Heterodyne reflectometer for film thickness monitoring and method for implementing
First Claim
1. A heterodyne reflectometer for measuring thickness of a target layer deposed on a substrate comprising:
- an optical light source for producing a split frequency, dual polarized beam;
a beam path diverting optical component for propagating the split frequency, dual polarized beam toward an exposed target layer deposed on a substrate at a predetermined angle of incidence;
a first heterodyne detector for receiving the split frequency, dual polarized beam and generating a reference electrical heterodyne beat signal;
a second heterodyne detector for receiving a reflected split frequency, dual polarized beam from the target layer and generating a measurement electrical heterodyne beat signal;
a phase detector for receiving reference electrical heterodyne beat signal and the measurement electrical heterodyne beat signal, and detecting a phase shift between said reference and measurement electrical heterodyne beat signals; and
a data processor for calculating a thickness relating to the target layer from the phase shift.
1 Assignment
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Accused Products
Abstract
The present invention is directed to a heterodyne reflectometer system and method for obtaining highly accurate phase shift information from heterodyned optical signals, from which extremely accurate film depths can be calculated. A linearly polarized light comprised of two linearly polarized components that are orthogonal to each other, with split optical frequencies, is directed toward a film causing one of the optical polarization components to lag behind the other due to an increase in the optical path in the film for that component. A pair of detectors receives the beam reflected from the film layer and produces a measurement signal, and the beam prior to incidence on the film layer and generates a reference signal, respectively. The measurement signal and reference signal are analyzed by a phase detector for phase shift. The detected phase shift is then fed into a thickness calculator for film thickness results. A grating interferometer may be included with the heterodyne reflectometer system with a grating, which diffracts the reflected beam into zeroth- and first-order bands, which are then detected by separate detectors. A detector receives the zeroth-order beam and generates another measurement signal. Another detector receives the first-order beam and generates a grating signal. The measurement signal from the grating and reference signal may be analyzed by a phase detector for phase shift, which is related to the thickness of the film. Conversely, either measurement signal may be analyzed with the grating signal by a phase detector for detecting a grating phase shift. The refractive index for the film may be calculated from grating phase shift and the heterodyne phase shift. The updated refractive index is then used for calculating thickness.
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Citations
62 Claims
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1. A heterodyne reflectometer for measuring thickness of a target layer deposed on a substrate comprising:
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an optical light source for producing a split frequency, dual polarized beam; a beam path diverting optical component for propagating the split frequency, dual polarized beam toward an exposed target layer deposed on a substrate at a predetermined angle of incidence; a first heterodyne detector for receiving the split frequency, dual polarized beam and generating a reference electrical heterodyne beat signal; a second heterodyne detector for receiving a reflected split frequency, dual polarized beam from the target layer and generating a measurement electrical heterodyne beat signal; a phase detector for receiving reference electrical heterodyne beat signal and the measurement electrical heterodyne beat signal, and detecting a phase shift between said reference and measurement electrical heterodyne beat signals; and a data processor for calculating a thickness relating to the target layer from the phase shift. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A heterodyne reflectometer for measuring a thickness parameter for a target layer deposed on a substrate comprising:
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an optical light source for producing a split frequency, dual polarized beam, said split frequency, dual polarized beam having a first polarized beam component oscillating at a first frequency and a second polarized beam component oscillating at a second frequency, the first frequency being unique from the second frequency; a beam path diverting optical component for propagating the split frequency, dual polarized beam toward an exposed a target layer deposed on a substrate at a predetermined angle of incidence, said target layer having a surface and a body portion; a first detector for receiving the split frequency, dual polarized beam and generating a reference electrical heterodyne beat signal; a second detector for receiving a reflected split frequency, dual polarized beam from the target layer and generating a measurement electrical heterodyne beat signal, said reflected split frequency, dual polarized beam being comprised of predominately one of a reflected first polarized beam component and a reflected second polarized beam component from the surface of the target layer and predominately the other of the reflected first polarized beam component and the reflected second polarized beam component from below the surface of the target layer; and a phase detector for receiving reference electrical heterodyne beat signal and the measurement electrical heterodyne beat signal, and detecting a phase shift between said reference and measurement electrical heterodyne beat signals, said phase shift being induced by a thickness of said target layer body. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44)
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45. A reflectometry method for measuring a thickness parameter for a target layer deposed on a substrate comprising:
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directing an optical light source for producing a split frequency, dual polarized beam toward an exposed a target layer deposed on a substrate at a predetermined angle of incidence, said split frequency, dual polarized beam having a first polarized beam component oscillating at a first frequency and a second polarized beam component oscillating at a second frequency, the first frequency being unique from the second frequency, said target layer comprising a surface and a body; generating a reference electrical heterodyne beat signal by heterodyning the first polarized beam component oscillating at the first frequency and the second polarized beam component oscillating at the second frequency to produce a reference optical beat signal and converting the reference optical beat signal to the reference electrical heterodyne beat; receiving a reflected split frequency, dual polarized beam from the target layer; and generating a measurement electrical heterodyne beat signal by heterodyning a first reflected polarized beam component oscillating at the first frequency and a second reflected polarized beam component oscillating at the second frequency to produce a measurement optical beat signal and converting the measurement optical beat signal to the measurement electrical heterodyne beat; and detecting a phase shift between said reference electrical heterodyne beat signal and said measurement electrical heterodyne beat signal, said phase shift being induced by a thickness of said target layer body. - View Dependent Claims (46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62)
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Specification