Systematic Study of Anodic Etching of Highly Doped N-type 4H-SiC in Various HF Based Electrolytes

Abstract

In this paper, we study the electrochemical anodization of n-type heavily doped 4H-SiC wafers in HF based electrolytes without any UV light assistance. We present, in particular, the differences observed when varying the process conditions such as the HF concentration, the type of additive and the applied current regime. The use of a solvent such as acetic acid seems to be more suitable to produce homogeneous morphologies compared with Cetyltrimethylammonium chloride (CTAC), Ammonium dodecylsulfate (ADS), Triton X-100 surfactants. In addition, the use of pulsed current regimes improves the global homogeneity of the porous layers. Nevertheless, for some unexplained reasons, at specific concentrations of 15 and 50%, this homogeneity cannot be ensured and the observed morphology mixes mesopores and macropores with random orientations.

Influence of the anodic etching current density on the morphology of the porous SiC layer

“…The SiC etching mechanism proposed by Shor and Kurtz 16 has been generally accepted. 13,[17][18][19][20][21][22][23] According to their hypothesis, anodic etching of SiC in aqueous HF occurs in two steps: oxidation of SiC and dissolution of the formed oxide. They suggested that oxidation of SiC occurs via the following reactions: 16 SiC…”

Silicon carbide X-ray beam position monitors for synchrotron applications

“…Electrochemical etching (ECE) is an oxidation/oxide removal process obtained by dipping silicon carbide samples in an HF solution and electrically supplying holes for the oxidation through the back metal contact (Dahal et al, 2017;Watanabe et al, 2011;Gautier et al, 2012Gautier et al, , 2013. The process is capable of removing highly doped (!1 Â 10 18 cm À3 ) p-type and n-type layers but is selective towards low-doped n-type layers (selectivity !…”

Investigation of the Young’s Modulus and the Residual Stress of 4H-SiC Circular Membranes on 4H-SiC Substrates

“…The substrate removal was obtained by electrochemical etching. ECE is an oxidation/oxide-removal process obtained by dipping the SiC wafer in a hydrofluoridric acid-based solution and electrically supply holes for the oxidation through a 100 nm aluminium back metal contact [6,[21][22][23]. The process is capable of removing highly doped (≥ 10 18 cm −3 ) p-type and n-type layers but is selective towards low-doped n-type layers (selectivity > 1000:1 with respect to the 5 × 10 13 cm −3 doped n − layer).…”