JPH0564863B2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention is a device that can be attached to a robot's hand, etc., to detect the repulsive force or slip sensation when grasping an object, or to measure the distribution of pressure sensation. The present invention relates to the structure of a force sensor and its manufacturing method.

(Prior Art) In recent years, inexpensive and high-performance microcomputers have become widespread, and by using them, automation or robotization is progressing in various industrial fields. However, robots that are currently in practical use can only lift or carry objects of a certain size or weight, or perform tasks such as processing or assembly, only according to a certain program. The current situation is that it is possible. On the other hand, due to the diversification of consumer groups, there is a growing trend towards high-mix, low-volume production.
There is a call for the development of an automation technology called FMS (Flexible Manufacturing System). In this trend of automation, robots and machines are equipped with various sensors that replace human sense organs.
It is necessary to have intelligent robots or machines themselves make decisions. For example, when a robot picks up an object, it first finds the object using a visual sensor, approaches the object using a proximity sensor, and touches the object.

The tactile sensor first detects whether the object has been touched.
Detect ON-OFF information. Next, grasp the object and measure the repulsive force from the object to determine whether the object is hard or soft. Then, the robot moves on to lifting the object, but at that time, it is necessary to accurately judge whether the object is slippery or not. In other words, the functions necessary for a tactile sensor include a tactile sense to determine whether something has been touched, a pressure sense to determine the strength of gripping an object, and a sliding sense to determine whether the object is slippery. As described above, the functions of tactile sensors required for robots are wide-ranging, and their necessity is strongly recognized. However, at present, a sensor that satisfies all of the above functions has not been realized, and only each individual function is satisfied. For example, “Automation Technology” magazine No.
As introduced in Vol. 14, No. 6, pages 37 to 42 and pages 61 to 70, there are various types such as those using conductive rubber, those using microswitches, and those using carbon fiber. These tactile sensors have drawbacks such as being too large or having poor linearity in reproducibility, but all of them have a single function. In other words, only distributed pressure or ON-OFF
Only etc. Recently, a method has been proposed in which pressure-sensitive materials are attached directly to a silicon IC and signal processing is performed on the IC to detect distributed pressure and slip sensation using software. (Proceedings of the 12th International Symposium on Industrial Robotics (Proceedings.12th ISIR), 1982, pp. 417-425.
page).

(Problems to be solved by the invention) As mentioned above, the functions of tactile sensors required for robots include tactile sense, pressure sense, and sliding sense, and with conventional technology, there is no sensor that can detect all of these functions. It had not been realized. Also
It has been reported that devices attempt to solve these problems using software by performing signal processing on an IC, but constraints on signal processing time are unavoidable.
However, in order to prevent the robot from dropping the object when it is directly grasping it, a very short processing time is required, and it is necessary to directly detect the sensation of slipping. It is an object of the present invention to provide a new structure for a force sensor and a method for manufacturing the same, which eliminates the above-mentioned drawbacks of the conventional force sensor.

(Means for Solving the Problems) The present invention provides the following features: 1. On a beam provided on a silicon semiconductor substrate and supported on at least one side, the A half-bridge or full-bridge circuit is formed by the diffused layer resistors provided symmetrically with respect to the center line in the longitudinal direction and at least one diffused layer resistor provided at the support base portion, and a half-bridge or full bridge circuit is formed in the vicinity of the support base of the beam. A half-bridge circuit is formed by the diffused layer resistors provided on both sides of the beam, or a full bridge circuit is formed by the diffused layer resistors provided on both sides and the diffused layer resistor formed on the support part. A force sensor featuring:

2. On a beam provided on a silicon semiconductor substrate and supported on at least one side, in the vicinity of at least one support part of the beam, and when viewed from above, symmetrically with respect to the center line in the longitudinal direction of the beam. A half bridge or a full bridge circuit is formed by the provided diffusion layer resistor and at least one diffusion layer resistor provided at the support base portion, and the diffusion layer resistor provided on both sides of the beam near the support base of the beam forms a half bridge or full bridge circuit. A force sensor is characterized in that a half-bridge circuit is formed, or a full-bridge circuit is formed by a diffusion layer resistor provided on both sides of the half-bridge circuit and a diffusion layer resistor formed on the support base portion, and the present structure is A force sensor characterized in that at least two sets of elements are arranged on the silicon substrate, including an element and an element of this structure rotated by approximately 90 degrees within the plane of the substrate.

3 Manufacture of a force sensor consisting of a step of forming a diffused layer resistor on a silicon semiconductor substrate, a step of forming a silicon diaphragm and protecting the diaphragm part, a step of forming a beam, and a step of connecting each diffused resistor. A method for manufacturing a force sensor, comprising the step of etching away a portion of the diffusion layer resistance to equivalently form the diffusion layer resistance at the edge of the side surface of the beam.

(Function) The present invention utilizes the piezoresistance effect of silicon,
A diffusion resistance formed in the center of a silicon beam supported on one side detects the force component perpendicular to the beam, and a diffusion layer resistance formed on both sides of the beam detects the force component parallel to the beam support. It is something to detect. Furthermore, by orienting the above-mentioned elements at 90 degrees to each other, the beam has the characteristic of being able to detect force components in three directions, including two directions perpendicular to the beam and in-plane. In addition, the manufacturing method requires three-dimensional processing to form a diffused layer resistance on both sides of the beam, but the inventor has developed a method of providing a diffused layer resistance on the surface and edge portion of the beam. discovered that the component of force in the direction parallel to the support of the beam could be measured with sufficient sensitivity.
By providing a manufacturing method in which a part of the diffusion layer resistance remains at the edge of the beam when forming the beam, three
The aim is to realize a structure that provides the same effect without dimensional processing.

(Example) The present invention will be described below based on Examples. Plan view of Figure 2 a and schematic sectional view at AB in the figure 2
As shown in Figure b, a silicon oxide film is formed by thermal oxidation on a P-type silicon substrate 201 with a plane orientation of (100) on which a high concentration P ⁺ boron layer 202 is epitaxially grown to a thickness of about 20 μm, and a diffusion layer resistor is formed. The n-type diffusion layer 20 is removed by etching and ion implantation.
3,204 is formed. Next, the oxide film on the front and back surfaces is removed, and the silicon oxide film 2 is thermally oxidized again.
05 is formed to a thickness of 1000 Å, a pattern for forming a silicon diaphragm is formed on the back side, and a silicon oxide acid is processed on the back side to open a window 209.
Next, the silicon is anisotropically etched in a 90 DEG C. hydrazine solution for about 3 hours to form a silicon diaphragm 210 as shown in FIG. 2c. At this time, the P type silicon layer 201 is etched, but the high concentration P ⁺ silicon layer 202 is not etched, and even if the etching time is slightly exceeded, the diaphragm 210 is successfully formed as shown in FIG. 2c. This is a well-known and common property when not only hydrazine but also anisotropic etching liquids such as potassium hydroxide, ethylenediamine and pyrocatechol mixtures are used. Next, a silicon oxide film 211 is deposited on the back surface to a thickness of approximately 2000 Å by CVD method to protect the exposed back silicon portion of the silicon diaphragm 210, and to form a pattern for forming beams 208 from the front surface as shown in FIG. 2d. form,
As shown in Figure 2e, the silicon oxide film is opened, the back side is protected with a resist 213 while leaving the resist 212, and a high concentration P ⁺
The silicon layer is etched to form a beam 208 with a length of 1 mm and a width of 500 μm. In the process of forming this beam, it is preferable to process the beam so that the edge of the beam is on the center line of the diffusion layer resistor 203 as much as possible so that there is no misalignment. Furthermore, since the nitric fluoride solution etches silicon isotropically, it is necessary to estimate the reduction in width in the lateral direction due to this. Thereafter, the resist and backside oxide film 211 are removed, each diffusion layer resistor is connected with aluminum wiring, a protective oxide film is formed on the surface, and a window is opened in the pad portion. The final completed drawings are shown in Figures 1a and 1b.

The equivalent circuit of the element of the present invention is a half-bridge circuit as shown in FIG. 3, and V _D , V _E ,
The symbols R _L1 , R _L2 , R _L3 , and R _S correspond to those in Figure 1a, _and the power supply parts _{R L1 are} connected to the beam by a low antibody formed in the center of the beam. The vertical force component is detected, and R _L2 and R _L3 are low antibodies formed at the edge of the beam, and the force component parallel to the support base of the beam is detected. In order to evaluate this element, as shown in Fig. 2 f and g, a silicone piece 214 with a side of 0.3 mm square was attached, and its surface was further covered with silicone rubber 215, and a load tester was applied from above, left and right, and diagonally upward. The measurement was performed by applying force from . The results are shown in FIG. Figure 4a shows the results when a vertical force is applied, Figure 4b shows the results when a horizontal force is applied, and Figure 4c shows the results when a force is applied diagonally downward at 45 degrees. However, the vertical axis shows the output value at maximum load as 1
It is normalized as . This figure shows that the linearity is good and the sensitivity is sufficient for force measurement. In addition, in Fig. 4, V _S1 ,
V _S2 is each of the Herb Bridge circuit in Figure 3.
This is the output value between the V _S1 and V _S2 terminals and the earth terminal V _E.

Next, the embodiment shown in FIG. 2 will be explained. The manufacturing method is
This is no different from the first example, and as shown in FIG. 5, the elements shown in FIG. 1 were oriented at 90° to each other and were fabricated on the same substrate. The first step is to measure the sample.
As in the example above, attach a piece of silicone to each beam, cover the entire surface with silicone rubber, and measure with a load tester by applying force from above, from the front and back, from the left and right, or from diagonal directions. It was found that the following characteristics can be obtained.

Next, a third embodiment will be described. In this example,
The point is that a beam supported on both sides is used instead of a beam supported on one side, as shown in FIG. 6a. In the case of this example as well, a prototype could be manufactured using the basic structure and manufacturing method of the present invention. Furthermore, since the beam is supported on both sides, the fracture strength can be increased several times compared to a beam supported on one side. In addition, in order to compensate for the fact that the force detection sensitivity is lower than that of a beam supported on one side, two diffused resistors 601 and 602 are installed in the vertical direction.
The problem was solved by arranging 06 diffused resistors.

In order to prevent the diagram from becoming complicated, the wiring pattern is omitted in FIG. 6a. Note that the equivalent circuit of FIG. 6a is shown in FIG. 6b, and R _S1 ,
R _S2 , R _L1 , R _L2 , R _L3 , R _L4 , R _L5 , R _L6 are shown in Figure 6b
corresponding to each resistance.

(Effects of the Invention) As described above in the Examples, when an element having the structure of the present invention was manufactured by the manufacturing method of the present invention, the basic function as a force sensor was achieved with good reproducibility and linear It also looked good in terms of sex.

In addition, in this example, since the purpose was to provide a tactile sensation for relatively small objects, a normal silicon substrate was used, and the beam size was small, about 500 μm x 1 mm x 20 μm. It is only necessary to design a value that is suitable for this purpose, and there is no change in the effects of the present invention. Furthermore, by arranging the elements of the present invention into an array, it is also possible to measure distributed pressure. It can also be used as a force sensor that applies not only tactile sensation but also moment.

[Brief explanation of drawings]

FIG. 1 is a diagram that best represents the structure of the present invention, and is a diagram of the completed device of the first embodiment. FIG. 1a is a plan view, and FIG. 1b is a sectional view taken at AB in FIG. be. 2A to 2E are schematic views of the device shown in FIG. 1 during the manufacturing process. Figure 2 f and g are
FIG. 3 is a mounting diagram of an element prepared for measuring element characteristics. 3 is an equivalent circuit diagram of FIG. 1, and FIG. 4 is a characteristic diagram of the element. Figure 5 is the second
FIG. 6a is a plan view of the device of the third embodiment. Figure 6b is Figure 6a
FIG. 101,201...Silicon substrate, 102,2
02... High concentration P ⁺ layer, 103, 104, 203,
204,503,504,601,602,60
3,604,605,606...Diffusion layer resistance, 1
05, 106, 205, 206, 211... silicon oxide film, 108, 208, 508... beam.

Claims (1)

[Scope of Claims] 1. On a beam provided on a silicon semiconductor substrate and supported on at least one side, near at least one supporting portion of the beam and also on the center line in the longitudinal direction of the beam when viewed from above. A half-bridge or full-bridge circuit is formed by the diffused layer resistor provided symmetrically with respect to the beam and at least one diffused layer resistor provided in the support part, and the circuit is formed on both sides of the beam near the support base of the beam. A herb bridge circuit is formed by the provided diffused layer resistors, or a full bridge circuit is formed by two diffused layer resistors provided on both sides thereof and a diffused layer resistor formed at the support base portion. force sensor. 2. On a beam provided on a silicon semiconductor substrate with at least one side indicated, place it near at least one support part of the beam and in such a way that it is symmetrical with respect to the center line in the longitudinal direction when the beam is viewed from above. A half-bridge or full-bridge circuit is formed by the diffusion layer resistance provided on the beam and at least one diffusion layer resistance provided on the support base, and the diffusion layer resistance provided on both sides of the beam near the support base of the beam. It is a force sensor in which a half-bridge circuit is formed by the two diffusion layer resistors provided on both sides of the sensor and a full-bridge circuit is formed by the diffusion layer resistor formed in the support part, and the element of this structure is A force sensor characterized in that at least two sets of elements having this structure rotated approximately 90 degrees within the plane of the substrate are arranged on the silicon substrate. 3 Manufacture of a force sensor consisting of a step of forming a diffused layer resistor on a silicon semiconductor substrate, a step of forming a silicon diaphragm and protecting the diaphragm part, a step of forming a beam, and a step of connecting each diffused resistor. A method for manufacturing a force sensor, comprising the step of etching away a portion of the diffusion layer resistance to equivalently form the diffusion layer resistance at the edge of the side surface of the beam.