Characterization of Novolac Based Photoresists to Fabricate 3D Polymer Dome Features

Wafer level, 3D, free standing structures (e.g., domes or hemi-cylinders) can be fabricated using polymer dome features as sacrificial templates for MEMS and interconnect applications. Understanding the kinetics of dome formation and the material properties are essential for a robust and manufacturable process of controlling the size and shape of the photoresist features. In this paper, temporal and thermal characteristics of Novolac based photoresists are presented as a function of solid loading and solvent type using analytical techniques such as Thermogravimetric Analysis (TGA), Fourier Transform Infrared (FTIR) spectroscopy, hot stage microscopy, and Gas Chromatography/ Mass Spectrometry (GC/MS). The solid loading influences the thickness and processing ability of the resist. The solvent evaporation rate controls the final size and shape of the 3D polymer dome features. Solvent is the primary material lost during the dome formation and the onset of deformation is dependent on temperature and ramp rate.