DE2549001A1 - PRESSURE TRANSDUCER - Google Patents

Description

The invention relates to a pressure transducer with a pressure sensitive element monocrystalline silicon, which is pressure-sensitive Element has a membrane of small thickness and has a thickened edge on the outside, wherein in the membrane dolinunga-sensitive resistors arranged are.

Such a known pressure transducer has been described, for example, in Dutch patent application 68.17089. The pressure sensitive element has a flat membrane; the thickened edge is used to easily attach the pressure-sensitive element υλχ . The resistors are for example 609820/1012

PHN. 7796.

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included in a Wheatstone bridge circuit. the The output voltage of the bridge can be fed to an integrated circuit, for example. If the If the membrane is relatively thick, the output voltage will be fairly linear with the pressure. However, in order to achieve high sensitivity it is desired to make the membrane as thin as possible. However, there is a strong deviation from the desired one Linearity between pressure and output voltage.

The aim of the invention is to create a pressure transducer with great sensitivity, the relationship between pressure and output voltage nevertheless being fairly linear. For this purpose, according to the invention, the membrane has a rigid central part which is designed as a thickening, which thickening has a diameter in the order of magnitude of 0.5 to 0.7 times the inside diameter of the thickened edge. It has been found that the thickness of the membrane can be made using this measure, with a linearity better than 15 ° can be reduced such that the · pressure transducer a h- to 5 times large ere sensitivity than when using a membrane without the rigid center part. On the other hand, with the diaphragm having the same thickness, the linearity of the pressure transducer according to the invention is significantly better than that of the known pressure transducer.

It should be noted that pressure sensitive elements 609820/1012

PHN. 7796.

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with a thickened central part per se at Beschleurii ~ motion meters are known. In general, there is no question of a membrane (but dex thickened Part is connected to an outer ring via spokes, it is also intended to focus on accelerations, to maintain a responsive element and not to improve the linearity. The ratio of the Diameter of the middle part to the inner diameter dos thickened edge in known designs of the desired value xtfessentially in the invention.

In a preferred embodiment according to the invention, the membrane consists of an epitaxial membrane Layer grown on a silicon substrate, in which substrate the thickened edge and the thickened central part are formed.

The pressure regulator can find a very useful field of application in gas flow measurement, for example when measuring the inlet air of an internal combustion engine, With this air volume measurement, the mass flow is inversely proportional to the absolute temperature. To find a suitable application of the pressure transducer In order to maintain this temperature influence must then be compensated in some way, which is the case with a Another embodiment of the invention happens when the strain-sensitive resistances due to diffusion of an acceptor are formed in an η-conductive epitaxial layer, \ '7obeherein the diffusion concentration

B 0 9 R? 0/1 η 1?

■ if-- ■

25490Π1

PHN. 7796. 24-10-1975.

1 R is on the order of 5 x 10 atoms per cm ³ .

Piezoresistance and coefficient of the p-type silicon, of which the resistors are made, is temperature-dependent; it was found that when the concentration of these genamiten coefficient to the absolute temperature almost inversely proportional in a temperature range between -4o ° C to + 120 ⁰ C, so that complete equalization takes place.

An embodiment of the invention is illustrated in the drawing and will be described below the near ^1st Show it:

Fig. 1 is a section through a pressure sensitive Element according to the line 1-1 in Fig. 2,

Figure 2 is a plan view of the pressure sensitive Element.

In Figs. 1 and 2, a form of execution of a pressure-sensitive element according to the invention is shown. A conductive epitaxial layer 5 is applied to a substrate made, for example, of η-conductive monocrystalline silicon. An annular recess 1 is formed in the substrate, which continues to the epitaxial layer. The recess 1 can be formed, for example, with the aid of spark erosion. This creates a pressure-sensitive element with a thin membrane 2, a thickened edge 3 and a rigid, thickened central part h. In the epitaxial layer 5 are dchmmgs-sensitive

609820/10 12

9 R 4 9 O η 1

pun. 7796. 2 ^ -10-1975.

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Resistors 6 arranged, for example by. diffusion of an acceptor, such as boron.

The resistors 6 are then made of p-conducting Silicon. Basically it could be the substrate and the epitaxial Layer, however, also consist of p-conducting silicon into which n ~ leiten.de resistors diffuse or the resistances can be formed by means of ion implantation.

Fig. 2 shows an example of a pattern dex · resistors 6 which are connected according to a Wheatstone bridge. In this embodiment, two resistors are arranged next to one another, one in the vicinity of the thickened edge 3 and one in the vicinity of the central part h. This ensures that the curvature of these resistances is opposite when the membrane is bent out (the thickened edge 3 is fixedly arranged in a housing, the rigid central part k moves with the membrane).

The epitaxial layer is electrical with one insulating .Schicht 7 made of, for example, silicon oxide covered. On this layer conductors 8 are arranged, which are in an opening of the insulating Layer 7 at 9 with resistors 5 electrical νerbundeη are.

Of the conductors 8 electrical \ ^r can be onnectivity led to non-illustrated electronic circuit elements.

609 8 20/1012

N. 7796.

2 5 49 O Π1 24-10-1975.

The pressure-sensitive element can be in any any housing can be installed. As already mentioned, the thickened edge 3 is used to provide a favorable Maintain connection in the housing. On the side on which the epitaxial layer is located, in Housing a vacuum, while a gas or liquid pressure acts on the other side. That However, the pressure-sensitive element can also be used in the event of difference pressure measurement can be used. As a scope a measurement of fluid pressure can be called, for example, blood pressure measurement. A very A favorable application for gas pressure measurement is the measurement of the supply air in an internal combustion engine. With a correct one Metering the supply air and fuel will maintain favorable combustion while polluting the air is avoided.

In a favorable embodiment, the pressure-sensitive element has a central part 4 with an outer diameter of 0.5. mm and a thickened edge 3 with an inner diameter of 1 mm. The thickness of the epitaxial layer 5 is 10 µm. This very small thickness of the membrane is very sensitive; With the rigid central part h of the given dimensioning it is achieved that the linearity of the pressure compared to the output voltage of the Wheatstone bridge is less than 0.5 fo.

It is beneficial, especially when measuring 6 0 9 8 2 0/1012

2 5 4 9 O η 1

PHN. 779 ^. 24-10-1975.

Air for internal combustion engines, the diffusion concentration of the p-conducting resistors 6 in the order of magnitude

1 ft
tion of 5 · 10 6 atoms per cm ³ instead of the usual value

10 to choose. It was found that the temperature influence on the resistance value of the absolute Temperature is inversely proportional. Since the mass flow of the air of the absolute temperature is reversed is proportional, do not need any further temperature-compensating agents at the concentration mentioned Measures to be taken.

6098? 0/1 01 ?

Claims (2)

pun. 7796. 2549001 2 ^ -10-1975. - 8 PATENT CLAIMS. 1 λ pressure transducer with a ^ m pressure-sensitive element made of monocrystalline silicon, which pressure-sensitive element has a membrane of small thickness and has a thickened edge on the outside, with expansion-sensitive resistors being arranged in the membrane, which means that the membrane is rigid having middle part formed as a thickener, which thickener has a diameter in the order of from 0.5 to O, 7f ^"a chen of the inner diameter of the thickened rim. 2. Pressure transducer according to claim 1, characterized in that the membrane consists of an epltaxial Layer is grown on a silicon substrate, in which substrate the thickened edge and the, thickened central part are formed. 3 · Pressure transducer according to claim 1 or 2, characterized marked that the strain-sensitive resistors are formed by diffusion of an acceptor in a conductive epitaxial layer, the Diffusion concentration in the order of magnitude of 18th
5 x 10 atoms per cm ³ . 609820/1012