Oliver Humbel

Ion implantation challenges for power devices

Ion Implantation processes contribute significantly to the development of power devices. In this case not smallest scale technologies are addressed, but accurate treatment of the frontside, backside and bulk material play a crucial role to guarantee for key parameters such as highest power densities and required switching behavior. Some representative examples of the development needs of high, medium and low power switching devices based on silicon technology are described and challenges for ion implantation processing are concluded.

Experimental Study of a 6.5kV MOS Controllable Freewheeling Diode

A 6.5 kV controllable freewheeling diode (CFD) has been realized for the first time. A forward voltage V_F up to 2.5 V (66 A/cm²) and a V_F rising over 1.8 V between gate off state and gate on state at 125degC temperature was realized. A reduction of the recovery charge Q_rr and consequently reverse recovery energy E_rec of more than 35% have been achieved in comparison with a state of the art 6.5 kV emitter controlled diode.

Identification of deep trap energies and influences of oxygen plasma ashing on semiconductor carrier lifetime

We have performed an analytical study of the effects of oxygen plasma ashing processes in semiconductor device fabrication and its impact on minority carrier lifetime in high voltage semiconductor devices. Our work includes a critical background study of life time killing mechanisms by deep traps imparted into the semiconductor by barrel plasma ashing. The Elymat technique provides the opportunity to measure lifetime and diffusion length of minority carriers and surface photo voltage (SPV) measurement was used to analyse influences of process parameters such as photoresist, time budget and positioning in the process chamber. It was shown that in microwave plasma processes the diffusion length changes severely with tempering at 200 ?C, whereas RF-plasma processes show a significant process time-dependence. Batch tools in general suffer from a strong first wafer effect which could be correlated with the static electrical parameters of the semiconductor devices. The trap identities were detected by using deep level transient spectroscopy and the chemical species of the traps has been proven by inductive coupled plasma mass spectrometry. The deep-bandgap trap energies are reliable fingerprints of the chosen process parameters such as process time and of resist-influences. By microwave plasma processes intrinsic Fe and FeB-complex levels were identified and a good agreement with the SPV-measurement and electrical device characteristic was shown. RF-plasma processes impart levels attributed to Pt levels and an additional level, which could be identified as a trap level probably forming a complex of Pt and H.