JP2002257645A - High sensitive force detecting sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the sensitivity of a force detecting sensor in which an element such as diode, transistor, etc., is formed in a mesa step formed on the surface of a semiconductor block. SOLUTION: A current path 38 having a piezo resistance is provided on the side of the mesa steps 30, 34, and thereby the coefficient of piezo resistance π11, the value of which is great, can be utilized. In addition, a plane of pn junction is formed, and a diode or a transistor is formed. A force transmitting block with a large area 22 and the mesa step with a small cross-sectional area 30, 32, 34, 36 are utilized, and thereby the force is amplified, and in addition, a sensitively changing phenomenon of the piezo resistance and the semiconductor property act synergistically with each other, and the sensitivity can be improved furthermore.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a force detection sensor that outputs an electric signal according to the magnitude of a force (which may be a pressure) when the force is applied.

[0002]

2. Description of the Related Art The present applicant has developed a force detection sensor capable of detecting the magnitude of an applied force with high sensitivity. This force detection sensor is described in JP-A-8-271363. The basic structure of this force detection sensor will be described with reference to FIG. This force detection sensor uses a semiconductor block (specifically, a silicon single crystal) 10 and a force transmission block (specifically, a crystallized glass block) 20. For clarity of illustration, the force transmission block 20 is shown by a dashed line. The surface of the semiconductor block 10 is mesa-etched to form mesa steps 11 to 14 on the surface of the semiconductor block 10. For convenience of illustration, the mesa step 12 is shown in a broken cross section, but is actually continuous and has a mesa step 11 to 1.
4 forms four sides of a square. In advance, a thin p-doped layer 19 is formed on the surface of the n-type semiconductor block 10, and mesa steps 11 to 14 forming four sides of a square are performed in order to perform mesa etching beyond the depth of the p-doped layer 19. The p-doped layer 19 remains in the vicinity of the surface, and this becomes a current path. By providing the electrodes 15 to 18 at the apexes of the square, current paths (mesa steps 11 to 14) forming four sides of the square are formed.
A Wheatstone bridge is formed by the p-doped layer 19) in the vicinity of the surface. The force transmission block 20 is fixed to the tops of mesa steps 11 to 14 having a constant height and forming four sides of a square.

When a constant current is applied between the diagonal electrodes 15 and 17 or a constant voltage is applied, a voltage is generated between another pair of diagonal electrodes 16 and 18. Square 4
A piezoresistance effect appears in the current path 19 forming a side, and the resistance value of the current path 19 affects the voltage between the electrodes 16, 18. In accordance with the magnitude of the load W acting on the Since the magnitude of the load W is converted into the magnitude of the voltage between the electrodes 16 and 18, when a constant current is applied between the electrodes 15 and 17 or when a constant voltage is applied, the gap between the electrodes 16 and 18 is generated. The magnitude of the load W is detected from the magnitude of the voltage.

This force detection sensor is particularly effective when detecting pressure, and the pressure acting on the surface of the force transmission block 20 is concentrated on the mesa steps 11 to 14, so that it can be detected with high sensitivity. That is, by using the force transmitting block 20 having a large area and the mesa steps 11 to 14 having a small cross-sectional area (cross-sectional area in a plane parallel to the surface of the semiconductor block 10), a force amplification phenomenon can be obtained. Thus, the detection sensitivity can be increased.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to further increase the detection sensitivity. In a conventional force detection sensor, a silicon single crystal (1
10) By making the surface appear, and forming the mesa steps 11 and 13 in the <110> direction and the mesa steps 12 and 14 in the <100> direction, the maximum piezoresistance coefficient can be used. As the direction of the crystal plane and the direction of the current path, a method of obtaining the maximum sensitivity is adopted. However, the maximum sensitivity is the maximum sensitivity under the constraint that the current path 19 extends in a plane perpendicular to the direction of force application, and if this limitation can be removed, the sensitivity can be further increased. is there. Further, a conventional force detection sensor utilizes a piezoresistance effect generated in a current path.
However, the phenomenon that the electrical characteristics change due to the acting stress is not limited to the piezoresistance effect. For example, it is known that when a stress is applied to a pn junction surface of a diode, a relationship established between a forward voltage and a forward current changes. Alternatively, it is known that the relationship established between the reverse voltage and the reverse current also changes. Alternatively, it is known that when a stress is applied between the base and the emitter of the bipolar transistor, the collector current changes even if the base current is constant. Alternatively, it is known that when stress is applied to the gate of a field effect transistor, the drain current changes even when the gate voltage is constant. If the above semiconductor characteristics can be used for a force detection sensor that obtains a force amplification phenomenon by using a large-area force transmission block and a small-mesa step with a small cross-sectional area, it is possible to further increase the sensitivity. is there.

[0006]

One high-sensitivity force detection sensor according to the present invention comprises a semiconductor block having a mesa step formed on its surface and a force transmission block fixed to the top of the mesa step. have. What is unique here is that
A doped layer doped with ions of the conductivity type opposite to that of the semiconductor block is formed on the side surface of the mesa step, and the side surface of the mesa step is selected in a crystal direction having a piezoresistance coefficient. It is.

According to this force detection sensor, the direction in which the force acts and the current path can be arranged in parallel. For this reason, the piezoresistance effect appears remarkably, and the resistance value measured along the current path changes greatly. By excluding the limitation of the conventional detection sensor that the current path extends in a plane perpendicular to the direction of force application, it is possible to obtain high sensitivity that has not been obtained conventionally.

Another high-sensitivity force detection sensor according to the present invention includes a semiconductor block having a mesa step formed on a surface thereof, and a force transmission block fixed to the top of the mesa step. What is characteristic here is that at least one pn junction surface is formed in the mesa step.

When at least one pn junction surface is formed, a semiconductor device such as a diode, a bipolar transistor, or a field effect transistor is formed in the mesa step. The electrical characteristics of these semiconductor devices change significantly more than the piezoresistive effect due to the applied stress. For this reason, the sensitivity of the semiconductor device is added to a force detection sensor of a type that obtains a force amplification phenomenon by using a force transmission block having a large area and a mesa step having a small cross-sectional area. A detection sensor is realized.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the main features of the embodiment described below will be summarized. (Mode 1) A semiconductor block having a mesa step surrounding a closed space formed on the surface thereof, and a force transmission block fixed to the top of the mesa step, wherein ions of the conductivity type opposite to the conductivity type of the semiconductor block are doped. A doped layer extends across the closed space. (Embodiment 2) A sealed space having a semiconductor block having a mesa step surrounding the closed space formed on the surface thereof, and a force transmission block fixed to the top of the mesa step, and defined by the semiconductor block, the mesa step, and the force transmission block. Compressible gas is enclosed. (Embodiment 3) In the above embodiment, the height of the mesa steps surrounding the closed space is uniform. (Embodiment 4) In the above embodiment, a pair of electrodes is formed outside the closed space. (Embodiment 5) In the above embodiment, the current path extending along the surface of the semiconductor block is formed by metal wiring. (Aspect 6) In the above aspect, a mesa step is formed in the closed space, and the doped layer also crosses the mesa step. (Aspect 7) In the above aspect, the mesa step surrounding the closed space is circular. (Embodiment 8) In the above embodiment, the mesa step surrounding the closed space is rectangular. (Mode 9) A layer doped with ions of the conductivity type opposite to the conductivity type of the semiconductor block extends across the plurality of mesa steps. (Mode 10) A doped layer doped with ions of a conductivity type opposite to the conductivity type of the semiconductor block is obliquely oblique to the side surface of the mesa step erecting from the surface of the semiconductor block. (Mode 11) A doped layer doped with ions of a conductivity type opposite to the conductivity type of the semiconductor block extends on a mesa step side surface extending obliquely from the surface of the semiconductor block. (Mode 12) In a high-sensitivity force detection sensor having a semiconductor block having a mesa step formed on the surface and a force transmission block fixed to the top of the mesa step, and having a diode formed in the mesa step, a pn junction surface Are parallel to the top surface of the mesa step. (Mode 13) In a high-sensitivity force detection sensor having a semiconductor block having a mesa step formed on the surface and a force transmission block fixed to the top of the mesa step, and having a diode formed in the mesa step, a pn junction surface Is parallel to the side surface of the mesa step. (Feature 14) In a high-sensitivity force detection sensor having a semiconductor block having a mesa step formed on the surface and a force transmission block fixed to the top of the mesa step, and having a transistor formed in the mesa step, pnp or npn The structure extends parallel to the top surface of the mesa step. (Feature 15) In a high-sensitivity force detection sensor having a semiconductor block having a mesa step formed on the surface and a force transmission block fixed at the top of the mesa step, and having a transistor formed in the mesa step, pnp or npn The structure extends parallel to the side of the mesa step.

[0011]

Embodiment (First Embodiment) FIG. 2 schematically shows a high-sensitivity force detection sensor 21 according to a first embodiment. For clarity of illustration, the force transmission block 22 is shown by a dashed line. 26 in the figure
Is a support stand, width 1.4mm, length 2.0mm, height 0.5m
m is a rectangular parallelepiped. The semiconductor block 24 is fixed on the upper surface of the support 26. In this example, a p-type silicon single crystal block (width 1.4 mm, length 2.0 mm, height 0.
3 mm) is used as the semiconductor block 24. The direction of the semiconductor block 24 is selected such that the depth direction is the <100> direction. Alternatively, <1 in the depth direction
00> may be adopted, and there are 11 equivalent directions shown in Table 2 of Japanese Patent Application No. 2000-127830. A gallium arsenide substrate may be used as the semiconductor block 24. On the surface 24a of the semiconductor block 24, mesa steps 30, 32, 34, 36 are formed. The mesa steps 30, 32, 34, 36 form four sides of a square. Each mesa step has a height of 3 μm and a width of 10 μm. The side of each mesa step is the semiconductor surface 24
It is upright on a. The height of the mesa step can be made 3 μm or more by adopting anisotropic etching or dry etching, and the detection sensitivity can be increased by increasing the height. The height of the mesa step is selected according to the sensitivity required for the force detection sensor. On the surface 24a of the semiconductor block 24, a pair of electrodes 2 is placed at positions facing each other with a pair of facing mesa steps 30, 34 facing each other.
8, 40 are formed. Then, a doped layer 38 extends between the electrodes 28 and 40. As shown in FIG. 3A, an insulating layer 42 is formed on the surface of the semiconductor block 24, and a doped layer 38 is formed immediately below the insulating layer 42.
The doped layer 38 is n-type, and the p-type semiconductor block 24
The doped layer 38 extends between the electrodes 28 and 40. FIG.
(B) shows the surface of the semiconductor block 24 and shows a state where the force transmission block has been removed.

The doped layer 38 has two mesa steps 30, 34.
In the mesa step, there is a portion A extending parallel to the side surface of the mesa step and a portion B extending parallel to the top surface of the mesa step. The part A extending parallel to the mesa step surface is
The semiconductor block 24 extends in the <100> direction. Immediately below the electrodes 28 and 40, contact holes are formed in the insulating layer 42, and the electrodes 28 and 40 are in direct contact with the doped layer 38 by the contact holes.

The doped layer 38 has an impurity concentration of 1 × 10
^{It is 18} atom / cm ³ or 1 × 10 ²⁰ atom / cm ³ , has a width of 10 μm, is extremely thin, and has a resistance of 0.001 Ωcm. Since the impurity concentration is high enough,
The temperature compensation described in paragraphs 0058 to 0062 of Japanese Patent Publication No. 363 is obtained, and the resistance value between the electrodes 28 and 40 is maintained constant against the temperature change. Although the doped layer 38 has a high concentration, it has a high resistance value because it is thin and thin, so that a change in the resistance value can be easily measured.

Mesa steps 30, 32, 3 surrounding a closed space
The force transmission block 22 against the top insulating layer 42
Are anodic bonded and firmly fixed. The force transmission block 22 is formed of crystallized glass and has a width of 1.0 m.
It is a rectangular parallelepiped with a length of 1.0 mm and a height of 0.5 mm. The method of fixing the force transmission block 22 is not limited to anodic bonding, and may be fixed with solder, an adhesive, or the like. Compressible gas is sealed in a closed space surrounded by the mesa steps 30, 32, 34, 36 surrounding the closed space, the semiconductor block 24, and the force transmission block 22. Due to the compressibility, the load (which may be pressure) acting on the surface of the force transmission block 22 is received by the mesa steps 30, 32, 34, and 36, and is applied to the mesa steps 30, 32, 34, and 36. The load is amplified and transmitted.

When a load acts on the mesa steps 30, 34, the dope layer A extending parallel to the side surfaces of the mesa steps acts as a load parallel to the extension of the dope layer A. The doped layer A is formed on the (100) crystal plane (or its equivalent plane) and extends in the <100> direction (or its equivalent direction). For this reason, the resistance in the longitudinal direction of the doped layer A changes according to the piezoresistance coefficient π11. On the other hand, the resistance in the longitudinal direction of the doped layer B extending in parallel to the top surface of the mesa step changes according to the piezoresistance coefficient π13. The piezoresistance coefficient π11 is larger than π13.

In a conventional detection sensor disclosed in Japanese Patent Application Laid-Open No. 8-271363, a piezoresistive coefficient π having a small value is used.
Since only 13 were available, high sensitivity was restricted. In the detection sensor of this embodiment, the piezoresistive coefficient π11 having a large value can be used, so that a high sensitivity which cannot be obtained conventionally can be obtained. Also, by increasing the height of the mesa step, the length of the doped layer A can be increased, and a high mesa step can be formed by anisotropic etching or dry etching technology. For this reason, the sensitivity can be set freely. If the sensitivity is allowed to decrease, the doped layer A is set to (100)
Alternatively, it can be formed on a crystal plane other than the crystal plane equivalent thereto. Further, it may be extended in a direction other than the <100> direction or a direction equivalent thereto. For example, on the (110) plane,
It may be extended in the <1110> direction. In this example,
Although n-type ions are implanted into the p-type semiconductor block 24, p-type ions may be implanted into the n-type semiconductor block 24.

(Improvement Example 1) As shown in FIGS. 4A and 4B, a current path extending parallel to the surface 24a of the semiconductor block 24, that is, a current path having a piezoresistance coefficient of π13 instead of π11. It is preferable to reduce the parasitic resistance component by using the metal wiring 44. In this case, the sensitivity can be further improved. It is preferable to use metal wiring even in a portion where the stress does not change even when a force acts.

(Improved Example 2) As shown in FIGS. 5A and 5B, it is preferable to increase the number of mesa steps traversed by the doped layer 38. In the case of FIG. 5, the mesa steps 30, 32, 3
In the closed space surrounded by 4 and 36, two mesa steps 4
6 and 48 are added, which is 2 times higher than the sensitivity in the case of FIG.
Double sensitivity is obtained.

If an additional mesa step is provided in a closed space surrounded by the mesa steps 30, 32, 34, and 36, and the top surface of the additional mesa step contributes to positioning of the force transmission block, Specifically, the phenomena described in paragraphs [0068] to [0074] of JP-A-8-271363 are obtained, and it is possible to suppress the degree to which the electric signal shifts due to a horizontal load applied to the force transmission block. In addition, deformation of the force transmission block can be suppressed. Eventually, the detection accuracy can be kept high.

(Improvement 3) FIG. 6 shows an improvement in which the mesa step 52 is formed in a tubular shape to avoid stress concentration to improve the breaking strength of the mesa step. When the mesa step 52 is a tubular shape, the stress concentration portion can be eliminated. Further, current flows along the inner side surface of the mesa step 52, and current does not flow on the outer side surface. For this purpose, the electrode 40
Is formed on the top surface of the mesa step 56, and a doped layer is formed on the top surface of the mesa step 54 connecting the mesa steps 52 and 56. A current path connecting the top surface of the mesa step 52 and the electrode 40 may be provided by metal wiring instead of the doped layer. No doped layer is formed on the outer side surface of the mesa step 52. A doped layer A extending along the side surface is formed only on the inner side surface. The opposite electrode 28 is provided on the bottom surface of the mesa step, and the doped layer 50 connects the electrode 28 and the doped layer A extending along the inner side surface of the mesa step 52. Substantially, the doped layer A extending along the inner side surface of the mesa step 52 serves as a current path between the top surface and the bottom surface of the tubular mesa step 52.

In this case, the current path A in which the piezoresistance coefficient π11 contributing to force detection is generated is accommodated in a sealed space surrounded by the cylindrical mesa step 52, the semiconductor block 24 and the force transmission block 22, and Is protected. For this reason, it is suitable for detecting the pressure of corrosive gas or liquid, for example. Piezoresistance coefficient π11 contributing to force detection
In the case where the current path A in which the electric current is generated is accommodated in a sealed space and protected from the outside, the mesa step 52 may be polygonal, not circular. When the mesa step 52 is rectangular, the four inner side surfaces on which the current paths are formed can be equivalent crystal planes, and a stable gauge can be realized.

(Improved Example 4) When the force acting on the force transmission block 22 is not pressure but a contact load, it is not necessary to create a sealed space with a mesa step. As shown in FIG. 7, the sensitivity can be increased by further narrowing the pressure receiving area. In this embodiment, four columnar mesa steps 58, 60, 6
2, 64 support the force transmission block 22 and
Extend across the two mesa steps 60, 64.

(Modification 5) The Wheatstone bridge shown in FIG. 9 can be formed by utilizing the side surface of the mesa step. FIGS. 8A and 8B show an example in which four resistors R1, R2, R3, and R4 are formed using side surfaces of a mesa step formed on the (100) plane of an n-type silicon single crystal wafer. Have been. Each resistor extends back and forth between two mesa steps, and, as a result, eight resistors extending along the side surface of the mesa step are connected in series. Resistance R1, R4
A region larger than the region in which is formed, here, the mesa step and its surrounding region are formed to a p-type region (pweld) to a predetermined depth.
1), an n-type doped layer is formed in the p-type region to form n-type resistors R1 and R4. Resistance R
As for R2 and R3, p-type doped layers are formed in an n-type silicon single crystal wafer to form p-type resistors R2 and R3. As a result, the resistors R1 and R4 become (10
0) n-type resistance (gauge) extending in the <100> direction on the surface
And the resistors R2 and R3 set the (100) plane to <100>.
It becomes a p-type resistance (gauge) extending in the direction. in this case,
The piezoresistance coefficient π11 of the gauges R1 and R4 is
It is larger than the piezoresistance coefficient π11 of R3. By utilizing this resistance change, a meaningful Wheatstone bridge is formed. In the figure, a, b, c, and d are metal wirings and terminals. In order to stably operate the Wheatstone bridge, the highest potential is applied to the n-type substrate, and
It is preferable to apply the lowest potential to the mold region (pwell). For this purpose, an n-type substrate and a p-type region (pwell)
Is preferably provided with a contact for connecting to an external voltage. In the (100) plane, <10
The <0> direction and the <110> direction form 45 degrees. For this purpose, n-type resistors (gauges) extending the (110) plane in the <100> direction are defined as resistors R1 and R4, and p-type resistors extending the (110) plane in the <100> direction are defined as resistors R2 and R3. can do. Also in this case, the piezoresistance coefficients π11 of the gauges R1 and R4 are larger than the piezoresistance coefficients π11 of the gauges R2 and R3. As shown in FIGS. 8C and 8D,
A (110) plane can be used to form a Wheatstone bridge. In this case, the <100> direction and the <11
The 0> directions are orthogonal. In this case, the resistors R1 and R4 are (1
00) plane is an n-type extending in the <110> direction, and the resistance R
2 and R3 are p-type extending in the <110> direction on the (110) plane. In this case, the piezoresistance coefficients π11 of the gauges R1 and R4 are smaller than the piezoresistance coefficients π11 of the gauges R2 and R3. In the above, a meaningful Wheatstone bridge is constructed even if n and p are completely inverted. As shown in FIGS. 8E and 8F, the force transmission block transmits the load to the resistances R1 and R4 and does not transmit the load to the resistances R2 and R3. pwel
A bridge can be formed without forming 1).
Further, as shown in FIG. 8 (g), a bridge can be formed by changing the cross-sectional shape of the mesa step and making the resistance changes of the resistors R1 and R4 and the resistance changes of the resistors R2 and R3 different. In this case, since the resistors R1 and R4 are formed at the mesa steps having a large cross-sectional area, the change in stress is small and the change in resistance is small. Since the resistances R2 and R3 are formed in a mesa step having a small cross-sectional area, the change in stress is large and the change in resistance is large. Even in this way, a meaningful Wheatstone bridge is formed.

(Improved Example 6) As shown in FIG. 10, the length of the current path extending along the side surface of the mesa step can be increased. The main series resistance is formed. The sensitivity is increased 7 times. Further, the side surface of the mesa step may extend obliquely from the surface of the semiconductor block. In this case, the mechanical strength can be improved.

(Second Embodiment) A second embodiment is an example in which a diode is formed in a mesa step, and a force is detected by using a phenomenon in which the electrical characteristics of the diode change with a load.
As shown in FIG. 11, the force detection sensor 121 is fixed to a semiconductor block (specifically, an n-type silicon single crystal) 124 having a pressure receiving mesa step 132 formed on the surface thereof, and fixed to the top of the mesa step. It has a force transmission block 122. The pressure receiving mesa step 132 has four sides in the positive direction. In addition to the pressure receiving mesa step 132, a mesa step 126 for the electrode 128 and a connection for connecting the pressure receiving mesa step 132 and the electrode mesa step 126. A mesa step 130 is formed.

The surface of the semiconductor block 124 and the upper surfaces and side surfaces of the mesa steps 126, 130 and 132 are
42. Mesa steps 126, 130, 132
Immediately below the insulating layer 142 covering the upper surface, a p-doped layer 134 having a conductivity type opposite to the conductivity type of the semiconductor block 124, that is, p-type ions implanted and diffused (having a thickness of about 1 μm).
m) is formed. Actually, the p-doped layer 1
Anisotropically etching the silicon substrate on which 34 has been formed,
A semiconductor block 124 having mesa steps 126, 130, 132 formed on the surface is formed. A diode 133 having a pn junction surface is formed in the pressure receiving mesa step 132.

On the surface of the electrode mesa step 126, a p-electrode 128 for connecting to the p-doped layer 134 is formed, and the p-electrode 128 and the p-doped layer 134 are connected to the insulating layer 142.
Are connected by a contact hole formed in the contact hole. An n-electrode 140 is formed on the surface 124 a of the semiconductor block 124, and the n-electrode 128 and the n-type semiconductor block 124 are connected by a contact hole formed in the insulating layer 142. As described above, the p-layer 134 and the n-layer 12 are located between the p-electrode 128 and the n-electrode 140.
4 are formed.

In the case of a diode, a stress is applied to the pn junction surface, so that the electrical characteristics change sharply.
When a constant forward current flows between the p-electrode 128 and the n-electrode 140, as shown in FIG. 12, as the compressive stress acting on the pn junction increases, the voltage between the p-electrode 128 and the n-electrode 140 increases. Becomes smaller. By utilizing this characteristic, the magnitude of the stress acting on the pn junction surface, and consequently,
The magnitude of the force acting on the force transmission block 122 can be detected. In this force detecting sensor, a method of applying a constant reverse voltage between the p-electrode 128 and the n-electrode 140 and measuring the reverse current flowing at that time to detect the force can also be used. In this case, as the compressive stress increases,
A large reverse current flows.

In the example shown in FIG.
The joining surface extends parallel to the top surface of the pressure receiving mesa step 132. Alternatively, the direction in which the pn junction surface of the diode extends parallel to the side surface of the pressure receiving mesa step 132 may be adopted.

(Improvement Example 1) As shown in FIG. 13, a diode may be formed only in a part of the pressure receiving mesa step 132. In this case, the p-doped layer 154 is formed only in a limited range.

(Improved Example 2) As shown in FIG. 14, the p-electrode 128 is extended along the connection mesa step 130 to the upper part of the pressure receiving mesa step 132, and the extended electrode 128a and the p-doped layer 154 are connected. Alternatively, the connection may be made through a contact hole formed in the insulating layer 142. In this case, the mesa step 13
Although the heights of the top surfaces of the contact surfaces 0 and 132 in contact with the force transmission block 122 are not uniform, the force transmission can be performed by making the width of the connection mesa step 130 wider than the width of the extended electrode 128a. Block 122 can be anodically bonded to semiconductor block 124. Also, the extended electrode 128
The thickness of “a” can be made sufficiently thin. Further, on the top surface of the connecting mesa step 130, the extended electrode 128a
Can be etched in advance by the thickness of the electrode 128a.

(Improved Example 3) As shown in FIG. 17, in addition to the pressure receiving mesa step 132, the pressure receiving mesa step
The diode may be formed by providing the upper layer 60 and the upper layer 166 and the lower layer 168 with opposite conductivity types. In this case, a mesa step 162 for connection that passes from one side of the electrode mesa step 126 to one side of the pressure receiving mesa step 132 and reaches the center pressure receiving mesa step 160 is provided, and an extended portion of the electrode is formed on the upper surface thereof. . Instead of forming the current path by extending the electrode, the current path may be secured by a layer into which ions are implanted and diffused.

(Improvement 4) In the above, a sensor in the case where pressure is applied to the surface of the force transmission block has been introduced. Since the pressure receiving mesa steps continuously make one round, pressure is not applied to the back surface of the force transmission block, and the pressure applied to the large surface of the force transmission block can be concentrated on the pressure receiving mesa step with a small cross-sectional area. it can. High detection sensitivity is realized by utilizing the power amplification mechanism and diode sensitivity. When a contact load acts on the surface of the force transmission block, the pressure receiving mesa step does not need to continuously make one round.

(Embodiment 3) A third embodiment is an example in which a bipolar transistor is formed in a mesa step for receiving pressure, and a force is detected by utilizing a phenomenon in which the electrical characteristics of the bipolar transistor change with a load. As shown in FIG. 16, the force detection sensor includes a semiconductor block (specifically, an n-type silicon single crystal) 224 having a pressure receiving mesa step 236 formed on the surface thereof, and a force fixed to the top of the mesa step. It has a transmission block 222. The pressure receiving mesa step 236 forms four sides in the positive direction, and in addition to the pressure receiving mesa step 236,
A mesa step 226 for the emitter electrode 228 and the base electrode 230, a mesa step 236 for receiving pressure, and a mesa step 2 for the electrode.
26, a connection mesa step 234 is formed.

The surface of the semiconductor block 224 and the upper surfaces and side surfaces of the mesa steps 226, 234, and 236 are
42. Immediately below the insulating layer 242 covering the upper surface of the pressure receiving mesa step 236, an n-doped layer 238 in which the same conductivity type as the semiconductor block 224, that is, n-type ions are implanted and diffused is formed. n-doped layer 2
Below p is formed a p-doped layer 240 into which ions of the opposite conductivity type, that is, p-type ions are implanted and diffused. Below the p-doped layer 240 is an n-type silicon block 224.
It has become. In the pressure receiving mesa step 236, n
The pn layers are stacked to form a vertical bipolar transistor.

An emitter electrode 228 for connecting to the n-doped layer 238 is formed on the surface of the electrode mesa step 226, and the emitter electrode 228 and the n-doped layer 238 are formed by contact holes formed in the insulating layer 242. It is connected. Further, a base electrode 23 for connecting to the p-doped layer 240 is provided on the surface of the electrode mesa step 226.
0, the base electrode 230 and the p-doped layer 2
Reference numerals 40 are connected by contact holes formed in the insulating layer 142. The emitter electrode 228 and the base electrode 230 are insulated. A collector electrode 232 is formed on the surface 224a of the semiconductor block 224, and the collector electrode 232 and the n-type semiconductor block 224 are formed.
Are connected by contact holes formed in the insulating layer 242.

As understood from the above, the n-layer 238
(Functions as an emitter region), a p-layer 240 (functions as a base region), and an n-layer 224 (functions as a collector region) are stacked vertically to form a bipolar transistor having an emitter electrode 228 and a base electrode 230.
And a semiconductor device to which the collector electrode 232 is connected.

In the case of a bipolar transistor, the base 2
It is known that when a stress is applied between 40 and emitter 238, the collector current changes even if the base current is constant. By utilizing this characteristic, the pressure receiving mesa step 2
It is possible to detect the magnitude of the stress acting on 36 and, consequently, the magnitude of the force acting on the force transmission block 222.

(Improvement Example 1) As shown in FIG. 17, a lateral bipolar transistor can be formed in the pressure receiving mesa step 236. For this purpose, a p-doped layer 260 is formed near the upper surface of the pressure receiving mesa step 236 of the n-type semiconductor block 224. In the p-doped layer 260, two n-doped layers 262, 2
64 are formed. The outer n-doped layer 262 is connected to the emitter electrode 228, and the p-doped layer 260 is connected to the base electrode 23.
0, and the inner n-doped layer 264 is connected to the collector electrode 2
32.

As a result, a horizontal npn structure is realized in the pressure-receiving mesa step 236, and a horizontal bipolar transistor is formed. Also in the case of this detection sensor, the magnitude of the stress acting on the pressure receiving mesa step 236 and, consequently, acting on the force transmission block 222 are detected by detecting the change in the collector current while keeping the base current constant. Detect the magnitude of the force.

(Embodiment 4) The fourth embodiment is an example in which a field effect transistor is formed in a mesa step for receiving pressure, and a force is detected using a phenomenon in which the electric characteristics of the field effect transistor change with a load. It is. As shown in FIG. 18, this force detection sensor includes a semiconductor block (specifically, a p-type silicon single crystal) 324 having a pressure-receiving mesa step 342 formed on the surface thereof, and a force fixed to the top of the mesa step. It has a transmission block 322. The pressure receiving mesa step 342 forms four sides in the positive direction, and in addition to the pressure receiving mesa step 342,
Source electrode 336, gate electrode 334, and drain electrode 3
32, and a mesa step 342 for receiving pressure.
Connecting mesa step 34 connecting the electrode mesa step 338
0 is formed.

The surface of the semiconductor block 324 and the upper and side surfaces of the mesa steps 338, 340 and 342 are
46. Immediately below the insulating layer 346 covering the upper surface of the pressure receiving mesa step 342, in the outer half, an n-doped layer 326 in which the conductivity type opposite to the conductivity type of the semiconductor block 324, that is, n-type ions are implanted and diffused. Are formed. Insulating layer 346 covering upper surface of pressure receiving mesa step 342
Immediately below, inside the n-doped layer 326, an n-doped layer 330 in which the conductivity type opposite to the conductivity type of the semiconductor block 324, that is, n-type ions are implanted and diffused, is formed.
The n-doped layer 326 and the n-doped layer 330 are separated,
A p-type silicon single crystal 324 p layer is interposed between the two. As a result, on the top surface of the pressure receiving mesa step 342,
From inside, n-doped layer 330, p-layer 324, n-doped layer 3
26 are formed. The insulating layer 34 for the p layer 324
Gates 328 are formed at positions facing each other across the gate 6. As a result, a field-effect transistor is formed laterally on the top surface of the pressure receiving mesa step 342.

The inner n-doped layer 330, which functions as a source region, is shorted to the semiconductor block 324 at the source / base contact region 348, and the semiconductor block 324
Is connected to the source electrode 336 via a contact hole formed in the insulating layer 346. Gate 32 facing central p-layer 324 functioning as body region
8 is connected to the gate electrode 334 via a contact hole formed in the insulating layer 346. The outer n-doped layer 326 functioning as a drain region is connected to the drain electrode 332 via a contact hole formed in the insulating layer 346. The source electrode 336, the gate electrode 334, and the drain electrode 332 are insulated.

As understood from the above, the n-doped layer 330 (functioning as a source region), the p-layer 324 (functioning as a body region), and the n-doped layer 326 ( P functioning as a body region
A horizontal field-effect transistor is formed by disposing the gate 328 at a position facing the layer 324 with the insulating layer 346 interposed therebetween. Source region 330 is at source electrode 336, and gate 328 is at gate electrode 334.
Next, it is understood that a semiconductor device in which the drain region 326 is connected to the drain electrode 332 is formed. In the case of a field effect transistor, it is known that when stress is applied to the body region 344 facing the gate 328, the drain current changes even when the gate voltage is constant. By utilizing this characteristic, the pressure receiving mesa step 342 can be used.
The magnitude of the stress acting on the power transmission block 32
2 can be detected.

[0045]

According to the force detection sensor shown in FIGS. 2 to 12, the direction of the force and the current path having the piezoresistive effect can be arranged in parallel. For this reason, the piezoresistance effect appears remarkably, and the resistance value measured along the current path changes greatly. By using a force transmission block with a large area and a mesa step with a small cross-sectional area, the characteristic that the piezoresistance effect appears remarkably can be synergized with the force detection sensor that obtains the force amplification phenomenon. High sensitivity that could not be obtained can be obtained.

In the force detecting sensors shown in FIGS. 11 to 18 according to the embodiment, at least one pn junction surface is formed in the mesa step. For this reason, the sensitivity of the semiconductor device is added to a force detection sensor of a type that obtains a force amplification phenomenon by using a force transmission block having a large area and a mesa step having a small cross-sectional area. A detection sensor is realized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a conventional force detection sensor.

FIG. 2 is a perspective view showing a force detection sensor according to the first embodiment.

FIG. 3 is a cross-sectional view and a plan view of the force detection sensor according to the first embodiment.

FIG. 4 is a cross-sectional view and a plan view of a force detection sensor according to a first modification of the first embodiment.

FIG. 5 is a cross-sectional view and a plan view of a force detection sensor according to a second modification of the first embodiment.

FIG. 6 is a perspective view, a sectional view, and a plan view of a force detection sensor according to a third modification of the first embodiment.

FIG. 7 is a plan view of a force detection sensor according to a fourth modification of the first embodiment.

FIG. 8 is a perspective view of a force detection sensor according to a fifth modification of the first embodiment.

FIG. 9 shows a bridge circuit formed by a force detection sensor according to a fifth modification of the first embodiment.

FIG. 10 is a side view of a force detection sensor according to a sixth modification of the first embodiment.

FIG. 11 is a sectional view and a plan view of a force detection sensor according to a second embodiment.

FIG. 12 shows a relationship between a forward voltage and a forward current of the force detection sensor according to the second embodiment.

FIG. 13 is a cross-sectional view and a plan view of a force detection sensor according to a first modification of the second embodiment.

FIG. 14 is a cross-sectional view and a plan view of a force detection sensor according to a second modification of the second embodiment.

FIG. 15 is a sectional view and a plan view of a force detection sensor according to a third modification of the second embodiment.

FIG. 16 is a cross-sectional view and a plan view of a force detection sensor according to a third embodiment.

FIG. 17 is a cross-sectional view and a plan view of a force detection sensor according to a first modification of the third embodiment.

FIG. 18 is a cross-sectional view and a plan view of a force detection sensor according to a fourth embodiment.

[Explanation of symbols]

 22: Force transmission block 24: Semiconductor block 26: Support base 28: Electrode 36: Mesa step 38: Doped layer: Current path 40: Electrode 42: Insulating layer A: Doped layer (current path) parallel to the mesa step side 132: Mesa step 134: p-doped layer 124: n-type semiconductor block 128: p-electrode 140: n-electrode 236: mesa step 238: n-doped layer (emitter region) 240: p-doped layer (base region) 224: n-type semiconductor block ( (Collector region) 228: emitter electrode 230: collector electrode 232: collector electrode 342: mesa step 330: n-doped layer (source region) 324: p-layer (body region) 326: n-doped layer (drain region) 328: gate 336: Source electrode 332: Drain electrode 334: Drain electrode

Continuing from the front page (72) Inventor Tokuo Fujitsuka 41-cho, Chuchu-Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside the Toyota Central R & D Laboratories Co., Ltd. No. 1 Inside Toyota Central Research Laboratory Co., Ltd. (72) Inventor Hiroshi Tadano 41-cho, Yokomichi, Oku-cho, Nagakute-cho, Aichi-gun, Aichi F-term (reference) 2F055 AA40 BB20 CC60 DD05 EE23 FF02 FF11 GG01 4M112 CA51 EA03

Claims (3)

[The claims] 1. A semiconductor block having a mesa step formed on a surface thereof, and a force transmission block fixed to the top of the mesa step, and an ion of a conductivity type opposite to the conductivity type of the semiconductor block is provided on a side surface of the mesa step. Wherein a side surface of the mesa step is selected in a crystal direction having a piezoresistance coefficient. 2. A semiconductor device comprising: a semiconductor block having a mesa step formed on a surface thereof; and a force transmission block fixed to a top of the mesa step, wherein at least one pn junction surface is formed in the mesa step. High sensitivity force detection sensor. 3. The high-sensitivity force detection sensor according to claim 2, wherein a diode, a bipolar transistor, or a field-effect transistor is formed in the mesa step.