Real-time reactive ion etch metrology techniques to enable in situ response surface process characterization

We present a methodology termed in situ design of experiments (ISDOE) which enables rapid response surface design in plasma etch chambers while greatl y reducing test wafer necessity. We experimentally demonstrate the ISDOE pr ocedure on two separate systems using different optical real-time monitorin g techniques to obtain wafer state data on film thickness and etch-rate est imation during reactive ion etch processes. Using the real-time wafer measu rement tools during processing, we quickly obtain input/output (I/O) data t o map plasma inputs to wafer outputs at multiple operating points, thereby reducing the number of test wafers necessary to obtain rich data sets for s tatistical model building and design of experiments. Both measurement techn iques utilize iii situ etch-rate estimations to increase the number of rest set points explored per processed wafer and maximize the parameter space o bserved during each run. Model results and verification using these in situ techniques indicate no loss of accuracy when compared with traditional ex situ measurement methods for response surface design. Though the ISDOE conc ept is demonstrated here specifically on etch rate data, the general idea c an be applied to many other real-time wafer state measurement methods. (C) 2000 The Electrochemical Society. S0013-4651(00)01-046-6. All rights reserv ed.