MICROSYSTEMS WITH INTEGRATED CAPACITIVE, MAGNETIC AND OPTICAL SENSORS Albin Pevec, Janez Trontelj University of Ljubljana, Faculty of Electrical Engineering, Ljubljana, Slovenia POSVET O SENZORJIH V ZAVODU ITC SEMTO 15.03.2002, FE Ljubljana Key words; integrated sensors, Hall sensors, optical sensors, capacitive sensors Abstract: This article discusses microsystems with integrated sensors for measuring various physical values like acceleration, electrical current and motion. An integrated microsystem is presented for all three physical values. These microsystems are composed from the integrated sensor and the processing electronics all on the same silicon die. The emphasis of this article is on the presentation of the integrated sensors. Mikrosistemi z integriranimi kapacitivnimi, magnetnimi in optičnimi senzorji Ključne besede: integrirani senzorji. Hali senzorji, optični senzorji, kapacitivni senzorji Izvleček: Članek obravnava mikrosisteme z integriranimi senzorji za merjenje fizikalnih veličin kot so pospešek, električni tok in gibanje. Za vsako veličino je predstavljen integrirani mikrosistem, ki je sestavljen iz senzorjev in obdelovalne elektronike, ki sta integrirani na istem silicijevem substratu. Poudarek članka je na predstavitvi integriranih senzorjev. 1. INTRODUCTION We are witnessing an extreme advent in tlie computer and communication technology. In contrast to these advances the possibility to gather and process information from the Sensor Iprim Isec N-turns B=0 => Iprim = N'Isec Fig. 1: Closed loop current measuring system physical world lags behind. Great advances in this area are possible with the development of integrated microsystems. These are physical value measuring systems which combine the sensor and the processing electronics on the same silicon die. Three various microsystems are presented in this article: magnetic microsystem with integrated Hall sensors for electrical current measurement capacitive microsystems with micromechanical sensor for acceleration measurement optical microsystem with integrated photo diodes tor displacement measurement All three microsystems can replace the traditional discrete sensor and electronics systems and therefore reduce the cost and the area of the measurement system. 2.1 Magnetic microsystem with integrated hall sensors The Hall magnetic sensors are compatible with the standard CMOS process therefore they can be easily integrated with the use of the n-well layer. The inherent characteristic of the Hall sensor can be largely improved with various techniques as the current spinning, bias current compensation, use of spatially distributed Hall sensors etc. In the presented system a Hall sensor array is used for measuring the electrical current through the primary coil. This current generates a magnetic field sensed by the microsystem which also drives the secondary coil. The system is in a closed loop configuration and therefore the microsystem with the use of the secondary coil zeroes the magnetic field in the core. The current through the secondary coil is proportional to the primary current. The advantage of the closed loop system is the galvanic separation and high bandwidth (200kHz) of such a system. An example of such a system is on fig.1. The magnetic sensors, processing electronics and the current driver amplifiers are all on the same silicon die (fig.2). Riiig for holding ll>e two dies Console from polysislicon serving as capacitive plate and sensing elctrtent Bond v. Actiiafor capacitor plate Sensing capacitor plato Fig. 3: Capacitive microsystem cross-section ; ' —fill_II_n : ^ iHtlBIIBiÄÄ^ÄBII aiiii " M ■ ii«fil|i Fig. 2: Die plot with the marl