Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
1998-10-22
2003-09-02
Hamilton, Cynthia (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S270100, C430S905000, C430S920000, C430S286100, C522S063000
Reexamination Certificate
active
06613495
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to i-line photoresist compositions for printed circuit applications which are imageable by exposure at i-line wavelengths of about 320 to 420 nanometers. In particular this invention is directed to a photoresist composition that will unexpectedly reduce line growth of the resist image of the printed circuit and unexpectedly has a longer shelf (storage) life than would have been expected.
2. Description of the Art
Photoresists are photosensitive films used to transfer images to a substrate. They are applied as liquid coatings or dry film compositions to a substrate to provide a photosensitive resist article. After forming the film on the substrate, the film is exposed through a patterned photomask to a source of activating energy such as light to form a latent image thereon after development. The photomask has areas opaque to activating radiation and other areas transparent to activating radiation. The pattern in the photomask of opaque and transparent areas defines a desired image that may be used to transfer the image to a substrate. A relief image is provided by development of the latent image pattern in the resist coating. The use of photoresist coatings is generally described, for example, by DeForest, Photoresist Materials and Processes, McGraw Hill book Company, New York (1975), and by Moreau, Semiconductor Lithography, Principals, Practices and Materials, Plenum Press, New York (1988) as well as in U.S. Pat. No. 5,366,846, the entire contents of this patent are incorporated herein by reference hereto. While the teachings of the above mentioned U.S. Pat. No. 5,366,846 are quite significant, it has been found that after development of the imaged photoresists, line growth of the resist had occurred. Therefore, there is still a need for better sidewall definition without substantial line growth during processing. The composition of the present invention provides a composition that even further reduces line growth of the resist sidewalls during development. Line growth produces etched lines which do not properly reproduce the desired geometries as defined by the mask.
Reference should also be had to the following for a greater understanding of the art: U.S. Pat. Nos. 5,034,304; 5,128,232; 4,189,323, 3,954,475 5,057,397, 5,340,697, 4,826,753, 5,180,653, 5,340,697, and the following patents or publications: Canadian Patent No. 2100,392, Japan 63075737A2, Japan 05,303,196; 05,281,727 and European Patent Application Nos. 0 458 325, 0 519 298, 0 621,509, 0 483,689, 0 483,693 and 0,672,954.
SUMMARY OF THE INVENTION
The present invention provides novel radiation sensitive coating compositions that are characterized in part as providing a cured coating layer that exhibits substantial flexibility as well as reducing line growth thereof during processing after a photoimaging step. In general, a composition of the invention comprises a resin binder, a reactive oligomer that comprises one or more internal crosslinking groups, and a radiation sensitive component (photoacid generator) that is photoactivatable at a wavelength of from about 320 to 420 nanometers. Such materials may be a substituted triazine compound or a substituted oxadiazole compound which produces an acid when activated by light energy at the wavelengths set forth above. As used herein, the term “reactive oligomer” refers to a material that is a polymer molecule containing a number of repeating units, e.g., 2 to 50 and that is crosslinkable when in contact with photogenerated acid such as provided by triazines and oxadiazoles. Such reactive oligomers include materials such as the epoxidized butadiene family (See U.S. Pat. No. 5,366,846 incorporated herein by reference hereto), acetals, vinyl ethers and others as would be clear to those skilled in the art after reading this application.
While substantially non-reactive resin binders are suitably employed in the compositions of the invention, preferably the resin binder is a reactive polymer that can undergo photoactivated crosslinking with one or more components of the composition.
A variety of resin binders can be employed. Suitable reactive resins are those that contain a functional group that can react with one or more other components of the composition, for example a reactive hydrogen containing resin. Generally preferred reactive resins are phenolic resins. With respect to the crosslinker component, a variety of crosslinking agents may be employed. Preferred crosslinkers include an epoxy-containing materials and amine-based crosslinkers such as melamines, ureas, guanamines and mixtures thereof. Such crosslinkers will cure to form a polymerized network with the resin binder and reactive oligomer. Compositions of the invention are suitable for use as a liquid coating composition as well as a dry film.
The compositions of the invention have utility in a variety of applications. Hence, the invention includes processes employing the compositions of the invention, including processes for forming a relief image, processes for forming an imaged dielectric layer on a substrate, and processes for the manufacture of printed circuit boards, additive printed circuits, multilayer printed circuits, high density printed circuits, flexible circuits, surface mount devices, multichip modules, sequential build and other articles. The invention further provides novel articles of manufacture comprising substrates coated with the compositions of the invention.
The terms “crosslink”, “crosslinking” and other such terms used herein refer to any reaction of one or more of the components of a composition of the invention that results in reduced developer solubility of the composition.
Products such as these above are first photochemically set, the unwanted areas removed, and the remaining organic material is thermally fully set, i.e., hardened to its ultimate state.
DETAILED DESCRIPTION OF THE INVENTION
A composition of the invention in general comprises a resin binder, an acid sensitive crosslinkable oligomer and a radiation activated component which produces an acid after radiation is directed thereon at wavelengths between about 320 to 420 nanometers. Preferably the compositions further include a crosslinking agent component in addition to the reactive oligomer.
The resin binder component may comprise a nonreactive resin or, preferably, the resin binder is a reactive resin that can undergo photoinitiated crosslinking with one or more components of the composition either photochemically or thermally. The resin binder preferably imparts aqueous alkaline developability to the composition. Thus, preferred resin binders include resins that contain polar functional groups, such as hydroxyl or carboxylate, that can impart aqueous alkaline developability. Further, the resin binder component is preferably employed in a composition in a concentration sufficient to render unexposed portions of a coating layer of the composition aqueous alkaline developable.
The term “nonreactive resin” as used herein refers to a resin that does not substantially polymerize with one or more of the components of the composition upon photoactivation of the same. Thus, upon curing of a composition, a nonreactive resin binder typically will be encapsulated within the polymerizable component(s) of the composition. Suitable nonreactive resins include, for example, urethanes, silicones, acrylates and the like. The resin binder component suitably may comprise both nonreactive and reactive resin binders.
A reactive resin binder is suitably any of a variety of materials that will undergo photoinitiated crosslinking with one or more components o the composition. Thus suitable resins include those that contain one or more reactive moieties, for example a functionality that contains a reactive hydrogen. Phenolic resins are particularly suitable reactive resins and are preferably employed in a concentration sufficient to render a coating layer of the composition developable with an aqueous alkaline solution or semi-aqueous alkaline solution. Suitable phen
Corless Peter F.
Hamilton Cynthia
Shipley Company L.L.C.
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