With the increasing requirements for microelectromechanical systems (MEMS) regarding stability, miniaturization and integration, novel materials such as wide band gap semiconductors are attracting more attention. Polycrystalline SiC has first been implemented into Si micromachining techniques, mainly as etch stop and protective layers. However, the outstanding properties of wide band gap semiconductors offer many more possibilities for the implementation of new functionalities. Now, a variety of technologies for SiC and group III nitrides exist to fabricate fully wide band gap semiconductor based MEMS. In this paper we first review the basic technology (deposition and etching) for group III nitrides and SiC with a special focus on the fabrication of three-dimensional microstructures relevant for MEMS. The basic operation principle for MEMS with wide band gap semiconductors is described. Finally, the first applications of SiC based MEMS are demonstrated, and innovative MEMS and NEMS devices are reviewed.

http://iopscience.iop.org/article/10.1088/0022-3727/40/20/S19/pdf

Group III nitride and SiC based MEMS and NEMS: materials properties, technology and applications

Advances in silicon carbide microfabrication and growth process optimization for silicon carbide nanostructures are ushering in new opportunities for microdevices capable of operation in a variety of demanding applications, involving high temperature, radiation, or corrosive environment. This review focuses on the materials science and processing technologies for silicon carbide thin films and low dimensional structures, and details recent progress in manufacturing technology, including deposition, metallization, and fabrication of semiconductor microdevices, with emphasis on sensor technology. The challenges remaining in developing silicon carbide as a mainstay materials platform are discussed throughout.

Advances in silicon carbide science and technology at the micro- and nanoscales

Silicon carbide (SiC) is recognized as the leading semiconductor for high power and high temperature electronics owing to its outstanding electrical properties combined with mature processing technologies for monolithic structures. SiC has long been known for its outstanding mechanical and chemical properties making it equally attractive for mechanical structures in micro- and nanoelectromechanical systems (MEMS and NEMS). Recent advancements in bulk and surface micromachining have led to the development of SiC analogues to common Si-based devices (i.e., resonators, pressure sensors). This paper presents an overview of MEMS and NEMS technologies that incorporate SiC as a key component in their mechanical structure, providing both a historical perspective as well as recent developments. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Micro‐ and nanomechanical structures for silicon carbide MEMS and NEMS

Vicinal $4H$ and $6H\mathrm{\text{\ensuremath{-}}}\mathrm{S}\mathrm{i}\mathrm{C}(0001)$ surfaces have been investigated using atomic force microscopy and cross-sectional high-resolution transmission electron microscopy. We observed the characteristic self-ordering of nanofacets on any surface, regardless of polytypes and vicinal angles, after gas etching at high temperature. Two facet planes are typically revealed: (0001) and high index $(11\overline{2}n)$ that are induced by equilibrium surface phase separation. A $(11\overline{2}n)$ plane may have a free energy minimum due to attractive step-step interactions. The differing ordering distances in $4H$ and $6H$ polytypes imply the existence of SiC polytypic dependence on nanofaceting. Thus, it should be possible to control SiC surface nanostructures by selecting a polytype, a vicinal angle, and an etching temperature.

/pdf/self-ordering-of-nanofacets-on-vicinal-sic-surfaces-1099jmfubp.pdf

Self-Ordering of Nanofacets on Vicinal SiC Surfaces

From thin film to bulk 3C-SiC growth: Understanding the mechanism of defects reduction

We study the influence of the growth conditions on the residual strain and related optical and structural properties in the case of 3C-SiC films grown on (001) silicon substrates. We show that two possible mechanisms compete to manage the final sample bow: one is by controlling the composition of the gaseous phase (C/Si ratio) the other one by adjusting the growth temperature and duration (creep effect). In both cases, we compare the low temperature photoluminescence spectra of samples grown under tensile or compressive final stress. We show that better results can be obtained when using the creep effect.

Strain and wafer curvature of 3C-SiC films on silicon : influence of the growth conditions

Strain and wafer curvature of 3C-SiC films on silicon: influence of the growth conditions

Due to the large differences in lattice parameters and thermal expansion coefficients, the heteroepitaxial growth of 3C-SiC on Si mainly results in highly defective layers on strongly bent wafers. The defects may not be detrimental for very basic applications, but the bow is. In this article, we review several attempts to reduce the final curvature after epitaxial growth of 3C-SiC. One is the use of the "checkerboard" carbonization process which creates a macroscopic balance of the stress by the formation of a regular network of compressed and tensed areas. Another approach proposes to create, in situ, a random patchwork of tensed and compressed areas during the carbonization step. The other attempts use substrates other than standard Si, namely silicon on insulator and Si-Ge substrates for compliance effect and closer thermal expansion mismatch with SiC, respectively. All techniques provoke a significant reduction of the strain in the deposited 3C-SiC layers.

Strain Tailoring in 3C-SiC Heteroepitaxial Layers Grown on Si(100)

In this work the authors study the strain of 3C-SiC thin films grown on (001) on-axis silicon substrates. They use ex situ wafer curvature measurements to monitor the residual strain of silicon carbide film. At high temperature creep effects take place and modify the intrinsic strain of silicon carbide film. From the time and temperature dependences of these effects, they determine the creep exponent and the creep activation energy for 3C-SiC. Obtained values of N=2.6±0.3 and Q=5.6±1.0eV are similar to those reported in literature for hexagonal polytypes of silicon carbide.

André Leycuras

Papers

Strain and wafer curvature of 3C-SiC films on silicon : influence of the growth conditions

Strain and wafer curvature of 3C-SiC films on silicon: influence of the growth conditions

Strain Tailoring in 3C-SiC Heteroepitaxial Layers Grown on Si(100)

Stress relaxation during the growth of 3C-SiC∕Si thin films

Growth of CVD thin films and thick LPE 3C SiC in a specially designed reactor