Reactive etching of semiconductor surfaces using an electronically chopped low energy broad beam ion source

A tuneable electronic chopper was adapted to the power supply of a common ECR (electron cyclotron resonance) broad beam ion source. The beam switch allows the selection of the frequency and the duty cycle in the range of 50 Hz to 10 kHz and 0.1 to 0.9, respectively. Hence, ion beam pulses with a length of 10 μs to 18 ms can be applied without changing the other beam properties, which was proved by integrated and time-resolved measurements. The pulsed ion beam was utilised for the investigation of the GaAs etching by chlorine. The dynamics of halogen–solid interactions could be studied under real processing conditions by varying the pulse length. In general, the etch rate of GaAs increases with decreasing pulse length at a given pulse frequency as a result of the increased chloride coverage of the surface. The usage of pulsed ion beams from broad beam ion sources is proposed to control and improve the etch profiles, the defect density and the selectivity of reactive etch processes.