Fabrication and characterization of single-crystal 4H-SiC microactuators for MHz frequency operation and determination of Young’s modulus

Highlights

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Single crystal 4H-SiC MEMS actuators with MHz resonant frequency were demonstrated.

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Young’s modulus of 4H-SiC were determined.

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The device truly exploits SiC superior material properties for harsh environments.

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The high frequency is desirable for ultrafast and high resolution sensors/actuators.

Silicon carbide (SiC), a wide bandgap semiconductor, is more desirable over conventional silicon (Si) to satisfy the increasing demands for microelectromechanical system (MEMS) to operate in harsh environments due to the excellent physical, mechanical and chemical inertness. Research in MEMS devices based on single or polycrystalline SiC on Si or SOI substrate, such as 3C-SiC polytype, have been widely carried out. Another promising candidate is “all”-SiC, i.e., homoepitaxial single crystal SiC layer on single-crystal SiC substrate, such as 4H and 6H-SiC polytypes. They truly exploit the superior material properties of SiC and provide advantages for MEMS devices to operate in hostile conditions. In this work, 4H-SiC MEMS actuators in cantilever and bridge configurations were fabricated by a surface micromachining process, and their dynamic responses were characterized to determine Young’s modulus of 4H-SiC and frequency performance. Resonant frequencies of 1.208 MHz from cantilever and 1.338 MHz from bridge actuators were achieved. These high frequency operation capabilities are particular interesting for ultrafast and high resolution sensors and actuators.

Graphical abstract

Keywords

• 4H-SiC; 
• MEMS; 
• Microactuator; 
• MHz frequency; 
• Young’s modulus

Source:Sciencedirect

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Effects of surface/interface states on Schottky contacts for 4H-SiC

Electrical characteristics of sputter deposited Ni, Cr, Au, Pt, and Ti contacts on SiC-4H were studied. The 4H-SiC substrates used were test grade, single crystalline, and n-type. These contacts were found to be rectifying. Saturation current densities, ideality factors and Schottky barrier heights were determined from these measurements. Argon plasma sputtering degraded the contact by increasing the reverse current and lowering the turn-on voltage. The calculated Schottky barrier heights were ranged from /spl sim/ 0.8 eV to /spl sim/ 13 eV and reverse current was found to be as low as 136.5 nA/cm/sup 2/ at -5 V. For RCA cleaned samples, the barrier heights are weakly dependent on metal work function and were largely determined by metal induced gap states (MIGS) and electronegativity difference between metal and semiconductor. However, in RCA + Ar plasma sputter cleaned samples, the barrier heights were independent of the metal work function determined entirely by MIGS and surface/interface states.

Index Terms:
Ar, Schottky contacts, surface/interface states, sputter deposition, single crystalline, saturation current densities, ideality factors, argon plasma sputtering, reverse current, calculated Schottky barrier heights, metal work function, metal induced gap states, SiC:H, Ni, Cr, Au, Pt, Ti

Citation:
Md.M. Islam, K. Das, "Effects of surface/interface states on Schottky contacts for 4H-SiC," ssst, pp.378-382, Proceedings of the Thirty-Seventh Southeastern Symposium on System Theory.

source:IEEE

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