Hidetaka Satou

Photosensitive polyimide for IC devices

Photosensitive polyimide has potential applications for interlayer insulation, alpha-ray shielding, and buffer coating of IC and LSI devices because it offers reduction in processing time. There are two main methods used to photosensitize polyimide. One is based on ion bonding and the other on covalent bonding between polyamic acid and photosensitive groups. The sensitivity, resolution, and mechanical properties such as tensile strength, elongation, and adhesion strength of the photosensitive polyimides have been investigated. The studies indicate that the covalent-bonding type is better than the ion-bonding type in terms of optical properties; the physical properties of the ion-bonding type, however, are much better. In terms of the physical properties conventional nonphotosensitive polyimides still have superior properties compared to photosensitive polyimides.<<ETX>>

New screen-printable polyimide for IC devices

In order to develop a screen-printable polyimide paste, the structures, properties, and ratios of three major paste components (filler, binder, and solvent) were studied, and a film-forming strategy was established. This strategy comprises a novel type of polyimide particle filler, which can be dissolved in the binder and the solvent under the curing condition. A screen-printable polyimide paste was developed using this strategy. This paste gives uniform film with better mechanical properties than conventional polyimide paste, which comprises an insoluble polyimide particle filler. The effect of the solubility parameter of the solvent on mask swelling and moisture resistance was also examined. It was also examined. It was found that a lactone with a solubility parameter value of 18 approximately 20 (MJ/m/sup 3/)/sup 1/2/ is suitable as a paste solvent. The paste affords uniform pinhole-free polyimide films with good mechanical properties. As the mask swelling is low, the lifetime of stencil is longer than that of conventional pastes. >

New polyimide for multi-chip module application

P-terphenyltetracarboxylic dianhydride (p-TPDA), which has a rodlike structure, has been developed as a raw material for polyimides in order to reduce the propagation delay time associated with polyimide packaging for multichip modules. The coefficient of thermal expansion (CTE) of the polyimides derived from p-TPDA is approximately 2*10/sup -6/. This is much lower than that of conventional polyimides derived from bisphenyltetracarboxylic dianhydride (BPDA), which have a CTE of 8*10/sup -6/ K/sup -1/. Another attribute that these polyimides have is low dielectric constant, with a typical value of about 2.9. As a result, this polyimide can give improved performance when used in multichip module applications.<<ETX>>

Photosensitive Polyamic Acids Developable with Aqueous Alkaline Solutions

New negative-type photosensitive polyamic acids, precursors of polyimides, developable with aqueous alkaline solutions were synthesized. Among diamine monomers having a photofunctional group, 2′-(methacryloyloxy)ethyl 3,5-diaminobenzoate yields high molecular weight polyamic acids. A photosensitive polymer composition consisting of Michlers ketone and a thermally stable peroxide, 3,3′,4,4′-tetrakis(t-butyldioxycarbonyl)-benzophenone, results in high photosensitivity. The photosensitive coating of the composition is soluble in aqueous alkaline solutions as well as in organic aprotic polar solvents and either can be used as a developer of the coating. However, resolution of the patterns is quite different especially with thick films. Solvent developers result in poor resolution whereas aqueous alkaline developers give patterns of high aspect ratio even with thick films. This is probably due to the difference in the diffusion efficiency and swelling property of the polymer to the developers. Effects of copolymerizing with an ordinary diamine monomer on photosensitivities and film properties of the polyimides derived from their precursors are also discussed.