Patent ID: 6650426
Filing Date: 2003-11-18
Classification: H01J,H01L

Abstract:
A method for plasma etching a shallow recess at a predetermined final depth of less than approximately 0.67 &mgr;m, or 15-20 or more times shallower than 10 &mgr;m deep trenches, and a width of less than approximately 0.5 &mgr;m by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of:determining an etch start time based on at least one of a plasma ignition time, a detection of a beginning of a wafer reflectance change, and a time after plasma ignition determined by observing a change of reflectance intensity in the data indicating that a breakthrough step of etching a residual oxide layer has been completed; measuring reflectance intensities of light reflected from the wafer a number of times during said etching of said recess; calculating an etch rate from data of the measured reflectance intensities; calculating an etch stop time based on the etch start time, the etch rate, and the predetermined final recess depth; and triggering an endpoint such that etching is stopped approximately at the determined etch stop time, said shallow recess being etched at approximately the predetermined final recess depth within a specified tolerance of substantially 6%.