JPS63226074A - Force detector - Google Patents

Abstract

PURPOSE:To facilitate detecting a large load and improve impact-resistant properties even if a detecting element is formed on a single crystal substrate by a method wherein the single crystal substrate is provided and a strain inducing unit in which one of its center part or circumferential part serves as a support and the other serves as an actuator is provided and the single crystal substrate is bonded and fixed to the surface of the strain inducing unit. CONSTITUTION:A strain inducing unit 4 which serves as a reinforcing substrate which reinforces a single crystal substrate 1 is provided. The strain inducing unit 4 has a disc shape and its circumferential part serves as a support 6 with fixing screw holes 5 and a force transmitter 8 is formed at its center part. A circular recess 9 is formed around the force transmitter 8 to provide a thin film elastic deforming surface 10. The above mentioned single crystal substrate 1 is bonded and fixed to the surface of the elastic deforming surface 10. With this constitution, the strain inducing unit 4 is deformed by applying an external force to the force transmitter 8 and an internal stress is created in the single crystal substrate 1 corresponding to the deformation of the strain inducing unit 4. A detecting element 3 is deformed by the strain created as mentioned above and a resistance variation DELTAR is created by a piezo-resistance effect.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a force detection device used, for example, in a force sensor for a robot, a three-dimensional input device as a man-machine interface, and the like.

2. Description of the Related Art A conventional force detection device includes a strain body that elastically deforms when an external force is applied thereto, and a plurality of detection elements that change electrical resistance through mechanical deformation of the strain body. The strength of the external force is detected by extracting the change in electrical resistance as an electrical signal.

A technique for forming a detection element on the surface of a strain body made of silicon single crystal by semiconductor planar process technology is disclosed in Japanese Patent Laid-Open No. 60-221288. That is, a regular octagonal flat ring-shaped strain body made of silicon single crystal is formed, a plurality of detection elements are formed on one side of the strain body, and an external force is applied to opposite sides of the strain body to obtain Fx, This detects the two-dimensional distribution of the three force components Fy and Fz.

However, in order to cut out a hexagonal flat ring-shaped strain body from a silicon single crystal substrate, a combination of dicing saw cutting, laser machining, etching, etc. must be used, which is not easy. have a problem

Further, when the strain body is formed of a silicon single crystal, the physical property of the silicon single crystal is that it is highly brittle, and there is a problem that the maximum value that can be detected by a load is low. Furthermore, there is also the problem of being weak against shock.

Purpose The present invention provides a force detection device that can detect a large load even if the detection element is formed on a single crystal substrate by applying technology such as a semiconductor planar process, and that can improve impact resistance. The purpose is to obtain.

Structure The present invention provides a single-crystal substrate with a detection surface formed over one surface and is equipped with a detection element that changes electrical resistance by mechanical deformation, with one of the center and peripheral portions serving as a support and the other acting as a support. A strain-generating body is provided, and the single crystal substrate is adhesively fixed to the surface of the strain-generating body. Therefore, even if a detection element is formed directly on the surface of a single-crystal substrate using semiconductor planar process technology, an external force will not be generated because a separate strain-generating body is bonded to the single-crystal substrate. This allows the detection of high loads that cannot be detected with a single crystal substrate, and even if an impact force is applied, an excessive force acts on the single crystal substrate. It is designed so that nothing happens.

A first embodiment of the present invention will be described based on FIGS. 1 to 6. First, the single crystal substrate 1 is made of silicon single crystal and has a square shape. One surface of this single crystal substrate 1 is used as a detection surface 2, and a detection element 3 is formed on this detection surface 2 by means described later.

These detection elements 3 utilize the principle that resistivity changes when deformed under stress, that is, the piezoresistance effect. For example, when the single crystal substrate 1 is
1 (110) wafer, Rx, , Rx, , Rx, , Rx, and Ry as shown in FIG.
,.

The detection element 3 of RY, , RYs r RY4 is <1
10> direction, and Rx4.
RZz! RZs +Rz, the detection element 3 is <11
0> direction. The shape of each detection element 3 is shown enlarged in FIG.
The width is set to be Q, the length is set to be Q2, and the width is set to be Q, (Q) so that the current i flows in the direction of the axis and at 45 degrees with these.

Next, a method for manufacturing the detection element 3 will be explained based on FIG. 7. What is shown in FIG. 7 is an outline of the wafer processing process and a sectional view of the process.

[Thermal oxidation]

n-S 1 (110) wafer is oxidized and Sio
form 2. Sio is used as a mask for diffusion in the next step.

[Diffusion window light]

To perform selective diffusion, Sio is removed and diffusion windowing is performed.

〔diffusion〕

Diffusion is carried out using a BN solid grazing source, etc. Boron diffuses only where the silicon surface is exposed, changing from n-type to p-type.

(CVD-3i, N,) Deposit CVD-3L,N on both sides.

The front side is used as a barrier against external contamination, and the back side is used as a mask when etching the silicon substrate.

[Contact hole]

A contact hole for electrically connecting the detection element 3 is made by etching.

[Aluminum deposition/processing]

The detection elements 3 are interconnected and electrically connected to an external circuit using aluminum.

[Sintering]

Sintering is performed to improve the ohmic properties of the aluminum and gauge resistor.

[Dicing]

After completing the silicon processing step, it is separated into individual sensor chips.

Further, a strain body 4 is provided which acts as a reinforcing substrate for reinforcing the single crystal substrate 1. This strain-generating body 4 has a disk shape, and the outer peripheral part is a support part 6 equipped with a fixing screw hole 5, and the center part 7 is formed with a force transmitting body 8. A circular recess 9 is formed around the periphery, and an elastically deformable surface 10 in the shape of a wall is formed. This elastic deformation surface 10
The single crystal substrate 1 is adhesively fixed to the surface of the substrate.

These 12 detection elements 3 are connected to the outside via connection terminal portions 11 formed to be connected to the detection elements 3. That is, a flexible printed circuit board 13 on which external connection terminals 12 are formed is adhesively fixed to the strain body 4, and this flexible printed circuit board 13 is
The connection terminal portion 11 is connected to a relay terminal 14 formed in the wafer via a wire bond 15.

After the single crystal substrate 1 is adhesively fixed to the strain body 4 in this manner, a cap 16 is provided on the detection surface 2 side to isolate the single crystal substrate 1 from the outside air.

Therefore, the forces acting on the force transmitting body 8 include forces (Fx, Fy+Fz) along each axis, that is, x, y, and z directions that are three-dimensionally orthogonal to each other, and moments around each axis ( M x , My y , M Z
It is formed as shown in (C).

In such a configuration, by applying an external force to the force transmitting body 8, the strain body 4 is deformed, and in response to the deformation of the strain body 4, internal stress is generated in the single crystal substrate 1. The detection element 3 is deformed by the resulting strain, and a resistance change ΔR occurs due to the piezoresistive effect. That is, since the external force acting on the force transmitting body 8 is received by the strain body 4 and the strain body 4 deforms, the single crystal substrate 1 is deformed. It is capable of receiving loads. Furthermore, even if an impact load is applied to the force transmitting body 8, the impact is not directly transmitted to the single crystal substrate 1, but is buffered by the strain body 4, so that the single crystal substrate 1 is made of a highly brittle material. are well protected.

Here, the resistance change ΔR when stress is present is ΔR/
R=π2σ0+πtσL+πSσS... (1
) π2: Vertical piezo resistance coefficient πt=Transverse piezo resistance coefficient πS: Shear piezo resistance coefficient σL: Longitudinal stress σt: Lateral stress σS: Shear direction stress.

Here, since the shear stress σS is smaller than σ°C and σt, the following discussion will ignore this shear stress σS.

Furthermore, as mentioned above, since the shape of the detection element 3 is set to fl, (Q) as shown in FIG. 5, πL and σt in equation (1) can be ignored. So, the formula (
1) becomes the following equation (2).

ΔR/R=π2σU (2) At this time,
If three components of force, Fz, Mx, and My, act on the force transmitting body 8, the change in resistance of the detection element 3 will be as shown in FIGS. 2 and 6 below.

That is, [when Mx is added] Rx,, Rx, decreases, Rx,, Rx, increases RV, Ry, Ry,, Ry4 remains unchanged RZ,,
RZ, decreases, Rz, , Rz4 increases [When My is added, I Rx,, Rx2. Rx,, Rx4 are unchanged RY3. RY3 decreases, RYt+ RL increases R1
r + RZ i decreases, Rz, , Rz4 increases [when Fz is added] Rx, , Rx4 decreases, Rx, , Rx, increases R
y1. RL decreases, R'Wx, RYs increases Rz,...
Rz4 decreases, Rz2. Rz increases.

A summary of such resistance changes is shown in Table 1 below.

Table 1 In order to detect these three force components (Mx, My, Fz), a bridge circuit is configured as shown in Figure 5, so each force component can be detected without being interfered with by the other force components. Mx, My, and Fz outputs are obtained for each circuit.

For example, Fig. 5 (a) (b) (c) when Mx is added.
The output of is as follows.

First, in Figure 5(a), becomes.

Here, for simplicity, Rx, = Rx, = R
When x3=Rx4=R, equation (3) becomes V=O.

Also, the increase in resistance due to Mx is ΔR, and the decrease is -ΔR.
Then, from Table 1, the output by Mx is 4R = ΔR・engine (4).

In other words, the output change (■ to sensitivity) due to Mx is Δ■ =
ΔR････････････(5).

Next, in FIG. 5(b), becomes.

Here, Ry+ = RL = RVs =RY4=
When R, equation (6) becomes V=O.

Also, assuming that there is no resistance change due to Mx, -〇・
(7) That is, the sensitivity Δ■ due to Mx is as follows: ΔV=O (8).

Next, in FIG. 5(C), if Rz,=Rz2=Rz,=Rz4=R, equation (9) becomes V=O.

Also, the increase in resistance due to Mx is ΔR1 decrease is -ΔR
Then, =0 (10). In other words, the sensitivity Δ■ due to Mx is V=O...
...(11) becomes.

The above matters have been described for Mx, but the same can be considered for My and Fz.

Therefore, in the bridge circuit of FIGS. 5(a), 5(b), and 5(c), (i) the resistance of each detection element 3 is equal.

(ii) The increase/decrease ΔR of the resistance of the detection element 3 is equal.

Under these conditions, the three components Mx, My, and Fz can be detected without interfering with each other.

A second embodiment of the present invention will be described based on FIGS. 8 and 9. This embodiment is different from the previous embodiment in the means for extracting the output of the detection element 3 to the outside. That is,
The strain body 4 also serves as a stem for extracting the output signal of the detection element 3 to the outside, and a plurality of lead pins 17 are arranged on the outer periphery of the single crystal substrate 1.

A third embodiment of the present invention will be described based on FIGS. 10 and 11. In the embodiment described above, the single crystal substrate 1 and the strain body 4 are separate members, and it is necessary to accurately determine the center position of both. That is, if a positional shift occurs between the center positions of the two, interference between the respective component forces occurs, resulting in a problem that the detection accuracy decreases. However, due to processing problems, it is impossible in a strict sense to eliminate the relative positional deviation between the two, and this embodiment allows such relative positional deviation to some extent.

Therefore, in this embodiment, the force transmitting body 8 is positioned on the elastically deformable surface 10 of the strain body 4 on a concentric circle with the force transmitting body 8 as the center.
circular holes 18 are formed at equal intervals. These holes 18 are located between each of the detection elements 3, Rx, , Rx, , Rx3 .
Detection element 3 Rx4 and Ry, , Ry! .

Detection element 3 RY, RY4 and RZ+ + RZz
+ RZs + RZ4 and the detection elements 3 are formed at relative positions of 22.5 degrees to each other.

In such a configuration, when an external force is applied to the force transmitting body 8, deformation occurs in the elastic deformation surface 10 in a direction corresponding to the external force, but since the holes 18 are provided, the generation of this strain is mainly suppressed. This occurs only in the radial direction, and there is no stress in the circumferential direction. This eliminates interference between component forces, and component forces can be separated favorably. Furthermore, the presence of the hole 18 expands the strain imparted to the detection element 3, improving sensitivity. Regarding the single-crystal substrate 1, the sensitivity improves when the thickness is 0.3 mm or less, but this thickness causes poor workability and poor yield, so it is necessary to avoid these problems. It is preferable to set the hole 18 to a thickness of .

Next, a fourth embodiment of the present invention will be described based on FIG. In this embodiment, the holes formed in the elastically deformable surface 10 of the strain body 4 are fan-shaped holes 19. This shape effectively prevents the generation of stress in the circumferential direction and causes strain to occur only in the radial direction.

Furthermore, what is shown in FIG. 13 is a fifth embodiment of the present invention, in which a hole 20 having the same shape as the hole 18 formed in the strain body 4 shown in FIGS. 10 and 11 described above is formed in a single crystal. It is also formed on the substrate 1. Therefore, in a single crystal substrate 1 without holes 20, when there is a temperature change, the single crystal substrate 1 deforms in the Z-axis direction and the output of the two components changes, but in this example, By forming the holes 20, thermal stress is dispersed and the temperature characteristics of the Z component are stabilized. In addition, in the case of this embodiment, since the holes 18° and 20 have the same shape and the same dimensions, the relative position of the single crystal substrate 1 with respect to the strain body 4 can be accurately determined using a positioning pin or the like. It is something. Of course, although not particularly shown in the drawings, a pin for positioning both may be specially prepared and the pin may be driven into the strain body 4 and the single crystal substrate 1.

What is shown in FIG. 14 is a sixth embodiment of the present invention, in which a sector-shaped hole 21 similar to the sector-shaped hole 19 is formed also in the single-crystal substrate 1 in contrast to the fourth embodiment described above. It is. Therefore, the generation of stress in the circumferential direction is effectively prevented so that strain occurs only in the radial direction, and the thermal stress in the single crystal substrate 1 is dispersed, thereby stabilizing the temperature characteristics of the Z component. Furthermore, in the case of this embodiment as well, since the fan-shaped holes 19 and 21 have the same shape and the same dimensions, it is possible to accurately determine the relative position of the single crystal substrate 1 with respect to the strain body 4 using a positioning pin or the like. It is possible.

In each of the third to sixth embodiments, the hole 18.20 or the fan-shaped hole 19.21 is formed in the strain body 4 and/or the single crystal substrate 1. Since it is designed to prevent the generation of stress in the circumferential direction and only generate stress in the radial direction, it may be formed with a notch instead of a hole shape.

Further, regarding the shape of the holes 18, 20 or the fan-shaped holes 19, 21 described above, it is also possible to use an elliptical hole, a polygonal hole, or the like.

Effects As described above, the present invention provides a single-crystal substrate having a detection surface formed over one surface, which is equipped with a detection element that changes electrical resistance by mechanical deformation, and has either the center portion or the peripheral portion supported by a support member. A strain-generating body with the other side as an acting part is provided, and the single crystal substrate is adhesively fixed to the surface of this strain-generating body, so that the external force acting on the acting part can be received by the strain-generating body, and the strain-generating body is Since the single crystal substrate is deformed by deforming the body, it can receive a load that cannot be received by a single crystal substrate, and even if an impact load is applied to the acting part, the impact will be transferred to the single crystal substrate. Since the force is not directly transmitted to the substrate and is buffered by the strain body, even if the single crystal substrate is made of a highly brittle material, it is sufficiently protected and highly reliable force detection can be performed. Since holes or notches are formed in the single-crystal substrate and/or the strain-generating body, it is possible to eliminate stress in the circumferential direction and apply only stress in the radial direction to the detection element. This allows a state of high sensitivity to be obtained.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional side view showing the first embodiment of the present invention, and the second
The figure is a plan view with the cap removed, Figure 3 is I)
- A characteristic diagram showing the piezoresistance coefficient in S 1 (110), Fig. 4 is a plan view showing the shape of the detection element, Fig. 5 (
a)(b)(c) are bridge circuit diagrams, Fig. 6(a)(b)
) and (c) are characteristic diagrams showing various stress generation states, Fig. 7 is a manufacturing process diagram, Fig. 8 is a longitudinal cross-sectional side view showing the second embodiment of the present invention, and Fig. 9 is with the cap removed. FIG. 1o is a plan view showing the third embodiment of the present invention.
1 is a longitudinal sectional side view thereof, FIG. 12 is a plan view showing a fourth embodiment of the present invention, FIG. 13 is a plan view showing a fifth embodiment of the present invention, and FIG. 14 is a plan view showing a fourth embodiment of the present invention. It is a top view which shows Example 6. DESCRIPTION OF SYMBOLS 1... Single crystal substrate, 2... Detection surface, 3... Detection element, 4... Strain body, 6... Support part, 7... Center part,
18.20...hole, 19.21...fan-shaped hole (hole) Applicant: Ricoh Co., Ltd.

Claims (1)

[Claims] 1. A single-crystal substrate with a detection surface formed over one surface and equipped with a detection element that changes electrical resistance by mechanical deformation is provided, and one of the center portion and the peripheral portion is used as a support portion. 1. A force detection device comprising: a strain-generating body with the other end serving as an action portion; and the single crystal substrate is adhesively fixed to the surface of the strain-generating body. 2. A single-crystal substrate with a detection surface formed over one surface, equipped with a detection element that changes electrical resistance through mechanical deformation, is provided, and one of the center and peripheral parts is used as a support part and the other part is used as an action part. A force detection device characterized in that a strain-generating body is provided, the single-crystal substrate is adhesively fixed to the surface of the strain-generating body, and a hole or a notch is formed in the single-crystal substrate and the strain-generating body, or in either one thereof. . 3. Claim No. 3, characterized in that a plurality of holes or notches are formed in the single crystal substrate and the strain-generating body, or in either one, and these holes or notches are arranged on the same circumference. The force detection device according to item 2.