JP2001264198A - Method for manufacturing multiaxial tactile sensor and tactile sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a fine multiaxial tactile sensor and a tactile sensor which are applicable to a microcomputer and have high sensitivity. SOLUTION: In one style, the multiaxial tactile sensor has opening parts which are provided to a flat plate type semiconductor substrate, a support part which is formed of the outer periphery of the semiconductor substrate, an elastic connection part which extends from the support part to the center of the semiconductor substrate, a force operation part which is nearly in the center of the support part and connected to the support part by the connection part, and a strain detecting element which is provided on the connection part, and is characterized by that the connection part is formed of a diffusion area formed by doping a P type semiconductor with N type impurities and a made thinner than the support part and force operation part by electrochemical etching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a force sensor,
In particular, the present invention relates to a multi-axis force sensor applied as a micro force sensor used for handling micro parts, cells, and the like, and a method of manufacturing the force sensor.

[0002]

2. Description of the Related Art With the development of micromachine technology in recent years, micromanipulators capable of high-accuracy position control for handling microparts and manipulating cells have been developed.

[0003] As a conventional technique of such a micromanipulator, for example, IEEEInternatio
nal Conference on Robot a
nd Automation, 1995, pp. 139-143. 167
"Two-Finger" disclosed in U.S. Pat.
Micro Hand "(two-finger micro hand).

Hereinafter, this conventional technique will be described with reference to FIG.

That is, in this two-finger micro hand, a pair of glass needles 101 are driven by the piezoelectric element 102.

In this two-finger micro hand, the piezoelectric element 1
By precisely controlling the displacement of 02, it becomes possible to perform delicate handling such as cell operation using a pair of glass needles 101 like chopsticks.

In a manipulation system using a manipulator with such a two-finger microhand, a control system is configured to detect and feed back a small stress when handling a small component or a cell having a low mechanical strength. It is desirable.

On the other hand, in a manipulator of an industrial robot that handles relatively large-sized components and the like, a multiaxial force sensor for forming a feedback control system is used.

A prior art of this type of force sensor is disclosed in Japanese Patent Application Laid-Open No. 5-149911.
An axial force sensor is used.

Hereinafter, this prior art will be described with reference to FIG.

FIG. 8 is a schematic view of a flexure element used in the six-axis force sensor.

That is, the support portion 103 and the force acting portion 1 formed on the strain body 107 manufactured in a flat plate shape by machining.
04 are connected by a first elastic beam 105 and a second elastic beam 106, and at the appropriate positions of the first elastic beam 105 and the second elastic beam 106, orthogonal three-axis forces and A plurality of sets of bridge circuits (not shown) for independently detecting moments around these axes are provided.

In such a configuration, the multi-axial (six-axis) is detected by detecting the distortion generated in the elastic beam due to the stress.
Of the force sensor.

In the six-axis force sensor using such a flexure element, each acting force can be detected without requiring a complicated transformation matrix or interference correction calculation.

[0015]

However, in a micromanipulator used for cell manipulation and handling of small parts as shown in FIG. 7, it is necessary to work in a minute space, so that the size of the force sensor is also small. Limited, the stress to be measured is very small, nN ~ μ
Since force detection on the order of N is necessary, as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-149811,
It is difficult to apply a multi-axis force sensor constituted by a strain element manufactured by conventional machining in terms of both size and sensitivity.

The present invention has been made in view of the above circumstances, and has as its object to provide a highly sensitive and minute multi-axis force sensor applicable to a micromanipulator and a method of manufacturing the force sensor.

[0017]

According to the present invention, in order to solve the above-mentioned problems, (1) a plurality of openings provided in a flat semiconductor substrate, and a support portion comprising an outer periphery of the semiconductor substrate are provided. An elastic connecting portion extending from the supporting portion to the center of the semiconductor substrate, a force acting portion substantially at the center of the supporting portion, and connected by the supporting portion and the connecting portion; A strain detecting element provided on the connecting portion, wherein the connecting portion is formed of a diffusion region in which a P-type semiconductor is doped with an N-type impurity, and is formed thinner than the support portion and the force acting portion by electrochemical etching. A multi-axis force sensor is provided.

(Corresponding Embodiment of the Invention) One embodiment described later corresponds to this embodiment.

(Operation) In the flexure element 1 made of a flat semiconductor substrate having a plurality of openings, the support portion 7, the force acting portion 8 and the elastic beam portion 9 as a connecting portion are formed by electrochemical etching. It is formed of an integrated single-crystal silicon thin plate extracted from a semiconductor substrate.

Here, the elastic beam portion 9 as a connecting portion
Comprises a diffusion region doped with an N-type impurity, the shape of which is defined by electrochemical etching.
And it is formed thinner than the force acting portion 8.

According to the present invention, in order to solve the above-mentioned problems, (2) a flexible thin film having a plurality of wirings formed therein is integrally formed on the semiconductor substrate; The multiaxial force sensor according to (1), wherein a circuit provided on the semiconductor substrate and an external signal processing circuit can be connected by wiring provided inside the multi-axis force sensor.

(Corresponding Embodiment of the Invention) One embodiment described later corresponds to this embodiment.

(Operation) A detecting piezoresistive element 11 and a temperature compensating diffused resistive element 12 as strain detecting elements formed on an elastic beam portion 9 as a connecting portion in the strain generating element 1.
Is electrically connected to the external lead portion 3 on which the external lead electrode 20 (19 ') is formed via the flexible thin film region 2 via the aluminum thin film wiring layer 15.

According to the present invention, in order to solve the above-mentioned problems, (3) a first surface of a P-type silicon substrate is formed so as to surround a portion corresponding to a sensor region formed on a second surface. A step of forming a silicon nitride film, a step of forming a deep N-type diffusion layer in a region where a support portion, a force acting portion and an external lead portion are formed; and a step of forming a shallow N-type diffusion region in a region where a connection portion is formed. Forming a type diffusion layer;
Forming a strain detecting element on the silicon diffusion layer, sequentially forming a lower polyimide film, an aluminum wiring layer and an upper polyimide film on the silicon substrate; and forming the deep N-type diffusion from the first surface of the silicon substrate. Electrochemically etching the silicon substrate with an aqueous solution of potassium hydroxide in a state where a positive voltage is applied to the layer and the shallow diffusion layer.

(Corresponding Embodiment of the Invention) A method of manufacturing a force sensor according to an embodiment described below corresponds to this embodiment.

(Function) In the flexure element 1 made of a flat semiconductor substrate having a plurality of openings, the support portion 7, the force acting portion 8 and the elastic beam portion 9 as a connecting portion are electrochemically etched. And an elastic beam portion 9 as a connecting portion thereof is defined as a diffusion region doped with an N-type impurity and its shape is defined by electrochemical etching. , A silicon nitride film is formed on the first surface of the P-type silicon substrate so as to surround a portion corresponding to the sensor region formed on the second surface. Forming a deep N-type diffusion layer in a region where a support portion, a force acting portion and an external lead portion are formed; and forming an N-type diffusion layer shallower than the deep diffusion layer in a region where a connection portion is formed. Deep N-type diffusion And a lower polyimide film, an aluminum wiring layer and an upper polyimide film are sequentially formed on the silicon substrate, and the deep N-type diffusion layer and the shallow diffusion layer are formed from the first surface of the silicon substrate. The silicon substrate is electrochemically etched with an aqueous potassium hydroxide solution while a positive voltage is applied.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view schematically showing a configuration of an application of a multiaxial force sensor according to an embodiment of the present invention.

That is, in one embodiment of the present invention, the triaxial force sensor 4 composed of the flexure element 1, the flexible thin film section 2 and the external lead section 3 is fixed to the drive section of the micromanipulator. A small gripping bar 5 made of a glass needle or the like, which actually grips the cells and the like, is fixed to the center portion of the flexure element 1 by a method such as adhesion.

Next, each area of the force sensor 4 will be described.

FIG. 2 shows the structure of one portion of the flexure element of FIG.

FIG. 2A is a plan view of a portion of the flexure element 1, and FIG. 2B is a sectional view taken along line AA 'of FIG. 2A.
It is sectional drawing, (c) of FIG. 2 is B- of FIG.
It is B 'sectional drawing.

That is, the strain-generating body 1 composed of a flat-plate-shaped semiconductor substrate provided with a plurality of openings 1a is provided with a support portion 7 in the form of a flat rectangular frame on the periphery and a force-applying portion 8 in the center. And four elastic beam portions 9 as a connecting portion for connecting the support portion 7 and the force acting portion 8 to each other.
The flexible thin film portion 2 extends from one side.

An opening 10 is formed at the center of the force acting portion 8 for fixing the force acting portion 8 through the grip bar 5 shown in FIG.

Further, four elastic beam portions 9 are used as connecting portions.
Are each formed with a piezoresistive element 11 for detection as a strain detecting element.

Further, a temperature-compensating diffusion resistance element 12 is formed in the vicinity of a connection portion between the support portion 7 and the four elastic beam portions 9 as the connection portion.

On the surface of the strain body 1, a lower polyimide film 13 and an upper polyimide film 14 are laminated.

The lower polyimide film 13 and the upper polyimide film 14 extend from one side of the strain body 1 as they are to form the flexible thin film portion 2.

An aluminum thin film wiring is provided at both ends of each of the detecting piezoresistive elements 11 and each of the temperature compensating diffused resistive elements 12 as strain detecting elements through openings formed in predetermined portions of the lower polyimide film 13. Layer 15 is electrically connected.

Although not particularly shown, the aluminum thin film wiring layer 15 provided between the lower polyimide film 13 and the upper polyimide film 14 is formed on the flexure element 1 with an arbitrary layout. The piezoresistive element 11 for detection as a strain detecting element and the diffusion resistance element 12 for temperature compensation are drawn out to the external lead section 3 through the flexible thin film section 2 as described later.

Here, the support portion 7 constituting the flexure element 1 and
The force acting part 8 and the elastic beam part 9 as a connecting part are P
It is formed of an integrated single-crystal silicon thin plate extracted from a mold semiconductor substrate by electrochemical etching.

The elastic beam portion 9 as a connecting portion
Is formed of a diffusion region in which a P-type semiconductor substrate is doped with an N-type impurity, the shape of which is defined by electrochemical etching, and is formed thinner than the support portion 7 and the force acting portion 8.

Next, the structure of the external lead portion 3 will be described with reference to FIG.
This will be described with reference to FIG.

Here, (a) of FIG.
FIG. 3B is a plan view of FIG.
It is C 'sectional drawing.

That is, the external lead portion 3 comprises a single-crystal silicon thin plate 16 extracted from a P-type semiconductor substrate by electrochemical etching, and a lower layer extending from the flexible thin-film portion 2 above the single-crystal silicon thin plate 16. It is composed of a polyimide film 13 and an upper polyimide film 14.

A CMOS circuit 17 is formed in a predetermined region of the single-crystal silicon thin plate 16.

The CMOS circuit 17 includes the strain body 1
An aluminum thin film wiring layer 15 connected to each detection piezoresistor element 11 as a strain detection element and each temperature compensation diffusion resistance element 12 is connected through a flexible thin film portion 2.

On the other hand, the plurality of external lead electrodes 20 as a force sensor are constituted by a thin film aluminum wiring layer 19 having an exposed portion 19 ′ exposed at an opening 18 formed in the upper polyimide thin film 14.

The thin aluminum wiring layer 19 is also connected to the CMOS circuit 17.

Here, the CMOS circuit 17 applies a voltage to each of the detecting piezoresistive elements 11 and each of the temperature compensating diffused resistive elements 12 as the strain detecting elements, measures the resistance value, and performs A / A
The electronic circuit includes a function of performing D conversion and outputting the measured value to an external controller via a plurality of external lead electrodes 20 in a time sharing manner.

Next, a method of manufacturing the force sensor according to the present embodiment will be described with reference to FIGS.

First, as shown in FIG. 4, a silicon nitride film 21 is formed on the back surface of the P-type silicon substrate 100 so as to surround a portion corresponding to a region where a force sensor is formed on the front surface side. 1 support portion 7, force acting portion 8, external lead portion 3
A deep N-type diffusion layer 22 is formed in a region corresponding to the single-crystal silicon thin plate 16, and a shallow diffusion layer 23 is formed in a region corresponding to the elastic beam portion 9 as a connecting portion in the strain body 1.

At this time, no N-type diffusion layer is formed in a region corresponding to the central opening 10 of the strain body 1.

In a predetermined region of the deep N-type diffusion layer 22, a piezoresistive element 11 for detection as a strain detecting element and a CMOS circuit 17 are formed. In a predetermined region of the shallow N-type diffusion layer 23, Each temperature compensating diffusion resistor 12 is formed.

Here, each detecting piezoresistive element 11 as a strain detecting element and each temperature compensating diffused resistor 12 are formed in the same step by diffusing a P-type impurity into the P-type silicon substrate 100. Is done.

The CMOS circuit 17 is provided with a normal CMOS
It is formed by the same process as the S-IC.

Next, as shown in FIG. 5, a lower polyimide film 13, thin-film aluminum wiring layers 15 and 19, and an upper polyimide film 14 are sequentially formed.

At this time, the lower polyimide film 13 has an opening for electrically connecting the thin film aluminum wiring layer 15 with each of the detecting piezoresistors 11 and each of the temperature compensating diffusion resistors 12 as the strain detecting elements. Then, an opening for electrically connecting the thin film aluminum wiring layer 15 and the thin film aluminum wiring layer 19 to the CMOS circuit 17 is formed.

In the upper polyimide film 14, an opening 18 for an external lead electrode 20 (19 ') is formed.

Next, as shown in FIG. 6, with the silicon nitride film 21 as a mask, a positive voltage is applied to the deep N-type diffusion layer 22 and the shallow N-type diffusion layer Performs the electrochemical etching of the P-type silicon substrate 100.

By this step, the region of the deep N-type diffusion layer 22 and the region of the shallow N-type diffusion layer 23 and the region where the depletion layer extending therefrom was formed can be selectively left.

Thereafter, the lower polyimide film 13 and the upper polyimide film 14 are cut into a predetermined shape by a technique such as excimer laser ablation, so that the force sensor shown in FIG. 1 can be obtained.

At this time, the lower polyimide film 13 remaining in the region of the opening 10 is also removed.

As described above, in the force sensor according to the present embodiment, the flexure element 1 including the support portion 7, the connecting portion 9, and the force acting portion 8, the strain detecting element (strain sensing element), Can be formed integrally with the semiconductor manufacturing technology, so that the size can be significantly reduced as compared with the conventional multi-axis force sensor, and the external lead portion 3 including the flexure element 1 and the signal processing circuit is flexible. Since it is electrically connected via the conductive thin film region 2, it can be freely bent at this portion, so that the force sensor can be arranged in a very narrow space.

In addition, the strain body 1 is integrally formed by electrochemical etching. In this case, the thickness is basically defined by the impurity profile of the semiconductor, and the planar shape is defined by the photolithography process. Therefore, it is possible to form a very fine elastic beam having a width of about 10 μm and a thickness of several μm or less as a very fine connection part with good controllability, thereby realizing high-sensitivity stress measurement.

[0066]

According to the first aspect of the present invention, the strain generating element 1 including the support portion 7, the connecting portion 9, and the force acting portion 8 and the strain detecting element (strain sensing element) are formed of a semiconductor. Since it can be integrally formed by a manufacturing technique, it can be significantly miniaturized as compared with a conventional multi-axis force sensor, and the elastic beam portion 8 as a connecting portion is formed by electrochemical etching on a single crystal silicon substrate as a semiconductor substrate. As defined by
A fine shape can be formed with good reproducibility, and as a result, a highly sensitive multiaxial force sensor can be realized.

According to the second aspect of the present invention, since the strain generating portion 1 and the external lead portion 3 including the signal processing circuit are electrically connected via the flexible thin film portion 2, Since the portion can be freely bent, the multiaxial force sensor can be arranged in a very narrow space.

According to the third aspect of the present invention, the strain generating element 1 including the support portion 7, the connecting portion 9, and the force acting portion 8 and the strain detecting element (strain sensing element) are formed by a semiconductor manufacturing technology. Since it can be formed integrally with the conventional multi-axis force sensor, it is possible to significantly reduce the size as compared with the conventional multi-axis force sensor, and the elastic beam portion 8 as a connecting portion is defined by electrochemical etching on a single crystal silicon substrate as a semiconductor substrate. Therefore, a fine shape can be formed with good reproducibility, and as a result, a multi-axial force sensor with high sensitivity can be manufactured.

Therefore, as described above, according to the present invention, it is possible to provide a highly sensitive and minute multiaxial force sensor applicable to a micromanipulator and a method of manufacturing the force sensor.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view schematically showing an application configuration of a multiaxial force sensor according to an embodiment of the present invention.

FIG. 2 shows a configuration of a flexure element 1 of FIG. 1; FIG. 2A is a plan view of the flexure element 1;
2B is a sectional view taken along the line AA ′ of FIG. 2A, and FIG. 2C is a sectional view taken along the line BB ′ of FIG.

3 shows the structure of the external lead portion 3 of FIG. 1. FIG. 3 (a) is a plan view of the external lead portion 3, and FIG. 3 (b) is a plan view of FIG. (A) is a sectional view taken along the line CC ′.

FIG. 4 is a process chart for explaining a method of manufacturing a force sensor according to an embodiment of the present invention.

FIG. 5 is a process chart for explaining a method of manufacturing a force sensor according to an embodiment of the present invention.

FIG. 6 is a process chart for explaining a method of manufacturing a force sensor according to an embodiment of the present invention.

FIG. 7 is a diagram showing a two-finger microhand as an example of a micromanipulator according to the related art.

FIG. 8 is a schematic view of a flexure element used in a conventional six-axis force sensor.

[Explanation of symbols]

1a: a plurality of openings, 1: a flexure element, 2: a flexible thin film section, 3: an external lead section, 4: a 3-axis force sensor, 5: a gripping bar, 6: fixed to a drive section of a micromanipulator 7, a supporting portion, 8: a force acting portion, 9: an elastic beam portion as a connecting portion, 10: an opening for fixing through the gripping rod 5, 11: a detecting piezoresistive element as a strain detecting element, 12: diffusion compensation element for temperature compensation, 13: lower layer polyimide film, 14: upper layer polyimide film, 15: aluminum thin film wiring layer, 16: single crystal silicon thin plate, 17: CMOS circuit, 18: opening, 19 ': exposed part Reference numeral 19: a thin-film aluminum wiring layer; 20, a plurality of external lead electrodes; 100, a P-type silicon substrate; 21, a silicon nitride film; 22, a deep N-type diffusion layer;

Claims (3)

[Claims] 1. A plurality of openings provided in a flat semiconductor substrate, a support portion comprising an outer periphery of the semiconductor substrate, and an elastic connection extending from the support portion to the center of the semiconductor substrate. And a force acting unit substantially at the center of the support unit and connected by the support unit and the connection unit; and a strain detecting element provided on the connection unit. The connection unit is a P-type. A multiaxial force sensor, comprising a diffusion region in which a semiconductor is doped with an N-type impurity, and formed thinner than the support portion and the force acting portion by electrochemical etching. 2. A flexible thin film having a plurality of wirings formed therein is integrally formed on the semiconductor substrate, and a wiring provided inside the flexible thin film is used to connect a circuit on the semiconductor substrate to a circuit on the semiconductor substrate. 2. The multi-axis force sensor according to claim 1, wherein the sensor can be connected to an external signal processing circuit. 3. A step of forming a silicon nitride film on a first surface of a P-type silicon substrate so as to surround a portion corresponding to a sensor region formed on a second surface; Forming a deep N-type diffusion layer in a region where an external lead portion is formed; forming an N-type diffusion layer shallower than the deep diffusion layer in a region where a connection portion is formed; Forming a strain detection element; sequentially forming a lower polyimide film, an aluminum wiring layer and an upper polyimide film on the silicon substrate; and forming the deep N-type diffusion layer and the shallow surface from a first surface of the silicon substrate. Electrochemically etching the silicon substrate with an aqueous solution of potassium hydroxide while applying a positive voltage to the diffusion layer.