneeZygo Corporation
InventorPeter J. De Groot
Life of this patent
Estimating the term…
Abstract
A method including: generating a sequence of phase-shifted interferometry images of an object surface relative to a reference surface; and calculating an unequally weighted average of the phase-shifted interferometry images to produce a final image. The final image can be useful as a lateral metrology image. The method may further include calculating a surface topography image from the sequence of phase-shifted interferometry images. Embodiments further include apparatus related to the method.
Claims38
A method comprising:
- generating a sequence of phase-shifted interferometry images of an object surface relative to a reference surface;
- and
- calculating an unequally weighted average of the phase-shifted interferometry images to produce a final image, wherein the final image is a lateral metrology image.
A method comprising:
- generating a sequence of phase-shifted interferometry images of an object surface relative to a reference surface;
- and
- calculating an unequally weighted average of the phase-shifted interferometry images to produce a final image,
- wherein the sequence of phase-shifted interferometry images can be expressed mathematically as:
- gi,j(θi,v)=Qi(1+V cos(θi+vφj))
- where gi,j is an intensity for the ith pixel of the jth image in the sequence, θi is a phase for the ith pixel of the object surface relative to the reference surface, where v is a phase shift frequency with respect to a nominal phase shift sequence, Qi is a DC level for the ith pixel, V is a fringe contrast, and φj is a nominal phase shift for the jth image in the sequence,
- wherein the final image, Ai, can be expressed as:
- A
- i
-
- (
- θ
- i
- ,
- v
- )
- =
- ∑
- j
-
- w
- j
-
- g
- i
- ,
- j
-
- (
- θ
- i
- ,
- v
- )
- /
- ∑
- j
-
- w
- j
- ,
- where wj is a sequence of coefficients defining the unequally weighted average, and wherein the unequally weighted average requires wj to not be constant for all j,
- wherein φj=(j−j0)α, where j=0, . . . , P−1, P is the number of images in the sequence, α is a constant phase shift interval, and j0 is a constant selected to cause φ(P−1)−j=−φj, and
- wherein wj satisfies:
- W
-
- (
- v
- =
- 1
- )
- =
- 0
-
-
- and
-
-
- ∂
- W
-
- (
- v
- )
- ∂
- v
-
-
- v
- =
- 1
-
- =
- 0
- ,
- where
-
-
- W
-
- (
- v
- )
- =
- ∑
- j
-
- w
- j
-
- cos
-
-
- (
- v
-
-
- ϕ
- j
- )
- .
A method comprising calculating an unequally weighted average of a sequence of phase-shifted interferometry images to produce a final image, wherein the final image is a lateral metrology image.
An apparatus comprising a computer readable medium which causes a processor to calculate an unequally weighted average of a sequence of phase-shifted interferometry images to produce a final image, wherein the final image is a lateral metrology image.
An apparatus comprising:
- an interferometer which during operation generates a sequence of phase-shifted interferometry images of an object surface relative to a reference surface;
- and
- means, coupled to the interferometer, for calculating an unequally weighted average of the phase-shifted interferometry images to produce a final image, wherein the final image is a lateral metrology image.
An method for obtaining a fringe-free intensity image from a sequence of phase-shifted interference patterns, the method comprising:
- providing the sequence of phase-shifted interference patterns;
- and
- calculating a weighted average of the phase-shifted interference patterns to produce the fringe-free intensity image.
An interferometry system comprising:
- an interferometer for providing a sequence of phase-shifted interference patterns;
- and
- means, coupled to the interferometer, for calculating a weighted average of the phase-shifted interference patterns to produce a fringe-free intensity image.
Dependencies are inferred from the claim text.