Fabrication processes of microdevices and integrated microsystems are indispensable for the development of Micro-Electro-Mechanical Systems (MEMS). Reduction lithography becomes an important step in many new applications requiring ultra thick photolayers, large Critical Dimensions (CD) and tight control limits. For this market segment, the ASML SA 5200 reduction step-and-repeat system is a cost-effective tool for the manufacture of advanced microelectronics, MEMS, and Integrated Circuits (ICs). Along with this trend, manufacturing and development engineers, in order to better predict process interactions and better estimate process manufacturing, increasingly utilize modeling and numerical simulations.
This paper discusses the simulated and experimental lithographic performance of an i-line step-and-repeat system by using photosensitive DurimidesTM a photopolymer developed and commercialized by Arch Chemicals. These photopolymers are negative acting self-priming Polyimide precursors with a high photosensitivity, which provide thick layer exposure solutions with a wide process window. The excellent adhesion of DurimideTM films makes these materials suitable for MEMS, buffer-coat, and packaging applications. The range of film thicknesses used is from 6 μm up to 80 μm. Process windows for the different thicknesses are investigated and discussed in terms of Exposure Latitude (EL), Depth Of Focus (DOF), and Size linearity.
The lithography simulator PROLITH/2 with thick resist option has been used for all modeling activities in this work. Also, an extensive comparison is made between simulated and experimental data.