Max Steger

Implantable low power integrated pressure sensor system for minimal invasive telemetric patient monitoring

A new low power integrated pressure sensor system with digital output (1 bit PDM signal) for medical applications is presented. The absolute pressure sensor comprising 400 nm thick surface micromachined polysilicon membranes for capacitive pressure detection and a monolithic integrated 2/sup nd/ order sigma-delta-modulator including voltage reference and timing generator is extremely miniaturized on an area of approximately 3 mm/sup 2/. For protection and biocompatibility reasons the sensor is coated with a silicone elastomer of up to 100 /spl mu/m thickness, which does not influence the sensors performance. The sensor system was tested in vitro in physiological NaCl solution, showing excellent results compared to a commercially available reference sensor. The sensor system is working well down to a supply voltage of 2.2 V at a power consumption of 0.5 mW. The resolution is better than 12 bit. Due to the small chip area, low power consumption and cost effective production process, the sensor is ideal for medical applications, e.g. in combination with telemetric power and data transmission as an implantable sensor to reduce the mortality risk of intensive care patients.

Low power integrated pressure sensor system for medical applications

Abstract A new low power integrated pressure sensor system with digital output (1 bit PDM signal) for medical applications is presented. The absolute pressure sensor comprising 400 nm thick surface micromachined polysilicon membranes for capacitive pressure detection and a monolithic integrated 2nd order sigma–delta-modulator including voltage reference and timing generator is extremely miniaturized on an area of approximately 3 mm 2 . For protection and biocompatibility reasons the sensor is coated with a silicone elastomer of up to 100 μm thickness, which does not influence the sensors performance. The sensor system was tested in vitro in physiological NaCl solution, showing excellent results compared to a commercial available reference sensor. The sensor system is working well down to a supply voltage of 2.2 V with a power consumption of 0.5 mW. The resolution is better than 12 bit. Due to the small chip area, low power consumption and cost effective production process, the sensor is ideal for medical applications, e.g., in combination with telemetric power and data transmission [J. Zacheja, B. Clasbrummel, J. Binder, U. Steinau, Implantable Telemetric Endosystem for Minimal Invasive Pressure Measurements, MedTech95, Berlin, Germany, (1995)] as an implantable sensor to reduce the mortality risk of intensive care patients.

Full integration of a pressure-sensor system into a standard BiCMOS process

Abstract We report a novel process for the full integration of surface-micromachined pressure-sensor cells into a standard BiCMOS process. Only the standard layers of the BiCMOS process are used to build up the sensor and only one additional photolithography step is necessary to achieve the micromachined structures. The application of the process is demonstrated by means of an integrated pressure-sensor system at a working range of 0.1 to 1.1 bar of absolute pressure. The influence of process parameters and tolerances of the VLSI process on the sensor performance are examined. To examine the long-term stability, the sensors are electrically deflected at the resonance frequency applying 4 × 10 11 load cycles. The measurements do not show any changes in the mechanical behaviour, so a very high long-term stability can be proven. In contrast to all integrated micromechanical systems presented so far, neither prenor post-processing of the system is necessary. Compared to conventional surface micromachining, the additional processing effort for the sensor realization is reduced dramatically to about 5% of the BiCMOS process.

A pure CMOS surface micromachined integrated accelerometer

A pure CMOS integrated accelerometer was realised using surface micromachining as structural technique. The samples were fabricated by a 14 mask 0.8 /spl mu/m CMOS standard process in a Siemens production line. Only the standard layers of the process (350 nm polysilicon and 600 nm oxide as sacrificial layer) are used to build up the surface micromachined device. Sensor release and antisticking are also CMOS-compatible. The movement of a seismic mass normal to the chip surface is capacitively detected (open loop) and transformed on chip into a digital output signal by a robust circuit for measuring sub-fF capacitance differences. Parasitics are suppressed on chip. The sensor was designed to measure accelerations up to 50 g. A resolution of /spl plusmn/0.6 g corresponding to a capacitance change of /spl plusmn/0.1 fF was observed.

A pure CMOS surface-micromachined integrated accelerometer

Abstract A pure CMOS integrated accelerometer has been realized using surface micromachining as the structural technique. The samples are fabricated by a 14-mask 0.8 μm CMOS standard process in a Siemens production line. Only the standard layers of the process (350 nm polysilicon and 600 nm oxide as sacrificial layer) are used to build up the surface-micromachined device. Sensor release and antisticking are also CMOS-compatible. The movement of a seismic mass normal to the chip surface is capacitively detected (open loop) and transformed on chip into a digital output signal by a robust circuit for measuring sub-femtofarad capacitance difference. Parasitics are suppressed on chip. The sensor is designed to measure accelerations up to 50g. A resolution of ± 0.6g, corresponding to a capacitance change of ± 0.1fF, is observed.