JP3355341B2 - Semiconductor pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor using a piezoresistive element made of a semiconductor such as silicon or germanium.

[0002]

2. Description of the Related Art FIG. 16 shows a conventional semiconductor pressure sensor. A sensor substrate 2 made of, for example, n-type silicon is provided on the base 1, and a groove 2 a having a constant depth is provided near the center of the back surface of the sensor substrate 2, so that a gap is formed between the sensor 1 and the base 1. The portion formed and reduced in thickness by the groove 2a is a diaphragm portion 2b. Diaphragm part 2b
Are provided with a plurality of piezoresistive elements 3 made of, for example, p-type silicon. This semiconductor pressure sensor detects the magnitude of pressure by directly applying pressure to the surface of the diaphragm portion 2b of the sensor substrate 2 and electrically detecting a change in the resistance value of the piezoresistive element 3. .

Here, the rate of change in resistance of the piezoresistive element 3 when a pressure is applied, ΔR / R, is defined as σ _x , σ _y , σ _z , the stress acting in the x, y, z directions, respectively. Assuming that the piezoresistive coefficients relating to the stress in the direction are π _x , π _y , π _z , it is given by the following equation (1). The thickness of _{ΔR / R = π x σ x} + π y σ y + π z σ z ...... (1) actually the sensor substrate 2 diaphragm portion 2b,
For example, since it is sufficiently thin, about several hundred μm or less, there is substantially no stress σ _{z in the} z direction. In the case of the semiconductor pressure sensor of FIG. 16, the rate of change in resistance ΔR / R is expressed by the following equation (2). Is done. _{ΔR / R = π x σ x} + π y σ y ...... (2)

[0004]

By the way, the piezoresistive coefficient π _{x in the x} direction and the piezoresistive coefficients π _y and π _{z in the} y and z directions have opposite polarities, and depend on the direction of the crystal of the semiconductor such as silicon. However, for example, when π _x takes a positive value, π _y and π _z take negative values. On the other hand, as shown in FIG. 17, the distribution of the stresses σ _x , σ _y in the x, y directions in the diaphragm 2 b of the sensor substrate 2, both σ _x , σ _y have negative values near the center of the diaphragm 2 b. take,
In the vicinity of the periphery of the diaphragm 2b, both σ _x and σ _y take positive values.

As described above, since π _x and π _y have opposite polarities, σ _x and σ _y have the same polarity, π _x σ _x and π _y σ in the above equation (2) _y has opposite polarities to each other. Therefore, in the semiconductor pressure sensor of FIG. 16, the absolute value [ΔR / R] of the rate of resistance change ΔR / R is
As expressed by the following equation (3), the components in the x and y directions cancel each other out and the absolute value [ΔR / R] of the resistance change rate becomes a small value. As a result, the piezoresistance effect cannot be used effectively, There is a problem that the sensitivity of the pressure sensor tends to be low. In this specification, the absolute value is indicated by [] for convenience. [[Delta] R / R] = [[pi] _x [sigma] _x ]-[[pi] _y [sigma] _y ] (3) The maximum pressure measurable with a conventional semiconductor pressure sensor is, for example, about 40 to 85 MPa. Since detection of a higher pressure is required in some fields, development of a semiconductor pressure sensor capable of measuring a higher pressure has been demanded.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a semiconductor pressure sensor capable of measuring a high pressure and having high sensitivity as compared with the prior art. Therefore, the semiconductor pressure sensor according to claim 1 of the present invention provides the sensor substrate by forming a groove with a predetermined depth on the back surface of the sensor substrate provided on the base to form a gap with the base. While the part where the groove of was provided is the diaphragm part,
In a semiconductor pressure sensor in which a semiconductor piezoresistive element is provided on the surface of the diaphragm, a flat end of a force transmission rod extending in a direction substantially perpendicular to the surface of the sensor substrate is joined to the surface of the sensor substrate including the diaphragm. and constitutes the other end of the force-transmitting rod and a pressure receiving portion,
Further, the Young's modulus of the sensor substrate is about 130 GPa or more.
And the Young's modulus of the force transmission rod is approximately 20
It is in the range of 80 GPa, and the width of this force transmission rod
Is at least 1.2 times the width of the diaphragm,
The length dimension of the above-mentioned force transmission rod is
It is characterized by being at least 1.0 times.

[0007]

[0008]

[0009]

According to a second aspect of the present invention, there is provided a semiconductor pressure sensor.
In the configuration, a base member, a sensor substrate including the semiconductor piezoresistive element, and a case member that covers the outside of the force transmission rod are provided, and the inner surface side of the pressure receiving diaphragm provided at one end of the case member is provided with the force transmission rod. The pressure receiving diaphragm is brought into contact with the other end, and the outer surface of the pressure receiving diaphragm is brought into contact with the pressure detection medium.

According to a third aspect of the present invention, there is provided a semiconductor pressure sensor according to the second aspect.
In the above structure, the base, the sensor substrate including the semiconductor piezoresistive element, and the force transmission rod are supported by the case member so as to be movable in the length direction of the force transmission rod.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The base and sensor substrate of the semiconductor pressure sensor 10 are basically configured in the same manner as the conventional example of FIG. That is, as shown in FIG. 1, a sensor substrate 12 made of, for example, n-type silicon having a thickness of about several hundred μm or less is provided on a base 11 made of metal, glass, ceramics, or the like. A groove 12a having a constant depth, for example, about 100 to 200 μm is provided on the back surface near the center of the sensor substrate 12 so that the base 1
A gap is formed between the diaphragm portion 1 and the portion of the sensor substrate 12 whose thickness is reduced by the groove 12a.
2b. When the sensor substrate 12 is formed of silicon, its Young's modulus is 130 to 190 GPa.
It is about.

As shown in FIG. 2, the sensor substrate 12 is formed, for example, in a square shape having a side size S of about 2 to several mm when viewed from above, and has a groove 12a, that is, a width dimension of the diaphragm portion 12b. W is about several hundred to 1,000 μm,
The depth B of the diaphragm portion 12b is set to about 1.5 to 3 mm. Then, for example, four piezoresistive elements 13a to 13d are provided on the surface of the diaphragm 12b.
Is provided. Each piezoresistive element 13a to 13d
Is composed of p-type silicon, and two piezoresistive elements 13a and 13d are provided at the center of the diaphragm 12b.
The other two piezoresistive elements 13b and 13c are provided at the periphery (both ends in the width direction) of the diaphragm 12b.

As shown in FIG. 3, the piezoresistive elements 13a to 13d include, for example, a piezoresistive element 13b.
It is formed in a bent shape when viewed from above, and has electrodes 14 at both ends.
Are provided, and lead wires (not shown) are drawn from these electrodes 14. Each piezoresistive element 13
a to 13d, for example, it is connected to the lead wirings so as to constitute a bridge circuit shown in FIG. 4, while the piezoresistive elements 13a, 13c and between 13b, the input voltage V _in across 13d is applied, the piezo Resistance elements 13a, 13b
The output voltage _Vout is taken _out from between and between 13c and 13d.

Here, each of the piezoresistive elements 13a to 13a
The resistance value of d is R₁Or R_FourAnd the diaphragm part 1
Of the two piezoresistive elements 13a and 13d at the center of
Resistance value R₁= R_Four= R_CTwo peripheral piezoresistors
Resistance value R of child 13b, 13c _Two= R_Three= R_SThen
The following equation (4) holds in the circuit of FIG. V_out= (ΔR_S/ R_S-ΔR_C/ R_C) V_in/ 2 (4)

In FIG. 1, a flat lower end portion (one end portion) of a cylindrical force transmission rod 15 is adhered to the surface of a sensor substrate 12 including a diaphragm 12b provided with piezoresistive elements 13a to 13d by bonding or the like. Are joined. The force transmitting rod 15 extends in a direction perpendicular to the surface of the sensor substrate 12, and a flat bottom surface of a hemispherical head 16 (pressure receiving portion) is bonded to the flat upper end (other end) by bonding or the like. . Here, the diameter of the head 16 is
5, but the diameter of the head 16 may be smaller or larger than the diameter of the force transmitting rod 15. The head 16 receives a pressure near the apex thereof and plays a role of transmitting the pressure substantially uniformly to each part in the cross section of the force transmission rod 15.

The force transmitting rod 15 is formed of a material having a Young's modulus smaller than that of the sensor substrate 12, specifically, a metal, glass or resin material having a Young's modulus in a range of 20 to 80 GPa. The diameter D of the force transmission rod 15
Is, for example, about 1 to 2 mm, and the length L (height) is, for example, about 1.5 to 3 mm.

FIG. 5 shows a sensor base via a force transmitting rod 15.
Diaphragm 12 when downward force is applied to plate 12
4 schematically shows a stress distribution around b. Response in x, y, z directions
Force σ _x, Σ_y, Σ_zPolarity, that is, whether it is compressive stress
Whether the tensile stress depends on the crystal orientation of silicon
Is a diaphragm in which the piezoresistive elements 13a and 13b are located.
In the vicinity of the center of the ram portion 12b, for example, stress in the x direction
σ_xTakes a negative value, in this case, the diaphragm portion 12b
Near the periphery (both ends in the width direction)_xIs a positive value
You.

On the other hand, in this case, the stress in the y and z directions is
The values near the center and the periphery of the diaphragm portion 12b are negative values, and the absolute values of σ _y and σ _z are sufficiently smaller than the absolute values of σ _x near the center of the diaphragm portion 12b. Can be considered. The stress distribution in the present embodiment shown in FIG.
Formula 03 see) (1) ΔR / R = π x σ x + π y σ
_When applied to _y + π _z σ _z , the absolute value of σ _y , σ _z is approximated to zero near the center of the diaphragm portion 12b, whereby the absolute value of the rate of change in resistance ΔR / R of the piezoresistive elements 13a, 13b is obtained. [ΔR / R] is represented by the following equation (5). [ΔR / R] = [π _x σ _x ] (5) When this equation (5) is compared with the equation (3) (paragraph number 0005) of the conventional semiconductor pressure sensor, in this embodiment, X
It can be understood that the components in the Y direction and the Y direction do not cancel each other, and the detection sensitivity can be improved by more effectively using the piezoresistance effect.

In the vicinity of the periphery of the diaphragm portion 12b, σ _x , σ _y , and σ _z have opposite polarities, and as described above (paragraph number 0004), the piezoresistance coefficients π _x , π _y , π _z Are also of opposite polarity, and from the above equation (1), the rate of change in resistance of the piezoresistive elements 13c and 13d ΔR / R
Is represented by the following equation (6). [[Delta] R / R] = [[pi] _x [sigma] _x ] + [[pi] _y [sigma] _y ] + [[pi] _z [sigma] _z ] (6) As described above, in the vicinity of the periphery of the diaphragm 12b, Is added.
The piezoresistive effect can be used more effectively than a conventional semiconductor pressure sensor.

It should be noted that the stresses σ _x , σ _y ,
The slope of the curve showing the distribution of σ _z depends on conditions such as the Young's modulus of the material constituting the force transmission rod 15, the ratio of the diameter D to the length L of the force transmission rod 15, the thickness of the diaphragm portion 12b, and the like. And depending on the combination of these conditions,
The value of σ _x near the periphery of the diaphragm portion 12b in (2) takes a negative value, and the above equations (5) and (6) may not be satisfied.

Therefore, the present inventor has proposed a FEM (Finite Eleme).
nt Method: Finite Element Method)
While changing various combinations of the four conditions of the Young's modulus of 5, the length L of the force transmission rod 15, the diameter D of the force transmission rod 15, and the thickness of the diaphragm portion 12b,
By analyzing numerically the distribution of the stresses σ _x , σ _y , and σ _z in each direction, the above-described Young's modulus and suitable ranges of various dimensions were obtained. Here, the thickness of the sensor substrate 12 is 300 μm,
The dimension S of one side of the sensor substrate 12 was 3000 μm, the width W of the diaphragm portion 12b was 750 μm, and the depth B was 2000 μm. The analysis conditions are shown below.

(1) Analytical Model A 1/4 model composed of the sensor substrate 12 and the force transmitting rod 15 was used. (2) Boundary conditions All nodes on the lower surface of the sensor substrate 12 were completely constrained in the x, y, and z directions. 1/4
Since this is a model, points on the y-axis are constrained in the x direction, and points on the x-axis are constrained in the y direction. (3) Load Condition As a load condition, 37.5 N was applied to the center of the upper surface of the force transmission rod 15. (4) Material properties Silicon is treated as an isotropic material for ease of analysis, and Young's modulus is 170
GPa and Poisson's ratio = 0.25.

An analysis is performed based on the above conditions, and the Young's modulus of the force transmitting rod 15 is 70 GPa, and the force transmitting rod 15
The length L = 2.0 mm, the diameter D = 1.5 mm, and the thickness of the diaphragm 12b = 200 μm were used as standard models. With respect to this standard model, the diaphragm unit 1 when each of the above items was changed within the range shown in Table 1 below
Changes in the stress components σ _x , σ _y , σ _z acting on 2b were obtained by the FEM analysis.

[0025]

[Table 1]

FIGS. 6 to 8 show an example of the analysis results, where the Young's modulus of the force transmitting rod 15 in Table 1 is 20 to 210.
The distribution of stress components σ _x , σ _y , and σ _z in the x, y, and z directions when the parameters are changed in the range of GPa and other parameters are used as the values of the standard model are shown. The horizontal axis in each drawing is the distance from the center of the diaphragm 12b in the width direction. Since the width W of the diaphragm 12b is 750 μm, the distance at the width direction end of the diaphragm 12b is 375 μm.

As is clear from FIGS. 6 to 8, the lower the Young's modulus, the greater the absolute value of each stress component, and the better the detection sensitivity (see equations (5) and (6)). In order to obtain the necessary detection sensitivity and to make the stress component σ _x in the peripheral portion of the diaphragm portion 12b have a positive polarity, the Young's modulus of the force transmission rod 15 is preferably in the range of 20 to 80 GPa as described above. .

Next, regarding the piezoresistive elements 13a and 13d at the center of the diaphragm section 12b and the piezoresistive elements 13b and 13c at the periphery, when the four types of parameters shown in Table 1 are changed, the piezoresistors at the center are changed. Element 13
9 to FIG. 9 to FIG. 9 to FIG. 9 show the calculation results of how the resistance change rate ΔR _C / R _{C of the} a and 13d and the resistance change rate ΔR _S / R _{S of the} peripheral piezoresistive elements 13b and 13c change. FIG.

FIG. 9 shows the relationship between the Young's modulus of the force transmission rod 15 and the resistance change rate. The curve I represents the resistance change rate ΔR _C / R _C of the piezoresistive elements 13a and 13d at the center of the diaphragm 12b. And a curve II represents a resistance change rate ΔR _S / R _S of the piezoresistive elements 13b and 13c at the peripheral portion. As described above, when the Young's modulus is in the range of 20 to 80 GPa, the absolute value of the resistance change rate is relatively large, and good sensitivity is easily obtained.

FIG. 10 shows the relationship between the length L (height) of the force transmitting rod 15 and the rate of change in resistance. The curve I represents the piezoresistive elements 13a, 13a, 1b at the center of the diaphragm 12b.
The resistance change rate ΔR _C / _RC of 3d, and the curve II shows the resistance change rate ΔR _S / R of the peripheral piezoresistive elements 13b and 13c.
R _S. As is clear from the curves I and II, when the length L is 1.5 mm or more, the resistance change rate is substantially constant. However, when the length L is 1.5 mm or more, the stress components σ _x ,
This is because the magnitudes of σ _y and σ _z are substantially constant. Therefore, it is preferable that the length L of the force transmission rod 15 be 1.5 mm or more.

FIG. 11 shows the relationship between the diameter D of the force transmitting rod 15 and the resistance change rate. The curve I shows the resistance change rate ΔR _C / R _C of the piezoresistive elements 13a and 13d at the center of the diaphragm 12b. And a curve II represents a resistance change rate ΔR _S / R _S of the piezoresistive elements 13b and 13c at the peripheral portion. As is clear from the curves I and II, the smaller the diameter D, the better the sensitivity. However, if the diameter D is too small, the peak position of the stress in the outer peripheral portion of the force transmitting rod 15 becomes close to the position where the piezoresistive elements 13b and 13c are provided in the peripheral portion of the diaphragm portion 12b. There is a possibility that the variation in output characteristics due to an alignment error at the time of attachment to the sensor substrate 12 increases. Therefore, it is preferable that the diameter D is approximately 1.2 times or more, for example, 1.0 mm or more, of the width W (750 μm in this case) of the diaphragm portion 12b.

The length L of the force transmitting rod 15
Is 1.5 mm or more and the diameter D is about 1.5 mm, as described above, when the thickness of the sensor substrate 12 is 300 μm, the dimension S of one side is 3000 μm, and the width W of the diaphragm 12 b is 750 μm. The corresponding size,
Depending on the application of the semiconductor pressure sensor 10, etc., the sensor substrate 1
When the size of the diaphragm 2 or the size of the diaphragm portion 12b is changed, the optimum values of the length L and the diameter D of the force transmission rod 15 naturally change accordingly. Therefore, the length L of the force transmission rod 15
The ratio of the diameter D to the diameter D is more important, but the ratio may be determined as long as the length L is equal to or larger than the diameter D.

FIG. 12 shows the relationship between the thickness of the diaphragm portion 12b and the resistance change rate. A curve I represents the resistance change rate ΔR _C / R _C of the piezoresistive elements 13a and 13d at the center of the diaphragm portion 12b. , Curve II represents the resistance change rate ΔR _S / R _S of the peripheral piezoresistive elements 13b and 13c. As is clear from the curves I and II, the piezoresistive elements 13a and 13d at the center have little change at the thicknesses of 200 μm and 150 μm, and the resistance change rate ΔR at 100 μm or less.
_C / _RC approaches zero.

The peripheral piezoresistive elements 13b and 13c have the largest resistance change rate ΔR _S / R _S when the thickness is 100 μm. Considering the balance between the central part and the peripheral part,
The one with 50 μm has the best sensitivity. The thickness of 150 μm at which the optimum sensitivity is obtained is also a value when the width W of the diaphragm 12b is 750 μm, and when the width itself of the diaphragm 12b changes, the diaphragm for obtaining the optimum sensitivity is obtained. It goes without saying that the thickness of the portion 12b also changes accordingly.

Based on the above analysis results, a semiconductor pressure sensor 10 having the outer shape shown in FIG. 1 and the dimensions shown in the standard model of Table 1 was actually manufactured. That is, duralumin having a Young's modulus of 70 GPa is used as the material of the force transmission rod 15, the length L is 1.8 mm, and the diameter D is 1.5.
mm and the diameter of the head 16 is 1.0 mm,
Further, as described above, the dimension S of one side of the sensor substrate 12 is set to 30.
The thickness of the sensor substrate 12 was 300 μm, the width W of the diaphragm portion 12b was 750 μm, and the depth B was 2000 μm. The base 11 has a diameter of 20 mm.
A disk-shaped stainless steel having a thickness of 1.0 mm and a thickness of 1.0 mm was used, and an epoxy-based adhesive was used for bonding each part.

A load of up to 150 N was applied to the semiconductor pressure sensor 10 using a universal tester (Model 4206 of INSTRON), and the results of actually measuring the resistance change rates of the piezoresistive elements 13a to 13d are shown in FIG. 13 shows each curve I
To IV. As is clear from FIG. 13, the resistance change rate changes substantially in proportion to the load. In the present invention,
Since the external force is applied to the sensor substrate 12 via the force transmission rod 15 instead of directly applied thereto, it is possible to measure a high pressure of up to about 150 N, which is about twice as high as that of a conventional semiconductor pressure sensor.

The semiconductor pressure sensor 10 actually manufactured above
FIG. 14 shows the result of measuring the relationship between the load and the output voltage V _out (see the equation (4) in paragraph 0015) by using FIG. It should be noted that the input voltage V _in is set to 5V. As is clear from FIG. 14, there is a substantially proportional relationship between the load and the output voltage.

Next, an embodiment in which the semiconductor pressure sensor 10 is housed in a case member is shown in FIG. Each part of the semiconductor pressure sensor 10 has the same configuration as that of FIG. 1, and common parts are denoted by the same reference numerals. For example, the case member 20 made of a metal such as stainless steel is formed in a substantially columnar shape with an open lower part, and the pressure receiving diaphragm 2
1 and the pressure receiving diaphragm 2
A bulging portion 21a that bulges downward is provided at the center of 1. A female screw 20a is formed on the inner peripheral surface near the lower end of the case member 20, and a male screw 20b for attachment to the pressure detection site is formed on the outer peripheral surface.

A metal adjustment member 22 is arranged at a lower portion in the case member 20, and the semiconductor pressure sensor 10 is fixed on the adjustment member 22. The adjusting member 22 is vertically movable with respect to the case member 20 together with the semiconductor pressure sensor 10 when a male screw 22a provided on the outer periphery is screwed into the female screw 20a. Semiconductor pressure sensor 10
When accommodating in the case member 20, the case member 20
The adjustment member 22 with respect to the semiconductor pressure sensor 1
The semiconductor pressure sensor 10 may be adjusted so as to obtain an appropriate sensitivity by moving the head 0 up and down in the case member 20 and adjusting the contact state of the head 16 with the bulging portion 21a.

Thereafter, the semiconductor pressure sensor 10 is attached to a pressure detection site, for example, an injection molding machine or the like, together with the case member 20 with a male screw 20b or the like, and the pressure detection medium is applied to the outer surface side (upper surface side) of the pressure receiving diaphragm 21. If you touch
The pressure at the pressure detection site is transmitted to the head 16 via the pressure receiving diaphragm 21, and the pressure is detected by the semiconductor pressure sensor 10.

In the above embodiment, the sensor substrate 12 and the piezoresistive elements 13a to 13d are formed of n-type and p-type silicon. However, the sensor substrate 12 and the piezoresistive elements 13a to 13d are formed of p-type and n-type Of silicon. Further, the sensor substrate 12 and the piezoresistive elements 13a to 13d may be formed of another semiconductor such as germanium. Also, the piezoresistive elements 13a to 13a
The number of 3d can be any number of 2 or more.

Further, the force transmission rod 15 may be formed in a shape other than a cylinder, such as a prism, etc., and the head 16 having a hemispherical shape is not necessarily required as long as the force can be transmitted substantially uniformly in each section in the cross section of the force transmission rod 15. No need to provide. The force transmission rod 15 can be formed of various materials such as metals or alloys other than the above duralumin, glass, and synthetic resin as long as the material has a Young's modulus in a range of about 20 to 80 GPa.

[0043]

According to the semiconductor pressure sensor of the first aspect of the present invention, a groove having a predetermined depth is provided on the back surface of a sensor substrate provided on a base to form a gap between the sensor and the base. A portion of the sensor substrate provided with the groove is a diaphragm portion, and in a semiconductor pressure sensor having a semiconductor piezoresistive element provided on a surface portion of the diaphragm portion, the surface of the sensor substrate including the diaphragm portion is provided with a surface of the sensor substrate. A flat end of a force transmission rod extending in a direction substantially perpendicular to the end is joined, and the other end of the force transmission rod is used as a pressure receiving portion. Instead of applying pressure directly to the diaphragm portion of the sensor substrate as in the related art. Since the pressure is applied to the diaphragm through the force transmission rod, even if a higher pressure is applied to the other end of the force transmission rod than before, the force is absorbed by the force transmission rod. Without because the pressure is transmitted directly to the sensor substrate, it is possible to measure the pressure higher than the conventional as a result.

[0044]

[0045]

[0046] Further, substantially the Young's modulus of the upper Symbol sensor substrate 13
0 GPa or more, the Young's modulus of the force transmission rod is in the range of approximately 20 to 80 GPa, the width of the force transmission rod is 1.2 times or more the width of the diaphragm, and the length of the force transmission rod is The dimensions are 1.0 times or more of the width dimension of the force transmission rod, and the present inventor repeats the experiment, whereby the semiconductor pressure sensor can withstand higher pressure by the above setting,
It has been found that the pressure detection sensitivity can be further improved. Note that the pressure is detected by the above setting.
The reason that the sensitivity is improved is that the piezoresistive element
The above equation ΔR / R = πxσ indicating the rate of resistance change ΔR / R
x + πyσy + πzσz (see paragraph 0003)
And πyσy and πzσz can be made substantially zero.
Or πyσy and πzσz have the same polarity as πxσx
This makes it possible to increase the absolute value of ΔR / R.
This is because

According to a second aspect of the present invention, there is provided a semiconductor pressure sensor according to the first aspect.
In the configuration, a base member, a sensor substrate including the semiconductor piezoresistive element, and a case member that covers the outside of the force transmission rod are provided, and the inner surface side of the pressure receiving diaphragm provided at one end of the case member is provided with the force transmission rod. The pressure receiving diaphragm is brought into contact with the other end, and the outer surface side of the pressure receiving diaphragm is brought into contact with the pressure detection medium. By providing the case member, the durability of the semiconductor pressure sensor is improved, and the life is extended. In addition to this, there is an advantage that work such as attachment of the semiconductor pressure sensor to the pressure detection site can be easily performed.

According to the third aspect of the present invention, there is provided a semiconductor pressure sensor according to the second aspect.
In the above structure, the base, the sensor substrate including the semiconductor piezoresistive element, and the force transmission rod are supported by the case member so as to be movable in the longitudinal direction of the force transmission rod. By moving the case member relative to the case member, the abutting condition of the other end of the force transmitting rod with respect to the pressure receiving diaphragm of the case member is adjusted, so that the detection sensitivity by the semiconductor piezoresistive element becomes the best. can do.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a semiconductor pressure sensor according to an embodiment of the present invention.

FIG. 2 is a schematic plan view showing a sensor substrate of the semiconductor pressure sensor.

FIG. 3 is an enlarged explanatory view showing a piezoresistive element of the semiconductor pressure sensor.

FIG. 4 is a circuit diagram showing a connection relationship of lead wires from each piezoresistive element of the semiconductor pressure sensor.

FIG. 5 is an explanatory diagram showing a stress distribution in a diaphragm portion of the semiconductor pressure sensor.

FIG. 6 is a graph showing the result of analyzing the distribution of stress components in the x direction in the diaphragm of the semiconductor pressure sensor.

FIG. 7 is a graph showing a result of analyzing a distribution of a stress component in a y-direction in a diaphragm portion of the semiconductor pressure sensor.

FIG. 8 is a graph showing a result of analyzing a distribution of a stress component in a z-direction in a diaphragm portion of the semiconductor pressure sensor.

FIG. 9 is a graph showing a calculation result of a relationship between a Young's modulus of a force transmission rod of the semiconductor pressure sensor and a resistance change rate of a piezoresistive element.

FIG. 10 is a graph showing a calculation result of a relationship between a length of a force transmission rod of the semiconductor pressure sensor and a resistance change rate of a piezoresistive element.

FIG. 11 is a graph showing a result obtained by calculating a relationship between a diameter of a force transmission rod of the semiconductor pressure sensor and a resistance change rate of a piezoresistive element.

FIG. 12 is a graph showing a calculation result of a relationship between a thickness of a diaphragm portion of the semiconductor pressure sensor and a resistance change rate of a piezoresistive element.

FIG. 13 is a graph showing the results of measuring the relationship between the load and the rate of change of resistance in a semiconductor pressure sensor of the present invention actually manufactured.

FIG. 14 is a graph showing a result of measuring a relationship between a load and an output voltage in an actually manufactured semiconductor pressure sensor of the present invention.

FIG. 15 is an explanatory sectional view showing an embodiment of the present invention in which the semiconductor pressure sensor is housed in a case member.

FIG. 16 is a schematic sectional view showing a conventional semiconductor pressure sensor.

FIG. 17 is an explanatory diagram showing a stress distribution of a diaphragm in a conventional semiconductor pressure sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Semiconductor pressure sensor 11 Base 12 Sensor board 12a Groove 12b Diaphragm part 13a to 13d Piezoresistive element 15 Force transmission rod 17 Case member 21 Pressure receiving diaphragm

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiyama Toshiyuki 1-1-1, Nojihigashi, Kusatsu-shi, Shiga Ritsumeikan University Biwako-Kusatsu Campus Science and Engineering Faculty (72) Inventor Kouji Ota Abe, Sakurai-shi, Nara 49-1 Inside RIKEN Keiki Nara Works, Ltd. (56) References JP-A-2-36327 (JP, A) JP-A-9-126915 (JP, A) JP-A-7-253374 (JP, A) JP-A-7-253364 (JP, A) JP-A-7-176766 (JP, A) JP-A-7-19981 (JP, A) JP-A-6-132543 (JP, A) JP-A-4-257272 ( JP, A) JP-A-2-36575 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01L 1/18 G01L 9/04 101 H01L 29/84 JICST file (JOIS)

Claims (3)

(57) [Claims] 1. A groove having a predetermined depth is provided on a back surface of a sensor substrate provided on a base to form a gap between the sensor substrate and the sensor substrate. And a semiconductor pressure sensor having a semiconductor piezoresistive element provided on the surface of the diaphragm, wherein a force transmitting rod extending in a direction substantially orthogonal to the surface of the sensor substrate is provided on the surface of the sensor substrate including the diaphragm. One end is joined, the other end of the force transmitting rod is configured as a pressure receiving portion , and the Young's modulus of the sensor substrate is substantially reduced.
130 GPa or more and the force transmission rod
Power ratio is in the range of approximately 20 to 80 GPa.
The width of the first rod is equal to the width of the diaphragm.
The force transmission rod is twice or more, and the length of the force transmission rod is
It is at least 1.0 times the width of the rod
Semiconductors pressure sensor. 2. A base member, a sensor substrate including a semiconductor piezoresistive element, and a case member for covering the outside of a force transmission rod are provided, and an inner surface side of a pressure receiving diaphragm provided at one end of the case member is connected to the force transmission rod. the semiconductor pressure sensor according to claim 1 Symbol mounting the other end portion is brought into contact, characterized in that abut the outer surface side of the pressure receiving diaphragm to be pressure detection medium. 3. The force transmitting rod according to claim 2 , wherein the base, the sensor substrate including the semiconductor piezoresistive element, and the force transmitting rod are movably supported by the case member in the longitudinal direction of the force transmitting rod. Semiconductor pressure sensor.