Recent development status of rinse material for EUV lithography

Extreme ultraviolet lithography is one of the promising high volume manufacturing processes for devices below 7 nm node and beyond. However, resist pattern collapse is one of the hurdles in achieving a comfortable process margin/window for resist patterning. To suppress this resist pattern collapse and to improve manufacturing process margin, undoubtedly it is a well-known fact that the rinse materials can mitigate a pattern collapse at development process. In this study, we focus on the relationship between resist swelling and pattern collapse, based on the assumption of resist pattern softening induced by resist swelling and further resist pattern bending or deformation which could be classified as pattern collapse. To verify this model, two samples of Rinse-A and Rinse-B which showed similar capillary force but different resist swelling behavior expected, respectively, were prepared. And the hardness of the resist films treated using those rinse materials together with de-ionized water as reference rinse, were measured using nano-indentation measurement technique. From the result, it was found that Rinse-A had the resist film hardness reduced by 7.9 % as compared to that on de-ionized water. On the other hand, Rinse-B which was designed to suppress the penetration of additives into the resist film, exhibited comparable hardness property to that on reference rinse, de-ionized water. Finally, the evaluation of lithographic performance of the photoresist in different rinse process conditions using Rinse-A and Rinse-B was carried out, and Rinse- B achieved 12.7 nm minimum pattern size of resist feature at 16 nm half pitch printing by interference projection system on Extreme Ultraviolet lithography, whereas Rinse-A showed 16.5 nm.