JP2006058266A - Force detector and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make joining strength between a force transmission block and a semiconductor substrate firm, without worsening detection sensitivity. <P>SOLUTION: This force detector is provided with the semiconductor substrate 22 and the force transmission block 32. A dope area 25 of which the resistance varies when a partial region is deflected is formed in the partial region of a surface in the semiconductor substrate 22. The force transmission block 32 contacts with the surface of the semiconductor substrate 22 in the dope region 25 and a surrounding region 34 surrounding the dope region 25. The force transmission block 32 is not projected from an outer circumferential outline 33 of the surrounding area 34. A height of the force transmission block 32 in a direction orthogonal to the surface of the semiconductor substrate 22 is regulated to get high in the doping area 25 and to get low in the surrounding area 34. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a force detection device that outputs an electrical signal corresponding to the magnitude of an acting force (for example, a force acting due to external force, pressure, acceleration, angular velocity, etc.).

Formed on the surface of a semiconductor substrate (typically a silicon single crystal) is a mesa step extending in the crystal direction in which a piezoresistance effect appears, and a force transmission block (typically touching the top surface of the mesa step) Is known a force detection device in which crystallized glass is used. In this type of force detection device, a gap is formed between the surface of the semiconductor substrate and the force transmission block by the protruding mesa step. When the gap is formed, foreign matter generated during the manufacturing process (typically dust, mainly generated during the dicing process) enters the gap, and the foreign matter that enters the gap acts on the force transmission block. There is a possibility that the relationship established between the size of the force and the contact pressure between the force transmission block and the mesa step is shifted from the desired relationship. If the relationship between the magnitude of the load acting on the force transmission block and the magnitude of the contact pressure acting on the mesa step deviates from the desired relationship, the electrical signal obtained from the force sensing device and the magnitude of the force acting on the force sensing device This relationship deviates from the desired one. A force detection device that solves this problem is disclosed in Patent Document 1.
JP 2004-132911 A

FIG. 11 and FIG. 12 show an example of a force detection device in which foreign matter countermeasures are taken. As shown in FIGS. 11 and 12, the force transmission block 1032 is shown by a two-dot broken line for the sake of clarity. 12 corresponds to the D, E, and F lines in FIG.
As shown in FIGS. 11 and 12, the force detection device 1010 includes an n-type semiconductor substrate 1022 and a force transmission block 1032. A mesa step 1024 formed by mesa etching is formed on the surface of the semiconductor substrate 1022. A direction in which the piezoresistance effect appears is selected as the longitudinal direction of the mesa step 1024. The surface of the semiconductor substrate 1022 is covered with an insulating layer 1028 to ensure insulation (not shown in FIG. 11).
The top surface portion of the mesa step 1024 is doped with a p-type impurity having a conductivity type opposite to that of the semiconductor substrate 1022, thereby forming a piezo region 1025. The piezo region 1025 is indicated by black hatching. As shown in FIG. 12E, both ends of the piezo region 1025 are electrically connected to a pair of electrodes 1042 and 1044 through contact holes 1042a and 1044a. Thus, the pair of electrodes 1042 and 1044 are electrically connected via the piezoelectric region 1025 formed on the top surface portion of the mesa step 1024.
The force transmission block 1032 is in contact with the surface of the semiconductor substrate 1022 in the piezo region 1025 on the surface of the mesa step 1024 and the surrounding region 1034 surrounding the mesa region 1025. The force transmission block 1032 is fixed to the surface of the semiconductor substrate 1022 by the surrounding area 1034. The shape of the force transmission block 1032 is a rectangular parallelepiped.
When a load acts on the surface opposite to the surface facing the semiconductor substrate 1022 of the force transmission block 1032 (the surface on the upper side of the paper), the force transmission block 1032 has a piezoelectric region 1025 and a mesa step 1024 according to the magnitude of the load. Compressive stress is transmitted to The mesa step 1024 is distorted based on the magnitude of the compressive stress. Due to this distortion, the resistance value of the piezo region 1025 of the mesa step 1024 changes. The amount of change is proportional to the magnitude of the load. When a constant current is passed, the voltage applied to the force transmission block 1032 can be detected because the voltage between the pair of electrodes 1042 and 1044 changes when the resistance changes.

  The feature of the force detection device 1010 is that the force transmission block 1032 is joined to the surface of the semiconductor substrate 1022 at the periphery thereof. In other words, the force transmission block 1032 is more than the outer peripheral contour 1033 of the surrounding region 1034. Is not protruding to the outside. For this reason, no gap is formed between the force transmission block 1032 and the semiconductor substrate 1022 outside the surrounding region 1034. Therefore, a situation where foreign matter accumulates in the gap does not occur. As shown in Patent Document 1 by the present applicant, a mesa-shaped sealing member that makes a circuit along the surface of the force transmission block and the semiconductor substrate may be provided. Also in this case, it is possible to realize a structure in which no gap is formed outside the outer peripheral contour of the surrounding region where the sealing member and the force transmission block are joined. In addition, when the force transmission block protrudes outside the outer peripheral contour, for example, in a tapered shape, or protrudes with a curvature, the gap between the force transmission block and the semiconductor substrate is formed wide, so that the foreign matter The accumulation of is substantially prevented. Also in this case, it can be evaluated as a force detection device in which measures against foreign matter are taken.

The applicant has succeeded in obtaining new knowledge after conducting detailed research on this type of force detection device proposed by the present applicant. It is a structure in which this kind of force detection device breaks the trade-off relationship that exists between the sensitivity of detecting the load acting on the force transmission block and the bonding strength between the force transmission block and the semiconductor substrate. This is the fact. Next, this will be specifically described.
As shown in FIG. 12F, in order to increase the bonding strength between the force transmission block 1032 and the semiconductor substrate 1022 and improve the mechanical stability of the force detection device, the area of the surrounding region 1034 needs to be increased. There is. On the other hand, in order to improve the detection sensitivity of this type of force detection device, in general, the area of the contact surface between the force transmission block 1032 and the semiconductor substrate 1022 (both the surrounding region 1034 and the piezo region 1025) must be reduced. It is supposed to be. As described above, when the area of the surrounding region 1034 is reduced, the bonding strength between the force transmission block 1032 and the semiconductor substrate 1022 is weakened, and it is difficult to ensure the mechanical stability of the force detection device 1010. That is, in this type of force detection device 1010, it was considered that there is a trade-off relationship between detection sensitivity and bonding strength.
However, when the force detection device proposed by the applicant is studied in detail, the width L1011 of the piezo region 1025 is increased and the area of the surface where the force transmission block 1032 and the semiconductor substrate 1022 are in contact is increased. Although the detection sensitivity is greatly deteriorated, the phenomenon has been found that when the width L1012 of the surrounding region 1034 is increased and the area thereof is increased, the detection sensitivity does not deteriorate so much. More specifically, it has been found that even if the area of the go region 1034 is doubled, the detection sensitivity only deteriorates by about 10%. That is, it has been found that the force transmission block 1032 in which foreign matter countermeasures are taken has a structure in which an applied load is easily transmitted to the mesa step 1024 in a concentrated manner. From this, it has been found that this type of force detection device has a structure in which it is easy to secure a wide surrounding area and ensure the mechanical stability of the force detection device without significantly degrading the detection sensitivity. It was. This type of force detection device is considered to have extremely unique properties.
The present invention makes use of the properties of this type of force detection device to further increase the detection sensitivity without losing the bonding strength, or conversely, further improving the bonding strength without losing the detection sensitivity, Furthermore, it was developed for the purpose of improving both joint strength and detection sensitivity as needed.

The force detection device of the present invention includes a semiconductor substrate and a force transmission block. A piezo region whose resistance changes when the region is distorted is formed in a partial region of the surface of the semiconductor substrate. The force transmission block is in contact with the semiconductor substrate surface in the piezoelectric region and the surrounding region surrounding the piezoelectric region, and accumulates foreign matter between the semiconductor substrate surface and the force transmission block outside the outer peripheral contour of the surrounding region. There is no gap. The height of the force transmission block in the direction orthogonal to the surface of the semiconductor substrate is adjusted to be high in the piezo region and low in at least a part of the surrounding region.
The force transmission block and the semiconductor substrate may be in direct contact with each other, or may be in indirect contact with another member interposed therebetween. When other members are interposed, the other members can be evaluated as a part of the semiconductor substrate. Alternatively, it may be appropriate to evaluate as part of a force transmission block.
When the gap between the force transmission block and the semiconductor substrate is sufficiently wide outside the outer peripheral contour of the surrounding area, foreign matter is not substantially accumulated. The gap in which foreign matter accumulates here refers to a gap in which foreign matter is accumulated so as to prevent displacement of the force transmission block when a load is applied to the force transmission block. A case where the detection result of the force detection device is not stable depending on the presence or absence of foreign matter. As long as such a situation does not occur, the aspect in which the force transmission block protrudes outside the outer peripheral contour of the surrounding region should be interpreted as the force transmission block of the present invention. Typically, when protruding with a taper or curvature, it should be interpreted as a force transmission block of the present invention.

Said force detection apparatus is a force detection apparatus with which the foreign material countermeasure was taken. In this type of force detection device, even if the area of the surrounding region where the force transmission block and the semiconductor substrate are in contact with each other is increased, the detection sensitivity does not deteriorate so much. Therefore, this type of force detection device can employ a configuration in which the area of the surrounding region is increased and the bonding strength is increased. Further, in the force detection device, the height of the force transmission block in the direction orthogonal to the surface of the semiconductor substrate is adjusted to be high in the piezo region and low in at least a part of the surrounding region. For this reason, the force acting on the force transmission block is more easily concentrated on the piezo region than on the surrounding region. As a result, this force detection device can detect a load acting on the force transmission block with high sensitivity because more compressive stress is transmitted to the piezo region. Therefore, this force detection device can strengthen the bonding strength, and does not deteriorate the detection sensitivity, or can increase the sensitivity as necessary. Alternatively, the bonding strength can be made equal to the conventional one, and the detection sensitivity can be increased.
Note that the above-described force detection device can be grasped as follows from another viewpoint. The force detection device in which measures against foreign matter are taken can increase the area of the surrounding area. If the surrounding area is configured to be wide, the force transmission block corresponding to the surrounding area may be configured to be wide. For such a force transmission block, the load acting on the force transmission block is concentrated and transmitted to the piezo region by adopting the configuration of the present invention that lowers the height of the force transmission block in the surrounding region. Can be effectively obtained. That is, it can be said that the configuration of the force transmission block of the present invention functions extremely effectively in a force detection device in which measures against foreign matter are taken.

It is preferable that a gap is secured between the semiconductor substrate and the force transmission block in at least a part of the region between the piezo region and the surrounding region.
When the gap is secured, the contact area between the piezo region and the force transmission block becomes relatively large. For this reason, the load acting on the force transmission block can be concentrated and transmitted to the piezo region, and the detection sensitivity can be increased.

It is preferable that a recess is formed on the surface of the semiconductor substrate in at least a part of the region between the piezo region and the surrounding region.
According to the above aspect, the recess is surrounded by the force transmission block, and a gap can be secured between the semiconductor substrate and the force transmission block. As a result, the contact area between the piezo region and the force transmission block is relatively increased. Can be bigger. This force transmission block can transmit the acting load in a concentrated manner in the piezo region, and the detection sensitivity can be increased.

It is preferable that a recess is formed on the back surface of the force transmission block in at least a part of the region between the piezo region and the surrounding region.
Similarly, in this case, the recess is surrounded by the semiconductor substrate, so that a gap can be secured between the semiconductor substrate and the force transmission block, so that the contact area between the piezo region and the force transmission block is relatively increased. Can be bigger. This force transmission block can transmit the acting load in a concentrated manner in the piezo region, and the detection sensitivity can be increased.

In the force transmission block, it is preferable that a step is formed in a region between the piezo region and the surrounding region which is high on the piezo region side and low on the surrounding region side.
According to the above aspect, a force transmission block is obtained in which the height in the direction orthogonal to the surface of the semiconductor substrate is adjusted to be high in the piezo region and low in the surrounding region. The force transmission block can transmit the acting load in a concentrated manner in the piezo region, and can increase the detection sensitivity of the force detection device.

It is preferable that the side wall of the force transmission block extends in a direction perpendicular to the semiconductor substrate surface from the outer peripheral contour of the surrounding region. In other words, the force transmission block does not protrude at all toward the outside of the outer peripheral contour of the surrounding area. Therefore, no gap is formed between the force transmission block and the semiconductor substrate surface outside the outer peripheral contour of the surrounding region.
Since the force transmission block of the above aspect does not have a portion protruding to the outside, the phenomenon that the protruding portion hangs down due to the load applied and the piezo region side is warped does not occur. Thereby, the acting load can be more concentrated and transmitted to the piezo region. Therefore, it is possible to obtain a force detection device with higher detection sensitivity.

The present applicant has also created a new manufacturing method capable of easily manufacturing the above-described force detection device.
The method for manufacturing a force detection device according to the present invention includes a step of forming a plurality of unit element structures in a lattice shape on a surface of a semiconductor substrate, each of which includes a piezo region having a piezoresistive effect and an electrode conducting to the piezo region. It has. Further, the method includes a step of preparing a plate material in which lattice-like grooves passing through the gaps between the unit element structures are formed on the back surface side. After passing through said process, it has the process of joining the back surface of the board | plate material to the surface of a semiconductor substrate. And it has a depth that reaches the groove on the back surface side from the surface side of the plate material along the lattice line on the surface side corresponding to the lattice groove on the back surface side of the plate material, and is wider than the groove on the back surface side. A step of forming a grid-like groove having a width is provided.
If each said process is implemented, the board | plate material on each unit element structure will be obtained as a shape where the circumference height became low. The force transmission block according to the present invention can be easily obtained. The force detection device of the present invention can be easily manufactured.

  The force detection device of the present invention can further increase the detection sensitivity without deteriorating the bonding strength, or conversely, further improve the bonding strength without deteriorating the detection sensitivity, and further, if necessary, the bonding strength. It is possible to improve both the detection sensitivity and the detection sensitivity.

First, the main features of the embodiment are listed.
(First Form) The piezo region forms a current path that is electrically insulated from the surrounding semiconductor substrate.
(Second Mode) The piezo region of the first mode is formed on the surface of the semiconductor substrate and is formed by doping a mesa step extending in a direction in which the piezoresistive effect appears with an impurity having a conductivity type opposite to that of the semiconductor substrate. Area.
(Third Embodiment) The piezoelectric region of the first embodiment is a region formed by doping a part of the surface of a flat semiconductor substrate with an impurity having a conductivity type opposite to that of the semiconductor substrate.
(4th form) The piezoelectric area | region of a 1st form may be an area | region which forms an electric current path in the inside separated by the insulating material from the surrounding semiconductor substrate.
(Fifth Mode) The force transmission block has a stepped shape in which the height of the portion corresponding to the surrounding region with the semiconductor substrate is low.
(6th form) The level | step difference of 5th form makes a round of the force transmission block.
(7th form) The force transmission block side wall is processed into the taper shape which spreads toward the semiconductor substrate side.

Embodiments will be described in detail below with reference to the drawings.
First Embodiment FIGS. 1 and 2 show a force detection device according to a first embodiment. As shown in FIGS. 1 and 2, the force transmission block 32 is shown by a two-dot broken line for the sake of clarity. 2 corresponds to the lines A, B, and C in FIG.
As shown in FIGS. 1 and 2, the force detection device 10 includes a semiconductor substrate 22 mainly composed of an n-type silicon single crystal having a crystal plane (110) plane, and a force transmission block 32. A mesa step 24 is formed on the surface of the semiconductor substrate 22 by mesa etching. The mesa step 24 is formed as the remaining portion of the recess 26 formed in the semiconductor substrate 22. The mesa step 24 extends substantially across the center of the recess 26. A direction in which the piezoresistance effect appears is selected as the longitudinal direction of the mesa step 24. In this example, the longitudinal direction of the mesa step 24 matches the crystal direction <110>. This recess 26 is sealed by a force transmission block 32 to form a closed gap 26 (detailed later).
The surface of the semiconductor substrate 22 is covered with an insulating layer 28 in order to ensure insulation (not shown in FIG. 1). The top surface portion of the mesa step 24 is doped with a p-type impurity having a conductivity type opposite to that of the semiconductor substrate 22 to form a piezo region 25. This piezo region 25 is illustrated by black hatching. As shown in FIG. 2B, both ends of the piezo region 25 are electrically connected to a pair of electrodes 42 and 44 through contact holes 42a and 44a. Thus, the pair of electrodes 42 and 44 are electrically connected via the piezoelectric region 25 formed on the top surface portion of the mesa step 24.

On the semiconductor substrate 22 of the force detection device 10, a force transmission block 32 having crystallized glass as a main component is fixed. The force transmission block 32 is in contact with the surface of the semiconductor substrate 22 in the piezoelectric region 25 of the mesa step 24 and the surrounding region 34 surrounding the mesa step 24. The surrounding area 34 circulates around the gap 26 around the mesa step 24. The width of the surrounding area 34 is constant. The force transmission block 32 is fixed on the semiconductor substrate 22 by the surrounding region 34.
The force transmission block 32 does not protrude outward from the outer peripheral contour 33 of the surrounding area 34. The side wall of the force transmission block 32 extends from the outer peripheral contour 33 of the surrounding region 34 in a direction orthogonal to the surface of the semiconductor substrate 22. Therefore, no gap is formed between the force transmission block 32 and the surface of the semiconductor substrate 22 outside the outer peripheral contour 33 of the surrounding region 34. Foreign matter measures are taken.
From another point of view, the force transmission block 32 can be expressed as follows. The width of the force transmission block 32 parallel to the semiconductor substrate 22 can also be expressed as being within a range not exceeding the outer peripheral contour 33 of the surrounding region 34 with the semiconductor substrate 22 as shown in FIGS. .
Further, the force transmission block 32 is formed with a step which is high on the piezoelectric region 25 side and low on the surrounding region 34 side. As shown in FIGS. 1 and 2, the height of the force transmission block 32 in the direction orthogonal to the surface of the semiconductor substrate 22 is lower than the remaining height H12 in a portion corresponding to the surrounding region 34. More specifically, the portion of the height H12 is formed around the force transmission block 32, and the width 38 of this region substantially coincides with the width of the surrounding region 34. The height H12 is adjusted to be lower than the height H11 of the portion corresponding to the piezo region 25 of the mesa step 24.
A hemisphere (not shown) is fixed to the surface of the force transmission block 32 opposite to the surface facing the semiconductor substrate 22 (the upper surface of the paper; hereinafter referred to as the upper surface).

When a load acts on a hemisphere (not shown), the hemisphere applies the load evenly to the upper surface of the force transmission block 32. The force transmission block 32 transmits a compressive stress to the mesa step 24 via the contact region 36 according to the magnitude of the load. Since the force transmission block 32 of this embodiment is adjusted to be high on the piezo region 25 side and low on the surrounding region 34 side, the load acting on the force transmission block 32 is concentrated and transmitted to the mesa step 24 as compressive stress. Is done. The mesa step 24 is distorted by the compressive stress, and the amount of strain is based on the magnitude of the compressive stress. Since more compressive stress is transmitted, the mesa step 24 is greatly distorted (compared to the case where the force transmission block is a rectangular parallelepiped). The amount of change in the resistance value of the mesa step 24 based on the amount of strain is detected as the amount of change in the voltage value between the pair of electrodes 42 and 44 when a constant current is passed. Since the amount of distortion of the mesa step 24 is large, the amount of change in voltage value also increases. Thereby, the force acting on the force transmission block 32 can be detected with high sensitivity.
As shown in FIG. 2, the detection sensitivity can be adjusted by adjusting the width 38 of the portion where the height of the force transmission block 32 is low. Increasing the width 38 further improves the detection sensitivity.
In order to increase the bonding strength between the force transmission block 32 and the semiconductor substrate 22, it is preferable to configure the surrounding region 34 to be wide. The wider the surrounding area 34 is, the more easily the detection sensitivity is deteriorated (of course, the present embodiment in which foreign matter countermeasures are taken does not worsen compared to the case where foreign matter measures are not taken). In the present embodiment in which the periphery of the transmission block 32 is configured to be low, deterioration in detection sensitivity is suppressed. In some cases, even if the surrounding region 34 is configured to be wide, the detection sensitivity can be increased. Therefore, it is possible to obtain the force detection device 10 without deteriorating the detection sensitivity or increasing the detection sensitivity and having a strong bonding strength.
Moreover, even if the joint area of the surrounding area 34 is equivalent to the conventional one, the detection sensitivity can be increased by using the step-shaped force transmission block 32. The detection sensitivity can be increased without impairing the bonding strength.

Note that the force detection device 10 with the foreign matter countermeasure of the present embodiment can concentrate and transmit the compressive stress to the mesa step 24 for the following reason regardless of the force transmission block 32. it is conceivable that.
For example, when the force transmission block protrudes outside the surrounding area (when no foreign matter countermeasures are taken), the force transmission block is based on the weight of the protruding portion and the applied load. It is thought that the center side is warped by sagging. Thereby, it is thought that it is a structure where a load is hard to be transmitted to the center side.
On the other hand, the force transmission block 32 of the present embodiment is not formed to protrude outward from the outer peripheral contour 33. An outer peripheral contour 33 of the force transmission block 32 is bonded to the surface of the semiconductor substrate 22. Thereby, it is considered that the force transmission block 32 of the present embodiment has a structure in which the acting force is easily concentrated on the center side. Therefore, it can be considered that the force transmission block 32 of this embodiment can obtain a phenomenon that does not deteriorate the detection sensitivity so much even if the area of the surrounding region 34 is increased.

Next, with reference to FIG. 3, the manufacturing method of this force detection apparatus 10 is demonstrated.
First, as shown in FIG. 3A, a semiconductor wafer 22 having n-type single crystal silicon as a main component is prepared. The surface of the semiconductor wafer 22 is etched to form a recess (rear closed space 26). The remainder of the recess is a mesa step not shown. A p-type impurity is implanted into the top surface portion of the mesa step to form a piezoelectric region (not shown). Next, after oxidizing the surface of the semiconductor substrate 22 and covering it with the insulating layer 28, contact holes (not shown) are formed, and electrodes 42 and 44 covering the contact holes are formed. A plurality of the unit element structures are formed in a lattice shape on the semiconductor wafer 22.

Next, as shown in FIG. 3B, a glass wafer 32a (which will later become the force transmission block 32) containing crystallized glass as a main component is prepared. The glass wafer 32 a is grooved in a lattice shape, and the surface subjected to the grooving is bonded to the surface of the semiconductor substrate 22. This groove coincides with the position of the gap between the unit element structures. The glass wafer 32a and the semiconductor substrate 22 are fixed by, for example, anodic bonding.
In this embodiment, even if the areas of the force transmission block 32 and the surrounding region 34 of the semiconductor substrate 22 are increased, the detection sensitivity does not deteriorate so much. Therefore, the surrounding region 34 can be formed wide. This also means that, in the process of bonding the glass wafer 32a and the semiconductor substrate 22, the width allowing the positional deviation between the two becomes wide. Therefore, the structure of the force detection device 10 according to the present embodiment has a feature that it is easy to make from the viewpoint of manufacturing.

Next, as shown in FIG. 3 (c), the dicing saw 92 is moved up and down a plurality of times (in this example, four times or even once) to correspond to the grooved portion of the glass wafer 32a. To remove. At this time, it reaches the grooved groove and cuts and removes a wider range than the groove. By this step, the shape of the remaining glass wafer 32a becomes a step shape in which the height of the periphery thereof is lower than the mesa step side, and the force transmission block 32 having a desired shape can be obtained.
As described above, in this embodiment, the surrounding region 34 is formed wide. Therefore, the step of forming a step on the glass wafer 32a by the dicing saw 92 can be easily performed without requiring accurate control. The step-like force transmission block 32 can be easily obtained.

Next, as shown in FIG. 3D, in order to protect the electrodes 42 and 44 and the like, the surface of the semiconductor substrate 22 is completely covered with a protective film 82 whose main component is a resin or the like.
Next, as shown in FIG. 3 (e), a dicing saw 94 is used to cut out along each force detection device.
Through the above steps, the force detection device of this embodiment can be obtained.
Note that the formation of the protective film 82 shown in FIG. 3D is not necessarily required and can be omitted.

Next, the modification of the force transmission block of a present Example is shown in FIGS. The cross-sectional views of these modifications are shown corresponding to the cross section of the first embodiment in the direction of FIG. 2 (c).
The force transmission block 132 in FIG. 4 has a trapezoidal cross section. The side wall is processed into a taper shape spreading toward the surface of the semiconductor substrate 122. The force transmission block 132 has a height H112 in the surrounding area 134 (which varies within the width of the surrounding area 134, but any height may be selected) than the height H111 in the piezo area 125 of the mesa step 124. It is adjusted low. Also in this modified example, since the load acting on the upper side surface of the force transmission block 132 is concentrated and transmitted to the mesa step 124, the acting load can be detected with high sensitivity.

The force transmission block 232 of FIG. 5 is an example in which a recess 226 is formed on the side of the force transmission block 232, and a closed gap 226 is formed between the force transmission block 232 and the semiconductor substrate 222 by the recess 226. is there. The surface of the semiconductor substrate 222 in this example is not etched. Therefore, no mesa step is formed on the surface of the semiconductor substrate 222, and the piezo region 225 is formed on the surface portion of the flat semiconductor substrate 222 so as to extend in the direction between a pair of electrodes (not shown). The direction in which the piezoresistance effect appears is selected as the longitudinal direction of the piezo region 225. On the other hand, a mesa step that crosses the closed gap 226 is formed on the force transmission block 232 side. The mesa level difference on the side of the force transmission block 232 coincides with the position of the piezoelectric region 225 on the surface of the semiconductor substrate 222, and the force transmission block 232 and the piezoelectric region 225 are in contact with each other.
In the force transmission block 232, the height H212 in the surrounding area 234 is adjusted to be lower than the height H211 in the piezo area 225. Accordingly, since the load acting on the upper side surface of the force transmission block 232 is concentrated and transmitted to the piezo region 225, the acting load can be detected with high sensitivity.

The force transmission block 332 of FIG. 6 can be evaluated as one modification of FIG. The force transmission block 332 is processed into a taper shape that spreads in the opposite direction toward the surface (both the surrounding region 334 and the piezoelectric region 325) that is bonded to the semiconductor substrate 322. In this example, the force transmission block 332 is formed to protrude outward from the outer peripheral contour 333 of the surrounding region 334. A tapered surface 331 on the outer peripheral contour 333 side protrudes outward from the outer peripheral contour 333. However, the gap between the tapered surface 331 and the surface of the semiconductor substrate 322 is sufficiently wide, and foreign matter (for example, dust etc.) hardly accumulates in the gap. Further, when protruding in a tapered shape as in this embodiment, the same effect as the phenomenon detailed in [0015] can be obtained. That is, when protruding in a tapered shape, the phenomenon that the load is difficult to transmit to the center side due to the weight of the protruding portion does not occur, and it is easy to concentrate on the center side. It is a structure that can obtain various phenomena. The angle between the tapered surface 331 and the surface of the semiconductor substrate 322 is 45 ° or more, which is preferable because the force transmission block 332 can surely obtain the above effect.
In the force transmission block 332 of the force detection device in FIG. 6, the height H312 in the surrounding region 334 is adjusted to be lower than the height H311 in the piezo region 325. Therefore, since the load acting on the force transmission block 332 is transmitted in a concentrated manner by the piezo region 325, the acting load can be detected with high sensitivity.

The force transmission block 432 in FIG. 7 is an example in which metal members 452 and 454 mainly composed of titanium (Ti) or titanium nitride (TiN) are interposed between the force transmission block 432 and the semiconductor substrate 422, for example. is there. The material of the metal members 452 and 454 may be silicon oxide or silicon nitride instead of the metal. This metal member 452 can be evaluated as a part of the semiconductor substrate 422. Therefore, the surface where the force transmission block 432 and the semiconductor substrate 422 are in contact may be evaluated as the surface where the force transmission block 432 and the metal member 452 are in contact.
As shown in FIG. 7, the force transmission block 432 is adjusted such that the height H412 in the surrounding region 434 is lower than the height H411 in the piezo region 425. Thereby, since the load acting on the force transmission block 432 is concentrated and transmitted to the piezo region 425, the acting load can be detected with high sensitivity.

Next, some examples using a force transmission block formed with a step-like shape anisotropy are shown in FIGS. These embodiments are examples in which the shape of the mesa step is different from that of the first embodiment.
Second Embodiment FIG. 8 is a plan view of a force detection device 510 according to a second embodiment. The shape of the force transmission block 532 is a stepped shape as in the first embodiment. In FIG. 8, it is indicated by a two-dot broken line for the sake of clarity.
The mesa step 524 of this embodiment is formed by mesa etching the surface of the n-type semiconductor substrate 522 having a crystal plane (110) plane. This mesa step 524 is formed as the remainder of the etched recess 526. A p-type impurity having a conductivity type opposite to that of the semiconductor substrate 522 is introduced into the top surface portion of the mesa step 524 to form a piezo region 525. The piezo region 525 is illustrated by black hatching. The mesa step 524 extends in the direction of the pair of electrodes 542 and 544 and is formed in a circular shape that goes around the center of the gap 526. For this reason, the mesa step 524 facing the center of the circle is substantially parallel, and therefore the crystal direction of the facing mesa step 524 is also parallel. Therefore, it can be evaluated that the equivalent circuit between the pair of electrodes 542 and 544 is configured in parallel with a variable variable by the piezoresistive effect. The structure of the circular mesa step 524 is a combination of a <110> direction component that is highly sensitive to a compressive load and an insensitive (or small) <100> direction component. Therefore, although the sensitivity is reduced, the amount of change can be stably detected because the amount of change of the two variable resistors is used. Therefore, the proportional relationship between the magnitude of the load acting on the force transmission block 532 and the amount of change in resistance value is extremely linear. A force transmission device that accurately detects the load acting on the force transmission block 532 can be obtained.

  Further, the force transmission block 532 used in this embodiment is not formed to protrude outward from the outer peripheral contour 533 of the surrounding region 534. Further, the force transmission block 532 is adjusted such that the height in the surrounding region 534 is lower than the height in the piezo region 525 of the circular mesa step 524. Therefore, also in this embodiment, the load acting on the upper surface of the force transmission block 532 is concentrated and transmitted to the piezo region 525 of the circular mesa step 524, so that the acting load can be detected with high sensitivity. Can do. The load acting on the force transmission block 532 can be detected accurately and with high sensitivity.

Third Embodiment FIG. 9 is a perspective view of a force detection device 610 according to a third embodiment. In this embodiment, the Wheatstone bridge is configured by the mesa steps 624a, 624b, 624c, and 624d. Further, the shape of the force transmission block 632 has a stepped shape as in the first embodiment.
The mesa steps 624a, 624b, 624c, and 624d in this embodiment are formed by mesa etching the surface of the n-type semiconductor substrate 622 on the crystal plane (110). These mesa steps 624a, 624b, 624c, 624d are formed as the remainder of the etched recess 626. A p-type impurity having a conductivity type opposite to that of the semiconductor substrate 622 is introduced into the top surface portions of the mesa steps 624a, 624b, 624c, and 624d to form a piezoelectric region 625. The longitudinal directions of opposing mesa steps (624a and 624b, 624c and 624d) extend in parallel. The longitudinal direction of the mesa steps 624a and 624b is orthogonal to the longitudinal direction of the mesa steps 624c and 624d, and the crystal directions are the <110> direction and the <100> direction. Accordingly, the mesa steps 624a, 624b, 624c, and 624d form a Wheatstone bridge made of a regular square. Electrodes 642, 644, 646, and 648 are connected to the respective corners of the regular square.
A constant current is passed between a pair of diagonal electrodes 642 and 646, and a voltage value is measured between a pair of electrodes 644 and 648 forming the other diagonal. When such mesa steps 624a, 624b, 624c, and 624d formed of Wheatstone bridges are used, the proportional relationship between the magnitude of the load acting on the force transmission block 632 and the amount of change in resistance value is extremely linear. Show. The load acting on the force transmission block 632 can be accurately detected.

Further, the force transmission block 632 used in this embodiment is not formed so as to protrude from the outer peripheral contour 633 of the surrounding region 634. Further, the height of the portion of the force transmission block 632 in the surrounding region 634 is adjusted to be lower than the height in the piezo region 625 of the mesa steps 624a, 624b, 624c, and 624d formed of Wheatstone bridges. Accordingly, also in this embodiment, the load acting on the upper side surface of the force transmission block 632 is concentrated and transmitted to the mesa step 624 constituted by the Wheatstone bridge, so that the acting load is detected with high sensitivity. Can do. The load acting on the force transmission block 632 can be detected accurately and with high sensitivity.
FIG. 10 is a modification of the third embodiment, and is an example in which the Wheatstone bridge is formed in a circular shape. The mesa steps (724a and 724b, 724c and 724d) facing the center of the circle are substantially parallel, so the crystal directions of the facing mesa steps (724a and 724b, 724c and 724d) are each <110. The> direction and the <100> direction are the main components. Therefore, it functions as a Wheatstone bridge and can obtain the same effect as the third embodiment. The load acting on the force transmission block 732 can be detected accurately and with high sensitivity.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

The perspective view of the force detection apparatus of 1st Example is shown. Sectional drawing corresponding to each line | wire of 1st Example is shown. The manufacturing process of the force detection apparatus of 1st Example is shown. Sectional drawing of the modification of 1st Example is shown (1). Sectional drawing of the modification of 1st Example is shown (2). Sectional drawing of the modification of 1st Example is shown (3). Sectional drawing of the modification of 1st Example is shown (4). The top view of the force detection apparatus of 2nd Example is shown. The perspective view of the force detection apparatus of 3rd Example is shown. The top view of the modification of 3rd Example is shown. 1 shows a perspective view of a prior art force sensing device. FIG. Sectional drawing corresponding to each line | wire of a prior art is shown.

Explanation of symbols

22: semiconductor substrate 24: mesa step 25: piezo region 26: gap 32: force transmission block 33: outer periphery contour 34 of the force transmission block: surrounding regions 42, 44: electrodes

Claims (7)

It has a semiconductor substrate and a force transmission block,
A piezo region in which resistance changes when the region is distorted is formed in a partial region of the surface of the semiconductor substrate,
The force transmission block is in contact with the surface of the semiconductor substrate in the piezoelectric region and the surrounding region surrounding the piezoelectric region,
Outside the outer peripheral contour of the surrounding area, there is no gap for accumulating foreign matter between the surface of the semiconductor substrate and the force transmission block,
The height of the force transmission block in the direction orthogonal to the surface of the semiconductor substrate is adjusted to be high in the piezo region and low in at least a part of the surrounding region.   2. The force detection device according to claim 1, wherein a gap is secured between the semiconductor substrate and the force transmission block in at least a part of a region between the piezo region and the surrounding region.   3. The force detection device according to claim 2, wherein a recess is formed in the surface of the semiconductor substrate in at least a part of a region between the piezo region and the surrounding region.   The force detection device according to claim 2, wherein a recess is formed in the back surface of the force transmission block in at least a part of a region between the piezo region and the surrounding region.   5. The force detection device according to claim 1, wherein a step is formed in the force transmission block between the piezo region and the surrounding region so as to be higher on the piezo region side and lower on the surrounding region side. .   6. The force detection device according to claim 1, wherein a side wall of the force transmission block extends in a direction perpendicular to the surface of the semiconductor substrate from an outer peripheral contour of the surrounding region. A step of forming a plurality of unit element structures in a lattice shape on a surface of a semiconductor wafer, the unit element structure including a piezo region having a piezoresistive effect and an electrode conducting to the piezo region;
Preparing a plate material in which a lattice-like groove passing through the gap between the unit element structures is formed on the back surface side;
Bonding the back surface of the plate material to the surface of the semiconductor wafer;
A depth that reaches the groove on the back surface from the surface side of the plate material along the lattice line on the surface side corresponding to the lattice groove on the back surface side of the plate material, and wider than the groove on the back surface side. A method for manufacturing a force detection device comprising a step of forming a lattice-shaped groove.

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