RU2122258C1 - Magnetic-field vector sensor - Google Patents

Abstract

FIELD: magnetic- field sensing semiconductor devices such as digital sensors or sensing elements of magnetic- field controlled integrated circuits. SUBSTANCE: sensor is, essentially, structure of two bipolar n-p-n magnetic transistors integrated into four-collector bipolar magnetic transistor and double-drain MOS magnetic transistor. Electrode of MOS magnetic transistor gate is provided with ports giving access to contact regions of MOS transistor current contacts, collector and emitter regions, and region of contact for base of four-collector bipolar magnetic transistor, their sizes being not less than those of ports; side insulation over perimeter of ports in gate electrode has its edges aligned with those of respective contact ports; low-resistance region of second polarity of conductivity is made between external edge of MOS transistor gate electrode and closest edge of insulation section, its width being not less than distance between these edges. Sensor body depends only on configuration of gate electrode irrespective of precision of process equipment and accuracy of relative alignment of configuration layers. EFFECT: reduced output signal at zero magnetic field. 1 dwg

Description

 The invention relates to semiconductor magnetically sensitive devices and can be used to measure magnetic fields in the form of a discrete sensor or as a sensitive element in magnetically integrated integrated circuits.

 Known designs of magnetic field vector sensors, using a bipolar two-collector magnetotransistor as an element of a magnetic field vector sensitive to the component of the magnetic field perpendicular to the crystal surface [1]. The main disadvantage of these sensors is their low sensitivity to the component of the magnetic field vector perpendicular to the surface of the crystal, compared with sensitivity to the two components of the magnetic field vector parallel to the surface of the crystal. In addition, cross-sensitivity occurs in these sensors.

 The closest in technical essence is the sensor of the magnetic field vector described in [2]. The sensor consists of two bipolar magnetotransistors integrated in a four-collector magnetotransistor, and a two-line MOS magnetotransistor. The four-collector bipolar magnetotransistor is sensitive to two components of the magnetic field vector parallel to the surface of the crystal, and the two-line MOS magnetotransistor is sensitive to the perpendicular component. Compared with other sensors of the magnetic field vector, the presented sensor has a rather high sensitivity to the perpendicular component of the magnetic field vector. The use of a two-line MOS magnetotransistor allows you to practically get rid of cross sensitivity. The disadvantage of this design is that the relative positions of the emitter and collectors of the bipolar magnetotransistor and the current regions of the MOS magnetotransistor, as well as their sizes are determined by several photo masks and during the manufacturing process they are misaligned relative to each other, which leads to asymmetry of the structure and, therefore, to the presence of a nonzero difference output currents in the absence of a magnetic field (initial current imbalance). This leads to a decrease in the precision of the sensor.

 Using the proposed technical solution will increase the precision of the magnetic field vector sensor. For this, it is necessary, first of all, to reduce the initial imbalance of currents. A significant contribution to the magnitude of the initial current imbalance is made by the asymmetry of the structure obtained in the process of manufacturing sensors. To solve the problem of reducing the difference in the output currents of the magnetically sensitive element associated with the asymmetry of the structure obtained due to misregistration of the topological layers during the formation of the magnetically sensitive structure, we propose a structure containing a region of the first conductivity type in a semiconductor wafer of the second type of conductivity, in which a base region of the second conductivity type is formed , windows are made in the gate electrode, under which the contact areas of the current contacts of the MOS magnets are formed a transistor and collector regions, an emitter and a contact to the base of a four-collector bipolar magnetotransistor, having dimensions not less than window sizes, lateral dielectric insulation is located around the window perimeter, the edge of which coincides with the edges of the contact windows to these areas, and between the outer edge of the gate electrode of the MOS magnetotransistor and nearby a low-resistance region of the second type of conductivity with a width of at least the distance between these edges is made to it by the edge of the dielectric insulation section. In this case, the relative position of the emitter and the collectors of the bipolar magnetotransistor and the current areas of the MOS magnetotransistor is determined only by the configuration of the gate electrode, regardless of the precision of the process equipment and the accuracy of combining the topological layers with respect to each other. Thus, it is possible to avoid the occurrence of an initial imbalance of currents in the process of manufacturing sensors associated with the misregistration of topological layers relative to each other.

 For definiteness, in what follows, we will consider the first type of conductivity to be electronic, and the second to hole.

 One of the possible topologies of the proposed magnetic field vector sensor is shown in the drawing, where 1 is a semiconductor wafer of the second type of conductivity, 2 is the diffusion region of the first type of conductivity, 3 is dielectric insulation, 4,5 are the contact areas of the current contacts of the n-MOS magnetotransistor, 6 - gate electrode, 7 - gate dielectric, 8 - low-resistance region of the second type of conductivity, 9 - current contacts, 10 - lateral dielectric insulation, 11,12 - windows in the gate electrode to the contact areas of the current contact in the n-MOS magnetotransistor, 13 is the edge of the dielectric isolation section, 14 is masking oxide, 15 is the emitter region, 16, 21, 22 are the windows in the gate electrode to the emitter regions, the contact areas of the collector contacts and the contact areas of the side contacts, 17 is the region bases of the second type of conductivity, 18, 19, 20 — contact areas of contacts to the base and collectors.

 In the semiconductor wafer of the second type of conductivity 1, a region of the first type of conductivity 2 and four contact areas of the collector contacts 19, 20 of the first type of conductivity are surrounded by dielectric insulation 3, inside which four contact areas of the contacts to the base 18 of the second type of conductivity and the emitter region 15 of the first type of conductivity. Nearby is a region of the second type of conductivity (substrate) 1, surrounded by a dielectric insulation 3, inside which two contact areas of current 4, 5 contacts of the first type of conductivity are formed. A gap electrode 6 located on the gate dielectric 7 is formed above these regions. Windows 11, 12, 21, 22 are made in the gate electrode 6, under which the contact regions of the current contacts of the n-MOS magnetotransistor 4, 5, and the emitter region 15, the contacts to base 18, collector contacts 19, 20 of a bipolar four-collector magnetotransistor having dimensions not less than the sizes of the windows in the gate electrode, lateral dielectric insulation 10 is made along the perimeter of the windows, the edges of which coincide with the edges of the contact windows to the data on areas, and between the outer edge of the gate electrode of the n-MOS magnetotransistor and the adjacent edge of the dielectric insulation portion 3, a low-resistance region of the second conductivity type 8 is made with a width of at least at least the distance between these edges.

 Consider the principle of operation of the magnetic field vector sensor. Two-string n-MOS magnetotransistor operates as follows. When a positive voltage (higher than the threshold voltage) is applied to the gate electrode 6 on the silicon surface of the second type of conductivity 1, a thin, conductive channel of the first type of conductivity is induced under the gate insulator 7. When a positive voltage is applied between current contacts 4,5, an electron current flows through the channel. In the absence of a magnetic field, the sink currents are equal, since the structure is symmetrical. When a magnetic field arises perpendicular to the surface of the crystal, the electrons moving under the influence of an electric field from source 4 to sinks 5 are affected by the Lorentz force, which deflects them to one or another sink, depending on the direction of the magnetic induction vector. As a result, the current of one drain increases and the other decreases. The difference of the drain currents is proportional to the value of the perpendicular component of the magnetic induction vector. A bipolar four-collector n-p-n magnetotransistor operates as follows. A positive voltage relative to the emitter 15 is applied to the contacts to the collector 19, 20. A positive voltage above 0.7 V is applied to the contacts to the base 18 relative to the emitter 15, due to which electrons are injected from the emitter into the base 17, which partially recombine in the base and partially flying through the base, they fall into the area of collector 2, redistributed between the four contact areas to the collector 19, 20. In the absence of a magnetic field, the collector currents are equal, since the structure is symmetrical. Under the action of a magnetic field parallel to the surface of the crystal, under the action of the Lorentz force, the currents of the collectors are redistributed in the region of the collector 2. The magnitude of the change in the currents of the collectors of the sensor determines the magnitude of the induction and the direction of the magnetic field vector.

 The proposed magnetic field vector sensor can be manufactured using standard n-pocket CMOS integrated circuit technology with the addition of a single photolithography. Simultaneously with the sensor on one chip, a signal processing circuit can be obtained. Therefore, on the basis of the proposed sensor, high-precision magnetically sensitive circuits can be implemented that can be used in flaw detectors of magnetic materials to measure the magnetic field of the Earth, etc.

Sources of information
1. S. Kordic and PJA Munter, "Three-dimensional magnetic-field sensors", IEEE Transactions on Electron Devices, Vol. 35, No. 6, June 1988, pp. 771-779.

 2. Durgamadhad Misra and Bingda Wang, "Elimination of cross sensitivity in a three-dimensional magnetic sensors", IEEE Transactions on Electron Devices, Vol. 41, April 1994, pp. 622-624. - prototype.

Claims (1)

 A magnetic field vector sensor consisting of two bipolar npn magnetotransistors integrated in a four-collector bipolar magnetotransistor and a two-line MOS magnetotransistor, characterized in that windows are formed in the gate electrode of the MOS magnetotransistor, under which are formed contact areas of the magnetotransistor contacts and MOS contact to the base of the four-collector bipolar magnetotransistor, having dimensions not less than the size of the windows, and along the perimeter of the windows put lateral dielectric isolation, the edges of which coincide with the edges of the contact holes to these areas, and not less than the distance between the edges between the outer edge of the gate electrode of MOS magnetotransistor thereto and surrounding the edge portion of the dielectric isolation region is made low-impedance of the second conductivity type in width.