JPS5940308B2 - pressure sensitive element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure-sensitive element that improves the output linearity of a semiconductor strain gauge in which impurities are diffused into a single crystal such as Si or Ge.

FIG. 1 shows a conventional pressure-sensitive element, in which 1 is an anisotropic single crystal made of a semiconductor such as Si or Ge held on a substrate 2, and a part of the pressure-receiving surface of this is cut out by etching. It is cut out to form a circular recess 1a.

This is made thin in consideration of obtaining a predetermined sensitivity and improving the linearity of output resistance change when pressure Po is applied. Further, on the upper side of the anisotropic single crystal 1, a semiconductor layer 1, non-gauge 3, and τ are diffused by a method of IC manufacturing technology to form a diffused resistance layer. For example, n
When a diffused resistance layer is formed on the <100 (crystal direction)> crystal plane of the anisotropic single crystal 1 of type Si, the resistance change rate △R/R with respect to pressure change of each resistance layer is as follows: △Rp/Rp■ 1(1-ν)←')-4(-)2 ΔRn/Rn■- becomes (1-ν)(pπ44(-2)2.

Here, π44 is the piezoresistance coefficient of Si, ν is Poisson's ratio, is the thickness of the pressure receiving surface, and a is the radius. ΔR Therefore, as far as we can see from the above equation, the rate of change in resistance - is proportional to the pressure Po, so it seems that the diffusion resistance layers of the semiconductor strain gauges 3 and 3' do not exhibit nonlinearity.

However, in the thin recesses 1a of this type of anisotropic single crystal 1, a phenomenon of output nonlinearity called a balloon effect usually occurs.

On the other hand, regarding the plate thickness of the anisotropic single crystal 1 (pressure-receiving diaphragm) and the displacement ωo of the pressure Po, the balloon effect does not occur as long as ωo/ is below a certain value. Furthermore, the value of 2 varies depending on the direction in which the pressure Po is applied. Therefore, if the above-mentioned balloon effect occurs in the pressure-sensitive element itself, if a positive pressure Po is applied as shown in Fig. 2,
The terminal effects appear differently. Furthermore, when pressure Po in the direction shown in FIG. 1 is applied, the semiconductor strain gauge 3 is set so that the resistance increases and the semiconductor strain gauge 3' is set so that the resistance decreases.The rate of change in resistance with respect to the pressure Po is ΔR/ The mode of linearity of R is different between the +Po side and the -Po side.

This nonlinearity varies depending on the measurement range, but is 0.5
It reaches about 2.0%. Therefore, this is a particular problem in the case of a coupled meter that measures a wide range, with a measurement range ranging from positive pressure to negative pressure. Note that FIG. 3 is an output characteristic diagram when a bridge circuit is constructed using the resistors Rp and Rn of the semiconductor strain gauges 3 and 3' shown in FIG. 1. This is △Rp, −ΔR
The output voltage VO is caused by the resistance difference of n. The present invention has been developed with the above points in mind. It has a simple structure, can be realized at low cost, has excellent corrosion resistance and insulation resistance, and has good straight line performance in a wide range of pressure measurements from positive pressure to negative pressure. The object of the present invention is to provide a pressure-sensitive element that provides high performance. below,
Embodiments of the present invention will be described with reference to the drawings.

In FIG. 4, reference numeral 11 is an anisotropic single crystal formed of a semiconductor such as Si or Ge, and as in FIG. In other words, semiconductor strain gauges 12 and 17 are formed.
On the other hand, on one side of the single crystal 11, that is, on the side where the semiconductor strain gauges 12 and 17 are located, a holding plate 13 that is substantially symmetrical with the single crystal 11 and made of the same material is arranged.

That is, the single crystal 11 is glass-welded to the holding plate 13, and A
It is fixed by means such as U-Si bonding or adhesive. In this case as well, the single crystal 11 and the holding plate 13 have recesses 11a and 13a formed by etching, respectively. Therefore, the single crystal 11 as a diaphragm has perfect symmetry, eliminating the balloon phenomenon, and the holding plate 13 Single crystal 1
Since it is bonded to the resistance diffusion surface side of the single crystal 11, not only the corrosion resistance of the surface portion of the single crystal 11 but also the insulation property can be maintained by applying an insulating material or the like.

Further, the recesses 11a and 13a of the single crystal 11 and the holding plate 13 may be formed by etching after joining the two. Therefore, the structure of the pressure sensitive element of the present invention is based on the semiconductor strain gauge 12.
, 17, and it is possible to eliminate nonlinearity due to the difference in terminal effects even in the case of positive pressure and negative pressure.

FIG. 5 shows the semiconductor strain gauge 12 for pressure change,
This figure shows a perfect straight line near the zero point, and very good linearity can be obtained even when the positive pressure increases.

Next, FIG. 6 shows another embodiment of the pressure-sensitive element of the present invention, in which
In this case, a diffusion resistance layer, that is, a semiconductor strain gauge 14, 14' is also formed on a holding plate 13 made of the same material as the single crystal 11. In this structure, the single crystal 11 and the holding plate 1
3 are joined with perfect symmetry, so the 6th
In addition to the pressure sensitive element having the structure shown in the figure, the semiconductor strain gauge 12 is resistor Rpl, l7 is Rnl, l4 is Rp2, l4.
' is Rn2, the rate of resistance change of the semiconductor strain gauges 12.17, 14, and 11 with respect to positive and negative pressure is the seventh
With the characteristics shown in the figure, when configuring a bridge circuit, the diffused resistance layers of the semiconductor strain gauges 12 and 12' on the P side in Figure 6 are used on the two sides as shown in Figure 8. (the diffusion resistance layer of the semiconductor strain gauges 14 and 11 is not used), the resistance difference (△
RPl-△R2), the output characteristic becomes as shown in Figure 9. Therefore, as is clear from the figure, the vicinity of the zero point becomes a perfect straight line, and the slope at the terminal is extremely gentle and saturated. ing.

Furthermore, both positive and negative pressures can be made completely equal and symmetrical. That is, semiconductor strain gauges 12, 12', 14, and 14' are provided on the single crystal 11 and the holding plate 13, respectively, and the bridge is constructed by using the two strain gauges 12 and 14 that have a completely opposite resistance action against the pressure PO. When the circuit is assembled, a linearity that is further improved than that of the pressure sensitive element having the structure shown in FIG. 4 can be obtained. Next, FIG. 10 shows the single crystal 11 and the holding plate 1.
3 respective semiconductor strain gauges 12, 17, 14
, 14' is used to construct a bridge circuit, and in this case as well, the same effect as in FIG. 8 can be expected.

} In FIGS. 4 and 6, 15 is a lead wire for taking out an output signal from the pressure sensitive element. FIG. 11 is a diagram showing how the pressure-sensitive element of the present invention is installed, in which the upper end of the support cylinder 16 is bent inward and returned, and the holding plate 13 of the pressure-sensitive element is welded to the end. It is fixed.
17 is a terminal, to which lead wires 15, 15' are connected.
is connected.

18 is an external lead line.

As described in detail above, according to the present invention, an anisotropic single crystal and a holding plate made of the same material are joined symmetrically, and a diffused resistance layer of a semiconductor strain gauge is formed on the single crystal surface on the side of the joining surface with the holding plate. , it is possible to not only make the resistivity against pressure change a perfect straight line near the zero point, but also to make the saturation slope at that terminal sufficiently gentle even when the pressure is increased. Moreover, the rate of change in resistance and the output characteristics can be made uniform and symmetrical over the entire range with respect to positive and negative pressurization, making it very easy to compensate.

Additionally, since semiconductor strain gauges are isolated from the atmosphere and pressure, they have excellent corrosion resistance.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional pressure-sensitive element, Figure 2 is a characteristic diagram of the rate of change in resistance of the semiconductor strain gauge of the pressure-sensitive element shown in Figure 1, and Figure 3 is the semiconductor strain gauge of Figure 1. FIG. 4 shows the pressure-sensitive element according to the present invention, where A is a cross-sectional view, B is a perspective view, and FIG. A characteristic diagram of the resistance change rate in a semiconductor strain gauge of a pressure element, FIG. 6 is a sectional view explaining another embodiment of the pressure sensitive element of the present invention, and FIG.
The characteristic diagram of the resistance change rate in the semiconductor strain gauge of the pressure-sensitive element shown in the figure, Figure 8 is the configuration diagram of the bridge circuit assembled using the two semiconductor strain gauges shown in Figure 6, Output characteristic diagram of the bridge circuit shown in Fig. 10
This figure is an output characteristic diagram of a bridge circuit assembled using the four semiconductor strain gauges shown in FIG. 6, and FIG. 11 is a sectional view showing the state in which the pressure-sensitive element is attached. DESCRIPTION OF SYMBOLS 11... Single crystal, 12, 17... Semiconductor strain gauge, 13... Holding plate, 14, 14t... Semiconductor strain gauge, 16... Support cylinder, 17... Terminal.

Claims (1)

[Claims] 1. A holding plate made of the same material and having approximately the same shape as the single crystal is attached to the other side of the single crystal, which has a concave portion formed on one side in order to increase a predetermined sensitivity and linearity of output resistance change. They are directly bonded via an insulating bonding material with the concave portion formed on the outside facing outward and symmetrically, and a semiconductor strain is placed on the single crystal face portion or both surfaces of the single crystal and the holding plate located at the bonded portion. Form the resistance diffusion layer of the gauge,
A pressure-sensitive element that is characterized by detecting a wide range of varying pressures, from positive pressure to negative pressure, with good linearity.