Freezing Material Development for Double Patterning Process

Double patterning is one of the most promising lithography techniques for sub-40nm half-pitch device manufacturing. Several variations of double patterning processes have been reported by research groups, including a dual-trench process (litho-etch-litho-etch) and a dual-line process (litho-litho-etch). Between these, the dual-line process attracts the most attention because it is a simple process and achieves high throughput. However, there is concern that the second lithography process damages the first lithography patterns in the dual-line process. Therefore, new technology must be developed to keep the configuration of first lithography patterns during the second lithography step, and to make this patterning process practical. Recently, we succeeded in forming 32 nm half-pitch LS lithography patterns by the introduction of a new "freezing" step. This step involves covering the first lithography pattern with a chemical freezing material to prevent damage by the second lithography process. This process, so called "litho-freezing-litho-etch" process, will achieve higher throughput and lower cost compared to litho-etch-litho-etch. In this study, the performance of this chemical freezing double patterning process was investigated for various applications using a hyper NA immersion exposure tool. Imaging results including process window and etching results of sub-30nm half-pitch LS and 40nm half-pitch CH with this freezing process were shown. Furthermore, items such as critical dimension uniformity and defect inspection using the freezing process were reviewed. Additionally, to simplify the double patterning process, we developed a new material called "self freezing resist". Self freezing resist requires only one step bake to prevent damage by the second litho process. Litho performance of self freezing resist was reviewed.