FTIR Analysis of Plasma Damage of Kapton

Recently, Kapton (polyimide) has been used in the reduction of dust particles in plasma etching chambers. However, it is found that there is a limit of lifetime for Kapton in trapping particles. Beyond this time limit, particle contamination becomes serious and even causes defect on wafers. In this study, two plasma etching recipes were used to test the particle/polymer trapping efficiency of Kapton. A Fourier Transform Infrared (FTIR) spectrometer was used to examine the functional groups change of the Kapton surface after plasma etching. The increase of IR absorption of CF_x (x = 2, 3) indicates the growth of fluorocarbon polymer on the Kapton surface. The Kapton surface was damaged as indicated by the change of C=O, -NH₂, and C - H IR intensities. IR Spectroscopic data show that Kapton has a very good particle/polymer reduction efficiency when using high-polymer recipe but not very efficient with oxygen-rich recipe. It has drawn our attention that when testing metal contamination of the processed wafers using chambers with Kapton coating, the concentration of aluminum was always high as compared to those without using Kapton. It can be ascribed to the plasma damage of Kapton, as supported by the surface chemical analysis with energy dispersion spectroscopy (EDS). Data collected from FTIR and EDS are correlated to interpret the mechanisms of plasma damage of Kapton.