Overcome the challenge of CD-bias with organic bottom anti-reflective coating removal process

This paper presents a review of two bottom anti-reflective coating (BARC) removal processes incorporated into subhalfmicron contact etching. They are believed to represent different etching mechanisms. Accuracy of size feature transfer was taken as a primary criterion for comparison of different BARC removal processes. These processes are based on application of glow discharge in the following basic gas mixtures: CF4+O2 and CO+O2. The first process based on CF4+O2 gas mixture shows a behavior of neutral etching species model that cause a footing developing during BARC removal. Roughly this may be explained by the continuous direction spectrum of neutral active species movement. The access of active neutral species to the BARC layer is dependant upon the window mask size, resist profile and the thickness of resist layer. The second process based on CO+O2 gas mixture represents another etching mechanism − ion bombardment induced etching. On contrary to the previous partially isotropic process this one provides anisotropic etching. This is due to stimulating and activating the etching reaction by ion bombardment. Anisotropic features are achieved because of directional ion flux normally to wafer surface. This process is proved to be independent of profile and mask opening size features. Data presented show that process based on CO+O2 gas mixture provides consistent close to zero CD bias at BARC removal step while CF4+O2 gas mixture based process causes negative CD bias with apparent dependence upon the window mask size. Robust results of CO+O2 process allow one to consider it and its basic etching mechanism to be a mainstream of process development for different applications.