JPH0438273Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a semiconductor pressure transducer that converts pressure into an electrical signal by utilizing the piezoresistance effect of a semiconductor single crystal such as silicon, and particularly relates to a semiconductor pressure transducer that converts pressure into an electrical signal by utilizing the piezoresistance effect of a semiconductor single crystal such as silicon. This invention relates to improvements in semiconductor pressure transducers that effectively realize temperature compensation of the transducer.

<Prior art> A conventional semiconductor pressure transducer has a pressure detection element that detects the pressure to be measured and a temperature detection element that detects temperature changes of the semiconductor chip formed on the same semiconductor chip. The measured temperature characteristics are stored in a memory corresponding to each semiconductor pressure transducer, and this characteristic is used to perform correction calculations on the measured pressure obtained by the pressure detection element.

However, measuring the temperature characteristics of each semiconductor pressure transducer and handling a large amount of data as a single unit as characteristic data unique to each semiconductor pressure transducer increases the number of adjustment steps and costs. There are problems that arise.

<Purpose of the invention> In view of the above-mentioned prior art, an object of the present invention is to provide a semiconductor pressure transducer that can realize versatile temperature compensation with a simple configuration.

<Configuration of the present invention> The configuration of the present invention to achieve this object relates to a semiconductor pressure transducer that has a semiconductor gauge chip and detects the pressure to be measured via a strain gauge on the gauge chip. A first gauge bridge that responds to strain corresponding to pressure, a second gauge bridge that responds to a predetermined reference stress formed in the gauge chip, and a bridge output E _p and a second gauge bridge when the first gauge bridge is driven with a constant voltage. Using the bridge output E _s when the two-gauge bridge is driven at a constant voltage and the bridge output E _s0 at the reference temperature of the second-gauge bridge, E _p /
(E _s /E _s0 ), and outputs a pressure signal corresponding to the pressure to be measured.

<Example> Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1a is a perspective view showing a sensor portion of an embodiment of the present invention, and FIG. 1b is a side view seen from the direction of arrow A in FIG. 1a.

Reference numeral 1 denotes a semiconductor substrate made of silicon or the like, and a silicon rectangular gauge chip 2 is placed on this substrate.
is fixed. Each side of the gauge chip 2 is selected so that the silicon crystal axis is <110>, and the vertical axis is selected to be <100>.

A rectangular strain detection hole 3 is formed in the gauge chip 2, and a diaphragm 4 is formed above it. Further, a pressure introduction hole 5 is bored in the substrate 1 facing the strain detection hole 3.

A U-shaped reference hole 6 communicating with the outside air is formed on the right side of the strain detection hole 3.

The substrate 1 and the gauge chip 2 are bonded together by anodic bonding or low melting point glass bonding to maintain airtightness. However, the leg part 7 of the gauge chip 2 on the right side of the reference hole 6 and the substrate 1 are not joined, and the upper part 8 of the reference hole 6 and the leg part 7 form a cantilever 9. The length h of the leg portion 7 is the reference hole 6.
The cantilever is formed to be slightly longer than the length l of the left leg 10 of the cantilever 9, and a reference stress σ _R is applied to the cantilever 9, thereby generating a reference strain therein.

FIG. 1c is a gauge arrangement diagram showing the arrangement of strain gauges formed as P-type semiconductors in FIG. 1a.
As shown in the figure, strain gauges G ₁ , G ₂ , G ₄ , and G ₃ are formed in this order on the diaphragm 4 above the strain detection hole 3 . The influence of strain on strain gauges G ₁ and G ₃ is equal, e.g. their resistances both increase as the measured pressure P increases, and the effect of strain on strain gauges G ₂ and G ₄ is equal, for example as the measured pressure P increases. It is arranged so that its resistance is reduced. Furthermore, strain gauges _G5 and _G6 are placed above the reference hole 6.
Strain gauges G ₇ and G ₈ are formed in the same direction as G ₁ to _{G 4} and perpendicular to these. The effect of strain on the resistance for strain gauges G ₇ and G ₈ is equal, and the effect of strain on the resistance for strain gauges G ₅ and G ₆ is also equal.

With the above configuration, the pressure to be measured P introduced from the pressure introduction hole 5 is introduced into the strain detection hole 3 and displaces the diaphragm 4. This displacement is measured by strain gauge
Detected at _G1 to _G4 . On the other hand, the reference stress σ _R is measured by strain gauges G ₅ to G ₈ formed on the upper part 8 of the cantilever 9
Detect.

These strain gauges G ₁ to G ₄ and strain gauges G ₅ to
Each output detected by G ₈ is converted into pressure by the circuit shown in FIG.

Strain gauges G ₁ to G ₄ are strain gauges G ₁ and G 4 respectively.
G ₃ and strain gauges G ₂ and G ₄ together form a bridge BG ₁ on diagonal sides. Also, strain gauge
G ₅ to _{G 8} are bridges with strain gauges G ₅ and G ₆ and strain gauges G ₇ and G ₈ forming diagonal sides, respectively.
Forming BG ₂ . Power terminal 1 of Bridge BG ₁
1, 12 and power terminals 13, 1 of bridge BG ₂
A constant voltage V _s is applied to each of the terminals 4 and 4. In this case, the bridge output E p is at the output ends 15, 16 of the bridge BG ₁ , and the bridge output E _p is at the output ends 17, 1 of the bridge BG ₂ .
8, the bridge output E _s is obtained in the form shown in the following equation.

E _p =V _s π ₀ KP (1+g(t)) (1) E _s =V _s π ₀ σ _R (1+g(t)) (2) Here, π ₀ is the piezoresistance coefficient at the reference temperature t ₀ , K
is a conversion constant when converting the measured pressure P into stress, σ _R is the reference stress, and g(t) is the temperature coefficient of the piezoresistance coefficient of the gauge, which is expressed by the following equation.

g(t)=β ₁ t+β ₂ t ² +…+β _i t ⁱ +… (3) Here, β _i is the temperature coefficient of the i-th order piezoresistance coefficient π. Note that in equation (1), V _s π ₀ K is a constant value, so it is set as a constant B, and in equation (2), V _s π ₀ σ _R
is the bridge output of bridge BG ₂ at reference temperature t ₀
Since E _s0 is shown, applying these relationships to equations (1) and (2), E _p = BP (1 + g (t)) (4) E _s = E _s0 (1 + g (t)) ( 5), and from equations (4) and (5), we obtain the relationship E=BP=E _p /(E _s /E _s0 ) (6) where E=BP. The left side is a value proportional to pressure, and the term of temperature coefficient g(t) is eliminated, so by calculating equation (6), output E that is not affected by temperature can be obtained.
can be obtained.

In the arithmetic circuit PCC in Figure 2, each bridge
The calculation of equation (6) is executed using the bridge outputs E _p and E _s of BG ₁ and BG ₂ and the bridge output E _s0 at the reference temperature t ₀ . In addition, the bridge output E _s0 is determined by measuring the output of the bridge BG ₂ at the reference temperature t ₀ in advance, and calculating the output from the arithmetic circuit.
Configure PCC externally.

<Effects of the invention> As explained above in detail along with the examples,
According to the present invention, a gauge bridge that responds to the measured pressure and a gauge bridge that responds to the reference stress are formed on the gauge chip, and the outputs of these bridges are used to perform simple calculations, thereby eliminating the need for special compensation for temperature characteristics. It is possible to realize a semiconductor pressure sensor that is not affected by the temperature of the gauge chip, has high reliability, and greatly reduces the number of adjustment steps.

[Brief explanation of the drawing]

Fig. 1a is a perspective view showing a sensor portion of an embodiment of the present invention, Fig. 1b is a side view taken from arrow A in Fig. 1a, and Fig. 1c is a strain gauge formed in Fig. 1a. FIG. 2 is a block diagram of a pressure conversion circuit showing an embodiment of the present invention. 1... Board, 2... Gauge chip, 3... Strain detection hole, 4... Diaphragm, 5... Pressure introduction hole,
6...Reference hole, 9...Cantilever, _G1 to _G4 ...
...Strain gauge, BG ₁ ... Bridge, G ₅ to _{G 8} ... Strain gauge, BG ₂ ... Bridge, V _s ... Constant voltage,
PCC... Arithmetic circuit, E _s ′, E _p ... Bridge output.

Claims (1)

[Scope of utility model registration request] A thin diaphragm is formed by forming a semiconductor substrate through which a pressure introduction hole through which the pressure to be measured is introduced, and a strain detection hole communicating with the pressure introduction hole on the side opposite to this substrate. and a gauge chip having a U-shaped reference hole communicating with the atmosphere adjacent to the strain detection hole, the upper part and the leg part forming a cantilever, and the size of the leg part being selected to generate a reference strain; a first gauge bridge formed on the diaphragm that responds to strain corresponding to the measured pressure; a second gauge bridge formed on the top of the cantilever that responds to the reference strain; and when the first gauge bridge is driven with a constant voltage. bridge output E _P , bridge output E _S when the second gauge bridge is driven with the constant voltage, and the second gauge bridge
Bridge output E _S0 at gauge bridge reference temperature
A semiconductor pressure transducer comprising: a calculation means for performing the calculation E _P /(E _S /E _S0 ) using the above, and outputs a pressure signal corresponding to the pressure to be measured.