Enhancement of deep-UV patterning integrity and process control using antireflective coating

摘要

Abstract: In this paper, we describe the results of experiments performed using wafers having either phosphorous (POCl$-3$/) doped polysilicon, LPCVD silicon nitride, LPCVD silicon dioxide, LPCVD silicon dioxide over POCl$-3$/ doped polysilicon, evaporated aluminum, or CVD tungsten thin films, patterned with and without the use of deep UV anti-reflective coatings. The parameters of reflectance control, critical dimension control, focus/exposure latitude, and resist profiles were studied for line/space gratings and contacts. Incorporation of anti-reflective coatings was shown to be very beneficial for reducing the impact of highly reflective substrates, grainy surfaces, and topographical features encountered during deep UV imaging. The ARC process is independent of the substrate's reflectivity, allowing the same exposure dose for all substrates studied. Without ARC the optimum exposure dose for the same substrates varied over a 35% range. ARC also provides slightly increased exposure and focus windows for some substrates, and was shown to significantly improve linewidth control on rough substrates such as POCl$-3$/ doped polysilicon and tungsten. The grainy surface of the tungsten wafers was nearly impossible to pattern without the use of an anti-reflective coating; without ARC, there was virtually no process window (approximately 2 mJ/cm$+2$/) for retention of 0.50 $mu@m features. !6