Photosensitive polyimide

OGG Microelectronic Materials, Olin/CIBA-GEIGY venture photosensitive polyimides, high performance semiconductors... 

Photosensitive functions are in many cases also heat sensitive, so the preparation of photosensitive polyimides needs smooth conditions for the condensations and imidization reactions. Some chemical reactants, which can be used for polyamide preparation, have been patented for the synthesis of polyimides and polyimide precursors. For example, chemical imidization takes place at room temperature by using phosphonic derivative of a thiabenzothiazoline.102 A mixture of N -hydroxybenzotriazole and dicyclohexylcarbodiimide allows the room temperature condensation of diacid di(photosensitive) ester with a diamine.103 Dimethyl-2-chloro-imidazolinium chloride (Fig. 5.25) has been patented for the cyclization of a maleamic acid in toluene at 90°C.104 The chemistry of imidazolide has been recently investigated for the synthesis of polyimide precursor.105 As shown in Fig. 5.26, a secondary amine reacts with a dianhydride giving meta- and para-diamide diacid. The carbonyldiimidazole... 

K. Horie and T. Yamashita, Photosensitive Polyimides, Technomic, Lancaster, PA, 1995. 

Phosphoms pentoxide-methanesulfonic acid (PPMA), 315 Phosphorylation, 187 Photoacid generator (PAG), 317 Photoluminescence, 490 Photosensitive polyimides, 270-271, 292 PHRRs. See Peak heat release rates (PHRRs)... 

Positive imaging techniques, 19 201 Positive ion spectroscopy, 24 107 Positive photochromism, 6 588 Positive photoresists, 20 280-281 Positive photosensitive polyimides,... 

Poly(amic acids) in which the ortho-carboxylic group has been chemically modified to either an ester- or amide moiety have been known for many years. However, their commercial significance was non-existent until very recent applications involving dielectric insulators [48] and photosensitive polyimide precursors [49, 50]. As with many synthetic pathways, there are generally several ways to arrive at the same goal. Similarly, the preparation of derivatized poly(amic acids) can be divided into two general categories ... 

Figure 19. Process steps for patterning polyimides by wet etching and dry etching and for direct photopatterning of a photosensitive polyimide. The abbreviation PR stands for photoresist.

Direct Patterning of Photosensitive Polyimides. Photosensitive polyi-mides (PSPIs) are recently developed materials that can be directly photo-patterned like a negative photoresist (80,85,88,146-148). The most common PSPIs are polyamic acids that have been esterified with photoreactive alcohols and combined with photoinitiators to form a polymer that will crosslink under exposure to UV radiation and become insoluble. The unexposed material is selectively dissolved in a developer solution, and the patterned film is then cured to convert the cross-linked polyamic acid to a polyimide and drive off the cross-linking groups. 

An all-polyimide microchannel chip was created by patterning two photosensitive polyimide layers, and then by laminating the two layers based on a partially imidized interfacing layer [228,229]. 

K. Horie, Introduction to Photopolymers and Microelectronics, in K. Horie, T. Yamashita (Eds.), Photosensitive Polyimides, Technomic Publishing Company, Inc., Lancaster, PA, 1995. 

Sashida N, Hirano T, Tokoh A (1989) Photosensitive polyimides with excellent adhesive property for integrated circuit devices. Proc Electron Compon Conf 39th 167070 82... 

Horie K, Hamashita T (1995) Photosensitive polyimides fundamentals and applications. Technomic, Lancaster Basel... 

Efforts continue in the Far East, particularly in Japan, by Horie et al., on photosensitive polyimides containing epoxide groups [44,45]. These studies focus on the chemical amplification of photo crosslinks in the resulting materials for use in making mask materials in silicon chip fabrication. 

Title Photosensitive Polyimides for Optical Alignment of Liquid Crystals... 

The preparation of other aromatic diamines, (III), useful in preparing photosensitive polyimides effective as liquid crystal alignment agents is provided by the author [2]. 

Photosensitive polyimides with improved photospeed are supplied by Asahi Chemical, Ciba Geigy,... 

K. K. Chakravorty, C. P. Chien, J. M. Cech, M. H. Thnielian, and P. L. Young, High-Density Interconnection Using Photosensitive Polyimide and Electroplated Copper Conductor Lines, IEEE Comp., Hybrids., Manuf. Technol., 13, No. 1, pp. 200-206 (1990). 

Photosensitive polyimides have been found to be more useful for... 

Scheme 1.1. Chemistry of photosensitive polyimides exposure and cure.

V, White, R. Ghodssi, C. Herdey, D.D. Denton and L. McCaughan, Use of photosensitive polyimide for deep X-ray lithography, Appl. Phys. Lett, 66 (1995) 2072-2073. 

White V, Ghodssi R, Herdey C, Denton DD, McCaughan L. Use of photosensitive polyimide for deep x-ray lithography. Appl Phys Lett 1995 66 2072-3. 

M. Asano and H. Hiramoto, Photosensit. Polyimides, (Technomatic, Pa)(Eds. K. Horie andT. Yamashita),1995,121. 

The differences between the curing of the polyamic acids and their tertiary amine salts or esters is even larger. The Toray Photoneece photosensitive polyimide (which is a tertiary amine salt of BTDA/ODA polyamic acid) begins reacting at much lower temperatures and the reaction is completed faster during the temperature ramp (see Table 2 and Figure A). This effect is consistent with work of Kruez et al. (O on tertiary amine salts of PMDA/ODA polyamic acid. 

Lastly, the polyimide has some inherent photosensitivity. The use of a photosensitive polymer requires fewer processing steps, which also implies an increased yield for the circuit. Ciba-Geigy announced the formulation of inherently photosensitive polyimides in 1985.(5) The use of an inherently photosensitive polyimide is attractive because no sensitizers are added to contaminate the final resin, no functionality is added which degrades the thermal and chemical resistance, and fewer volatiles are present to contaminate the resin or equipment than in some other approaches to photosensitive polyimides. Recent work has shown that these polyimides crosslink on irradiation through hydrogen abstraction by triplet benzophenone and subsequent coupling of the resultant radicals. ... 

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