Workpiece handling device and mapping method

Abstract

The subject of the present invention is to reliably detect an abnormal loading state in which multiple workpieces are loaded in one slot or workpieces are loaded across adjacent slots when mapping the in-stock state of workpieces in a storage section, wherein the storage section has multiple slots arranged in a vertical direction and loads one workpiece in each slot under normal conditions. Wafers as workpieces are stored on a cassette stage as a storage section so that a normal loading state and an abnormal loading state appear in multiple locations respectively (step 101), and a sensor is moved in a vertical direction relative to the cassette stage in this state to detect the workpiece (step 102). Based on the average value of the wafer thickness detected for each loading state and the average value of the wafer center position in the height direction detected for each loading state, a judgment threshold for detecting an abnormal loading state is calculated (step 103).

Description

Technical Field

[0001] The present invention relates to the transportation of workpieces using a transportation device such as a transportation robot, and in particular to a transportation device and a mapping method that improves the detection accuracy of abnormal loading status of workpieces in a storage section when performing mapping to determine the in-stock status of workpieces in a storage section such as a cassette or a cassette stage. Background Art

[0002] In the case of using a conveying robot or other conveying device to convey a plate-shaped workpiece such as a semiconductor wafer or a glass substrate, the workpiece of the conveying object is pre-stored in a storage section called a cassette or a cassette stage, and the conveying device extends a hand set at its front end into the storage section of the conveying source to take out the workpiece, conveys the workpiece while placing the workpiece on the hand, and stores the workpiece in the storage section of the conveying destination. Patent document 1 discloses an example of a conveying robot for conveying workpieces such as semiconductor wafers. Generally, since the storage section can accommodate multiple workpieces, it is necessary to investigate the position of the storage section where the workpiece exists in the warehouse before actually conveying, which is called mapping. In the storage section, multiple slots are arranged in a stacked manner in the vertical direction. By executing mapping, it is possible to know which and which slots the workpiece exists, and the best conveying sequence can be assembled according to the result. In the conveying sequence, it is specified that the workpiece is taken out from the slot of the conveying source storage section, and the workpiece is stored in the slot that becomes the current empty slot in the conveying destination.

[0003] Mapping is performed by using a sensor to detect the workpiece in the storage section in a non-contact manner and to find its position. Among the sensors used in mapping, there are a transmission type sensor that detects the workpiece by blocking the optical path with the workpiece, and a reflection type sensor that irradiates the workpiece with light for detection and detects the light reflected by the edge (or end face) of the workpiece, and detects the workpiece based on the amount of reflection and the position of the reflection. In mapping, the presence or absence of the workpiece is determined for each groove while the sensor is moved along the arrangement direction of the grooves. By determining at which position the sensor detects light (transmitted light or reflected light) and at which position the sensor does not detect light, the thickness of the workpiece and the position of the workpiece in the height direction of the groove can also be found. In addition, the workpiece is, for example, a semiconductor wafer, and its thickness is, for example, less than 1 mm, and the interval between the grooves in which each workpiece is placed in the storage section is about 5 mm to 10 mm. For these reasons, when using any of the transmission type and reflection type sensors, the detection light is preferably a laser with a narrow beam diameter and sharp directivity. Examples of mapping using a transmission type sensor are described in Patent Documents 2 and 3.

[0004] In the case where a plate-shaped workpiece is horizontally stored in a storage section where grooves are arranged in a vertical direction, one workpiece needs to be stored in each groove. However, for some reason, two or more workpieces are sometimes placed in one groove in an overlapping manner, or the workpiece is placed in a manner that spans two grooves. In the following description, the state in which one workpiece is stored in one groove is referred to as "single", and the state in which two or more workpieces are stored in one groove is referred to as "double". In each groove, in order to make the workpiece horizontal, the two ends of the workpiece are respectively held by, for example, rails arranged at both ends of the groove in the horizontal direction. Therefore, the groove is a horizontally elongated area, and the height position can be determined in the groove in the height direction of the groove based on the position where the workpiece is held by the rail. In order to transport the workpiece, it is necessary to insert the hand of the transport device into the storage section and slightly raise the hand, thereby placing the workpiece stored in the groove on the hand. Therefore, if the rail parts at both ends of the groove in the horizontal direction are excluded, the grooves adjacent in the vertical direction are not separated. Therefore, the workpiece is sometimes placed obliquely in a manner that spans two grooves adjacent in the vertical direction. The state where a workpiece spans two slots is called "crossover".

[0005] "Single" is a normal storage state or loading state of the workpiece that can enter the storage section. In contrast, "double" and "cross" are abnormal loading states in the storage section. In this way, when the workpiece is stored in the storage section in a "double" or "cross" manner, that is, in an undesirable state, if the workpiece is to be taken out of the storage section, there is a risk of damage to the workpiece or inability to take out the workpiece. Therefore, in mapping, it is necessary not only to determine the in-stock state of the workpiece, but also to identify these undesirable states and issue an alarm, thereby preventing damage accidents, etc. Such an abnormal loading state is different from the case where the detection thickness of the workpiece or the position of the workpiece in the height direction of the groove is "single", so it can be detected by setting a threshold value related to the detection thickness of the workpiece and a threshold value related to the position of the workpiece in the height direction.

[0006] [Prior art literature]

[0007] [Patent Document]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2019-84651

[0009] [Patent Document 2] Japanese Patent Application Publication No. 2004-327501

[0010] [Patent Document 3] Japanese Patent Application Publication No. 2000-36528 Summary of the invention

[0011] When detecting an abnormal loading state of a workpiece during mapping, two thresholds need to be set in advance: a threshold for detecting the thickness of the workpiece and a threshold related to the position of the workpiece in the height direction in the slot. In the past, these thresholds were actually measured for the workpiece in the abnormal loading state and manually set based on the measured data in the normal loading state and the measured data in the abnormal loading state. However, the threshold setting operation takes time and there are deviations depending on who sets the threshold. As a result, sometimes the abnormal loading state cannot be properly detected when mapping is actually performed properly.

[0012] An object of the present invention is to provide a transport device and a mapping method that can accurately set a threshold value for determining an abnormal loading state of a workpiece in a short time when mapping is executed.

[0013] The transport device of the present invention transports workpieces with a storage section as an object, and the storage section has a plurality of grooves arranged in a height direction, and can horizontally store a workpiece as a plate-like object for each groove. The transport device comprises: a hand, which holds the workpiece when transporting the workpiece; a sensor, which irradiates light on the workpiece to determine the storage status of the workpiece in the groove; a moving mechanism, which moves the hand and the sensor relative to the storage section; and a control unit, which drives and controls the moving mechanism, and the control unit performs a threshold detection action of moving the sensor in the height direction and detecting the workpiece by the sensor for a storage section in which workpieces are stored in multiple locations in a normal loading state and in multiple locations in an abnormal loading state, and calculates a threshold value for distinguishing between a normal loading state and an abnormal loading state based on an average value of a detected thickness and an average value of a height position in the groove obtained from the workpiece in the normal loading state in the threshold detection action, and an average value of a detected thickness and an average value of a height position in the groove obtained from the workpiece in the abnormal loading state in the threshold detection action.

[0014] In the transport device of the present invention, a storage section is prepared for storing workpieces in a manner that normal loading states and abnormal loading states appear at multiple locations, and a threshold detection operation similar to the mapping operation is performed on the storage section, and the threshold is calculated based on the average value obtained by the threshold detection operation. Therefore, the threshold for determining whether there is an abnormal loading state when performing mapping can be set automatically without manual work. As a result, there is no deviation in the determination threshold due to differences in operators, and the abnormal loading state can be correctly determined when performing mapping.

[0015] In the transport device of the present invention, it is preferred that the abnormal loading state includes a first state (i.e., "double") in which two or more workpieces are stored in one slot, and a second state (i.e., "cross") in which at least one workpiece is stored across adjacent slots, and when calculating the threshold, a storage unit that stores workpieces at multiple locations in the first state and stores workpieces at multiple locations in the second state is used. By performing a threshold detection operation on a storage unit in which the first state and the second state appear in multiple locations, respectively, a threshold that can distinguish and discriminate the first state and the second state can be obtained.

[0016] In the transport device of the present invention, the sensor is preferably mounted on a hand. In order to perform mapping, the sensor needs to be moved, but by mounting the sensor on a hand that moves relative to the storage unit, the structure of the moving mechanism in the transport device can be simplified.

[0017] In the handling device of the present invention, the sensor may be a transmission type sensor having a light emitting part and a light receiving part, and detecting the workpiece by blocking the light from the light emitting part to the light receiving part by the workpiece, or a reflection type sensor detecting the workpiece by irradiating light to the workpiece and detecting the reflected light from the workpiece. In the present invention, any of the transmission type sensor and the reflection type sensor generally used for mapping may be used. However, depending on the type of sensor used, the calculation procedure of the threshold value may be different.

[0018] When a reflective sensor is used, workpiece detection may not be performed smoothly depending on the mapping position. Here, the mapping position refers to the irradiation position when the sensor is moved in the vertical direction in order to map the storage state of the workpiece in the storage section, and the irradiation position refers to the position in the workpiece that is irradiated by the light from the sensor along the horizontal direction orthogonal to the depth direction of the storage section. Therefore, in the handling device of the present invention, it is preferred that the control unit, before performing the threshold detection action, moves the irradiation position and repeatedly moves the sensor in the vertical direction to detect the reflected light from the workpiece, with the storage section in which one workpiece is stored in each of the slots as the object, thereby obtaining detection distribution data, determining the mapping position based on the detection distribution data, and then performing the threshold detection action at the determined mapping position.

[0019] In the transport device of the present invention, when the control unit controls the moving mechanism to transport the workpiece, it performs mapping control to determine the in-stock status of the workpiece in the storage section, and can use a threshold to determine whether there is an abnormal loading state. By using the threshold determined according to the present invention, the abnormal loading state can be correctly determined when the mapping is executed.

[0020] The mapping method of the present invention is a mapping method for determining the in-stock status of workpieces in a storage section, wherein the storage section has a plurality of grooves arranged in a height direction, and can horizontally store a workpiece as a plate-like object in each groove. In the mapping method, for a storage section in which workpieces are stored in a plurality of locations in a normal loading state and in a plurality of locations in an abnormal loading state, a threshold detection action is performed in which a sensor is moved in a height direction and the sensor detects the workpieces. A threshold for determining the normal loading state and the abnormal loading state is calculated based on an average value of the detected thickness and an average value of the height position in the groove obtained from the workpiece in the normal loading state in the threshold detection action, and an average value of the detected thickness and an average value of the height position in the groove obtained from the workpiece in the abnormal loading state in the threshold detection action.

[0021] In the mapping method of the present invention, a storage section for storing workpieces is prepared in such a manner that a normal loading state and an abnormal loading state appear at a plurality of locations, a threshold detection operation similar to the mapping operation is performed on the storage section, and a threshold is calculated based on an average value obtained by the threshold detection operation. Therefore, the discrimination threshold for discriminating the presence or absence of an abnormal loading state when performing mapping can be automatically set without manual intervention and without deviation, and the abnormal loading state can be correctly discriminated when performing mapping.

[0022] In the mapping method of the present invention, it is preferred that the abnormal loading state includes: a first state (i.e., "double") in which one slot stores more than two workpieces, and a second state (i.e., "cross") in which at least one workpiece is stored across adjacent slots, and when calculating the threshold, a storage unit that stores workpieces at multiple locations in the first state and stores workpieces at multiple locations in the second state is used. By performing a threshold detection operation on a storage unit in which the first state and the second state appear in multiple locations, respectively, a threshold that can distinguish and discriminate the first state and the second state can be obtained.

[0023] In the mapping method of the present invention, as a sensor, a transmission type sensor having a light emitting portion and a light receiving portion, which detects the workpiece by blocking the light from the light emitting portion toward the light receiving portion by the workpiece, or a reflection type sensor which detects the workpiece by irradiating light to the workpiece and detecting the reflected light from the workpiece can be used. However, when a reflection type sensor is used, the detection of the workpiece cannot be performed smoothly depending on the mapping position. Therefore, in the mapping method of the present invention, it is preferred that, when the sensor is a reflection type sensor, before performing the threshold detection action, the irradiation position is moved to repeatedly perform the action of moving the sensor in the vertical direction to detect the reflected light from the workpiece with a storage portion in which a workpiece is stored in each of all the slots as the object, and the detection distribution data is obtained, and the mapping position is determined based on the detection distribution data, and then the threshold detection action is performed at the determined mapping position.

[0024] In the mapping method of the present invention, after the threshold is determined, when the workpiece is transported, the storage portion can be mapped, and the threshold is used to determine whether there is an abnormal loading state. By using the threshold determined according to the present invention, the abnormal loading state can be correctly determined when performing mapping.

[0025] Effects of the Invention

[0026] According to the present invention, it is possible to obtain a transport device and a mapping method that can accurately set a threshold value for determining an abnormal loading state of a workpiece in a short time when executing mapping. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a diagram showing a transfer robot as a transfer device according to one embodiment of the present invention.

[0028] Figure 2 (a) is a plan view illustrating mapping by a transmission type sensor, and (b) and (c) are plan views illustrating mapping by a reflection type sensor.

[0029] Figure 3 It is a front view explaining the mounting state of the chip.

[0030] Figure 4 This is a flowchart showing a procedure for determining a threshold value for distinguishing an abnormal loading state.

[0031] Figure 5 It is a front view for explaining the loading state of the wafer in the storage section for determining the threshold value.

[0032] Figure 6 Determination of the discrimination threshold value TH1 related to the detection thickness will be described.

[0033] Figure 7 This is a diagram for explaining the determination of the determination threshold TH2 related to the detection thickness and the determination threshold TH3 related to the detection position in the height direction.

[0034] Figure 8 This is a diagram for explaining the determination of the discrimination threshold value TH4 related to the detection position in the height direction.

[0035] Fig. 9 1 and 2 are diagrams for explaining determination of a mapping position, wherein (a) is a side view and (b) is a top view.

[0036] Fig.10 It is a diagram showing an example of detection distribution data. DETAILED DESCRIPTION

[0037] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1A transfer robot is shown as a transfer device according to one embodiment of the present invention. Figure 1 The transport robot 20 shown is used to transport a workpiece as a plate-shaped object. Hereinafter, the workpiece is a wafer 50 such as a silicon wafer, and the wafer 50 is stored in a cassette stage 40 as a storage unit. The cassette stage 40 has a plurality of slots arranged in a vertical direction, and is configured to store one wafer 50 horizontally in each slot. Before transporting the wafer 50, the transport robot 20 performs mapping to determine the inventory status of the wafer 50 in the cassette stage 40.

[0038] Figure 1 The transport robot 20 shown is similar to the horizontal articulated robot described in Patent Document 1, for example, and includes three arms 22 to 24 mounted in series on a base 21 and a hand 25 mounted on the front end of the arm 24 on the front end side. Figure 1 The arms 22 to 24 are depicted in a folded state, but the arms 22 to 24 may also be in an unfolded state. In particular, the arms 22 and 23 form a link mechanism in which the front end of the arm 23 moves radially in a horizontal plane with the mounting position of the arm 22 relative to the base 21 as the center. The arm 24 can rotate relative to the arm 23 in a horizontal plane, and the hand 25 can rotate relative to the arm 24. The base 21 is provided with a lifting mechanism (not shown) for raising and lowering the root side of the arm 22 and a rotating mechanism (not shown) for rotating the arm 22 around a vertical axis. If used Figure 2 As described above, a sensor for mapping is mounted on the hand 25. A robot controller 30 for driving and controlling the transport robot 20 is also connected to the transport robot 20. The robot controller 30 controls the lifting mechanism or the rotating mechanism provided on the base 21, the link mechanism composed of the arms 22 and 23, the mechanism for rotating the arm 24 relative to the arm 23, and the mechanism for rotating the hand 25 relative to the arm 24, and processes the detection signal from the sensor. In particular, the robot controller 30 performs control related to the action for determining the discrimination threshold, the action for determining the mapping position, the mapping action, and the action for transporting the workpiece.

[0039] The transport robot 20 performs the following processes: a process of taking out a wafer 50 from the cassette stage 40 of the transport source and transporting the wafer 50 to the device or cassette stage 40 of the transport destination; a process of storing the wafer 50 transported from the device or cassette stage 40 of the transport source into an empty slot of the cassette stage 40 of the transport destination. The cassette stage 40 as a storage unit is a front-opening cassette stage such as a front-opening cassette integrated transport or a FOUP (Front-Opening Unified Pod) as a storage box as specified by the SEMI (Semiconductor Equipment and Materials International) standard E47.1. Therefore, when the transport robot 20 takes out a wafer 50 from a slot in the cassette stage 40, and when storing a wafer 50 in an empty slot in the cassette stage 40, the hand 25 of the transport robot 20 enters the cassette stage 40 through the front opening of the cassette stage 40 with the fork 26 side as the front end, targeting the specified slot.

[0040] Mapping is performed before the actual transfer of the wafer 50 . Since the slots in the cassette stage 40 are arranged in the vertical direction, during mapping, the hand 25 is moved up and down to move the sensor in the vertical direction. Figure 2 (a) to (c) are top views for explaining mapping by sensors. When mapping is performed, the hand 25 moves in a direction perpendicular to the paper surface in the figure. The hand 25 is an elongated member having a fork 26 provided at one end thereof. The fork 20 has a shape that branches into two at the front end, and is a part that holds the wafer 50 as a workpiece when the wafer 50 is transported. During transport, the wafer 50 is placed horizontally on the surface of the fork 26.

[0041] Figure 2 (a) shows a mapping using a transmission type sensor. The transmission type sensor includes a light emitting portion 27 provided at one front end of a fork portion 26 of a hand 25 and a light receiving portion 28 provided at the other front end, and a laser 60 is irradiated from the light emitting portion 27 to the light receiving portion 28. In order to generate the laser 60, for example, a laser diode (LD) is used. As the hand 25 is raised and lowered, the laser 60 is shielded by the wafer 50 and does not enter the light receiving portion 28, thereby enabling the transmission type sensor to detect the workpiece 50 in the groove. The thickness of the wafer 50 and the height position of the wafer 50 in the groove can also be determined based on the movement amount and movement position of the hand 25 during the period when the laser 60 is not incident on the light receiving portion 28.

[0042] Figure 2(b) shows the mapping using the reflection type sensor 29. The reflection type sensor 29 is a sensor in which the light emitting part and the light receiving part of the laser 60 are integrally formed. The laser 60 is irradiated from the light emitting part to the wafer 50, and the reflected light from the wafer 50 is detected by the light receiving part. The laser 50 is diffusely reflected on the end face (wafer edge) of the wafer, so a part of the reflected light is incident on the light receiving part. The thickness of the wafer 50 and the height direction position of the wafer 50 in the groove can also be determined based on the movement amount and movement position of the hand 25 during the period of detecting the reflected light.

[0043] When the reflection type sensor 29 is used, the direction and intensity of the reflected light from the wafer 50 vary greatly depending on the surface condition of the end surface of the wafer 50. When the end surface of the wafer 50 is a rough surface, as described above, Figure 2 As shown in (b), the irradiated laser 60 is diffusely reflected on the end face of the chip 50, and a part of the reflected light generated by the diffuse reflection reaches the light receiving part of the sensor 29. As a result, the sensor 29 can detect the chip 50 independently of the mapping position. Here, the mapping position refers to the position on the chip 50 that is irradiated with light from the sensor 29 along the horizontal direction orthogonal to the depth direction of the cassette stage 40 when the sensor is moved in the vertical direction of the groove arrangement for mapping. In contrast, in the case where the end face of the chip 50 is, for example, a mirror surface, such as Figure 2 As shown in (c), the irradiated laser light 60 is specularly reflected in one direction at the end surface of the wafer 50. In this case, if the mapping position is inappropriate, even if the laser light 60 is irradiated to the wafer 50, the reflected light will not return to the sensor 29, and the sensor 29 may not detect the wafer 50. The determination of the mapping position when using the reflection type sensor 29 will be described later. In addition, the mapping position can be changed by actually moving the sensor 29 in the horizontal direction, or by changing the irradiation direction of the light from the sensor without changing the position of the sensor 29 in the horizontal direction.

[0044] When performing mapping as described above, it is necessary to be able to discriminate an abnormal loading state of the wafer 50 on the cassette stage 40 . Figure 3 is a diagram showing an example of an abnormal loading state, Figure 3 The left half of the figure is depicted as a diagram of a cassette stage 40 storing a workpiece 50 as viewed from the front. The cassette stage 40 shown in the figure has eight slots arranged in the vertical direction, which are numbered as slot 1, slot 2, ... from the bottom. In each slot, a track 41 is provided at both ends of the slot in the horizontal direction. The wafer 50 is stored in the slot by holding both ends of the wafer 50 using a pair of tracks 41 in the slot, so the upper surface of the track 41, that is, the height direction position of the surface of the track 41 that should abut against the wafer 50, is used as the height direction reference in the slot. The height direction reference of each slot is shown by a dotted line in the figure. Figure 3The right half of the diagram shows the following for the case where the sensor is a transmissive type and the case where the sensor is a reflective type: Figure 3 The left half of FIG. 4 shows the range in which the wafer 50 is detected when mapping is performed in the height direction of the groove when the wafer 50 is stored in the cassette stage 40 .

[0045] exist Figure 3 In the embodiment, one wafer 50 is stored in the slot 2, so the wafer 50 is in a normal loading state, that is, "single". Figure 3 In the example, two wafers 50 are stored in the slot 4, and these wafers 50 are in a "double" state, which is one of the abnormal loading states. In the "double" state, which is an abnormal state, the detected thickness of the wafer 50 becomes larger than that in the "single" state, so it is possible to make a judgment based on the detected thickness. For example, whether the sensor is a transmission type or a reflection type, it can be judged as a "double" when the detected thickness exceeds a certain threshold.

[0046] exist Figure 3 , the wafer 50 is arranged to straddle the groove 6 and the groove 7. Specifically, the left end of the wafer 50 in the figure is located on the left end side of the groove 6, and the right end of the wafer 50 in the figure is located on the right end side of the groove 7, and the wafer 50 is stored obliquely. The wafer 50 is in a "cross" state, which is one of the abnormal loading states. When the bad state is "cross", the determination method is different depending on whether the sensor type is a transmission type or a reflection type. When a transmission type sensor is used, if it is "cross", the detection thickness of the wafer 50 becomes larger than that of the "single" case (also compared to the "double" case), and the wafer detection position in the height direction of the groove is also different from that of the "single" case. As the detection position of the wafer in the height direction of the groove, considering the deviation of the thickness of the wafer, etc., it is preferable to use the center position of the wafer in the height direction of the groove. Therefore, when a transmission type sensor is used, when the detection thickness exceeds a certain threshold value, and the difference between the center position of the wafer 50 in the height direction detected and the center position of the wafer 50 in the height direction that should be detected in the "single" case exceeds another threshold value, it can be determined as "cross". In contrast, when using a reflective sensor, since the detection thickness in the "cross" case is the same as that in the "single" case, when the difference between the center position in the height direction of the detected workpiece and the center position in the height direction of the workpiece that should be detected in the "single" case exceeds the threshold, it can be determined as a "cross".

[0047] In the past, two thresholds for detecting abnormal loading states (i.e., a threshold for detecting the thickness of the workpiece and a threshold related to the height direction position of the workpiece in the slot) were manually set. However, the threshold setting operation takes time, and there is a problem that the thresholds may vary depending on who sets them. Therefore, in order to solve such a problem, the transport device of this embodiment automatically finds and sets the threshold for distinguishing abnormal loading states when executing mapping. Figure 4 The following shows the order of determining the threshold values ​​used to distinguish an abnormal loading state. Figure 4 Steps 102 to 103 in the sequence shown are executed by controlling the transfer robot 20 through the robot controller 30 .

[0048] First, in step 101, the wafers 50 are stored on the cassette stage 40 in such a manner that "single" as a normal loading state appears at a plurality of locations, and "double" and "cross" as abnormal loading states appear at a plurality of locations, respectively. Figure 5 An example of the storage state of the wafers 50 in the cassette stage 40 at this time is shown. The wafers 50 are stored in slot 1 and slot 2 in a "single" manner, respectively. Two wafers 50 are stored overlappingly in slot 3, forming a "double". Slot 4 is also a "double". The wafers 50 are arranged in a "cross" manner across the left end of slot 5 and the right end of slot 6. Similarly, the wafers 60 are arranged in a "cross" manner across the left end of slot 6 and the right end of slot 7. Figure 5 In the cases shown, "single" appears in two locations, "double" appears in two locations, and "cross" appears in two locations.

[0049] For the cassette stage 40 storing the wafers 50 in this way, in step 102, the hand 25 is moved in the vertical direction while the sensor detects the wafers 50 in the cassette stage 40, similarly to the mapping performed when the wafers 50 are normally transported. This detection operation is called a threshold detection operation. According to the threshold detection operation, for the wafers 50 in each storage position, the detection value of the detected thickness and the height direction position in each slot can be obtained. Here, the height direction position uses the center position of the height direction of the wafer 50 in the corresponding slot. As a result, the measured values ​​of the thickness of multiple wafers and the center position of the height direction of the wafer are obtained in each "single", "double" and "cross" loading state. In the case of "cross", as described above, the measured value is different depending on whether the sensor is a transmission type sensor or a reflection type sensor. Here, since it is known which wafer 50 or which slot is in which loading state in the cassette stage 40, the threshold (i.e., the judgment threshold) for distinguishing an abnormal loading state is determined based on the measured value when performing mapping so that it is consistent with the known loading state. That is, in step 103, the discrimination threshold is calculated based on the average value of the wafer thickness measurement value for each mounted state and the average value of the measurement value at the center position in the height direction. The calculation of the discrimination threshold is described in detail below.

[0050] In the threshold detection operation, the average value of the thickness of the "single" wafer 50 detected by the sensor is set to a, and the average value of the height direction center position of the wafer 50 in each groove is set to b. Similarly, the average value of the thickness of the "double" wafer 50 detected by the sensor is set to c. For the "cross" wafer 50, the average value of the thickness when detected by the transmission sensor is set to d, the average value of the height direction center position of the groove when detected by the transmission sensor is set to e, and the average value of the height direction center position of the groove when detected by the reflection sensor is set to f.

[0051] like Figure 6 As shown, the discrimination threshold TH1 for discriminating the "double" in the abnormal loading state is the middle value between the average value a of the detected thickness in the case of "single" and the average value c of the detected thickness in the case of "double".

[0052] Let TH1 = (a + c) / 2.

[0053] The thresholds for determining "cross" using a transmission sensor include a threshold TH2 based on the detected thickness and a threshold TH3 based on the center position in the height direction. Figure 7 As shown, the threshold value TH2 based on the detected thickness is set to the middle value of the average value a of the detected thickness in the case of "single" and the average value d of the detected thickness in the case of "cross".

[0054] Let TH2 = (a + d) / 2.

[0055] The determination threshold value TH3 based on the center position in the height direction is set to the middle value of the average value b of the center position in the height direction in the case of "single" and the average value e of the center position in the height direction in the case of "cross".

[0056] Let TH3 = (b + e) ​​ / 2.

[0057] like Figure 8 As shown, the threshold value TH4 for determining "cross" using the reflective sensor is set to the middle value of the average value b of the center position in the height direction when "single" and the average value f of the center position in the height direction when "cross".

[0058] Let TH4 = (a + f) / 2.

[0059] In the present embodiment, as described above, a discrimination threshold for determining whether an abnormal loading state is present when mapping is performed is determined. The discrimination threshold is stored as a parameter, for example, in the robot controller 30. Once the discrimination threshold is determined, when mapping is performed when the wafer 50 is actually transported, by comparing the detected thickness of the wafer and the center position in the height direction of the groove with the discrimination threshold, it is possible to determine whether the wafer 50 is carried on the cassette stage 40 in an abnormal state. In the case of using a transmission type sensor, when the detected thickness of the wafer is greater than any one of the discrimination thresholds TH1 and TH2, or when the center position in the height direction of the wafer is greater than TH3, it can be determined that an abnormal loading state has occurred. When it is necessary to distinguish between "double" and "cross", since TH2>TH1 is generally the case, when the detected thickness exceeds TH2, or the center position in the height direction of the groove exceeds TH3, it can be determined as "cross", and otherwise it can be determined as "double". When using a reflective sensor, if the detected thickness of the wafer is greater than the discrimination threshold TH1, it can be discriminated as "double", and if the center position in the height direction is greater than the discrimination threshold TH4, it can be discriminated as "cross".

[0060] However, in the case of using the reflective sensor 29, Figure 2 As shown in (c), the wafer 50 may not be detected depending on the irradiation position of the laser 60 on the wafer 50. Therefore, when the wafer 50 may not be detected due to its shape or material, it is preferable to perform an action of determining an appropriate mapping position before performing the actions of steps 101 to 103. The determination of the mapping position is also performed by the robot controller 30 controlling the transport robot 0. The determined mapping position is not only used for mapping during transport, but also used when performing the threshold detection action in step 102.

[0061] Since the mapping position needs to be determined according to the shape and material of the wafer 50, in determining the mapping position, first, the wafers 50 of the same shape and material as the wafer to be transported are stored one by one in all the slots of the cassette stage 40 as the mapping object. Then, the reflective sensor 29 mounted on the hand 25 is directed toward the cassette stage 40, and the hand 25 is moved to a position in front of the cassette stage 40. Next, similarly to the mapping operation and the threshold detection operation, Fig. 9 As shown in (a), the hand 25 is moved in the vertical direction to irradiate the laser 60 to the cassette stage 40 to detect the wafer 50. Fig. 9 As shown in (b), while changing the horizontal position of the hand 25 (i.e., the reflective sensor 29) in front of the cassette stage 40, such detection of the wafer 50 is repeatedly performed. The horizontal direction here is a horizontal direction perpendicular to the depth direction of the cassette stage 40. As a result, the wafers 50 in each slot are irradiated with the laser 60 at different positions along the horizontal direction, and the light receiving part of the sensor 29 is used to obtain the detection result of the wafer thickness at each slot and each irradiation position in the horizontal direction. Fig. 9 In the example shown, the laser beam 60 is irradiated at 11 different positions A to K along the horizontal direction.

[0062] A series of detection results obtained in this manner can be shown as two-dimensional detection distribution data, in which the irradiation position in the horizontal direction is one dimension and the slot position in the vertical direction is the other dimension. Fig.10 The figure shows an example of detection distribution data obtained when the number of slots in the cassette stage 40 is 10, the irradiation positions of the laser 60 in the horizontal direction are the above-mentioned 11 positions A to K, and a silicon wafer with a thickness of 0.9 mm is stored in each slot as the wafer 50. The area shown in black in the figure is the area where the sensor 29 detects the wafer 50. The larger the size of the area in the vertical direction (the vertical direction in the figure), the thicker the detected wafer 50 is. The dotted line shows that the wafer 50 is not detected although it exists.

[0063] exist Fig.10In the results shown, although the wafer 50 of the same material and the same thickness is to be detected, the detected thickness in each groove and each irradiation position is very different. There are also grooves where the detection of the wafer 50 fails at positions A, B, and K. In addition, at positions F, G, and H, a wafer 50 that is about 2 to 4 times thicker than the original thickness is detected, and the deviation in the detected thickness is large. This is believed to be due to the over-reflection caused by the reflection angle of the laser 60 in the wafer 50. Therefore, in the process of determining the mapping position, in addition to the irradiation position where the groove of the wafer 50 cannot be detected and the irradiation position where excessive over-reflection occurs, a position suitable for mapping is found from the irradiation positions, and the irradiation position is determined as the mapping position. As conditions for determining the mapping position, the following (1) to (3) can be cited.

[0064] (1) The average value of the detected thickness is closest to the specified thickness (e.g., the thickness of the wafer 50);

[0065] (2) The deviation is the smallest among all the values ​​of the tested thickness;

[0066] (3) The difference between the maximum and minimum values ​​of the detected thickness is the smallest.

[0067] When determining the mapping position, any one of the conditions (1) to (3), two of the conditions, or all of the conditions (1) to (3) may be used. By determining the mapping position in this way, even when the reflection sensor 29 is used, the wafer 50 can be reliably detected in the threshold detection operation and the mapping operation. Fig.10 In the example shown, for example, position D or position I is determined as the mapping position.

[0068] In the transfer robot 20 of the present embodiment described above, the cassette stage 40 storing the wafers 50 is prepared so that the normal loading state and the abnormal loading state appear at a plurality of locations, respectively, and the discrimination threshold is calculated based on the average value obtained by performing the threshold detection operation on the cassette stage 40, so that the discrimination threshold for discriminating the presence or absence of the abnormal loading state when performing mapping can be set automatically without manual work. As a result, the deviation of the discrimination threshold due to the difference in operators does not occur, and the abnormal loading state can be correctly discriminated when performing mapping. Furthermore, since the detection distribution data is obtained by using the cassette stage 40 storing the wafers 50 in all the slots, and the mapping position is determined based on the detection distribution data, the optimal mapping position can be automatically obtained without manual work, and a more appropriate discrimination threshold can be obtained by performing the threshold detection operation at the mapping position. According to the present embodiment, the setting stage of the discrimination threshold for discriminating the abnormal loading states of "double" and "cross" when performing mapping can be reduced.

[0069] Here, the reset of the discrimination threshold is explained. When a reflective sensor is used, the threshold may change according to the shape or material of the workpiece, the surface state, etc. Therefore, when the batch of workpieces is switched, the discrimination threshold needs to be reset. When the batch of workpieces is switched, generally, a device such as a semiconductor manufacturing device provided with a transport device is stopped, and the discrimination threshold can be reset during the stop period. Similarly, when a transmission sensor is used, if the level of a storage part such as a cassette stage changes due to a production change, the detected thickness of the wafer changes, and therefore, the discrimination threshold needs to be reset at such a time. When the production change is adjusted, generally, a device such as a semiconductor manufacturing device provided with a transport device is stopped, and the discrimination threshold can be reset during the stop period. Therefore, even if the discrimination threshold is automatically set according to the present invention, the stop period of the device will not be extended, which helps to improve the productivity of the device.

[0070] In the case where the discrimination threshold is calculated based on the present invention, the wafer 50 needs to be stored in the cassette stage 40 as intended in the above step 101. In order to prevent errors in the storage of the wafer 50 at this time, for example, the deviation or standard deviation of the detection value when the wafer 50 in each loading state is detected can be calculated, and an alarm can be issued to urge confirmation when the deviation is large. Alternatively, after calculating each discrimination threshold, the calculated discrimination threshold can be used to determine the detection results remaining in the memory of the robot controller 30 to determine whether the normal loading state and the abnormal loading state can be correctly distinguished, and an alarm can be issued to urge confirmation when the discrimination cannot be correctly distinguished.

[0071] Reference numerals

[0072] 20…Transportation robots;

[0073] 21…Abutment;

[0074] 22-24…arm;

[0075] 25…hands;

[0076] 26…fork;

[0077] 27…luminous part;

[0078] 28…light receiving part;

[0079] 29…Sensor;

[0080] 30…Robot controller;

[0081] 40…cassette stage;

[0082] 41…track;

[0083] 50… wafers;

[0084] 60…Laser.

Claims

1. A conveying device for conveying a workpiece with a storage section as a target, the storage section having a plurality of grooves arranged in a height direction, capable of horizontally storing one of the workpieces as a plate-like object in each of the grooves, the conveying device comprising: a hand for holding the workpiece while carrying the workpiece; A sensor that irradiates light to the workpiece to determine the storage status of the workpiece in the slot; a moving mechanism that moves the hand and the sensor relative to the storage portion; as well as a control unit, which drives and controls the moving mechanism, The control unit performs a threshold detection action of moving the sensor in the height direction and detecting the workpiece by the sensor for the storage section in which the workpiece is stored in multiple positions in a normal loading state and in multiple positions in an abnormal loading state, and calculates an intermediate value between an average value of the detected thickness obtained from the workpiece in the normal loading state in the threshold detection action and an average value of the detected thickness obtained from the workpiece in the abnormal loading state in the threshold detection action, or an intermediate value between an average value of the height position in the groove in the normal loading state in the threshold detection action and an average value of the height position in the groove in the abnormal loading state in the threshold detection action, as a threshold value for distinguishing the normal loading state from the abnormal loading state.

2. The transport device according to claim 1, characterized in that: The abnormal loading state includes a first state in which two or more workpieces are stored in one slot, and a second state in which at least one workpiece is stored across adjacent slots. When calculating the threshold value, the storage section in which the workpieces are stored at a plurality of locations in the first state and the workpieces are stored at a plurality of locations in the second state is used.

3. The transport device according to claim 1, characterized in that: The sensor is mounted on the hand.

4. The transport device according to claim 2, characterized in that: The sensor is mounted on the hand.

5. The transport device according to any one of claims 1 to 4, characterized in that: The sensor is a transmission type sensor including a light emitting section and a light receiving section, and detects the workpiece when light from the light emitting section toward the light receiving section is blocked by the workpiece.

6. The transport device according to any one of claims 1 to 4, characterized in that: The sensor is a reflection type sensor that detects the workpiece by irradiating light to the workpiece and detecting reflected light from the workpiece.

7. The transport device according to claim 6, characterized in that: a position on the workpiece irradiated with light from the sensor along a horizontal direction perpendicular to the depth direction of the storage portion as an irradiation position, Before performing the threshold detection operation, the control unit moves the irradiation position and repeatedly moves the sensor in a vertical direction to detect the reflected light from the workpiece, taking the storage section in which all the slots store one workpiece each as the target, obtains detection distribution data, and determines a mapping position based on the detection distribution data. The control unit performs the threshold detection operation at the determined mapping position, The mapping position is the irradiation position when the sensor is moved in the vertical direction in order to perform mapping for determining the storage state of the workpiece in the storage section.

8. The transport device according to any one of claims 1 to 4, characterized in that: The control unit controls the moving mechanism to transfer the workpiece, performs control of mapping to determine the storage status of the workpiece in the storage section, and determines the presence or absence of the abnormal loading status using the threshold value.

9. A mapping method for determining the storage status of workpieces in a storage section, wherein the storage section has a plurality of slots arranged in a height direction, and each of the slots can horizontally store one of the workpieces as a plate-like object, characterized in that: For the storage section in which the workpieces are stored at a plurality of locations in a normal loading state and in which the workpieces are stored at a plurality of locations in an abnormal loading state, a threshold detection operation is performed in which the sensor moves in the height direction and detects the workpieces by the sensor, The intermediate value of the average value of the detected thickness obtained from the workpiece in the normal loading state in the threshold detection action and the average value of the detected thickness obtained from the workpiece in the abnormal loading state in the threshold detection action, or the intermediate value of the average value of the height position in the groove in the normal loading state in the threshold detection action and the average value of the height position in the groove in the abnormal loading state in the threshold detection action is calculated as a threshold for distinguishing the normal loading state and the abnormal loading state.

10. The mapping method according to claim 9, characterized in that: The abnormal loading state includes a first state in which two or more workpieces are stored in one slot, and a second state in which at least one workpiece is stored across adjacent slots. When calculating the threshold value, the storage section in which the workpieces are stored at a plurality of locations in the first state and the workpieces are stored at a plurality of locations in the second state is used.

11. The mapping method according to claim 9 or 10, characterized in that: The sensor is a reflection type sensor that detects the workpiece by irradiating light to the workpiece and detecting reflected light from the workpiece. a position on the workpiece irradiated with light from the sensor along a horizontal direction perpendicular to the depth direction of the storage portion as an irradiation position, Before performing the threshold detection operation, the storage section in which all the grooves store one workpiece each is used as the object, the irradiation position is moved and the sensor is repeatedly moved in the vertical direction to detect the reflected light from the workpiece, detection distribution data is obtained, and a mapping position is determined based on the detection distribution data. performing the threshold detection operation at the determined mapping position, The mapping position is the irradiation position when the sensor is moved in the vertical direction in order to perform the mapping.

12. The mapping method according to claim 9 or 10, characterized in that: When the workpiece is conveyed after the threshold value is determined, the mapping for the storage section is performed, and the presence or absence of the abnormal loading state is determined using the threshold value.

13. The mapping method according to claim 11, characterized in that: When the workpiece is conveyed after the threshold value is determined, the mapping for the storage section is performed, and the presence or absence of the abnormal loading state is determined using the threshold value.

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