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US 7,324,210 B2Granted
Scanning interferometry for thin film thickness and surface measurements
AssigneeZygo Corporation
InventorsPeter J. De Groot, Xavier Colonna De Lega
Life of this patent
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Abstract
A method including: providing a low coherence scanning interferometry data for at least one spatial location of a sample having multiple interfaces, wherein the data is collected using a low coherence scanning interferometer having an illumination geometry and an illumination frequency spectrum, and wherein the data comprises a low coherence scanning interferometry signal having multiple regions of fringe contrast corresponding to the multiple interfaces; and determining a distance between at least one pair of interfaces based on a distance between the corresponding regions of fringe contrast and information about the illumination geometry.
Claims35
A method comprising:
- providing a low coherence scanning interferometry data for multiple spatial locations of a sample having multiple interfaces, wherein the data is collected using a low coherence scanning interferometer having an illumination geometry and an illumination frequency spectrum, and wherein the data comprises a low coherence scanning interferometry signal having multiple regions of fringe contrast corresponding to the multiple interfaces;
- determining spatial information about the sample by, for each of the multiple spatial locations, determining a distance between at least one pair of the interfaces based on a distance between the corresponding regions of fringe contrast and information about the illumination geometry;
- and
- outputting information based on the determined spatial information;
- wherein the determined spatial information comprises at least one of:
- a thickness profile and a surface height profile.
3 more elements
An apparatus comprising:
- a low coherence scanning interferometer configured to collect data for multiple spatial locations of a sample having at least one film, the coherence scanning interferometer having an illumination geometry and an illumination frequency spectrum, and the data comprising, for each of the multiple spatial locations, a low coherence scanning interferometry signal having multiple regions of fringe contrast corresponding to the multiple interfaces;
- and
- an electronic processor configured to analyze the data and determine spatial information about the sample by, for each of the multiple spatial locations, determining a distance between at least a pair of the interfaces based on a distance between the corresponding regions of fringe contrast and information about the illumination geometry,
- wherein the determined spatial information comprises at least one of:
- a thickness profile and a surface height profile.
2 more elements
A method comprising:
- using a low coherence scanning interferometer having an illumination geometry and an illumination frequency spectrum to collect a low coherence scanning interferometry signal for each of multiple spatial locations of a sample having at least one thin film with a top surface and a bottom surface;
- selecting the illumination geometry and the illumination frequency spectrum to suppress a region of fringe contrast in the signals corresponding to the bottom surface relative to a region of fringe contrast in the signals corresponding to the top surface;
- determining a surface height profile for the top surface of the film based on the signals;
- and
- outputting information based on the determined surface height profile for the top surface of the film.
2 more elements
An apparatus comprising a low coherence scanning interferometer having an objective to illuminate the sample with a numerical aperture greater than 0.5 and a magnification less than 10×.
A method comprising:
- providing a low coherence scanning interferometry data for multiple spatial locations of a sample having multiple interfaces, wherein the data is collected using a low coherence scanning interferometer having an illumination geometry and an illumination frequency spectrum, and wherein the data comprises a low coherence scanning interferometry signal having multiple regions of fringe contrast corresponding to the multiple interfaces;
- and
- determining spatial information about the sample by, for each of the multiple spatial locations, determining a distance between at least one pair of the interfaces based on a distance between the corresponding regions of fringe contrast and information about the illumination geometry;
- and outputting information based on the determined spatial information;
- wherein determining the distance between at least one pair of interfaces comprises providing information about a correspondence between the distance between the pair of interfaces and the distance between the corresponding regions of fringe contrast in the interferometry signal for different settings of the illumination geometry and the illumination frequency spectrum;
- wherein the correspondence is based on a theoretical model for the interferometer that uses the information about the illumination geometry and the illumination frequency spectrum as input parameters;
- and
- wherein the theoretical model is based on the following expression for the interferometry signal I (ζ) as a function of scan coordinate ζ for each spatial location in the data:
- I
-
- (
- ζ
- )
- =
- ∫
- 0
- ∞
-
- ∫
- 0
- 1
-
- g
-
- (
- β
- ,
- k
- ,
- ζ
- )
-
- U
-
- (
- β
- )
-
- V
-
- (
- k
- )
-
- β
-
- ⅆ
- β
-
- ⅆ
- k
- where U is an illumination distribution in a pupil plane of an objective used to illuminate the sample as a function of directional cosine β, V is the illumination frequency spectrum as a function of spectral wavenumber k, and
- g
-
- (
- β
- ,
- k
- ,
- ζ
- )
- =
- R
- +
- Z
- +
- 2
-
- R
-
-
- Z
-
- cos
-
- [
- 2
-
- β
-
-
- k
-
- (
- h
- -
- ζ
- )
- +
- (
- υ
- -
- ω
- )
- ]
- for a reference path reflectivity R, a sample path reflectivity Z, and a local sample height h, and where phase offsets υ, ω are system and phase change on reflection values for the reference and sample paths, respectively.
93 more elements
Dependencies are inferred from the claim text.