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US5595844A
Expired / Lapsed
US
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Method of exposing light in a method of fabricating a reticle
Assignee: Toshiba Corp
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Filing: 1995-05-30
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Granted: 1997-01-21
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Expires: 2015-05-30
Abstract
Abstract In a reticle, a semi-transparent film pattern in place of a light blocking film pattern is used as a mask pattern having a size within a certain range, whereby an exposure system can be improved in resolution limit and faithful pattern transfer can be realized with a constant light quantity. A reticle may be of a stacked layer structure which comprises a shift film for providing a different optical path to exposure light, a mask substrate formed on the top or bottom of the shift film, and a transmissivity ratio adjustment layer having a predetermined transmissivity ratio to the exposure light. The material of a phase shifter may be adjusted in amplitude transmissivity ratio so that a shifter width for effectively improving a contrast can be made large and an accuracy necessary for a shifter width can be loosened. The mask pattern may include a semi-transparent film pattern which is made of silicon, a silicon compound, a mixture containing silicon, germanium, a germanium compound or a mixture containing germanium to provide a different optical path from that of the transparent part with respect to lithographic light. A silicon compound, a mixture containing silicon, germanium, a germanium compound or a mixture containing germanium is controlled in its composition ratio to form a semi-transparent film pattern on a transparent substrate.
Inventors
- 👤 Yoko Tomofuji
- 👤 Makoto Nakase
- 👤 Takashi Sato
- 👤 Hiroaki Hazama
- 👤 Haruki Komano
- 👤 Shinichi Ito
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 23:14
CPC Classifications
G; G03; G03F; G03F1/00; G03F1/26; G03F1/32; G03F1/29; G03F1/36
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
231 words
A method of exposing light comprising the steps of: forming a mask pattern made of a mask film pattern formed on a light-transmissible substrate, the mask pattern being a semi-transparent film which causes a length of an optical path for a light beam passing therethrough to be different from a length of an optical path for a light beam passing through the substrate by a predetermined amount, the step of forming a mask pattern comprising the steps of: determining ranges of refractive index n and extinction coefficient k of the semi-transparent film within which an amplitude transmissivity ratio T and a phase difference φ between the semi-transparent film and air that has the same thickness of the semi-transparent film fall within ranges necessary to obtain desired resolution and depth of focus, obtaining relationship in the form of a curved line between the refractive index n and the extinction coefficient k by changing conditions for formation of the mask pattern, selecting values of the refractive index and the extinction coefficient k from the ranges thus determined, and determining the conditions for formation of the mask pattern such that the refractive index n and the extinction coefficient k become the selected values, and forming a mask film pattern based on the conditions for formation of the mask pattern; and irradiating an exposure beam onto a resist through a reticle using the mask pattern.
Claim 2
Independent Claim
231 words
A method of exposing light comprising the steps of: forming a mask pattern made of a mask film pattern formed on a light-transmissible substrate, the mask pattern being a semi-transparent film which causes a length of an optical path for a light beam passing therethrough to be different from a length of an optical path for a light beam passing through the substrate by a predetermined amount, the step of forming a mask pattern comprising the steps of: determining ranges of refractive index n and extinction coefficient k of the semi-transparent film within which an amplitude transmissivity ratio T and a phase difference φ between the semi-transparent film and air that has the same thickness of the semi-transparent film fall within ranges necessary to obtain desired resolution and depth of focus, obtaining relationship in the form of a curved line between the refractive index n and the extinction coefficient k by changing conditions for formation of the mask pattern, selecting values of the refractive index and the extinction coefficient k from the ranges thus determined, and determining the conditions for formation of the mask pattern such that the refractive index n and the extinction coefficient k become the selected values, and forming a mask film pattern based on the conditions for formation of the mask pattern; and irradiating an exposure beam onto a resist through a reticle using the mask pattern.
Claim 3
Dependent Claim
79 words
A method of exposing light as set forth in claim 1, wherein the step of forming the mask film pattern comprises the step of forming a silicon nitride or silicon oxide film having desired values of amplitude transmissivity ratio and phase difference by mixing a predetermined quantity of nitrogen or oxygen gas in a sputtering atmosphere using silicon as a target and controlling a nitrogen or oxygen composition ratio based on the conditions for formation of the mask pattern.
Claim 4
Dependent Claim
18 words
A method of exposing light as set forth in claim 2, wherein said phase difference is substantially π.
Claim 5
Dependent Claim
65 words
A method of exposing light as set forth in claim 1, wherein said exposure beam is a g ray and the step of forming the mask film pattern comprises the step of forming a mask pattern made of amorphous silicon based on the conditions for formation of the mask pattern, thereby forming a mask pattern having desired values of amplitude transmissivity ratio and phase difference.
Claim 6
Dependent Claim
18 words
A method of exposing light as set forth in claim 4, wherein, said phase difference is substantially π.
Claim 7
Dependent Claim
79 words
A method of exposing light as set forth in claim 4, wherein the step of forming the mask film pattern comprises the step of forming a silicon nitride or silicon oxide film having desired values of amplitude transmissivity ratio and phase difference by mixing a predetermined quantity of nitrogen or oxygen gas in a sputtering atmosphere using silicon as a target and controlling a nitrogen or oxygen composition ratio based on the conditions for formation of the mask pattern.
Claim 8
Dependent Claim
19 words
A method of exposing light as set forth in claim 1, wherein said exposure beam is an i ray.
Claim 9
Dependent Claim
19 words
A method of exposing light as set forth in claim 1, wherein said exposure beam is an g ray.
Claim 10
Dependent Claim
83 words
A method of exposing light as set forth in claim 1, wherein the step of forming the mask film pattern comprises the step of depositing a silicon dioxide film while adjusting the quantity of oxygen in a raw material gas by using a CVD technique based on the conditions for formation of the mask pattern so as to control an oxygen composition ratio in the silicon dioxide film, thereby forming a mask pattern having desired values of amplitude transmissivity ratio and phase difference.
Claim 11
Dependent Claim
79 words
A method of exposing light as set forth in claim 1, wherein the step of forming the mask film pattern comprises the step of depositing a silicon nitride film while adjusting the quantity of ammonium in a raw material gas by a CVD technique based on the conditions for formation of the mask pattern so as to control a nitrogen composition ratio, thereby forming a mask pattern having desired values of the amplitude transmissivity ratio and the phase difference.
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) | 2000-01-21 | 2000-07-22 | 2001-01-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-01-21 | 2004-07-22 | 2005-01-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-01-21 | 2008-07-22 | 2009-01-21 | $7700.00 | Window Closed / Lapsed |