Preparation of organic soluble polyimides and their applications in KrF excimer laser LIGA process

In this study two organic soluble polymides were successfully synthesized v ia polycondensation of a hexafluoropropyl group contained dianhydride with two kinds of diamines. These two polyimides (DMDB/6FDA, OT/6FDA) can be dis solved in most aprotic solvents (for example, NMP, DMAc) and many other com mon solvents (for example, THF, DMSO). The soluble polyimides also show goo d thermal-stability and high absorption at the KrF excimer laser wavelength (lambda = 248 nm). (The absorption coefficients of DMDB/6FDA and OT/6FDA w ere 1.26 x 10(5) cm(-1) and 1.49 x 10(5) cm(-1), respectively.) The photoab lation properties of the polyimides were studied in detail. Due to incorpor ating the hexafluoropropyl group into the chemical structure, these two pol yimides have higher etching rates than Kapton (a commercial PI film). The e ffects of exposure parameters on linewidth and taper-angle of polyimides wi th different chemical structure were also investigated here. Under the prop er control of exposure conditions, good precision patterns with near-vertic al side wall can be produced. The 300 mm thick comb-shape and Fresnel patte rns with 10mm linewidth have been made. Moreover, the complementary metalli c microstructure's have also been realized in the following electroforming procedure. The results showed that these two soluble polyimides were very s uitable for KrF Laser LIGA process.