Etch profile control of high-aspect ratio deep submicrometer alpha-Si gateetch

The well-acknowledged etch profile drift problem in chip production was inv estigated with a more accurate means of measuring actual etch thickness to monitor and correct this drift. Using a high-aspect ratio, 0.1-mum alpha -S i gate structure, the investigation was specifically focused on the control of transition timing in the critical interval from main etch (ME) to over etch (OE). This required reliable endpoint detection of alpha -Si which was achieved through the development of a method employing a Kalman-Bucy filte r with a real-time spectroscopic ellipsometer (RTSE). The robustness of our endpoint detection technique was tested and demonstrated under the actual physical and chemical disturbance environments of the etching process. Appl ication of this endpoint detection technique to the etch of a 0.1-mum patte rned alpha -Si gate also achieved a significant improvement on the etch pro file repeatability.