High Voltage P-N Junction Diodes in Silicon Carbide Using Field Plate Edge Termination
- PDF / 971,083 Bytes
- 6 Pages / 417.6 x 639 pts Page_size
- 92 Downloads / 248 Views
high thermal conductivity. However, its widespread application has been limited due to the fact that the device fabrication technology for SiC is still in its stage of infancy. Due to low impurity diffusion coefficients, doping in SiC is usually obtained either by epitaxial growth or by ion implantation. The former is not attractive because it requires mesa etching for edge termination, and hence the device topology becomes non-planar making passivation difficult. Hence, in order to improve the commercial viability of SiC devices, the successful development of planar ion implantation technology for SiC for microelectronic technology is of major importance. Dopant activation, surface morphology control and ohmic contacts have been the major obstacles in the development of a reproducible ion implantation technology. Until recently, P-N junctions in SiC have been formed using multiple epitaxial layers or unmasked ion implantation. However, these approaches compromise on surface planarity and are not preferred [1-3]. Although there have been quite a few reports on ion implantation, 6H-SiC has received most of the attention [2-6]. In most cases, the dopants used have been nitrogen, aluminum and boron. There have been only a couple of reports on other dopants like phosphorous and beryllium [7,8] where breakdown voltages of 675 V were reported for phosphorous implanted non-planar junctions. The diodes fabricated in the above work have been mesa-etch terminated which are not compatible with IC technology. Various planar edge terminations such as floating metal rings and resistive Schottky barrier field plates have been explored for 6H-SiC devices [9] but only 50% of ideal breakdown voltage was achieved. A planar, near ideal, edge termination 81 Mat. Res. Soc. Symp. Proc. Vol. 572 © 1999 Materials Research Society
using Argon implantation [10,11] has been reported for 6H-SiC Schottky barrier diodes but the leakage current is greatly increased by the implanted region. This method was also demonstrated for 4H-SiC with breakdown voltages exceeding those reported for 4H-SiC mesa-etch terminated diodes [12]. Most recently, a 3.4 kV ion implanted PIN-rectifier has been implemented on 4HSiC with low leakage currents obtained by using junction termination extension created by boron ion implantation [13]. In this paper, reverse blocking characteristics of diodes made using phosphorous, nitrogen, aluminum and boron implanted layers and having different edge terminations are discussed. EXPERIMENT The starting wafers were research grade 6H- and 4H-SiC wafers (both n-type and p-type) consisting of a 10 gm thick epitaxial layer (0.85-1.0x10 16 cm 3) on a 300 gim thick substrate (lxlOs8 cm-3), obtained from CREE. Devices were fabricated using two process sequences differing mainly in the dielectric used to mask the implants, the temperature of post implantation anneal and the final dielectric used in device termination. The first fabrication process was a 2-mask process in which the post-implantation anneal was at 1600 'C, which is desi
Data Loading...
