Handling: hand and hoist-line implements – Grapple – Resilient jaws
Reexamination Certificate
1999-04-14
2001-01-16
Kramer, Dean J. (Department: 3652)
Handling: hand and hoist-line implements
Grapple
Resilient jaws
C294S001200, C414S941000
Reexamination Certificate
active
06174011
ABSTRACT:
FIELD OF INVENTION
The present invention relates to techniques and apparatus for holding, handling and transporting thin workpieces; being more specifically concerned with flat pieces such as semiconductor wafers, magnetic recording discs, flat panel displays and other thin and flat workpieces, particularly, though not exclusively, as they may be handled and transported between workstations or wafer cassettes and the like.
BACKGROUND OF INVENTION
The art is replete with many types of such handling mechanisms, including apparatus specifically designed for holding workpieces like semiconductor wafers, and transporting them between workstations and or wafer cassettes. Among these are mechanisms using an annular ring member to position a wafer and an annular flange or lip to support the workpieces, as suggested, for example, in U.S. Pat. No. 4,584,045, as part of a dry processing system. U.S. Pat. No. 4,749,330 discloses a simpler version of such a means, eliminating the annular positioning ring. In U.S. Pat. No. 5,334,257, as another example, a paddle works in conjunction with a means to lift the workpiece off a fixed annular ring member. U.S. Pat. Nos. 5,584,647 and 5,810,549 disclose such workpiece holding means as an object handling system.
A disadvantage of these and similar approaches, however, is that the workpiece is not held in a manner that secures the workpiece when the gripper is moved in planes other than horizontal. Another disadvantage is that such apparatus is restricted to picking the workpiece up off a pedestal of some sort, and does not allow for picking the workpiece up off a flat surface, or for picking up the workpiece from above.
A different approach has accordingly been suggested, using a vacuum wand or paddle, wherein a flat upper surface with vacuum ports is brought into contact with the underside of a workpiece and suction is applied at the port to secure the workpiece tot he paddle. U.S. Pat. No. 4,770,590 discloses such a means for use in a transport system. U.S. Pat. Nos. 5,064,030, 5,135,349 and 5,765,444 disclose such a means for use in a precision robot arm system. U.S. Pat. No. 5,803,979 discloses a means of making vacuum workpiece holders more robust against contamination of the workpiece that may clog the vacuum lines. A basic disadvantage of this vacuum approach, however, is that the contact between the paddle and the workpiece can result in microscopic mechanical damage to the workpiece or particle contamination of the workpiece. As microelectronic circuitry evolves to smaller features and higher densities, particle contamination even of the backside of workpieces is undesirable. This technique, furthermore, prohibits picking up the workpiece from its front surface, the surface on which micro-electronic circuits are fabricated.
Another prior art proposal for holding workpieces is the use of a plurality of gripping arms or fingers which are mechanically moved relative to one other to change the distance between contact surfaces which, when brought to their minimal separation, clamp the workpiece in place relative to the arm assembly. These means avoid the previously discussed disadvantage of contacting the work-piece surface, and can be used to pick up a work-piece from a substantially flat surface. U.S. Pat. No. 4,900,214 is illustrative of such proposals, disclosing first and second jaws moveable relative to one other along a diameter of the wafer to be transported. In U.S. Pat. Nos. 5,549,444 and 5,700,046, contacting elements are attached to the inner surface of each gripping member in order to support the workpiece from its bottom surface. U.S. Pat. No. 5,566,466 discloses such a means wherein the gripper mechanism is part of a spindle assembly used to rotate the workpiece while it is clamped by the mechanism.
A disadvantage of such approaches resides in the possibility of particle generation by rubbing between adjacent sliding mechanical surfaces. A further disadvantage is the cost of fabricating and maintaining precision tolerances in an assembly of several parts.
The matter of handling a variety of workpiece sizes has also been considered. U.S. Pat. No. 4,971,512, as an illustration, discloses the use of a fork-shaped workpiece support board that carries the workpiece from the bottom with a moveable arm slide provided to capture the workpiece in its horizontal plane. While such constructions are indeed capable of handling a variety of workpiece sizes, they are unfortunately not useful in applications where workpiece cleanliness on front and back sides is important.
Still another approach to solve these pressing problems makes us of a Bernoulli effect on the top side of the workpiece. U.S. Pat. Nos. 5,080,549 and 5,324,155 disclose such a system wherein a paddle with appropriately placed gas exhaust ports is brought into close proximity with the top side of a workpiece. The exhaust ports are configured so that the gas flow creates a low pressure region on the top side of the workpiece causing it to lift up toward said paddle. The workpiece can therefore be lifted from a substantially flat surface and transported from the top side with no contact with the top side of the workpiece.
A disadvantage of this approach, however, is that it may not be used in a vacuum system. A further disadvantage is that it does not provide for high precision centering of the workpiece; and still another disadvantage in that the holding mechanism restricts the transport motion to paths within a horizontal plane or perpendicular to a horizontal plane.
OBJECTS OF THE INVENTION
It is accordingly an object of the present invention to provide a new and improved method of apparatus for handling substantially thin flat workpieces and the like in a manner that provides for repeatable transport of said workpieces between-different locations in a process tool and for repeatable precise location of said workpieces in said locations, and obviating the above-described and other disadvantages and limitations in prior art approaches.
It is a further object to provide a novel handling mechanism that is itself thin in the same dimension as the workpiece is thin, and thereby enables extracting and inserting the workpieces from substantially closed pack configurations, such as wafer cassettes or diffusion tube racks and the like.
Another object is to provide an improved holding mechanism that has no sliding contacting surfaces that may be a source of particle generation and that could contaminate the workpiece; preferably, indeed, contacting the workpiece at its very extreme edges and avoiding contact with either the front or rear surface of the said workpiece, thereby insuring workpiece cleanliness. This structure is sometimes referred to herein as an “end-effector.”
Still a further object of the invention to provide a handling mechanism that automatically and reliably brings the workpiece into a known location relative to the robotic arm to which the mechanism is attached—known with respect to both the mechanical center of the workpiece and the rotational orientation of the workpiece as defined by a location notch or location flat in the case of semiconductor wafer workpieces. This repeatable centering allows the robotic arm repeatedly to position said workpiece in a centered location in processing equipment, such as a spin chuck or a diffusion rack.
The invention has the additional object of providing for a minimal number of parts, and especially a minimal number of moving parts, in order to enhance the reliability of the said mechanism continually to transport and position millions of workpieces.
Another object of the invention to provide a novel mechanism that is also suitable for transporting workpieces from one configuration within an automated process tool to another configuration within said process tool with minimal constraint on the path along which the robot arm travels. An embodiment of the invention is provided that securely holds the workpiece in any orientation with respect to the vertical and horizontal planes of the process tool.
The invention additionally pro
Kramer Dean J.
Rines and Rines
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