Low sidewall damage plasma etching using ICP-RIE with HBr chemistry of Si/SiGe resonant interband tunnel diodes

The effect and influence of dry plasma etching processes of Si/SiGe using HBr for the formation of diode mesa structures has been investigated to minimise sidewall leakage current. To characterise sidewall damage electrically, Si-based resonant interband tunnel diodes (RITD) were processed and the completed RITDs compared by their peak-to-valley current ratio (PVCR) and valley current density (VCD), which are sensitive to defect related currents. Dry processed RITDs were compared to reference RITDs fabricated by wet chemical etching (HNO₃:HF:H₂O=100:1:100). The combination of HBr process gas and very low substrate bias power (10 W) for inductively coupled plasma reactive ion etching (ICP-RIE) yielded the better results. The resulting RITDs processed by ICP-RIE using HBr chemistry show high PVCR of 4.02 with VCD of 32 A/cm² while wet etched RITDs show a PVCR of only 2.81 with VCD of 40 A/cm². Hydrogen passivation during the HBr plasma process may play a role that overcomes the slightly higher surface roughness compared to wet etching.