Patent Application
20070231108
1. Field of the Invention
Embodiments of the present invention generally relate to a method and apparatus for transferring wafers within a processing system whereby the wafers lie in a plane perpendicular to that of the processing chamber and can be stored in a separate compartment.
2. Description of the Related Art
Moving wafers between processing chambers at a greater speed is essential to lessen downtime and increase productivity in a semiconductor processing line. The more time it takes to transfer a wafer between and into processing chambers, the more time the processing chamber sits idle. An idle processing chamber can result in great financial losses over time.
One way of causing downtime is to have numerous degrees of movement for a wafer. U.S. Pat. No. 6,822,413 to Simondet discloses a transportation system for wafers in which a sensor is present on the wafer moving mechanism that can auto calibrate. The wafer robot pivots around several axes while keeping the wafer in the same plane as the wafer chuck. Because the wafer is in a plane horizontal to the wafer chuck, the processing system will be longer and the wafer will need to travel a greater distance through the system. The robot, because of its several axes of rotation, will require a large space in which to rotate. The arm itself is contained in its own separate chamber, which increases cost and space requirements.
U.S. Pat. No. 6,773,543 to Summers discloses a system for removing and transporting individual die from a wafer. A pickhead arm rotates 90° clockwise so that a removal nozzle is perpendicular to the wafer. The nozzle contacts the wafer on a specific die and then vacuum is applied. The vacuum secures the die to the nozzle so that the die can be removed. While removing a die from the wafer, the nozzle touches the face of the die which can lead to contamination.
U.S. Pat. No. 6,662,673 to Olgado discloses a conventional transfer robot in which a single arm pivots about several axes of rotation and extends to the wafer. The arm comprises a plurality of fingers wherein the fingers grip the wafer on the face of the wafer. The conventional robot runs the risk of contaminating the wafer by touching the wafer on its face. The robot also requires a large amount of space. Also, keeping the wafer in the same plane as the chuck will require more space.
U.S. Pat. No. 6,366,830 to Bacchi et al. discloses a robot assembly for transferring wafers that rotates about three separate axes of rotation. The robot grabs the wafer on the bottom at a position near the center of the wafer. The robot has at least two separate arms that operate on separate wafers, but each arm is interconnected through a common base housing. By holding the wafer along the bottom of the wafer, contamination of the underside of the wafer is a risk. Also, keeping the wafer in the same plane as the chuck will require more space.
U.S. Pat. No. 5,947,677 to Matsushima et al. discloses a cassette transfer mechanism. The cassette is a square shaped cassette and can hold 25 wafers. The cassette holder has sides, bottom support elements and a back surface supporting surface. When viewed from the side, the cassette holder looks like a triangle. The holder elements are not movable toward each other. Also, keeping the wafer in the same plane as the chuck will require more space.
U.S. Pat. No. 5,944,476 to Bacchi et al. discloses a robot assembly for transferring wafers that rotates about three separate axes of rotation. The robot has a hand on the end of the arm. The hand is forked with two distal ends that have vacuum pressure outlets so that vacuum pressure may be applied so that the wafer can be held in position. The forked hand grips the wafer on its face and runs the risk of contaminating the wafer. Also, keeping the wafer in the same plane as the chuck will require more space.
U.S. Pat. No. 5,271,702 to Dobbs et al. discloses transferring a wafer to a processing station by rotating a carousel to the cassette. A manipulator arm is then moved vertically to the wafer. The gripper opens and the arm rotates to the cassette location that overlaps the wafer. Once the arm is rotated, the gripper closes and the arm rotates out of the carousel to the transport position. The processing station door is opened and the arm is moved vertically to the processing station. The arm then rotates, the gripper opens, the arm rotates again out of the processing station, and the processing station door is closed. The gripper comprises at least two circular holders, one of which is in a fixed position and the other of which is movable. The movable holder moves outward as a wafer is placed into the gripper. Once the diameter of the wafer passes the grippers, the movable gripper moves back inward to secure the wafer.
U.S. Pat. No. 5,040,484 to Mears et al. discloses a device for transporting wafers in which a plurality of fingers grip the wafer along its periphery. The fingers are resilient and are machined to conform to the wafer so that a notch is formed. The wafer rests within the notch so that the periphery, bottom and possibly the top of the wafer are touched by the fingers. The fingers do not appear to rotate. By touching the wafer on the top and bottom, the wafer can become contaminated. Also, keeping the wafer in the same plane as the chuck will require more space.
There is a need in the art to provide effective transfer of wafers between chambers. There is also a need in the art to utilize less space for transfer chambers and processing chambers.
The present invention generally comprises a method and apparatus for transferring wafers within a processing system.
The first preferred embodiment involves an apparatus. The apparatus has a vacuum chamber, a wafer chuck in the vacuum chamber, a random access input station, a random access output station, and a rotatable wafer gripper. The wafer chuck is movable between a lowered position and a raised position and has a planar wafer receiving surface. The random access input station is capable of holding one or more wafers perpendicularly to the planar wafer receiving surface. The random access output station is capable of holding the one or more wafers perpendicularly to the planar wafer receiving surface. The rotatable wafer gripper is capable of moving the one or more wafers from a plane perpendicular to the planar surface to a plane parallel with the planar surface.
A second embodiment also involves an apparatus. The apparatus has a metrology chamber, a wafer chuck, and a rotatable, extendable wafer gripper. The rotatable, extendable gripper is capable of moving one or more wafers from a plane perpendicular to the wafer chuck to a plane parallel to the wafer chuck.
A third embodiment involves a method of transferring wafer. The method involves gripping a wafer in a random access input station with an extendable gripper, rotating the gripper about 90° so that the gripped wafer is in a plane parallel to a planar surface or a wafer chuck, releasing the gripped wafer from the gripper onto the planar surface, processing the released wafer, re-gripping the released wafer after the processing with the gripper on the wafer perimeter, rotating the gripper about 90° so that the gripped wafer is in a plane perpendicular to the planar surface of the wafer chuck; and releasing the re-gripped wafer in a random access output station. The gripper has two extendable arms that grip the wafer and is located within a central processing station.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
The present invention describes a method and apparatus for transferring wafers within a processing system. To save space in a processing line it would be beneficial to place wafers in a plane perpendicular to the processing plane during transfer between chambers. Unfortunately, it is not easy to move a wafer from a horizontal processing position to a perpendicular transfer position without contaminating the wafer by touching it on its face. Flipping the wafers to a plane perpendicular to the processing plane could easily involve as much transfer chamber space as is normally required for a horizontal wafer transfer chamber. The instant invention allows transfer of wafers between chambers while conserving space and limiting the size of transfer chambers.
The random input/output stations 6 are randomly supplied with wafers through a door 9 (see
The random input/output stations 6 are random in the sense that they can be randomly accessed through door 9. The gripper arms 3 are only capable of accessing the wafer 2 closest to the chamber 5.
The griper arms 3 are rotated by a gripper rotator 8. The gripper rotator 8 can be any mechanism capable of providing controlled rotational movement of the gripper arms 3. Examples of conventional rotation mechanisms include motors, gears, and pulleys.
In order to pick up a wafer 2 form the random access input/output station 6, the gripper arms 3 must rotate about 90° along the path shown by the arrow A. Once the gripper arms 3 have rotated, the arms are in position to pick up a wafer as shown in
Once the wafer 2 has been gripped by the gripper ends 4 on the gripper arms 3, the gripper arms 3 retract and rotate about 90° counterclockwise to the initial position shown in
Once the wafer 2 has been processed, the wafer chuck 1 is raised to meet the gripper arms 3 as shown in
In the processing chamber, metrology, chemical vapor deposition (CVD), physical vapor deposition (PVD), chemical mechanical polishing (CMP), etching, or combinations thereof may occur.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
