By Carl Scharrer, Keithley Instruments, Inc.
Whether you are manufacturing RFICs for cell phone modules on III-V wafers
or DSPs on a silicon-based technology, predicting final product performance
and reliability requires s-parameter measurements at the wafer level to
complement the DC data. This is only practical when calibration and deembedding
of the s-parameters is automated, along with probe cleaning.
Cost of consumables and overall cost of test must also be comparable to the
traditional DC process monitor operation. The ideal case is to have a single
test operation collect the DC and s-parameter data.
RF Process Monitoring – Who Needs It?
Almost without exception, semiconductor device manufacturers use
DC data for statistical process control of their manufacturing operations. They
have traditionally taken s-parameter data only in device modeling laboratories
due to the complex nature of the measurements and associated cost. RF
parameters are extracted from the s-parameter data and included in the
simulation models used by design engineers during product development. RF
parameters for modeling and DC data for production was a working paradigm
until product performance approached the gigahertz range. Process control for
gigahertz devices requires RF parameter sampling to meet the Known Good
Die goals of RFICs for cell phone modules, guarantee the frequency
performance of DSP chip level interconnect, and monitor gate dielectrics with
complex material properties. As device performance improves to meet the
demands of the wireless market, component manufacturers are struggling to
improve test coverage without unacceptable increases in test cost. Several leading manufacturers have attempted to migrate the RF parametric measurement capability from their device modeling labs to manufacturing operations with little success and high levels of frustration.
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White Paper: Statistical Process Control Of Wireless Device Manufacturing Requires Production Worthy S-Parameter Measurements