3C-SiC — From Electronic to MEMS Devices

Abstract

Since decades, silicon carbide (SiC) has been avowed as an interesting material for highpower and high-temperature applications because of its significant properties including its wide bandgap energy and high temperature stability. SiC is also professed as an ideal candidate for microsystem applications due to its excellent mechanical properties and chemical inertia, making it suitable for harsh environments. Among the 250 different SiC polytypes, only 4H, 6H and 3C-SiC are commercially available. The cubic structure, 3C-SiC, is the only one that can be grown on cheap silicon substrates. Hence, 3C-SiC is more interesting than any other polytype for reducing fabrication costs and increasing wafer diameter. This huge property has been evidenced for more than 30 years using chemical vapor deposition. Despite this key achievement and the growing interest for silicon carbide, no 3C-SiC-based devices can be found on the market whereas 4H-SiCbased devices are more and more largely commercialized. Even so, important headways have been reached for electrical and microelectromechanical systems (MEMS) applications. Therefore, the purpose of this chapter is to address concerns related to electronic applications and MEMS fabrication of 3C-SiC-based devices, trying to give a broad overview on specific issues and challenging solutions.

Surface stabilities of 3C–SiC and H2O adsorption on the (110) surface

“…Besides, 3C–SiC has a smaller band gap (2.2 eV), lower breakdown electric field strength, and higher electron mobility than all α‐SiC polytypes, which can be more favorable for applications in high temperature, high power, and high frequency electronic devices . The high‐purity low‐cost 3C–SiC is also commonly used for sintering superplasticity ceramics . More especially, cubic 3C–SiC is the most commonly used polytype of SiC in the nuclear fuel applications where 3C–SiC is inevitably in contact with H 2 O.…”

Emerging SiC Applications beyond Power Electronic Devices

“…Nevertheless, it is crucial to notice that the mechanical properties of SiC, such as its high Young’s modulus or the layer internal stresses, are in such cases largely affected, and may negatively impact vibrating MEMS structures. Indeed, the Young’s modulus (E) values obtained, through MEMS (clamped beams, membranes) structures, clearly indicate that E strongly depends on a crystalline structure or orientation, thicknesses and doping type and level (by at least a factor of 3, from 120 to 500 GPa) [ 21 , 24 , 142 , 143 , 144 , 145 , 146 , 147 ]. In particular, a strong dependence of the Young’s modulus from both point defects [ 24 ] and stacking faults [ 142 ] has been reported.…”

“…Many masks for RIE technologies have been tested as thick photoresists, or SiOx and Al 2 O 3 without convincing success. The most efficient mask seems to be the hard mask using Ni, which is related to its inertness to the species present in the plasmas used [ 21 ]. The RIE or ICP etching processes of SiC are nowadays still far from the performances that are possible on silicon (such as those provided by cryogenic or DRIE etching), both in terms of maximum depth and anisotropy.…”

“…Silicon Carbide is a suitable material for fabricating even MEMS devices [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ], particularly when it is grown on silicon substrates, because in this case it is relatively easy to create suspended structures by removing the underlying silicon with various consolidated techniques. Moreover, the mechanical properties of epitaxially grown SiC on silicon are excellent ( Table 1 ), and this allows MEMS devices with very good performances to be obtained.…”

Investigation of the Young’s Modulus and the Residual Stress of 4H-SiC Circular Membranes on 4H-SiC Substrates

“…Silicon carbide (SiC) is recognized as an excellent material for power applications due to notable electrical properties but SiC is also an outstanding candidate for microelectromechanical systems (MEMS) thanks to its distinguished chemical and mechanical properties [1]. Therefore, sensors that are able to detect temperature, gas, and pressure in aerospace or the automotive field are potential applications of SiC-based devices [2][3][4]. The cubic 3C-SiC polytype is favoured for MEMS applications as it can be epitaxially grown on silicon (Si) substrates and thus offers a low-cost solution for SiC-based MEMS development coupled with the conventional Si technologies.…”