RU2271523C2 - Semiconductor pressure transformer - Google Patents

Abstract

FIELD: measuring equipment engineering, in particular, engineering of small pressures transformers.

SUBSTANCE: semiconductor pressure transformer has silicon membrane with thickened peripheral base, made of n-type conductivity silicon and alloyed with boron up to concentration not less than 5*10¹⁹ cm^-3. Membrane has thickness equal to height of tension resistors formed at layer of silicon dioxide held on membrane and made of silicon, alloyed with boron up to similar concentration level as membrane itself. Tension resistors are connected by means of commutation buses with metallized contact areas to form a bridge measuring circuit. Membrane has profile with concentrators of mechanical strains in place of tension resistors position, which is a combination of thinned portions and rigid centers, and surface of tension resistors is covered by silicon dioxide layer.

EFFECT: increased sensitivity of transformer while maintaining native resonance frequency, improved durability and hardness of membrane, improved linear transformation range, improved stability of characteristics.

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Description

The proposed technical solution relates to the field of measurement technology, in particular to low-pressure transducers, and can be used in the design and manufacture of small-sized semiconductor pressure transducers operable at elevated temperatures. A known pressure transducer containing a silicon shaped crystal, on which a tensor-resistive bridge circuit of polycrystalline silicon is formed, isolated from the substrate by silicon dioxide [1].

The disadvantage of this Converter is the low sensitivity due to the low tensosensitivity of polysilicon.

Known pressure transducer and method of its manufacture, characterized in that the strain gauges made of high-alloy silicon through a dielectric layer deposited on a profiled silicon membrane [2].

A disadvantage of the known device and method is the low sensitivity to measuring low pressures, due to the limitations of the formation of small thicknesses of the membranes.

The closest in technical essence to the invention is a pressure transducer, characterized in that the membrane with a dielectric layer on which the strain gages are formed is doped with boron to the same concentration level as the strain gages, while the thickness of the membrane under the dielectric layer is equal to the thickness of the strain gages [3] .

The disadvantages of the known device are low sensitivity to measuring low pressures while maintaining their own resonant frequency, low membrane strength, a small range of linear conversion due to the presence of a uniform membrane thickness. In addition, this converter has a significant level of measurement errors, determined by the low stability of its characteristics over time due to the presence of an unprotected surface of strain gauges.

The invention is aimed at increasing the sensitivity of the converter while maintaining its own resonant frequency, increasing the strength of the membrane, increasing the range of linear conversion, increasing the stability of the characteristics.

According to the invention, in a semiconductor pressure transducer containing a silicon membrane with a thickened peripheral base made of n-type silicon and doped with boron to a concentration of at least 5 · 10 ¹⁹ cm ^-3 , and having a thickness equal to the height of the strain gauges formed on the membrane mounted a layer of silicon dioxide and made of silicon doped with boron to the same concentration level as the membrane, and combined with the help of busbars in a bridge measuring circuit, and having connected metalized contact pads with them, the membrane contains a profile with stress concentrators at the location of the strain gages, which is a combination of refined sections and rigid centers, and the surface of the strain gages is covered with a layer of silicon dioxide.

The introduction of the proposed design containing a profiled membrane with stress concentrators at the location of the strain gages, which is a combination of refined sections and rigid centers, allows us to obtain a sensitivity of semiconductor pressure transducers of less than 10 Pa while maintaining their own resonant frequency, operable up to 300 ° C and having breakdown voltage up to 1000 V, increases the strength of the membrane, which entails an increase in the reliability of the entire converter, increasing It is linear and expands the range of linear conversion, and the introduction of a protective layer of silicon dioxide on the surface of strain gauges increases the temporal and temperature stability of their characteristics and reduces the level of measurement errors.

The proposed device is illustrated in figure 1, 2.

1, 2 shows a converter containing a n-type silicon sensing element (1) with a boron-doped membrane (2) with a profile (3) and a thickened peripheral base (4) with silicon dioxide formed on it (5) ) strain gauges (6) coated with a layer of silicon dioxide (7) and connected to the contact pads (8) using patch buses (9).

The principle of operation of the converter is as follows.

The measured pressure, acting on a membrane with a rigid center, deforms the strain gauges and increases the imbalance of the bridge circuit into which the strain gauges are closed. The choice of silicon concentration of at least 5 · 10 ¹⁹ cm ^-3 and the presence of a profiled membrane with stress concentrators at the location of the strain gages allows stop etching to form thin membranes with a thickness of 1-3 microns without breaking the structure. The membrane itself is a combination of refined sites and rigid centers. Thus, this design allows to obtain a sensitivity of semiconductor pressure transducers of less than 10 Pa while maintaining its own resonant frequency. Due to the fact that the surface of the strain gages is coated with a layer of silicon dioxide, due to the presence of this protective coating that prevents the penetration of unwanted impurities from the external environment onto the surface of the strain gages, the temporal and temperature stability of their characteristics increases and the level of measurement errors decreases.

The technical and economic advantages of the proposed converter in comparison with the known are:

the possibility of creating semiconductor pressure transducers for ranges of less than 10 Pa, operable up to 300 ° C and having a breakdown voltage of up to 1000 V;

improving the reliability, linearity, time and temperature stability of the characteristics of the Converter;

extension of the linear transformation range;

decrease in the level of measurement errors.

Information sources

1. SAE Techn.Par.Ser, 1986, No. 860473, p. 71-77: Express Information IPiS, No. 9, 1987.

2. US patent No. 4400869, CL. H 01 L 21/225, 1984.

3. Copyright certificate of the USSR No. 1732199, cl. G 01 L 9/04, 1990.

Claims (1)

A semiconductor pressure transducer containing a silicon membrane with a thickened peripheral base made of n-type silicon and doped with boron to a concentration of at least 5 · 10 ¹⁹ cm ^-3 , having a thickness equal to the height of the strain gauges formed on the silicon dioxide layer fixed to the membrane and made of silicon doped with boron to the same concentration level as the membrane, and combined with the help of busbars in a bridge measuring circuit, and having metallized with them nye contact pads, characterized in that it comprises a profile with a membrane stress concentrators in place of strain gauge arrangement, which is a combination thinned portions and hard centers and surface strain gauges covered with a layer of silicon dioxide.

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