A Smart Sensor Device Realized in Standard CMOS-Technology based on an ASIC-Design

The presented smart sensor dimensioned for measuring pressures between 0 and 1000 mbar has been monolithically integrated on a single silicon chip. An efficient development of such sensor-systems can be done using two well-known techniques: ASIC design methodology and standard CMOS processing. Based on the cell library of a commercial semiconductor manufacturer, sensor-specific CMOS cells have been developed and were defined as new library elements. So conventional CAD-tools can be used composing and checking the layout of the smart sensor. Also a electro-mechanical simulation model of the piezoresistive transducer has been developed. Technology dependend parameters were evaluated by measurements of pure bending of cantilever structures under different temperature conditions. The netlist was extracted from the layout, combined with the mechanical simulation model and used for a system simulation of the smart sensor. So the system can be checked and optimized before its fabrication. The sensor system was realized in two steps: First, the electronic components of the sensor element and the devices of the signal conditioning circuit have ben manufactured by the ES2 wafer fab. This was done without any modifications to their 1.5 μm n-well CMOS process. After this, the micromechanical structuring of the device was done by anisotropic etching. The sensor was mounted onto DIL header using an intermediate silicon substrate to reduce mechanical stress. The charcateristics of the balanced smart sensor shows a total system error of less than 0.7 % in good agreement with the simulation results.