Ekkehard Niemann

SiC devices for advanced power and high-temperature applications

Silicon carbide (SiC) process technology has made rapid progress, resulting in the realization of very promising electronic devices and sensors, enabling advanced solutions in power industry and mobile systems. In particular, for electronics working under harsh environmental conditions, SiC devices reach unprecedented performance. Transfer to production has already started for some applications.

Efficient p-type doping of 6H-SiC: Flash-lamp annealing after aluminum implantation

Flash-lamp annealing was used for activation and crystal recovery of highly aluminum-implanted 6H-SiC wafers. In comparison with conventional furnace annealing, the free hole concentration can be remarkably increased at high acceptor atom concentrations (⩾5×1020 cm−3). The lowest resistivity measured at room temperature was 0.01 Ω cm. In this case, the layers are characterized by metallic conduction with weak dependence of the hole concentration on the temperature. This effect is caused by freezing-in of the enhanced solubility of aluminum in SiC at the extraordinary high temperature of about 2000 °C during the light-flash.

CVD growth of 3C-SiC on SOI (100) substrates with optimized interface structure

Abstract In this paper we have investigated the CVD growth of 3C-SiC on SOI (100) substrates at reduced temperatures employing a carbonization step with a slow temperature heating-ramp. The carbonization leads to a rapid sealing of the Si-top layer of the SOI substrate due to a high SiC nucleation density totally avoiding the commonly reported formation of cavities at the 3C-SiC/Si interface. From TEM investigations it can be shown that the crystallinity of the 3C-SiC is comparable to state-of-the-art SiC thin films on Si. Exploiting this growth process 5 μm thick 3C-SiC layers on Si (100) show excellent crystal quality with a FWHM=0.18° derived from X-ray ω -rocking curves. This is confirmed by electrical characterization using Hall measurements.

Electrical characterization of 6H-SiC enhancement-mode MOSFETs at high temperatures

Linear, small-signal enhancement-mode MOSFETs are fabricated in p-type 6H-SiC. Ion implantation of nitrogen and aluminum are used to form the n + -regions for the source/drain contacts and the channel-stop, respectively. Direct current measurements were performed up to 673 K, revealing a drain-to-source saturation current I DSS of 1.53 mA mm -1 at V DS = + 10 V and V GS = + 9 V, a transconductance in saturation of 0.56 mS mm -1 at V GS = + 9 V and a subthreshold slope of 170 mV per decade at room temperature. The excellent high temperature behavior is demonstrated by an I ON /I Off ratio of 10 5 at 673 K (10 8 at 303 K) and low leakage currents (< 10 pA) below threshold up to 523 K. The inversion layer mobility of the electrons μ n is 40 cm 2 V -1 s -1 at room temperature, having a thermally activated region up to 423 K with maximum of 44 cm 2 V -1 s -1 before decreasing by phonon scattering.