A Design of Experiment for High Throughput GaAs Via Etch by Reactive Ion Etch

Juifen Lee, Hungchun Tsai, Yee-Shyi Chang
Materials Science and Engineering, National Tsing-Hua University
Hsin-Chu, Taiwan, ROC

A design of experiment for high throughput GaAs via etch by reactive ion etch is reported.  An effective GaAs backside via process for connecting the front side circuits to the backside ground plane reduces the ground inductance and thus improves the RF performance of Fabricated circuits.  We conducted a Design of Experiment (DOE) for GaAs via etch to obtain high etch rate and smooth via profile with a non-reentrant slope simultaneously on a four mils thick GaAs substrate.  The DOE consisted of four major varying parameters, which were pressure, RF power, BC13/C12 ration, and Ar flow rate.  Dependence of output results, such as GaAs etch rate, photoresist etch rate, etch selectivity between GaAs and photoresist, and cross-section view of via holes, on the four major parameters is discussed.  A smooth via profile with non-reentrant slope was achieved for a GaAs backside process with a combination of multiple etches.



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