Multilayer resist dry etching technology for deep submicron lithography

Abstract

Using an O2+HBr mixed gas plasma,multilayer resist dry etching under low substrate temperature is applied to the 0.25 μm design‐rule 256Mb dynamic random access memory fabrication. Anisotropicetching profiles with a critical dimension (CD) loss less than 0.02 μm are obtained by optimizing the amount of HBr in the plasma. With exceeding amounts of HBr, the pattern width varies with the spacing of the patterned lines due to variations of the thickness of deposited on the resist sidewall, causing a large CD loss. This phenomenon is named ‘‘the pattern‐dependent deposition.’’ An increase in the HBr flow rate enhances the pattern‐dependent deposition. It is also found that the resist overetching can cause the pattern‐dependent deposition. An electron dispersive x‐ray spectroscopy analysis reveals that under etching conditions of the pattern‐dependent deposition, the characteristics of depositedfilm are similar to that of an oxidized silicon film. In comparison, the depositedfilm is close to the silicon‐rich film when there is no pattern‐dependent deposition. A mechanism of the pattern‐dependent deposition is discussed.