JP2004163166A - Silicon tactile sensor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized tactile sensor device having higher resolution. <P>SOLUTION: The silicon tactile sensor device is provided with a thin silicon diaphragm 2, a semiconductor distortion sensitive element array 3 arranged in a lower part of the diaphragm 2, a signal processing circuit 4 integrated around the array 3, a movable gap 7 which is arranged in the lower part of the diaphragm 2 and face the array 3, and a support substrate 1 by which the gap 7 is defined. The diaphragm 2 deforms according to the form of an object 8 to be measured. Mutation of the form of the diaphragm 2 is electrically detected by signal processing of the processing circuit 4. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a tactile sensor used in various advanced robot technologies requiring a delicate operation of a fingertip, and in particular, is formed on a silicon substrate by silicon integrated circuit technology or micromachining, and detects the shape of a contact object. The present invention relates to a silicon tactile sensor device used for a device.
[0002]
[Prior art]
Conventionally, as a tactile sensing element (sensor) for detecting the surface shape or the like of an object, a rubber conductive sheet (pressure-sensitive conductive rubber) whose electric resistance changes, or a minute pressure sensor formed by a semiconductor micromachine Or, there are many sensors that detect pressure distribution at the time of contact by arranging force sensors. For example, (1) Conventional examples using pressure-sensitive conductive rubber [Non-Patent Documents 1 and 2] and (2) Micro pressure sensor There are examples such as a conventional example [Non-Patent Document 3] arranged side by side and (3) a conventional example [Non-Patent Documents 4 and 5] arranged small force sensors.
[0003]
As shown in FIG. 5, the tactile sensor of the conventional example (1) uses a pressure-sensitive conductive rubber 102 sandwiched between a PET film 101 and an electrode pattern 103 to use a change in electric resistance at a contact portion as a signal. That is, a change in the electric resistance of a portion that is strongly subjected to pressure is captured as a signal, and a force distribution on the sensor is detected. Although this method allows the sensor to deform to some extent and can receive pressure, the resolution of pressure detection is low. Further, as the number of electrodes increases, the number of wirings becomes enormous, so that the number of electrodes cannot be increased to a certain degree or more, and the information obtained is limited. Therefore, a very detailed shape cannot be detected. In addition, since the pixels are coupled with low resistance by the lateral conductivity of the pressure-sensitive conductive rubber 102, reducing the interval between the pixels to increase the resolution poses a problem in detection accuracy.
[0004]
As shown in FIG. 6 (FIG. 6 (a) is a top view of a sensor having a pressure sensor array, and FIG. 6 (b) is a cross-sectional view of a pressure sensor unit), the pressure sensor array of the conventional example (2) is silicon micromachining. The micro-diaphragm pressure sensor 220 formed by the above is arranged on the silicon chip 200. 210 is a CMOS integrated circuit, 211 is a silicon substrate, 212 is a p-well, 213 is an n-well, 214 is a field oxide film, 215 is a PGS film, 216 is a gate oxide film, 217 is a polycrystalline silicon gate, 218 Denotes an Al wiring, 220 denotes a minute diaphragm pressure sensor, 221 denotes a diaphragm, 222 denotes an etching hole, and 223 denotes a cavity.
[0005]
As described above, 1024 micro-diaphragm pressure sensors 220 formed by micromachining are incorporated in the peripheral circuit of the CMOS integrated circuit 210. This sensor is different from the conventional example (1) in that the peripheral signal processing circuit 230 can read many sensor signals from outside with a small number of wires. Further, by using micromachining, the size per element can be reduced, and higher resolution can be realized.
[0006]
However, a pressure distribution is obtained only when the diaphragm 221 is depressed below the surface of the silicon chip 200. Therefore, when used as a tactile sensor, the surface of the very “hard” silicon chip 200 is covered with elastic rubber or the like, so that the diaphragm 221 is configured to be more easily depressed than the surface of the silicon chip 200, and the accuracy of the positional resolution originally possessed by the sensor is obtained. As a result.
[0007]
Further, when many pressure sensors are integrated, a large area is required for forming a diaphragm as compared with a strain detecting element. This is because it is necessary to form a structure having a certain size in order to generate a sufficiently detectable distortion even with a minute mechanical structure. Therefore, the formable size of the diaphragm determines the area of one pixel, and as a result, there is a limitation in increasing the resolution.
[0008]
As shown in FIG. 7, the silicon tactile sensor of the conventional example (3) forms a large number of minute structures by a micromachine and reads out a force signal applied from each shape change to obtain a tactile surface distribution. . This sensor is also advantageous in that the base material is silicon and the peripheral circuit can be formed on the same substrate.
[0009]
In the method of the conventional example (3), unlike the conventional example (2), since the load accepting points (Load Accepting Points) 304 protrude most from the chip surface, it is possible to detect the direct contact sense information on the surface of the silicon chip 300. However, the structure of one pixel is the same as the conventional example (2) in that each mechanical structure is formed, and it is necessary to have a certain size in order to detect distortion. Therefore, since the size of one pixel is relatively large, it is difficult to improve the position resolution of the sensor. In FIG. 7, reference numeral 301 denotes an upper surface side of the silicon chip 300, 302 denotes a groove, 303 denotes a sensing element, 305 denotes a lower surface side of the silicon chip 300, and 306 denotes a through hole.
[0010]
Next, a conventional example (4) will be described in addition to the above-described conventional examples (1) to (3).
[0011]
As shown in FIG. 8 (FIG. 8 (a) is a top view of the tactile sensor, and FIG. 8 (b) is a circuit configuration diagram of the force detecting unit) of the tactile sensor 400 of the conventional example (4), as shown in FIG. The body thin film 402 is integrated with the MOS integrated circuit 401 to detect a surface pressure distribution [Non-Patent Document 4]. It is the ferroelectric thin film 402 that converts the input force into an electric signal. This portion can be reduced in size per pixel as compared with the three conventional examples described above, and is used for high resolution. This is an advantageous configuration.
[0012]
However, all the detection parts are arranged on a hard silicon chip, and it is necessary for the contact target side to be entirely deformed in order to detect the surface pressure distribution. In addition, since the measurement target is in direct contact with the circuit surface, it is necessary to form a protective film such as an elastic rubber in order to prevent physical damage as in the conventional example (2). It will be difficult.
[0013]
In FIG. 8, the detection of the force input to the sensor element is performed by detecting a change in the MOS 403 connected to the power supply _VDD and a change in the capacitor 404 of the ferroelectric thin film connected to the gate electrode.
[0014]
[Patent Document 1]
JP-A-11-125570, page 2-3 [Patent Document 2]
JP-A-8-37314, page 2-3 [Non-Patent Document 1]
Intelligent Sensor Technology, edited by Ryoji Ohba, Ohmsha, 1990 (Intelligent & Control Series) pp. 84-85
[Non-patent document 2]
Computer No. 21 Corona pp. 59-66
[Non-Patent Document 3]
IEICE Transactions C-II Vol. J74-C-II No. 5 pp. 411-420
[Non-patent document 4]
Proceedings of the Robotics and Mechatronics Conference of the Japan Society of Mechanical Engineers Vol. 1990-A pp. 361-366 1990
[Non-Patent Document 5]
IEDM 85 pp. 133-136
[0015]
[Problems to be solved by the invention]
As described above, each of the conventional examples (1) to (4) has a problem and is not technically satisfactory.
[0016]
It is a first object of the present invention to provide a tactile sensor having higher resolution by removing the restriction that determines the minimum size of a distortion detection pixel. In other words, each of the above four conventional examples has technical limitations in reducing the size of one pixel and improving the position detection resolution of the tactile sensor. This is because a relatively large area is required for forming the strain detection pixel, and the element surface needs to be covered with a protective material such as elastic rubber. At present, these matters are the main factors that make the tactile sensor lower in resolution compared to the optical image sensor, and are important issues to be solved. Accordingly, the present invention has made it possible to reduce the pixel size of the tactile sensor and realize a sensor that can directly contact an object without using a protective material such as an elastic rubber on the surface, thereby dramatically improving the position detection resolution. A tactile sensor can be realized.
[0017]
A second object of the present invention is to provide a tactile sensor that can be used in a wide input range from a weak force to a case where a relatively strong force is applied. In particular, the range of force that can be received by delicate mechanical structures and integrated circuit surfaces is narrowly limited, and the range of force that can be input is determined by the designed sensor structure, so haptic sense that can respond to a wide range of input There is a need for sensors. In the conventional tactile sensor, the lower limit and the upper limit of the tactile input signal that can be detected when the sensor is completed are almost determined. On the other hand, in the present invention, a new tactile sensor that operates in response to a wide range of input can be realized by appropriately changing the “hardness” of the tactile sensor structure according to the range of the input force. The stiffness of the sensor may be controlled according to the input, or the setting may be changed each time it can be predicted to some extent.
[0018]
A third object of the present invention is to provide a new function-combination type tactile sensor capable of detecting various information like a fingertip of a human body. In the conventional tactile sensor, information obtained is limited to only tactile information such as surface pressure distribution and surface shape. In the present invention, various information other than the surface shape is simultaneously obtained as information on the measurement surface. Thus, it is possible to operate a delicate object that cannot be handled by a conventional tactile sensor. That is, by incorporating necessary sensors / actuators other than those for shape recognition and their signal processing functions, various kinds of information such as temperature, humidity, surface friction, and hardness of the contact target can be obtained from the tactile sensor.
[0019]
[Means for Solving the Problems]
The present invention, in order to achieve the above-mentioned object,
[1] In a silicon tactile sensor device, a thin silicon diaphragm, a semiconductor strain detecting element array arranged below the thin silicon diaphragm, a signal processing circuit integrated around the semiconductor strain detecting element array, A movable gap disposed below the thin silicon diaphragm and facing the semiconductor strain detection element array, and a supporting substrate on which the movable gap is defined, wherein the thin silicon diaphragm is adapted to the shape of the contacted measuring object. The thin silicon diaphragm is deformed, and the deformation of the shape of the thin silicon diaphragm is electrically detected by signal processing of the signal processing circuit.
[0020]
[2] In the silicon tactile sensor device according to the above [1], the support substrate has a pressure adjusting hole for adjusting the pressure of the movable gap.
[0021]
[3] The silicon tactile sensor device according to [1], wherein sensors for measuring temperature, thermal conductivity, and the like are further integrated, and the information is processed.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0023]
FIG. 1 is a perspective view showing an overall configuration of a high-resolution tactile sensor showing an embodiment of the present invention, FIG. 2 is a diagram showing a layout of a high-resolution tactile sensor showing an embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a diagram showing a layout of a strain detecting element per pixel of the high-resolution tactile sensor, and FIG. 4 is a cross-sectional view showing a measurement state of a contact target of the high-resolution tactile sensor according to the embodiment of the present invention.
[0024]
In these figures, 1 is a support substrate, 2 is a thin silicon diaphragm, 3 is a semiconductor strain detecting element array arranged below the thin silicon diaphragm 2, 3A is a semiconductor strain detecting element, 4 is this semiconductor strain detecting element array. A signal processing circuit integrated around 3 is formed, 5 is an electrode, 6 is a connecting line, 7 is defined on the back side of the thin silicon diaphragm 2 so that the semiconductor strain detecting element array 3 faces (faces). A movable gap (gas pressure chamber), 8 is an object to be measured, and 9 is a connection terminal.
[0025]
As shown in FIG. 4, the thin silicon diaphragm 2 is deformed according to the shape of the measuring object 8 in contact with the thin silicon diaphragm 2, and the deformation of the shape of the thin silicon diaphragm 2 is electrically detected by the signal processing of the signal processing circuit 4. It is composed.
[0026]
The thin silicon diaphragm 2 is made of an ultra-thin silicon single crystal having a thickness of about 10 μm, and a semiconductor strain detecting element 3A for shape detection (a heater element, a temperature sensor, and the like can also be mounted thereon) has a high density on the back surface. They are integrated in an array. The output signal of each strain gauge is switched by the integrated signal processing circuit 4, processed, and taken out. The integrated semiconductor strain detecting element array 3 and the signal processing circuit 4 are formed by a general silicon integrated circuit technique, and thinned (for example, chemical mechanical polishing (CMP) or the like) on a completed wafer. , Processed to a thickness that is thin enough to deform.
[0027]
FIG. 2 shows a design example of such a silicon surface element, in which the element arrangement is independent of the mechanical structure. Here, the number of integrated elements is 36 (6 × 6), and the pixel interval is determined by the minimum processable size of the semiconductor element. The size required for forming the detection pixels depends only on the semiconductor processing technology, and it is possible to reduce the size and increase the number of pixels with a more precise processing technology.
[0028]
In FIG. 3, a piezoresistor using an n-type diffused resistor is formed here as the semiconductor strain detecting element 3A. Four piezoresistors 11, 12, 13, and 14 in the vertical direction and four piezoresistors 15, 16, 17, 18 in the horizontal direction are provided so as to effectively detect vertical and horizontal strains generated on the surface of the silicon chip. It is formed for each pixel.
[0029]
In this embodiment, only the semiconductor strain detecting element 3A is integrated, but in addition to the semiconductor strain detecting element 3A, a heater element and a temperature sensor element can be easily integrated by an integrated circuit technique.
[0030]
Prior to the step of thinning the silicon portion, a support substrate (glass or the like) processed so that the contact surface is movable to some extent is bonded to the circuit surface side of the thin silicon diaphragm 2. With this configuration, the sensor can have sufficient strength to withstand the external force applied to the thinning process. Further, this can be used as a final package of the sensor or a part thereof. With this manufacturing method, it is possible to form a sensor structure that is thin enough to be deformable in conformity with the surface shape using standard integrated circuit technology. In addition, since the substrate has sufficient strength, the manufacturing method can sufficiently endure the mass production process.
[0031]
In FIG. 4, the thin silicon diaphragm 2 comes into contact with the object 8 to be measured, and the surface of the thin diaphragm 2 is deformed along the surface shape. Since the semiconductor strain detecting element 3A formed on the back surface of the thin silicon diaphragm 2 only has the strain information of the contact portion, it is necessary to restore the surface shape information by appropriate signal processing from the signal processing circuit 4. is there.
[0032]
In the high-resolution tactile sensor of the present invention, the information on the distortion of each pixel is integrated to restore the information on the shape irregularity, and the surface shape (height) information based on the end surface (silicon diaphragm) of the movable part of the sensor is used. It is possible to obtain. If the magnitude of the entire force input to the entire sensor can be known by some method, it can be converted into a pressure distribution for each pixel. Further, the pressure of the gas pressure chamber 7 is not shown, but can be changed or controlled from the outside through a pressure adjusting hole communicating with the gas pressure chamber 7 so that the external force of various magnitudes can be reduced as described above. A high-resolution tactile sensor adaptable to the above can be realized.
[0033]
With the above-described detection method, it is possible to reduce the pixel area to approximately 1/10 to 1/100 or less of the conventional technology at the present time. Therefore, it is possible to improve the detection position resolution of the high-resolution tactile sensor by two digits or more in the future. Since the pixel area can be reduced with the miniaturization of semiconductor manufacturing technology, it is expected that the difference from the conventional technology will be further widened in the future.
[0034]
Furthermore, as described above, the shape information of the measuring object in contact is measured by the strain detecting element, but various sensors and actuators such as a humidity sensor, a heater, and a temperature sensor are mounted on the surface of the sensor chip by a signal processing / control circuit. In addition, information such as temperature, heat conductivity, humidity, surface friction coefficient, and hardness of the contact target can be obtained in addition to the shape.
[0035]
For example, the surface temperature distribution of the measurement object can be known by the integrated temperature sensor. For example, by measuring the transient characteristics during heating of one or an array of heater elements on the surface, the thermal conductivity of the surface can be examined, and the sense of cold, etc. felt when touching an object can be measured. It can be obtained numerically. Further, by analyzing the time series data of the normal force and the surface shape change when the sensor is pressed against the object, the hardness of the object can be known. Further, the degree of the surface friction coefficient can be calculated from the result of detection of the normal force applied to the object and the amount of surface slip, and information on the slipperiness can be obtained.
[0036]
These are basically the same information that can be obtained when manipulating an object with a fingertip, and by taking advantage of the features of the present invention that enable high-density integration, high functionality and high resolution similar to those of a human fingertip Silicon tactile sensor can be realized.
[0037]
If a sensor that can obtain various tactile sensation information in place of a human fingertip is put into practical use, the robot can know the same sensory information as a human fingertip. In the future, a nursing care robot that directly touches a human needs to understand the body temperature and body state of the other party by touching the fingertip. By effectively utilizing this high-resolution tactile sensor for robot motion control, a "human-friendly" care robot with more human-like behavior can be put to practical use.
[0038]
It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.
[0039]
【The invention's effect】
As described above in detail, according to the present invention, the following effects can be obtained.
[0040]
(A) The shape of the contact object can be detected with high precision.
[0041]
(B) Since the entire high-density strain detection array circuit formed by the integrated circuit technology is processed into a single ultra-thin silicon diaphragm and its own deformation is used for shape recognition, the consistency with the integrated circuit technology is high. In addition, tactile information can be detected with a higher resolution than ever before.
[0042]
(C) By making the contact portion with the object the lower portion (back surface) of the thinned silicon chip, it is possible to detect contact and shape with the object without forming a special protective film or the like on the integrated circuit surface. It becomes possible.
[0043]
(D) By pressurizing a gas pressure chamber as a movable gap in the diaphragm structure with air or the like, the diaphragm can be kept in a curved state protruding from a plane. Thereby, a state suitable for contact with the object can be obtained. Also, by appropriately controlling or setting this pressure from the outside, it becomes possible to arbitrarily determine the measurement range of the sensor in accordance with the force given by the contacting object.
[0044]
(E) Furthermore, utilizing the features of this sensor that the circuit is easily integrated and integrated, various sensors for measuring temperature, thermal conductivity, etc., and a processing circuit for realizing the algorithm are the same. It can be integrated into parts and process that information. This makes it possible to realize a silicon tactile sensor capable of knowing the shape, temperature, cold / hot feeling, friction coefficient, and hardness similarly to a human fingertip.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an overall configuration of a high-resolution tactile sensor according to an embodiment of the present invention.
FIG. 2 is a diagram showing a layout of a high-resolution tactile sensor according to an embodiment of the present invention.
FIG. 3 is a diagram showing a layout of a distortion detecting element per pixel of the high-resolution tactile sensor according to the embodiment of the present invention.
FIG. 4 is a cross-sectional view illustrating a measurement state of a contact target of the high-resolution tactile sensor according to the embodiment of the present invention.
FIG. 5 is a diagram showing a tactile sensor using a conventional pressure-sensitive conductive rubber.
FIG. 6 is a diagram showing a conventional pressure sensor array in which a minute diaphragm structure is integrated.
FIG. 7 is a diagram showing a tactile sensor in which a conventional minute force sensor is integrated.
FIG. 8 is a diagram showing a tactile sensor using a conventional minute ferroelectric film.
[Explanation of symbols]
Reference Signs List 1 support substrate 2 thin silicon diaphragm 3 semiconductor strain detecting element array 3A semiconductor strain detecting element 4 signal processing circuit 5 electrode 6 connection line 7 movable gap (gas pressure chamber)
8 Measurement object 9 Connection terminals 11, 12, 13, 14 Vertical piezoresistors 15, 16, 17, 18 Horizontal piezoresistors

Claims (3)

(A) a thin silicon diaphragm;
(B) a semiconductor strain detecting element array disposed below the thin silicon diaphragm;
(C) a signal processing circuit integrated around the semiconductor strain detecting element array;
(D) a movable gap facing the semiconductor strain detecting element array disposed below the thin silicon diaphragm;
(E) a supporting substrate on which the movable gap is defined;
(F) the thin silicon diaphragm is deformed in accordance with the shape of the object to be contacted, and the deformation of the shape of the thin silicon diaphragm is electrically detected by signal processing of the signal processing circuit. Sensor device. 2. The silicon tactile sensor device according to claim 1, wherein the support substrate has a pressure adjusting hole for adjusting the pressure of the movable gap. 2. The silicon tactile sensor device according to claim 1, wherein sensors for measuring temperature, thermal conductivity, and the like are further integrated, and the information is processed.

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