SU-8胶光刻工艺研究

SU-8胶是一种基于环氧SU-8树脂的环氧型的、近紫外光、负光刻胶.其专门用于在非常厚的底层上需要高深宽比的应用.但是SU-8胶对工艺参数的改变非常敏感.本文对影响光刻后图形质量的主要工艺参数前烘温度和时间、中烘温度和时间、曝光时间及显影时间进行了研究,发现前烘时间和显影时间是影响图形分辨率及高深宽比的最主要的参数.随后给出了200μm厚SU-8光刻胶的建议工艺条件:200μm/s甩胶,1h的95°C前烘,近紫外光(400nm)接触式曝光,95°C的中烘 30min,PGMEA中显影20min.另外对实验中实现的主要问题基片弯曲和光刻胶的难以去除作了一定的探讨,给出了合理化建议:对于基片弯曲可采用以下四种措施来降低,降低中烘的温度同时增加中烘的时间、用厚硅片来代替薄硅片、对于薄硅片在前烘后可用金刚刀切成4～8小片、适当的设计掩模板;对于光刻胶的去除用热丙酮泡、超声清洗、反应离子刻蚀和高温灰化法相结合,能达到较好的效果.

Research on SU-8 resist photolithography process

SU-8 resist is an epoxy-type,near-UV,negative photoresist based on EPON SU-8 resin.The resist has been specifically developed for the applications requiring high aspect ratios in very thick layers. However, this photoresist has proven very sensitive to process variations. The main process variations influencing the pattern such as pre-and postbake temperature and time, exposure time and development time have been studied. And the conclusion that prebake and development time are the main factors affecting the image’s resolution and aspect-ratio,has been drawn.After analyzing the experiment results,a proposed fabrication process for 200μm SU-8 application is given as follows:coating at a speed of 200μm/s,prebaking at 95°C for 1 hour,near-UV（400nm） contacting lithography,postbaking at 95°C for 30 min and development for 20 min. In addition,the main two problems involved in the experiment are researched.One is the bend of substrate,which can be resolved by the following solutions:decreasing the postbake temperature and increasing the postbake time,using thick wafer instead of thin one, dividing the thin wafer into 4～8 pieces and designing the mask reasonably.The other is the removal of SU-8,which can be resolved by the combination of marinating in hot acetone,ultrasonic cleanout,RIE and cineration at high temperature.