US4881257A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Deformation free X-ray exposure mask for X-ray lithography
Assignee: Fujitsu Ltd
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Filing: 1987-10-23
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Granted: 1989-11-14
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Expires: 2007-10-23
Abstract
Abstract An X-ray exposure mask for use in a stepper in X-ray lithography is formed so that deformation of mask patterns on a surface of the X-ray mask is prevented, so that when these patterns are transferred to a semiconductor wafer substantially no deformation of the patterns will occur, allowing higher integration of patterns. The surface of the X-ray mask is divided into a centrally located first region and a surrounding second region. A layer of X-ray absorbing material is superposed on the surface of the X-ray mask and includes a first layer portion coextensive with the first central region and patterned for selectively exposing the first central region of the membrane surface in a corresponding pattern for selected transmission of an X-ray beam therethrough. A second layer portion of the layer of X-ray absorbing material, coextensive with the second, surrounding region of the membrane, is patterned for selectively exposing the second, surrounding region to reduce the density of the X-ray absorbing material on that second, surrounding region. Preferably, the respective densities of the first and second layer portions of the X-ray absorbing material are substantially the same, although a difference of up to 30% therebetween will yield satisfactory results.
Inventors
- 👤 Kenji Nakagawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 05:12
CPC Classifications
G; G03; G03F; G03F1/00; G03F1/22
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
155 words
An X-ray exposure mask used for patterning a resist layer of a semiconductor wafer using an X-ray beam, said mask comprising: a membrane, translucent to the X-ray beam, having a planar surface including a centrally located X-ray mask region on the surface and a non-mask region surrounding said X-ray mask region; and a layer of X-ray absorbing material superposed on said planar surface of said membrane and comprising a first layer portion coextensive with said X-ray mask region and patterned for selectively exposing the X-ray mask region of the membrane surface in a corresponding pattern for selective transmission of an X-ray beam therethrough, and said layer of X-ray absorbing material further comprising a second layer portion coextensive with said non-mask region and patterned for reducing a pattern density of the X-ray absorbing material superposed on the non-mask region and balancing stress in said layer of X-ray absorbing material in the first and second layer portions.
Claim 2
Dependent Claim
155 words
An X-ray exposure mask used for patterning a resist layer of a semiconductor wafer using an X-ray beam, said mask comprising: a membrane, translucent to the X-ray beam, having a planar surface including a centrally located X-ray mask region on the surface and a non-mask region surrounding said X-ray mask region; and a layer of X-ray absorbing material superposed on said planar surface of said membrane and comprising a first layer portion coextensive with said X-ray mask region and patterned for selectively exposing the X-ray mask region of the membrane surface in a corresponding pattern for selective transmission of an X-ray beam therethrough, and said layer of X-ray absorbing material further comprising a second layer portion coextensive with said non-mask region and patterned for reducing a pattern density of the X-ray absorbing material superposed on the non-mask region and balancing stress in said layer of X-ray absorbing material in the first and second layer portions.
Claim 3
Dependent Claim
31 words
An X-ray exposure mask according to claim 1, wherein the respective pattern densities of the X-ray absorbing material of said first and second layer portions differ by no more than 30%.
Claim 4
Dependent Claim
28 words
An X-ray exposure mask according to claim 2, wherein the respective pattern densities of the X-ray absorbing material of said first and second layer portions are approximately equal.
Claim 5
Dependent Claim
19 words
An X-ray exposure mask according to claim 1, wherein said second layer portion is patterned in a checkerboard pattern.
Claim 6
Dependent Claim
37 words
An X-ray exposure mask according to claim 4, wherein said checkerboard pattern of said second layer portion comprises plural, substantially square areas of the X-ray absorbing material, individually separated from each other and in parallel, aligned relationship.
Claim 7
Dependent Claim
48 words
An X-ray exposure mask according to claim 4, wherein said checkerboard pattern of said second layer portion comprises plural, substantially square areas through each of which a corresponding portion of the non-mask region is exposed, said areas being individually separated from each other and in an aligned relationship.
Claim 8
Dependent Claim
170 words
An X-ray exposure mask for patterning a resist layer of a semiconductor wafer during X-ray lithography, said X-ray exposure mask comprising: a ring-shaped base; a silicon supporting ring mounted on said base; a substantially flat inorganic membrane, translucent to X-rays, formed on said silicon supporting ring and having a substantially planar surface including a centrally located mask region and a non-mask region surrounding said mask region; and a layer of X-ray absorbing material superposed on said planar surface of said membrane and comprising a first layer portion coextensive with said mask region and patterned for selectively exposing the mask region of the membrane surface in a corresponding pattern for selective transmission of an X-ray beam therethrough, and said layer of x-ray absorbing material further comprising a second layer portion coextensive with said surrounding non-mask region and patterned for reducing a pattern density of the X-ray absorbing material superposed on the surrounding non-mask region and balancing stress in said layer of X-ray absorbing material between the first and second layer portions.
Claim 9
Dependent Claim
170 words
An X-ray exposure mask for patterning a resist layer of a semiconductor wafer during X-ray lithography, said X-ray exposure mask comprising: a ring-shaped base; a silicon supporting ring mounted on said base; a substantially flat inorganic membrane, translucent to X-rays, formed on said silicon supporting ring and having a substantially planar surface including a centrally located mask region and a non-mask region surrounding said mask region; and a layer of X-ray absorbing material superposed on said planar surface of said membrane and comprising a first layer portion coextensive with said mask region and patterned for selectively exposing the mask region of the membrane surface in a corresponding pattern for selective transmission of an X-ray beam therethrough, and said layer of x-ray absorbing material further comprising a second layer portion coextensive with said surrounding non-mask region and patterned for reducing a pattern density of the X-ray absorbing material superposed on the surrounding non-mask region and balancing stress in said layer of X-ray absorbing material between the first and second layer portions.
Claim 10
Dependent Claim
45 words
An X-ray exposure mask according to claim 7, wherein said second layer portion includes a solid band of X-ray absorbing material formed on an area of said non-mask region bordering said mask region and a checkerboard pattern over the remaining area of said non-mask region.
Claim 11
Dependent Claim
31 words
An X-ray exposure mask according to claim 8, wherein the respective pattern densities of the X-ray absorbing material of said first and second layer portions differ by no more than 30%.
Claim 12
Dependent Claim
28 words
An X-ray exposure mask according to claim 9, wherein the respective pattern densities of the X-ray absorbing material of said first and second layer portions are approximately equal.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-11-13 | 1993-05-15 | 1993-11-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-11-13 | 1997-05-15 | 1997-11-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-11-13 | 2001-05-15 | 2001-11-14 | $7700.00 | Window Closed / Lapsed |