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
2002-03-18
2004-08-17
Ashton, Rosemary (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
C430S325000, C430S326000, C430S905000
Reexamination Certificate
active
06777159
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for forming polyimide pattern using photosensitive polyimide and composition therefor. The present invention is useful for microscopic processing of semiconductors, thin film magnetic heads of hard disk drives and the like, and liquid crystal displays.
BACKGROUND ART
In production of various electronic parts including semiconductor integrated circuits such as LSI, thin film magnetic heads of hard disk drives and the like, and liquid crystal displays, very fine processing using lithography is employed, and photoresists are widely used in the processing.
For electronic devices, not only high density and high performance, but also large number of functions and high diversity are demanded, and photoresist patterns with sizes of as small as less than 1 &mgr;m are formed.
Therefore, the light source used for irradiation is now being shifted from g-line of mercury lamp (436 nm) to those having shorter wavelengths, that is, to i-line (365 nm) of mercury lamp, and further to KrF excimer laser (248 nm) and ArF excimer laser (193 nm).
Photoresist materials which are excellent in transparency to ultrashort wave, which have high sensitivity and high resolution, and which have resistance to etching for microscopic processing have been proposed.
Aliphatic compounds such as acrylic esters and alicyclic compounds of polyvinylphenol, which have higher Tg than the conventional novolak type resins have been proposed. However, a photoresist which may be used as a standard product, which satisfies the demands for positive-type photoresist, such as good development by alkali, adhesion to substrate and resistance to dry etching, has not been available.
Polyimides are excellent in heat resistance, mechanical strength, and electric insulation properties, and are recently applied to the field of semiconductors for which high reliability is demanded. Polyimides are applied in semiconductors as passivation films, buffer coat films, &agr;-ray-shielding films, interlayer insulation films and the like, and positive-type photosensitive polyimides which can be developed with an alkaline solution are now demanded rather than the conventional negative-type photosensitive polyimides.
Although it has been tried to give positive-type photosensitivity by converting polyamic acid which is an unstable intermediate of polyimide to an ester derivative, the compound is poor in stability during storage, and a heat treatment at a temperature not lower than 350° C. is necessary for imidation so that distortion is generated when the polyimide is used for lamination of semiconductors (Y. Yamaoka et al.: J. Photopoly. Sci. Tech. Vol.9 293(1996)).
The present applicant previously developed a photosensitive polyimide composition and filed a patent application directed thereto (WO99/19771). This photosensitive polyimide composition comprises a photoacid generator and a solvent-soluble polyimide which shows positive-type photosensitivity in the presence of the photoacid generator. This photosensitive polyimide composition is soluble in an organic solvent, excels in adhesiveness, heat resistance, mechanical properties and in flexibility, and exhibits the properties of highly sensitive positive-type alkali-soluble photoresist upon irradiation with light.
However, with the photosensitive polyimide composition disclosed in W099119771, satisfactory resolution is not necessarily attained when a pattern with high resolution is to be formed by selectively exposing the polyimide to a light having a short wavelength or electron beam.
DISCLOSURE OF THE INVENTION
Accordingly, an object of the present invention is to provide a method for forming thin film pattern of polyimide, by which a pattern having a high resolution may be formed by selective exposure with a light having a short wavelength such as i-line (365 nm) of Hg-line, KrF excimer laser (248 nm) or ArF excimer laser (193 nm).
The present inventors intensively studied to discover that by selectively exposing the polyimide obtained by polycondensation between an aliphatic or alicyclic tetracarboxylic dianhydride and an aliphatic or alicyclic diamine or diaminosiloxane, which polyimide is not disclosed in WO99/19771 to a light having a short wavelength or electron beam, a pattern having high resolution may be formed, thereby completing the present invention.
That is, the present invention provides a positive-type photosensitive polyimide composition comprising a solvent-soluble polyimide which shows positive-type photosensitivity in the presence of a photoacid generator, which is obtained by polycondensation of at least one aliphatic tetracarboxylic dianhydride and/or alicyclic tetracarboxylic dianhydride and at least one aliphatic diamine and/or alicyclic diamine and/or diaminosiloxane; and the photoacid generator. The present invention also provides a method for forming a pattern of positive-type photosensitive polyimide comprising the steps of forming a photosensitive layer consisting essentially of polyimide composition according to the present invention on a substrate; selectively irradiating the photosensitive layer with a light beam having a wavelength of not more than 365 nm; heat-treating the photosensitive layer; and developing the photosensitive layer after the heat-treatment to selectively remove prescribed regions in the photosensitive layer. The present invention also provides a use of the polyimide of the present invention as a material for positive-type photolithography. The present invention further provides a method for forming negative-type pattern of polyimide comprising coating a substrate with the polyimide in the polyimide composition according to the present invention; selectively irradiating the polyimide with an actinic ray, the irradiated regions constituting a desired pattern; and developing the irradiated polyimide with an alkaline solution to dissolve the non-irradiated regions. The present invention still further provides a use of the polyimide in the polyimide composition according to the present invention as a material for negative-type photolithography.
By the method of the present invention, polyimide thin film patterns having high resolution may be formed by selective exposure of the polyimide thin film to a light having a short wavelength or electron beam, such as i-line (365 nm) of Hg-line, KrF excimer laser (248 nm) or ArF excimer laser (193 nm). The photosensitive polyimide used in the method of the present invention is excellent in solubility in alkaline developing solutions, and has sufficient resistance to dry etching. Further, the polyimide has excellent insulation performance and heat resistance. Therefore, the present invention is advantageous for microscopic processing or the like of semiconductors, thin film magnetic heads of hard disk drives, liquid crystal displays and the like.
BEST MODE FOR CARRYING OUT THE INVENTION
The polyimide used in the method of the present invention is a solvent-soluble polyimide which shows positive-type photosensitivity in the presence of a photoacid generator, which is obtained by polycondensation of at least one aliphatic tetracarboxylic dianhydride and/or alicyclic tetracarboxylic dianhydride and at least one aliphatic diamine and/or alicyclic diamine and/or diaminosiloxane.
The polyimide shows positive-type photosensitivity when irradiated with a light in the presence of a photoacid generator, and shows negative-photosensitivity when irradiated with an electron beam in the absence of a photoacid generator (although it shows negative-type photosensitivity even in the presence of the photoacid generator).
The term “aliphatic tetracarboxylic dianhydride” means the tetracarboxylic dianhydride in which the moiety constituting the main chain of the polyimide consists of an aliphatic structure, and the number of carbon atoms constituting the aliphatic structure is preferably 1 to 15. The aliphatic structure may be either linear or branched, and may contain (an) oxygen atom(s) (ether, ketone or the like) and/or (a) nitrogen atom(s) (secondary, tertiary or
Gorwadkar Sucheta
Itatani Hiroshi
Itatani Tarou
Komuro Masanori
Matsumoto Shunichi
Ashton Rosemary
PI R&D Co., Ltd.
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