An Improved ICP Etching for Mesa-Terminated 4H-SiC p-i-n Diodes

Optimization of Mesa Etch for a Quasi-Vertical GaN Schottky Barrier Diode (SBD) by Inductively Coupled Plasma (ICP) and Device Characteristics

“…Secondly, the steep profile of the mesa sidewall allows for reduction of the distance between the anode and cathode electrodes, resulting in a reduction of the series resistance of the Schottky barrier diode (SBD). Therefore, the formation of highly anisotropic profiles of the mesa structure in the etching process is crucial for quasi-vertical GaN devices [6]. Most efforts on the reduction of surface damage and roughness of mesas [7] have been made using inductively coupled plasma (ICP) power, radio frequency 2 of 13 (RF) power, the ratio of etching gas, flow rate [8][9][10][11], and mask selection [12].…”

Dry Etching of High Aspect Ratio 4H-SiC Microstructures

“…25,29 The formation of microtrenches has been attributed to various process parameters working in concert 22,36,37 and can lead to undesired localized electric fields and premature breakdown in SiC. 38 These microtrenches can also converge to form trenches with "W" shaped bottoms, and eventually "V" shaped bottoms with longer etch times. 23 The formation of "V" shaped bottoms prevents etching of trenches with equidistant sidewalls, resulting in trench opening as a function of etch depth.…”

“…23 The formation of "V" shaped bottoms prevents etching of trenches with equidistant sidewalls, resulting in trench opening as a function of etch depth. The importance of minimal microtrench formation can be summarized through the efforts made to eliminate them in SiC etching via Bosch-like etching, 38 thermal chlorine treatment, 27 hydrogen bromide chemistry, 39 and the adjustment of electrode gap 26 as well as other process parameters. [19][20][21] In this work, no post-etch treatment was used to eliminate microtrench.…”

Deep reactive ion etching of 4H-SiC via cyclic SF6/O2 segments

“…The more vertical sidewall is likely due to reduced etch rate, alongside consumption of carbon-rich layer with increased oxygen content [13,14]. For power devices, the rounder trench bottoms are preferred to prevent premature electrical breakdown in SiC [20].…”

“…An anti-Bosch process for SiC etching replaces the passivation step in traditional Bosch with a step that targets the carbon-rich layer formed during SiC etching [13,14]. The combination of the carbon-rich layer and fluorinated residue accumulation of the sidewall is known to affect etch profile [20], and some accumulation is needed to passivate the sidewalls to promote anisotropic etching. The anti-Bosch process is expected to etch carbon-rich areas, thus reducing sidewall accumulation, while maintaining sufficient fluorinated sidewall passivation for vertical sidewalls.…”