Method and apparatus for transferring a semiconductor substrate

A method and apparatus for transferring a substrate is provided. In one embodiment, an apparatus for transferring a substrate includes at least one end effector. A disk is rotatably coupled to the end effector. The disk is adapted to rotate the substrate relative to the end effector. The end effector may additionally include a sensor coupled thereto. The sensor is adapted to detect an indicia of orientation of the substrate supported by the end effector. In another embodiment, a method for transferring a substrate includes rotating the substrate disposed on an end effector and detecting an indicia of orientation of the substrate.

BACKGROUND OF THE DISCLOSURE

1. Field of the Invention

The embodiments of the present invention generally relate to a method and apparatus for transferring a semiconductor substrate.

2. Background of Invention

Semiconductor substrate processing is typically performed by subjecting a substrate to a plurality of sequential processes to create devices, conductors and insulators on the substrate. These processes are generally performed in a processing chamber configured to perform a single step of the production process. In order to efficiently complete the entire sequence of processing steps, a number of processing chambers are typically coupled to a central transfer chamber that houses a robot to facilitate transfer of the substrate between the processing chambers. A semiconductor processing platform having this configuration is generally known as a cluster tool, examples of which are the family of CENTURA® and ENDURA® processing platforms available from Applied Materials, Inc. of Santa Clara, Calif.

Generally, a cluster tool consists of a central transfer chamber having a robot disposed therein. The transfer chamber is typically surrounded by one or more processing chambers, at least one load lock chamber and sometimes a dedicated orientation chamber. The processing chambers are generally utilized to process the substrate, for example, performing various processing steps such as etching, physical vapor deposition, chemical vapor deposition, ion implantation, lithography and the like. Processed and unprocessed substrates are housed in a substrate storage cassette disposed in a factory interface coupled to the load lock chamber. The load lock chamber is isolated from the factory interface and the transfer chamber by slit valves. Substrates enter the transfer chamber from the substrate storage cassettes one at a time through the load lock. The substrate is first positioned in the load lock after the substrate is removed from the cassette. The load lock is then sealed and pumped down to match the operating environment of the substrate transfer chamber. The slit valve between the load lock and transfer chamber is then opened, allowing the substrate transfer robot to access the substrates disposed in the substrate storage cassette. In this fashion, substrates may be transferred into and out of the transfer chamber without having to repeatedly re-establish transfer chamber vacuum levels after each substrate passes through the load lock.

Some processes such as etching and ion implantation require that the substrate have a particular orientation. Typically, substrates include an indicia, such as a notch or a flat on their perimeters in a pre-defined location, that is typically indicative of the orientation of the substrate. This notch is used as a reference point when orientation of the substrate is required.

Typically, orientation of the substrate occurs in the orientation chamber. The orientation chamber generally includes a platform for rotating the substrate and a sensor for detecting the notch or flat on the substrate's perimeter. For example, the platform disposed in the orientator supports the substrate. A shaft is coupled between the platform and a stepper or servo motor to controllably rotate the substrate. A light source is positioned in the orientator near the edge of the substrate and is directed across the substrate's edge to a sensor. The light source is normally blocked by the substrate's perimeter as the perimeter rotates. As the indicia (e.g., the notch or flat) rotates to a position between the light source and sensor, the light beam passes therethrough and impinges on the sensor. The sensor, in response to the impingement of the light beam, indicates the position of the notch, which accordingly, is indicative of the angular orientation of the substrate. Once the position of the notch is determined, the motor is able to rotate the platform and places the notch in a pre-determined angular position that can be referenced throughout the cluster tool and associated chambers.

Although the use of a dedicated orientation chamber coupled to the cluster tool has traditionally provided a robust process for determining the orientation of a substrate, the demand in the semiconductor industry for reduced cost of tool ownership and increased substrate throughput has made the use of a dedicated orientation chamber undesirable. For example, a dedicated orientation chamber increases the cluster tool hardware and software cost. Moreover, the orientation chamber may utilize a position on the cluster tool that could be allocated to an additional process chamber. Additionally, the use of a dedicated orientation chamber requires a time expenditure that is not directly related to processing. For example, time is spent transferring the substrate into the orientation chamber, clearing the robot arm from the orientation chamber, spinning (i.e., orientating) the substrate and retrieving the substrate. This time is significant as the orientation process takes about six to fourteen seconds to execute.

Therefore, there is a need for an improved method and apparatus for transferring a substrate.

SUMMARY OF INVENTION

One aspect of the present invention generally provides an apparatus for transferring a substrate. In one embodiment, an apparatus for transferring a substrate is provided that includes at least one end effector. A disk is rotatably coupled to the end effector. The disk is adapted to support the substrate while rotating the substrate relative to the end effector.

In another embodiment, an apparatus for transferring a substrate includes an end effector that has a sensor coupled thereto. The sensor is adapted to detect an indicia of orientation of the substrate supported by the end effector.

In another embodiment, an apparatus for transferring a substrate includes a chamber that has a robot disposed therein. An end effector having a disk rotatably disposed thereon is coupled to the robot. At least one sensor is disposed on the end effector and is adapted to detect an indicia of orientation of the substrate as the substrate is rotated on the disk.

In another aspect, a method for transferring a substrate is provided. In one embodiment, a method for transferring a substrate includes rotating the substrate disposed on an end effector and detecting an indicia of orientation of the substrate.

In another embodiment, a method for transferring a substrate includes supporting the substrate on an end effector of a robot and rotating to substrate relative to the end effector.

To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the figures.

DETAILED DESCRIPTION OF INVENTION

FIG. 1depicts a processing system100having one embodiment of a substrate transfer mechanism120of the present invention disposed therein. The exemplary processing system100additionally includes a factory interface102, a transfer chamber104, a least one load lock chamber106and a plurality of process chambers108. One example of a processing system that may be adapted to benefit from the invention is an ENDURA® processing platform, available from Applied Materials, Inc., of Santa Clara, Calif. Although the substrate transfer mechanism120is described disposed in the exemplary processing system100, the description is one of illustration and, accordingly, the substrate transfer mechanism120has utility wherever substrate orientation is desired.

The transfer chamber104is generally fabricated from a single piece of material such as aluminum. The chamber104defines an evacuable interior122through which substrates124are transferred between the process chambers108coupled to the exterior of the chamber104. A pumping system (not shown) is coupled to the chamber104through a pumping port114disposed on the chamber's floor to maintain vacuum within the chamber104. In one embodiment, the pumping system includes a roughing pump coupled in tandem to a turbomolecular or cryogenic pump.

The process chambers108are typically bolted to the exterior of the transfer chamber104. Examples of process chambers108that may be utilized are etching chambers, physical vapor deposition chambers, chemical vapor deposition chambers, ion implantation chambers, lithography chambers and the like. Different process chambers108may be coupled to the transfer chamber104to provide a processing sequence necessary to form a predefined structure or feature upon the substrate's surface. A slit valve116is disposed between each process chamber108and the transfer chamber104to maintain isolation between the environments of the chambers108,104except during transfer of the substrate124therebetween.

The load lock chambers106(two are shown) are generally coupled between the factory interface102and the transfer chamber104. The load lock chambers106are generally used to facilitate transfer of the substrates124between the vacuum environment of the interior122of the transfer chamber104and the environment of the factory interface102which is typically held at or near atmospheric pressure. Each load lock chamber106is isolated from the interior122of the transfer chamber104by one of the slit valves116. Each load lock chamber106additionally includes a door126disposed between the chamber106and the factory interface102. The door126may be opened to allow the substrate transfer mechanism120transfer the substrate124into the load lock chamber106. After the substrate transfer mechanism120is removed from the load lock chamber106, the door126is closed to isolate the load lock106. Once the atmosphere within the load lock106is substantially equal to that of the transfer chamber104, the slit valve116is opened and the substrate124is retrieved into the interior122of the transfer chamber104. Transfer of the substrate124from the transfer chamber104to the load lock106is performed similarly in the reverse order.

A first transfer robot112A and a second transfer robot112B are disposed in the interior122of the transfer chamber104to facilitate transfer of substrates between the process chambers108. The robots112A,112B may be of the dual or single blade variety. The robots112A,112B typically have a “frog-leg” linkage that is commonly used to transfer substrates in vacuum environments. The first robot112A is generally disposed in an end of the transfer chamber104adjacent the load locks106. The second robot112B is disposed in an opposite end of the transfer chamber104such that each robot112A,112B services the adjacent process chambers108. One or more transfer platforms118are generally provided in the interior122of the chamber104to facilitate substrate transfer between robots112A,112B. For example, a substrate retrieved from one of the load locks106by the first robot112A is set down on one of the platforms118. After the first robot112A is cleared from the platform118supporting the substrate124, the second robot112B retrieves the substrate from the platform118. The second robot112B may then transfer the substrate to one of the process chambers108serviced by the second robot108at that end of the transfer chamber104.

To facilitate process control of the system100, a controller (not shown) comprising a central processing unit (CPU), support circuits and memory, is coupled to the system100. The CPU may be one of any form of computer processor that can be used in an industrial setting for controlling various drives and pressures. The memory is coupled to the CPU. The memory, or computer-readable medium, may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. The support circuits are coupled to the CPU for supporting the processor in a conventional manner. These circuits may include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like.

The factory interface102generally houses the substrate transfer mechanism120. The factory interface102generally includes a plurality of bays128on the side opposite the transfer chamber104. The bays128are configured to accept a substrate storage cassette130. Opposite the bays128are ports136that coupled the factory interface102to the load lock chambers106. The substrate transfer mechanism120is typically coupled to a guide132that is movably disposed on a rail134. An actuator (not shown) is coupled between the factory interface102and the guide132so that the guide132and substrate transfer mechanism120may be controllably positioned along the rail134. Thus, the substrate transfer mechanism120may be positioned proximate any of the cassettes130or the load locks106to facilitate transfer of the substrate124therebetween. An example of one factory interface that may be adapted to benefit from the invention is described in U.S. patent application Ser. No. 09/161,970, filed Sep. 28, 1998 by Kroeker, which is hereby incorporated by reference in its entirety.

FIG. 2depicts one embodiment of the substrate transfer mechanism120. The substrate transfer mechanism120generally includes a body202, a shaft204, a robot arm206and an end effector208. The body202generally houses the robot's motor. The shaft204extends from the body202and is rigidly coupled to the robot arm206. The shaft204may controllably rotate, extend and retract into the body202as directed by the controller. The arm206includes a first strut210and a second strut212that are pivotally coupled at an elbow214. The first strut210is rigidly connected to the shaft204opposite the elbow214. A wrist216couples the second strut212to the end effector208. The wrist216is generally rigid but may optionally pivot or include a rotary actuator. An example of a transfer mechanism that may be adapted to benefit from the invention is described in U.S. patent application Ser. No. 09/272,658, filed Mar. 18, 1999 by Sundar, which is hereby incorporated by reference in its entirety.

The end effector208of the substrate transfer mechanism120generally retains and supports the substrate during transfer between locations. The end effector208generally includes a plurality of seats218disposed thereon. Each seat218is typically fabricated from a polymeric material to minimize particle generation and substrate scratching which could occurs when the substrate is in contact with the seats218. Each seat218typically includes a base220and a lip222. The base220is generally parallel to the end effector208and supports the bottom of the substrate. The lip222projects from the base220and is typically perpendicular thereto. The seats218are generally disposed on the end effector208such that the lips222bound the perimeter of the substrate when seated on the seats218. In one embodiment, the lip222is curved to substantially equal the radius of the substrate. As such, the lips222prevent the substrate124from sliding off the bases220of the seats218as the end effector208is moved by the substrate transfer mechanism120.

FIG. 3depicts a plan view of the substrate transfer mechanism120illustrating the motion of the end effector208about the body202. The motion illustrated inFIG. 3may be referred to as “polar” motion. In a rotational mode, the end effector208may be rotated about the body202of the substrate transfer mechanism120by rotating the shaft204while the elbow214maintains an angle302constant between the first strut210and the second strut212. In the rotational mode, the end effector208is maintained at a constant radius from the centerline of the shaft204. In a extension or retraction mode, the end effector208may be extended and retracted by rotating the shaft204while engaging a linkage (not shown) in the elbow214to increase or decrease the angle302between the first strut210and the second strut212. For example, when the shaft204is rotated clockwise while the angle302is decreased, the end effector208moves towards the body202of the substrate transfer mechanism120. In a combined mode, the rotational and extension/retraction modes are combined to produce a hybrid motion.

The end effector208generally includes a disk304and one or more orientation sensors308disposed thereon. The disk304is generally rotatably disposed on the end effector208. The disk304, which may be maintained in contact with or be actuated to contact the substrate disposed on the end effector208, may be rotated so that an indicia306of the substrates orientation (i.e., a notch, flat or the like) may be rotated above the orientation sensor308. The orientation sensor308, which is coupled to the controller, provides a signal that is indicative of the indicia's position proximate the orientation sensor308, thus establishing the substrate's orientation on the end effector208. The disk304may include an optional vacuum port334disposed therein to retain the substrate to the disk304.

In one embodiment, the end effector208generally includes a center portion310having a first tab312, a second tab314and a third tab316extending therefrom. Each tab312,314,316has one of the substrate support seats218(individually shown as318A,318A and318B) disposed thereon. Generally, the tabs312,314,316are orientated in so that the substrate124is supported by the seats318A,318B when disposed on the end effector208in a stable position that maintains the substrate124on the end effector208without falling during transport. As such, it is contemplated that the geometry of the end effector208is scaled to accommodate substrates of different diameters. Generally, one seat, preferably the seat318A that is disposed on the first tab312, is movable towards the center portion310to allow the substrate124to be gripped between the seats318A,318B, thereby centering the substrate on the end effector208and disk304.

The first tab312generally couples the center portion310to the wrist216of the substrate transfer mechanism120. In one embodiment, the first tab312includes an actuator, such as a pneumatic cylinder, solenoid or the like, coupled thereto. A plunger322of the is coupled to the seat318A that is disposed on the first tab312. The plunger322, when urged by the actuator308, moves the seat318A inwardly toward the stationary seats318B coupled to each of the second and third tabs314,316, thus gripping the substrate124therebetween.

The second tab314and the third tab316are disposed on the side of the center portion310opposite the first tab312. Typically, the second tab314and the third tab316are disposed as mirror images to either side of an imaginary line defined between the first tab312and the center of the center portion310.

In one embodiment, a substrate sensor324is disposed on the second tab316for detecting the proximate of an object332to the end effector208. The sensor324may be an optical sensor. The sensor324may be used alone or in tandem with a reflector or receptor326that is disposed on the third tab318. When the object332disrupts a beam, such as a light wave, passing between the sensor324and the receptor326, a signal is generated by either the sensor324or receptor326indicating the presence of the object332therebetween. As the sensor324and receptor326are position on the second and third tabs314,316outward of the substrate's perimeter when disposed on the end effector208, the sensor324and receptor326may be utilized when the substrate124is disposed on the end effector208. This configuration is particularly useful in detecting objects332such as substrates in the substrate storage cassette130. Alternatively, other types of sensors (used alone or in tandem) that detect the presence of an object may be utilized in place of the sensor324and receptor326, for example, proximately sensors, limit switches, optical sensors, pressure transducers and the like.

At least one orientation sensor308is typically disposed on one of the tabs312,314or316. The orientation sensor308is generally positioned at a radial distance from the center of the center portion310equal to the radius of the substrate for which the end effector208is designed to transfer. The sensor308is typically a proximately sensor that detects the presence of the substrate thereover. Alternatively, the orientation sensor308may be a through beam sensor, a reflective sensor or a CCD camera. Such sensors are generally available from a number of commercial sources such as Keyence Corporation, of Woodcliff Lake, N.J. The orientation sensor308provides a signal indicative of the passing of the indicia306thereover as the substrate124is rotated. For example, the sensor308may have an optical detection means that provides a signal (which may be configured to be no signal) in response to the reflectivity of the substrate when disposed proximate thereto. Since the indicia306provides a discontinuity in the reflectivity seen by the sensor308, the indicia306passing over the sensor308causes a change in signal level. The difference in signals provided by the sensor308in response to the discontinuity (i.e., the indicia306) passing over the sensor308is indicative of the substrate's orientation. The signal information is provided to the controller which logs the event in relation to the angular position of the disk304, thus providing a reference of the substrate's orientation for use when positioning the substrate124in process chambers108which require a particular orientation during processing.

Alternatively, more than one orientation sensor308may be disposed on the end effector208. Since the indicia306typically is disposed in a single location, having multiple sensors308disposed on the end effector208may reduce the time required for the indicia306to rotate over one of the orientation sensors308. For example, a second orientation sensor328may be disposed on the end effector208. In one embodiment, the second orientation sensor328is disposed on the first tab312. Optionally, additional orientation sensors, such as a third orientation sensor330disposed on the third tab316, may be utilized. Any one of the sensors308,328and330may be elongated a radial orientation relative to the center of the disk304so that the indicia306may be detected on substrates that are disposed off-center on the disk304.

Optionally, the orientation sensor308may be disposed remotely to the end effector208. For example, one or more sensors308may be disposed another component of the substrate transfer mechanism120, in the substrate storage cassette130, in the factory interface102, in the transfer chamber104, in the load lock chamber106, in the one or more process chambers108, in the various ports or other locations within the system100where the indicia306disposed on the substrate124may be viewed.

FIGS. 4 and 5depict the end effector208with the disk304removed to show a motor410. A hub402is centrally disposed on the center portion310of the end effector208. The disk304typically includes a flange502that at least partially circumscribes the hub402. A bearing504may be disposed between the flange502and hub402to enhance the rotation to the disk304. An annular pocket414circumscribes the hub402and extends into the center portion310. A pocket bottom412generally extends between an outer wall408and the hub402thereby defining the pocket414.

The motor410is disposed in the pocket414of the end effector208. The motor410generally comprises a casing418that is disposed proximate the outer wall408and includes a plurality of armatures416extending inwardly therefrom. Each armature416includes a core404having a circumscribing conductive winding406. The windings406of alternating armatures416are electrically coupled through the casing418.

The motor410additionally includes a plurality of permanent magnets506are disposed on an outer surface508of the flange502. The magnets506may be disposed on an inner race of the motor410(not shown) that is press-fit or adhered to the flange502of the disk304. As the windings406are energized, the magnets506are urged in a rotary motion that causes the disk304to rotate. The magnets506circumscribe the flange502and are generally arranged in alternating polarity. As the controller (or other power source) energizes the winding406with an alternating current, the windings406alternately attract and repel magnets506having a given polarity as to cause the disk304to rotate on the hub402in a conventional fashion. Alternatively, the disk304may be rotated through other means, for example, a belt, gear assembly or drive shaft coupled to a motor or solenoid positioned on or remote to the end effector206.

Optionally, an encoder510may be coupled to the end effector208proximate the disk304. The encoder510is coupled to the controller150to provide closed-loop information regarding the angular position of the disk304.

FIG. 6depicts another embodiment of an end effector600. The end effector600is generally substantially similar to the end effector208described above except that the end effector600includes an actuator602disposed thereon for elevating the substrate124relative to the end effector600. In one embodiment, a hub604centrally disposed in the end effector600at least partially houses the actuator602. The actuator602, which may be a solenoid, may be actuated to lift the substrate124clear of the seats218as shown. In the lifted position, the substrate124may be rotated by the disk304without touching the seats218, thus minimizing particle generation and the chance of scratching of the substrate during rotation. Other means for actuating the substrate normally to the end effector600include lead screws, pneumatic cylinders, hydraulic cylinders, electromagnetic actuators, cams, fluid jets and the like. A substrate124′ depicted in phantom is shown in a lowered position supported by the seats218.

FIGS. 1 and 3may be referred to during the following description of one mode of operation. Generally, the substrate transfer mechanism120moves proximate one of the substrate storage cassettes130. Using the substrate sensor324and receptor326, the presence of a substrate within the storage cassette130is confirmed before gripping the substrate. The end effector208of the transfer mechanism120then extends into the cassette130to retrieve the substrate. The substrate is gripped by moving the seat318A towards the stationary seat318B. The end effector130is then retracted and the substrate is moved to the load lock106.

Typically during movement of the substrate between the cassette130and load lock106, the first seat318A is moved slightly outward to relax the grip on the substrate. Once the substrate can rotate across the seats318A,318B, the motor assembly410is energized to rotate the disk304. As the disk304supporting the substrate rotates, the indicia306passes over the orientation sensor308, indicating the angular orientation of the substrate. The controller stores the substrate's orientation information in the controller's memory for use when positioning the substrate in those process chambers108that require substrate orientation. Alternatively, the orientation of the substrate occurs while the end effector208is stationary. In another mode of operation, once the orientation of the substrate is determined, the substrate is rotated to place the indicia306in a predefined orientation relative to the end effector208.

As stated above, the substrate transfer mechanism120having the capability for orientating the substrate is not limited to the illustrative embodiment described above. For example, a robot having an end effector that includes a rotating disk and at least one sensor may be utilized outside of a vacuum environment or other chamber.

Another example of a substrate transfer mechanism700is depicted inFIG. 7. The substrate transfer mechanism700generally includes an end effector702coupled to a frog-legged robot704. The end effector702is substantially similar to the end effector208described above. The robot704includes a pair of concentric drive motors706,708regulated by the controller. The robot704includes a pair of robot arms710each including a first strut712rigidly connected to a respective drive706,708. A second strut714of the robot arm710is pivotally connected to the first strut712by an elbow pivot716and by a wrist pivot718to a common rigid connecting member722. The connecting member722is coupled to the end effector702. The structure of the struts712,714and pivots716,718form a “frog-leg” linkage that is actuated in a conventional manner to rotate, extend and retract the end effector702. The substrate transfer mechanism700may be utilized in any number of locations requiring transfer and/or orientation of the substrate. Additionally, the substrate transfer mechanism700may include more than one end effector702, for example, a second end effector coupled to the robot704or to a second robot mounted concentrically to the robot704(second end effector and second robot not shown). One location where the substrate transfer mechanism700may be utilized in dual end effector configuration is in place of one or both of the transfer robots112A,112B disposed in the transfer chamber104ofFIG. 1. An example of a robot that may be modified to benefit from the invention is described in the previously incorporated U.S. patent application Ser. No. 09/272,658.

Although the teachings of the present invention that have been shown and described in detail herein, those skilled in the art can readily devise other varied embodiments that still incorporate the teachings and do not depart from the scope and spirit of the invention.