Conveying system

A conveying system according to an embodiment includes a robot and a controller. The controller includes a switching unit. The robot includes an arm unit formed of a hand and a plurality of arms connected rotatably with respect to one another, and a base unit. An arm on a rear end side is connected to the base unit rotatably about a rotation axis, and the hand is rotatably connected to an arm on a front end side. The switching unit switches cylindrical coordinate control for controlling the arm unit such that a trajectory of the hand overlaps with any one of lines radiating from the rotation axis and rectangular coordinate control for controlling the arm unit such that the trajectory of the hand overlaps with none of the lines at a predetermined timing.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2012-018704, filed on Jan. 31, 2012, the entire contents of which are incorporated herein by reference.

FIELD

The embodiment discussed herein is directed to a conveying system.

BACKGROUND

Conventionally widely known are conveying robots that convey a laminated workpiece (hereinafter, referred to as a “wafer”), such as a semiconductor wafer and a liquid crystal panel. Also known are conveying systems provided with such a conveying robot in a local clean room (hereinafter, referred to as a “conveyance room”) arranged between a container of a wafer and a processing room for the wafer.

An area such as the container and the processing room described above (hereinafter, referred to as a “transfer position”) is typically provided at such a position that a rotation axis of a conveying robot is not located on an extension of a trajectory of a hand that accesses the transfer position, that is, at an offset position (refer to Japanese Patent Application Laid-open No. 2008-28134, for example).

The conventional conveying system has room for further improvement to increase throughput in conveying processing of a wafer. Specifically, if all the transfer positions are provided at offset positions as described above, a change in the posture of an arm of the conveying robot tends to be made large, resulting in reduction in throughput in the conveying processing.

SUMMARY

A conveying system according to an embodiment includes a robot and a controller. The controller includes a switching unit. The robot includes an arm unit formed of a hand and a plurality of arms connected rotatably with respect to one another, and a base unit. An arm on a rear end side is connected to the base unit rotatably about a rotation axis, and the hand is rotatably connected to an arm on a front end side. The switching unit switches cylindrical coordinate control for controlling the arm unit such that a trajectory of the hand overlaps with any one of lines radiating from the rotation axis and rectangular coordinate control for controlling the arm unit such that the trajectory of the hand overlaps with none of the lines at a predetermined timing.

DESCRIPTION OF EMBODIMENT

An exemplary embodiment of a conveying system disclosed in the present application are described below in greater detail with reference to the accompanying drawings. It is to be noted that the embodiment below are not intended to limit the present invention.

A conveying system according to an embodiment will be described with reference toFIG. 1.FIG. 1is a top view of a conveyance room2according to the present embodiment. InFIG. 1, a part of the shapes is simplified so as to facilitate explanation thereof.

As illustrated inFIG. 1, an opening and closing device5is arranged in a manner parallel to the conveyance room2as a transfer position into and out of which a laminated workpiece (hereinafter, referred to as a “wafer4”), such as a semiconductor wafer and a liquid crystal panel, is conveyed. Furthermore, a conveying robot10is arranged in the conveyance room2.

The conveyance room2is a clean room referred to as an equipment front end module (EFEM). The conveyance room2is provided with a filter (not illustrated) that purifies a gas on the upper part thereof. A clean air current purified by the filter and flowing downward makes the inside of the housing locally cleaned.

The opening and closing device5opens and closes a lid provided to a container3and is arranged at an opening provided to a side wall of the conveyance room2. The opening and closing device5is referred to as a load port or a FOUP opener, for example, and is typically a device conforming to semiconductor equipment and materials international (SEMI) standards.

The container3is a box container capable of storing therein a plurality of wafers4in a multistage manner in the height direction and is a device referred to as a front-opening unified pod (FOUP) specified in the SEMI standards, for example.

The container3is placed on the opening and closing device5such that the lid of the container3faces the conveyance room2. A movable body provided to the opening and closing device5descends in a sliding manner in the conveyance room2while holding the lid, thereby opening the lid. A circle indicated by a dashed line in each container3represents a storage space for the wafer4.

The conveying robot10can hold the wafer4serving as an object to be conveyed. Specifically, the conveying robot10includes a base unit11and an arm unit20.

The arm unit20includes a robot hand (hereinafter, referred to as a “hand23”) capable of holding the wafer4serving as an object to be conveyed. The arm unit20is supported rotatably in the horizontal direction on the top of the base unit11including a raising and lowering mechanism.

Specifically, the base end of a first arm21is rotatably connected to the top of the base unit11, and the base end of a second arm22is rotatably connected to the top of the front end of the first arm21. Furthermore, the hand23is rotatably connected to the front end of the second arm22. These components can rotate with respect to one another.

With this configuration, the conveying robot10can remove the wafer4from the container3to place the wafer4on the hand23, transfer the wafer4to a predetermined processing room (not illustrated), and convey the wafer4to a target position by moving up and down and rotating the arm unit20. The arm unit20will be described later in detail with reference toFIG. 2.

To cause the hand23of the conveying robot10to enter a transfer position, such as the container3and the processing room, the conveying robot10moves the hand23in a linear trajectory from a predetermined position (hereinafter, referred to as a “standby position”) provided outside of the transfer position. While an explanation will be made of the case where the transfer position is the container3, the transfer position may be the processing room or an aligner.

The conveying robot10, for example, moves the hand23from a standby position6b(refer to a cross inFIG. 1) to a transfer position7bof the wafer4(refer to a circle inFIG. 1) in a linear trajectory (hereinafter, referred to as a “transfer trajectory”), thereby transferring the wafer4into the container3. While the standby position6bindicated by the cross and the transfer position7bindicated by the circle as reference positions are the center position of the wafer4to be placed onto the hand23, the reference position may be provided to any part of the hand23.

The container3positioned in the middle among three containers3is provided such that a rotation axis8of the conveying robot10is positioned on an extension of a transfer trajectory (6b-7b). The rotation axis θ of the conveying robot10corresponds to a rotor shaft to which the base end of the first arm21is rotatably connected on the top of the base unit11.

The conveyance room2is in a rectangular shape viewed from the top, and the conveying robot10is arranged such that the rotation axis θ is located on a line α connecting midpoints of long sides in the conveyance room2. The containers3arranged along the outside of the long side are provided in a manner symmetric with respect to the line α connecting the midpoints.

In this case, the conveying robot10can allow the arm unit20to take two postures symmetric with respect to the transfer trajectory (6b-7b) as the posture (hereinafter, referred to as a “standby posture”) of the arm unit20at the standby position6bcorresponding to the container3positioned in the middle. Specifically, there are two standby postures of a standby posture of the arm unit20indicated by a solid line and a standby posture indicated by a dashed line.

By contrast, the two containers3other than the container3positioned in the middle are provided at such positions that the rotation axis θ of the conveying robot10is not located on an extension of each transfer trajectory (6a-7aand6c-7c), that is, at offset positions.

In the conventional conveying system, a transfer position, such as a container and a processing room, is provided at a position offset from a rotation axis of a conveying robot. When the conveying robot is caused to take a standby posture so as to cause a hand to enter the transfer position provided at the offset position, the posture of an arm unit of the conveying robot is determined to be one posture. Therefore, to access a plurality of transfer positions sequentially, a change in the posture of the arm unit tends to be made large, resulting in reduction in throughput.

To address this, when the hand23is caused to enter the container3provided such that the rotation axis θ of the conveying robot10is positioned on an extension of a transfer trajectory, the conveying system according to the present embodiment selects a standby posture with which a change in the posture of the arm unit20is smaller from a plurality of standby postures.

Specifically, a robot control device controls motions of the conveying robot10. The robot control device controls the motions of the conveying robot10based on instruction data that instructs the conveying robot10in advance to make predetermined motions.

The conveying system determines whether the hand23is being caused to enter the container3provided such that the rotation axis θ of the conveying robot10is positioned on an extension of a transfer trajectory based on the instruction data.

In other words, the conveying system determines whether a plurality of standby postures exist to be subsequently taken based on the instruction data. If a plurality of subsequent standby postures exist, the conveying system selects a standby posture that can be taken in a process with which a change in the posture of the arm unit20is the smallest. The conveying system then moves the conveying robot10to the standby posture thus selected. In the present embodiment, a plurality of standby postures serving as candidates for the posture of the arm unit20at the subsequent transfer position correspond to candidate postures.

Furthermore, if a plurality of subsequent standby postures exist, the conveying system switches from a rectangular coordinate system to a cylindrical coordinate system to generate a trajectory along which the conveying robot10is moved. As a result, it is possible to reduce time for generating the trajectory to cause the hand23to enter the container3provided such that the rotation axis θ of the conveying robot10is positioned on an extension of a transfer trajectory.

Thus, the conveying system according to the present embodiment can increase throughput.

While the shape of the conveyance room2illustrated inFIG. 1is a rectangular, it is not limited thereto. The shape of the conveyance room2may be a polygon or a circle, for example. Furthermore, while an explanation will be made of the case where the arm unit20of the conveying robot10moves in the horizontal direction, the conveying system moves the conveying robot10in the vertical direction besides the horizontal direction simultaneously.

The conveying robot10according to the present embodiment will now be described in detail with reference toFIG. 2.FIG. 2is a schematic perspective view of the conveying robot10according to the present embodiment. As illustrated inFIG. 2, a robot control device30is connected to the conveying robot10, and the robot control device30and the conveying robot10can communicate with each other.

The conveying robot10is a horizontal articulated robot including two arms that rotate in the horizontal direction about vertical axes. Specifically, the conveying robot10includes the base unit11and the arm unit20.

The arm unit20includes the first arm21, the second arm22, and the hand23capable of holding the wafer4serving as an object to be conveyed. The arm unit20is supported rotatably in the horizontal direction on the top of the base unit11including the raising and lowering mechanism.

Specifically, the base end of the first arm21is rotatably connected to the top of the base unit11, and the base end of the second arm22is rotatably connected to the top of the front end of the first arm21. Furthermore, the hand23is rotatably connected to the front end of the second arm22. These components can rotate with respect to one another and are rotated by a mechanism formed of a motor and a reducer, for example. The mechanism formed of a motor and a reducer, for example, may be provided to the base unit11or housed in the arm unit20.

The conveying robot10rotates the first arm21, the second arm22, and the hand23, thereby moving the hand23to a target position. Furthermore, the conveying robot10moves the first arm21and the second arm22synchronously, thereby moving the hand23in a linear manner.

The raising and lowering mechanism included in the base unit11includes a linear motion guide, a ball screw, and a motor. The raising and lowering mechanism converts a rotational motion of the motor into a linear motion, thereby moving the arm unit20up and down along the vertical direction. While the raising and lowering mechanism moves the arm unit20up and down using the ball screw, the raising and lowering mechanism may move the arm unit20up and down using a belt provided along the vertical direction.

With this configuration, the conveying robot10can remove the wafer4from the container3to place the wafer4on the hand23, transfer the wafer4to a predetermined processing room (not illustrated), and convey the wafer4to a target position by moving up and down and rotating the arm unit20.

The processing room is a room arranged in a manner parallel to the conveyance room2and provided with a device that performs predetermined processing, such as chemical vapor deposition (CVD), exposure, etching, and asking, on the wafer4.

While the explanation is made of the case where the conveying robot10according to the present embodiment is a triaxial horizontal articulated robot formed of the first arm21, the second arm22, and the hand23, it is not limited thereto. The conveying robot10may be a horizontal articulated robot having four or more motion axes.

To cause the hand23to enter the container3provided such that the rotation axis θ of the horizontal articulated robot having four or more axes is positioned on an extension of a transfer trajectory, the conveying system selects a standby posture from two or more patterns of standby postures.

The conveying robot10may be a dual-arm robot having two arm units20or may include three or more arm units20. If the conveying robot10is a dual-arm robot, the conveying robot10can perform two operations simultaneously in parallel, such as removing the wafer4from a predetermined conveyance position with a first arm unit20and conveying another wafer4into the conveyance position with a second arm unit20. Furthermore, in the conveying robot10, one second arm unit22may be provided with two or more hands23. In this case, the two or more hands23are provided coaxially in a manner rotatable independently of one another.

The robot control device30is a controller that controls motions of the conveying robot10and includes a selecting unit30aand a switching unit30b. The conveying robot10removes the wafer4from the container3to place the wafer4on the hand23and conveys the wafer4to a target position by moving up and down and rotating the arm unit20in accordance with instructions issued from the robot control device30.

The selecting unit30adetermines whether a plurality of standby postures exist to be subsequently taken based on the instruction data, for example. If a plurality of subsequent standby postures exist, the selecting unit30aperforms processing for selecting a standby posture that can be taken in a process with which a change in the posture of the arm unit20is the smallest.

The selecting unit30a, for example, calculates a rotation amount of each articulated shaft of the arm unit20to select a standby posture with which the rotation amount is the smallest. Furthermore, the selecting unit30amay select a standby posture by taking into account required power for the mechanism formed of a motor and a reducer, for example.

If a plurality of subsequent standby postures exist, the switching unit30bperforms processing for switching from the rectangular coordinate system to the cylindrical coordinate system. The robot control device30then generates a trajectory along which the conveying robot10is moved to a standby posture with which a change in the posture of the arm unit20is the smallest using the cylindrical coordinate system. In addition, the robot control device30performs processing for transmitting motion instructions to the conveying robot10based on the trajectory thus generated.

The conveying robot10then moves the arm unit20to a standby posture with which a change in the posture of the arm unit20is the smallest in accordance with the instructions transmitted from the robot control device30.

The robot control device30performs posture selection processing when the conveying robot10changes its posture into a reference posture. However, the timing of the posture selection processing is not limited thereto. The selecting unit30amay perform the posture selection processing when the conveying robot10causes the hand23to enter the transfer position of the container3.

The reference position of the conveying robot10will now be described in detail with reference toFIG. 3.FIG. 3is a view for explaining the reference posture of the conveying robot10.

As illustrated inFIG. 3, in the reference posture of the conveying robot10, the whole arm unit20is folded so as to be made the shortest with the second arm22and the hand23stacked on the first arm21. Furthermore, in the reference posture of the conveying robot10, each axis of the arm unit20is parallel to the lateral direction (an arrow e inFIG. 3) of the conveyance room2. The robot control device30temporarily returns the conveying robot10to the reference posture and moves the conveying robot10to a predetermined posture.

A change in the posture of the conveying robot10from the reference posture (refer toFIG. 3) will now be described in detail with reference toFIG. 4AtoFIG. 4D.FIG. 4AtoFIG. 4Dare a first view to a fourth view, respectively, for explaining a trajectory of the conveying robot10.

An explanation will be made of the case where the hand23is caused to enter a container3bfrom the reference posture (refer toFIG. 4D). The container3bis provided such that the rotation axis8of the conveying robot10is positioned on an extension of a transfer trajectory. Therefore, there are two standby postures of the arm unit20at a standby position corresponding to the container3bthat are symmetric with respect to the transfer trajectory as illustrated inFIG. 4C.

The reference posture serving as the starting point of the trajectory of the conveying robot10is also symmetric with respect to the transfer trajectory with the arm unit20of the conveying robot10positioned on the extension of the transfer trajectory corresponding to the container3b. Therefore, there are two trajectories of the conveying robot10that are symmetric with respect to the transfer trajectory as illustrated inFIG. 4AandFIG. 4B. Thus, the changes in the posture of the arm unit20are the same in both the trajectories.

In this case, in selection of a standby posture that can be taken in a process with which a change in the posture of the arm unit20is the smallest from a plurality of standby postures to be subsequently taken, the selecting unit30amay select either of the standby postures.

A change in the posture of the conveying robot10from an offset position will now be described in detail with reference toFIG. 5,FIG. 6AtoFIG. 6C, andFIG. 7AtoFIG. 7C.FIG. 5is a view for explaining the offset position of the conveying robot10.FIG. 6AtoFIG. 6CandFIG. 7AtoFIG. 7Care views for explaining a trajectory of the conveying robot10.

As illustrated inFIG. 5, in addition to the container3and processing rooms9ato9c, the conveyance room2may be provided with another device, such as an aligner8that detects and adjusts (aligns) the directivity of the wafer4.

In the conveyance room2, the conveying robot10removes the wafer4stored in the container3and conveys the wafer4to the aligner8. After the aligner8aligns the wafer4, the conveying robot10conveys the wafer4thus aligned to the processing rooms9ato9c. The conveying robot10then restores the wafer4on which processing is performed in the processing rooms9ato9cto the container3. A circle indicated by a dashed line in each of the processing rooms9ato9crepresents a transfer position of the wafer4.

An explanation will be made of the case where the hand23is caused to enter the processing room9bfrom the aligner8provided at a position offset from the rotation axis θ of the conveying robot10(refer toFIG. 6CandFIG. 7C). The processing room9bis provided such that the rotation axis θ of the conveying robot10is positioned on an extension of a transfer trajectory.

A first pattern of a trajectory of the conveying robot10will now be described with reference toFIG. 6AtoFIG. 6C. To change the posture as illustrated inFIG. 6A, the conveying robot10folds the arm unit20such that the second arm22is stacked on the first arm21.

Subsequently, the conveying robot10rotates the first arm21and the second arm22thus folded in a direction of an arrow100and rotates the hand23on which the wafer4is placed in a direction of an arrow101.

Thus, the arm unit20is in a standby posture at a standby position corresponding to the processing room9bas illustrated inFIG. 6B. Subsequently, the conveying robot10causes the hand23to enter the processing room9bfrom the standby posture (refer toFIG. 6C).

A second pattern of a trajectory of the conveying robot10will now be described with reference toFIG. 7AtoFIG. 7C. To change the posture as illustrated inFIG. 7A, the conveying robot10folds the arm unit20such that the second arm22is stacked on the first arm21in the same manner as in the first pattern.

Subsequently, the conveying robot10rotates the first arm21and the second arm22thus folded in a direction of an arrow102and rotates the hand23on which the wafer4is placed in a direction of an arrow103.

Thus, the arm unit20is in a standby posture at a standby position corresponding to the processing room9bas illustrated inFIG. 7B. Subsequently, the conveying robot10causes the hand23to enter the processing room9bfrom the standby posture (refer toFIG. 7C).

In comparison of the changes in the posture between two standby postures of the first pattern and the second pattern based onFIG. 6AandFIG. 7A, changes in the posture of the hand23(the arrow101and the arrow103) are the same. By contrast, in terms of changes in the posture of the first arm21and the second arm22(the arrow100and the arrow102), the change in the first pattern is smaller than that in the second pattern.

In this case, the selecting unit30aselects the first pattern in which the change in the posture of the arm unit20is smaller from the two standby postures to be subsequently taken.

The selecting unit30aselects a standby posture that can be taken in a process with which a change in the posture of the arm unit20is smaller from the standby postures to be subsequently taken. However, the selection method is not limited thereto, and the selecting unit30amay determine the subsequent standby posture based on a change in the posture of the conveying robot10to a standby posture to be taken after the subsequent standby posture or to a standby posture to be taken thereafter, for example.

Specifically, after the hand23is caused to enter a predetermined transfer position based on the instruction data and the like, the conveying system can further acquire a position to which the conveying robot10is moved. An assumption is made that the instruction data instructs the conveying robot10to convey the wafer4from the aligner8to the processing room9band then move to fetch the wafer4in the processing room9a, for example.

In this case, in terms of a change in the posture of the arm unit20moving from the aligner8to the processing room9b, the change is smaller in the first pattern. By contrast, in terms of a change in the posture of the arm unit20moving from the processing room9bto the processing room9a, the change is smaller in the second pattern. Therefore, the selecting unit30amay select the standby posture of the second pattern in consideration of a change in the posture to the standby posture taken after the subsequent standby posture.

The posture selection processing performed by the robot control device30will now be described in detail with reference toFIG. 8.FIG. 8is a flowchart of a process of the posture selection processing.

The robot control device30performs the posture selection processing illustrated inFIG. 8at a predetermined timing. The robot control device30may perform the posture selection processing at a timing when the conveying robot10changes its posture into the reference posture or at a timing when the conveying robot10causes the hand23to enter the transfer position of the container3, for example.

As illustrated inFIG. 8, the selecting unit30adetermines whether a plurality of standby postures exist to be subsequently taken (Step S101). If a plurality of subsequent standby postures exist (Yes at Step S101), the switching unit30bperforms the following processing.

To generate a trajectory of the conveying robot10, the switching unit30bdetermines whether a trajectory is being generated using the rectangular coordinate system (Step S102). If the trajectory is being generated using the rectangular coordinate system (Yes at Step S102), the switching unit30bswitches the coordinate system to the cylindrical coordinate system (Step S103).

By contrast, if the trajectory is not being generated using the rectangular coordinate system (No at Step S102), the system control goes to Step S104.

Subsequently, the selecting unit30aselects a standby posture that can be taken in a process with which a change in the posture of the arm unit20is the smallest from the standby postures (Step S104).

The robot control device30then generates a trajectory along which the conveying robot10is moved to a standby posture selected at Step S104using the cylindrical coordinate system and moves the conveying robot10based on the trajectory thus generated (Step S105).

The robot control device30causes the hand23to enter the transfer position from the standby position at which the conveying robot10is in the standby posture, causes the hand23to perform transfer processing of the wafer4(Step S106), and terminates the series of processing.

If there are not a plurality of subsequent standby postures at Step S101(No at Step S101), the switching unit30bdetermines whether a trajectory is being generated using the cylindrical coordinate system to generate a trajectory of the conveying robot10(Step S107).

If the trajectory is being generated using the cylindrical coordinate system (Yes at Step S107), the switching unit30bswitches the coordinate system to the rectangular coordinate system (Step S108). By contrast, if the trajectory is not being generated using the cylindrical coordinate system (No at Step S107), the system control goes to Step S109.

The robot control device30then generates a trajectory along which the conveying robot10is moved to a standby posture using the rectangular coordinate system and moves the conveying robot10based on the trajectory thus generated (Step S109).

The robot control device30causes the hand23to enter the transfer position from the standby position at which the conveying robot10is in the standby posture, causes the hand23to perform transfer processing of the wafer4(Step S110), and terminates the series of processing.

The transfer position will now be described with reference toFIG. 9andFIG. 10.FIG. 9is a view for explaining the transfer position.FIG. 10is a top view of a conveyance room2according to a modification.

While the container3and the processing rooms9ato9carranged along the side wall of the conveyance room2have been explained as the transfer positions provided such that the rotation axis θ of the conveying robot10is positioned on an extension of a transfer trajectory in the conveying system according to the present embodiment, the transfer position is not limited thereto.

As illustrated inFIG. 9, for example, the present embodiment may be also applied to the case where the aligner8provided in the conveyance room2is provided such that the rotation axis θ of the conveying robot10is positioned on an extension of a line connecting a standby position6and a transfer position7, that is, an extension of a transfer trajectory.

Furthermore, while the explanation has been made of the three containers3or the three processing rooms9ato9carranged along the side wall of the conveyance room2, the number of transfer positions is not limited thereto. Four of more transfer positions may be arranged.

As illustrated inFIG. 10, for example, the present embodiment may be applied to the case where four containers3are arranged along the side wall of the conveyance room2and a container3damong the containers3is provided such that the rotation axis θ of the conveying robot10is positioned on an extension of a line connecting a standby position6and a transfer position7, that is, an extension of a transfer trajectory.

As described above, to cause a hand to enter a transfer position provided such that a rotation axis of a conveying robot is positioned on an extension of a transfer trajectory, the conveying system according to the present embodiment selects a standby posture with which a change in the posture of an arm unit is smaller from a plurality of standby postures. Furthermore, if a plurality of subsequent standby postures exist, the conveying system switches from a rectangular coordinate system to a cylindrical coordinate system to generate a trajectory along which a conveying robot is moved. Thus, the conveying system according to the present embodiment can increase throughput.