A. Bhogra, L. Ngo
Stanford University,
United States
Keywords: characterization, SiO2, etching
Summary:
Achieving precise control over the etch rates and sidewall profiles of SiO₂ is critical in fabricating high-resolution nanostructures. This work focuses on characterizing the etch rate of silicon dioxide and optimizing the sidewall profile using the Oxford Plasma Pro 80 Reactive Ion Etcher (RIE) at Stanford’s Nanofabrication Shared Facilities. First, the etch rate is determined by measuring oxide thickness using the Filmetrics F40 before and after a blanket etch. The repeatability is monitored with a blank control wafer to maintain an etch rate of approximately 65 nm/min. Once complete, ~200 nm of CSAR 62 resist is spin coated onto a 4-inch silicon wafer. Spin curves are measured to find consistent thickness based on varying spin speeds (RPM). A pattern composed of rows with varying widths is exposed onto the sample using electron beam lithography (Raith EBPG 5200). The pattern is designed in KLayout and goes through proximity effect correction and conversion in Beamer. After developing, the sample is etched in the RIE using a standard recipe (CHF3, CH4, Ar). The sample is then cleaved to expose the cross section, which is imaged in the scanning electron microscope (Zeiss Gemini SEM) to measure sidewall angles. Process steps are modified and iteratively optimized to achieve vertical (90°) sidewall angles.