JP2960510B2 - Flexure element structure of semiconductor 3-axis force sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a strain-generating body structure of a diffusion type semiconductor three-axis force sensor in which a silicon single crystal substrate on which a diffusion strain gauge is formed is bonded on a strain-generating body.

(Prior Art and Problems Thereof) First, an outline of a diffusion type force sensor to which the present invention is applied will be described.

Conventionally known force sensors have a strain gauge attached to a strained body processed into a three-dimensional structure, but cannot be said to be sufficient in terms of size, sensitivity, and price. there were.

However, by improving such a conventional force sensor, applying mechanical external force to a silicon single crystal plate causes distortion in the crystal lattice, changing the number of carriers and mobility in the semiconductor, and changing the resistivity. A semiconductor three-axis force sensor using a method of converting a strain element and strain into a change in resistance using a phenomenon, ie, a piezo effect, and converting a force applied to the strain element into an electric signal by a blitch circuit has been devised. Was.

FIG. 5 is a sectional view of the above-described semiconductor three-axis force sensor (hereinafter simply referred to as a force sensor). The strain sensor 11 of the force sensor 10 is formed by an outer peripheral portion 11a, an inspection arm 13 projecting perpendicularly to the center, and an annular diaphragm 12 between the outer peripheral portion 11a and the detection arm 13. 14-1, 14-2, 14-3, and 14-4 above the edges 12a and 12b (the boundary between the outer peripheral portion 11a and the detection arm 13) (the surface opposite to the edges 12a and 12b). A gauge resistor 14 is formed. This gauge resistance is formed on one diameter of the flexure element 11 by 14-1, 14-2, 14-3, 14-.
4 are arranged in order.

This flexure element 11 has a moment Mx, My in the X-axis or Y-axis direction.
FIG. 6 and FIG. 7 show deformation simulations in the case where the force acts or the force Fz (pressing force or tension) in the Z-axis direction acts.

8, 9 and 10 show the gauge resistance of the force sensor 10 described above.
14-1, 14-2, 14-3, and 14-4 show the configuration of the bridge circuit.
When 1,14-2,14-3,14-4 is subjected to an external force, the electric resistance Rx ₁ to Rx bridge circuit each side _{4, Ry 1 ~Ry 4, Rz} 1 ~Rz 4 are shown in Table 1 Causes a change, the X-axis moment (Mx), Y
Axial moment (My) and Z-axis pressing force (Fz) can be detected.

Here, each gauge resistance 14-1, 14-2, 14-3, 14-
Reference numeral 4 denotes the X-axis, Y-axis, and Z-axis bridge resistors x _{1 to} Rx ₂ and Ry ₁ to
Ry ₄ , common to Rz _{1 to} Rz ₄ .

However, since the diaphragm 12 of the conventional flexure element 11 has a uniform thickness structure, the sensitivity in the Z direction is inferior to Mx and My. Therefore, if there is a difference in sensitivity, when a force is applied to the force sensor as shown in FIG. 11, the rated load in each direction becomes an elliptical spherical distribution.

The distribution of the rated force in the force sensor shown in FIG. 11 is such that, when the rotation center when a moment is applied is P, and a position 1 away from P is an action point F, the rated force distribution is In the force distribution shape, the rated force in the F direction does not change, and only the rated force in the X and Y directions decreases.
As shown in the equation, the force distribution becomes flatter.

_{Fx 0 = Mx 0 / l ··} Fy 0 = My 0 / l , but here in the Fx _0, Fy ₀ is Teikakuryoku Mx _0, My ₀ strong strength in the F direction as described above rated moment, Mx, My However, it had a disadvantage that it was weak and easily broken.

Ideally, when a force is applied to the detection arm 13 as shown in FIG. 12, it is desirable that the force distribution of the rated load be completely spherical.

When using a force sensor as shown in Fig. 11, it can only be used within a perfect spherical range that falls within its force distribution except in special cases, and the S / N ratio to Fz deteriorates. There is a problem that the detection accuracy in the Z direction is significantly reduced.

An object of the present invention is to provide a force sensor capable of detecting the X-axis, the Y-axis moment, and the Z-axis pressing force with the same sensitivity by solving the above-described problems.

(Means for Solving the Problems) In order to achieve the above object, in a force sensor 20 in which a silicon single crystal plate having a diffusion strain gauge formed thereon is joined to a strain body 21, a strain sensor and a detection arm are provided. And two opposed L-shaped arms provided between the L-shaped arm and the detection arm, and between the L-shaped arm and the strain-generating body. A diaphragm 25 is provided to separate the X-axis and Y-axis moments into separate diaphragms 25 (25a, 25b) for detection.

(Operation) As described above, the moment of the X axis and the moment of the Y axis are detected by different diaphragms, and the pressing force of the Z axis uniformly deforms all the diaphragms. Is detected.

Here, l (distance from point P to action point F) is L / 2
If the (distance from the center of the flexure element to the diaphragm) is equal, when the force is applied to the point F so as to generate a moment, the deformation of the diaphragm generated when the same force is applied in the Z direction is almost equal. Therefore, the detection sensitivities of X, Y, and Z become substantially equal.

(Embodiment) FIG. 1 is a plan view of a force sensor according to an embodiment of the present invention viewed from a gauge resistance side, and FIG. 2 is a reference structural diagram of a main part.
(A) is a perspective view, and (B) is a plan view.

This force sensor 20 has a rectangular window at the center of the flexure element 21.
A detection arm 23 having a rectangular shape is disposed at the center of the window 22, and a rectangular wall having sufficient rigidity is formed between the upper surface of the detection arm 23 and the periphery of the window 22. A frame 24 is arranged.

Between the detection arm 23 and the frame 24, diaphragms 25a and 25b are arranged on both sides in the longitudinal direction so as to straddle both members, and the two members are configured to be separated by the same distance. And the relative position of the frame 24 is maintained.

Further, diaphragms 25b, 25b having the same shape as the diaphragm 25a between the detection arm 23 and the frame 24 are formed in the same manner at the center of each of the opposed long sides of the frame 24 and the window 22 of the strain body 21. Thus, the relative position between the frame body 24 and the strain body 21 is maintained.

As shown in FIG. 2 (b), the diaphragms 25a and 25b (generally referred to as 25) are rectangles having a long side length a and a short side length b, each having a long side surface. Of the opposed diaphragms 25, 25 in the configured state, those 25a, 25b between the detection arm 23 and the frame 24, and those 25b, 25b between the frame 24 and the long side of the window 22. The intervals between the center lines in the longitudinal direction are configured to have the same length L.

Each of the diaphragms 25 has a length a in one direction that is sufficiently larger than a length b between the two straddling members so as to make it difficult to deform under a load other than the detection component, thereby preventing the occurrence of interference output. It is.

The four diaphragms 25 are all at the same height, and only those portions are joined to the sensor chip 27 so that the displacement of the frame body 24 is not transmitted to the sensor chip 27. .

However, in the case of wire bonding, if the bonding position of the sensor chip 27 is in the air, the sensor chip 27 is broken, so the pedestal 26 is placed on the surface of the strain body 21 at the same height as the diaphragm 25. And it is better to join this portion in the same manner as the diaphragm 25.

However, the pedestal 26 should be arranged so as to be located on the side of the My diaphragm 25b. This is because when a load in the Z-axis direction is applied, the diaphragm 25a for Mx generates a displacement just twice as much as the diaphragm 25b for My,
This is because an excessive force is not applied to the sensor chip 27.

FIG. 4 is a gauge resistance array diagram of the sensor chip 27 (shown by a two-dot chain line in the figure) at the center of the strain body 21 shown in FIG. Since the above-mentioned diaphragms 25 are arranged on one plane, the sensor chip 27 is joined to each of the four diaphragms 25. This sensor chip 27
Two center lines XX (X
Rx ₁ , Rx ₂ , Rx ₃ , and Rx ₄ are arranged on the diaphragm 25 from below on one X-axis of Y-Y (Y-axis), and Ry is on the Y-axis from the left. _{1, Ry 2, Ry 3,} Ry 4 are arranged. Respectively on the left side as viewed from the center point C for these _{Rx 1 ~Rx 4, Ry 1 ~Ry} 4 Rz 1 ~Rz 8 and Rz ₁ ~Rz ₄ are arranged in close proximity.

 Next, the operation of the above-described force sensor 20 will be described.

When a force is applied to the tip of the detection arm 23 in a direction inclined to both the X axis and the Y axis, the diaphragms 25a and 25b bend in the short side b direction due to the X component of the force, but the long side a direction It is difficult to deform and the frame 24 is inclined. As a result, the diaphragms 25b, 25b undergo the same deformation as the diaphragm 25a due to the Y component of the force.

As a result, the diaphragm 25a detects the X component of the force, and the diaphragm 25b detects the Y component.

Further, since the Z component of the force is in the direction of the central axis of the detection arm 23, the force becomes a pressing force on the detection arm 23, and the diaphragm 25 is deformed in the same shape.

The distance between the diaphragms 25a, 25a and the diaphragm
Since the distance between 25b and 25b is the same L, the sensitivity is the same as the Y component of the X component, and the Z component is distributed to four diaphragms 25. The total sensitivity is the same as the sensitivity of the X component and the Y component.

FIG. 3 is a block diagram showing a main part of the present invention, in which two L-shaped arms 28, 28 are divided instead of the frame 24 of FIG. A diaphragm 25a is formed between the detection arm 23 and the long side of the window 22 at the end of the long side of the L-shape. Are integrally formed.

The other parts are the same as in the case of FIG. 2 and the operation is the same, so that the description is omitted.

(Effects of the Invention) As described above, when a force is applied to the detection arm 23, the rated load in each direction shows a uniform force distribution in any direction, and the detection accuracy does not vary depending on the direction.

[Brief description of the drawings]

FIG. 1 is a plan view of a force sensor according to one embodiment of the present invention as viewed from the gauge resistance side, FIG. 2 is a reference view of a main part, (a) is a perspective view, (b) is a plan view, 3 is a structural view showing a main part of the present invention, (a) is a perspective view, (b) is a plan view, FIG. 4 is a gauge resistance arrangement diagram of a sensor chip, and FIG. 5 is a conventional force sensor. FIG. 6 is a deformation simulation diagram of the X (Y) axis direction, FIG. 7 is a deformation simulation diagram of the pressing force in the Z axis direction, FIG. 8 is a bridge circuit diagram for the X axis, and FIG. FIG. 10 is a Z-axis bridge circuit diagram, FIG. 11 is an operation characteristic diagram of a conventional diffusion type force sensor, and FIG. 12 is an operation characteristic diagram of an ideal force sensor. 20: force sensor, 21: strain body, 23: detection arm, 24: frame, 25: diaphragm, 27: sensor chip, 28: L-shaped arm.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01L 5/16 H01L 29/84

Claims (1)

(57) [Claims] In a semiconductor three-axis force sensor in which a silicon single crystal plate on which a diffusion strain gauge is formed is joined to a strain body, two opposed L sensors provided between the strain body and a detection arm.
A L-shaped arm and a diaphragm integrally formed between the L-shaped arm and the detection arm and between the strain body and the L-shaped arm so as to straddle both members,
A flexure element structure for a semiconductor three-axis force sensor, wherein moments in the X-axis and the Y-axis are separately detected on separate diaphragms.