H. Blanchard, Ch. Schott This project was presented at the Hanover Trade Fair 1998 toghether with our industrial partner SENTRON AG, Zug, Switzerland as one of the award winning projects of "Location Switzerland" in order to present the latest achievements of high-tech R&D in Switzerland !

Silicon Hall probes, or sensors, are widely used. In industry they can be found in contactless switches, position indicators, meters as well as in systems for the measurement of speed and rotation. In the automobile Hall sensors can be found in systems such as : ABS, speed meter, electric windows, control systems for doors, headlights, the engine and the gear box. Many Hall probes can be found in home appliances, domestic electronics and computers.

There exists a real need for very high detectivity sensors, which are both compact and economic to use. A current means of increasing the detectivity of a Hall sensor is to use magnetic flux concentrators (Fig. 1).

Fig. 1: Macro-Flux-Concentrators used in industry

However they take a large space and are expensive, often costing more than the sensor itself.

The main innovation of our product is to use low cost integrated flux concentrators where the technology required for their integration is compatible with microelectronic integration processes. The concentrators are integrated directly onto the silicon wafer alreay containing thousands of Hall sensors and the wafer is then cut into single Hall probes (Fig. 2) which are then packaged like standard integrated circuits (Fig. 3).

Fig. 2 : Cylindrical Hall device with integrated flux concentrators

Fig. 3 : The sensor in a package for standard integrated circuits

The unit cost for the integration of the concentrators is only a quater of the price of the sensor whereas the equivalent detectivity of the sensor is multiplied by five. The active area of our Hall sensor has a cylindrical shape. The makes it very suitable for measuring the circular field under the air gap between two magnetic flux concentrators (Fig. 4).

Fig. 4 : The cylindrical Hall device measures the circular field under the airgap between the two flux concentrators

These magnetic flux concentrators are made of ferromagnetic sheet metal which is glued on the wafer. The desired shape is obtained by using classic microelectronic processing (photolithography and chemical etching). This innovation opens new horizons : Since the sensor is produced using the same technology as for integrated electronic circuits, we will be able to implement a complete integrated system including sensor and signal processing electronics. The integration technology for ferromagnetic layers opens new possibilites in the area of magnetic sensors: we are currently working on different projects using two and three dimensional Hall sensors, magnetic 'choppers' and 'fluxgates'.

Datasheet Cylindrical Hall Device