US4890309A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Lithography mask with a π-phase shifting attenuator
Assignee: Massachusetts Institute of Technology
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Filing: 1987-02-25
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Granted: 1989-12-26
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Expires: 2007-02-25
Abstract
Abstract The mask includes an attenuator which passes a fraction of the incident electromagnetic radiation and phase shifts the radiation relative to the radiation passing through open features of the mask by approximately an odd multiple of π radians. This phase shifting of light passing through the attenuator by π radians reduces the edge blurring that results from diffraction effects. The present invention steepens the slope of the intensity profile at the edges of features in x-ray lithographic replication relative to the slope obtained with a conventional x-ray mask. The steeper slope is a highly significant advantage because it permits improved linewidth control.
Inventors
- 👤 Henry I. Smith
- 👤 Erik H. Anderson
- 👤 Mark L. Schattenburg
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 15:59
CPC Classifications
G; G03; G03F; G03F1/00; G03F1/22; G03F1/26; G03F1/32; G03F7/00; G03F7/70; G03F7/70216; G03F7/70283
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
55 words
Lithography mask including open features and an attenuator whose material and thickness are selected to both pass a fraction of incident electromagnetic radiation and to phase shift the radiation relative to radiation passing through the open features of the mask by approximately an odd multiple of π radians in order to reduce deleterious diffraction effects.
Claim 2
Dependent Claim
55 words
Lithography mask including open features and an attenuator whose material and thickness are selected to both pass a fraction of incident electromagnetic radiation and to phase shift the radiation relative to radiation passing through the open features of the mask by approximately an odd multiple of π radians in order to reduce deleterious diffraction effects.
Claim 3
Dependent Claim
12 words
The lithography mask of claim 1 wherein the electromagnetic radiation is x-rays.
Claim 4
Dependent Claim
13 words
The lithography mask of claim 2 wherein the attenuator is an x-ray absorber.
Claim 5
Dependent Claim
19 words
The lithography mask of claim 2 wherein the attenuator is a multilayer film resulting in attenuation through back reflection.
Claim 6
Dependent Claim
11 words
The lithography mask of claim 3 wherein the absorber is homogeneous.
Claim 7
Dependent Claim
11 words
The lithography mask of claim 5 wherein the attenutator is tungsten.
Claim 8
Dependent Claim
11 words
The lithography mask of claim 5 wherein the attenuator is gold.
Claim 9
Dependent Claim
15 words
The lithography mask of claim 3 wherein the attenuator comprises alloys or gold and silver.
Claim 10
Dependent Claim
16 words
The lithography mask of claim 3 wherein the attenuator comprises alternating layers of gold and silver.
Claim 11
Dependent Claim
15 words
The lithography mask of claim 3 wherein the attenuator comprises alloys of copper and gold.
Claim 12
Dependent Claim
16 words
The lithography mask of claim 3 wherein the attenuator comprises alternating layers of copper and gold.
Claim 13
Dependent Claim
25 words
The lithography masks of claim 4 wherein the multilayer film comprises alternating layers of a high atomic number material and a low atomic number material.
Claim 14
Dependent Claim
22 words
The lithography mask of claim 12 wherein the high atomic number material is tungsten and the low atomic number material is carbon.
Claim 15
Dependent Claim
55 words
X-ray lithography mask including open features and an attenuator whose material and thickness are selected to both pass a fraction of the incident x-rays and to phase shift the x-rays relative to those passing through open features of the mask by approximately an odd multiple of π radians in order to reduce deleterious diffraction effects.
Claim 16
Dependent Claim
55 words
X-ray lithography mask including open features and an attenuator whose material and thickness are selected to both pass a fraction of the incident x-rays and to phase shift the x-rays relative to those passing through open features of the mask by approximately an odd multiple of π radians in order to reduce deleterious diffraction effects.
Claim 17
Dependent Claim
14 words
The x-ray lithography mask of claim 14 wherein he attenuator is an x-ray absorber.
Claim 18
Dependent Claim
22 words
The x-ray lithography mask of claim 14 wherein the attenuator is a multilayer film adapted to attenuate x radiation by back reflection.
Claim 19
Dependent Claim
16 words
The lithography mask of claim 2 wherein the attenuator transmits approximately 10% of the incident radiation.
Claim 20
Dependent Claim
86 words
Mask for optical and ultra-violet radiation comprising a transparent substrate and an attenuator pattern on the substrate, in which, in order to reduce deleterious diffraction effects, the material and thickness of the attenuator pattern are selected to pass a fraction of the incident radiation, and the open features of the transparent substrate include a relief portion adjusting the phase of the non-attenuated portion of the radiation such that the relative phase shift between the attenuated and non-attentuated radiation is approximately an odd multiple of π radians.
Claim 21
Dependent Claim
86 words
Mask for optical and ultra-violet radiation comprising a transparent substrate and an attenuator pattern on the substrate, in which, in order to reduce deleterious diffraction effects, the material and thickness of the attenuator pattern are selected to pass a fraction of the incident radiation, and the open features of the transparent substrate include a relief portion adjusting the phase of the non-attenuated portion of the radiation such that the relative phase shift between the attenuated and non-attentuated radiation is approximately an odd multiple of π radians.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-12-25 | 1993-06-26 | 1993-12-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-12-25 | 1997-06-26 | 1997-12-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-12-25 | 2001-06-26 | 2001-12-26 | $7700.00 | Window Closed / Lapsed |