Fabrication of 3C-Silicon Carbide Membranes: Towards Development of Novel Microdevices for Biomedical Applications
Microelectromechanical (MEMS) devices with high biocompatibility are the ideal medical solution to many types of human disease prevention and detection system. The best condition for human physiological measurements is to avoid disruption of patient’s normal activity and this can be achieved by implantable biomedical microdevices. Conceptually, BioMEMS technology offer prospective devices with low power consumption, low production cost and miniaturization of size and weights for implants and continuous patient monitoring. However, apart from electronic design and fabrication issues, the material chosen for the device should be biocompatible and easy to adapt to traditional microfabrication technology in Silicon (Si). Silicon carbide (SiC) has the properties and characteristics that could meet these requirements together with its excellent electrical, mechanical and chemical properties.
Approximately 250 polytypes of SiC have been identified in recent years . Of these polytypes, the only cubic variety known to exist is the 3C-SiC (or β-SiC). In terms of electrical properties, the 3C-SiC polytype has shown the smallest bandgap of 2.3 eV compared to all SiC polytypes. 3C-SiC is also the polytype with the highest electron mobility (1000 cm2/Vs) and saturation drift velocity (10 cm/s) which has been partially attributed to its cubic crystalline symmetry. Epitaxial layers of 3C-SiC have shown great potential in micro and nanoelectromechanical system (MEMS and NEMS) applications since the film can be grown on silicon substrates using chemical vapor deposition. This attracts many possible applications especially in biomedical microdevices. However, rigorous biocompatibility studies were performed on the devices fabricated from hexagonal crystal variants of SiC (4H-SiC).
Few biocompatibility studies were conducted on 3C-SiC using testing procedure in accordance to ISO 10993. It is found as a bulk material, 3C-SiC did not induce cytotoxicity to the mouse fibroblast in in vitro environment and behave as non-irritants after one and 12 week of rabbit muscle implantation. However, it is suggested that the biocompatibility of 3C-SiC may change in respective to the fabrication process. In medical electronics, 3C-SiC was used as the main material to construct a brain machine interface device. 3C-SiC membrane can be a suitable candidate as a deflective structure of a pressure sensor especially for invasive blood pressure monitoring in critical care unit (CCU). Lab-on-chip systems which requires biocompatible membrane as a part of the device can utilize 3C-SiC membrane as a working structure. 3C-SiC membrane was also used as a superlens in near-field scanning optical microscopy (NSOM). It is suggested the 3C-SiC superlens can be applied as a microfluidic structure for NSOM imaging for biotechnology and medical application .