Profile control in high aspect ratio contact hole etching by a capacitively coupled plasma source

Two types of masking methodologies for high aspect ratio deep contact hole etching, photo-resist (PR) masks only and poly-silicon hard masks (poly-HM), have been applied and studied. In order to understand the variation of plasma chemistries, the optical emission spectroscopy has been used to characterize the reactions of plasma etching. A novel technique for bowing-free 0.1-μm deep contact hole etching using either PR or poly-HM has been developed. It has been demonstrated that a straight vertical profile of deep contact hole can be obtained by controlling two process factors: polymer deposition rates and ion extraction energy. The step-by-step control of top and bottom powers in the capacitively coupled plasma has been found to be an effective method to avoid profile bowing and tapering in the etching process. The deep contact holes with aspect ratio >30 and profile angle of 89.8° have been obtained.