Sj. Pearton et al., DRY PROCESSED, THROUGH-WAFER VIA HOLES FOR GAAS POWER DEVICES, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 11(2), 1993, pp. 152-158
The fabrication of through-wafer via holes in GaAs substrates by plasm
a etching and laser drilling is reported. Using a low pressure (15-20
mTorr), low dc bias ( - 150 V) Cl2/BCl3 discharge with Cl2-to-BCl3 rat
ios <0.2, we are able to produce narrow (less-than-or-equal-to 30 mum)
via holes. This enables the use of a higher density of vias in closer
proximity to the active GaAs power devices than can be achieved with
normal diameter (100-150 mum) holes. Microwave enhancement of the plas
ma density using an electron cyclotron resonance source increases the
GaAs vertical and lateral etch rates and requires use of low Cl2-to-BC
l3 ratios in order to retain the anisotropic nature of the vias. Multi
ple pass (approximately 100 per hole) drilling of vias with a Q-switch
ed Nd-YAG frequency doubled (532 nm), 30 mW laser has also successfull
y produced through-wafer connections. This provides a maskless, versat
ile method for producting vias customized for a particular wafer, but
is less developed than plasma etching.