Mechanical properties and pattern collapse of chemically amplified photoresists

The mechanical properties of positive tone chemically amplified resists UV6 and APEX-E ore :measured and used in finite element analysis (FEA) to dete rmine the mechanical compliance of photoresist lines as an indicator of the propensity for pattern collapse. Specifically, the residual strain is dete rmined by surface micromachined resist structures; the residual stress, exp ansion coefficient, and glass transition temperatures are determined from w afer curvature measurements; and the Young's modulus is calculated from the stress and strain. The results indicate that UV-6 has higher strain and a higher coefficient of thermal expansion than APEX-E. however, it has lower residual stress because its Young's modulus is 50%-70% lower than that of A PEX-E. FEA indicates that lines of UV6 have greater compliance than those o f APEX-E, and are more easily deformed by fluidic forces during develop and rinse steps. This is fully consistent with separate reports that demonstra te a greater likelihood of pattern collapse in UV6 than APEX-E, (C) 2000 Am erican Vacuum Society. [S0734-211X(00)08706-0].