Ingo Herrmann

Temperature sensitivity modeling of pn-junction diodes for microbolometer-based thermal imaging applications

A model for the electrical behavior of pn-junction diodes biased in forward direction and used as a temperature sensitive device (TSD) in microbolometers is presented. It is based on the well-known Shockley equation extended by the ideality factor m. We demonstrate that the largest temperature sensitivity can be reached for diodes at low current density operation featuring a high ideality factor m > 1.

Low-cost Approach for Far-Infrared Sensor Arrays for Hot-Spot Detection in Automotive Night Vision Systems

Sensor data fusion of active near infrared (NIR) and passive far infrared (FIR) for reliable detection of vulnerable road users in future warning automotive night vision systems requires for low-cost, mid-resolution FIR sensor arrays for hot spot detection. We present a new cost efficient technology for FIR arrays adopting a volume proven integrated MEMS process for the production of a suspended thermo-diode array. In contrast to established bolometer production all steps of the process developed are fully semiconductor compatible as the sensor element formation is an integral part of the read out IC processing and does not require ASIC backend processing with dedicated equipment. Vacuum wafer-level packaging compatibility further reduces cost. In a first step the proposed process has been verified with small integrated FIR arrays consisting of 42x28 pixels. The FIR array development reported is part of the EU FP7 project ‘ADOSE’.

Low-cost microbolometer with nano-scaled plasmonic absorbers for far infrared thermal imaging applications

We present a scalable low-cost microbolometer technology platform which is based on separate fabrication of MEMS and read-out ASIC CMOS wafers. Mechanical, electrical and hermetical connection is achieved by Cu-based thermocompression bonding. The performance loss due to the resulting backside illumination of the sensor is compensated by an optimized microbolometer design including nano-scaled plasmonic absorbers, a dedicated pixel geometry and the use of highly temperature sensitive devices. The low-cost approach features CMOS compatible MEMS processes, wafer level packaging and uncooled operation of the sensor.

Microbolometer technology using serial pn-diodes

A fabrication process for a thermo-diode microbolometer array is presented. The process is based on a sintered porous silicon (sPS) technique adopted from Chipfilm™ technology to enable vertical thermal insulation of the pixels. In addition, the process offers the possibility to have more than one diode per pixel connected in series. It is demonstrated that this boosts the temperature sensitivity of the device.