Alexander V. Suvorov

Diffusion of boron in 6H and 4H SiC coimplanted with boron and nitrogen ions

The diffusion behavior of boron (B) and nitrogen (N) implanted in 6H and 4H silicon carbide (SiC) samples was investigated using secondary ion mass spectroscopy. The samples were either coimplanted with B and N ions or implanted with each element alone. The annealing was performed at 1700°C for times ranging from 10to1800s in argon ambient or in the vapors of silicon and carbon. Transmission electron microscopy has been used to determine the structural properties of implanted layers after the annealing. The N concentration profiles remained unchanged after the annealing. B atoms showed transient enhanced out- and in-diffusion. The coimplantation reduced the fraction of mobile B atoms participating in out- and in-diffusion processes and resulted in an increase in the density and decrease in size of dislocation loops formed in the implanted layer. The B diffusion coefficients in both SiC polytypes have been determined and a diffusion mechanism has been discussed.

SiC symmetric blocking terminations using orthogonal positive bevel termination and Junction Termination Extension

Symmetric blocking power semiconductor switches require two edge terminations, one for the reverse blocking junction and the other one for the forward blocking junction. In this work, we demonstrated 1100V SiC symmetric blocking edge terminations using orthogonal positive bevel (OPB) termination and a one-zone Junction Termination Extension (JTE). The OPB was formed by orthogonally sawing 45° V-shape trenches into the SiC wafer with a diamond-coated dicing blade. The surface damage was then repaired with dry-etch in SF6/O2 plasma, which reduced the leakage current by around two orders of magnitude. As limited by field reach-through, both the OPB and the JTE terminations show breakdown voltage of 1100V. The P+P-N+ diodes fabricated on the same wafer with the OPB termination showed 1610V avalanche breakdown which was around 83% of ideal value.

Effect of Implantation Temperature on Redistribution of Al in SiC during Annealing

Diffusion of aluminum in 6H-SiC during high temperature annealing was studied. Al atoms were introduced by ion implantation at various substrate temperatures. It has been shown that redistribution of Al atoms during the following annealing correlated with the amount and nature of residual damage created by ion bombardment.

High-Performance Implanted-Channel SiC MESFETs

We demonstrate for the first time the development of state-of-the-art ion-implanted-channel SiC MESFETs with record dc and RF performance that is comparable to that of epitaxial-channel devices. MESFETs fabricated with this approach show a maximum stable gain exceeding 15.8 dB at 3.1 GHz in class-AB bias condition. An RF power output that is greater than 4 W/mm, with 63% drain efficiency, at 3.5 GHz was also achieved, showing the potential of these devices for high-power operation.

Aluminum Ion Implantation in Silicon Carbide at High Temperature of Target

Single crystals and epitaxial films of SiC - 4H and 6H were implanted at an energy of 40 and 90 KeV by ions of Al at various temperatures and high dose. The implanted layers were studied before and after annealing by Raman scattering, Auger electron spectroscopy and SIMS. Results of this investigation show intensive graphitization of the implanted layer surface, the formation of great associations of defects in the implanted layer and shallow defects. It was found that recrystallization of the implanted layer pushes out a considerable part of aluminum atoms. The nature of the processes in silicon carbide during implantation and annealing is discussed.