Simulation of the optical effects of particles residing at the bottom of KrF positive photoresist films coated on Si substrates

The reflection effects of Si, SiO2, and Al particles on developed cross-sectional photoresist patterns are simulated by using a two-dimensional waveguide model. The particles were assumed to reside at the bottom of chemically amplified positive photoresist film coated on the Si substrates. The reflection effects were investigated in both cases of particles on the flat surface and on the side slope of the stepped pattern of the substrates. The smallest sizes of particles capable of causing pattern shorts are discussed through a comparison between this work and the authors’ previous work, where the particles reside at the top of photoresist film. In conclusion, the smallest sizes of particles residing at the bottom of the resist film are larger than those of particles residing at the top of the resist film. In addition, because the reflecting light exposes the bottom of the positive resist, after development it apparently helps to realize 0.2 μm critical dimension. Thus the smallest size of the Al particle ...