Resist roughness Bi-modality as revealed by two-dimensional FFT 2D analysis

Abstract

LER/LWR performance is currently considered as one of the major stumbling blocks complicating progress in the semiconductor technology. Line edge scans show that low frequency components clearly dominate the LER Power Spectral Density (PSD), thus implying a large characteristic length (>100-500 nm) phenomenon as the major LER source. Most of the theoretical analyses aimed to identify the origin of the LER were focused on the combined effect of exposure and CAR action statistics, and failed to explain the origin of this limit, which resulted in suggestions that there is more than just one phenomenon involved in LER generation. Depth profiling experiments were performed for a broad set of Polymer-PAG-Base combinations. Depth profiling PSD spectra have demonstrated that higher RMS values and correspondingly higher PSD amplitudes are associated with tighter PSD spectrum shifted towards lower frequencies (larger sizes of roughness features), which is very typical for all the cases investigated. The set of the PSD spectra obtained exhibit a pronounced bi-modal structure, indicating that there are at least two clearly noticeable independent roughness-controlling mechanisms.