RU2300824C1 - Integrated current-magnetic sensor incorporating light-emitting diode display - Google Patents

Abstract

FIELD: semiconductor electronics; magnetic field sensing semiconductor devices (bipolar structures).

SUBSTANCE: proposed current-magnetic sensor incorporating light-emitting diode display has semiconductor device responsive to magnetic field, as well as magnetic-field responsive loading and amplifying MOS transistors of bipolar double-collector type. Magnetic-field responsive base region of semiconductor device is isolated from substrate by diffusion pocket accommodating beyond-base-region contacts; highly doped contact regions are formed in substrate; substrate contacts and emitter are electrically interconnected and placed at equal potential. Loading and amplifying MOS transistors are disposed in separate pocket and function to transmit signals from magnetic-field sensing double-collector lateral bipolar transistor to light-emitting diode display.

EFFECT: reduced impact of device substrate currents onto integrated-circuit adjacent parts, reduced measurement error brought in by initial unbalance of transistor collector currents.

1 cl, 7 dwg

Description

The present invention relates to semiconductor electronics, semiconductor devices - bipolar structures with sensitivity to the influence of a magnetic field. Semiconductor sensors of magnitude and direction of the magnetic field are becoming more widespread in integrated microsystems due to the possibility of combining them with other components of microsystems using microelectronics methods and the creation of microminiature devices for monitoring and control in automated complexes for various purposes.

Among many types of semiconductor magnetosensitive elements of resistors, diodes, Hall sensors, bipolar and MOS two-collector transistors, a bipolar two-collector magnetosensitive transistor is of particular interest due to the possibility of obtaining high sensitivity and selectivity to the direction of the magnetic field.

In the article / 1 / and in the patent / 2 / a sensor is described that is sensitive to a three-dimensional magnetic field, implemented on magnetotransistors according to CMOS technology. Around the emitter in a common pocket are four pairs of collector areas and four base contacts. A useful signal in the form of collector current is obtained by applying a bias voltage to the substrate relative to the pocket.

The patent / 3 / proposes a sensor sensitive to a three-dimensional magnetic field. The device consists of Hall sensors that detect the three components of the magnetic field Bx, By, Bz and an electronic circuit. The rectangular crystals of the Hall sensors have an active region of one type of conductivity. Four current electrodes with an external connection of pairs of diagonally located electrodes are placed at the corners of this region. There are four potential electrodes on the sides of the rectangle. Potential electrodes are connected to the inputs of the compilers of the electronic circuit. By adding or subtracting potentials, the electronic circuit generates three signals proportional to the three components of the magnetic field.

Based on sensors sensitive to a magnetic field, compasses are created that allow you to determine the direction of the Earth's magnetic field and obtain data on the orientation and direction of motion of moving objects.

In the patent / 4 / a compass with a luminescent indication is proposed. The device includes a power source, a driver for the luminescent panel, a luminescent panel, a driver control panel, a voltage divider circuit, and an electronic compass module. The electronic compass module gives an orientation signal, which is transmitted to the driver and from it to the fluorescent panel. When a compass with a fluorescent display is installed on a car, information is obtained on the orientation and direction of movement of the car.

Patent / 5 / proposes a compass with a direction indicator. Using a satellite navigation system, a portable compass based on the receiver, decoder and small-sized display indicating the cardinal points is offered.

The closest analogue adopted by us for the prototype is a patent for an invention in which a magnetic field sensitive semiconductor device is proposed in the form of a lateral bipolar magnetically sensitive two-collector transistor containing a single crystal substrate, a deep pocket located inside the pocket of the contact area to the base, emitter, the first and second working collectors located outside the pocket - the first and second contacts to the substrate, the diffusion areas of the contacts to the base are located closer to Mitter than working collectors, the dimensions of the contact areas to the base are more or equal to the width and depth of the pocket, and the contacts to the base and the contacts to the substrate are connected to the same power source / 6 /.

The main disadvantage of this device is that, together with the injected electrons, holes penetrate the substrate, which create the interaction of elements in the integrated circuit. Transistors have a relatively large initial imbalance of collector currents. Their use as part of integrated circuits is difficult due to the imbalance of currents and the influence of substrate currents on neighboring elements of the integrated circuit.

The purpose of the invention is to reduce the influence of the substrate currents of the semiconductor device sensitive to a magnetic field on adjacent elements of the integrated circuit and to reduce the measurement error due to the initial imbalance of the collector currents of the bipolar two-collector magnetosensitive transistor.

The essence of the invention is to change the structure of the lateral bipolar magnetosensitive transistor by introducing into the substrate a pocket for separation from the substrate of the base layer in which the emitter and measuring collectors are formed, and introducing an operating mode with an electrical connection between the contacts to the emitter and the contacts to the substrate. Such a structure and operation mode create a predominant flow direction of the charge carriers injected from the emitter towards the contacts to the pocket, and those injected from the contact to the base of the charge carriers toward the contacts to the substrate. The charge carriers injected from the emitter in the pocket become the main carriers, and charge carriers of a different sign injected from the contact to the base become the main charge carriers in the substrate. In this case, the charge carriers injected into the substrate are the main ones and practically do not affect neighboring elements of the integrated circuit. The magnetic field affects the carrier fluxes of both signs and their recombination so that the sensitivity increases and the influence of the initial imbalance of collector currents decreases. Load and amplification r-channel MOS transistors are located in a separate pocket on the same substrate.

Figure 1 shows the cross-section of an integrated current-magnetic sensor, the topology of the planar structure of the device is shown in figure 2, the first electrical circuit for energizing an integrated current-magnetic sensor with an LED indicator is shown in figure 3, the second electrical circuit is shown in figure 4, Fig. 5 shows the dependences of the currents of the emitter, pocket, base, measuring collector in a semiconductor current-magnetic converter on the bias voltage between the base and the emitter, and Fig. 6 shows the dependences current sensitivity from the bias voltage of the base at several values of magnetic induction, Fig. 7 shows the dependences of the currents of the measuring collectors at the selected bias voltage of the base on the angle of rotation of the sensor in the horizontal plane.

The integrated current-magnetic sensor consists of a single-crystal substrate of the first type of conductivity (1)); a deep pocket (2) for MOS transistors, a deep pocket (3) for BMTs located on the surface of the substrate and having a low concentration of impurities, creating a second type of conductivity; base area (4) of the first type of conductivity located in the pocket (3); contacts (5), (11) to the pocket (3) in the form of regions with strong doping with an impurity that creates a second type of conductivity; areas of contacts to the base (7) and (9) located in the base (4), having a width and depth not less than the depth and width of the base and having strong alloying of the first type of conductivity; heavily doped regions of the second type of conductivity with a depth less than the depth of the base and located inside the base of the emitter (8), the first (6) and second (10) measuring collectors; the area of contact to the substrate (12) having strong doping of the first type of conductivity; contacts (13), (19) to the pocket (2) in the form of regions with strong doping with an impurity that creates a second type of conductivity; the drain of the load MOS transistor (14), the drain of the amplifier MOS transistor (18), the source of the load and amplifier MOS transistors (16) having strong doping of the first type of conductivity; gate of the load MOS transistor (15); the gate of the amplifying MOS transistor (17) (Figure 1).

Figure 2 shows the topology of the planar structure of an integrated tokomagnetic sensor, where the device consists of a single-crystal substrate of the first type of conductivity (1)); deep pocket (2) for MOS transistors, deep pocket (3) for BMT; base area (4) located in the pocket (3); contacts (5), (11) to the pocket (3); areas of contacts to the base (7) and (9) located in the base (4); areas of the emitter (8), the first (6) and second (10) measuring collectors located inside the base; the area of contact to the substrate (12); contacts (13), (19) to the pocket (2); sinks of load MOS transistors (14), (20), drain of amplification MOS transistor (18), source of load and amplification MOS transistors (16); gate load MOS transistors (15); MOS transistor gate (17).

Figure 3 shows the electrical circuit voltage, where the power supply Epit is supplied to the sources of the MOS transistors RMOP1, RMOP2, RMOPZ and the voltage divider R1, R2. The effluent of the load MOS transistors RMOP1, RMOP2 are connected to the measuring collectors K1 and K2 of the semiconductor current-magnetic converter. The gates of the load MOS transistors RMOP1, RMOP2 are connected to each other and to the measuring collector K1 of the semiconductor current-magnetic converter. The gate of the amplifying transistor RMOPZ is connected to the measuring collector K2 and the drain of the load MOS transistor RMOP2. The drain of the amplifying MOSFET transistor RMOPZ is connected to the LED LED. The midpoint of the voltage divider R1, R2 is connected with the contacts to the base B1, B2 and with the contacts to the pocket QC. The voltage divider provides the task of the bias voltage of the base Ub relative to the common point to which the emitter E of the semiconductor current-magnetic converter is connected, contact to the substrate P, the second output of the LED LED and the voltage divider R1, R2. Load RMOS transistors are included according to the current mirror circuit.

In Fig. 4, a second voltage switching circuit is given, which differs from the first circuit in that the load transistors RMOP1, RMOP2 are connected in parallel and have the form of field diodes with a gate and drain connection.

Figure 5 shows the dependences of the currents of the emitter Ie, pocket Ib, base Ib, measuring collector Ic in a semiconductor current-magnetic converter on the bias voltage between the base and emitter Ube in the range from 0.6 to 1.0 V. A rapid increase in the current of the measuring collector begins after response threshold Ube = 0.77 V.

Fig. 6 shows, for a particular device, the dependences of the relative current magnetosensitivity Sr = (Ic1-Ic2) / (Ic1 + Ic2) V, 1 / T on the bias voltage of the base Ube in the range from 0.78 to 1.0 V at magnetic induction 3, 9, 17, 33, 60, 120, 180 mT of a uniform magnetic field in an electromagnet. For small values of the bias voltage between the emitter and the base, the current of the left collector is less than the current of the right collector, therefore, the relative magnetosensitivity has a negative sign, and changes in magnitude and reaches 7 T ^-1 in a weak magnetic field. With large bias voltages between the emitter and the base, the current of the left collector is greater than the current of the right collector, therefore, the relative magnetosensitivity has a positive sign.

In Fig. 7, for a particular device, the dependences of the currents of the measuring collectors Ic1, Ic2 are given for a base bias voltage of Ube = 0.78 V and a rotation of the sensor in the horizontal plane 360 degrees in an inhomogeneous weak magnetic field. The change in the magnitude of the collector currents in this case is greater than their relative difference.

Figure 3 is a diagram of the voltage on the integrated tokomagnetic sensor. The contacts to the base and to the pocket are electrically connected, which ensures the absence of bias voltage at the base-pocket pn junction. In the absence of an external electric field, this structure determines the diffusion mechanism of the flow of current carriers injected from the emitter through the base into the pocket. In the base and in the pocket, the injected current carriers in the semiconductor volume recombine with current carriers of a different sign, arising from contacts to the base and diffusing in the base, in the pocket, and in the substrate, ensuring electroneutrality in the semiconductor volume by compensation of charge carriers of different signs. Thus, the volumetric nature of the processes in a semiconductor current-magnetic converter practically eliminates the dependence of the parameters of the device on the state of the surface of the device.

The electrical connection between the emitter and the contacts to the substrate provides bias voltage to the substrate-pocket pn junction in the closed direction. The electric field at the closed pn junction of the substrate-pocket helps the holes to overcome the transition and leave the pocket into the substrate, at the same time restricting the movement of electrons into the substrate. The separation of electrons and holes reduces the effect of excess carriers in the substrate on neighboring elements of the integrated circuit.

The sensitivity mechanism is determined by the distribution of electron and hole concentrations and their recombination in the bulk. In a magnetic field under the action of the Lorentz force, a change occurs in the position of streamlines, the concentration of electrons and holes and, accordingly, their recombination rate. This is the concentration-recombination mechanism of magnetic current sensitivity.

Changing the current lines leads to a change in the currents of the measuring collectors, one of them increases, the other decreases. In this case, the circuit of the current mirror on the load transistors, presented in figure 3, allows to obtain a large gain signal voltage. Further, this voltage is supplied to the gate of the amplifying transistor, which is larger than the load transistors. A change in current in the amplifying transistor leads to a change in the current of the LED, which determines its glow. Thus, a change in the magnetic field is indicated by the strength of the LED.

Figure 4 is a diagram of the voltage on the integrated tokomagnetic sensor when the current of the measuring collectors exceeds their relative change. In this case, the load transistors are connected in parallel and a voltage change occurs on them when the total current of the two measuring collectors changes. This eliminates the influence of the initial unbalance of the currents of the measuring collectors on the measurement accuracy.

The current of the measuring collector near the threshold is less than the emitter current by several orders of magnitude (Fig. 5). The Lorentz force is proportional to the magnitude of the current, so the deviation of the charge carrier flows from the emitter current can create a much larger change in current in the measuring collector than a change in the initial collector current in a magnetic field. Therefore, the semiconductor current-magnetic sensor near the threshold has a high current sensitivity.

As follows from Fig.6, a semiconductor current-magnetic Converter has a high current sensitivity in weak magnetic fields. The current sensitivity changes its value and sign with increasing bias voltage, i.e. with an increase in injection level.

Figure 7 shows how the currents of the measuring collectors depend on the selected bias voltage and rotation of the sensor in an inhomogeneous weak magnetic field available in laboratory conditions. The change in the magnitude of the collector currents in this case is greater than their relative difference, therefore, for such conditions, a second switching circuit is used (Fig. 4).

For definiteness, we assume that the substrate is silicon and has p-type conductivity. The manufacture of the device begins with the formation of pockets of n-type conductivity using photolithography, ion doping and thermal distillation, then using the same technological processes, p-type conductivity regions of the base, gate oxide, polysilicon gate, highly doped contacts to the base and substrate are formed, the sources , drains of RMOS transistors and the fabrication process is completed by the formation of heavily doped n-type regions of conductivity of contacts to the pocket, emitter, and measuring collector in. To provide an electrical connection, a dielectric layer of silicon oxide is applied to the surface of the device, contact windows to all areas and aluminum wiring with contact pads are formed.

Voltage is applied to the terminals of the device: positive voltage relative to the emitter and the substrate is applied to the base contacts and contacts to the pocket, and positive voltage from the power source is supplied to the collector terminals through load-carrying RMOS transistors and a voltage divider. The output current of the amplifying RMOS transistor determines the intensity of the LED glow. The luminous intensity is visually fixed during rotation of the sensor and the maximum intensity corresponds to the maximum value of magnetic induction. In the case of measuring the Earth's magnetic field, the maximum induction corresponds to the north-south direction.

An integrated current-magnetic sensor with an LED indicator allows you to get a microminiature device to determine the direction of the magnetic field. The parameters of the device are determined by the bulk properties of the semiconductor and depend little on the state of the surface of the device, which determines its high stability and reproducibility during manufacture.

Information sources

1. Ristic Lj., Doan M.T., Paranjape M. / 3-D magnetic field sensor realized as a lateral magnetotransistor in CMOS Technology // Sensor and Actuators, A21-A23, 1990.

2. US patent 5323050.

3. US patent 6278271.

4. US patent 6742270.

5. US patent 6292137.

6. RF patent 2239916 - prototype.

Claims (1)

An integrated current-magnetic sensor with an LED indicator, consisting of a lateral bipolar magnetically sensitive two-collector transistor on a single-crystal substrate of the first type of conductivity, with a base region on the surface of the substrate having a low concentration of impurities and a second type of conductivity, located in the base region are heavily doped regions of the emitter, the first and second working collectors of the first type of conductivity with a depth less than the depth of the base region, the area of contacts to the base, located closer to the emitter than the collectors, and having a depth not less than the depth of the base region, and a length not less than the width of the base region, the first and second contacts located outside the base region, connected to the contacts to the base region and connected to the same voltage source characterized in that the base region is separated from the substrate by a diffusion pocket, heavily doped contact areas are formed in the substrate and pocket, the contacts to the substrate and the emitter are electrically connected with the same potential, load f and amplifying MOS transistors for transmitting a signal from a lateral bipolar magnetically sensitive two-collector transistor to an LED indicator are located in a separate pocket.

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