Silicon carbide dry etching technique for pressure sensors design

This paper presents the results of an in-depth study of the plasma-chemical etching (PCE) process of single-crystal silicon carbide (SiC) in SF6/O-2 inductively coupled plasma (ICP). Using the method of optical emission spectroscopy (OES) we have examined the influence of RF power, bias voltage, pressure in the reaction chamber, and gas mixture composition on SiC PCE as well as the applicability of the OES technique for optimization and monitoring of SiC dry etching process in SF6/O-2 ICP. An optimized PCE process for mass-manufacturing of SiC diaphragms of less than 20 mu m thickness with an etch rate of more than 1.2 mu m/min, and with an Rms of the etched surface of about 0.7 nm is developed. The influence of microtrenches on the electromechanical characteristics of the diaphragm as part of a capacitive pressure sensor is studied by means of computational simulation. An ideal diaphragm is compared with a real-process produced diaphragm with the microtrenching effect. It was shown that this effect has a great impact on the mechanical characteristics of the diaphragm. It is demonstrated that the von Mises stress at an applied pressure of 0.2 MPa for the real diaphragm is 183 MPa, while for the ideal diaphragm only 88 MPa.