JP4040435B2 - Silicon tactile sensor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tactile sensor used in various advanced robot technologies that require delicate fingertip operations, and in particular, is formed on a silicon substrate by silicon integrated circuit technology, micromachining, etc., and detects the shape of a contact object, etc. The present invention relates to a silicon tactile sensor device used for the above.
[0002]
[Prior art]
Conventionally, as a tactile sensing element (sensor) for detecting the surface shape of an object, a small conductive pressure sensor formed using a conductive sheet made of rubber (pressure-sensitive conductive rubber) whose electrical resistance changes or a semiconductor micromachine is used. Or, many force sensors are arranged to detect the pressure distribution at the time of contact. For example, (1) conventional examples using pressure-sensitive conductive rubber [Non-patent Documents 1 and 2], (2) a minute pressure sensor Examples include the conventional example [Non-Patent Document 3] arranged, and (3) the conventional example [Non-Patent Documents 4 and 5] in which minute force sensors are arranged.
[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, and uses a change in electrical resistance at a contact portion as a signal. That is, a change in electrical resistance at a site that has received a strong pressure is captured as a signal, and a force distribution on the sensor is detected. Although this method allows the sensor to be deformed to some extent and can accept the pressure, the pressure detection resolution is low. Further, since the number of wires increases as the number of electrodes increases, the number of electrodes cannot be increased to a certain extent, and information obtained is limited. Therefore, a very detailed shape cannot be detected. Further, since the pixels are coupled to each other with low resistance due to the lateral conductivity of the pressure-sensitive conductive rubber 102, increasing the resolution by reducing the interval between the pixels becomes a problem in detection accuracy.
[0004]
As shown in FIG. 6 (FIG. 6A is a top view of a sensor having a pressure sensor array and FIG. 6B is a cross-sectional view of a pressure sensor section), 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 Is an Al wiring, 220 is a minute diaphragm pressure sensor, 221 is a diaphragm, 222 is an etching hole, and 223 is a cavity.
[0005]
As described above, 1024 minute diaphragm pressure sensors 220 formed by micromachining are incorporated in the peripheral circuit of the CMOS integrated circuit 210. Unlike the case of the conventional example (1), this sensor can read many sensor signals from the outside with a small number of wires by the peripheral signal processing circuit 230. Further, by using micromachining, the size per element can be reduced, and higher resolution can be realized.
[0006]
However, the pressure distribution is obtained only when the diaphragm 221 is recessed from 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 more easily depressed than the surface of the silicon chip 200. As a result.
[0007]
In addition, when many pressure sensors are integrated, the area required to form the diaphragm is considerably larger than that of the strain detection element. This is because it is necessary to form a structure having a certain size in order to generate a strain that can be sufficiently detected even with a minute mechanical structure. Therefore, the formable size of the diaphragm determines the area of one pixel, and as a result, becomes 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, reads force signals added from the respective shape changes, and obtains 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), the load acceptance points (Load Accepting Points) 304 protrude most from the chip surface, so that direct contact sense information can be detected on the surface of the silicon chip 300. However, it is the same as the conventional example (2) in that the structure of one pixel forms one mechanical structure, and it is necessary to have a certain size for detecting 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, 301 is the upper surface side of the silicon chip 300, 302 is a groove, 303 is a sensing element, 305 is the lower surface side of the silicon chip 300, and 306 is a through hole.
[0010]
Next, in addition to the conventional examples (1) to (3), the conventional example (4) will be described.
[0011]
As shown in FIG. 8 (FIG. 8A is a top view of the tactile sensor and FIG. 8B is a circuit configuration diagram of the force detection 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 the surface pressure distribution [Non-patent Document 4]. It is the ferroelectric thin film 402 that converts the input force into an electric signal, and this part has a higher resolution in that the size per pixel can be reduced compared to the above three conventional examples. This is an advantageous configuration.
[0012]
However, all the detection portions are arranged on a hard silicon chip, and it is necessary for the contact target side to be responsible for deformation when detecting the surface pressure distribution. In addition, since the measurement object is in direct contact with the circuit surface, it is necessary to form a protective film such as elastic rubber as in the conventional example (2) in order to prevent physical damage. It becomes difficult.
[0013]
In FIG. 8, the force input to the sensor element is detected by detecting changes in the MOS 403 connected to the power supply V _DD and the ferroelectric thin film capacitor 404 connected to the gate electrode thereof.
[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 Ryoji Ohba, Ohmsha, 1990 (Intelligent & Control Series) pp. 84-85
[0017]
[Non-Patent Document 2]
Compute No. 21 Corona pp. 59-66
[0018]
[Non-Patent Document 3]
IEICE Transactions C-II Vol. J74-C-II No. 5 pp. 411-420
[0019]
[Non-Patent Document 4]
Proceedings of the Japan Society of Mechanical Engineers Robotics and Mechatronics Vol. 1990-A pp. 361-366 1990
[0020]
[Non-Patent Document 5]
IEDM 85 pp. 133-136
[0021]
[Problems to be solved by the invention]
As described above, the conventional examples (1) to (4) have their respective problems and are not technically satisfactory.
[0022]
A first object of the present invention is to provide a tactile sensor having higher resolution by removing the restriction that determines the minimum size of the strain detection pixels. 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 to form the strain detection pixels, and it is necessary to cover the element surface with a protective material such as elastic rubber. At present, these matters are the main factors for the low resolution of the tactile sensor compared to the optical image sensor, and are important issues to be solved. Therefore, the pixel size of the tactile sensor can be reduced by the present invention, and the position detection resolution is greatly improved by realizing a sensor that can directly contact the object without using a protective material such as elastic rubber on the surface. A tactile sensor can be realized.
[0023]
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 relatively strong force. In particular, the range of forces that can be received by delicate mechanical structures and integrated circuit surfaces is narrowly limited, and the range of forces that can be input is determined by the designed sensor structure, so that it is possible to handle a wide range of inputs. A sensor is needed. 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, according to the present invention, a new tactile sensor that operates in accordance with a wide range of inputs can be realized by appropriately changing the “hardness” of the tactile sensor structure in accordance with the input force range. The hardness of the sensor may be controlled according to the input, or the setting may be changed each time if a certain degree of prediction can be made.
[0024]
A third object of the present invention is to provide a new function composite type tactile sensor capable of detecting various information such as a fingertip of a human body. In the conventional tactile sensor, the obtained information is limited to only the tactile information such as the surface pressure distribution and the surface shape. However, in the present invention, various information other than the surface shape is obtained simultaneously as the information on the measurement surface. This makes it possible to operate delicate objects that cannot be handled by conventional tactile sensors. That is, by incorporating necessary sensors / actuators other than for shape recognition and their signal processing functions, various information such as temperature, humidity, surface friction, and hardness of the contact target can be obtained from the tactile sensor.
[0025]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides
[1] In a silicon tactile sensor device, a thin silicon diaphragm, a semiconductor strain detecting element array disposed below the thin silicon diaphragm, a signal processing circuit integrated around the semiconductor strain detecting element array, A gas pressure chamber that is disposed under the thin silicon diaphragm and that defines a movable gap that faces the semiconductor strain sensing element array , and a pressure adjusting hole that communicates with the gas pressure chamber and adjusts the pressure of the movable gap. The thin silicon diaphragm is deformed in accordance with the shape of the object to be contacted, and the deformation of the thin silicon diaphragm is electrically detected by signal processing of the signal processing circuit. And
[0026]
[ 2 ] The silicon tactile sensor device according to [1], wherein sensors for measuring temperature and thermal conductivity are further integrated to process the information.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0028]
FIG. 1 is a perspective view showing the overall configuration of a high resolution tactile sensor showing an embodiment of the present invention, FIG. 2 is a diagram showing a layout of the 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 sectional view showing a measurement state of a contact object of the high resolution touch sensor according to the embodiment of the present invention.
[0029]
In these drawings, 1 is a supporting substrate, 2 is a thin silicon diaphragm, 3 is a semiconductor strain detecting element array disposed below the thin silicon diaphragm 2, 3A is a semiconductor strain detecting element, and 4 is this semiconductor strain detecting element array. 3 is a signal processing circuit integrated in the periphery of 3, 5 is an electrode, 6 is a connection line, and 7 is defined so that the semiconductor strain detecting element array 3 faces (facing) on the back side of the thin silicon diaphragm 2. The movable gap (gas pressure chamber), 8 is a measurement object, and 9 is a connection terminal.
[0030]
As shown in FIG. 4, the thin silicon diaphragm 2 is deformed in accordance with the shape of the object 8 to be contacted, and the deformation of the shape of the thin silicon diaphragm 2 is electrically detected by signal processing of the signal processing circuit 4. It is configured.
[0031]
The thin silicon diaphragm 2 is made of an ultrathin silicon single crystal having a thickness of about 10 μm, and a semiconductor strain detection element 3A for detecting the shape (a heater element, a temperature sensor, etc. can also be mounted) on the back surface thereof is high density. They are integrated in an array. The output signal of each strain gauge is switched by the integrated signal processing circuit 4, signal-processed and taken out to the outside. The integrated semiconductor strain detection element array 3 and the signal processing circuit 4 are formed by a general silicon integrated circuit technology, and thin film processing (for example, chemical mechanical polishing (CMP), etc.) is performed on the completed wafer. , Processed to a thickness sufficiently thin to deform.
[0032]
FIG. 2 shows a design example of such a silicon surface element, in which an element arrangement independent of the mechanical structure is made. Here, the number of integrated elements is 6 × 6, 36, and the pixel interval is determined by the minimum processable dimension of the semiconductor element. The size necessary for forming the detection pixel depends only on the semiconductor processing technology, and can be further reduced in size and the number of pixels can be increased by a more precise processing technology.
[0033]
In FIG. 3, a piezoresistor using an n-type diffused resistor is formed here as the semiconductor strain detecting element 3A. Four longitudinal piezoresistors 11, 12, 13, and 14 and four lateral piezoresistors 15, 16, 17, and 18 are provided so that the longitudinal and lateral strains generated on the silicon chip surface can be detected effectively. Each pixel is formed.
[0034]
In this embodiment, only the semiconductor strain detection element 3A is integrated. However, in addition to the semiconductor strain detection element 3A, a heater element and a temperature sensor element can be easily integrated by integrated circuit technology.
[0035]
Prior to the thinning process of the silicon portion, a support substrate (such as glass) 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 such a configuration, the sensor can have a strength that can sufficiently withstand the external force applied to the thinning process. It can also be used as the final package of the sensor or a part thereof. In this manufacturing method, it is possible to form a sensor structure that is thin enough to be deformed in conformity with the surface shape while using standard integrated circuit technology. In addition, since the substrate has sufficient strength, it is a manufacturing method that can sufficiently withstand the mass production process.
[0036]
In FIG. 4, the thin silicon diaphragm 2 contacts the measurement object 8, 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 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.
[0037]
In the high resolution tactile sensor of the present invention, the information on the unevenness of the shape is restored by integrating the information on the distortion in each pixel, and the surface shape (height) information on the basis of the movable part end face (silicon diaphragm) of this sensor. Makes it 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. Furthermore, although the pressure of the gas pressure chamber 7 is not shown, the pressure can be changed or controlled from the outside through a pressure adjustment hole communicating with the gas pressure chamber 7, so that the external force of various magnitudes can be obtained as described above. A high-resolution tactile sensor that can be adapted to the above can be realized.
[0038]
By the detection method as described above, the pixel area can be reduced to about 1/10 to 1/100 or less of the prior art at the present time. Therefore, in the future, it is possible to improve the detection position resolution of this high resolution tactile sensor by two digits or more. Since the pixel area can be reduced with the miniaturization of semiconductor manufacturing technology, the difference from the conventional technology is expected to increase more and more in the future.
[0039]
Furthermore, as described above, the shape information of the measurement object that is in contact is measured by the strain detection element, but the signal processing / control circuit includes various sensors and actuators such as a humidity sensor, heater, and temperature sensor on the surface of the sensor chip. By integrating together, it is possible to obtain information such as temperature, thermal conductivity, humidity, surface friction coefficient, and hardness of the contact object in addition to the shape.
[0040]
For example, it is possible to know the surface temperature distribution of the measurement object with an integrated temperature sensor. For example, it is possible to investigate the thermal conductivity of the surface by measuring the transient characteristics during heating of one heater element arranged in an array or on the surface, and feel the coldness etc. when touching the object. 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 detecting the normal force applied to the object and the slip amount of the surface, and information on slipperiness can be obtained.
[0041]
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 enables high-density integration, high functionality and high resolution close to those of the human fingertip. The silicon tactile sensor can be realized.
[0042]
If sensors capable of obtaining various tactile sensation information instead of human fingertips are put into practical use, it becomes possible for the robot to know sensory information similar to that of human fingertips. In the future, a robot that provides care directly touching a human needs to understand the temperature and state of the other party by touching the fingertip. By effectively using this high-resolution tactile sensor for robot motion control, it is possible to put to practical use a “human-friendly” nursing robot with more human-like behavior.
[0043]
In addition, this invention is not limited to the said Example, A various deformation | transformation is possible based on the meaning of this invention, and these are not excluded from the scope of the present invention.
[0044]
【The invention's effect】
As described above in detail, according to the present invention, the following effects can be obtained.
[0045]
(A) The shape of the contact object can be detected with high precision.
[0046]
(B) Since the entire high-density strain detection array circuit formed by the integrated circuit technology is processed into a single ultrathin silicon diaphragm shape 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 at a high resolution that has not been achieved conventionally.
[0047]
(C) By making the contact portion with the object the lower part (rear surface) of the thinned silicon chip, contact / shape detection with the object can be performed without forming a special protective film or the like on the surface of the integrated circuit. It becomes possible.
[0048]
(D) By pressurizing a gas pressure chamber as a movable gap to the diaphragm structure with air or the like, the diaphragm can be kept in a curved state protruding from a plane. Thereby, it can be in the state suitable for contact with an object. In addition, by appropriately controlling or setting the pressure from the outside, it is possible to arbitrarily determine the measurement range of the sensor in accordance with the force applied by the contacting object.
[0049]
(E) Furthermore, by utilizing the feature of this sensor that it is easy to integrate and integrate, various sensors that measure temperature, thermal conductivity, etc. and the processing circuit that implements the algorithm are the same. The information can be integrated into parts and processed. This makes it possible to realize a silicon tactile sensor that can know the shape, temperature, coolness, coefficient of friction, and hardness, similar 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 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.
FIG. 3 is a diagram showing a layout of strain detection elements per pixel of a high resolution tactile sensor showing an embodiment of the present invention.
FIG. 4 is a cross-sectional view illustrating a measurement state of a contact object 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 view showing a pressure sensor array in which conventional minute diaphragm structures are integrated.
FIG. 7 is a diagram showing a tactile sensor in which conventional micro force sensors are integrated.
FIG. 8 is a diagram showing a conventional tactile sensor using a minute ferroelectric film.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Support substrate 2 Thin silicon diaphragm 3 Semiconductor strain detection element array 3A Semiconductor strain detection element 4 Signal processing circuit 5 Electrode 6 Connection line 7 Movable gap (gas pressure chamber)
8 Measurement object 9 Connection terminal 11, 12, 13, 14 Vertical piezoresistance 15, 16, 17, 18 Horizontal piezoresistance

Claims (2)

(A) a thin silicon diaphragm;
(B) a semiconductor strain sensing element array disposed below the thin silicon diaphragm;
(C) a signal processing circuit integrated around the semiconductor strain sensing element array;
(D) a gas pressure chamber in which a movable gap facing the semiconductor strain sensing element array disposed below the thin silicon diaphragm is defined ;
(E) a support substrate communicating with the gas pressure chamber and having a pressure adjusting hole for adjusting the pressure of the movable gap ;
(F) A silicon tactile sensation characterized in that the thin silicon diaphragm is deformed in accordance with the shape of an object to be contacted, and the deformation of the thin silicon diaphragm is electrically detected by signal processing of the signal processing circuit. Sensor device. In the silicon tactile sensor device according to claim 1, further temperature sensors for measuring the thermal conductivity integrated, silicon tactile sensor device, characterized in that the process that information.

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