PECVD amorphous silicon carbide membranes for cell culturing

This paper presents the fabrication of low-stress amorphous silicon carbide films (α-SiC) deposited in plasma-enhanced chemical vapour deposition (PECVD) reactors and its application as α-SiC membrane for cell culture. Deposition in the high-frequency generator mode (13.56 MHz) proved to be superior since it provides both a low-stress value (and which can be tuned from tensile to compressive by selecting the correct power) and a high deposition rate. In contrast, the films deposited in the low-frequency mode (380 kHz) have high compressive stress (around 500 MPa) due to ion bombardment that results in the densification of the deposited layer. As expected, increasing the deposition temperature in any frequency deposition mode decreases the stress value. The main deposition parameters were then tuned in order to achieve a low stress and high deposition rate. Our experiments also show that PECVD α-SiC layers have low etching rates both in KOH and HF solutions, and, therefore, α-SiC is a very suitable inert masking material for wet etching in micromachining. Moreover, the feasibility of using PECVD α-SiC as substrate material for cell cultures was also studied and is described in this paper. Low-stress α-SiC released membranes were fabricated and subsequently used as cell culture support and compared with monocrystalline SiC and non-released films deposited uniformly on a Si substrate, respectively. Our experiments indicate that PECVD α-SiC can be successfully used for cell culturing, especially after it is treated in NH4F. However, if the layer was initially exposed to KOH, the biocompatibility of the α-SiC surface degrades and is very similar with that observed for single crystal SiC. Very good results were obtained when using released 2.5-μm-thick α-SiC membranes pre-treated in NH4F as cell culture substrates, proving the excellent biocompatibility of PECVD α-SiC and its suitability for other future biomedical related applications.