Photoresist stochastic defect generation depending on alkyl chain length and concentration of tetraalkylammonium hydroxide in alkali aqueous developer

The effects of photoresist dissolution on randomly occurring (“stochastic”) pattern defects in extreme ultraviolet (EUV) lithography were investigated. Specifically, the effects of the alkali concentration of two developers of different alkyl chain lengths; tetramethylammonium hydroxide and tetrabutylammonium hydroxide (TBAH) on stochastic defect generation were investigated for two typical EUV photoresists. In the case of the PHS-type photoresist, results show that stochastic defect generation was almost the same regardless of developer type, given the same developer concentration. For the hybrid-type photoresist, a decrease in stochastic defects was found with the application of the longer alkyl chain length TBAH developer. Results also suggest the existence of an optimum developer concentration. Such optimum developer concentration is considered to be affected by the balance between polarity and non-polarity of the photoresist and developer components.