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25 March 2010Process feasibility investigation of freezing free litho-litho-etch process for below 32nm hp
Double patterning with 193nm immersion lithography becomes to most promising candidate for 32nm half pitch node
and possibly below 32nm half pitch. Several double patterning methods have been suggested such as LELE (Litho-Etch
-Litho-Etch), LLE (Litho-Litho-Etch) and Spacer defined process, however, LLE process is pointed out as low cost
double patterning technique because of its simplicity. But LLE process needs new method to maintain 1st lithography
pattern and additional freezing processes have been suggested
In SPIE Advanced Lithography 2009, freezing free "Posi/Posi" process was introduced as candidate for LLE process.
This is LLE process that uses two different positive tone photoresists without freezing process. The resist for 2nd
lithography contains a specific solvent to prevent the mixing of two resists and there is an activation energy gap
between 1st and 2nd resists to maintain 1st lithography pattern. The double patterning can be successfully processed by
these specific resists without freezing process.
In this study, the performance of this freezing free "Posi/Posi" process is investigated for pitch splitting pattern using
1.35 NA exposure tool. The imaging results including CD control capability, and etching results are collected for 32nm
half pitch and below. Additionally the two-dimensional pattern imaging is also obtained for 76nm minimum pitch.