GaAs/AlGaAs - Dry Etching

GaAs/AlGaAs - Dry Etching

Material Name: GaAs/AlGaAs
Recipe No.: 8506
Primary Chemical Element in Material: Ga, Al
Sample Type: Thin film
Uses: Etching
Etchant Name: None
Etching Method: Dry etching
Etchant (Electrolyte) Composition: A Plasma-Therm SLR 770 inductively coupled plasma etcher was utilized for selective etching of GaAs over AlGaAs layer. The etcher has He back-side cooling configuration and a mechanical ceramic clamp on the wafer. Bulk GaAs and 3000 Å of AlGaAs epi-layer with 20 % Al composition were prepared on GaAs wafers. One micron thick photoresist on top of 400 Å SiNx was patterned as a mask for etching of GaAs and AlGaAs. Each of the 4” GaAs and AlGaAs wafers was cleaved into a quarter and attached next to each other on a 4” bare GaAs carrier with a thermally conductive paste. A short breakthrough etching step was done before selective etching started in order to remove any native oxide on the materials. Gas flow of BCl3, SF6, He and N2 was controlled by electronic mass flow controllers. Total gas flow rate was kept at 20 standard cubic centimeter per minute (sccm) and pressure was at 5 mTorr. A 2 MHz ICP source power and 13.56 MHz rf chuck power was maintained at 300 W and 10 W, respectively. Self-induced dc bias on the electrode was measured to be about ~ - 45 V. Etch depth, sidewall and surface morphology was measured by a profilometer and a scanning electron microscope (SEM), respectively. In order to have accurate calculation for selectivity with a simulation of extremely long over-etching time for AlGaAs layer, all the characterization data was obtained after 15 min. etching, which made a few micron of etched GaAs feature. It is common to have short over-etching time (less than 10 %) in order to ensure complete removal of GaAs and full exposure of AlGaAs surface.
Procedure (Condition): No data
Note: No data
Reference: J. W. Lee, M. Devre, B. Reelfs, D. Johnson and J. N. Sasserath, S. J. Pearton, Significant enhancement of selectivity and anisotropy for high rate plasma etching of GaAs over AlGaAs for heterojunction bipolar transistor structure, http://www.plasma-therm.com, 2020, pp. 1-10.