RU2550756C1 - Three-collector bipolar magnetotransistor with orthogonal flows of charge carriers - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: three-collector bipolar magnetotransistor with orthogonal flows of charge carriers contains a silicon single-crystal substrate, base area on the substrate surface with small concentration of impurities, heavily doped emitter areas, the first and the second measuring collectors with the depth less than the depth of the base area and located in base area, the area of heavily doped contacts to the base, the diffusive pocket which separates the base area from the substrate and is the third collector, heavily doped contacts to the pocket and to the substrate. Contacts to the pocket are connected by metallization to contacts to the base, contacts to the substrate are connected by metallization to contacts to the emitter, areas of the emitter and collectors are located near the base at a distance from each other, contacts to the pocket are located in the pocket near p-n junction boundary base-pocket opposite to measuring collectors, the emitter has identical length with the measuring collectors, heavily doped contacts to the base are located end-to-end with end faces of the strip emitter with the orthogonal direction between the emitter and contact to the base with reference to the direction between the emitter and measuring collectors.

EFFECT: enhancement in sensitivity of magnetic field parallel to crystal surface.

5 dwg

Description

The present invention relates to semiconductor electronics, semiconductor devices - bipolar structures with sensitivity to the influence of a magnetic field. Magnetic field magnitude and direction sensors convert magnetic field induction into an electrical signal and find wider application due to the possibility of creating them on a single chip with a subsequent signal processing circuit, as well as integration into elements of microsystem technology.

The lateral (lateral) transistor with the location of the electrodes of the collectors, emitter, and contacts to the base on the crystal surface provides high sensitivity / 1 /. This device consists of a pair of lateral transistors with a common emitter. It is essential for the operation of the device that the charge carrier flows injected from the emitter flow to two collectors in opposite directions. It was experimentally established that magnetosensitivity is determined by a change in the emitter-collector current transfer coefficient between the emitter and the collectors in an external transverse magnetic field. Magnetoconcentration phenomena are understood as a change in the concentration of injected carriers due to surface recombination at the base length in a magnetic field that presses carriers to the surface on one side of the emitter and pushes the carriers away from the surface on the other side of the emitter. This effect gives a nonlinearity in the change in current of each collector depending on the magnitude of the magnetic field at large distances between the emitter and the collectors. The collector current difference has a linear dependence on induction. The magnitude of the magnetoconcentration effect depends on the parameters of the base material, on the ratio of the length of the base to the diffusion length of minority charge carriers and on the rate of surface recombination. The relative current sensitivity was 1.9 T ^-1 . The magnetosensitivity with the magnetoconcentration effect is much greater than in the deflection effect. The disadvantages of the device include the lack of isolation of the active part of the device from the substrate. Injected charge carriers pass unhindered into all areas of the crystal, which affects other elements of the integrated circuit.

In US Pat. No. 2, a magnetic field sensor in the form of a lateral bipolar two-collector magnetotransistor is formed in a diffusion pocket on the surface of a silicon substrate of a different type of conductivity than a pocket. The electrodes are located on the surface of the pocket in the following order: in the middle is an emitter, collectors on the left and right, then contacts to the base on the left and right. The reverse bias is applied to the pn junction between the substrate and the pocket with the help of additional contacts to the substrate, which should provide isolation of the transistor from other elements of the integrated circuit. The relative current sensitivity of the sensor is approximately 1 T ^-1 . The main role in the redistribution of charge carriers is played by the modulation of injection as a result of potential changes at the left and right boundaries of the emitter pn junction under the action of the Lorentz force in a magnetic field. This device is sensitive mainly to a magnetic field directed along the surface of the crystal. The disadvantage of the sensor is that the current of the injected charge carriers penetrates through the pocket-substrate transition, therefore, the pocket-substrate transition does not provide sufficient isolation of the device.

The closest analogue adopted for the prototype is the RF patent for the invention / 3 /, which proposes a semiconductor magnetic transducer in the form of a lateral bipolar magnetically sensitive two-collector transistor containing a silicon single crystal substrate; a base region on a substrate surface having a low impurity concentration; heavily doped areas of the emitter, the first and second measuring collectors with a depth less than the depth of the base region and located inside the base region; areas of heavily doped contacts to the base; a diffusion pocket separating the base region from the substrate and in which there are heavily doped contacts; contacts are formed in the substrate, which are electrically connected to the contacts to the emitter with the same potential supply. A pn junction is formed between the pocket and the substrate, which protects the device from the currents of other elements included in the integrated circuit. The device is most sensitive to magnetic induction with a vector directed along the surface of the crystal and along the long side of the strip electrodes of the emitter and collectors. The relative current sensitivity for magnetic induction directed parallel to the surface of the substrate is 4.5 T ^-1 . With the strip geometry of the emitter and collectors equidistant from the emitter, the sensitivity to a magnetic field directed perpendicular to the surface of the substrate is practically zero.

The objective of the invention is a three-collector bipolar magnetotransistor with orthogonal flows of charge carriers is to increase the sensitivity and reduce the initial imbalance of the semiconductor magnetic transducer to magnetic induction directed parallel to the surface of the crystal.

The problem is solved due to the fact that in a three-collector bipolar magnetotransistor with orthogonal flows of charge carriers, significant differences from the prototype are provided. The emitter and collector regions in the form of stripes are located in the base region at a distance from each other. The contact windows to the emitter and the measuring collectors are also in the form of strips. Heavily doped contact areas to the base are end-to-end with the ends of the strip emitter. The mutual arrangement of the heavily doped contact areas to the base and the emitter creates the emitter-base current flowing in one direction, and the mutual arrangement of the emitter and the measuring collectors creates the collector current in the orthogonal direction. The difference of the collector currents in the magnetic field corresponds to the measured component of the magnetic induction vector, parallel to the surface of the crystal, and determines the sensitivity. The flow of currents between heavily doped contacts to the base and the emitter perpendicular to the currents between the measuring collectors and the emitter eliminates the coincidence of currents in space and reduces the initial imbalance of the currents of the measuring collectors, arising from the imbalance of currents between the heavily doped contacts to the base and the emitter.

Between the totality of the essential features of the claimed object and the achieved technical result, there is a causal relationship, the p-n-base-pocket junction is located closer to the emitter and serves as the third collector. A larger stream of charge carriers injected from the emitter flows into the third collector than into the measuring collectors. The currents between two heavily doped contacts to the base and the emitter are large in comparison with the currents of the measuring collectors and are not equal to each other. The sequential arrangement of the emitter, the contacts to the base and the measuring collectors leads to the imposition of the currents of the emitter-base and emitter-measuring collectors. With the initial imbalance of currents of heavily doped contacts to the base and emitter, a sequential voltage drop occurs in the space between the emitter and the measuring collectors, which affects the initial imbalance of currents of the emitter-measuring collectors. The flow of charge carriers between heavily doped contacts to the base and the emitter in the common region of the base with carrier flows between the measuring collectors and the emitter leads to an imbalance in the initial currents of the measuring collectors. The orthogonal arrangement of heavily doped contacts to the base and collectors relative to the emitter eliminates the mutual influence of the currents of heavily doped contacts to the base-emitter on the initial imbalance of currents of the measuring collectors.

Under the influence of magnetic induction directed perpendicular to the flows of charge carriers injected from the emitter, an asymmetric change in the distribution of flows occurs under the action of the Lorentz force. More flow flows into one measuring collector, and less into another. Due to the parasitic initial imbalance of currents, the magnitude of the flows of the measuring collectors changes, which increases the sensitivity threshold of the magnetotransistor.

, которая определяется как изменение тока измерительных коллекторов I_K1(В)-I_K2(В) в магнитном поле с индукцией В при разбалансе начального тока коллекторов I_K1(0)-I_K2(0) относительно суммы начального тока коллекторов I_K1(0)+I_K2(0).The invention of a three-collector bipolar magnetotransistor with orthogonal flows of charge carriers makes it possible to lower the threshold of sensitivity of a semiconductor magnetic converter to a component of the magnetic induction vector directed parallel to the surface of the crystal. The device operates with a small initial imbalance, so the relative current sensitivity increases

, which is defined as the change in the current of the measuring collectors I _K1 (B) -I _K2 (B) in a magnetic field with induction B when the initial current of the collectors I _K1 (0) -I _K2 (0) is unbalanced relative to the sum of the initial current of the collectors I _K1 (0 ) + I _K2 (0).

Figure 1 presents a cross section of the volumetric structure of a three-collector bipolar magnetotransistor with orthogonal flows of charge carriers, where:

1 - heavily doped contact to the base of the first type of conductivity;

2 - emitter of the second type of conductivity;

3 - a single-crystal silicon substrate of the first type of conductivity;

4 - diffusion pocket of the second type of conductivity;

5 - measuring collector of the second type of conductivity;

6 - the base of the first type of conductivity.

The topology of a three-collector bipolar magnetotransistor with orthogonal flows of charge carriers is presented in figure 2, where the designation of the elements:

E - emitter;

K1 - measuring manifold first;

K2 - measuring manifold second;

B - heavily doped areas of contacts to the base;

I _BE - current direction between the base and the emitter;

I _KE - current direction between the measuring collectors and the emitter.

The scheme of changes in the magnetic field of the streamlines injected from the emitter of the charge carriers of a three-collector bipolar magnetotransistor with orthogonal flows of charge carriers is presented in figure 3, where:

1 - heavily doped contact to the base of the first type of conductivity;

7 - hole flow from a heavily doped contact to the base to the emitter;

8 - electron flow from the emitter to the base;

2 - emitter of the second type of conductivity;

3 - a single-crystal silicon substrate of the first type of conductivity;

9 - electron flow from the emitter to the measuring collector through the base region;

4 - diffusion pocket of the second type of conductivity;

10 - electron flow from the emitter to the measuring collector through the base-pocket p-n junction region;

5 - measuring collector of the second type of conductivity;

6 - the base of the first type of conductivity.

B is the magnetic induction vector directed parallel to the surface of the substrate;

J _h is the flow of charge carriers from the heavily doped contact to the base to the emitter;

J _eb — charge carrier flux from the emitter to a heavily doped contact to the base;

J _ec is the carrier stream of the measuring collector without a magnetic field;

dJ _ec — carrier flux of the measuring collector in a magnetic field;

J _ew is the flow of charge carriers passing from the flow of charge carriers to the third collector-pocket;

dJ _ew is an additional carrier stream of the measuring collector in a magnetic field, passing from the carrier stream to the third collector-pocket.

The voltage switching circuit for the electrodes of the device of a three-collector bipolar magnetotransistor with orthogonal flows of charge carriers in the composition of the sensors is made as shown in figure 4, where:

P - output from contact to the substrate;

K - output from contacts to the pocket;

B - output from contacts to the database;

E - output from the emitter;

K1 - output from the first collector;

K2 - output from the second collector;

U _EP - voltage on the emitter and the substrate;

U _BC - bias voltage at the base and on the pocket;

U _K1 is the voltage at the first collector;

U _K2 - voltage on the second collector.

и их отношения при величине магнитной индукции В=5 мТл при сопротивлении нагрузки коллекторов 219 кОм.Figure 5 is given for a particular device of a three-collector bipolar magnetotransistor with orthogonal carrier currents depending on the emitter current I _{E of the} initial voltage unbalance of the measuring collectors U _K1 (0) -U _K2 (0), the absolute voltage sensitivity

and their relationship with a magnetic induction of B = 5 mT with a collector load resistance of 219 kOhm.

The volume cross-section of the structure of a three-collector bipolar magnetotransistor with orthogonal carrier flows shown in Fig. 1 shows that a diffusion pocket of the second conductivity type 4 and a base layer of the first conductivity type 6 are formed in a single-crystal substrate of the first conductivity type 6. On the surface of the substrate, a heavily doped form contact to the base of the first conductivity type 1, emitter of the second conductivity type 2, measuring collector of the second conductivity type 5. Hole flow k from a heavily doped contact to the base flows into the emitter. From the emitter, an electron stream flows into a heavily doped contact to the base and into the measuring collector through the base region, as well as through the base-pocket pn junction region. A feature of the structure is the mutually orthogonal directions of the flow of currents, a heavily doped contact to the base-emitter and a measuring collector-emitter.

Three topological configurations in figure 2 show the difference in the location of the electrodes.

A. Usually accepted topology with a sequential arrangement of electrodes of the E - emitter, K1 and K2 - measuring collectors, B - heavily doped contact areas to the base. In this case, the I _BE - the direction of the current between the base and the emitter coincides with the I _CE - the direction of the current between the measuring collectors and the emitter. Overcurrents occur.

B. Topology with the location of heavily doped contact areas to the base near the ends of the emitter strip.

B. Topology with the location of heavily doped contact areas to the base near the ends of the emitter strip. There are two contacts along the edges of the emitter strip, with the size of more than the strips of collectors. Highly doped contact areas to the base cover the ends of the emitter, protruding beyond the dimension of the strips of the collectors.

In topological configurations B, the current direction between the base and emitter of _BE I orthogonally to the direction between the current collectors and the emitter measuring I _TBE.

. На потоки между эмиттером и сильнолегированными контактами к базе Jeb(B), Jh(B) магнитная индукция, направленная параллельно токам, не действует.A diagram of a change in a magnetic field with induction In the current lines of the injected charge carriers from the emitter of a three-collector bipolar magnetotransistor with orthogonal flows of charge carriers is shown in FIG. 3. Without a magnetic field, the hole flux Jh from the heavily doped contact to base 1 induces from the emitter 2 flows of injected charge carriers Jeb (0) + Jec (0) + Jew (0), which pass to the heavily doped contact to base 1 and to the measuring collector 5 through the base and through the pn junction between base 6 and pocket 4. The magnetic induction vector B is directed parallel to the surface of the substrate and parallel to the long side of the strip electrodes. The flows of injected charge carriers Jec (B), Jew (B) flowing to the collector under the action of the Lorentz force deflect to the surface dJec (B), dJew (B) or move away from the surface, which leads to a change in the length of streamlines. In accordance with the action of two effects, the flow of the measuring collector increases or decreases, which determines the differential relative magneto-sensitivity for current of a three-collector bipolar magnetotransistor

. The fluxes between the emitter and heavily doped contacts to the base Jeb (B), Jh (B) are not affected by magnetic induction parallel to the currents.

In the composition of the magnetic field sensor circuit energization trehkollektornogo bipolar magnetotransistor orthogonal charge carrier flow is formed as follows (Figure 4), which contacts to the base B and K are supplied to the pocket base voltage bias and the pocket U _BK emitter relative to the substrate and contacts U _EPO . In accordance with the magnitude of the bias current of the base and pocket I of the _BC , the voltage of the power source and the load resistance of the measuring collectors K1 and K2, the potentials U _K1 , U _{K2 are} established on the collectors. A charge carrier current of one sign flows from the base contact to the emitter and a charge carrier of another sign is created due to injection from the pn junction of the emitter into the base. In the base, the injected charge carriers reach the measuring collectors and are extracted by them.

As can be seen in Fig. 5, with an increase in the emitter current, the initial unbalance value changes from a small positive value of 1 mV to minus 100 mV, and the voltage sensitivity increases to 11 V / T. At maximum sensitivity, the value of the ratio of imbalance and sensitivity is 7.7 mV / V / T or 7.7 mT. In [4], the magnetic field equivalent to imbalance at a given sensitivity is called offset, and for a magnetotransistor with suppression of lateral injection this parameter is determined to be ± 200 mT. In a three-collector bipolar magnetotransistor with orthogonal charge carrier flows, this parameter is much better.

The functioning of a three-collector bipolar magnetotransistor with orthogonal flows of charge carriers occurs as follows. In the absence of a magnetic field, the charge carriers injected from the emitter pass through the base and are evenly distributed between the measuring collectors and form equal currents of the working collectors I _K1 (0) and I _K2 (0). In a magnetic field, the carriers injected from the emitter are affected by the Lorentz force, which deflects the carrier stream to one side of the base relative to the middle of the emitter, and the carrier stream of a different sign deviates in the opposite direction, which causes an asymmetric distribution of current carriers in the base. The asymmetric distribution of carrier flows during extraction by measuring collectors causes asymmetries in the currents of these collectors. As a result, the difference in voltage drops at equal load resistances in the circuit of the measuring collectors is a function of the magnitude of the magnetic field acting parallel to the surface of the crystal.

Listed in figure 1, the structural elements of a three-collector bipolar magnetotransistor with orthogonal flows of charge carriers are made according to the CMOS technology of integrated circuits as follows.

1 - heavily doped contact to the base of the first type of conductivity;

2 - emitter of the second type of conductivity;

3 - a single-crystal silicon substrate of the first type of conductivity;

4 - diffusion pocket of the second type of conductivity;

5 - measuring collector of the second type of conductivity;

6 - the base of the first type of conductivity.

For definiteness, we assume that the single-crystal substrate 3 is silicon and has p-type conductivity. The manufacture of the device begins with the formation of the region of the diffusion pocket 4 of the n-type conductivity using photolithography, ion doping and thermal distillation. Then, using the same technological processes, p-type conductivity regions of the base 6 layer are formed, ohmic contacts are doped to base 1, to substrate 3. Fabrication of the structure continues by forming n-type conductivity regions of contacts to pocket 4, emitter 2, and measuring collector 5. For to ensure the connection of a planar bipolar magnetotransistor with an external electrical circuit of the integrated sensor, a dielectric layer of silicon dioxide is grown on the crystal surface, contact windows are formed to all areas and aluminum wiring. To reduce the effect of surface recombination on the flows of charge carriers injected from the emitter, the silicon-silicon dioxide interface has a low surface recombination rate, which is achieved by using chlorine-containing gases during the growth of silicon dioxide.

The above-described three-collector bipolar magnetotransistor with orthogonal flows of charge carriers is used to create magnetic field sensors for various purposes as follows. Voltage is applied to the terminals of the device: a positive bias voltage relative to the emitter is applied to the base contacts and to the contacts to the pocket, and the same voltage with the emitter is applied to the substrate. The collector leads are supplied with positive voltage from the power source through collector load resistances. The device has a symmetrical structure and the same loads, so the currents of the working collectors are equal and the voltage difference at the outputs between the two collectors is zero.

In a magnetic field with a magnetic induction vector parallel to the surface of the crystal, under the influence of the Lorentz force, the flows of charge carriers - electrons injected from the emitter, flowing in opposite directions to the two measuring collectors of a three-collector bipolar magnetotransistor with orthogonal flows of charge carriers, experience a deviation in the base in different directions . In this case, the current lines opposite one collector are shortened, and opposite the other lengthen. There is an asymmetry of streamlines, respectively, the current of one working collector increases, and the current of another collector decreases. At identical loads, a difference in voltage drop occurs, and a voltage difference arises between the collectors, which depends on the magnitude of the magnetic field.

A three-collector bipolar magnetotransistor with orthogonal charge carrier flows has a new quality - increased sensitivity to magnetic induction directed parallel to the surface of the crystal. Together with an increase in sensitivity, the measurement error decreases due to the initial current imbalance of the measuring collectors, which leads to a decrease in the sensitivity threshold.

Information sources

1. Mitnikova I.M., Persiyanov T.V., Rekalova G.I., Shtyubner G.A. / Study of the characteristics of silicon side magnetotransistors with two measuring collectors / FTP, 1978, vol. 12, No. 1, pp. 48-50.

2. US patent 4700211.

3. RF patent 2284612 - prototype.

4. A. Häberli, M. Schneider, P. Malcovati, R. Castagnetti, F. Maloberti, H. Baltes / 2D Magnetic Microsensor with On-Chip Signal Processing for Contactless Angle Measurement // IEEE Journal of Solid-State Circuits, v .31, pp. 1902-1907, 1996.

Claims (1)

A three-collector bipolar magnetotransistor with orthogonal charge carrier flows, containing a silicon single crystal substrate, a base region on the substrate surface, having a low impurity concentration, heavily doped emitter regions, first and second measurement collectors with a depth less than the depth of the base region and located inside the base region, regions of heavily doped contacts to base, a diffusion pocket that separates the base region from the substrate and is the third collector, a strong the contacts to the pocket and the substrate, the contacts to the pocket are connected by metallization with the contacts to the base, the contacts to the substrate are connected by metallization with the contacts to the emitter, the emitter and collector regions are located in the base region at a distance from each other, the contacts to the pocket are located in the pocket near the boundary pn -junction of the base-pocket opposite the measuring collectors, characterized in that the emitter is the same length as the measuring collectors, heavily doped contacts to the base are located end to end with strip ends emitter with an orthogonal direction between the emitter and the contact to the base relative to the direction between the emitter and the measuring collectors.

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