RU2262777C1 - Magnetic field sensor - Google Patents

Abstract

FIELD: semiconductor magnetic field sensors.

SUBSTANCE: proposed Hall-effect magnetic field sensor has arsenide-gallium chip incorporating semi-insulating substrate, magnetically sensitive epitaxial n layer, current and potential contacts; thickness of magnetically sensitive later (d) is specified in the range of d = (0.2 - 1.5) μv and mean concentration of electrons (n) in mentioned layer is chosen from following expression: n·d=(3,3-20)·10¹¹ cm².

EFFECT: enhanced specific magnetic sensitivity without noticeable increase in residual voltage and noise level or reducing operating stability.

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Description

The invention relates to semiconductor magnetically sensitive devices and can be used as a magnetic field sensor as part of measuring equipment and in various automatic control systems.

Known devices for measuring magnetic induction, for example, sensors using the Hall effect. Structurally, they are a rectangular semiconductor wafer with two pairs of orthogonally located electrical contacts [1]. The principle of operation of such devices is that when an electric current flows between one pair of contacts and under the influence of a magnetic field whose vector is perpendicular to the current vector, a Hall EMF appears on another pair of electrical contacts. The maximum value of the Hall EMF (U _xmax ), and therefore the sensitivity of the sensor, depends on the geometry of the plate (mainly thickness), the concentration and mobility of charge carriers [2]:

Where

A is the Hall constant;

μ is the mobility of charge carriers;

n is the concentration of charge carriers;

d is the thickness of the plate (magnetically sensitive crystal volume).

The disadvantage of such devices is the low sensitivity due to technological difficulties in ensuring the small thickness of the plate.

Of the semiconductor materials used for the manufacture of highly sensitive magnetic field sensors, according to expression (1), A ₃ B ₅ materials with high electron mobility, such as InSb, InAs, GaAs, etc., are most suitable. Of these, the use of gallium arsenide is preferable for the production of sensors intended for operation in a wide range of temperatures and under conditions of exposure to radioactive radiation and space factors [3]. The production of thin-film arsenide-gallium sensors makes it possible to set the thickness of the magnetically sensitive region of the crystal from a few nanometers to several micrometers. The specific magnetic sensitivity of industrial epitaxial arsenidogallium magnetic field sensors is 20-280 V / A · T [4].

However, an unlimited decrease in the thickness of the magnetically sensitive region (d) and (or) the concentration of charge carriers (n) to achieve high values of U _xmax according to expression (1) leads to such negative factors as an increase in the residual voltage of the sensor, an increase in the input and output resistances, and increased noise and reduced stability.

The closest device claimed by the present invention is a magnetic field sensor containing a substrate of semi-insulating gallium arsenide on which a magnetically sensitive layer of electronic type of conductivity is epitaxially grown by the method of MOS hydride technology [5]. The specific magnetosensitivity of these sensors was 220 V / A · T with an epitaxial film thickness of 0.35 μm and an electron concentration of 8.8 · 10 ¹⁶ cm ^{-3 in it} .

However, the achieved sensitivity level of arsenidogallium magnetic field sensors is insufficient for a number of astrophysical measurements, and especially measurements in the region of small values of magnetic induction.

The technical result, the achievement of which the claimed solution is directed, consists in increasing several times the specific magnetic sensitivity of the magnetic field sensor without a noticeable increase in the residual voltage, noise level and without reducing stability.

A positive result is achieved by the fact that the device of the magnetic field sensor, including an arsenidogallium crystal, consisting of a semi-insulating substrate, a magnetically sensitive epitaxial layer of the electronic type of conductivity, current and potential contacts, has a thickness of the magnetically sensitive layer d = (0.2-1.5) μm, in where the average electron concentration (n) is technologically given from the relation

To increase the stability of the sensor, the electron concentration across the thickness of the magnetically sensitive layer continuously increases from the substrate towards the electrical contacts.

The practical implementation of the claimed device has become possible due to the experimentally established optimal ratio (2) between the thickness of the magnetically sensitive layer and the concentration of electrons in it in the range of thicknesses of the magnetically sensitive layer (0.2-1.5) microns. The range of electron concentrations for fulfilling this ratio is 2 · 10 ¹⁵ -2 · 10 ¹⁶ cm ^-3 . In the framework of the MOS hydride epitaxial technology used in the prototype, the preparation of epitaxial layers with the indicated concentration requires large material costs for the deep cleaning of organometallic compounds. In the manufacture of the inventive magnetic field sensor, the chloride method of epitaxial growth was used, which allows to provide the necessary level of electron concentration and a predetermined doping profile at significantly lower costs for cleaning transport agents. To reduce the negative effect of the uneven spatial distribution of the electric field in the magnetically sensitive layer on the stability of the sensor, the electron concentration in the magnetically sensitive crystal layer increases from the substrate to the electrical contacts.

The drawing schematically shows one possible device of the inventive sensor, consisting of a crystal, including a substrate of semi-insulating gallium arsenide 1 and an epitaxial magnetically sensitive layer 2. The crystal is mounted on a ceramic carrier 3. Current and potential contacts 4 and 5 formed by planar technology are connected by wire conclusions 7 with metallized contact pads 6 on a ceramic carrier 3. Sealing compound 8 provides a monolithic design of the sensor. The figure does not show the electrical connections of the potential contacts 5 of the crystal with the pads of the ceramic carrier 3.

The sensor works according to the well-known principle of the action of traditional Hall elements: a control electric current is passed through current contacts 4, which causes a signal proportional to magnetic induction on potential contacts 5 under the influence of a magnetic field.

It was experimentally established that with a thickness of the magnetosensitive layer less than 0.2 μm at any values of the electron concentration, the residual voltage, input and output resistance, and noise of the magnetic field sensor increase. When the thickness of the magnetically sensitive layer is more than 1.5 μm, the sensitivity of the sensor decreases sharply.

An example of practical implementation. Magnetic field sensors were manufactured with a magnetically sensitive layer thickness of 0.3 μm and an average electron concentration of 10 ¹⁶ cm ^-3 . Their specific magnetic sensitivity reached 2000 V / A · T, which is almost an order of magnitude higher than that of the prototype. They steadily functioned at operating currents of 0.2-1 mA. The input resistance of the sensors was no more than 2500 Ohms, the specific residual voltage did not exceed 6-8 V / A. To reduce the negative effect of crystalline defects, a thin (3 μm) undoped buffer layer was grown between them at the substrate – epitaxial magnetosensitive layer. To reduce contact resistance, a thin (0.15 μm) heavily doped intermediate contact layer was built up over layer 2 (the buffer and contact layers are not shown in the drawing). The electron concentration gradient was set within the technological capabilities of epitaxial growth over the thickness of the magnetically sensitive layer and amounted to 5 · 10 ²¹ cm ^-4 . The manufactured magnetic field sensors are operable in the temperature range of -60 ÷ + 100 ° С.

Literature

1. G. Weiss. Physics of galvanomagnetic devices and their application. - M .: Energy, 1974, p. 10.

2. MM Mirzabaev, KD Potaenko, V. Tikhonov and others. Epitaxial Hall sensors and their application.

3. I.M.Vikulin, L.F. Vikulina, V.I. Stafeev. Galvanomagnetic devices. - M.: Radio and Communications, 1983, p. 9-13.

4. M.L. Baranochnikov. Micromagnetoelectronics. - M.: DMK Press, 2001, p. 47.

5. R. Campesato et.al. GaAs Hall sensor made by the MOCVD technique. Abstract journal "Electronics", 1993, No. 4, ref. 4B216.

Claims (2)

1. A magnetic field sensor comprising an arsenide-gallium crystal, consisting of a semi-insulating substrate, an epitaxial magnetically sensitive layer of electronic type of conductivity, current and potential contacts, characterized in that the magnetically sensitive layer has a thickness d = (0.2-1.5) μm, in which the average electron concentration (n) is technologically given from the relation n · d = (3.3-20) · 10 ¹¹ cm ^-2 . 2. The magnetic field sensor according to claim 1, characterized in that the concentration of electrons in the magnetically sensitive layer increases from the substrate towards the surface of the crystal.