Growth Mechanism and 2D Aluminum Dopant Distribution of Embedded Trench 4H-SiC Region

Abstract

The migration enhanced embedded epitaxy (ME3) mechanism and 2D dopant distribution of the embedded trench region is investigated with the aim to realize the all-epitaxial, normally-off junction field effect transistor (JFET). We found that the embedded growth consists of two main components. First one is the direct supply without gas scattering and the other one is the surface migration supply via the trench opening edge, which dominate the ME3 process. An inhomogeneous 2D distribution of Aluminum (Al) concentration was revealed for the first time in the 4H-SiC embedded trench regions by the combined analysis of secondary ion mass spectrometry (SIMS) and scanning spreading resistance microscopy (SSRM) results. The maximum variation of Al concentration in the trench is estimated to be about 4-times, which suggests that the Al concentration is highest for the (0001) plane and lowest for the trench corner (1-10x) plane. Al concentration in the (1-100) plane, which determines the JFET p-gate doping level is 1.5-times lower than (0001) plane for trench region fabricated on Si-face wafers.

Design, process, and performance of all‐epitaxial normally‐off SiC JFETs

“…The Al concentration in the (1 100) plane (A region), which determines the top gate doping concentration, is 1.5-times lower than in the (0001) plane for Si-face wafers. The contrary is observed for Cface wafers, where the Al concentration is higher at the trench corner [33]. For the n-type doping, the channel trench corner of Si-face and C-face wafers indicate the opposite doping trends.…”

“…Article trometry (SIMS) and scanning spreading resistance microscopy (SSRM) it was found that the Al concentration in the embedded p-region is inhomogeneous with a maximum variation of about 4-times [33]. It was suggested that the Al concentration is highest for the (0001) plane and lowest for the trench corner corresponding to the (1 10 ) x plane.…”

1950°C Post Implantation Annealing of Al+Implanted 4H-SiC: Relevance of the Annealing Time

“…Such a technology is the embedded epitaxial growth. 6 Anyway, the cost of this technology and the difficulty of its control are so high that embedded epitaxial growth is limited to the fabrication of device channel regions while for the device termination regions or for the test of new doping profiles, ion implantation remains the preferred technology.…”

Filling 4H-SiC trench towards selective epitaxial growth by adding HCl to CVD process

“…Moreover, the shape factor, which tends to fill narrow trenches by enhancing the migration of arriving species toward the trench bottom, [9][10][11] produces an additional decrease in the reactant species remaining on the mesa top with increasing P, 14) as shown in the reference data plotted in Fig. 3(b).…”

“…7) Therefore, trench filling by epitaxially filling doped SiC into trenches of the opposite conductivity type is considered the preferable method for constructing SiC-SJ structures. [8][9][10][11][12][13][14] In previous literature, 4H-SiC trenches with depths of up to 7 µm and aspect ratios of about 2-4 have been completely or half-filled by using hot-wall chemical vapor deposition (HWCVD) with a conventional gas system, SiH 4 : C 3 H 8 : H 2 . [8][9][10][11][12][13] However, Schöner et al mentioned the necessity of maintaining a slow growth rate and long duration of trench filling to minimize excessive growth outside of the trenches.…”