Martin Willmann

Silicon pressure sensor with integrated CMOS signal-conditioning circuit and compensation of temperature coefficient

Abstract A silicon pressure sensor designed for automotive applications with on-chip signal conditioning is presented. The micromechanical processing steps are added to a standard 3 μm CMOS process. The membrane is etched in (100)-oriented Si by anisotropic etching with an electrochemical etch stop. Thickness control with tolerances of less than 0.5 μm is readily achieved. A complete CMOS evaluation circuit is integrated on the same device. The signal of the piezoresistive Wheatstone bridge is processed by an instrumentation amplifier with temperature-dependent amplification for on-chip compensation of the sensitivity variation with temperature. Moreover, the sensitivity variation itself, the offset and the offset variation with temperature are compensated. On-chip trimming is provided for the adjustment of these terms in the full automotive temperature range from −40 °C to + 125 °C.

Micromachined thermoelectrically driven cantilever structures for fluid jet deflection

The design, fabrication, and performance of bimorph cantilever structures for direction control of laminar jet flow are reported. The fabrication process comprises standard IC technologies and additional silicon micromachining techniques. The design parameters for the structures are obtained using analytical approximations and numerical simulations. Forced convection as the decisive cooling mechanism proves to be very effective, resulting in an excellent dynamic response of the thermoelectrically activated structures. Experimental testing confirmed the predicted stationary and transient behavior of 1-mm-long and 1-mm-wide actuators, which are able to control hydraulic power at pressure levels of up to 4 bar, flow rates of up to 150 ml/min, and time constants of about 1 ms.<<ETX>>

Fully Integrated Silicon Pressure Sensor with On-Chip CMOS Evaluation Circuit and On-Chip Trimming

A silicon pressure sensor with an integrated signal conditioning circuit has been developed for automotive applications. The sensor is fabricated with a standard 3μm CMOS process. The membrane is formed by anisotropic etching in (100)-oriented silicon using an electrochemical etch stop. A complete signal conditioning circuit is added to amplify the Bridge output signal. Furthermore, the sensor offset, the sensitivity, and the temperature effects on offset and sensitivity values are adjusted individually. Compensation is done for a temperature range from −40 to +125°C. On-chip trimming is provided for the adjustment of the correction values.