US4636078A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Microscopic detection of membrane surface defects through interference patterns
Assignee: MICROMANIPULATOR MICROSCOPE COMPANY Inc
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Filing: 1983-10-04
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Granted: 1987-01-13
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Expires: 2003-10-04
Abstract
Abstract Transparent membranes are examined with a microscope having coaxial brightfield illumination fitted with a narrow bandwidth filter to convert polychromatic light from a source to substantially monochromatic light. Light reflecting off of the surfaces of the membrane recombine to create an interference pattern, including observable fringes in the region of membrane surface aberrations. Membranes which may be examined include pellicles used to cover photomasks and photo-resist layers. If a photo-resist layer is examined, a filter is selected to provide essentially monochromatic light at a wavelength to which the resist is insensitive.
Inventors
- 👤 T. Charles Podvin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 16:34
CPC Classifications
G; G03; G03F; G03F7/00; G03F7/70; G03F7/70483; G01; G01N; G01N21/00; G01N21/84; G01N21/88
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
247 words
An apparatus for inspecting a substantially transarent membrane by reflection when said transparent membrane is backed by an opaque surface, said apparatus comprising: said transparent membrane having a pair of flat surfaces with a thickness between said pair of flat surfaces of between about 0.5 and about 2.5 microns, said transparent membrane transimtting at least about 50% of incident light at a particular wavelength, and each of said pair of flat surfaces reflecting between about 0.5% and about 5% of the incident light; a polychromatic light source; a microscope having an eyepiece and an objective means and defining a light path from said light source through the objective means to said transparent membrane, and back from said transparent membrane, through said objective means, and to the eyepiece; a filter removably disposed in said light path having a peak transmittance at a particular wavelength with a bandwidth of about 40 nanometers or less; one of said pair of flat surfaces forming a reference surface and the other one of said pair of flat surfaces forming a measurement surface such that light reflecting off said reference surface and reflecting off said measurement surface to said eyepiece combine to create an observable interference pattern permitting inspection of said transparent membrane for defects, said defects appearing as fringe patterns in regions of change in optical path length; and said microscope being useful for normal observations of said opaque surface with polychromatic light when said filter is removed from the light path.
Claim 2
Independent Claim
247 words
An apparatus for inspecting a substantially transarent membrane by reflection when said transparent membrane is backed by an opaque surface, said apparatus comprising: said transparent membrane having a pair of flat surfaces with a thickness between said pair of flat surfaces of between about 0.5 and about 2.5 microns, said transparent membrane transimtting at least about 50% of incident light at a particular wavelength, and each of said pair of flat surfaces reflecting between about 0.5% and about 5% of the incident light; a polychromatic light source; a microscope having an eyepiece and an objective means and defining a light path from said light source through the objective means to said transparent membrane, and back from said transparent membrane, through said objective means, and to the eyepiece; a filter removably disposed in said light path having a peak transmittance at a particular wavelength with a bandwidth of about 40 nanometers or less; one of said pair of flat surfaces forming a reference surface and the other one of said pair of flat surfaces forming a measurement surface such that light reflecting off said reference surface and reflecting off said measurement surface to said eyepiece combine to create an observable interference pattern permitting inspection of said transparent membrane for defects, said defects appearing as fringe patterns in regions of change in optical path length; and said microscope being useful for normal observations of said opaque surface with polychromatic light when said filter is removed from the light path.
Claim 3
Dependent Claim
19 words
A combination in accordance with claim 1 wherein said filter has a bandwidth of about 20 nanometers or less.
Claim 4
Dependent Claim
39 words
A combination in accordance with claim 1 wherein said particular wavelength is about 500 nanometers or longer, and said membrane is a photo-resist having sensitivity to light of shorter wavelength and essential insensitivity to light at the particular wavelength.
Claim 5
Dependent Claim
21 words
A combination in accordance with claim 1 wherein said membreane has a thickness of between about 1 and about 5 microns.
Claim 6
Dependent Claim
21 words
A combination in accordance with claim 1 wherein said microscope provides magnification in the range of between 10 and about 100.
Claim 7
Dependent Claim
22 words
A combination in accordance with claim 1 wherein said microscope provides magnification in the range of between about 10 and about 50.
Claim 8
Dependent Claim
26 words
A combination in accordance with claim 1 including a long-working distance objective in said microscope providing a high magnification, said narrow bandwidth filter eliminating chromatic aberrations.
Claim 9
Dependent Claim
17 words
A combination in accordance with claim 7, said filter being disposed between said objective and the membrane.
Claim 10
Dependent Claim
18 words
A combination in accordance with claim 1, said filter being disposed between said light source and said microscope.
Claim 11
Dependent Claim
14 words
A combination in accordance with claim 1, wherein said membrane is a photo-resist layer.
Claim 12
Dependent Claim
24 words
A combination in accordance with claim 1, wherein said membrane is selected from the group consisting of a nitrocellulose membrane and a PEHB membrane.
Claim 13
Dependent Claim
56 words
A combination in accordance with claim 1 wherein said filter is disposed in the portion of said light path between said membrane and said eyepiece and tilted at an angle relative to the plane perpendicular to said portion of the light path, whereby reflections from the surfaces of said filter are diverted away from said eyepiece.
Claim 14
Independent Claim
189 words
A method of examining a substantially transparent membrane when backed by an opaque surface, said transparent membrane having a pair of substantially parallel surfaces and a thickness of between about 0.5 and about 25 microns, one of said pair of parallel surfaces forming a reference surface and the other of said pair of parallel surfaces forming a measurement surface, the method comprising: providing a microscope having an eyepiece, an objective means, and a polychromatic light source positioned to shine light along a light path from said source, through said objective means, through the transparent membrane, onto the opaque surface and then back to said objective means and to the eyepiece; disposing within said light path a filter having a peak transmittance at a particular wavelength with a bandwidth of about 40 nanometers or less; placing said transparent membrane in front of said objective means, and examining said transparent membrane through said eyepiece and noting interference patterns created by light reflecting off of said reference surface and said measurement surface toward said objective means, wherein fringe patterns of the interference patterns are indicative of surface aberrations in said transparent membrane.
Claim 15
Independent Claim
189 words
A method of examining a substantially transparent membrane when backed by an opaque surface, said transparent membrane having a pair of substantially parallel surfaces and a thickness of between about 0.5 and about 25 microns, one of said pair of parallel surfaces forming a reference surface and the other of said pair of parallel surfaces forming a measurement surface, the method comprising: providing a microscope having an eyepiece, an objective means, and a polychromatic light source positioned to shine light along a light path from said source, through said objective means, through the transparent membrane, onto the opaque surface and then back to said objective means and to the eyepiece; disposing within said light path a filter having a peak transmittance at a particular wavelength with a bandwidth of about 40 nanometers or less; placing said transparent membrane in front of said objective means, and examining said transparent membrane through said eyepiece and noting interference patterns created by light reflecting off of said reference surface and said measurement surface toward said objective means, wherein fringe patterns of the interference patterns are indicative of surface aberrations in said transparent membrane.
Claim 16
Dependent Claim
18 words
A method according to claim 13, said microscope providing a magnification of between about 10 and about 100.
Claim 17
Dependent Claim
18 words
A method according to claim 13 wherein said filter has a bandwidth of about 20 nanometers or less.
Claim 18
Dependent Claim
21 words
A method according to claim 13 wherein said filter transmits at least about 25% of the light at said peak wavelength.
Claim 19
Dependent Claim
22 words
A method according to claim 13 wherein said membrane transmits at least about 50% of the incident light at said peak wavelength.
Claim 20
Dependent Claim
35 words
A method according to claim 13 wherein said peak wavelength is about 500 nanometers or longer, and said membrane is a photo-resist sensitive to blue light and substantially insensitive to light transmitted through said filter.
Claim 21
Dependent Claim
18 words
A method according to claim 13 wherein said membrane is between about 0.5 and about 25 microns thick.
Claim 22
Dependent Claim
25 words
A method according to claim 13 wherein said surfaces of said membrane each reflect between about 0.5 and about 5 percent of the incident light.
Claim 23
Dependent Claim
36 words
A method in accordance to claim 15, disposing said filter in the portion of said light path between said membrane and said eyepiece at an angle relative to the plane perpendicular to said light path portion.
Claim 24
Independent Claim
257 words
A method of examining an object including an opaque surface and a transparent membrane by alternately examining the opaque surface and the transparent membrane for defects, the transparent membrane having a pair of substantially parallel surfaces and a thickness of between about 0.5 and about 25 microns, one of said pair of parallel surfaces forming a reference surface and the other of said pair of parallel surfaces forming a measurement surface, the method comprising: providing a microscope having an eyepiece, an objective means, and a polychromatic light source positioned to shine light along a light path from polychromatic light source, through said objective means, and to the object, and to receive light back from the object, through said objective, and to said eyepiece; disposing said object in front of said objective means perpendicular to said light path such that light passes through said transparent membrane before impinging on said opaque surface; examining said opaque surface by observing through said eyepiece the image produced by the reflection of polychromatic light from said opaque surface; alternately examining said transparent membrane by disposing within said light path between said polychromatic light source and said transparent membrane a filter having a peak transmittance at a particular wavelength with a bandwidth of about 40 nanometers or less, and by observing said transparent membrane through said eyepiece; and noting interference patterns created by light reflecting toward said objective means off of said reference surface and measurement surface, wherein fringe patterns in said interference patterns are indicative of surface aberrations in said transparent membrane.
Claim 25
Independent Claim
257 words
A method of examining an object including an opaque surface and a transparent membrane by alternately examining the opaque surface and the transparent membrane for defects, the transparent membrane having a pair of substantially parallel surfaces and a thickness of between about 0.5 and about 25 microns, one of said pair of parallel surfaces forming a reference surface and the other of said pair of parallel surfaces forming a measurement surface, the method comprising: providing a microscope having an eyepiece, an objective means, and a polychromatic light source positioned to shine light along a light path from polychromatic light source, through said objective means, and to the object, and to receive light back from the object, through said objective, and to said eyepiece; disposing said object in front of said objective means perpendicular to said light path such that light passes through said transparent membrane before impinging on said opaque surface; examining said opaque surface by observing through said eyepiece the image produced by the reflection of polychromatic light from said opaque surface; alternately examining said transparent membrane by disposing within said light path between said polychromatic light source and said transparent membrane a filter having a peak transmittance at a particular wavelength with a bandwidth of about 40 nanometers or less, and by observing said transparent membrane through said eyepiece; and noting interference patterns created by light reflecting toward said objective means off of said reference surface and measurement surface, wherein fringe patterns in said interference patterns are indicative of surface aberrations in said transparent membrane.
References Cited (Backward Citations)
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) | 1990-01-12 | 1990-07-14 | 1991-01-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-01-12 | 1994-07-14 | 1995-01-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-01-12 | 1998-07-14 | 1999-01-13 | $7700.00 | Window Closed / Lapsed |