Etch profile control of high-aspect ratio deep submicrometer /spl alpha/-Si gate etch

The well-acknowledged etch profile drift problem in chip production was investigated with a more accurate meads of measuring actual etch thickness to monitor and correct this drift. Using a high-aspect ratio, 0.1-/spl mu/m /spl alpha/-Si 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 /spl alpha/-Si which was achieved through the development of a method employing a Kalman-Bucy filter 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. Application of this endpoint detection technique to the etch of a 0.1-/spl mu/m patterned /spl alpha/-Si gate also achieved a significant improvement on the etch profile repeatability.