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Exposures leading to 0.18 micrometer or better resolution are now being demanded by IC development. Photolithography using 193 nm exposure tools is the leading technology for the development of these next generation of devices. We are reporting on our development efforts on the TER resist system, which is a single layer resist designed for image evaluation applications at 193 nm exposure wavelengths. The TER-system has been developed to allow equipment manufacturers to evaluate their equipment, to provide R&D lithographers with materials to qualify their 193 nm equipment and to determine process control parameters. The TER-system is a chemically amplified methacrylate resist terpolymer. It is composed of methyl methacrylate (MMA), methacrylic acid (MAA) and an acid labile acrylic ester. We have evaluated different leaving groups as the acid labile component and we report on the initial results of several. We also examined different onium salts as the PAG component. One such example is di(t- butylphenyl)-iodonium p-toluenesulfonate and we report on other examples which were used. We evaluated the thermal stability of the resins and thermal analysis showed they start to decompose at about 125 degrees Celsius when tetrahydropyranyl methacrylate is used. Other more thermally stable systems were also evaluated. Post apply bake (PAB) temperatures of 100 - 125 degrees Celsius were preferably used with the tetrahydropyranyl ester. Other more thermally stable esters, such as tetrahydro-4-methyl-2-oxo-2H-pyran-4-yl methacrylate (mevalonic lactone), ethoxy-ethyl methacrylate and 3-oxo-cyclohexyl methacrylate, also are described. Exposures in the range of 5 - 50 mJ/cm2 were typical and varied depending on the ester, the PAG, and other processing parameters. The acid catalyzed reaction rates after exposure were observed to be rapid. In all cases, post exposure bake (PEB) was typically carried out at 10 degrees Celsius or lower. Initial exposure evaluations at 193 nm and 248 nm show good resolution and image fidelity. The TER-system produced better than 0.225 micrometer resolution using 248 nm exposure equipment (NA equals 0.55) suggesting that better than 0.18 micrometer resolution is possible with 193 nm exposures. Results of resist synthesis, formulation and evaluation are presented.
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