RF process monitoring--who needs it?

Whether you are manufacturing radio frequency integrated circuits (RFIC) for cell phone modules on III-V wafers or digital signal processors (DSP) on silicon-based technology, predicting final product performance and reliability requires s-parameter measurements at the wafer level to complement direct current (DC) data. The use of radio frequency (RF) parameters for modeling and DC data for production monitoring was a working paradigm until product performance reached the gigahertz range. Now, process control for gigahertz devices requires RF parameter sampling to meet various objectives. Although the RF test methodology is well established, actual implementation is complicated and may require a practitioner with a doctorate to obtain accurate calibrations.