Porous Silicon Carbide for MEMS

Journal of Physics: Conference Series, 2009

Porous amorphous SiC (a-SiC) layer with pore size in the nanometer region was fabricated on the a-SiC/Si substrates by the electrochemical etching method using HF/H2O/surfactant solution. Systematic study showed that the HF concentration in the etching solution (in the 1-73% region) strongly affects the structure (both the pore size and the pore density) of the porous a-SiC layer. It was also observed the changing of the photoluminescence properties of the porous a-SiC layer when its structure has been changed.

AIP Advances, 2014

In this report, we fabricated a porous layer in amorphous SiC thin films by using constant-current anodic etching in an electrolyte of aqueous diluted hydrofluoric acid. The morphology of the porous amorphous SiC layer changed as the anodic current density changed: At low current density, the porous layer had a low pore density and consisted of small pores that branched downward. At moderate current density, the pore size and depth increased, and the pores grew perpendicular to the surface, creating a columnar pore structure. At high current density, the porous structure remained perpendicular, the pore size increased, and the pore depth decreased. We explained the changes in pore size and depth at high current density by the growth of a silicon oxide layer during etching at the tips of the pores.

Applied Surface Science, 2010

In this work, we present the formation of porous layers on hydrogenated amorphous SiC (a-SiC: H) by Ag-assisted photochemical etching using HF/K 2 S 2 O 8 solution under UV illumination at 254 nm wavelength. The amorphous films a-SiC: H were elaborated by d.c. magnetron sputtering using a hot pressed polycrystalline 6H-SiC target. Because of the high resistivity of the SiC layer, around 1.6 M cm and in order to facilitate the chemical etching, a thin metallic film of high purity silver (Ag) has been deposited under vacuum onto the thin a-SiC: H layer. The etched surface was characterized by scanning electron microscopy, secondary ion mass spectroscopy, infrared spectroscopy and photoluminescence. The results show that the morphology of etched a-SiC: H surface evolves with etching time. For an etching time of 20 min the surface presents a hemispherical crater, indicating that the porous SiC layer is perforated. Photoluminescence characterization of etched a-SiC: H samples for 20 min shows a high and an intense blue PL, whereas it has been shown that the PL decreases for higher etching time. Finally, a dissolution mechanism of the silicon carbide in 1HF/1K 2 S 2 O 8 solution has been proposed.

Due to its desirable material properties, Silicon Carbide (SiC) has become an alternative material to replace Si for Microelectromechanical Systems (MEMS) applications in harsh environments. To promote SiC MEMS development towards future cost-effective products, main technology areas in material deposition and processes have attracted significant interest. The developments in these areas have contributed to the rapid emergence of SiC MEMS prototypes. In this paper, we give an overview of the important developments in SiC material formation and fabrication processes in recent years. Some of the most interesting state-of-the-art SiC MEMS devices are reviewed. This highlights the major progresses in SiC MEMS developed thus far. This paper also looks into the prospect of SiC MEMS drawing attention to potential issues.

physica status solidi (c), 2011

Materials Science Forum, 2006

The effects of initial surface morphology on the early stages of porous SiC formation under highly biased photoelectrochemical etching conditions are discussed. We etched both Si-face and C-face polished n-type 6H SiC with different surface finishes prepared either by mechanical polishing or by chemical mechanical polishing at NOVASiC. For both Si-face and C-face porous SiC samples, a variety of surface and cross sectional porous morphologies, due to different surface finishes, are observed. The proposed explanation is based on the spatial distribution of holes at the interface of the SiC and electrolyte inside the semiconductor.

International Materials Reviews, 2000

Any discussion concerning SiC as a material for MEMS first requires a basic understanding of these Silicon carbide (SiC) has recently attracted micromachining processes. attention as a wide bandgap semiconductor with great potential for microelectromechanical Bulk micromachining was developed in the 1970s systems (MEMS). SiC exhibits excellent electrical, as an extension of IC technology for the fabrication mechanical, and chemical properties, making it of three-dimensional structures.1 Bulk micromachinwell suited for harsh environment applications ing of silicon uses wet and dry etching techniques in where traditional MEMS are constrained by the conjunction with etch masks and etch stops to sculpt physical limitations of silicon (Si). This paper micromechanical devices from the Si substrate. There reviews the material properties, deposition are two key capabilities that make bulk micromachintechniques, micromachining processes, and other ing of Si a viable technology. First, the availability of issues regarding the fabrication of SiC-based anisotropic etchants of Si such as ethylene-diamine sensors and actuators. Special emphasis is placed pyrocatecol (EDP) and potassium hydroxide (KOH), on the properties that make SiC attractive for MEMS, and the Si-based processing techniques which preferentially etch single crystal Si along select that have been adapted to realise SiC MEMS crystal planes. Second, the availability of etch masks structures and devices. An introduction to and etch-stop techniques which can be used in conmicromachining is provided for readers not junction with silicon anisotropic etchants to prevent familiar with MEMS fabrication techniques.

Advances in Natural Sciences: Nanoscience and Nanotechnology, 2011

Porous amorphous silicon carbide (P-aSiC) was prepared by an electrochemical etching method. The surface morphology of the samples was measured by an atomic force microscope (AFM). Photoluminescence (PL) and PL excitation spectra of the samples were measured at room temperature. We observed clear dependence of PL spectra and morphology on fabrication conditions. Based on these results, we propose the emitting mechanism of the PL from the samples.