US4891094A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of optimizing photoresist contrast
Assignee: Motorola Solutions Inc
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Filing: 1989-05-25
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Granted: 1990-01-02
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Expires: 2009-05-25
Abstract
Abstract The contrast of a photoresist layer used in a lithographic process for a given light source is optimized by determining the nonlinear relationship of the photoresist contrast with regard to the thickness thereof and then placing over a substrate a thickness of photoresist corresponding to a desired value of contrast indicated by the nonlinear relationship of contrast with photoresist thickness. The nonlinear contrast with regard to photoresist thickness function is a damped, sinusoidal like function with the difference between maxima and minima contrast values decreasing as the photoresist thickness increases and with higher absolute maxima values for contrast as photoresist thickness decreases. The amount of light needed to fully expose a given thickness of photoresist also varies with the photoresist thickness in a sinusoidal like manner and a phase difference may exist between the sinusoidal like contrast versus photoresist thickness function and the sinusoidal like exposing light versus photoresist thickness function. It is possible that the light source and the photoresist characteristics can be selected to product a predetermined phase difference.
Inventors
- 👤 Whitson G. Waldo, III
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 07:34
CPC Classifications
H; H10; H10P; H10P76/00; H10P76/20; H10P76/204; H10P76/2041; G; G03; G03F; G03F7/00; G03F7/70; G03F7/70483; G03F7/7055; G03F7/70583; G03F7/20
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
59 words
Optimizing the contrast of a photoresist layer used in the manufacture of integrated circuits by a lithographic process including: determining the nonlinear relationship of said photoresist contrast with regard to the thickness thereof, and placing over a substrate a thickness of photoresist corresponding to a desired value of contrast indicated by said nonlinear relationship of contrast with photoresist thickness.
Claim 2
Dependent Claim
59 words
Optimizing the contrast of a photoresist layer used in the manufacture of integrated circuits by a lithographic process including: determining the nonlinear relationship of said photoresist contrast with regard to the thickness thereof, and placing over a substrate a thickness of photoresist corresponding to a desired value of contrast indicated by said nonlinear relationship of contrast with photoresist thickness.
Claim 3
Dependent Claim
80 words
Optimizing the contrast of a photoresist layer used in the manufacture of integrated circuits by exposing a portion of a layer of photoresist over a substrate to a source of light with at least a portion of said light reflected by said substrate back through said photoresist, and selecting a thickness for said photoresist layer prior to said step of exposing that causes a substantial maxima of destructive standing wave interference between said exposing light and said reflected portion thereof.
Claim 4
Dependent Claim
80 words
Optimizing the contrast of a photoresist layer used in the manufacture of integrated circuits by exposing a portion of a layer of photoresist over a substrate to a source of light with at least a portion of said light reflected by said substrate back through said photoresist, and selecting a thickness for said photoresist layer prior to said step of exposing that causes a substantial maxima of destructive standing wave interference between said exposing light and said reflected portion thereof.
Claim 5
Dependent Claim
13 words
The method according to claim 2 wherein said light source is substantially monochromatic.
Claim 6
Dependent Claim
74 words
Optimizing the contrast of a photoresist layer used in the manufacture of integrated circuits by determining the nonlinear relationship of the photoresist contrast to the thickness thereof for a given light source, laying a thickness of photoresist corresponding to a desired value of contrast shown by said nonlinear relationship of contrast and photoresist thickness over a substrate, and exposing at least a portion of the surface of said photoresist layer to said light source.
Claim 7
Dependent Claim
74 words
Optimizing the contrast of a photoresist layer used in the manufacture of integrated circuits by determining the nonlinear relationship of the photoresist contrast to the thickness thereof for a given light source, laying a thickness of photoresist corresponding to a desired value of contrast shown by said nonlinear relationship of contrast and photoresist thickness over a substrate, and exposing at least a portion of the surface of said photoresist layer to said light source.
Claim 8
Dependent Claim
12 words
The method of claim 4 wherein said light source is approximately monochromatic.
Claim 9
Dependent Claim
22 words
The method according to claim 4 wherein a portion of said exposing light is reflected by said substrate back through said photoresist.
Claim 10
Dependent Claim
22 words
The method according to claim 6 wherein said reflected light and said exposing light result in standing wave interference within said photoresist.
Claim 11
Dependent Claim
25 words
The method according to claim 4 wherein said portion of said photoresist layer exposed to said light source receives a predetermined amount of light energy.
Claim 12
Dependent Claim
21 words
The method according to claim 4 wherein said nonlinear contrast with regard to photoresist thickness function is a sinusoidal like function.
Claim 13
Dependent Claim
33 words
The method according to claim 9 where said sinusoidal like contrast versus photoresist thickness function is damped such that the difference between maxima and minima contrast values decrease as the photoresist thickness increases.
Claim 14
Dependent Claim
25 words
The method according to claim 9 wherein said sinusoidal like contrast versus photoresist thickness function includes higher maxima values for contrast as photoresist thickness decreases.
Claim 15
Dependent Claim
30 words
The method according to claim 9 where the amount of light needed to fully expose a given thickness of photoresist varies with the photoresist thickness in a sinusoidal like manner.
Claim 16
Dependent Claim
40 words
The method according to claim 12 wherein said light source characteristics and said photoresist characteristics cause a phase difference to exist between said sinusoidal like contrast versus photoresist thickness function and said sinusoidal like exposing light versus photoresist thickness function.
Claim 17
Dependent Claim
19 words
The method according to claim 13 wherein said light source and said photoresist produce a predetermined said phase difference.
References Cited (Backward Citations)
US4462860A
Cited
US4575399A
Cited
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) | 1993-01-01 | 1993-07-03 | 1994-01-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-01-01 | 1997-07-03 | 1998-01-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-01-01 | 2001-07-03 | 2002-01-02 | $7700.00 | Window Closed / Lapsed |