JAPAN Organic azide molecules and/or azide polymers are widely used as photosensitive materials i n modern industries such as i n mi crol i thography. In a previous paper [1], poly(styrene-co-vinylbenzyl azide) (AZMS) was synthesized as one of the polymer resists, and photocrosslinking mechanism of AZMS sensitized by thioxanthone [9H-thioxanthen-9-one] (TX) and 2,4-di i sopentyl thi oxanthone (DITX) was studied in solid polymer matrices. In these systems, TX and DITX transfer their triplet

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... y to AZMS, and initiate the crosslinking by generating the nitrene from the excited azido group in AZMS. Energy diagram of these systems are schematically shown i n Fig. 1. The efficiency of generation of the nitrene measured from the volume of nitrogen evolved is dependent on the concentration of the azido group in AZMS [2]. This is due to the fact that autocatalytic chain reaction of the azide decomposition takes place in solid AZMS/TX and AZMS/DITX systems [2,3]. Furthermore, the efficiency of photocrosslink formation increases by the application of an external magnetic field of ca. 0.1 T. In this study, in an attempt to understand the sensitization processes of TX and DITX in AZMS polymer matrix, the self-quenching process of TX and DITX was investigated using Nd:YAG laser flash photolysis, and several factors which determine the lithographic sensitivities of these systems are discussed. AZMSs with different monomeric ratios of styrene and vinylbenzyl azide (VBA) were prepared by copol ymeri zati on i n deaerated benzene solution. The detailed procedures were described elsewhere [1] . Molecular weights and compositions of five batches of AZMSs (AZMS1 -AZMS5) are listed in Table 1. 225