Pattern transfer of sub-100 nm features in polysilicon using a single layer photoresist and extreme ultraviolet lithography

Until recently, pattern transfer of 100 nm-scale features using extreme ultraviolet lithography (EUVL) was accomplished by using an intermediate hard mask material such as silicon oxide or silicon oxynitride (1). In this experiment, a single layer of deep-UV photoresist, 175 nm thick, was patterned using Sandia's 10x-Microstepper EUV imaging system. The pattern was subsequently transferred into an underlying polysilicon layer, 300 nm thick, using a reactive ion etch process. Cross-sectional and top-down scanning electron microscopy analysis was performed to evaluate the etch process and determine sidewall angle and the etch selectivity between polysilicon and the photoresist, and were found to be >85 degrees and approximately 5:1, respectively.