Patent US5465148A successfully refreshed from Google Patents.
US5465148A
Expired / Lapsed
US
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Apparatus and method for detecting the relative positional deviation between two diffraction gratings
Assignee: Canon Inc
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Filing: 1993-10-21
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Granted: 1995-11-07
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Expires: 2013-10-21
Abstract
Abstract A first Savart plate and an object to be measured are arranged on the light path of a Zeeman light source. The object to be measured is constructed of a diffraction grating on a mask and a diffraction grating on a wafer. A second Savart plate, a deflection plate and a photoelectric detector are sequentially arranged in the light path for the diffracted beams from the measured object. The output of the photoelectric detector is connected to a phase-difference unit to detect the phase difference between two beat signals. Herein, the light is split into two beams by the Savart plate. After a diffraction is caused by the diffraction gratings, thereafter, the beams are re-synthesized by the Savart plates. The two beams travel on the same light path, thereby improving a measurement accuracy.
Inventors
- 👤 Takahiro Matsumoto
- 👤 Noriyuki Nose
- 👤 Kenji Saito
- 👤 Koichi Sentoku
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 19:29
CPC Classifications
G; G03; G03F; G03F7/00; G03F7/70; G03F7/70483; G03F7/70605; G03F7/70616; G03F7/70633; G03F9/00; G03F9/70
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
108 words
A method of detecting the relative positional deviation between two diffraction gratings, said method comprising the steps of: splitting a light beam into two light beams; causing one of the two light beams to enter one of the two diffraction gratings, and causing the other light beam to enter the other diffraction grating; causing +nth-order diffracted beams diffracted by the two diffraction gratings to interfere with each other, and causing -nth-order diffracted beams diffracted by the two diffraction gratings to interfere with each other, thereby forming two interference signals; and detecting the relative positional deviation between the two diffraction gratings on the basis of the two interference signals.
Claim 2
Independent Claim
108 words
A method of detecting the relative positional deviation between two diffraction gratings, said method comprising the steps of: splitting a light beam into two light beams; causing one of the two light beams to enter one of the two diffraction gratings, and causing the other light beam to enter the other diffraction grating; causing +nth-order diffracted beams diffracted by the two diffraction gratings to interfere with each other, and causing -nth-order diffracted beams diffracted by the two diffraction gratings to interfere with each other, thereby forming two interference signals; and detecting the relative positional deviation between the two diffraction gratings on the basis of the two interference signals.
Claim 3
Dependent Claim
24 words
A method according to claim 1, wherein said splitting step includes the step of causing the one light beam to enter a Savart plate.
Claim 4
Dependent Claim
23 words
A method according to claim 2, wherein the two diffraction gratings and the Savart plate are disposed so as to be optically conjugate.
Claim 5
Dependent Claim
23 words
A method according to claim 1, wherein the one light beam includes polarized light beams orthogonal to each other and having different frequencies.
Claim 6
Dependent Claim
31 words
A method according to claim 1, wherein each interference signal is a beat signal, and said detecting step includes the step of detecting a phase difference between the two beat signals.
Claim 7
Dependent Claim
25 words
A method according to claim 1, wherein one diffraction grating is formed on a mask, and the other diffraction grating is formed on a wafer.
Claim 8
Dependent Claim
22 words
A method according to claim 1, wherein the two diffraction gratings are formed on a substrate by processes different from each other.
Claim 9
Dependent Claim
30 words
A method according to claim 1, wherein the +nth-order diffracted beams are mixed and the -nth-order diffracted beams are mixed by a Savart plate, thereby forming the interference signals, respectively.
Claim 10
Dependent Claim
32 words
An apparatus according to claim 1, wherein said detecting means includes a Savart plate for mixing the +nth-order diffracted beams and mixing the -nth-order diffracted beams to form the interference signals, respectively.
Claim 11
Independent Claim
138 words
An apparatus for detecting the relative positional deviation between two diffraction gratings, said apparatus comprising: a light source for emitting light; means for splitting a light beam from said light source into two light beams; means for detecting two interference signals by causing one of the two light beams to enter one of the two diffraction gratings and the other light beam to enter the other of the two diffracting gratings, causing +nth-order diffracted beams diffracted by the two diffraction gratings to interfere with each other to form one interference signal, and causing the -nth-order diffracted beams diffracted by the two diffraction gratings to interfere with each other to form another interference signal; and means for measuring the relative positional deviation between the two diffraction gratings on the basis of the two interference signals from said detecting means.
Claim 12
Independent Claim
138 words
An apparatus for detecting the relative positional deviation between two diffraction gratings, said apparatus comprising: a light source for emitting light; means for splitting a light beam from said light source into two light beams; means for detecting two interference signals by causing one of the two light beams to enter one of the two diffraction gratings and the other light beam to enter the other of the two diffracting gratings, causing +nth-order diffracted beams diffracted by the two diffraction gratings to interfere with each other to form one interference signal, and causing the -nth-order diffracted beams diffracted by the two diffraction gratings to interfere with each other to form another interference signal; and means for measuring the relative positional deviation between the two diffraction gratings on the basis of the two interference signals from said detecting means.
Claim 13
Dependent Claim
14 words
An apparatus according to claim 10, wherein said splitting means includes a Savart plate.
Claim 14
Dependent Claim
23 words
An apparatus according to claim 10, wherein the two diffraction gratings and said Savart plate are disposed so as to be optically conjugate.
Claim 15
Dependent Claim
23 words
An apparatus according to claim 10, wherein the one light beam includes polarized light beams orthogonal to each other and having different frequencies.
Claim 16
Dependent Claim
30 words
An apparatus according to claim 10, wherein each interference signal is a beat signal, and said measuring means includes means for detecting a phase difference between the two beat signals.
Claim 17
Dependent Claim
25 words
An apparatus according to claim 10, wherein one diffraction grating is formed on a mask, and said other diffraction grating is formed on a wafer.
Claim 18
Dependent Claim
22 words
An apparatus according to claim 10, wherein the two diffraction gratings are formed on a substrate by processes different from each other.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1998-11-06 | 1999-05-08 | 1999-11-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-11-06 | 2003-05-08 | 2003-11-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-11-06 | 2007-05-08 | 2007-11-07 | $7700.00 | Window Closed / Lapsed |