JP7699457B2 - Workpiece transport device and mapping method - Google Patents

Description

The present invention relates to the transportation of workpieces using a transport device such as a transport robot, and in particular to a transport device and mapping method that improves the accuracy of mapping to determine the status of workpieces in a storage unit such as a cassette or cassette stage.

When a conveying device such as a conveying robot conveys a plate-shaped workpiece such as a semiconductor wafer or a glass substrate, the workpiece to be conveyed is accommodated in a container called a cassette or cassette stage, and the conveying device extends a hand provided at the tip of the conveying device into the container at the source to pick up the workpiece, conveys the workpiece while it is placed on the hand, and accommodates the workpiece in the container at the destination. An example of a conveying robot that conveys workpieces such as semiconductor wafers is shown in Patent Document 1. Since a container can generally accommodate multiple workpieces, it is necessary to check the position of the workpiece in the container before actually conveying it, and this is called mapping. Assuming that the container has multiple slots stacked vertically, by performing mapping, it is possible to know which slots the workpieces are in, and the optimal conveying sequence can be assembled according to the results. In the conveying sequence, it is specified which slot in the container at the source to pick up the workpiece from and which slot in the container at the destination to accommodate the workpiece.

Mapping is performed by detecting the workpiece in the storage section without contact using a sensor and determining its position. The sensors used for mapping include a transmission type sensor that detects the workpiece by blocking the light path with the workpiece, and a reflection type sensor that irradiates the workpiece with detection light, 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 reflection position. The workpiece is, for example, a semiconductor wafer, and its thickness is, for example, 1 mm or less. In addition, the interval between the slots in the storage section in which the workpieces are placed one by one is about 5 mm to 10 mm. For these reasons, whether a transmission type or reflection type sensor is used, it is preferable that the detection light is a laser light with a narrow beam diameter and sharp directionality. When a transmission type sensor is used, there is an advantage that stable detection results can be obtained regardless of the material of the workpiece, but the sensor needs to be close to the storage section or the workpiece, and there is a risk of interference or contact with the storage section or the workpiece. In addition, if the sensor is attached to the hand, the hardware structure such as the hand needs to be shaped to be able to detect the workpiece through the hand. Examples of mapping using a transmission type sensor are described in Patent Documents 2 and 3.

When a reflective sensor is used, the workpiece inventory status can be known from a position away from the workpiece, so interference between the sensor and the workpiece can be prevented, and there are no restrictions on the hardware structure. For example, if the transport device is a transport robot, if the sensor can be placed on the arm or hand of the robot, there is no need to give the area around the sensor a special shape for mapping, so mapping using a reflective sensor has great advantages in terms of introduction and operation. However, in mapping using a reflective sensor, the detection accuracy may deteriorate depending on the material, dimensions, and surface condition of the workpiece. If the absorption of light by the workpiece can be ignored and the workpiece surface is rough, the light will be diffusely reflected, so the workpiece can be detected reliably. In contrast, for example, if the workpiece is a silicon wafer and its surface is mirror-finished, the detection light may be totally reflected depending on the mapping position, that is, where the detection light from the sensor is irradiated, and in such a case, the workpiece cannot be detected properly. More specifically, the mapping position is the position on the workpiece where the light from the sensor is irradiated along a direction (second direction) perpendicular to the first direction on the front surface of the storage unit when mapping is performed by moving the sensor in the direction in which the slots are arranged (first direction). The mapping position can be changed by actually moving the sensor in the second direction, or by changing the direction of light emitted from the sensor without changing the position of the sensor in the second direction. When mapping is performed using a reflective sensor, it is necessary to manually adjust the mapping position while referring to the detection results when the work position is known, in order to ensure stable detection.

When storing workpieces in the cassette stage, it is necessary to store one workpiece per slot. However, for some reason, two or more workpieces may be placed overlapping in one slot, or a workpiece may be placed so as to straddle two slots. If an attempt is made to remove a workpiece from the cassette stage when the workpiece is stored in the cassette stage in an incorrect form, i.e., in a defective state, the workpiece may be damaged. Therefore, it is desirable for mapping to recognize such defective states and issue an alert, thereby preventing damage accidents. Such defective states can be identified by the thickness of the workpiece detected when mapping is performed and the position of the workpiece in the slot. If there is an error in determining the loading status by mapping, problems such as the robot going to retrieve a workpiece from a slot that does not contain a workpiece and stopping with an error, or placing a workpiece overlapping a slot where a workpiece is already present, causing damage to the workpiece, occur. Since the transport of the workpieces is performed continuously, mapping is required to be performed accurately over a long period of time.

JP 2019-84651 A JP 2004-327501 A JP 2000-36528 A

Mapping using a reflective sensor has the advantage that mapping can be done without approaching the workpieces or the storage area, but depending on the material and surface condition of the workpieces, it may not be possible to accurately determine the workpiece inventory status.

The object of the present invention is to provide a conveying device that conveys workpieces and is capable of accurately determining the workpiece inventory status while using a reflective sensor, and a mapping method that can perform such accurate mapping.

When transporting workpieces to a storage section that has multiple slots arranged in a first direction and can accommodate one workpiece per slot, mapping is performed before the workpieces are actually transported to determine the presence or absence of the workpieces in the storage section. In mapping, a sensor is moved along the first direction to determine whether a workpiece is present in each slot. When a reflective sensor is used to prevent the sensor from interfering with the workpiece or storage section during mapping, the detection of the workpiece may become unstable depending on the mapping position depending on the shape or material of the workpiece, so it is necessary to determine the optimal mapping position in advance. The present invention aims to automate the determination of the mapping position as a pre-processing before transporting the workpiece. Once the mapping position is determined, the same mapping position can be used as long as the shape or material of the workpiece does not change.

Therefore, the conveying device of the present invention is a conveying device that conveys workpieces to a storage section that has a plurality of slots arranged in a first direction and can accommodate one workpiece per slot, and includes a hand that holds the workpiece when conveying the workpiece, a reflective sensor that irradiates light on the workpiece and detects reflected light, a moving mechanism that moves the hand and the sensor relative to the storage section, and a control means that drives and controls the moving mechanism. The control means moves the sensor toward the position of the storage section where a workpiece is accommodated in each of the slots, and then moves the sensor along the first direction to detect reflected light from the workpiece, and repeats this operation by moving the light irradiation position from the sensor along a second direction perpendicular to the first direction on the front surface of the storage section to obtain detection distribution data, and determines a mapping position based on the detection distribution data. The mapping position is the position along the second direction of the irradiation position on the workpiece when the sensor is moved along the first direction to perform mapping to determine the presence status of the workpieces in the storage section.

Repeatedly performing the operation of moving the sensor along a first direction to detect reflected light from the workpieces in the storage section with one workpiece accommodated in each slot, and then moving the sensor along a second direction perpendicular to the first direction on the front side of the storage section, can be said to be repeating mapping at different mapping positions for the storage section. In this case, the sensor obtains data indicating the detection intensity of the workpiece for each mapping position and for each slot. These data can be expressed as detection distribution data with the mapping position and the slot position as coordinates, respectively. Since it is known that one workpiece is accommodated in each slot, it is possible to extract from the detection distribution data the mapping position at which the workpiece is detected with appropriate detection intensity for each slot based on this fact. In the transport device of the present invention, by determining the mapping position from the detection distribution data in this way, it becomes possible to accurately determine the presence status of the workpieces in mapping when the workpieces are actually transported during actual operation.

In the conveying device of the present invention, it is preferable that the control means, before acquiring the detection distribution data, moves the sensor along the first direction in front of the storage unit to determine the movement range of the sensor along the first direction when acquiring the detection distribution data and when performing mapping. By determining the movement range of the sensor along the first direction in advance in this manner, the amount of movement of the sensor along the first direction can be minimized, improving work efficiency. Furthermore, by determining the movement range along the first direction in advance, it becomes possible to easily determine in which slot the workpiece is present, based on the position of the sensor within that movement range.

In the transport device of the present invention, the sensor is preferably attached to the hand. The sensor needs to be moved for mapping, but by attaching the sensor to the hand that moves relative to the storage unit, the configuration of the movement mechanism in the transport device can be simplified.

In the conveying device of the present invention, for example, the workpiece is a plate-like object that is placed horizontally in the slot, and the first direction is the vertical direction. Detection using a reflective sensor tends to be unstable when the workpiece is a plate-like object, but the conveying method of the present invention makes it possible to perform mapping that can reliably determine the presence or absence of the workpiece even in such cases.

In the transport device of the present invention, the control means can execute control to perform mapping for the storage section using the determined mapping position when controlling the moving mechanism to transport the workpiece. In such a transport device, mapping is performed at the determined mapping position when actually transporting the workpiece after determining the mapping position as described above, so that the inventory status of the workpiece in the storage section can be accurately determined. In this case, the control means may determine the first mapping position and the second mapping position from the detection distribution data, and when performing mapping, move the sensor at the first mapping position along the forward direction of the first direction, and then move the sensor at the second mapping position along the reverse direction of the first direction. Since mapping is performed at different mapping positions while moving the sensor back and forth along the first direction, the accuracy of mapping can be improved while minimizing the increase in the amount of movement of the sensor.

The mapping method of the present invention is a mapping method for determining the presence of workpieces in a storage section that has a plurality of slots arranged in a first direction and can store one workpiece per slot, and includes a moving step of moving a reflective sensor toward a position of the storage section where one workpiece is stored in each of the slots, an acquisition step of moving the sensor along the first direction after the moving step to detect reflected light from the workpieces by repeatedly moving the irradiation position of the light from the sensor along a second direction perpendicular to the first direction on the front surface of the storage section to acquire detection distribution data, and a determination step of determining a mapping position based on the detection distribution data. The mapping position is the position along the second direction of the irradiation position when the sensor is moved along the first direction to perform mapping.

In the mapping method of the present invention, to find the optimal mapping position, mapping is repeated while changing the mapping position for the storage section when one workpiece is stored in each slot, and detection distribution data is obtained based on the data from the sensor at that time. Since it is known that one workpiece is stored in each slot, it is possible to extract from the detection distribution data the mapping position at which the workpiece is detected with appropriate detection strength for each slot. In this way, by determining the mapping position from the detection distribution data, the mapping method of the present invention makes it possible to accurately determine the workpiece loading status during mapping when the workpieces are actually transported during actual operation.

In the mapping method of the present invention, it is preferable to move the sensor along the first direction in front of the storage unit after the moving step and before the determining step to determine the movement range of the sensor along the first direction during the acquisition step and when performing mapping. By determining the movement range of the sensor along the first direction in advance in this manner, the amount of movement of the sensor along the first direction can be minimized, improving work efficiency. Furthermore, by determining the movement range along the first direction in advance, it becomes possible to easily determine in which slot the workpiece is present, based on the position of the sensor within that movement range.

In the mapping method of the present invention, for example, the workpiece is a plate-like object that is placed horizontally in the slot, and the first direction is the vertical direction. Detection using a reflective sensor tends to be unstable when the workpiece is a plate-like object, but the mapping method of the present invention makes it possible to perform mapping that can reliably determine the workpiece inventory status even in such cases.

In the mapping method of the present invention, when the workpiece is transported after the determination step, the mapping position can be used to perform mapping for the storage section. In this method, when the workpiece is actually transported after the mapping position is determined, mapping is performed at the determined mapping position, so that the inventory status of the workpiece in the storage section can be accurately determined. In this case, the first mapping position and the second mapping position are determined in the determination step, and when mapping is performed, the sensor may be moved at the first mapping position along the forward direction of the first direction, and then moved at the second mapping position along the reverse direction of the first direction. Since mapping is performed at different mapping positions while the sensor is moved back and forth along the first direction, the accuracy of mapping can be improved while minimizing the increase in the amount of sensor movement.

According to the present invention, it is possible to obtain a conveying device for conveying workpieces, which is capable of accurately determining the workpiece inventory status while using a reflective sensor, and a mapping method that can perform such accurate mapping.

1 is a diagram showing a transport robot which is a transport device according to an embodiment of the present invention; 5A and 5B are plan views showing the relationship between the hand, the sensor, and the workpiece. 13 is a flowchart showing a procedure for determining a mapping position. FIG. 11 is a side view illustrating the lowest mapping point LL and the highest mapping point UL. 5A and 5B are diagrams for explaining a method for acquiring detection distribution data, in which FIG. 5A is a side view and FIG. FIG. 11 is a diagram illustrating an example of detection distribution data. FIG. 13 is a front view showing an example of a mapping path.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a transport robot, which is a transport device according to an embodiment of the present invention. The transport robot 20 shown in FIG. 1 is used to transport a workpiece, which is a plate-like object. In the following description, the workpiece is a wafer 50 such as a silicon wafer, and the wafer 50 is stored in a cassette stage 40, which is a storage section. The cassette stage 40 has a plurality of slots arranged in a first direction, specifically, in the vertical direction. In this cassette stage 40, one wafer 50 is stored horizontally in each slot. Before transporting the wafer 50, the transport robot 20 performs mapping to determine the presence or absence of the wafer 50 in the cassette stage 40.

The transport robot 20 shown in FIG. 1 is similar to the horizontal articulated robot described in Patent Document 1, for example, and includes three arms 22-24 attached in series to a base 21 and a hand 25 attached to the tip of the tip-side arm 24. Although FIG. 1 illustrates the arms 22-24 in a folded state, the arms 22-24 can also be in an unfolded state, and in particular, the arms 22 and 23 form a link mechanism in which the tip of the arm 23 moves in a radial direction within a horizontal plane, centered on the attachment position of the arm 22 to the base 21. The arm 24 can rotate within a horizontal plane relative to the arm 23, and the hand 25 can rotate relative to the arm 24. The base 21 is provided with a lifting mechanism (not shown) for lifting and lowering the base-side arm 22, and a rotation mechanism (not shown) for rotating the arm 22 around a vertical axis. A reflective sensor 29 for mapping is attached to the hand 25. The transport robot 20 is further connected to a robot controller 30 for driving and controlling the transport robot 20. The robot controller 30 controls the lifting mechanism and rotation mechanism provided on the base 21, the link mechanism consisting 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 detection signals from a sensor 29 described below. In particular, the robot controller 30 executes control over the operation for determining the mapping position, the mapping operation, and the operation for transporting the workpiece, which will be described later.

2(a) and (b) show the relationship between the hand 25, the sensor 29, and the wafer 50 during mapping. The hand 25 is a long and slender member with a fork 26 at one end, and a reflective sensor 29 attached to the other end of the hand 25. The fork 20 has a shape with two branches at the tip, and is a part that holds a workpiece such as a wafer 50 when the workpiece is transported. The workpiece, which is a plate-like object, is placed horizontally on the surface of the fork 26 during transport. The sensor 29 is an integrated unit that generates and emits laser light 60 using a laser diode (LD) or the like, and a light receiving unit that detects the reflected light when the laser light 60 is reflected by a workpiece such as a wafer 50.

When the workpiece is a wafer 50, the mapping of the wafer 50 is performed by moving the sensor 29 in the thickness direction of the wafer 50, irradiating a laser beam 60 from the sensor 29 toward the edge of the wafer 50 (wafer edge), and detecting the reflected light from the edge of the wafer 50. The thickness of the wafer 50 can also be detected from the amount of movement of the sensor 29 during the period in which the reflected light is detected. However, the direction and intensity of the reflected light vary greatly depending on the surface condition of the edge of the wafer 50. When the edge of the wafer 50 is rough, the irradiated laser beam 60 is diffusely reflected at the edge of the wafer 50 as shown in FIG. 2(a), and part of the reflected light due to the diffuse reflection reaches the light receiving portion of the sensor 29. As a result, the sensor 29 can detect the wafer 50 regardless of the mapping position. On the other hand, when the edge of the wafer 50 is, for example, a mirror surface, the irradiated laser beam 60 is mirror-reflected in one direction at the edge of the wafer 50 as shown in FIG. 2(b). In this case, even if the laser light 60 is irradiated onto the wafer 50 with an inappropriate mapping position, the reflected light may not return to the sensor 29, and the sensor 29 may not be able to detect the wafer 50. In the transport robot 20 of this embodiment, the transport device itself automatically seeks to find an appropriate mapping position based on the material and shape of the wafer 50 before mapping is performed for transporting the wafer 50.

The transport robot 20 performs the process of taking out one wafer 50 from the cassette stage 40 at the transport source and transporting the wafer 50 to the device or cassette stage 40 at the transport destination, and the process of storing the wafer 50 transported from the device or cassette stage 40 at the transport source in an empty slot of the cassette stage 40 at the transport destination. The cassette stage 40, which is the storage section, is a front-opening type such as a front-opening cassette integrated transport and storage box FOUP (Front-Opening Unified Pod) as specified in 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 the transport robot 20 stores 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 with the fork part 26 side at the tip, aiming for a specified slot through the front opening of the cassette stage 40.

The determination of the mapping position in this embodiment will be described. FIG. 3 shows the procedure for determining the mapping position. Steps 102 to 106 of the procedure shown in FIG. 3 are executed by the robot controller 30 controlling the transport robot 20. Since the mapping position needs to be determined for each shape and material of the wafer 50, first, in step 101, wafers 50 having the same shape and material as the wafer to be transported are placed one by one in all slots of the cassette stage 40 to be mapped. Next, in step 102, teaching of the cassette stage position for use in normal wafer transport is performed. In this case, teaching is performed to move the hand 25 to a standby position in front of the target cassette stage 40, where the hand 25 is waiting to access the cassette stage 40.

Next, in step 103, the hand 25 is rotated relative to the arm 24 so that the reflective sensor 29 attached to the hand 25 faces the stage cassette 40, and the hand 25 is taught to a position where the laser light 60 from the sensor 29 irradiates approximately the center of the wafer 50 when the cassette stage 40 is viewed from the front opening side, and the lower end position of the bottom slot of the cassette stage 40 is set as the mapping lowest point LL. This teaching is teaching for mapping, and the teaching position is registered in the robot controller 30 as one for mapping. Next, the hand 25 is moved vertically upward, and teaching is performed in the same way, with the upper end position of the top slot of the cassette stage 40 as the mapping highest point UL. Figure 4 is a diagram explaining the teaching here. The section between the mapping lowest point LL and the mapping highest point UL, and the small margin sections set on both ends of this section, are determined as the mapping range, which is the vertical movement range of the sensor 29 when determining the mapping position in step 104 and when actually performing mapping after the mapping position has been determined, i.e., the movement range of the hand 25.

From the teaching height TL when teaching the hand 25 to the standby position in step 102 and the mapping lowest point LL, an offset between the actual slot height as seen from the transport robot 20, in other words, the height expressed in the coordinate system of the transport robot 20, and the height detected by irradiation with the laser light 60 is obtained. If this offset is called a mapping offset, the mapping offset is given by:
Mapping offset = LL - TL
The mapping offset can be used to determine in which slot from the bottom of the cassette stage 40 the wafer 50 is located when the wafer 50 is detected. Here, the vertical direction is defined as the Z direction, the direction from the hand 25 in the standby position toward the cassette stage 40 as the Y direction, and the direction perpendicular to the Z direction in front of the cassette stage 40 as the X direction. The X and Y directions are on a horizontal plane and perpendicular to each other.

By executing steps 101 to 104, the preliminary steps for determining the optimal mapping position are completed. After that, in step 105, detection distribution data used to determine the mapping position is acquired. Figures 5(a) and (b) are diagrams explaining the acquisition of detection distribution data. In acquiring detection distribution data, as shown in Figure 5(a), the sensor 29 is moved in the vertical direction, i.e., the Z direction, within the mapping range while emitting laser light 60 to the cassette stage 40 in which wafers 50 are accommodated in all slots, in the same manner as in the mapping performed when the wafers 40 are transported, and an attempt is made to detect each wafer 50 in the cassette stage 40. This is called a detection operation. This detection operation is then repeatedly performed while moving the sensor 29 in the X direction. Figure 5(b) shows at which position in the X direction the detection operation is performed by the laser light 60 from the sensor 29. Specifically, a range of, for example, ±10 mm is set in both the positive and negative directions of the X direction, centered on the position in the X direction when the mapping lowest point LL was found, and the detection operation is performed while moving the sensor 29 along the X direction within this range at a pitch of 0.5 mm to 1 mm. From among the positions where the detection operation is performed, the optimal mapping position is searched for, as described below. In the example shown in FIG. 5(b), the detection operation is performed at 11 positions A to K in the X direction, and among these, position F is the position when the mapping lowest point LL was found.

In the above description, the sensor 29 is actually moved in the X direction to repeat the detection operation. However, since the mapping position is the irradiation position of the laser light 60 on the wafer 50 along the X direction, the detection operation may be repeated by changing the emission direction of the laser light 60 in a horizontal plane centered on the Y direction within a range of, for example, ±5° at a pitch of 0.2° to 0.4° while keeping the position of the sensor 29 (or the hand 25) in the X direction fixed. The emission direction of the laser light 60 can be easily changed, for example, by changing the angle of the hand 25 relative to the arm 24. Furthermore, in order to increase the accuracy of determining the optimal mapping position, the detection operation may be performed while shifting the position of the sensor 29 in the Y direction within a range of, for example, ±5 mm.

When the detection operation is repeated while changing the position of the sensor 29 in the X direction, the sensor 29 obtains a detection result as the thickness of the wafer 50 contained in the corresponding slot for each slot of the cassette stage 40 and for each position in the X direction where the detection operation is performed. A series of detection results obtained in this way can be expressed as two-dimensional detection distribution data with the position in the X direction being one dimension and the position of the slot in the Z direction being the other dimension. Figure 6 shows an example of detection distribution data obtained when the number of slots in the cassette stage 40 is 10, the slot positions are numbered 1 to 10 from the bottom, the detection operation positions in the X direction are 11 positions A to K as described above, and each slot stores a silicon wafer with a thickness of 0.9 mm as the wafer 50. The area shown in black in the figure is the area where the sensor 29 detected the wafer 50. The larger the dimension of the area in the Z direction (the vertical direction in the figure) is, the thicker the wafer 50 is detected. The dotted line indicates that the wafer 50 could not be detected even though the wafer 50 is present. The thickness of the wafer 50 actually detected for each position in the X direction and for each slot position is shown in Table 1. The values in Table 1 are in mm.

Once the detection distribution data is obtained, in step 106, the mapping position in the X direction to be used in mapping during actual transport is determined based on the detection distribution data. The determination of the mapping position from the detection distribution data is described below.

In the example shown in FIG. 6 and Table 1, wafers 50 with a thickness of 0.9 mm are stored in each slot of the cassette stage 40, so the position in the X direction where the detected thickness is 0.9 mm in all slots is the most suitable mapping position. When the results in Table 1 are examined from this perspective, at positions A, B, and K, even though there are actually 10 wafers 50 present on the cassette stage 40, some wafers 50 have not been detected. This is thought to be because the irradiation position of the laser light 60 is far away from the center position of the wafer 50 in the X direction, so that the laser light 60 cannot be correctly reflected at the edge of the wafer 60, and therefore the wafer 50 cannot be correctly detected. Since the mapping results are unreliable, mapping should not be performed at these positions A, B, and K.

At positions F, G, and H, there are slots where the wafer 50 is detected as being 2 to 4 mm thick, even though the actual thickness of the wafer 50 is about 1 mm. Also, even though the wafer 50 being detected is of the same thickness, there is a variation of more than twice the detected thickness. This is thought to be due to over-reflection occurring due to the reflection angle of the laser light 60 on the wafer 50. In this state, it is unreliable to detect whether or not the wafers are overlapping in the slot from the detected wafer thickness, so mapping should not be performed at these positions F, G, and H.

Since positions A, B, F, G, H, and K are not suitable as mapping positions, a position in the X direction suitable for mapping is selected from the remaining positions C, D, E, I, and J and is set as the mapping position. Here, position D or position I is set as the mapping position. Once the mapping position has been set in this way, the teaching position previously registered as a position for mapping in step 103 is automatically corrected to the mapping position set this time. The following (1) to (3) are conditions for determining the mapping position.

(1) the average detected thickness is closest to a predetermined thickness (e.g., the thickness of the wafer 50);
(2) The smallest variation in all detected thickness values;
(3) The difference between the maximum and minimum detected thicknesses is smallest.

When determining the mapping position, any one of conditions (1) to (3) may be used, two of these conditions may be used, or all of conditions (1) to (3) may be used. In the above, the detection operation is performed while shifting the position in the X direction, but the detection operation may be performed in the same manner while shifting the axial angle of the hand 25 relative to the arm 24 and the Y direction position of the sensor 29 to find the axial angle and Y direction position that give stable detection results, and the mapping position may be determined by combining at least one of the axial angle and Y direction position of the hand 25 with the X direction position.

By executing the processes of steps 101 to 106, the optimal mapping position for performing mapping to determine the presence/absence status of wafers 50 on the cassette stage 40 is determined. Once the mapping position has been determined in this way, mapping is performed at the determined mapping position when the transport robot 20 is actually operated to transport the wafers 50. The teaching position registered as the mapping position in step 103 to move the hand 25 so that the laser light 60 irradiates the center position of the wafer 50 in the X direction is corrected to the mapping position determined as described above in step 106, so that mapping during actual transport can be performed by moving the hand 25 to the teaching position registered for mapping.

In order to complete mapping in the shortest time, the sensor 29 is moved upward or downward once within the mapping range at a specified mapping position to perform the detection operation. However, in order to further improve the accuracy of mapping, the sensor 29 can be moved in a reciprocating motion that combines upward and downward movements to perform the detection operation, and the detection values of the forward and backward movements can be averaged. When mapping is performed by a reciprocating motion, it is preferable to determine two different mapping positions in step 106 and perform the detection operation at different mapping positions on the forward and backward journeys. In the example shown in FIG. 6 and Table 1, if positions D and J are determined as the mapping positions, as shown in FIG. 7, the detection operation is performed at mapping position D when the sensor 29 rises, and the detection operation is performed at mapping position J when the sensor 29 falls, and then the detection results are averaged for each slot to obtain the final mapping result. In FIG. 7, the thick line 70 indicates the trajectory of the irradiation position of the laser light 60.

In the transport robot 20 of this embodiment described above, detection distribution data is acquired by performing a detection operation while changing the position in the X direction on the cassette stage 40 in which wafers 50 are accommodated in all slots, and the optimal mapping position is automatically determined from this detection distribution data. The determined mapping position is then used when actually transporting the wafers 50 thereafter. As a result, it becomes possible to accurately perform mapping that determines the presence or absence of wafers 50 on the cassette stage 40 using a reflective sensor without manually adjusting the mapping position.

20: Transport robot; 21: Base; 22 to 24: Arm; 25: Hand; 26: Fork portion; 29: Sensor; 30: Robot controller; 40: Cassette stage; 50: Wafer; 60: Laser light; 70: Mapping path.

Claims (11)

A conveying device that conveys a workpiece to a storage section that has a plurality of slots arranged in a first direction and can accommodate one workpiece in each of the slots,
A hand that holds the workpiece when transporting the workpiece;
A reflective sensor that irradiates light onto the workpiece and detects reflected light;
a moving mechanism that moves the hand and the sensor relative to the storage unit;
A control means for driving and controlling the moving mechanism,
the control means moves the sensor toward a position of the accommodation unit where the workpieces are accommodated in all of the slots one by one, and then moves the sensor along the first direction to detect the reflected light from the workpiece, and repeatedly executes this operation by moving an irradiation position of the light from the sensor on the workpiece along a second direction perpendicular to the first direction on the front surface of the accommodation unit to obtain detection distribution data, and determines a mapping position based on the detection distribution data;
A conveying device, wherein the mapping position is a position along the second direction of the irradiation position when the sensor is moved along the first direction to perform mapping to determine the inventory status of the work in the storage section. The conveying device according to claim 1, wherein the control means moves the sensor along the first direction in front of the storage unit before acquiring the detection distribution data, and determines the movement range of the sensor along the first direction when acquiring the detection distribution data and when performing the mapping. The conveying device according to claim 1 , wherein the sensor is attached to the hand. The conveying device according to any one of claims 1 to 3, wherein the workpiece is a plate-like object that is horizontally accommodated in the slot, and the first direction is a vertical direction. The transport device according to any one of claims 1 to 4, wherein the control means executes control to perform mapping for the storage unit using the determined mapping position when controlling the moving mechanism to transport the workpiece. The conveying device according to claim 5, wherein the control means determines a first mapping position and a second mapping position from the detection distribution data, and when performing the mapping, moves the sensor at the first mapping position along the forward direction of the first direction, and then moves the sensor at the second mapping position along the reverse direction of the first direction. A mapping method for determining an inventory status of a workpiece in a storage unit having a plurality of slots arranged in a first direction, each slot being capable of storing one workpiece, comprising:
a moving step of moving a reflective sensor toward a position of the accommodation unit in a state where the workpiece is accommodated in each of the slots;
an acquisition process for acquiring detection distribution data by repeatedly performing an operation of detecting the reflected light from the workpiece by moving the sensor along the first direction after the moving process, while moving an irradiation position of the light from the sensor on the workpiece along a second direction perpendicular to the first direction on the front surface of the storage section;
determining a mapping position based on the detection distribution data;
having
A mapping method, wherein the mapping position is a position of the irradiation position along the second direction when the sensor is moved along the first direction to perform the mapping. The mapping method according to claim 7, further comprising: moving the sensor along the first direction on the front surface of the housing after the moving step and before the determining step, thereby determining a moving range of the sensor along the first direction during the acquiring step and when performing the mapping. The mapping method according to claim 7 or 8, wherein the workpiece is a plate-like object that is horizontally accommodated in the slot, and the first direction is a vertical direction. The mapping method according to any one of claims 7 to 9, wherein mapping for the storage section is performed using the mapping position when the workpiece is transported after the determination step. 11. The mapping method of claim 10, further comprising: determining a first mapping position and a second mapping position in the determining step; and, when performing the mapping, moving the sensor at the first mapping position along a forward direction of the first direction, and then moving the sensor at the second mapping position along a reverse direction of the first direction.

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