Bernhard Winkler

Temperature Compensation in Silicon-Based Micro-Electromechanical Resonators

In this paper, we present passive temperature compensation by means of silicon dioxide. Using an oxide refilling technique it avoids gap distance reduction and therefore prevents degradation of electromechanical coupling and motional resistance of the micro-electromechanical resonator. Samples are fabricated and electrically characterized to demonstrate the feasibility of the process concept. A constant quality factor (Q) and only a slight increase of the series resistance value (Rm) are achieved, while the frequency inaccuracy due to temperature variation is reduced. ANSYS simulations are carried out to evaluate the potential of the technique, resulting in a remaining inaccuracy of less than 40ppm.

Novel surface-micromachined low-power fuses for on-chip calibration

A novel low-power polysilicon fuse of high reliability was developed. The power consumption is so small that the fuse can be blown with an on-chip circuit. The fuse can be blown with high yield by voltage pulses of an amplitude of approx. 4V and a blowing current of 20…40mA. The fuse is typically blown after 1µs. The total energy consumption amounts to 110nJ. The resistance changes by more than 8 decades. Because of its low power consumption the fuse can be used to realize an on-chip programmable PROM. This offers the possibility to calibrate chips after mounting and packaging. This paper describes the fuse itself and its application for the calibration of micromechanical sensors after packaging.

Pyroelectric Thin Film Presence Detector Arrays with Micromachined Pixels

Lately, pyroelectric thin film detectors gain in significance in the field of presence detection. In the paper, different variants of Pb(ZrTi)O 3 based detector arrays with 8 to 256 pixels are introduced. The sensing elements are arranged on thin micromachined SiO 2 /Si 3 N 4 membranes [1-4] as mechanical supporting structure with both low thermal mass and low heat conductivity into the substrate to achieve a high detectivity. For shaping these membrane structures, the most promising technology is micromachining, either from back or from surface of the silicon substrate. Self-polarized PZT thin films with a pyroelectric coefficient p up to 2.1 * 10 m 4 C/(m 2 K), dielectric loss tan i of less than 0.01 and a dielectric coefficient l r of about 250 are deposited in a multi-target sputtering process at comparatively low substrate temperatures of about 520°C. In the paper, presence detectors using thin film pyroelectric IR detector arrays as well as detector design, detector simulation, detector manufacturing and detector characteristics are discussed. In addition, pyroelectric material investigations and preparation of micromachined structures in combination with the back-end process of the pyroelectric active capacitor structure are presented.

Modelling of residual stress development in electronic materials and devices

Residual stresses in laterally structured thin films for microelectronic applications cause local stress concentrations in the substrate material near the film edges. Spatially resolved measurements of these stress concentrations with a resolution of about 1 micron are possible by means of optical spectroscopy. In the case of silicon Raman spectroscopy is applied. Raman spectroscopy has been used to analyse the stress state near edges of sputtered pyrosensor structures, in particular near the edges of Pt thin films, serving as bottom electrode, and near the edges of ferroelectric PZT films. The measured stress profile revealed that both the Pt and the PZT film are under tension.