Selective Doping in Silicon Carbide Power Devices

Abstract

Silicon carbide (SiC) is the most mature wide band-gap semiconductor and is currently employed for the fabrication of high-efficiency power electronic devices, such as diodes and transistors. In this context, selective doping is one of the key processes needed for the fabrication of these devices. This paper concisely reviews the main selective doping techniques for SiC power devices technology. In particular, due to the low diffusivity of the main impurities in SiC, ion implantation is the method of choice to achieve selective doping of the material. Hence, most of this work is dedicated to illustrating the main features of n-type and p-type ion-implantation doping of SiC and discussing the related issues. As an example, one of the main features of implantation doping is the need for post-implantation annealing processes at high temperatures (above 1500 °C) for electrical activation, thus having a notable morphological and structural impact on the material and, hence, on some device parameters. In this respect, some specific examples elucidating the relevant implications on devices’ performances are reported in the paper. Finally, a short overview of recently developed non-conventional doping and annealing techniques is also provided, although these techniques are still far from being applied in large-scale devices’ manufacturing.

Defect- and H-Free Stoichiometric Silicon Carbide by Thermal CVD from the Single Source Precursor Trisilacyclohexane

“…SiC films also serve as the host matrix in three exciting new areas of technical innovation. In power electronics, SiC enables the fabrication of high-voltage, high-current devices that can be operated at elevated temperatures [6][7][8]; SiC is also increasingly used in micro-electro-mechanical-systems (MEMS) due to its higher thermal conductivity, higher voltage power, and higher breakdown voltage compared to Si [3]; In nanophotonics, quantum and nonlinear photonics technologies exploit a wide array of SiC properties, including high refractive index, strong second-and third-order optical nonlinearity, and a broad ultra-violet-to-mid-infrared transparency window [9][10][11][12]. For these reasons, SiC also acts as a base platform for a number of optically addressable spin qubits [13].…”

Facet-dependent electrical conductivity properties of a 4H-SiC wafer

“…32,33 Selective doping techniques for SiC power devices have been reviewed. 34 Here the photoluminescence spectra of the front and side faces of an intrinsic 4H-SiC wafer were measured first. Conductivity measurements of different surfaces using tungsten probes were performed to reveal a large facet effect.…”

Effects of Excimer Laser Irradiation on the Morphological, Structural, and Electrical Properties of Aluminum-Implanted Silicon Carbide (4H-SiC)

“…Due to the low diffusivity of the dopant species in the material, the ion-implantation technique is the consolidated method for selective doping in 4H-SiC power electronics devices, such as junction barrier Schottky (JBS) diodes or MOSFETs. , Nonetheless, the ion-implantation process inevitably leads to the production of lattice damage or even amorphization of the material . Hence, postimplantation thermal annealing treatments are conventionally performed in furnaces at high temperature (>1600 °C), to partially recover the crystalline structure of the semiconductor and achieve the electrical activation of the dopant species, bringing them in substitutional lattice sites . However, the electrical activation of the dopant species is limited by both their solid solubility and the attainable annealing temperature in conventional high temperature furnaces.…”

“…8 Hence, postimplantation thermal annealing treatments are conventionally performed in furnaces at high temperature (>1600 °C), 9 to partially recover the crystalline structure of the semiconductor 10 and achieve the electrical activation of the dopant species, bringing them in substitutional lattice sites. 7 However, the electrical activation of the dopant species is limited by both their solid solubility and the attainable annealing temperature in conventional high temperature furnaces. Moreover, standard thermal annealing treatments at high temperatures can generate both point and extended defects, which are, in turn, detrimental for the electrical activation of the dopant.…”