The composition and photolithographic processof high- thermostability ultraviolet positive photoresist

Photoresist is a crucial and fundamental material for photolithographic technology, which plays a vital role in microelectronic technique. The rapid development of lithography drives the microelectronic technique moving forward. With high-level and multifunctional photoresist, it can make finer patterns and meet the demand under harsh working environment such as high temperature. To evaluate the performance of the photoresist, one of the most important indicators is line/space resolution, while the composition of the photoresist and photolithographic process have a very significant influence on the resolution performance. Different composition may result in different photosensitivity and solubility of the photoresist, which have a significant impact on the performance. Moreover, the photolithographic processes include exposure dose (exposure time), developing time, the concentration of developer and so on. They all have severely affected the lithography pattern quality and lithography performance. Thus, the related research in detail is very necessary and it is conducive to maximize the performance of the photoresist and guide lithography process to be carried out smoothly as well. In this work, a high thermal-stability ultraviolet (UV) positive photoresist was obtained from the formulation of a self-made amide-imide copolymer as matrix resin, a 2,1,5-diazonaphthoquinone sulfonyl chloride derivative as photosensitizer, and solvent. The optimal composition and photolithographic process parameters was studied by simple variable method. It was found that the optimal composition was with the 1:4:10 (mass ratio) proportion of photosensitizer, resin and solvent, and the optimal photolithographic process parameters were about 4500 r/min spin-coating, prebake 1 min at 110°C hot plate, 30 s exposure time, 25 s development time in 1.0% tetramethylamine hydroxide (TMAH) aqueous solution, and post bake 5 min at 120°C hot plate. The imaging contrast of this photoresist was about 3.35, which indicated that the positive part and negative part of the pattern had obvious boundary. In the condition of contact exposure the lithography process above, the optimal line/space resolution was about 1 μm. In addition, the photoresist had high thermal-stability. After hard baking 30 min at 270°C, the photoresist had no obvious collapse of the photolithography pattern. This is because the self-made amide-imide copolymer has high thermal-stability and it acts as matrix resin in the photoresist. With the high thermal-stability property, the photoresist can meet the requirements of some used under high temperature environment and lays a foundation for the lithography technology being applied and developed under complex circumstance.