Producing Silicon Carbide Micro and Nanostructures by Plasma‐Free Metal‐Assisted Chemical Etching

Abstract

Silicon carbide (SiC) is a wide bandgap third‐generation semiconductor well suited for harsh environment power electronics, micro and nano electromechanical systems, and emerging quantum technology by serving as hosts for quantum states via defect centers. The chemical inertness of SiC limits viable etching techniques to plasma‐based reactive ion etching methods; however, these could have significant undesirable effects for electronic and photonic devices. This paper presents a plasma‐free, open‐circuit, photo‐induced metal‐assisted chemical etch for fabricating micro and nanoscale features without the inherent high energy ion‐related surface damage. The method presented herein utilizes above bandgap ultraviolet light, patterned noble metal (Pt), and a solution consisting of an oxidant potassium persulfate (K2S2O8) and an acid, hydrofluoric acid, to spatially define the etching morphology. The parameter space is comprehensively explored to demonstrate the controllability and versatility of this technique to produce ordered arrays of micro and nanoscale SiC structures with porous or solid sidewalls, and to elucidate the etching mechanism.

Anisotropic Charge Transport Enabling High‐Throughput and High‐Aspect‐Ratio Wet Etching of Silicon Carbide

“…The case with a Pt top mask and without a Pt bottom coating has a moderate R vertical (0.463 ± 0.012 µm min −1 ) and a moderate R horizontal (0.090 ± 0.006 µm min −1 ). The case with the Pt top mask and bottom coating has the highest R vertical (0.737 ± 0.019 µm min −1 ), which is 248-fold enhanced compared to the previous record of external-bias-free wet etching methods [29] and also 1.3 times higher than the best rate achieved for external-bias-assisted wet etching, [40] as displayed in Table 1. Besides the highest R vertical , this case also reaches the highest R horizontal (0.151 ± 0.015 µm min −1 ), indicating rapid horizontal etching that may limit the aspect-ratio of the etched structure.…”

“…Such design largely suppresses recombination‐induced charge losses, and when used in combination with a Pt catalyst mask, the structure yields a remarkable vertical etching rate of 0.737 µm min −1 , 248‐fold enhanced compared to the previously reported photo‐electrochemical etching rate. [ 29 ] Alternating the catalyst mask with gold (Au), we achieved micro‐structured arrays with aspect ratio up to 3.2. The method can be readily extended to fabricate novel wide bandgap semiconductor structures and devices.…”

“…Externalbias-free wet etching typically relies on photo-electrochemical etching. [27][28][29][30] This method exploits hole carriers generated by ultraviolet (UV) light illumination to oxidize SiC. To achieve ordered micro/nano-structure arrays on SiC, pre-patterned platinum (Pt) was used as the mask catalyst, which selectively shields the UV light while catalyzing the reduction of oxidants in the etchant to provide holes for the unshielded SiC.…”

“…To achieve ordered micro/nano-structure arrays on SiC, pre-patterned platinum (Pt) was used as the mask catalyst, which selectively shields the UV light while catalyzing the reduction of oxidants in the etchant to provide holes for the unshielded SiC. [29,31] However, this method still yield low etching rate (<2.97 nm min −1 ) and aspect ratio (<1.67).…”

Surface and Subsurface Quality Assessment of Polished Lu2O3 Single Crystal Using Quasi-Brewster Angle Technique

“…Conventional surface inspection methods, such as optical profilometer, atomic force microscope (AFM), and scanning tunneling microscope (STM), are sufficient for surface quality testing needs [10][11][12][13]. Since subsurface damage is overlapped by the sample surface, high precision assessment of subsurface damage is challenging.…”