JPS5836998Y2 - semiconductor pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor pressure sensor useful for measuring two pressures simultaneously.

For example, semiconductor pressure sensors that utilize the so-called piezoresistance effect, in which electrical resistance changes due to changes in the energy band structure and carrier mobility when mechanical strain is applied to a semiconductor such as silicon (Si), are It has a structure as shown in the figure.

Figures a and l) show its plan view and cross-sectional view, and figure C
indicates the number of circuits.

In these figures, reference numeral 11 is an n-type silicon substrate, and the diaphragm portion 1 is etched from the bottom, leaving the periphery.
1a is formed, and boron (B) is formed on the surface of the substrate 11.
) etc. are selectively diffused into the resistive parts R1 to R.
4 is formed.

12a to 12d are P-type diffusion regions, but the impurity concentration is high, and resistors R1 and R2, resistors R2 and R3...
It is a lead part that connects between...

Aluminum (A1) electrodes 13a to 13d are provided at the outer corners of the lead portions 12a to 12d, which serve as terminals for external lead wires.
The wafer surface except 3d is silicon oxide film (S102)
It is covered with 14.

By appropriately selecting the crystal plane and crystal axis in the above configuration, carrier mobility can be set in two different directions so that the amount of change is the same and only the sign (increase/decrease direction) is different.

In the example of FIG. 1, the pair R1, R3 and the pair R2, R4 (particularly the bottom part of the U-shape) are provided perpendicularly, and as a result, R,
, R3 pair increases in response to an increase in strain, the resistance value of R2, R4 pair decreases.

FIG. 2 is a sectional view showing an example of a conventional semiconductor pressure sensor using the piezoresistive element 10 described above.

The etched bottom side of the piezoresistive element 10, which forms the main part of the semiconductor sensor described in FIG. 1, is adhered to the silicon pedestal 21 in a vacuum chamber, and the gap between the two forms a vacuum reference pressure chamber.

This sensor element is attached by bonding its silicon pedestal 21 to a ceramic substrate 20 provided with a pressure introduction hole 20a.

These adhesive parts a are made of glass having similar expansion coefficients and are welded together.

Note that a signal processing circuit may be mounted on the ceramic substrate 20, as is often the case with hybrid ICs.

The upper part of the ceramic substrate 20 is covered with a lid 22 made of a ceramic material, and a pressure introduction pipe (glass tube) 23 communicating with the hole 20a is bonded to the lower part.

In such a semiconductor pressure sensor, the pressure to be measured P1 introduced from the introduction pipe 23 is applied to the diaphragm portion 11 of the element 10.
The pressure Pr in the reference pressure chamber between the lower surface and the pedestal 21 (usually 10-1 to 10' T
The measured pressure P1 is measured based on the reference pressure Pr.

Since the pressure measured by this sensor is pH, for example, if data on both the intake air pressure into the engine and the atmospheric pressure are required for combustion control, two semiconductor pressure sensors with the same configuration are required. Become.

This also applies to a semiconductor pressure sensor configured as shown in FIG.

FIG. 3 shows a pressure sensor using a package such as To-5, with an eyelet-shaped insulator 2 in the central opening of the metal base 25.
8 are fitted and glued, and the central opening 28 of the insulator 28
A piezoresistive element 10 is bonded so that its etched bottom side contacts the inner surface of the metal base 25, more specifically, the inner surface of the eyelet-shaped insulating material 28, so as to cover the piezoresistive element 10.

The inner surface of the metal base 25 on which the piezoresistive element 10 is attached is covered with a metal can 24, and after a vacuum is drawn through the central thin tube portion of the metal can, the thin tube portion is fused to form an airtight sealing portion 24a. The internal space covered by the metal can 24 and the metal base 25 is used as a reference pressure chamber, and the introduction pipe 23 is attached to the outer surface of the metal base 25 surrounding the central opening 28a, and the introduction pipe is used as the pressure source to be measured. I am trying to connect to.

Therefore, the measured pressure P1 from the introduction pipe 23 is supplied to the bottom side of the element 10, contrary to the example shown in FIG.

26 and 27 are insulating materials, and these are the leads 29.3
0, and the lead wire of the element 10 is connected to this lead 29.3.
0 within the reference pressure chamber.

In this type of semiconductor pressure sensor, the manufacturing process of the reference pressure section (vacuum containment) is difficult, but the other processes are easily performed using established manufacturing techniques for ordinary semiconductor elements, ICs, and the like.

By the way, when controlling by measuring pressure, pressures are often measured at two or more locations, as in the above example, and in the conventional method, two or more pressure sensors are required because they are attached individually.

However, even when two or more pressures are measured simultaneously, the reference pressure of each sensor may be the same.

Taking these points into consideration, if two or more pressure measuring elements are provided in the same package and the reference pressure is shared, manufacturing becomes easier and miniaturization becomes possible.

The present invention was developed focusing on the above-mentioned points, and in particular,
Although the present invention is effective when applied to a pressure sensor that measures two pressures simultaneously, the present invention will be described in detail below with reference to the illustrated embodiments.

FIG. 4 shows an embodiment of the present invention, in which a ceramic substrate 20 is used as in FIG. 2.

A through hole 20b is provided in the center of the substrate 20, and a pair of piezoresistive elements 10 are placed on the upper and lower surfaces of the substrate 20, sandwiching the hole 20b.
．． 10' is fixed to cover the hole.

The space formed by the element 10, 10' and the hole 20b becomes a reference pressure chamber and is maintained at a high vacuum reference pressure Pr.

A first pressure to be measured P1 is supplied to the surface of the element 10 through an introduction pipe 23, and a second pressure to be measured P2 is supplied to the surface of the element 10' through another introduction pipe 23'.

Expanded open ends 23 a , 23 a of pipes 23 , 23 ′
' and the substrate 20 are hermetically sealed, and these members 20
゜23.23' is integrally supported by the insulating material 31, and the element 1
Electric signals are taken out from 0.10' through internal leads, wiring attached to the upper and lower surfaces of the substrate 20, and external leads 32 and 33.

In the above embodiment, the first,
Second measured pressure P1. P2 is piezoresistive element 10°10
Since Pl and P2 can be measured at the same time, the reference pressure Pr used at this time is supplied to element 10.'.
10' is common.

Therefore, according to the present invention, if one pressure measurement mechanism is manufactured, the reference pressure parts of two pressure measurement mechanisms can be formed with the same degree of difficulty, which improves cost performance and improves semiconductor performance for measuring multiple pressures at the same time. This has the advantage that the total package capacity of the pressure sensor can be reduced compared to the conventional one-to-one method.

[Brief explanation of the drawing]

Figures 1a, l), and c are a plan view, cross-sectional view, and equivalent circuit diagram of a piezoresistive element with a bridge configuration; Figures 2 and 3 are cross-sectional views showing different conventional semiconductor pressure sensors; Figure 4; FIG. 1 is a sectional view showing an embodiment of the present invention. 10.10'... Piezoresistance element, 20...
...Ceramic board, 23.23'...Pressure introduction pipe, Pr...Reference pressure, Pl, P2...
...Measured pressure.

Claims (1)

[Scope of utility model registration request] In a semiconductor pressure sensor that applies a reference pressure to one side of a semiconductor crystal piece and a measured pressure to the other side and measures the measured pressure using a piezoresistive effect, a pair of semiconductor crystal pieces are placed on both sides of a substrate opening of a common package. , the semiconductor pressure sensor is attached to cover the opening, and the opening gap closed by the pair of semiconductor crystal pieces serves as a common reference pressure chamber.