JP2019149478A - Sensor system and tilt detecting method - Google Patents

Abstract

To specify detailed information on a tilt of a wafer from whether the wafer tilts.SOLUTION: A sensor system (1) comprises a PLC (2) which specifies a tilt direction of a wafer (10) as an object of detection based upon change in quantity of light in a period in which a photoelectric sensor (6) is detecting the wafer (10).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sensor system that detects an inclination of a wafer stored in a wafer cassette using a photoelectric sensor.

  A technique for projecting detection light onto a wafer while moving a photoelectric sensor and detecting the tilt of a wafer stored in a wafer cassette based on the amount of received detection light is known as a prior art. In Patent Document 1 below, it is determined whether or not there is a peak of the amount of light received that exceeds a predetermined threshold value outside the vicinity of the wafer storage unit in the wafer cassette. A technique for determining that an abnormality such as insertion has occurred is disclosed.

JP 2000-150624 A (published on May 30, 2000)

  However, the technique disclosed in Patent Document 1 can only determine whether or not the wafer is tilted. In other words, with this technique, the user cannot know detailed information about the tilt.

  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 problems, a sensor system according to an aspect of the present invention is a sensor system that detects the tilt of a wafer stored in a wafer cassette, and a light projecting unit that projects detection light, and The photoelectric sensor having a light receiving unit that receives the detection light projected by the light projecting unit, and a direction in which the detection light travels parallel to a plane of the wafer that is normally stored, A movement control device that moves the sensor in a direction perpendicular to the traveling direction of the detection light, an acquisition device that acquires the amount of light received by the light receiving unit during the movement of the photoelectric sensor, and the photoelectric sensor And a specifying device for specifying the direction of tilt of the wafer based on the change in the amount of light during the period in which the wafer is detected.

  According to said structure, the direction of the inclination of a wafer is specified based on the change of the light quantity which the light-receiving part received during the period which the photoelectric sensor is detecting the detection object wafer. Thereby, the sensor system can specify more detailed information than the presence or absence of tilt.

  As the “inclination direction”, a direction from the uppermost point to the lowermost point with respect to the horizontal plane may be defined among the points forming the outer periphery of the wafer.

  In the sensor system according to the above aspect, the specifying device may further specify an inclination angle of the wafer based on the change in the light amount.

  According to the above configuration, the angle of inclination is specified in addition to the direction of inclination of the wafer. Thereby, the sensor system can specify more detailed information regarding the tilt of the wafer.

  In the sensor system according to the above aspect, the apparatus further includes a transfer device for transferring the wafer, the transfer device including a chuck for taking out the wafer from the wafer cassette, and the specifying device is configured to transfer the specified wafer. The inclination of the chuck may be controlled according to the inclination and angle.

  According to the above configuration, since the tilt of the chuck is controlled according to the tilt and angle of the wafer specified by the specific device, the wafer can be taken out from the wafer cassette without being damaged even if the wafer is tilted. Therefore, even if the wafer is tilted, the conveyance can be continued.

  In the sensor system according to the above aspect, the movement control device may be the transport device, and the photoelectric sensor may be provided at a tip of the chuck.

  According to the above configuration, since the photoelectric sensor is provided at the tip of the chuck, the transfer device performs a process of projecting detection light onto the wafer while moving the photoelectric sensor. Therefore, when the wafer is not tilted, it is possible to smoothly remove the wafer from the wafer cassette and carry the wafer after detecting the tilt.

  The sensor system according to the one aspect includes a plurality of the photoelectric sensors in an axial direction that is perpendicular to the detection light and perpendicular to a movement direction of the photoelectric sensor by the movement control device. May be.

  When the direction of the inclination defined as described above is a direction perpendicular to the detection light and the moving direction of the photoelectric sensor, it cannot be specified by only one photoelectric sensor. On the other hand, according to the above configuration, since the plurality of photoelectric sensors are provided in the axial direction perpendicular to the moving direction of the detection light and the photoelectric sensor, the direction of such inclination can be specified.

  In order to solve the above problems, an inclination detection method according to an aspect 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, and the sensor system Is provided with a photoelectric sensor having a light projecting unit that projects detection light and a light receiving unit that receives the detection light projected by the light projecting unit, and the traveling direction of the detection light is stored normally. A moving step of moving the photoelectric sensor in a direction perpendicular to the traveling direction of the detection light in a state parallel to the plane of the wafer, and acquiring the amount of light received by the light receiving unit during the moving step And an identifying step for identifying a direction of tilt of the wafer based on a change in the amount of light during a period in which the photoelectric sensor is detecting a detection target wafer.

  According to said structure, there exists an effect similar to the sensor system which concerns on 1 aspect of this invention.

  According to one embodiment of the present invention, more detailed information can be specified regarding the tilt of a wafer than the presence or absence of the tilt.

It is a figure which illustrates typically an example of the hardware constitutions of each apparatus contained in the sensor system concerning one embodiment of the present invention. (A) is a figure which shows an example of a wafer, (b) is a figure which shows an example of irradiation of the detection light to a wafer for the detection of the inclination of a wafer, (c) is a figure which shows detection light It is a figure which shows an example of a time-dependent change of the light quantity. It is a figure which shows an example of the operation | movement which takes out a wafer from a wafer cassette by the conveyance robot shown in FIG. It is a figure which shows an example of the positional relationship of a wafer and the chuck | zipper shown in FIG. 1 and FIG. 3 in the inclination detection of a wafer. FIG. 2 is a diagram schematically illustrating an example of a functional configuration of a PLC illustrated in FIG. 1. It is a flowchart which shows an example of the procedure of the process which PLC shown in FIG. 1 performs. (A) is a figure which shows an example of irradiation of the detection light to a wafer, and is a figure which shows the case where a wafer inclines with the side close | similar to a light projection part down. (B) is a figure which shows an example of the time-dependent change of the light quantity of the detection light in case a wafer inclines as shown to (a). (A) is a figure which shows an example of irradiation of the detection light to a wafer, and is a figure which shows the case where a wafer inclines with the side near a light-receiving part down. (B) is a figure which shows an example of the time-dependent change of the light quantity of the detection light in case a wafer inclines as shown to (a). (A) And (b) is a figure which shows an example of irradiation of the detection light to a wafer, and is a figure which shows the case where the wafer inclines with the side close | similar to a photoelectric sensor facing down. (C) is a figure which shows an example of the time-dependent change of the light quantity of the detection light when a wafer inclines as shown to (a) and (b). (A) And (b) is a figure which shows an example of irradiation of the detection light to a wafer, and is a figure which shows the case where a wafer inclines with the side far from a photoelectric sensor facing down. (C) is a figure which shows an example of the time-dependent change of the light quantity of the detection light when a wafer inclines as shown to (a) and (b). It is a figure which illustrates typically an example of the hardware constitutions of each apparatus contained in the sensor system concerning one modification of the present invention.

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

§1 Application Example First, an example of a scene where the present invention is applied will be described with reference to FIGS. 1 and 2. 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 the tilt of a wafer stored in a wafer cassette.

  As shown in FIG. 1, the sensor system 1 includes a programmable logic controller (PLC) 2, a sensor unit 3, a transfer robot 4, a chuck 5, and a photoelectric sensor 6. Details of the PLC 2, the sensor unit 3, the transfer robot 4, and the chuck 5 will be described later. As shown in FIG. 1, the photoelectric sensor 6 includes a light projecting unit 61 and a light receiving unit 62, and is realized by a fiber sensor as an example. The light projecting unit 61 projects detection light. The light receiving unit 62 receives the detection light.

  2A is a diagram illustrating an example of a wafer, FIG. 2B is a diagram illustrating an example of irradiation of detection light onto the wafer for detecting the tilt of the wafer, and FIG. It is a figure which shows an example of the time-dependent change of the light quantity of a detection light. A wafer 10 shown in FIG. 2A has a cylindrical shape. Specifically, the wafer 10 has a wafer surface 101 (wafer plane) and an outer peripheral surface 102 as shown in FIG.

  As shown in FIG. 2B, the light projecting unit 61 and the light receiving unit 62 are arranged so as to sandwich the wafer 10. That is, the photoelectric sensor 6 according to the present embodiment is realized by a transmitted light detection type photoelectric sensor.

  As shown in FIG. 2B, the sensor system 1 operates in the state where the traveling direction of the detection light 60 is parallel to the wafer surface 101 of the wafer 10 that is normally stored, that is, The light unit 61 and the light receiving unit 62 are moved in a direction perpendicular to the traveling direction of the detection light 60. In the illustrated example, the photoelectric sensor 6 is moved from the top to the bottom in FIG. 2, but the moving direction may be opposite to the example shown in FIG. Further, as shown in FIG. 2B, the sensor system 1 controls the photoelectric sensor 6 so that the light projecting unit 61 continuously projects the detection light 60 while the photoelectric sensor 6 is moving. The light receiving unit 62 receives the detection light 60. Hereinafter, projecting and receiving the detection light 60 while moving the photoelectric sensor 6 is also referred to as “scan”.

  The temporal change in the amount of the detection light 60 received by the light receiving unit 62 becomes, for example, a locus shown in FIG. Before the point P1, since the detection light does not reach the wafer surface 101, the light amount of the detection light 60 received by the light receiving unit 62 is maximum. The detection light 60 is blocked by the wafer 10 when the detection light 60 reaches the upper wafer surface 101 in FIG. 2 between the points P1 and P2. For this reason, the amount of light decreases and reaches a minimum value at the point P2. By reaching the lower wafer surface 101 in FIG. 2 between the points P2 to P3, the amount of light increases and returns to the maximum value at the point P3.

  As shown in FIG. 2B, when the wafer surface 101 is parallel to the horizontal plane (in other words, the detection light 60), that is, when the wafer 10 is not tilted, the change in the amount of light of the detection light 60 with time is shown. The trajectory is the trajectory shown in FIG. On the other hand, when the wafer surface 101 is not parallel to the horizontal plane, that is, when the wafer 10 is inclined, the trajectory is different from the trajectory shown in FIG. Details of the different trajectories will be described later.

  The sensor system 1 specifies whether or not the wafer 10 is tilted and, if tilted, the direction and angle of tilt based on the change in the amount of light over time. Thereby, the sensor system 1 can specify more detailed information about the tilt of the wafer 10 than the presence or absence of the tilt.

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

§2 Configuration example [Hardware configuration]
<PLC>
Next, an example of the 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.

  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 included in the PLC 2 are electrically connected to each other via a communication bus. The PLC 2 according to the present embodiment corresponds to a “specific device” of the present invention.

  The control unit 21 includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and the like, and controls each component according to information processing. The storage unit 22 is an auxiliary storage device such as a hard disk drive or 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 PLC2, a component can be omitted, replaced, and added according to the embodiment. For example, the control unit 21 may include a plurality of processors.

<Transport robot>
Next, an example of the hardware configuration of the transfer robot 4 according to the present embodiment will be described with reference to FIGS. 1, 3, and 4. FIG. 3 is a diagram illustrating an example of an operation for taking out the wafer 10 from the wafer cassette by the transfer robot 4. FIG. 4 is a diagram illustrating an example of the positional relationship between the wafer 10 and the chuck 5 in detecting the tilt of the wafer 10.

  In the example of FIG. 1, the transfer robot 4 includes a chuck 5. As an example, the chuck 5 is a U-shaped (or Y-shaped) member as shown in FIG. Although not shown in FIG. 3, the base side of the chuck 5 is connected to the transfer robot 4. When the transfer robot 4 is controlled by the PLC 2, the chuck 5 is inserted below the wafer 10 stored in the wafer cassette 20 as shown in FIG. 3 and lifts the wafer 10. As a result, the wafer 10 is changed from being placed on the wafer cassette 20 to being placed on the chuck 5 and taken out from the wafer cassette 20. The transfer robot 4 is controlled by the PLC 2 and transfers the wafer 10 placed on the chuck 5. The transport robot 4 according to the present embodiment corresponds to a “transport device” of the present invention.

  In the example of FIG. 1, the chuck 5 includes a photoelectric sensor 6, that is, a light projecting unit 61 and a light receiving unit 62. As an example, the light projecting unit 61 and the light receiving unit 62 are provided at the tip of the chuck 5 as shown in FIG. For this reason, in this embodiment, the movement of the photoelectric sensor 6 is performed by the movement of the chuck 5 by the transfer robot 4. That is, the transfer robot 4 according to the present embodiment also corresponds to the “movement control device” of the present invention.

  Hereinafter, the portion of the chuck 5 where the light projecting unit 61 and the light receiving unit 62 are provided is also referred to as “hand”. In the example of FIG. 4, two light projecting units 61 are provided on one hand of the chuck 5, and two light receiving units 62 are provided on the other hand. In other words, the chuck 5 is provided with a plurality (two) of photoelectric sensors 6. The two photoelectric sensors 6 are perpendicular to the detection light 60 (see FIG. 4) and perpendicular to the moving direction of the photoelectric sensors 6 (see FIG. 2B), that is, 4 are arranged in the vertical direction.

  Hereinafter, the photoelectric sensor 6 provided on the tip side of the chuck 5 is also referred to as a first photoelectric sensor 6a. The light projecting unit 61 and the light receiving unit 62 of the first photoelectric sensor 6a are also referred to as a light projecting unit 61a and a light receiving unit 62a, as shown in FIG. On the other hand, the photoelectric sensor 6 provided on the transport robot 4 side of the chuck 5 is also referred to as a second photoelectric sensor 6b. The light projecting unit 61 and the light receiving unit 62 of the second photoelectric sensor 6b are also referred to as a light projecting unit 61b and a light receiving unit 62b.

  When the diameter of the wafer 10 is 200 mm as in the example shown in FIG. 4, as an example, the light projecting unit 61 a and the light receiving unit 62 a are detected at a position 70 mm from the center of the wafer surface 101 as shown in FIG. 4. It is provided at the position of the chuck 5 where the light 60a is irradiated. As an example, the light projecting unit 61b and the light receiving unit 62b are, as shown in FIG. 4, a predetermined position from a position 70 mm from the center of the wafer surface 101 to a position 100 mm (that is, the outer periphery of the wafer surface 101). Is provided at the position of the chuck 5 where the detection light 60b is irradiated.

  The light projecting unit 61a and the light receiving unit 62a, and the light projecting unit 61b and the light receiving unit 62b may be provided at the position of the chuck 5 where the detection light is irradiated to the wafer 10. The position shown in FIG.

  In the present embodiment, an example in which the light projecting unit 61 is provided at the tip of the left hand of the chuck 5 in FIG. 4 and the light receiving unit 62 is provided at the tip of the right hand will be described. However, the light receiving unit 62 may be provided at the tip of the left hand, and the light projecting unit 61 may be provided at the tip of the right hand. Further, one of the light projecting unit 61a of the first photoelectric sensor 6a and the light projecting unit 61b of the second photoelectric sensor 6b may be provided at the tip of the left hand and the other may be provided at the tip of the right hand. . With this configuration, the traveling directions of the detection light 60a and the detection light 60b are opposite to each other. Thereby, the situation where the light-receiving part 62b of the 2nd photoelectric sensor 6b light-receives the detection light 60a light-projected by the light projection part 61a of the 1st photoelectric sensor 6a can be prevented. Therefore, it is possible to prevent the occurrence of noise during light reception.

<Sensor unit 3>
The sensor unit 3 is controlled by the PLC 2 and controls the photoelectric sensor 6. Specifically, the sensor unit 3 controls the start and stop of the projection of the detection light 60 from the light projecting unit 61. More specifically, the sensor unit 3 causes the light projecting unit 61 to continuously project the detection light 60 while the photoelectric sensor 6 is moving. In addition, the sensor unit 3 acquires the light amount of the detection light 60 received by the light receiving unit 62, converts it to light amount data by A / D conversion, and transmits the light amount data to the PLC 2. The sensor unit 3 according to the present embodiment corresponds to an “acquiring 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. 5 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 an inclination detection unit 211 and a robot control unit 212 as functional configurations. Moreover, the memory | storage part 22 has memorize | stored the reference | standard data 221 at least as an example.

  The tilt detection unit 211 acquires the light amount data of the detection light 60 from the sensor unit 3, and the tilt of the wafer 10 is based on a change in light amount (time-dependent change) during a period in which the photoelectric sensor 6 detects the detection target wafer 10. Is identified. The “period in which the detection target wafer 10 is being detected” is a period in which the detection light 60 is irradiated on the wafer 10 (a period in which the photoelectric sensor 6 crosses the outer peripheral surface 102). The robot control unit 212 controls the transfer robot 4. Specifically, the robot control unit 212 controls the tilt of the chuck 5 in accordance with the wafer tilt specified by the tilt detection unit 211.

  The reference data 221 is data serving as a reference for the tilt of the wafer 10 used when the tilt detection unit 211 specifies the tilt of the wafer 10. As an example, the reference data 221 may be a temporal change in the amount of light when the wafer 10 is not tilted. In the case of this example, the reference data 221 may be a change with time of the light amount shown in FIG.

  As an example, the control unit 21 may execute the above process as the inclination detection unit 211 and the robot control unit 212 by executing an appropriate program. The program may be stored in the ROM as an example. In the case of this example, the control unit 21 expands the program stored in the ROM in the RAM. And the control part 21 interprets and executes the program expand | deployed by RAM by CPU, and controls each component of PLC2.

  The recording medium storing the program may be a tangible medium that is not temporary. A tape, a disk, a card, a semiconductor memory, a programmable logic circuit, or the like can be used in addition to the ROM. The program may be supplied to the PLC 2 via any transmission medium (communication network, broadcast wave, etc.) 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.

  Details of processing executed by the inclination 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 described as being realized by a general-purpose CPU. However, these may be realized by one or more dedicated processors. In addition, regarding the functional configuration of the PLC 2, the configuration may be omitted, replaced, and added as appropriate according to the embodiment.

§3 Operation Example Next, an operation example of the PLC 2 will be described with reference to FIG. FIG. 6 is a flowchart illustrating an example of the processing procedure of the PLC 2. In addition, the process procedure demonstrated below is an example, and there is no intention which limits the process procedure of PLC2 which concerns on this 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 causes the transfer robot 4 to start moving the chuck 5 in a direction perpendicular to the traveling direction of the detection light 60 (step S1, moving step). The process of step S <b> 1 is realized by the robot control unit 212 transmitting a control command to the transport robot 4 via the communication interface 23. Further, when the robot control unit 212 starts to move the chuck 5, the robot control unit 212 notifies the tilt detection unit 211 to that effect.

  Subsequently, upon receiving a notification from the robot control unit 212, the tilt detection unit 211 controls the sensor unit 3 to start projecting the detection light 60 from each light projecting unit 61 onto the wafer 10 (step S2). , Acquisition step). In the case of the example of the present embodiment, the sensor unit 3 causes the light projecting unit 61a to project the detection light 60a, and causes the light projecting unit 61b to project the detection light 60b. The process of step S <b> 2 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 amount of detection light received by each light receiving unit 62 (step S3, acquisition step). In the case of the example of the present embodiment, the sensor unit 3 acquires the light amount of the detection light 60a received by the light receiving unit 62a and the light amount of the detection light 60b received by the light receiving unit 62b. The sensor unit 3 converts the acquired light amount into light amount data, and temporarily stores the light amount in association with light receiving unit identification information for identifying the light receiving unit 62. When the sensor unit 3 receives a light amount data transmission instruction from the PLC 2, the sensor unit 3 transmits all the light amount data acquired at that time to the PLC 2 in association with the light receiving unit identification information.

  Subsequently, the inclination detection 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, the inclination detecting unit 211 determines whether or not the wafer 10 is inclined based on the comparison result (step S5).

(Identification of tilt)
Here, an example of details of the determination of whether or not the wafer 10 is tilted will be described with reference to FIGS. 2, 7, and 9. As described above, the reference data 221 in this example is a change with time in the amount of light shown in FIG. FIG. 7A is a diagram illustrating an example of irradiation of the detection light onto the wafer 10, and is a diagram illustrating a case where the wafer 10 is inclined with the side close to the light projecting unit 61 facing down. Hereinafter, the inclination of the wafer 10 shown in FIG. 7A is also referred to as “downward left”. FIG. 7B is a diagram illustrating an example of a change with time of the light amount of the detection light in the case of falling to the left.

  FIGS. 9A and 9B are diagrams illustrating an example of irradiation of the detection light onto the wafer 10, and a diagram illustrating a case where the wafer 10 is inclined with the side close to the photoelectric sensor 6 facing down. is there. FIG. 9C is a diagram illustrating an example of a change over time in the amount of detection light when the wafer 10 is inclined with the side close to the photoelectric sensor 6 facing down.

  Hereinafter, the fact that the wafer 10 tilts with the light projecting unit 61 side or the light receiving unit 62 side down is also referred to as “tilt in the left-right direction”. In addition, the fact that the wafer 10 is tilted with the side close to the photoelectric sensor 6 or the side far from the photoelectric sensor 6 is also referred to as “tilt in the front-rear direction”.

  First, determination of whether or not the wafer 10 is tilted in the left-right direction will be described. Note that the method described below is merely an example, and there is no intention to limit the method of determining whether or not it is tilted in the left-right direction to the method described below. When the wafer 10 is not tilted in the left-right direction, the temporal change in the amount of light received by the PLC 2 is substantially the same as the temporal change shown in FIG. 2C during the period in which the photoelectric sensor 6 is detecting the detection target wafer 10. Match. In other words, the difference between the generated light amount with time and the reference data 221 is small.

  On the other hand, as shown in FIG. 7A, when the wafer 10 is tilted in the left-right direction, the temporal change in the amount of light generated by the PLC 2 is as shown in FIG. This is different from the time-dependent change shown in 2 (c). In other words, there is a large difference between the change in the amount of light generated with time and the reference data 221.

  For this reason, the inclination detection unit 211 determines whether or not the difference between the generated light amount with time and the reference data 221 is greater than or equal to a predetermined value during the period. If it is determined that the value is equal to or greater than the predetermined value, the tilt detection unit 211 determines that the wafer 10 is tilted in the left-right direction. On the other hand, when it is determined that the value is less than the predetermined value, the inclination detection unit 211 determines that the wafer 10 is not inclined in the left-right direction.

  Specifically, the inclination detection unit 211 calculates a coincidence rate when the change over time of the generated light amount and the reference data 221 are superimposed, and determines whether the coincidence rate is equal to or greater than a predetermined value. May be. As this predetermined value, a coincidence rate when the wafer 10 is tilted to a certain extent that the chuck 5 may come into contact with the wafer 10 when the wafer 10 is taken out from the wafer cassette 20 is calculated in advance, and the coincidence rate is used. That's fine.

  As described above, the method for determining whether or not the wafer 10 is tilted in the left-right direction is not limited to this example. For example, the inclination detection unit 211 may determine whether or not the change with time in the above period is line-symmetric with respect to a straight line that is perpendicular to the time axis and passes through the point of the minimum light amount. As shown in FIG. 2C, when the wafer 10 is not tilted in the left-right direction, the change over time in the period is axisymmetric in the straight line. On the other hand, as shown in FIG. 7B, when the wafer 10 is inclined in the left-right direction, the line is not line symmetric. For this reason, the inclination detection unit 211 determines that the wafer 10 is inclined in the left-right direction when the line is not symmetrical. On the other hand, when it becomes line symmetrical, it determines with the wafer 10 not inclining in the left-right direction.

  By using such a determination method, it is not necessary to store the reference data 221 in advance. In addition, the inclination detection part 211 does not need to be a structure which determines whether it is completely line symmetrical. That is, when the change with the passage of time is bent along the straight line, the inclination detection unit 211 has a coincidence rate between a decrease part of the light amount from the maximum value to the minimum value and an increase part from the minimum value to the maximum value is a predetermined value or more. In some cases, it may be determined that the line is symmetrical. The predetermined value may be the minimum value of the matching rate when the wafer 10 is not tilted.

  Next, determination of whether or not the wafer 10 is tilted in the front-rear direction will be described. Note that the method described below is merely an example, and there is no intention to limit the method of determining whether or not the vehicle is tilted in the front-rear direction to the method described below. When the wafer 10 is tilted in the front-rear direction, as shown in FIGS. 9A and 9B, one of the detection light 60 a and the detection light 60 b is first applied to the wafer surface 101 of the wafer 10. To reach. For this reason, as shown in FIG. 9C, one of the temporal change of the light amount in the first photoelectric sensor 6a and the temporal change of the light amount in the second photoelectric sensor 6b starts to decrease first.

  On the other hand, although not shown, when the wafer 10 is not tilted in the front-rear direction, the detection light 60 a and the detection light 60 b reach the wafer surface 101 at the same time. For this reason, the temporal change in the amount of light in the first photoelectric sensor 6a and the temporal change in the amount of light in the second photoelectric sensor 6b begin to decrease at the same timing.

  For this reason, the inclination detection unit 211 determines whether or not the temporal change of the light amount in the first photoelectric sensor 6a and the temporal change of the light amount in the second photoelectric sensor 6b are starting to decrease simultaneously. If it is determined that it has not started to decrease at the same time, the inclination detector 211 determines that the wafer 10 is inclined in the front-rear direction. On the other hand, when it is determined that the decrease starts simultaneously, the inclination detection unit 211 determines that the wafer 10 is not inclined in the front-rear direction.

  If the tilt detection unit 211 determines that the wafer 10 is tilted in either the left-right direction or the front-rear direction, the tilt detection unit 211 determines that the wafer 10 is tilted.

  Returning to the description of the operation example with reference to FIG. 6 again. When it is determined that the wafer 10 is tilted (YES in step S5), the tilt detection unit 211 identifies the tilt direction and angle of the wafer 10 (steps S6 and S7, identifying step).

(Identify the direction of tilt)
Here, an example of the details of specifying the tilt direction of the wafer 10 will be described with reference to FIGS. FIG. 8A is a diagram illustrating an example of irradiation of the detection light onto the wafer 10, and is a diagram illustrating a case where the wafer 10 is tilted in the opposite direction to FIG. 7A. Hereinafter, the inclination of the wafer 10 shown in FIG. 8A is also expressed as “downward to the right”. FIG. 8B is a diagram illustrating an example of a change with time of the light amount of the detection light in the case of the lower right.

  Note that the wafer 10 shown in FIG. 7A can also be expressed as being tilted leftward, and the wafer 10 shown in FIG. 8A can be expressed as being tilted rightward. it can.

  FIGS. 10A and 10B are diagrams illustrating an example of irradiation of the detection light onto the wafer 10, and a diagram illustrating a case where the wafer 10 is inclined with the side far from the photoelectric sensor 6 facing down. is there. FIG. 10C is a diagram illustrating an example of a change over time in the amount of detection light when the wafer 10 is inclined with the side far from the photoelectric sensor 6 facing down.

  Note that the wafer 10 shown in FIGS. 9A and 9B can be expressed as being tilted forward, and the wafer 10 shown in FIGS. 10A and 10B is backward. It can also be expressed as tilted.

  First, a method for specifying which of the left and right directions is inclined will be described. In addition, the method described below is an example, and the method for specifying which direction is tilted to the left or right is not intended to be limited to the method described below. As shown in FIGS. 7B and 8B, the shape of the temporal change in the amount of light varies depending on whether the direction of tilt of the wafer 10 is the left direction or the right direction. The inclination detection unit 211 specifies whether the wafer 10 is inclined in the left or right direction by specifying the difference in shape.

  Specifically, as shown in FIG. 7B, when the direction of the inclination of the wafer 10 is the left direction, the decreasing portion from the maximum value to the minimum value of the light amount, that is, between the points P4 to P5, After the amount of light decreases rapidly, it decreases gradually. In other words, the locus between the points P4 to P5 becomes a downwardly convex curve in FIG. On the other hand, in the increasing portion from the minimum value to the maximum value of the light amount, that is, between the points P5 to P6, the light amount increases slowly after increasing rapidly. In other words, the trajectory between the points P5 to P6 is a curved line convex upward in FIG.

  This is because when the direction of tilt of the wafer 10 is the left direction, the detection light 60 starts to be blocked at a position close to the light receiving unit 62. Although light diffusion occurs due to the start of light shielding, the diffused light is difficult to be received by the light receiving unit 62 because of diffusion at a position close to the light receiving unit 62. Therefore, the amount of light suddenly decreases from the maximum value. On the other hand, as the movement of the photoelectric sensor 6 proceeds, light diffusion occurs at a position close to the light projecting unit 61. Since this is diffusion at a position far from the light receiving unit 62, the diffused light is easily received by the light receiving unit 62. Therefore, the light quantity increases rapidly from the minimum value.

  On the other hand, as shown in FIG. 8B, when the direction of the inclination of the wafer 10 is the right direction, the amount of light suddenly decreases after the light amount gradually decreases in the above-described reduced portion, that is, between the points P7 to P8. To decrease. In other words, the trajectory between the points P7 to P8 becomes a curved line convex upward in FIG. On the other hand, in the increased portion, that is, between the points P8 to P9, the light amount increases rapidly after increasing gently. In other words, the locus between the points P8 to P9 is a curved line that protrudes downward in FIG.

  This is because when the wafer 10 is tilted in the right direction, the detection light 60 starts to be blocked at a position close to the light projecting unit 61. Since diffusion at a position far from the light receiving unit 62 occurs, the diffused light is easily received by the light receiving unit 62. Therefore, the amount of light gradually decreases from the maximum value. On the other hand, as the movement of the photoelectric sensor 6 proceeds, light diffusion occurs at a position close to the light receiving unit 62. Since this light is not easily received by the light receiving unit 62, the amount of light gradually increases from the minimum value.

  Unlike the example of the present embodiment, when the light projecting unit 61 is in the right hand of the chuck 5 and the light receiving unit 62 is in the left hand of the chuck 5, the inclination direction of the wafer 10 and the magnitude of the change are The relationship is reversed. That is, when the inclination of the wafer 10 is in the left direction, the locus of the decreasing portion is a curved curve convex upward in FIG. 7, and the locus of the increasing portion is a curved curve convex downward in FIG. On the other hand, when the inclination of the wafer 10 is rightward, the locus of the decreased portion is a downward convex curve in FIG. 8, and the locus of the increased portion is an upward convex curve in FIG.

  For example, when the inclination detecting unit 211 specifies that the decreasing portion of the change in the light amount with time is convex downward, the inclination detecting unit 211 specifies that the wafer 10 is inclined leftward, and the decreasing portion is convex upward. , It may be specified that the wafer 10 is tilted to the right. Alternatively, when the inclination detection unit 211 specifies that the increasing part of the change in the amount of light with time is convex upward, the inclination detecting part 211 specifies that the wafer 10 is inclined leftward, and the increasing part is convex downward. When specified, the wafer 10 may be specified as being tilted to the right.

  Alternatively, the tilt detection unit 211 specifies that the wafer 10 is tilted leftward when the decrease portion is convex downward and the increase portion is convex upward, and the decrease portion is upward. If it is convex and the increased portion is convex downward, it may be specified that the wafer 10 is tilted to the right. By specifying with the method of this example, a specific system improves compared with the specifying method of the two examples mentioned above.

  Next, a method for specifying which direction is inclined in the front-rear direction will be described. In addition, the method described below is an example, and the method for specifying which direction is inclined in the front-rear direction is not intended to be limited to the method described below. As shown in FIG. 9B, when the wafer 10 is tilted forward, the detection light 60a projected from the light projecting unit 61a is ahead of the detection light 60b projected from the light projecting unit 61b. The wafer surface 101 of the wafer 10 is reached. For this reason, as shown in FIG. 9C, the temporal change in the light amount in the first photoelectric sensor 6a starts to decrease before the temporal change in the light amount in the second photoelectric sensor 6b.

  On the other hand, as shown in FIG. 10B, when the tilt of the wafer 10 is in the backward direction, the detection light 60b reaches the wafer surface 101 before the detection light 60a. For this reason, as shown in FIG. 10C, the temporal change in the amount of light in the second photoelectric sensor 6b starts to decrease before the temporal change in the amount of light in the first photoelectric sensor 6a.

  The inclination detection unit 211 specifies which of the temporal change of the light quantity in the first photoelectric sensor 6a and the temporal change of the light quantity in the second photoelectric sensor 6b starts to decrease first, so that the inclination of the wafer 10 is increased. Specify whether it is a direction or a backward direction. When the inclination detection unit 211 specifies that the temporal change in the amount of light in the first photoelectric sensor 6a starts to decrease before the temporal change in the amount of light in the second photoelectric sensor 6b, the inclination detection unit 211 specifies that the inclination of the wafer 10 is in the forward direction. To do. On the other hand, when the inclination detection unit 211 determines that the temporal change of the light amount in the second photoelectric sensor 6b starts to decrease before the temporal change of the light amount in the first photoelectric sensor 6a, the inclination of the wafer 10 is backward. Is identified.

(Identification of tilt angle)
Next, an example of the details of specifying the tilt angle of the wafer 10 will be described with reference to FIGS.

  First, an example of specifying the angle in the horizontal tilt will be described. First, the inclination detecting unit 211 specifies a straight line passing through the maximum value point and the minimum value point in a decreasing portion of the light amount with time (see FIG. 7B and FIG. 8B). Then, the point farthest from the straight line is specified among the points of the reduced portion, and the distance from the straight line to the specified point is specified. This distance can also be expressed as the length of a line segment that is a perpendicular to the specified straight line and connects the specified point to a point on the straight line.

  Then, the inclination detecting unit 211 refers to a first database (not shown) that is stored in the storage unit 22 and associates the distance with the inclination angle of the wafer 10, and is associated with the identified distance. The inclination angle of the wafer 10 is specified.

  Note that the method for specifying the angle of inclination in the left-right direction is not limited to this example. For example, the inclination detection unit 211 specifies the inclination angle of the wafer 10 by referring to the first database by performing the distance specification in place of the decrease part or in the increase part together with the decrease part. Also good. In the example in which the distance is specified in both the decrease portion and the increase portion, when the angle specified from the distance in the decrease portion is different from the angle specified from the distance in the increase portion, the inclination detection unit 211. As an example, an average value of two angles may be set as an inclination angle.

  Further, as another method for specifying the angle of inclination in the left-right direction, the inclination detection unit 211 determines the maximum amount of light that is the end point of the increasing portion from the point of the maximum amount of light that is the starting point of the decreasing portion. You may specify the width to a point. The width is a period during which the photoelectric sensor 6 detects the detection target wafer 10. In the case of this example, the inclination detection unit 211 refers to a second database (not shown) stored in the storage unit 22 that associates the width with the inclination angle of the wafer 10 and corresponds to the specified width. The inclination angle of the attached wafer 10 is specified.

  This another method may be performed in place of the above-described method of specifying the tilt angle of the wafer 10 with reference to the first database, or may be performed together with this method. In the example performed together with the method, when the angle specified with reference to the first database is different from the angle specified with reference to the second database, the inclination detection unit 211, as an example, calculates the average of the two angles. The value may be an angle of inclination.

  Next, an example of specifying the angle in the tilt in the front-rear direction will be described. First, the inclination detecting unit 211 specifies a deviation width of a specific point in the temporal change of two light quantities (see FIG. 9C and FIG. 10C). The specific point may be a point indicating a minimum value of the light amount, for example. Note that the shift width is the length of a line segment connecting specific points.

  Then, the inclination detecting unit 211 refers to a third database (not shown) in which the deviation width and the inclination angle of the wafer 10 are associated with each other, and is associated with the identified deviation width. The angle of inclination of the wafer 10 is specified.

  Returning to the description of the operation example with reference to FIG. 6 again. The tilt detection unit 211 outputs the specified tilt direction and angle of the wafer 10 to the robot control unit 212. The robot control unit 212 controls the tilt of the chuck 5 according to the acquired tilt direction and angle of the wafer 10 (step S8). Specifically, the robot control unit 212 determines the tilt direction and angle of the chuck 5 according to the acquired tilt direction and angle of the wafer 10. Then, the robot control unit 212 transmits a control command including the determined tilt direction and angle of the chuck 5 to the transfer robot 4 via the communication interface 23. Thereby, the transfer robot 4 can adjust the direction and angle of the inclination of the chuck 5 in accordance with the direction and angle of the inclination of the wafer 10.

  Finally, the transfer robot 4 takes out the wafer 10 from the wafer cassette 20 (step S9) and transfers it. The processing in 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.

  Note that if the tilt detection unit 211 determines that the wafer 10 is not tilted (NO in step S5), steps S6 to S8 are omitted. That is, since the wafer 10 is not inclined, the PLC 2 causes the transfer robot 4 to take out the wafer 10 without adjusting the inclination direction and angle of the chuck 5 (step S9).

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

  As an example, the PLC 2 can adjust the tilt direction and angle of the chuck 5 based on the tilt direction and angle of the wafer 10 identified in step S8. Thereby, even if the wafer 10 is inclined, the wafer 10 can be taken out from the wafer cassette 20 without being damaged. Therefore, even if 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 or the case where the wafer cassette 20 itself is tilted.

§4 Modification (Modification 1)
In the above embodiment, as illustrated in FIG. 5, the 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 an inclination detection unit 211 as a functional configuration.

(Modification 2)
In the above embodiment, as illustrated in FIG. 1, the example in which the sensor system 1 has 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 such combinations.

(Modification 3)
In the embodiment described above, as illustrated in FIGS. 7 to 10 and the like, the sensor system 1 scans one wafer 10 and specifies an inclination direction and an angle 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 inclination direction and angle of each wafer 10. May be.

(Modification 4)
In the above embodiment, as illustrated in FIG. 4 and the like, the sensor system 1 includes the two photoelectric sensors 6, and the example in which the direction and angle of the front and rear tilt of the wafer 10 are specified has been described. However, the configuration in which the sensor system 1 includes the plurality of photoelectric sensors 6 is not essential. In other words, the sensor system 1 may include only one photoelectric sensor.

(Modification 5)
In the above-described embodiment, as illustrated in FIG. 6 and the like, an example in which the sensor system 1 specifies the tilt direction and angle of the wafer 10 has been described. However, the configuration in which the sensor system 1 specifies the tilt angle of the wafer 10 is not essential. In other words, the sensor system 1 may specify only the direction of tilt of the wafer 10.

(Modification 6)
In the above embodiment, as shown in FIGS. 1 and 3, the example in which the photoelectric sensor 6 is provided in the chuck 5 and the photoelectric sensor 6 moves as the chuck 5 moves under the control of the transfer robot 4 has been described. However, the photoelectric sensor 6 may move by a method different from the movement of the chuck 5. In other words, the movement control device that moves the photoelectric sensor 6 may be a device different from the transfer robot 4.

(Modification 7)
In the above embodiment, the example in which the sensor system 1 controls the tilt direction and angle of the chuck 5 according to the specified tilt direction and angle of the wafer 10 has been described. Instead of this configuration, or in addition to this configuration, the sensor system 1 may be configured to notify the user of the sensor system 1 when the specified tilt angle of the wafer 10 is greater than or equal to a certain level. 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 Modification 7. The sensor system 1a differs from the sensor system 1 in that a PLC 2a is included instead of the PLC 2 and a notification device 7 is newly included, as shown in FIG.

  The notification device 7 is a device that notifies the user of the sensor system 1, and may be a display device (display) as an example. In 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 taken out from the wafer cassette 20. A warning screen is displayed.

  The difference between the PLC 2a and the PLC 2 is that an output interface 24 is newly provided. The output interface 24 is an interface for the PLC 2a to output data. In this modification, the PLC 2a outputs information (for example, display information for displaying the screen) to notify the user to the notification device 7 via the output interface 24.

  Moreover, the control part 21 which concerns on this modification is provided with a display control part (not shown) as a function structure. The tilt detection unit 211 according to this 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 a certain value, the display control unit is instructed to generate the display information. 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.

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

  The present invention is not limited to the above-described embodiments and modifications, and various modifications are possible within the scope shown in the claims, and can be 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, specific device)
4 Transfer robot (movement control device, transfer device)
5 Chuck 6 Photoelectric Sensor 10 Wafer 20 Wafer Cassette 60 Detection Light 61 Light Emitting Unit
62 Light-receiving part 101 Wafer surface (plane of wafer)
S1 movement step S2, S3 acquisition step S6 identification step

Claims (6)

A sensor system for detecting the tilt of a wafer stored in a wafer cassette,
A light projecting unit for projecting detection light, and a photoelectric sensor having a light receiving unit for receiving the detection light projected by the light projecting unit;
A movement control device for moving the photoelectric sensor in a direction perpendicular to the traveling direction of the detection light in a state in which the traveling direction of the detection light is parallel to the plane of the wafer that is normally stored;
An acquisition device that acquires the amount of light received by the light receiving unit during the movement of the photoelectric sensor;
Based on the change in the amount of light during a period in which the photoelectric sensor is detecting a detection target wafer, a specifying device that specifies the direction of tilt of the wafer;
Comprising
Sensor system. The specifying device further specifies an angle of inclination of the wafer based on the change in the light amount;
The sensor system according to claim 1. The sensor system is a transfer device for transferring the wafer, further comprising a transfer device including a chuck for taking out the wafer from the wafer cassette,
The specifying device controls the inclination of the chuck according to the specified inclination and angle of the wafer;
The sensor system according to claim 2. The movement control device is the transport device,
The photoelectric sensor is provided at the tip of the chuck,
The sensor system according to claim 3. A plurality of the photoelectric sensors in an axial direction perpendicular to the detection light and perpendicular to the movement direction of the photoelectric sensors by the movement control device;
The sensor system according to any one of claims 1 to 4. An inclination detection method using a sensor system for detecting an inclination of a wafer stored in a wafer cassette,
The sensor system includes a photoelectric sensor having a light projecting unit that projects detection light, and a light receiving unit that receives the detection light projected by the light projecting unit,
A moving step of moving the photoelectric sensor in a direction perpendicular to the traveling direction of the detection light in a state where the traveling direction of the detection light is parallel to a plane of the wafer that is normally stored;
An acquisition step of acquiring the amount of light received by the light receiving unit during the moving step;
An inclination detection method comprising: a specifying step of specifying a direction of inclination of the wafer based on a change in the amount of light during a period in which the photoelectric sensor detects a detection target wafer.

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