Characterization of Protex® PSB thin film as a photosensitive layer for MEMS capacitive pressure sensor diaphragm based on SiC-on-Si wafer
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The ProTEX® PSB thin film as a photosensitive layer has been released in the market as an alternative replacement for silicon nitride or silicon oxide wet etch masks. In this work, this film has been deposited on SiC-on-Si wafer for the back-etching of the bulk Si to leave SiC thin film to be used as a pressure sensor diaphragm. This paper will discuss the process flow to estimate the optimized ProTEX® PSB thin film thickness for the sufficient back-etching of the 300um bulk Si. This thickness is defined by the following parameters: spin-coating rotational speed, final cure temperature and hard bake time of coating. Several samples of ProTEX® PSB thin films have been preliminary characterized by infinite focus microscopy (IFM) and scanning electron microscopy (SEM) to examine the substrate surface conditions and the effects of undercut edges structure. Based on these data, it was determined that the optimum thickness of ProTEX® PSB for this project is 2.133 μm with the spin speed of 3000 rpm, the first bake temperature of 110 °C in 120 seconds and the second bake temperature of 240 °C in 60 seconds. We conclude that ProTEX® PSB can withstand the etch mask with etch rate of 1.28 μm/min for 8 hours and gives good quality effect of undercut edge on the SiC-on-Si wafer.
Key Engineering Materials
Microelectromechanical Systems (MEMS)
Microelectronics and Integrated Circuits