Diamond microelectromechanical sensors (DMEMS)

CVD deposited diamond films, processed similar to conventional semiconductor devices, are used to achieve microelectromechanical systems (MEMS). Cantilever beams, membranes, stripes, and tips used as components in accelerometers, pressure sensors, and other devices can be constructed in doped and undoped diamond films. This paper will focus on the aspects of achieving diamond MEMS (DMEMS) for a high bandwidth, high temperature pressure sensor. The high elastic modulus of diamond provides a stiff substrate for the high temperature electromechanical device. The intended operating range of the device is over 600/spl deg/C, measuring dynamic pressures with a 0.002 psi response. The effects of temperature on ionization of dopants, the piezoresistance and gage factor of diamond are measured. The diamond pressure sensor has two key components, the intrinsic diamond membrane and the doped diamond piezoresistors (PZRs). These piezoresistors are delineated by an etch process and reside integral to the i-diamond membrane and substrate. Processing and behavior results of such diamond microstructures will be discussed. Also, PZR element placement on the membrane is evaluated for strain effect, signal, and gauge factor performance. The effect of the conductivity of i-diamond on sensor behavior, particularly at higher temperatures is evaluated. Further, the mechanical strength of the diamond membranes is examined.