Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2001-07-23
2004-03-09
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S290000, C430S311000, C430S313000, C430S330000, C430S945000, C430S950000
Reexamination Certificate
active
06703169
ABSTRACT:
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 a particular combination of process steps useful in preparing optically imaged high performance photomasks. The optical imaging of the photomask makes use of a deep ultraviolet (DUV) photoresist in combination with at least one antireflective coating (ARC). The DUV photoresist is imaged using an optical direct write continuous laser mask writing tool.
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. Additional work has been done recently using a direct write continuous wave laser tool available under the trade name ALTA™ from ETEC Systems Inc., Hillsboro, Oreg.
Preparation of a photomask/reticle is a complicated process involving a number of interrelated steps which affect the critical dimensions of a pattern produced in the reticle, and the uniformity of the pattern critical dimensions across the surface area of the reticle. By changing various steps in the reticle manufacturing process, the reproducibility of the manufacturing process itself may be altered, including the processing window. Processing window refers to the amount process conditions can be varied without having a detrimental outcome on the product produced. The larger the processing window, the greater change permitted in processing conditions without a detrimental affect on the product. Thus, a larger process window is desirable, as this generally results in a higher yield of in specification product produced.
Various efforts are made within the industry to improve the reliability of manufacturing processes by improving individual process steps; however, when a production process involves a number of interrelated process steps, alteration of an individual process step may have an unexpected result on other interrelated process steps.
The reticle manufacturing process steps generally include the following, where the initial substrate used to form the reticle is a silicon oxide-containing base layer having a layer of a metal-containing (typically chrome) mask material applied thereover. An inorganic antireflective coating (ARC) or an organic ARC, or a combination of inorganic and organic ARC layers may be applied over the surface of the chrome mask material. A photoresist layer is then applied over the antireflective coating. The photoresist is typically an organic material which is dissolved or dispersed in a solvent. The solution or dispersion of photoresist is typically spin coated onto the surface of the photomask fabrication structure. Typically, the photoresist is applied over an ARC layer on the fabrication structure surface. Some of the solvent or dispersion medium is removed during the spin coating operation. Residual solvent or dispersion medium is subsequently removed by another means, typically by baking the fabrication structure, including the photoresist layer. This step is commonly referred to as “Post Apply Bake” or PAB. The photoresist is then exposed to radiation (imaged), to produce a pattern in the photoresist layer, typically by a direct write process when the pattern includes dimensions which are less than about 0.3 &mgr;m or less. After exposure, the substrate including the photoresist layer is baked again. The second baking is typically referred to as “Post Exposure Bake” or PEB. The photoresist is then developed either using a dry process or a wet process, to create the pattern having openings through the photoresist layer thickness. Once the photoresist is “patterned” so that the pattern openings extend through the photoresist layer to the upper surface of an ARC layer, or to a surface beneath an ARC layer, the pattern in the patterned photoresist is transferred through the chrome-based mask layer and any remaining layers overlying the chrome layer, for example, typically by dry etching.
U.S. patent application, Ser. No. 09/848,859, filed May 3, 2001, titled: “Organic Bottom Antireflective Coating For High Performance Mask Making Using Optical Imaging” now U.S. Pat. No. 6,605,394, and assigned to the assignee of the present invention, describes a reticle fabrication process in general. This patent application is hereby incorporated by reference in its entirety. As disclosed in the '859 application, there are a number of problems encountered in trying to produce a photomask/reticle when the photomask pattern exhibits critical dimensions of less than 0.3 &mgr;m. Further, producing a reticle where pattern critical dimensions are uniform across the entire reticle surface requires careful control of process variables in each step of the reticle manufacturing process. For example, the developed (patterned) photor
Albelo Jeffrey A.
Buxbaum Alex
Fuller Scott
Montgomery Melvin W.
Applied Materials Inc.
Barreca Nicole
Church Shirley L.
Huff Mark F.
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