Development of advanced plasma process with an optical emission spectroscopy-based end-point technique for etching of AlGaAs over GaAs in manufacture of heterojunction bipolar transistors

We demonstrated an advanced plasma etching technology for AlGaAs over GaAs in a BCl3/N2 inductively coupled plasma using an optical emission spectroscopy. The process results showed that etch rate of GaAs and AlxGa1−xAs (x=0.2) was equal in the condition, which means that selectivity of AlGaAs over GaAs was 1:1. The process also provided very smooth surface morphology, vertical side wall and residue-free surface. All the results indicated that the process would significantly improve reproducibility and reliability for the plasma process in advanced manufacturing of AlGaAs/GaAs-based semiconductor devices, such as heterojunction bipolar transistors.