| Abstract: | A new polymer system of semiconductor devices was studied in response to the multifunctional systems evolved. A variety of functional polymers have been developed in the manufacture of semiconductor and integrated circuit (IC) packaging devices by R&D of high-temperature polymers. With the increase in integration of electronic devices and the need to reduce overall size, market needs are moving to multilevel metallization. Toray's core polymer technologies for electronic devices in the past 35 years (1961–95) are reviewed. The new technology of IC encapsulants of biphenyl type epoxy compounds is described for the new generation 16 megabits dynamic randon accessory memory (DRAM) electronic memory device, with good heat dissipation characteristics and low stress with an anti-flammability UL V-0 property of halogen-free formulation. As core functions are built into devices, packaging and mount technologies become more important. A new photosensitive high-temperature polymer stable up to 500°C with photosensitivity and high resolution has been developed. The trend toward a high degree of integration in solid-state technology requires the use of new high-temperature photosensitive insulating materials. Toray's "Photoneece" system provides such versatile polyimide pattern-generation techniques, containing a unique photosensitive polyimide precursor which can be spun or coated on the substrate. The main components of polyimide consist of poly(amic acid), a tertiary amine having methacrloyl group and a sensitizer. Through analyses of visible, fluorescence and electron spin resonance (ESR) spectroscopy, and flash photolysis and quantitative analyses, a new reaction mechanism is proposed. By photo-irradiation, the stable ion radical is formed without vinyl radical polymerization. The polymer is excited to form an excited singlet state. An anion radical of pyromellitic diamide moiety in a polymer chain is generated after intersystem crossing to an excited triplet state. The resultant relief of the photosensitive polyimide precursor, after exposure to UV light with a mask, development and cure processing, is transformed into a cyclized aromatic polyimide. The new system has higher photosensitivity and resolution and eliminates three steps in the conventional pattern-making process for integrated circuits, resulting in a significant cost reduction. The characterization of pattern generation, the conversion to polyimide patterns, and the properties of both Photoneece and the patterns are discussed. Initial photoreaction of an ionic-bonded photosensitive polyimide was studied by fluorescence, ESR and flush photolysis. A charge transfer complex between a polyamic acid (polyimide precursor) and an aromatic amine (sensitizer) was formed by UV irradiation from fluorescence measurement. Photo-induced radical was observed by ESR measurement. The photo-induced radical was an anion radical of polyamic acid from flush photolysis. From these results, a new photo-induced charge separation in an ionic bonded photosensitive polyimide film was found. Photo-induced electron transfer from an aromatic amine (sensitizer) to acid part of the polyamic acid occurs. © 1997 John Wiley & Sons, Ltd. |
