Characterization of resolution for integrated optical Mach-Zehnder Interferometer with optimization of photolithography process

This paper presents the characterization of resolution for Integrated Optical Mach-Zehnder Interferometer (IO-MZI) with optimization of photolithography process. IO-MZI is a type of optical biosensors that detect certain type of bacteria with typical device size of around 30 mm[1]. IO-MZI consists of line pattern with small width of approximately 4 μm which improves the sensitivity of IO-MZI to detect bacteria[2]. In this paper, photolithography process is used to transfer the line pattern of IO-MZI on silicon wafer. Nevertheless, finer line width is often difficult to be fabricated. This is because high development rate of positive photoresist (PR) increase risk of over-development. Therefore, optimization of photolithography process is needed to increase success rate of finer line width fabrication with high resolution. High resolution indicates the line pattern fabricated contains almost similar width with the width of line pattern designed on photomasks. Nevertheless, the chemical composition of PR and developer would be affected by optimizing photolithtography process parameters. This is thus analysis of variance (ANOVA) is performed on resolution of line pattern fabricated with 2-level full factorial design of experiment (DOE) For each process recipes, resulted width of line pattern indicates the quality of resolution in accordance to the line width designed on photomasks. Lastly, optimum treatments are selected which gives high resolution for line pattern transfer in IO-MZI by referring to the characterization result from ANOVA.