Research activities of photolithography by synchrotron radiation from Indus-1 and Indus-2

Our electron storage ring Indus-1 (450 MeV, 100 mA) will soon be commissioned. The critical wavelength is 61 Å. Using the wiggler, spectral flux can be enhanced at 10 Å. Hence our research work is oriented to: (i) development of master masks both for contact and proximity printing, (ii) a study of the effects of VUV and soft X-rays from synchrotron source on photoresists in SXRL. Mylar is chosen in this region as a master mask substrate for its excellent optical properties. Using the conventional photoresist system in UV lithography, pattern details of 5 μm were printed on Mylar deposited with AuCr films. Later on, by depositing TiPdAu films and Waycoat resists, pattern delineation by optical lithography gave resolution features as small as 1.2 μm. Resists of both positive and negative tones were used. UV exposure (10 mW/cm2 for 7 s) was done under ambient conditions. Contrast details of pattern were estimated by measuring the optical densities. To investigate the fundamental aspects of resist decomposition by SR radiation, (5 to 20 Å) from Indus-2, mass spectrometric analysis of residual gases is performed. It is most probable, that the PMMA and Novolac-based resists with light sensitive resins may be changed to a chemically different layer for example a highly cross linked layer. Resist coated Si wafers were held inside a multiport UHV chamber fitted with QMS and gauge heads, which was evacuated to 1 × 10−6Pa by TMP and sputter ion pump. Unfiltered UV radiation excited the resists whose energy is measured using a thermopile. Chemical reactions of the resists, when exposed by DUV, soft X-ray or electron beam are discussed. Resist annealing may be essential to withstand SR radiation. The above experimental data from the resists irradiated by synchrotron radiation is of paramount importance especially when we do SXRL work in Indus-2. We also plan to introduce the LIGA process for making special optical and micromechanical devices using SXRL. Results and experiments of the above works are discussed.