End effector

An end effector includes: a hand; a substrate holder provided on the hand; a mapping detector provided at distal end portions and of the hand; a light emitter, which the hand is provided with and which is configured to generate detection light; a light receiver, which the hand is provided with and which is configured to receive the detection light and convert the detection light into an electrical output; and an optical path formed such that the detection light emitted from the light emitter passes through the optical path to be incident on the light receiver; the optical path is formed such that detection light is blocked by a substrate detected in a cassette by the mapping detector, and such that detection light is blocked by a substrate held by the substrate holder.

TECHNICAL FIELD

The present invention relates to an end effector included in a substrate conveying robot for holding and conveying a substrate.

BACKGROUND ART

In a semiconductor manufacturing apparatus, liquid crystal panel manufacturing apparatus, or the like, a substrate conveying robot is used to convey a substrate, such as a semiconductor wafer or a glass substrate, to a desired position precisely while keeping the substrate clean. The substrate conveying robot includes an end effector, which is a suction hand, for example. By means of the suction hand, the substrate conveying robot retrieves a substrate from a cassette in which substrates are stored in a multi-staged manner, and then conveys the substrate while holding the substrate on the hand.

Conventionally, detection of the presence or absence of a substrate in a cassette has been performed by using an optical sensor provided on the distal end of a hand of a robot (see Patent Literature 1, for example). In recent years, a substrate conveying robot capable of quickly detecting the presence or absence of a substrate in a cassette has been disclosed (see Patent Literature 2, for example). The substrate conveying robot includes a hand provided with two different types of optical sensors. A first sensor is installed such that its optical axis is horizontal, and a second sensor is installed such that its optical axis is inclined by a certain angle relative to the horizontal direction.

In the case of a conventional suction end effector, the end effector may not be able to sufficiently suck and hold a substrate if the substrate is bent. If the substrate is conveyed in such a state, there is a risk of the substrate falling from the end effector. Therefore, it is necessary to check whether the sucking and holding of the substrate are sufficient and whether the substrate is stably placed on the end effector.

In this respect, for example, based on information from a pressure switch provided on the hand, the conventional substrate conveying robot determines whether or not a substrate on the hand is bent, thereby detecting whether or not the substrate is properly sucked and held. Patent Literature 3 discloses a conveying robot configured to detect, by means of a transmissive optical sensor provided on a hand, whether or not a substrate has been properly held.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, the above-described conventional substrate conveying robots are unable to perform both the detection of the presence or absence of a substrate in a cassette and the detection of whether or not a substrate has been held properly. If the above-described conventional techniques are combined, it becomes necessary to include a plurality of sensors. Thus, there arises a problem in that the circuit configuration of the sensors becomes complex.

The present invention has been made to solve the above-described problems. An object of the present invention is to provide an end effector included in a substrate conveying robot, the end effector being capable of performing, with a simple configuration, the detection of the presence or absence of a substrate in a cassette and the detection of whether or not a substrate has been held properly.

Solution to Problem

In order to solve the above-described problems, an end effector according to one aspect of the present invention includes: a hand; a holder provided on the hand and configured to hold a first substrate; a mapping detector provided at a distal end portion of the hand, the mapping detector being configured to face a second substrate stored in a cassette and detect presence or absence of the second substrate; a light emitter, which the hand is provided with and which is configured to convert an electrical input to generate detection light; a light receiver, which the hand is provided with and which is configured to receive the detection light and convert the detection light into an electrical output; and an optical path formed in the hand, through which the detection light emitted from the light emitter passes to be incident on the light receiver. The optical path is formed such that the detection light is blocked by the first substrate held by the holder, and such that the detection light is blocked by the second substrate detected by the mapping detector.

According to the above configuration, depending on whether or not the detection light travelling through the optical path has been blocked, the electrical output changes in accordance with a change in a received light amount detected by the light receiver. A substrate holding state detection operation of detecting the holding state of the first substrate and a mapping detection operation of detecting the presence or absence of the second substrate stored in the cassette are not performed at the same time. Therefore, in each of the substrate holding state detection operation and the mapping detection operation, the electrical output changing in accordance with the received light amount detected by the light receiver is monitored, which makes it possible to detect whether or not the first substrate in a normal condition is set properly and detect the mapping of the second substrate stored in the cassette. Since these two types of detections can be performed by means of one set of the light emitter and the light receiver, the configuration for the detections can be simplified.

Specifically, in the substrate holding state detection operation, if the light is blocked when a substrate has been retrieved and held by the hand, the current state is determined to be a state where a substrate in a normal condition is set properly. On the other hand, if the light passes through, the current state can be determined to be one of the following states: a state where no substrate is present; a state where a substrate in an abnormal condition is set; and a state where a substrate in a normal condition is set improperly.

The optical path may include: a first section formed such that if the first substrate is in a normal condition and is set on the holder properly, the detection light is blocked by the first substrate, and otherwise, the detection light is not blocked in the first section; and a second section formed such that if there is the second substrate stored in the cassette, the detection light is blocked by an outer peripheral portion of the second substrate, and otherwise, the detection light is not blocked in the second section.

The first section and the second section may be provided in series.

The light emitter and the light receiver may include a light-emitting element and a light-receiving element, respectively, and the light-emitting element and the light-receiving element may form a transmissive optical sensor.

Advantageous Effects of Invention

The present invention has an advantage of being able to provide an end effector included in a substrate conveying robot, the end effector making it possible to realize, with a simple configuration, both the detection of the presence or absence of a substrate in a cassette and the detection of whether or not a substrate has been held properly.

The above object, other objects, features, and advantages of the present invention will be made clear by the following detailed description of a preferred embodiment with reference to the accompanying drawings.

DESCRIPTION OF EMBODIMENTS

Hereinafter, one embodiment of the present invention is described with reference to the drawings.

FIG. 1is a side view of a substrate conveying robot100including an end effector1according to one embodiment of the present invention. As shown inFIG. 1, the substrate conveying robot100is installed, for example, in a semiconductor processing facility for manufacturing semiconductor elements. In the semiconductor processing facility, the substrate conveying robot100is utilized for conveying a substrate W, such as a wafer, which is a material of a semiconductor element. Examples of the wafer include a semiconductor wafer and a glass wafer. Examples of the semiconductor wafer include a silicon wafer, a wafer made of a single semiconducting material different from silicon, and a wafer made of a compound semiconducting material. Examples of the glass wafer include a glass substrate for use in FPD, a glass substrate for use in MEMS, and a sapphire (single crystal alumina) wafer. A plurality of treatment devices are installed in the semiconductor processing facility. For example, the treatment devices are devices for subjecting the wafer to heat treatment, impurity introducing treatment, thin film forming treatment, lithography treatment, cleaning treatment, and flattening treatment. The substrate conveying robot100conveys the substrate W to an area (a treatment chamber) in which these treatment devices are disposed. In the present embodiment, substrates W are stored on respective shelves in a multi-staged manner in a cassette6mounted on a cassette stand7.

For example, the substrate conveying robot100includes: the end effector1; an arm2including a first arm2aand a second arm2b; a lifting/lowering shaft3; a base4; and a controller5. In the present embodiment, the substrate W is placed on the end effector1of a horizontal articulated four-axis robot.

The substrate conveying robot100includes the base4, which is fixed to a suitable position (e.g., a floor) in the semiconductor processing facility. The lifting/lowering shaft3is provided on the base4. On the base4, the axis of the lifting/lowering shaft3extends vertically, for example. The base4includes a built-in lifting/lowering actuator (not shown), which is an air cylinder, for example. When the actuator operates, the lifting/lowering shaft3on the top surface of the base4is lifted or lowered vertically.

The elongated first arm2ais provided on the upper end of the lifting/lowering shaft3. The first arm2aextends horizontally from the upper end of the lifting/lowering shaft3. One end of the first arm2ais connected to the lifting/lowering shaft3such that the first arm2ais swingable about a vertical axis. The lifting/lowering shaft3includes a built-in swing actuator (not shown), which is an electric motor, for example. When the actuator operates, the first arm2aswings in a horizontal plane relative to the lifting/lowering shaft3.

The elongated second arm2bis provided on the upper surface side of the other end of the first arm2a. The second arm2bextends horizontally from the other end of the first arm2a. One end of the second arm2bis connected to the first arm2asuch that the second arm2bis swingable about a vertical axis. The other end of the first arm2aincludes a built-in swing actuator (not shown), which is an electric motor, for example. When the actuator operates, the second arm2bswings in a horizontal plane relative to the other end of the first arm2a.

The end effector1, which is configured to hold a substrate W placed thereon, is provided on the upper surface side of the other end of the second arm2b. The end effector1is connected to the other end of the second arm2bsuch that the end effector1is swingable about a vertical axis. The other end of the second arm2bincludes a built-in swing actuator (not shown), which is an electric motor, for example. When the actuator operates, the end effector1swings in a horizontal plane relative to the other end of the second arm2b.

For example, either in accordance with an input from an operating device (not shown) or automatically, the controller5controls the operation of each of the actuators that drive the lifting/lowering shaft3, the first arm2a, the second arm2b, and the end effector1, such that the end effector1moves vertically and horizontally. By suitably controlling the operation speed of each actuator, the end effector1can be caused to move along an intended path in a horizontal plane. In the substrate conveying robot100, the lifting/lowering shaft3, the first arm2a, the second arm2b, and the actuators driving the respective devices form a drive unit30for causing the end effector1to move.

FIG. 2is a plan view of the end effector1ofFIG. 1seen from above. As shown inFIG. 2, the end effector1includes: a hand10; substrate holders11formed on the hand10; a mapping detector12, which is formed in an area extending from distal end portions10band10cof the hand10across notch space21, the mapping detector12being configured to face a substrate W stored in the cassette6and detect the presence or absence of the substrate W; a light emitter13provided in the hand10and configured to convert an electrical input from the controller5to generate detection light; a light receiver14provided on the hand10and configured to receive the detection light and convert the detection light into an electrical output to the controller5; and an optical path15formed in the hand10, through which the detection light emitted from the light emitter13passes to be incident on the light receiver14.

The structure of the hand10is not particularly limited. In the present embodiment, the hand10is formed by using, for example, a plate material that is Y-shaped when seen in plan view. The Y-shaped body includes a single proximal end portion10aand a pair of distal end portions10band10c. The distal end portions10band10cextend from the proximal end portion as two portions branching off from the proximal end portion. The notch space21is formed between the pair of distal end portions10band10c. The proximal end portion10aof the hand is fixed to one end of an attachment plate20, and the body of the hand10extends horizontally from the attachment plate20. The other end of the attachment plate20is swingably connected to the other end of the second arm2b.

The hand10is configured to hold a discoid substrate W placed thereon. Three substrate holders11for holding the substrate W are formed on the upper surfaces of the proximal end portion10aand the distal end portions10band10cof the hand. In the present embodiment, for example, the substrate holders11are configured to be controlled to reduce pressure at portions that come into contact with the substrate W, and thereby the substrate W is sucked and held by these portions. In this manner, the substrate W is held by the substrate holders11.

The optical path15includes: light guiding sections, in which the detection light is guided by light guiding members; and sections in which the detection light travels through space. In the present embodiment, optical fibers15aand15bare used as the light guiding members.

One end of the optical fiber15ais connected to the light emitter13, which is built-in in the attachment plate20of the hand10. The optical fiber15ais laid to extend from the back side of the proximal end portion10aof the hand to the back side of the distal end portion10bof the hand. The optical fiber15aguides the detection light emitted from the light emitter13to the back side of the distal end portion10bof the hand.

One end of the optical fiber15bis connected to the back side of the distal end portion10cof the hand. The optical fiber15bis laid to extend to one end of a rectangular slit15cformed in the proximal end portion10aof the hand (i.e., the end of the slit15cat the distal end side of the hand10). The optical fiber15bguides the detection light that is incident on the back side of the distal end portion10cof the hand to the slit15c. It should be noted that a light-converging element (e.g., a convex lens) and a light-diverging element (e.g., a concave lens), which are not shown, may be disposed as necessary on both sides of each of the optical fibers15aand15b.

The sections in which the detection light travels through space include a first section and a second section. The first section serves as the mapping detector12, in which the detection light travels through the notch space21between the distal end portion10bof the hand and the distal end portion10cof the hand. In the second section, the detection light travels through the slit15cof the proximal end portion10aof the hand and space15dover the proximal end portion10aof the hand.

FIG. 3is a sectional view of the distal end portions10band10cof the hand of the end effector1ofFIG. 2, taken along line A-A′ ofFIG. 2. As shown inFIG. 3, detection light B1(indicated by a one-dot chain line arrow) emitted from an end of the optical fiber15aat the back side of the distal end portion10bof the hand travels through the mapping detector12(i.e., the first section) between the distal end portion10band the distal end portion10cof the hand, and is then incident on an end of the optical fiber15cat the back side of the distal end portion10cof the hand.

FIG. 4is a sectional view of the proximal end portion10aof the hand of the end effector1ofFIG. 2, taken along line B-W ofFIG. 2. As shown inFIG. 4, detection light B2(indicated by a one-dot chain line arrow) emitted from an end of the optical fiber15bat the back side of the proximal end portion10aof the hand travels through the slit15cformed in the proximal end portion10aof the hand10and the space15dover the proximal end portion10aof the hand10(i.e., the second section), and is then received by the light receiver14provided on the attachment plate20of the hand10.

As described above, the first section and the second section are provided on the optical path15in series. The detection light emitted from the light emitter13passes through the optical path15, and is then incident on the light receiver14. That is, a single optical path is formed from the light emitter13through the optical path15to the light receiver14.

FIG. 5is a block diagram showing a control system in the substrate conveying robot100. As shown inFIG. 5, the controller5of the substrate conveying robot100mainly controls: the light emitter13configured to convert an electrical input from the controller5to generate detection light; a light receiver14configured to receive the detection light from the light emitter13via the optical path15including the optical fibers and space, and convert the received detection light into an electrical output to the controller5; the drive unit30for causing the end effector1to move; and the substrate holders31of the end effector1.

In accordance with a control command from the controller5, the drive unit30operates the actuators that drive the lifting/lowering shaft3, the first arm2a, and the second arm2b, which are shown inFIG. 1, thereby causing the end effector1to move vertically and horizontally.

In accordance with a control command from the controller5, the substrate holders11control pressure at portions that come into contact with a substrate W, and thereby the substrate W is sucked and held by these portions. In this manner, the substrate W is held by the substrate holders11.

The light emitter13includes: a light-emitting element16configured to generate and emit detection light; and a drive circuit17configured to apply a voltage Vin to the light-emitting element16to drive the light-emitting element16. In the present embodiment, for example, a light-emitting diode or a laser diode is used as the light-emitting element16. The drive circuit17generates the voltage Vin in accordance with a control signal (an electrical input) from the controller5, and drives the light-emitting element16with the voltage Vin.

The light receiver14includes: a light-receiving element18configured to convert an optical signal into an electrical signal in such a manner that the light-receiving element18generates a voltage Vout in accordance with a received light amount when the light-receiving element18has received the detection light; and an output circuit19configured to amplify the electrical signal and outputs the amplified signal as a detection signal (an electrical output). In the present embodiment, for example, a photodiode is used as the light-receiving element18. The output circuit19outputs the detection signal to the controller5.

Each of the optical fibers forming the optical path15is connected to the light-emitting element16or the light-receiving element18via a connector, which is not shown. Thus, in the present embodiment, the light emitter13and the light receiver14include the light-emitting element16and the light-receiving element18, respectively, and the light-emitting element16and the light-receiving element18form a transmissive optical sensor.

Next, one example of a mapping detection operation of the end effector1is described. As one example, assume here that, in the mapping detection operation, the substrate conveying robot100causes the end effector1to sequentially scan the shelves from the uppermost shelf to the lowermost shelf to detect the presence or absence of a substrate on each shelf.

FIG. 6is a plan view showing the mapping detection operation of the end effector1. As shown inFIG. 6, the scanning is performed, for example, in such a manner that the mapping detector12of the end effector1is caused to face a substrate W stored on the n-th shelf in the cassette6. At the time, when the detection light B1(indicated by a one-dot chain line arrow) emitted from the end of the optical fiber15aat the back side of the distal end portion10bof the hand travels through the mapping detector12(the first section) between the distal end portion10band the distal end portion10cof the hand, if there is the substrate W stored in the cassette6, the detection light B1is blocked by the outer peripheral portion of the substrate W. As a result, the detection light B1is not received by the end of the optical fiber15cat the back side of the distal end portion10cof the hand. That is, on the optical path15, the detection light B1is blocked by the substrate W detected by the mapping detector12.

As described above, the mapping detector12(the first section) is formed such that if there is the substrate W stored in the cassette6, the detection light B1is blocked by the outer peripheral portion of the substrate W, and otherwise, the detection light B1is not blocked.

Next, one example of a substrate holding detection operation of the end effector1is described. For example, if the substrate W is detected on the n-th shelf in the cassette6in the above-described mapping detection operation, then the substrate conveying robot100inserts the end effector1, which is holding no substrate, into the cassette6at the position of the n-th shelf, such that the substrate W stored on the n-th shelf is placed onto the substrate holders11of the hand10. After detecting whether or not the substrate W is properly set on the substrate holders11, the substrate conveying robot100causes the end effector1to retract from the cassette6. In this manner, the retrieving and holding of the substrate W are performed.

FIG. 7AandFIG. 7Bare a plan view and a sectional view showing the substrate holding detection operation in a case where a substrate is held by the end effector1properly. As shown inFIG. 7AandFIG. 7B, the optical path15is formed such that the detection light B2(indicated by a one-dot chain line arrow) is blocked by the substrate W held by the substrate holders11. In a case where the substrate W is in a normal condition and is properly set on the substrate holders11, the detection light B2is blocked by the substrate W. In this case, the current state is determined to be a state where a substrate in a normal condition is set properly.

The optical path15is formed such that the detection light B2is not blocked if the substrate is set improperly.

FIG. 8AandFIG. 8Bare sectional views showing the substrate holding detection operation in a case where a substrate is held by the end effector1improperly.

FIG. 8Ashows a state where the substrate W is bent. In such a case where the substrate in an abnormal condition is set, the detection light B2from the optical fiber15breaches the light receiver14.

FIG. 8Bshows a state where the substrate W is placed not on the substrate holders11but on the light receiver14. In such a case where the substrate in a normal condition is set improperly, the detection light B2from the optical fiber15breaches the light receiver14. That is, in a case where the detection light B2passes through, the current state can be determined to be one of the following states: a state where no substrate is present; a state where a substrate in an abnormal condition is set; and a state where a substrate in a normal condition is set improperly.

Hereinafter, one example of a control operation of the substrate conveying robot100is described with reference to a flowchart ofFIG. 9. As shown inFIG. 9, first, the controller5controls a mapping operation of the end effector1(step1). The substrate conveying robot100causes the end effector1to sequentially scan the first to n-th shelves in the cassette6to detect whether or not a substrate is stored on each of the shelves.

Next, the controller5controls a substrate retrieving operation of the substrate conveying robot100(step2). In accordance with mapping detection results, the substrate conveying robot100causes the arm2to move to a shelf on which a substrate is stored (e.g., the first shelf), and retrieves the substrate from the shelf by the end effector1. Then, the controller5controls a substrate moving operation of the substrate conveying robot100(step3). The substrate conveying robot100causes the arm2to move with the substrate held by the substrate holders11of the end effector1.

Next, after causing the arm2of the substrate conveying robot100to move to a predetermined position, the controller5controls a substrate placing operation of the substrate conveying robot100(step4). In this operation, the holding of the substrate by the substrate holders11of the end effector1is released, and the substrate is placed on the predetermined position.

Then, the controller5repeats the substrate retrieving operation until the retrieval of all the substrates from the inside of the cassette6by the substrate conveying robot100is completed, and ends the control when the retrieval of all the substrates from the inside of the cassette6is completed (step5).

In the above-described flowchart, mapping detection by the end effector1is performed in step1, and substrate holding detection by the end effector1is performed in step2to step4.

Next,FIG. 10is a waveform chart showing input/output waveforms at the time of mapping detection and substrate holding detection by the end effector1in the control operation shown inFIG. 9.

The upper waveform chart inFIG. 10shows control commands from the controller5to the drive unit30and the substrate holders11. The middle waveform chart inFIG. 10shows the control signal inputted from the controller5to the drive circuit17of the light emitter13. If the level of the control signal is High, the drive circuit17applies a voltage Vin to the light-emitting element16of the light emitter13to cause the light-emitting element16to emit light.

The lower waveform chart inFIG. 10shows waveforms of the detection signal outputted from the light receiver14to the controller5. Depending on whether or not the detection light travelling through the optical path15has been blocked, the level of the detection signal (i.e., an electrical output) changes in accordance with a change in a received light amount detected by the light receiver14.

From a time t0to a time t1, the controller5controls the mapping operation of the end effector1. In accordance with a control command from the controller5to the drive unit30, the operation of the substrate conveying robot100shifts to an operation of mapping the substrates W stored on the first to n-th shelves in the cassette6. First, at the time 0, the controller5transmits a control signal of a High level (i.e., ON) to the light emitter13in synchronization with the control command to the drive unit30. Accordingly, the light-emitting element16emits light, and the level of the detection signal becomes High.

During the period from the time t0to the time t1, a substrate W is detected in the cassette6when the detection light B1is blocked. As a result, the level of the detection signal decreases from High to Low. The lower chart inFIG. 10shows a case where substrates are stored on all of the first to n-th shelves. In this case, the detection light B1is blocked n times corresponding to the number (n) of substrates stored in the cassette6. Accordingly, during the period from the time t0to the time t1, the level of the detection signal decreases from High to Low n times. In this manner, the mapping detection by the end effector1is performed.

At the time t1, the controller5controls the substrate retrieving operation of the substrate conveying robot100. In accordance with a control command from the controller5to the substrate holders11, the operation of the substrate conveying robot100shifts to an operation of retrieving the substrate W detected on the first shelf in the cassette6. Also at the time, the controller5continues transmitting a control signal of a High level (i.e., ON) to the light emitter13in synchronization with the control command to the substrate holders11. Here, the level of the detection signal continues to be High.

At a time t2, in accordance with the control command from the controller5to the substrate holders11, the substrate conveying robot100holds the retrieved substrate W. If the substrate W is held properly, the level of the detection signal changes from High to Low.

During the period from the time t2to a time t3, the controller5controls the substrate moving operation of the substrate conveying robot100. The substrate conveying robot100causes the arm2to move with the substrate held by the substrate holders11of the end effector1. At the time, if the substrate W is in a state of being held properly, the level of the detection signal remains Low.

At the time t3, after causing the arm2of the substrate conveying robot100to move to a predetermined position, the controller5controls the substrate placing operation of the substrate conveying robot100. In this operation, the holding of the substrate by the substrate holders11of the end effector1is released, and the substrate is placed on the predetermined position. At the time, the substrate W blocking the space of the mapping detector12at the distal end of the hand is eliminated. As a result, the level of the detection signal becomes High. In this manner, the substrate holding detection is performed during the operations of retrieving, moving, and placing the substrate.

At a time t4, in accordance with a control command from the controller5to the substrate holders11, the operation of the substrate conveying robot100shifts to an operation of retrieving the substrate W detected on the second shelf in the cassette6. Then, when the substrate W of the second shelf is held at a time t5, the detection light B1is blocked. As a result, the level of the detection signal decreases from High to Low. Thus, also in the case of the substrates on the second and the following shelves, the substrate holding detection is performed in the same manner as in the case of the substrate on the first shelf.

According to the above-described configuration, the substrate holding state detection operation of detecting the holding state of the substrate W and the mapping detection operation of detecting the presence or absence of the substrate W stored in the cassette6are not performed at the same time.

Therefore, in the present embodiment, in each of the substrate holding state detection operation and the mapping detection operation, an electrical output (the detection signal) changing in accordance with a received light amount detected by the light receiver14is monitored, which makes it possible to detect whether or not the substrate W in a normal condition is set properly and detect the mapping of the substrate W stored in the cassette. Since these two types of detections can be performed by means of one set of the light emitter13and the light receiver14, the configuration for the detections can be simplified.

It should be noted that the present embodiment adopts a technique of holding the substrate W by suction. In this technique, pressure is controlled at portions of the substrate holders11, the portions coming into contact with the substrate W, and thereby the substrate W is sucked and held by the substrate holders11. However, the manner of holding the substrate is not thus limited, and any configuration capable of holding the substrate may be adopted, so long as the hand is provided with the configuration.

From the foregoing description, numerous modifications and other embodiments of the present invention are obvious to one skilled in the art. Therefore, the foregoing description should be interpreted only as an example and is provided for the purpose of teaching the best mode for carrying out the present invention to one skilled in the art. The structural and/or functional details may be substantially altered without departing from the spirit of the present invention.

INDUSTRIAL APPLICABILITY

The present invention is applicable to an end effector of a substrate conveying robot for conveying a substrate such as a semiconductor wafer or a glass substrate.

REFERENCE SIGNS LIST