(Invited) P-Type and N-Type Channeling Ion Implantation of SiC and Implications for Device Design and Fabrication

Abstract

Silicon Carbide is rapidly growing in the power electronics industry. It is fueled by several robust long-term growth markets like renewables, cloud computing and electric vehicles. There is a wide release and proliferation of Diode and MOSFET devices from various companies in the marketplace. There is a continuous push in subsequent generations to improve device performance, reliability and efficiency. Some of the advanced design concepts in Silicon like super-junction technology have significant manufacturing roadblocks like diffusion, epi regrowth and implantation. In this work, we present results of both p-type and n-type channeled implants into 4º offcut N-type SiC substrates and Epitaxial layers using a Nissin Ion Equipment IMPHEAT system. Deep-channeled implants can be considered an enabling technology for the fabrication of advanced device designs including super-junction structures.The use of channeled implants have been reported on on-axis [1] SiC and 4º offcut using primarily low energies [2,3]. One major concern while trying to check the feasibility of channeling and implement it in mass-production is the reliability and variation of the off-cut angle. Fig. 1 shows the off-cut angle reported by the substrate vendor and the actual offcut angle as measured by X-ray diffraction. The actual off-cut variation is comparatively low. However, per wafer inline XRD measurements might be needed for accurate channeling. Fig. 2 shows how a 960kev 1e13cm-2 dose channeled implant changes the wafer shape. This change in shape is consistent with other high temperature treatments like Epi growth. Fig. 3 shows the room temperature channeled and non-channeled implant of triple charged Aluminum at 960 keV with a dose of 1e13cm-2. The offcut angle as measured by XRD of 4.1º gives the maximum range. The implant is also not very sensitive to off-cut disorientation. Fig. 4 shows the channeled implants as a function of implantation temperature. As expected, the range is reduced and thereby restricts very high doses. Fig. 5 shows similar channeled and non-channeled implantation of Boron and Phosphorous. The phosphorous profiles are flat and can be effectively used for n-type doping. A comprehensive review of effects of dose and orientation on the channeled profiles will be presented. Channeled implanted wafers were activated and the activation measured by fabricating Metal Schottky contacts. The effect of high and low warp wafers on channeled implant profiles are also discussed. Further implants at different energies are obtained and combined to get box-like profiles. The error in off-cut degree that can be tolerated for channeled implants in mass-production is estimated for different energies. Implications to super-junction device fabrication is discussed.