WO2020059685A1

WO2020059685A1 - Sensor system and inclination detection method

Info

Publication number: WO2020059685A1
Application number: PCT/JP2019/036310
Authority: WO
Inventors: 晋司上野
Original assignee: オムロン株式会社
Priority date: 2018-09-21
Filing date: 2019-09-17
Publication date: 2020-03-26
Also published as: JP2020053416A

Abstract

The present invention identifies information about an inclination of a wafer, the information being more specific than the presence of the inclination. This sensor system (1) is provided with a PLC (2) that identifies the direction of the inclination of a wafer (10) being detected and the degree of the inclination of the wafer (10) on the basis of the change in light amount during a period in which a photoelectric sensor (6) detects the wafer (10).

Description

Sensor system and tilt detection method

The present invention relates to a sensor system and the like for detecting the inclination of a wafer stored in a wafer cassette using a photoelectric sensor.

A technique of projecting detection light onto a wafer while moving a photoelectric sensor and detecting the inclination of a wafer stored in a wafer cassette based on the amount of received detection light is known as a conventional technique. Japanese Patent Application Laid-Open No. H11-157210 determines whether there is a peak of a light reception amount exceeding a predetermined threshold outside a range near a wafer storage unit in a wafer cassette. A technique for determining that an abnormality such as insertion has occurred is disclosed.

Japanese Unexamined Patent Publication "JP-A-2000-150624 (published on May 30, 2000)"

However, the technique disclosed in Patent Document 1 can only determine whether the wafer is tilted. In other words, this technique does not allow the user to know detailed tilt information.

In view of the above problems, an object of one embodiment of the present invention is to realize a sensor system or the like that specifies more detailed information on the tilt of a wafer than the presence or absence of the tilt.

In order to solve the above-described problem, a sensor system according to one embodiment of the present invention is a sensor system that detects an inclination of a wafer stored in a wafer cassette, and includes three or more photoelectric sensors and the three or more photoelectric sensors. Is moved in a direction perpendicular to the plane of the normally accommodated wafer while the plane including the three or more photoelectric sensors is parallel to the plane of the wafer normally accommodated. Movement control device, during the movement of the photoelectric sensor, an acquisition device that acquires the amount of light received by the photoelectric sensor, based on the change in the amount of light during the period when the photoelectric sensor is detecting the detection target wafer, A specification device for specifying the direction of the tilt of the wafer and the magnitude of the tilt of the wafer.

In order to solve the above problem, an inclination detection method according to one embodiment of the present invention is an inclination detection method using a sensor system that detects an inclination of a wafer stored in a wafer cassette, wherein the sensor system includes: It is provided with three or more photoelectric sensors, and the three or more photoelectric sensors are normally accommodated in a state in which a plane including the three or more photoelectric sensors is parallel to a plane of the wafer in which the plane is normally accommodated. A moving step of moving the wafer in a direction perpendicular to the plane of the wafer, and during the moving step, an obtaining step of obtaining an amount of light received by the light receiving unit, and the photoelectric sensor detects a wafer to be detected. Specifying a direction of the inclination of the wafer and a magnitude of the inclination of the wafer based on a change in the amount of light during a certain period.

According to one embodiment of the present invention, it is possible to specify more detailed information on the inclination of a wafer, such as the amount of vertical displacement of the wafer, the magnitude of the inclination in the horizontal direction, the magnitude of the inclination in the front-rear direction, and the like, whether or not the inclination exists. Can be.

FIG. 1 is a diagram schematically illustrating an example of a hardware configuration of each device included in a sensor system according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of an operation of removing a wafer from a wafer cassette by the transfer robot illustrated in FIG. 1. FIG. 3 is a diagram illustrating an example of a positional relationship between the wafer and the sensor hand illustrated in FIGS. 1 and 2 in detecting the inclination of the wafer. (A) is a figure which shows the positional relationship between the wafer and each sensor shown using XYZ coordinates, (b) is a figure which shows an example of a temporal change of the light quantity of the detection light in a transmission sensor and a reflection sensor. is there. (A) is a schematic diagram for explaining the principle of measurement of right and left inclination by two reflection sensors, and shows a state in which the wafer is inclined to the right, and (b) is a diagram illustrating two reflection sensors. FIG. 4 is a diagram illustrating a change over time in the amount of light detected by a sensor. FIG. 7 is a diagram illustrating a comparison of a change with time in the amount of light detected by a transmission sensor with time when the wafer has a tilt and when there is no tilt. It is a schematic diagram for demonstrating the measurement principle of right-left inclination by two reflection-type sensors, and shows the state in which a wafer is not inclined. FIG. 4 is a diagram illustrating a change over time in the amount of light detected by a transmission sensor and a reflection sensor. FIG. 2 is a diagram schematically illustrating an example of a functional configuration of the PLC illustrated in FIG. 1. 2 is a flowchart illustrating an example of a procedure of a process executed by the PLC illustrated in FIG. 1. FIG. 11 is a diagram schematically illustrating an example of a hardware configuration of each device included in a sensor system according to a modification of the present invention. FIG. 10 is a diagram illustrating a mounting position of a sensor in the sensor hand according to the second embodiment. FIG. 7 is a diagram showing a change over time in the amount of light detected by two

reflection sensors

67 and 68. FIG. 6 is a diagram showing a change over time in the amount of light detected by two reflection sensors 67 (or 68) and 69.

<First embodiment>
Hereinafter, an embodiment according to one aspect of the present invention (hereinafter, also referred to as “the present embodiment”) will be described with reference to the drawings.

§1 Application Example First, an example of a scene to which the present invention is applied will be described with reference to FIG. FIG. 1 is a diagram schematically illustrating an example of a hardware configuration of each device included in the sensor system 1 according to the present embodiment. The sensor system 1 is a sensor system that detects a tilt of a wafer stored in a wafer cassette.

As shown in FIG. 1, the sensor system 1 includes a PLC (programmable logic controller) 2, a sensor unit 3, a transfer robot 4, a sensor hand 5, and a photoelectric sensor 6. The transfer robot 4 includes a chuck 7 for taking out a wafer from a wafer cassette. Details of the PLC 2, the sensor unit 3, the transfer robot 4, and the sensor hand 5 will be described later. As shown in FIG. 1, the photoelectric sensor 6 includes a transmission sensor 61 and

reflection sensors

62 and 63. The transmission sensor 61 further includes a light projecting unit 61a and a light receiving unit 61b, and is realized by a fiber sensor as an example. The light emitting unit 61a emits the detection light, and the light receiving unit 61b receives the detection light. The

reflection sensors

62 and 63 project detection light toward the outer periphery of the wafer and receive the detection light reflected from the wafer.

FIG. 3 shows the positional relationship between the sensor hand 5 and the photoelectric sensor. The light projecting portion 61a and the light receiving portion 61b of the transmission sensor 61 are at the tip of the sensor hand 5 so that the detection light projected by the light projecting portion 61a passes through two points on an arc forming the outer periphery of the wafer. Provided. The

reflection sensors

62 and 63 are provided at positions symmetrical with respect to a straight line 1 connecting the midpoint of the light projecting unit 61a and the light receiving unit 61b to the center point of the wafer. Further, the

reflection sensors

62 and 63 are located on a circular arc forming the outer periphery of the wafer other than the two points, and a straight line l passing through the center point of the straight line connecting the two points and the center point of the wafer. The symmetrical position is provided so as to be a detection area.

In the drawings, the direction parallel to the traveling direction of the detection light 60 from the transmission sensor 61 is the y-axis direction, and the direction parallel to the plane 101 of the normally mounted wafer 10 and orthogonal to the y-axis is the x-axis direction. , And the direction orthogonal to the x-axis and the y-axis is defined as the z-axis.

In the sensor system 1 of the present invention, three or more photoelectric sensors including a transmission sensor or a reflection sensor are used to acquire data on a temporal change in the amount of detection light received by these sensors, and compare these data. I do. This makes it possible to obtain detailed information on the tilt of the wafer, such as the amount of displacement of the wafer in the z-axis direction, the tilt in the horizontal direction (tilt around the x-axis), and the tilt in the front-rear direction (tilt around the y-axis).

In the sensor system 1, the movement control device (the actuator 8 of the transfer robot 4) includes a plane including the transmission sensor 61 (the light projecting unit 61 a and the light receiving unit 61 b), the reflection sensor 62, and the reflection sensor 63 (ie, the upper surface of the sensor hand 5). ) Is moved at a constant speed in a direction perpendicular to the plane of the normally stored wafer (that is, the z-axis) in a state parallel to the plane of the normally stored wafer. During this time, the sensor unit 3 scans the wafer 10 with the detection light from the photoelectric sensor, and acquires the light amount of the detection light received by the sensor unit 3 with the photoelectric sensor. Then, the inclination detection unit 211 specifies the direction of the inclination of the wafer 10 and the magnitude of the inclination of the wafer 10 based on the temporal change in the amount of light during the period when the photoelectric sensor is detecting the target wafer 10.

In the above, during the period when the transmission sensor 61 is detecting the wafer 10, the light amount of the detection light to be received is the minimum value. In addition, during the period when the

reflection sensors

62 and 63 are detecting the wafer 10, the amount of the detection light received becomes the maximum value.

By arranging three or more photoelectric sensors such that different positions on the arc forming the outer periphery of the wafer are the irradiation areas of the detection light, the light amount of the detection light received by each transmission sensor becomes the minimum value. By using the difference in the timings or the difference in the timing at which the amount of the detection light received by each reflection sensor becomes the maximum value, the inclination in the left-right direction and the inclination in the front-back direction of the wafer can be specified. .

In addition, the acquisition device previously acquires data on a temporal change in the amount of detection light received by the transmission sensor or the reflection sensor with respect to a normal wafer having no displacement and no tilt in the z-axis direction. Causes the storage unit 22 to store this as the reference data 221. Then, the PLC 2 compares the stored reference data 221 with the data of the change over time in the light amount of the detection wafer. Thus, the PLC 2 specifies the amount of displacement of the wafer in the z-axis direction.

§2 Configuration example [Hardware configuration]
<PLC>
Next, an example of a hardware configuration of the PLC 2 according to the present embodiment will be described with reference to FIG. The PLC 2 is a control device that controls the sensor unit 3 and the transfer robot 4 included in the sensor system 1.

では In the example of FIG. 1, the PLC 2 includes a control unit 21, a storage unit 22, and a communication interface 23. These components of the PLC 2 are electrically connected to each other by a communication bus. The PLC 2 according to the present embodiment corresponds to the “specific device” of the present invention.

The control unit 21 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and controls each component according to information processing. The storage unit 22 is an auxiliary storage device such as a hard disk drive and a solid state drive.

The communication interface 23 is, for example, a wired LAN (Local Area Network) module, a wireless LAN module, or the like, and is an interface for performing wired or wireless communication via a network.

In addition, regarding the specific hardware configuration of the PLC 2, it is possible to omit, replace, and add components according to the embodiment. For example, the control unit 21 may include a plurality of processors.

<Transport robot>
Next, an example of a hardware configuration of the transfer robot 4 according to the present embodiment will be described with reference to FIGS. FIG. 2 is a diagram illustrating an example of an operation of taking out the wafer 10 from the wafer cassette 20 by the transfer robot 4.

In the example of FIG. 1, the transfer robot 4 is a transfer device that transfers the wafer 10, and includes the chuck 7 for removing the wafer 10 from the wafer cassette 20. The chuck 7 is, for example, a U-shaped (or Y-shaped) member as shown in FIG. As shown in FIG. 2, the root side of the chuck 7 is connected to the actuator 8 of the transfer robot 4. As the transfer robot 4 is controlled by the control unit 21, the chuck 7 is inserted below the wafer 10 housed in the wafer cassette 20, as shown in FIG. As a result, the wafer 10 is placed on the chuck 7 from the state placed on the wafer cassette 20 and is taken out of the wafer cassette 20. The transfer robot 4 is controlled by the control unit 21 and transfers the wafer 10 placed on the chuck 7. The transfer robot 4 according to the present embodiment corresponds to the “transfer device” of the present invention.

In the example of FIG. 2, the sensor hand 5 is connected to the opposite side of the chuck 7 via the actuator 8 of the transfer robot 4. The sensor hand 5 includes three or more photoelectric sensors. The sensor hand 5 is also moved by the transfer robot 4. When taking out a wafer from the wafer cassette 20, the transfer robot 4 first turns the sensor hand 5 toward the wafer cassette 20, scans the wafer 10 stored in the wafer cassette 20, and specifies the inclination and angle of the wafer 10. Thereafter, the transfer robot 4 rotates by 180 degrees, directs the chuck 7 toward the wafer cassette 20, and causes the chuck 7 to perform an operation of taking out the wafer 10 from the wafer cassette 20. At this time, the transfer robot 4 controls the tilt of the chuck 7 according to the tilt and the angle of the wafer 10 specified above. Thereby, the wafer 10 can be prevented from being damaged by the chuck 7.

In the examples of FIGS. 1 and 2, the sensor hand 5 includes a transmission sensor 61, a reflection sensor 62, and a reflection sensor 63. The transmission sensor 61 includes a light projecting unit 61a and a light receiving unit 61b. As an example, as shown in FIG. 3, the light projecting portion 61a and the light receiving portion 61b are provided so that the detection light passes through two points on an arc forming the outer periphery of the wafer at the tip end of the sensor hand 5. Have been. The reflection sensor 62 and the reflection sensor 63 are located on a circular arc forming the outer periphery of the wafer other than the two points, and a straight line l passing through the center point of a straight line connecting the two points and the center point of the wafer. The symmetrical position is provided so as to be a detection area. Therefore, in the present embodiment, the transmission sensor 61, the reflection sensor 62, and the reflection sensor 63 are moved by the movement of the sensor hand 5 by the transfer robot 4. That is, the transfer robot 4 also moves the sensor hand 5. Therefore, the transfer robot 4 according to the present embodiment also corresponds to the “movement control device” of the present invention.

Hereafter, in the sensor hand 5, the portion where the light projecting portion 61a and the light receiving portion 61b are provided is also described as "hand". In the example of FIG. 3, the light projecting unit 61 a is provided on one hand of the sensor hand 5, and the light receiving unit 61 b is provided on the other hand. Further, a reflection sensor 62 and a reflection sensor 63 are provided on a protrusion 65 and a protrusion 66 extending from the sensor hand 5, respectively. In the present specification, the light projecting unit 61a and the light receiving unit 61b of the transmission sensor 61 are each counted as one photoelectric sensor. Therefore, the sensor hand 5 is provided with four photoelectric sensors 6 (light emitting unit 61a, light receiving unit 61b, reflection sensor 62, and reflection sensor 63).

As in the example shown in FIG. 3, when the diameter of the wafer 10 is 200 mm, for example, the light projecting unit 61 a and the light receiving unit 61 b irradiate the detection light 60 to a position 70 mm from the center of the wafer surface 101. It is provided at the position of the chuck 5. Further, the

reflection sensors

62 and 63 are arranged such that the distance between them is about 142 mm, and the detection light projected from the

reflection sensors

62 and 63 is at most 45 degrees with respect to the straight line l toward the center of the wafer. It is mounted to illuminate an arc that forms an outer circumference of the wafer at an angle.

Note that the light projecting unit 61a and the light receiving unit 61b may be provided at the position of the sensor hand 5 at which the wafer 10 is irradiated with the detection light, and the positions are not limited to the positions shown in FIG.

In the present embodiment, an example will be described in which the light emitting unit 61a is provided at the tip of the left hand of the sensor hand 5 in FIG. 3 and the light receiving unit 61b is provided at the tip of the right hand. However, the light receiving unit 61b may be provided at the tip of the left hand, and the light emitting unit 61a may be provided at the tip of the right hand.

<Sensor unit 3>
The sensor unit 3 is controlled by the control unit 21 and controls the

photoelectric sensors

61, 62, and 63. Specifically, the sensor unit 3 controls start and stop of the projection of the detection light. More specifically, the sensor unit 3 continues to emit the detection light while the

photoelectric sensors

61, 62, and 63 are moving. That is, the sensor unit 3 acquires the light amount of the detection light received by the

photoelectric sensors

61, 62, and 63 while the

photoelectric sensors

61, 62, and 63 are moving, and converts the light amount into light amount data by A / D conversion. Send to PLC2. The sensor unit 3 according to the present embodiment corresponds to the “acquisition device” of the present invention.

[Functional Configuration of PLC]
Next, an example of a functional configuration of the PLC 2 according to the present embodiment will be described with reference to FIG. FIG. 9 is a diagram schematically illustrating an example of a functional configuration of the PLC 2 according to the present embodiment.

The control unit 21 of the PLC 2 according to the present embodiment includes a tilt detection unit 211 and a robot control unit 212 as functional components. The storage unit 22 stores at least reference data 221 as an example.

The inclination detection unit 211 acquires light amount data of the detection light from the sensor unit 3 and, based on a change in light amount (change with time) during a period when the

photoelectric sensors

61, 62, and 63 are detecting the wafer 10 to be detected. The inclination of the wafer 10 is specified. More specifically, the amount of displacement of the wafer in the z-axis direction, the direction and magnitude of the tilt of the wafer around the x-axis, and the direction and magnitude of the tilt of the wafer around the y-axis direction are specified. I do.

The “period during which the detection target wafer 10 is detected” is a period during which the detection light 60 is irradiated on the wafer 10 (a period during which the

photoelectric sensors

61, 62, and 63 cross the outer peripheral surface 102). is there. The robot control unit 212 controls the transfer robot 4 and the sensor hand 5. Specifically, the robot control unit 212 controls the tilt of the chuck 7 according to the tilt of the wafer specified by the tilt detection unit 211.

{Circle around (4)} The control unit 21 moves the sensor hand 5 at a constant speed along the z-axis direction, and detects the value of the amount of detection light received by each photoelectric sensor at that time. Therefore, the “time-dependent change in light amount” refers to a change in light amount according to the moving distance of the sensor hand 5 along the z-axis.

The reference data 221 is data used as a reference for the inclination of the wafer 10 when the inclination detection unit 211 specifies the inclination of the wafer 10. The reference data 221 is, for example, a temporal change in the amount of detection light received by each of the transmission sensor 61, the

reflection sensors

62, and 63 when the wafer 10 is not tilted and has no displacement in the z-axis direction. There may be. For example, the reference data 221 may include a temporal change of the light amount shown in FIG.

As an example, the control unit 21 may execute an appropriate program to execute the above processing as the inclination detection unit 211 and the robot control unit 212. The program may be stored in a ROM, for example. In the case of this example, the control unit 21 loads the program stored in the ROM into the RAM. Then, the control unit 21 controls the components of the PLC 2 by interpreting and executing the program developed in the RAM by the CPU.

The recording medium storing the above program may be any non-transitory tangible medium, and may be a ROM, tape, disk, card, semiconductor memory, programmable logic circuit, or the like. Further, the program may be supplied to the PLC 2 via an arbitrary transmission medium (a communication network, a broadcast wave, or the like) capable of transmitting the program. Note that one embodiment of the present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the program is embodied by electronic transmission.

The details of the processing executed by the tilt detection unit 211 and the robot control unit 212 will be described in an operation example described later. In the present embodiment, the inclination detection unit 211 and the robot control unit 212 are both described as being realized by a general-purpose CPU. However, these may be realized by one or more dedicated processors. Further, regarding the functional configuration of the PLC 2, the omission, replacement, and addition of the configuration may be appropriately performed according to the embodiment.

§3 Operation Example Next, an operation example of the PLC 2 will be described with reference to FIG. FIG. 10 is a flowchart illustrating an example of a processing procedure of the PLC 2. The processing procedure described below is an example, and there is no intention to limit the processing procedure of the PLC 2 according to the present embodiment to this example. Further, in the processing procedure described below, steps can be omitted, replaced, and added as appropriate according to the embodiment.

The robot control unit 212 moves the sensor hand 5 to a normally stored wafer in a state where a plane including three or more photoelectric sensors mounted thereon is parallel to the plane of the wafer normally stored. Is moved in a direction (z-axis direction) perpendicular to the plane (step S1, movement step). The process of step S1 is realized by the robot control unit 212 transmitting a control command to the transfer robot 4 via the communication interface 23. Further, when the movement of the sensor hand 5 is started, the robot control unit 212 notifies the inclination detection unit 211 of the start. Subsequently, upon receiving the notification from the robot control unit 212, the tilt detection unit 211 controls the sensor unit 3 to start emitting the detection light from each of the

photoelectric sensors

61, 62, and 63 to the wafer 10. (Step S2, acquisition step). The process of step S2 is realized by the tilt detection unit 211 transmitting a control command to the sensor unit 3 via the communication interface 23.

Subsequently, the sensor unit 3 acquires the light amount of the detection light received by each of the

photoelectric sensors

61, 62, and 63 (Step S3, acquisition step). The sensor unit 3 converts the acquired light amount into light amount data, and temporarily stores the light amount data in association with light receiving unit identification information for identifying each of the

photoelectric sensors

61, 62, and 63. When the sensor unit 3 receives the light amount data transmission instruction from the PLC 2, the sensor unit 3 transmits all the light amount data obtained at that time to the PLC 2 in a state where the light amount identification information is associated with the light amount data.

Next, the inclination detecting unit 211 of the PLC 2 compares the temporal change of the light amount generated using the received light amount data with the reference data 221 (Step S4). Then, based on the comparison result, the tilt detection unit 211 determines whether the wafer 10 is tilted around the x-axis and y-axis and whether there is a displacement in the z-axis direction (step S5). .

Hereinafter, in a sensor system including a pair of transmission sensors and two reflection sensors as shown in FIG. 3, the displacement amount of the wafer 10 in the z-axis direction, the magnitude of the tilt of the wafer around the y-axis, and the wafer around the x-axis A method for determining the magnitude of the inclination of the will be described.

(Specification of inclination of wafer 10)
First, identification of the amount of displacement of the wafer 10 in the z-axis direction will be described.

FIG. 4A is a diagram illustrating an example of irradiation of the wafer 10 with detection light for detecting the inclination of the wafer 10, and FIG. 4B is a diagram illustrating the detection light of the transmission sensor and the reflection sensor. It is a figure showing an example of a temporal change of light quantity. The wafer 10 shown in FIG. 4A has a cylindrical shape. Specifically, as shown in FIG. 4A, the wafer 10 has a wafer surface 101 (the plane of the wafer 10) and an outer peripheral surface 102. Further, as shown in FIG. 4A, the sensor system 1 includes three or more photoelectric sensors. Two of the three or more photoelectric sensors are a pair of transmissive sensors (a light projecting portion 61a of the transmissive sensor 61 and a pair of transmissive sensors provided so that detection light passes through two points on an arc forming the outer periphery of the wafer). A light receiving unit 61b). The three or more photoelectric sensors further include two reflection sensors (reflection sensors 62 and 63) provided such that a position other than the two points is a detection area on an arc forming the outer periphery of the wafer. Including. The two reflection sensors (reflection sensors 62 and 63) are located on a circular arc forming the outer periphery of the wafer 10 other than the two points, the center point of a straight line connecting the two points and the center point of the wafer. Are provided such that a position symmetrical with respect to a straight line passing through the detection region is a detection region.

The sensor system 1 includes three photoelectric sensors (a transmission sensor 61, a reflection sensor 62, and a reflection sensor 63) in a state where the plane (that is, the sensor hand 5) is parallel to the plane of the wafer in which the plane is normally accommodated. The two photoelectric sensors are moved at a constant speed in the direction perpendicular to the plane of the normally accommodated wafer, that is, in the z-axis direction. In the illustrated example, the photoelectric sensor 6 is moved in the negative direction of the z-axis in FIG. 4A. However, the moving direction is opposite to the example shown in FIG. It may be moved in the forward direction. In addition, the sensor system 1 controls the transmission sensor 61 so that the light projecting unit 61a continuously emits the detection light 60 while the transmission sensor 61 is moving, and causes the light receiving unit 61b to receive the detection light 60. . Hereinafter, performing projection and reception of the detection light 60 while moving the transmission sensor 61 at a constant speed is also referred to as “scan”.

(4) A temporal change in the light amount of the detection light 60 received by the light receiving unit 61b is, for example, a graph indicated by A1 in FIG. 4B. Before the detection light 60 reaches the wafer surface 101, since the detection light 60 is not blocked by the wafer 10, the light amount of the detection light 60 received by the light receiving unit 61b is maximum. Strictly speaking, the amount of received light exceeds the maximum value just before the graph A1 starts to decrease. This is because the reflected light on the wafer surface 101 is added to the transmission sensor 61 so that the light enters the transmission sensor 61 more greatly. Thereafter, the detection light 60 reaches the upper wafer surface 101 in FIG. For this reason, the light amount decreases, and eventually reaches the minimum value. When the detection light 60 reaches the lower wafer surface 101 in FIG. 4A, the light amount increases again and eventually returns to the maximum value.

As shown in FIG. 4A, when the wafer surface 101 is parallel to the horizontal plane, that is, when the wafer 10 is not inclined, the temporal change of the light amount of the detection light 60 is indicated by A1 in FIG. 4B. It becomes a graph. On the other hand, when the wafer surface 101 is not parallel to the horizontal plane, that is, when the wafer 10 is tilted, the period in which the detection light projected from the transmission sensor 61 is blocked is the time when the wafer 10 is not tilted. 6, the width L2 when the amount of received light is equal to or less than a certain amount becomes longer than L1 when the wafer is placed in a normal state, as indicated by A2 in FIG. The graph is different from the graphs indicated by A1 in FIG. 4B and FIG. Details of the different graphs will be described later.

(4) The temporal changes in the detection light received by the reflection sensor 62 and the reflection sensor 63 during scanning are, for example, graphs indicated by B1 and B2 in FIG. 4B, respectively. At B1 or B2 in FIG. 4B, before the detection light reaches the outer peripheral surface 102 of the wafer surface 101, since the detection light is not reflected on the outer peripheral surface 102 of the wafer 10, the

reflection sensor

62 or 63 The amount of the detection light received is the minimum value. Thereafter, when the detection light reaches the upper wafer surface 101 in FIG. 4A, the detection light is reflected by the outer peripheral surface 102 of the wafer 10. For this reason, the light amount increases and eventually reaches a maximum value. Thereafter, when the detection light reaches the lower wafer surface 101 in FIG. 4A, the detection light is not reflected on the outer peripheral surface 102 of the wafer 10, so that the amount of received detection light increases. Eventually it returns to the minimum value.

In the sensor system 1, the inclination detection unit 211 of the PLC 2 determines whether or not the wafer 10 is inclined and, if so, the direction and magnitude (angle) of the inclination when the wafer 10 is inclined. Identify. Thereby, the sensor system 1 can specify more detailed information on the inclination of the wafer 10 than the presence or absence of the inclination.

As the direction of the inclination, for example, among the points forming the outer periphery of the wafer surface 101, the direction from the highest point to the lowest point with respect to the horizontal plane may be specified. Further, as the angle of the inclination, for example, the angle of the wafer surface 101 with respect to the horizontal plane may be defined.

(Method of measuring displacement in wafer z-axis direction)
The measurement of the amount of displacement of the wafer 10 in the z-axis direction will be described. First, as shown in FIG. 4, the temporal change of the amount of light received by the light receiving unit 61b of the transmission sensor 61 is measured for a normal wafer 10 having no displacement in the z-axis direction and no tilt. The data is stored in the storage unit 22. The timing when the light amount of the detection light 60 becomes the minimum value corresponds to the position in the z-axis direction 0. This is compared with data on the change with time of the detection light 60 for the detection wafer. By comparing the point at which the light amount becomes the minimum value with the timing at which the light amount becomes the minimum value in the reference data, the displacement amount of the wafer 10 in the z-axis direction can be calculated. In other words, since the sensor hand 5 is moving at a constant speed in the z-axis direction, the amount of displacement and the direction in the z-axis direction can be specified by comparing the timing at which the detection light has a minimum value. .

If the timing at which the amount of light becomes the minimum value in the data of the change with time of the detection light for the detection wafer is earlier than that of the reference data, the tilt detection unit 211 determines that the wafer has been displaced upward in the z-axis direction. be able to. Conversely, when the timing at which the light amount becomes the minimum value in the data of the change with time of the detection light for the detection wafer is later than that of the reference data, the tilt detection unit 211 moves the wafer downward in the z-axis direction. It can be determined that it has been done. Further, the control unit 21 calculates the displacement amount of the detection wafer in the z-axis direction based on the difference between the timing when the amount of transmitted light to the detection wafer becomes the minimum value and the timing when the amount of transmitted light in the reference data becomes the minimum value. Can be identified.

Alternatively, the PLC 2 can calculate the amount of displacement of the wafer in the z-axis direction by using the reflection sensor 62 and the reflection sensor 63. The control unit 21 measures a change in the amount of light during scanning of the reflection sensor 62 or the reflection sensor 63 with respect to a wafer in a normal state having no displacement and no tilt in the z-axis direction and stores the reference data and the storage unit 22. . Then, the control unit 21 measures the change over time of the detection light of the two

reflection sensors

62 and 63 with respect to the detection wafer, and specifies the timing corresponding to the center point of the point at which the amount of received light reaches the maximum value. I do. By comparing this timing with the timing at which the amount of detection light received by the reflection sensor in the reference data reaches the maximum value, the displacement amount of the wafer in the z-axis direction can be calculated.

(Specification of tilt direction and tilt amount around x axis)
When the sensor unit 3 is moved downward in the z-axis direction as shown in FIG. 5A and the change over time in the amount of light of the reflection sensor 62 and the reflection sensor 63 is measured, the measurement result shown in FIG. 5B is obtained. . Here, the timing at which the amount of light received by the reflection sensor 62 located on the left side has the maximum value is earlier than the timing at which the amount of light received by the reflection sensor 63 located on the right side has the maximum value. When the detection light from the reflection sensor passes through the wafer, the amount of the detection light received by the reflection sensor becomes maximum. Therefore, it is possible to specify which of the reflection sensor 62 and the reflection sensor 63 the wafer 10 is tilted around the x-axis depending on which of the reflection sensor 62 and the light reception amount reaches the maximum value first. In the case where the reflection sensor 62 has the maximum amount of received light before the reflection sensor 63 as shown in FIG. 5B, it can be specified that the wafer rises to the left around the x-axis, that is, the wafer is tilted to the right. On the other hand, when the reflection sensor 63 arranged on the right side has the maximum amount of received light before the reflection sensor 62 arranged on the left side, it rises right around the x axis, that is, the wafer tilts to the left. Can be identified.

{Circle around (4)} The control unit 21 can also calculate the magnitude of the inclination of the wafer around the x-axis from the change over time of the amount of light received by the reflection sensor 62 and the reflection sensor 63 shown in FIG. In FIG. 5B, if the wafer is not tilted around the x-axis, the graphs of the change over time of the detected light amount indicated by the two

reflection sensors

62 and 63 overlap. As the inclination of the wafer around the x-axis increases, the graphs of the change in the detected light amount over time shown by the two reflection sensors move away from each other. Therefore, the width L between the points where the two reflection sensors have the maximum value shown in FIG. 5B is proportional to the magnitude of the inclination of the wafer around the x-axis. Therefore, by measuring the width L between the points having the maximum value, the inclination of the wafer around the x-axis can be specified.

Alternatively, as shown in FIG. 6, the magnitude of the inclination of the wafer around the x-axis can be specified by analyzing the temporal change of the amount of light received by the light receiving unit 61a of the transmission sensor 61 by the PLC 2. The reference data A1 of the change over time of the light received by the transmission sensor 61 with respect to the wafer in which the inclination of the PLC 2 around the x axis is 0 is obtained in advance and stored in the storage unit 22. Then, the PLC 2 compares the reference data A1 with time-dependent change data A2 of the amount of light received from the transmission sensor 61 for the detection wafer. When the transmitted light passes through the wafer, the amount of received light reaches a minimum value. While the transmission sensor 61 is detecting a wafer, the amount of detection light received is a minimum value. As the inclination of the wafer around the x-axis is larger, the width of the portion where the light amount becomes the minimum value becomes wider. Accordingly, the PLC 2 compares the width L1 of the portion where the light amount of the detection light is equal to or less than the predetermined value in the reference data A1 with the width L2 of the portion where the amount of received light is equal to or less than the predetermined value in the detection data A2, thereby obtaining the x-axis. The magnitude of the inclination of the wafer around it can be specified.

If the magnitude of the tilt of the wafer calculated using the reflection sensor is different from the magnitude of the tilt of the wafer calculated using the transmission sensor, the PLC 2 calculates the average value of the tilt of the wafer. May be specified.

(Measurement method of inclination direction and magnitude of inclination around y axis)
Next, a method of specifying the tilt of the wafer around the y-axis and the magnitude of the tilt will be described.

(4) The transfer robot 4 moves the sensor hand 5 at a constant speed downward in the z-axis, and at this time, the PLC 2 compares the change over time of the amount of light detected by the transmission sensor 61, the reflection sensor 62, and the reflection sensor 63 with time. Thus, the tilt direction and the magnitude of the tilt of the wafer around the y-axis can be specified. FIG. 8 is a diagram showing a temporal change (A1) of the amount of light detected by the transmission sensor 61 and a temporal change (B1 and B2) of the amount of light detected by the

reflection sensors

62 and 63. As shown in FIG. 8, the wafer is moved by the timing t1 at which the amount of detection light received by the transmission sensor 61 becomes the minimum value and the timing t2 or t3 at which the reflection light amount received by the

reflection sensor

62 or 63 becomes the maximum value. It can be specified which direction around the y axis is inclined. In this embodiment, the two

reflection sensors

62 and 63 are arranged on the x-axis direction front side of the transmission sensor 61. Therefore, as shown in FIG. 8, when the timing t2 or t3 when the amount of light received by the

reflection sensors

62 and 63 reaches the maximum value is earlier than the timing t1 when the detection light received by the transmission sensor reaches the minimum value. The control unit 21 can specify that the wafer is raised forward, that is, inclined backward. Conversely, if the time t2 or t3 when the detection light received by the

reflection sensor

62 or 63 has the maximum value is later than the time t1 when the detection light received by the transmission sensor has the minimum value, the controller 21 Can be specified that the wafer is lowered forward, that is, tilted forward. Further, for example, the control unit 21 calculates the y-axis based on the difference between the time point t2 at which the amount of detection light received by the reflection sensor 62 reaches a maximum value and the time point t1 at which the amount of detection light received by the transmission sensor 61 reaches a minimum value. The magnitude of the inclination of the wafer around it can be specified.

Return to the description of the operation example with reference to FIG. 10 again. The tilt detector 211 outputs the specified tilt direction, angle, and z-axis displacement of the wafer 10 to the robot controller 212. The robot controller 212 controls the tilt of the chuck 7 in accordance with the obtained direction, angle (magnitude of tilt), and displacement of the wafer 10 in the z-axis direction (step S8). Specifically, the robot control unit 212 determines the tilt direction, angle, and z-axis position of the chuck 7 according to the acquired tilt direction, angle, and z-axis displacement amount of the wafer 10. Then, the robot control unit 212 transmits a control command including the determined tilt direction, angle, and z-axis position of the chuck 7 to the transfer robot 4 via the communication interface 23. Thereby, the transfer robot 4 can adjust the direction and angle of the tilt of the chuck 7 according to the direction and angle of the tilt of the wafer 10 and the amount of displacement in the z-axis direction.

(4) Finally, the transfer robot 4 takes out the wafer 10 from the wafer cassette 20 (Step S9) and transfers it. The process of step S9 is realized by the robot control unit 212 transmitting a control command to the transfer robot 4 via the communication interface 23. The control command may be transmitted to the transfer robot 4 together with the control command transmitted in step S8, or may be transmitted after the control command transmitted in step S8.

If the tilt detection unit 211 determines that the wafer 10 is not tilted and has no displacement in the z-axis direction (NO in step S5), steps S6 to S8 are omitted. In other words, the PLC 2 allows the transfer robot 4 to take out the wafer 10 without adjusting the tilt direction, angle, and position in the z-axis direction of the chuck 7 because the wafer 10 is placed in a normal state. (Step S9).

[Action / Effect]
As described above, in the present embodiment, in steps S6 and S7, the PLC 2 specifies the direction and angle of the tilt of the wafer 10 and the displacement in the z-axis direction. That is, the PLC 2 can specify more detailed information on the inclination of the wafer 10 than the presence or absence of the inclination.

As an example, the PLC 2 can adjust the tilt direction, angle, and z-axis position of the chuck 7 based on the specified tilt direction and angle of the wafer 10 in step S8. Thus, even when the wafer 10 is tilted, the wafer 10 can be taken out of the wafer cassette 20 without damaging it. Therefore, even when the wafer 10 is tilted, the transfer of the wafer 10 by the transfer robot 4 can be continued. The case where the wafer 10 is tilted includes the case where the wafer 10 is tilted and stored in the wafer cassette 20 and the case where the wafer cassette 20 itself is tilted.

<Embodiment 2>
A second embodiment of the present invention will be described below. For convenience of description, members having the same functions as those described in the above embodiment are denoted by the same reference numerals, and description thereof will not be repeated.

Hereinafter, a method for specifying the inclination of the wafer 10 in the present embodiment will be described with reference to FIG.

In the present embodiment, the inclination of the wafer 10 is specified by using three

reflection sensors

67, 68, and 69.

In the present embodiment, as shown in FIG. 12, the sensor hand 5 does not include the transmission sensor, but includes three reflection sensors. As an example, as shown in FIG. 12, the sensor hand 5 according to the present embodiment includes a reflection sensor 67 and a reflection sensor 68 at positions of the reflection sensor 62 and the reflection sensor 63 in the first embodiment, respectively. That is, a reflection sensor 69 is provided on the sensor hand 5 side (that is, forward) of the straight line l connecting the two

reflection sensors

67 and 68 and the straight line 1 connecting the center point of the wafer and the

reflection sensors

67 and 68. I have. The

reflection sensors

67 and 68 may be provided at the positions of the light projecting unit 61a and the light receiving unit 61b of the transmission sensor 61 in the first embodiment, respectively.

構成 Other configurations are the same as those of the first embodiment. A method of specifying the tilt of the wafer, that is, the amount of displacement in the z-axis direction, the tilt direction and magnitude around the x-axis, and the tilt direction and magnitude around the y-axis in the present embodiment will be described below.

(Method of measuring the amount of displacement in the z-axis direction)
In advance, while the transfer robot 4 moves the sensor hand 5 downward at a constant speed at a constant speed, the sensor unit 3 detects the detection light received by the

reflection sensor

67, 68, or 69 for a normal wafer having no tilt. To obtain the change over time. The PLC 2 stores this in the storage unit 22 as reference data. Similarly, while the transfer robot 4 moves the sensor hand 5 at a constant speed downward in the z-axis, the sensor unit 3 sets the data of the change over time of the detection light received by the two

reflection sensors

65 and 66 for the detection wafer. To get. The PLC 2 specifies the timing corresponding to the center point of the point where the light amount of the detection light becomes the maximum value, and compares it with the timing at which the light amount of the detection light becomes the maximum value in the reference data measured in advance. If the timing at which the temporal change in the light amount on the detection wafer becomes the maximum value is earlier than the timing at which the reference data has the maximum value, the PLC 2 determines that the wafer has been displaced in the z-axis direction. Conversely, if the timing at which the temporal change in the amount of light in the detection wafer becomes the maximum value is later than the timing at which the reference data has the maximum value, the PLC 2 determines that the wafer has been displaced downward in the z-axis direction. I do. Further, the PLC 2 can specify the displacement amount of the wafer in the z-axis direction based on the difference between the timing at which the temporal change of the light quantity on the detection wafer becomes the maximum value and the timing at which the light quantity becomes the maximum value in the reference data.

(Specification of tilt direction and size around x axis)
Next, a method of specifying the tilt of the wafer around the x-axis will be described. The transfer robot 4 moves the sensor hand 5 downward at a constant speed at a constant speed, and during that time, the sensor unit 3 acquires data on the change over time of the detection light received by the two

reflection sensors

67 and 68 for the detection wafer. I do. The PLC 2 specifies the inclination direction and magnitude of the wafer around the x-axis by comparing data of the change over time in the amount of detection light received by the two left and right reflection sensors, that is, the

reflection sensors

67 and 68. Specifically, as shown in FIG. 13, when the timing at which the amount of received detection light reaches the maximum value is such that the left reflection sensor 67 is earlier than the right reflection sensor 68, the PLC 2 Identifies that it is rising to the left, that is, leaning to the right. Conversely, if the point at which the amount of light reaches a peak is earlier than the reflection sensor 66, the PLC 2 specifies that the wafer is tilted to the left, that is, the wafer is tilted to the right.

(4) The difference L between the timings at which the amounts of the detection light received by the

reflection sensors

67 and 68 reach the maximum value is proportional to the inclination of the wafer. Therefore, the PLC 2 specifies the magnitude of the inclination of the wafer around the x-axis by measuring the difference L between the timings at which the amount of light reaches the maximum value by the

reflection sensors

67 and 68.

(Specification of direction and magnitude of tilt around y-axis)
Next, a method of specifying the direction and magnitude of the tilt of the wafer around the y-axis will be described. (The front reflection sensor 69 is provided on the x-axis direction front side of the left and right reflection sensors 67 and 68). The transfer robot 4 moves the sensor hand 5 downward at a constant speed at a constant speed, and during this time, the sensor unit 3 detects the change over time of the detection light received by the reflection sensor 67 (or 68) and the reflection sensor 69 for the detection wafer. Get the data. The PLC 2 compares the acquired data of the change over time in the amount of the detection light received by the reflection sensor 67 (or 68) and the reflection sensor 68, and specifies the tilt direction and the size of the wafer around the y-axis. . The front reflection sensor 69 is provided on the x-axis direction front side of the left and

right reflection sensors

67 and 68. Therefore, as shown in FIG. 14, when the timing at which the amount of detection light reaches the maximum value is earlier than the reflection sensor 69 in the reflection sensor 67 (or 68), the PLC 2 moves the wafer forward, Identify the wafer as leaning forward. Conversely, if the timing at which the amount of detected light reaches the maximum value is after the reflection sensor 69 on the front side is higher than the reflection sensor 67 (or 68), the PLC 2 moves the wafer forward, that is, moves the wafer backward. Identify that it is leaning.

In addition, the PLC 2 determines the magnitude L of the difference between the timings at which the amount of the detected light reaches the maximum value using the reflection sensor 67 (68) and the reflection sensor 69, thereby reducing the magnitude of the inclination of the wafer around the y-axis. Identify.

(Other Examples)
The technology described in the present specification is not limited to the sensor configuration described above. For example, the sensor hand may include two pairs of transmission sensors and one reflection sensor. The sensor hand includes two pairs of transmission sensors arranged in the x-axis direction of the wafer such that transmitted light is parallel. With this configuration, the inclination of the wafer can be specified with higher accuracy.

§4 Modification (Modification 1)
In the above embodiment, as illustrated in FIG. 9, an example in which the control unit 21 of the PLC 2 includes the inclination detection unit 211 as a functional configuration has been described. Instead of this configuration, the control unit (not shown) of the sensor unit 3 may include a tilt detection unit 211 as a functional configuration.

(Modification 2)
In the above embodiment, as illustrated in FIG. 1, an example in which the sensor system 1 includes only one combination of the sensor unit 3, the transfer robot 4, the chuck 5, and the photoelectric sensor 6 has been described. However, the sensor system 1 may have a plurality of the combinations.

(Modification 3)
In the above embodiment, as illustrated in FIG. 4, an example has been described in which the sensor system 1 scans one wafer 10 and specifies the direction and angle of inclination of the wafer 10. Instead of this configuration, the sensor system 1 scans a plurality of wafers 10 (for example, all the wafers 10 stored in the wafer cassette 20) collectively and specifies the direction and angle of inclination of each wafer 10. You may.

(Modification 4)
In the above embodiment, as illustrated in FIG. 10 and the like, an example in which the sensor system 1 specifies the direction and angle of the tilt of the wafer 10 has been described. However, the configuration in which the sensor system 1 specifies the inclination angle of the wafer 10 is not essential. In other words, the sensor system 1 may specify only the direction of the tilt of the wafer 10.

(Modification 5)
In the above embodiment, an example in which the sensor system 1 controls the tilt direction, angle, and z-axis position of the chuck 7 in accordance with the specified tilt direction, angle, and displacement amount in the z-axis direction of the wafer 10 is described. explained. Instead of this configuration or in addition to this configuration, when the specified tilt angle of the wafer 10 is equal to or more than a certain value, the sensor system 1 may include a configuration that notifies the user of the sensor system 1 of the fact. Good.

FIG. 11 is a diagram schematically illustrating an example of a hardware configuration of each device included in the sensor system 1a according to the sixth modification. As shown in FIG. 11, the sensor system 1a differs from the sensor system 1 in that the sensor system 1a includes a PLC 2a instead of the PLC 2, and that the alarm system 7 is newly included.

The notification device 7 is a device that notifies the user of the sensor system 1 and may be, for example, a display device (display). In the case of this example, the notification device 7 notifies the user that the angle of inclination of the wafer 10 is equal to or greater than a certain value, in other words, the wafer 10 may be damaged when the wafer 10 is removed from the wafer cassette 20. Display a warning screen.

PLC2a is different from PLC2 in that an output interface 24 is newly provided. The output interface 24 is an interface for the PLC 2a to output data. In this modified example, the PLC 2a outputs information for performing notification to the user (for example, display information for displaying the screen) to the notification device 7 via the output interface 24.

The control unit 21 according to the present modification includes a display control unit (not shown) as a functional configuration. The tilt detection unit 211 according to the present modification determines whether or not the specified tilt angle of the wafer 10 is equal to or greater than a certain value. If the tilt angle is equal to or greater than the certain value, the display information generation instruction is sent to the display control unit. Output. The display control unit receives the generation instruction, generates display information, and outputs the display information to the notification device 7 via the output interface 24.

Accordingly, the sensor system 1a can notify a user (for example, an operator) of the sensor system 1a that the wafer 10 may be damaged.

[Summary]
In order to solve the above-described problem, a sensor system according to one embodiment of the present invention is a sensor system that detects an inclination of a wafer stored in a wafer cassette, and includes three or more photoelectric sensors and the three or more photoelectric sensors. Is moved in a direction perpendicular to the plane of the normally accommodated wafer while the plane including the three or more photoelectric sensors is parallel to the plane of the wafer normally accommodated. Movement control device, during the movement of the photoelectric sensor, an acquisition device that acquires the amount of light received by the photoelectric sensor, based on the change in the amount of light during the period when the photoelectric sensor is detecting the detection target wafer, A specification device for specifying the direction of the tilt of the wafer and the magnitude of the tilt of the wafer.

Note that as the “direction of inclination”, among the points forming the outer periphery of the wafer, the direction from the highest point to the lowest point with respect to the horizontal plane may be specified. In this specification, the “vertical direction” is a direction perpendicular to the plane of a normally stored wafer (that is, the vertical direction), and the “left-right direction” of the wafer is normally stored. A direction parallel to the plane of the wafer and connecting two points where the wafer is gripped by a transfer chuck or the like. The “front-back direction” of a wafer refers to a direction that is parallel to the plane of a normally stored wafer and that is orthogonal to the “left-right direction”.

According to the above configuration, while the photoelectric sensor is detecting the detection target wafer, the amount of displacement of the wafer in the vertical direction and the inclination in the horizontal direction are determined based on the change in the amount of light received by the three or more photoelectric sensors. More detailed information on the inclination of the wafer, such as the size of the wafer and the magnitude of the inclination in the front-back direction, can be obtained. Thus, the sensor system can specify more detailed information than the presence or absence of the inclination.

In the sensor system according to one embodiment of the present invention, two of the three or more photoelectric sensors are a pair of transmission-type sensors provided so that detection light passes through two points on an arc that forms the outer periphery of the wafer. It may be a sensor.

According to the above configuration, more detailed information on the tilt of the wafer can be specified by the pair of transmission sensors. In this specification, a pair of transmission sensors including a light projecting unit and a light receiving unit is counted as two photoelectric sensors.

In the sensor system according to one embodiment of the present invention, the three or more photoelectric sensors are further provided such that a position other than the two points is a detection region on an arc forming an outer periphery of the wafer. A plurality of reflective sensors may be included.

According to the above configuration, by combining a pair of a transmission type sensor and a reflection type sensor, it is possible to specify more precise and detailed information on the tilt of the wafer.

In the sensor system according to one embodiment of the present invention, one or a plurality of reflection-type sensors are positions on an arc forming the outer periphery of the wafer other than the two points, and a center point of a straight line connecting the two points. It may include two reflection sensors provided such that a position symmetrical with respect to a straight line passing through the center point of the wafer is a detection area.

According to the above configuration, by combining a pair of transmissive sensors and two or more reflective sensors, it is possible to more precisely specify detailed information on the tilt of the wafer.

In the sensor system according to an aspect of the present invention, the transfer device for transferring the wafer, further includes a transfer device having a chuck for taking out the wafer from the wafer cassette, the specific device, the specified device, The inclination of the chuck may be controlled according to the inclination and angle of the wafer.

According to the above configuration, the tilt of the chuck is controlled in accordance with the tilt, the angle, and the displacement in the z-axis direction of the wafer specified by the specifying device. Therefore, even if the wafer is tilted, the wafer cassette is not damaged. Can be taken from Therefore, even when the wafer is tilted, the transfer can be continued.

According to another aspect of the present invention, there is provided a tilt detection method using a sensor system for detecting a tilt of a wafer housed in a wafer cassette, wherein the sensor system comprises: Is provided with three or more photoelectric sensors, and the three or more photoelectric sensors are normally placed in a state in which a plane including the three or more photoelectric sensors is parallel to the plane of the wafer in which the plane is normally accommodated. A moving step of moving the stored wafer in a direction perpendicular to the plane of the wafer, an obtaining step of obtaining the amount of light received by the light receiving unit during the moving step, and the photoelectric sensor detects a wafer to be detected. Specifying a direction of the tilt of the wafer and a magnitude of the tilt of the wafer based on a change in the amount of light during the period.

According to the above configuration, the same operation and effect as those of the sensor system according to one embodiment of the present invention can be obtained.

The present invention is not limited to the above-described embodiments and modified examples, and various modifications are possible within the scope shown in the claims, and are obtained by appropriately combining technical means disclosed in different embodiments. Embodiments are also included in the technical scope of the present invention.

1,

1a Sensor system

2, 2a PLC (specific device)
3 Sensor unit (acquisition device)
4 Transfer robot (transportation device, movement control device)
Reference Signs List 5 sensor hand 6 photoelectric sensor 7 transfer chuck 8 actuator 9 notification device 10 wafer 20 wafer cassette 60 detection light 61a light projecting unit 61b light receiving unit
62, 63

Reflection sensor

65, 66

Projection

67, 68, 69 Reflection sensor 101 Wafer surface (plane of wafer)
S1 Movement step S2, S3 Acquisition step S6 Identification step

Claims

A sensor system for detecting a tilt of a wafer stored in a wafer cassette,
Three or more photoelectric sensors,
The three or more photoelectric sensors are perpendicular to the plane of the normally accommodated wafer while the plane including the three or more photoelectric sensors is parallel to the plane of the normally accommodated wafer. A movement control device for moving in the direction,
An acquisition device that acquires the amount of light received by the photoelectric sensor during movement of the photoelectric sensor,
The photoelectric sensor, based on the change in the amount of light during the detection of the detection target wafer, based on the direction of the tilt of the wafer, and a specifying device that specifies the magnitude of the tilt of the wafer,
A sensor system comprising:
2. The sensor according to claim 1, wherein two of the three or more photoelectric sensors are a pair of transmission sensors provided so that the detection light passes through two points on an arc forming the outer periphery of the wafer. 3. Sensor system.
The three or more photoelectric sensors further include one or a plurality of reflection sensors provided such that positions other than the two points are detection areas on an arc forming an outer periphery of the wafer. 3. The sensor system according to 2.
The one or more reflective sensors are located on a circular arc forming the outer periphery of the wafer other than the two points, and are formed as straight lines passing through the center point of a straight line connecting the two points and the center point of the wafer. 4. The sensor system according to claim 3, further comprising two reflection sensors provided such that a position symmetrical with respect to the detection region is a detection area. 5.
The sensor system is a transfer device for transferring the wafer, further comprising a transfer device having a chuck for taking out the wafer from the wafer cassette,
The sensor system according to claim 1, wherein the specifying device controls the tilt of the chuck according to the specified tilt and angle of the wafer.
A tilt detection method using a sensor system that detects a tilt of a wafer stored in a wafer cassette,
The sensor system includes three or more photoelectric sensors,
The three or more photoelectric sensors are perpendicular to the plane of the normally accommodated wafer while the plane including the three or more photoelectric sensors is parallel to the plane of the normally accommodated wafer. A moving step for moving in the direction;
During the moving step, an acquiring step of acquiring the amount of light received by the photoelectric sensor,
A step of specifying the direction of the tilt of the wafer and the magnitude of the tilt of the wafer based on a change in the amount of light during a period in which the photoelectric sensor is detecting the detection target wafer. Method.