Thoralf Kautzsch

A system-on-chip NFC bicycle tire pressure measurement system

This paper presents a monolithically implemented NFC bicycle tire pressure measurement system (BTPMS) with integrated antenna, on-chip capacitive pressure and temperature sensor, RFID interface for HF/NFC and EEPROM. This NFC BTPMS has been designed using a 130 nm standard CMOS process and has an active chip area of 5.76 mm2. It provides significant cost advantages and impresses with its large scale integration. The used ISO 14443 RFID communication protocol ensures compatibility with state-of-the-art NFC devices. Configuration and calibration data are stored in the integrated EEP-ROM. This battery less stand-alone system is powered wirelessly by any state-of-the-art near field communication device. Using a two-point calibration technique, various measurements have been performed and analyzed regarding accuracy, sensitivity, reproducibility, and temperature dependency. In the pressure range of 1 bar to 6 bar and for temperatures between −15°C to 55°C a ±3σ accuracy of ±0.4 bar is achieved.

Investigation of amorphous hydrogenated carbon layers as sacrificial structures for MEMS applications

This work presents a novel approach that utilizes amorphous hydrogenated carbon (a-C:H) layers as sacrificial structures for MEMS applications. The a-C:H layer serves as a buried sacrificial layer in the fabrication process. With the removal of the a-C:H by plasma etching processes, the movable structures are released. The fabrication of test structures is based on silicon surface micromachining technology. On those test structures, etch rates were determined for two different etch chemistries. The use of a-C:H as a sacrificial layer offers several advantages such as dry release capabilities accompanied by a high thermal and mechanical stability of the sacrificial layer and thus the possibility to integrate those layers in standard CMOS technology. Consequently, the proposed dry removal techniques prevent movable structural components from stiction problems associated with wet processing. The newly developed sacrificial layer process is suitable for a wide range of MEMS applications.

A capacitive pressure sensor with minimum foot print for CMOS integration

A novel capacitive pressure sensor with minimum foot print is presented. This sensor is fabricated by implementing an ultrahigh-aspect-ratio deep trench etch process to build vertically integrated sensing membranes and reference electrodes on a silicon chip. The bulk silicon membranes are isolated at their bottom sides via counter-doped regions. Each sensor element is surrounded by ventilation channels, connecting membranes to the ambient atmosphere via openings at the chip side or in the metallization stack. The cavities and ventilation channels are sealed by a high density plasma oxide without any need of sacrificial layer deposition and removal. A single element with two sensing membranes and cavities for a capacitive read out has a lateral size of less than one micron and a depth of eight microns. By this approach, very compact sensors are achieved, reaching a capacitive sensitivity per area of up to 50aF/(μm2·bar), surpassing by far all common surface integrated sensor designs.

A trench gate photo cell for spectrometric applications

A new trench gate photo cell for spectrometric sensing is demonstrated. By combining a trench structure with a gradually doped base, an electrically tunable device with minimum foot print and excellent spectral resolution is achieved. It offers new opportunities for ambient light recognition of mobile devices and for medical applications.