Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2001-05-03
2003-08-12
Rosasco, S. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S296000
Reexamination Certificate
active
06605394
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
In general, the present invention relates to a method of producing a lithographic mask (reticle) for use in the semiconductor industry. In particular, the invention pertains to the use of a deep ultraviolet (DUV) photoresist in combination with at least one antireflective coating (ARC) to produce a high performance mask. The invention also relates to use of an optical direct write continuous laser mask writing tool in combination with a chemically amplified DUV photoresist and an organic ARC.
2. Brief Description of the Background Art
Photoresist compositions are used in microlithographic processes for making miniaturized electronic components, such as in the fabrication of semiconductor device structures. The miniaturized electronic device structure patterns are typically created by transferring a pattern from a patterned masking layer overlying the semiconductor substrate rather than by direct write on the semiconductor substrate, because of the time economy which can be achieved by blanket processing through a patterned masking layer. With regard to semiconductor device processing, the patterned masking layer may be a patterned photoresist layer or may be a patterned “hard” masking layer (typically an inorganic material or a high temperature organic material) which resides on the surface of the semiconductor device structure to be patterned. The patterned masking layer is typically created using another mask which is frequently referred to as a photomask or reticle. A reticle is typically a thin layer of a metal-containing layer (such as a chrome-containing, molybdenum-containing, or tungsten-containing material, for example) deposited on a glass or quartz plate. The reticle is patterned to contain a “hard copy” of the individual device structure pattern to be recreated on the masking layer overlying a semiconductor structure.
A reticle may be created by a number of different techniques, depending on the method of writing the pattern on the reticle. Due to the dimensional requirements of today's semiconductor structures, the writing method is generally with a laser or e-beam. A typical process for forming a reticle may include: providing a glass or quartz plate, depositing a chrome-containing layer on the glass or quartz surface, depositing an antireflective coating (ARC) over the chrome-containing layer, applying a photoresist layer over the ARC layer, direct writing on the photoresist layer to form a desired pattern, developing the pattern in the photoresist layer, etching the pattern into the chrome layer, and removing the residual photoresist layer. When the area of the photoresist layer contacted by the writing radiation becomes easier to remove during development, the photoresist is referred to as a positive-working photoresist. When the area of the photoresist layer contacted by the writing radiation becomes more difficult to remove during development, the photoresist is referred to as a negative-working photoresist. Advanced reticle manufacturing materials frequently include combinations of layers of materials selected from chromium, chromium oxide, chromium oxynitride, molybdenum, molybdenum silicide, and molybdenum tungsten silicide, for example.
As previously mentioned, the reticle or photomask is used to transfer a pattern to an underlying photoresist, where the reticle is exposed to blanket radiation which passes through open areas of the reticle onto the surface of the photoresist. The photoresist is then developed and used to transfer the pattern to an underlying semiconductor structure. Due to present day pattern dimensional requirements, which are commonly less than 0.3 &mgr;m, the photoresist is preferably a chemically amplified DUV photoresist. In the making of the reticle itself, a chemically amplified DUV photoresist has been used in combination with a direct write electron beam writing tool. However, the exposed, imaged photoresist on the surface of the unpatterned reticle frequently exhibits a “foot” at the bottom of the pattern profile, where the photoresist layer interfaces with an underlying ARC layer on a chrome-containing surface, for example, despite the presence of the underlying ARC layer (which is typically a chrome oxynitride material). The foot is not uniform in size across the reticle substrate surface because the basisity changes somewhat randomly across the substrate surface. Since the foot is variable, it makes it difficult to do the metrology which is used to determine whether the finished reticle will meet dimensional requirements. Some imaged and developed positive tone photoresists exhibit a “t”-top profile. In addition, the surface of the patterned photoresist layer typically exhibits standing waves, due to reflections which occur during the direct writing on the photoresist layer, despite the presence of the underlying ARC layer.
In their 1992 paper in Microelectronic Engineering (Vol. 17 (1992) 275-278), Gilles Amblard et al. describe how the development of chemically amplified (CA) resist systems has been the most successfil approach to meeting the challenge of high resolution and high speed, posed by X-Ray, Electron-Beam or Deep UV lithography. However, they discovered that pattern profile abnormalities appear which limit the use of a negative resist. Even though the correct exposure dose is applied throughout the thickness of the desired pattern, an aqueous developer dissolves the bottom part of the resist in contact with or near the underlying substrate. Fissures as thick as 0.1 to 0.2 &mgr;m were observed in the pattern at the interface with the substrate, resulting in a loss of adhesion in fine patterns. The problem was observed for resists imaged and developed on both spin on glass (SOG) and aluminum substrates. With regard to the aluminum, they observed that because of the amphoteric behavior of aluminum, the acid molecules of the photoresist react when they come in contact with the substrate, thus generating a concentration gradient within the resist material. Because of the lack of acid molecules near the resist/aluminum interface, crosslinking of the resist could not be achieved, and the unreacted resist was washed away during development. A recommended method of overcoming this problem, for a Shipley SAL 603 photoresist imaged using an Electron-beam 20 KeV, is to deposit a layer of Al
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or titanium over the aluminum substrate prior to applying the photoresist.
Japanese Patent No. 10048831 assigned to Sony Corp and granted Feb. 20, 1998, relates to patterning of a chemical amplification-based resist film on a film which is to be patterned. The composition of the film to be patterned is not specified in the English abstract of the Japanese patent. The formation process comprises: (a) covering the film to be patterned with a protective coating consisting of chalcogen except sulphur; (b) depositing the chemical amplification-based resist film on the protective coating; (c) applying selective exposure, baking after exposure, and development to the chemical amplification-based resist film to form a resist pattern; and (d) selectively removing the exposed portion of the protective coating. The advantage is said to be that the surface of the film to be patterned is previously passivated by the protective coating. This prevents diffusion of active species between the chemical amplification-based resist film and the film to be patterned and prevents the active species from a decrease in its concentration around the interface against the film to be patterned. The resulting resist pattern is said to have “no unusual shape”.
International Application WO99/53378 of S. Funato et al., assigned to Clariant Int. Ltd., published Oct. 21, 1999, describes a method of forming a pattern in a photosensitive film made from a chemical amplification resist material. The method is said to provide high resolution and high precision by preventing reaction products from being formed at the interface between an anitreflection film and a photosensitive material film. This is accomplishe
Albelo Jeffrey A
Montgomery Melvin W.
Applied Materials Inc.
Church Shirley L.
Rosasco S.
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