Thomas Gutt

Laser Thermal Annealing for Power Field Effect Transistor by using Deep Melt Activation

For chips with vertical flow of electrical current, an ohmic contact and/or emitter on the backside of the wafer are required. The formation of this electrical contact can be done using a laser annealing method in overlapping mode. Test on bare wafers and on productive chips were carried out using an excimer laser (lambda = 308 nm) with a laser energy density of more than 2 J/cm2 and a laser pulse duration of 180ns. Owing to the long pulse duration, deep melt activation with a molten zone with up to 400nm could be reached and an efficient emitter could be achieved

6.5kV RCDC: For increased power density in IGBT-modules

A reverse conducting IGBT in trench technology is presented. By this approach no carrier life time means are necessary to balance static and dynamic losses of the diode. The diodes p-emitter efficiency can be dynamically tailored by the applied gate voltage due to inversion charge carriers in the vicinity of the gate trench. This opens up the opportunity for a variety of gate control schemes with the aim of a charge carrier reduction before commutation thus reducing the recovery and the corresponding IGBT turn-on losses while the on-state diode losses remain low. A simple substitution of the IGBT and diode dies by the RCDC chips in the industry standard packages enables a significant increase of the power density (e.g. up to 30% for typical traction application) due to a thermal benefit given by lower thermal resistances as well as by a reduction of the dynamic losses due to special gate control.

Wet rapid thermal oxidation of vertical cavity surface emitting laser structures with pyrogenic steam generator

In this article, the successful application of rapid thermal oxidation (RTO) with steam ambient for the selective oxidation of high aluminum containing embedded AlGaAs layer for the formation of current aperture in VCSELs is reported. The steam generation is achieved by the pyrogenic steam generation approach in which hydrogen and oxygen gas mixture is converted into steam by autoignition. Comparing to conventional furnace oxidation, steam-RTO showed a 6 times higher oxidation rate and an excellent oxidation uniformity across 4 inch wafers. It was also observed that after steam-RTO the Cr/Pt/Au p-type contacts had a 50% reduction in specific contact resistance compared to those oxidized in a conventional furnace