Manipulation of development rate in photolithography process for optical biosensor

Abstract

This paper presents the optimization of photolithography process for line pattern transfer of optical waveguide for optical biosensor applications. Among different type of optical biosensor, integrated optical Mach-Zehnder interferometer (IO-MZI) is attractive due to inherent high sensitivity and accuracy. This type of interferometer is intended for many optical biosensor applications. However, line pattern with finer width complicates the photolithography process and often result in low success rate especially when immersion method of development process is used. This is because there are several uncertainties occurred when immersion development process is conducted such as agitation of developer disturbs the development rate of positive photoresist (PR). Due to this reason, the aim of this project is to improve the success rate of photolithography process by carefully manipulating the development rate of PR using different treatment combinations which is important for optical waveguide fabrication. In this context, the acceptable development rate with minimal risk of over-development can be obtained. The manipulation of development rate is based on the process parameters which are baking temperature, exposure time and developer concentration respectively. Design of Experiment (DOE) is performed on three process parameters with two level factorial design of photolithography process. After that, characterization of process parameters is performed using Analysis of Variance (ANOVA). ANOVA tests for the normality of DOE and significantly presents the P-value and effect size of each coded factors. In summary, this paper optimizes the process parameters of conventional photolithography process in order to obtain the optimum process recipe with high success rate of line pattern transfer for IO-MZI.