A current sensor for detecting a magnetic field generated by current, a angle sensor for detecting rotational angle of a magnet, a position sensor for detecting displacement of a magnet, and the like have been known as magnetic-sensor semiconductor integrated circuit having Hall elements built therein.
It is known that magnetic sensitivity of Hall element varies depending on the temperature. Therefore, it is necessary to compensate the influence of the temperature in order to compensate the magnetic sensitivity of the Hall element with high accuracy. Furthermore, it is known that the magnetic sensitivity of the Hall element varies depending not only on the temperature effect but also on the mechanical stress effect (Piezo-Hall Effect).
FIG. 1 is a cross-section view of a package structure in which a semiconductor integrated circuit of a magnetic sensor is encapsulated. The package structure includes a semiconductor integrated circuit 3 of the magnetic sensor on a lead frame 1, a Hall element 2 incorporated into the semiconductor integrated circuit 3, and a molding resin 4 surrounding the semiconductor integrated circuit 3. In this package structure, since thermal expansion coefficients of silicon, the lead frame 1, the resin 4, and the like are different from one another, mechanical stress occurs at several positions including the surface of the silicon. Furthermore, the mechanical stress varies due to the change in temperature and humidity of the operating condition. Accordingly, there is a problem in that the magnetic sensitivity of the semiconductor integrated circuit of the magnetic sensor varies depending on the operating condition.
In order to address such a problem in that the magnetic sensitivity of the semiconductor integrated circuit of the magnetic sensor varies depending on the operating condition, for example, PTL 1 discloses that a change of the mechanical stress is detected by using a change of an offset of the Hall element in order to compensate the magnetic sensitivity.
Furthermore, PTL 2, for example, discloses that the change of the mechanical stress is detected by using a change of a resistance value of the Hall element (Hall resistance value) in order to compensate the magnetic sensitivity by feeding back the detection result of the mechanical stress to a drive current of the Hall device (Hall drive current).
Further, PTL 3 to PTL 5, and NPL1, for example, disclose that a mechanical stress detection element other than the Hall element is utilized in order to compensate the magnetic sensitivity on the basis of the mechanical stress detection result.
Further, PTL 6, for example, discloses a method of reducing the mechanical stress applied to the Hall element by improving a package material or a package structure.
Further, in order to address a problem in that the magnetic sensitivity of the Hall element varies depending on temperature, for example, PTL 7 discloses that the magnetic sensitivity is compensated by use of a one-chip microcomputer controlling a power supply voltage of the Hall element.
USPTO Backgrounds
USPTO Backgrounds