Material or article handling – Elevator or hoist and loading or unloading means therefor – Grab
Reexamination Certificate
1997-03-12
2001-04-10
Werner, Frank E. (Department: 3652)
Material or article handling
Elevator or hoist and loading or unloading means therefor
Grab
C414S937000, C414S416060, C414S941000, C414S744300, C414S226010, C901S040000
Reexamination Certificate
active
06213708
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to integrated circuit manufacturing and more specifically to simultaneously sorting and/or rearranging of multiple semiconductor wafers contained in a cassette.
2. Description of the Relevant Art
Semiconductor wafers used in integrated circuit manufacturing are usually stacked in slots of a cassette which holds the wafers. Wafers in a cassette typically undergo the same processing steps which is often referred to as a semiconductor “run”. In some instances, however, it may be desirable to perform different processing steps on one or more wafers within a cassette. It may also be desirable to process wafers of a cassette in an order dissimilar from order used in a previous step. Therefore, wafers are sometimes split up into separate cassettes, randomized in their present cassettes, or transferred to another cassette of wafers. Movement of wafers among cassettes is generally carried out using a wafer sorter.
Wafer sorters typically handle one wafer at a time when splitting, transferring, or randomizing wafers within a cassette. In addition, conventional wafer sorters use two cassettes to randomize wafer locations within a target cassette. The wafers may be removed from a first (or target) cassette and stacked in a different order within a second cassette. Sometimes a second cassette may be unavailable, and the randomizing has to be delayed until a second cassette can be found. Because of this, a conventional wafer sort operation may take an unduly long time to complete the split, transfer or randomization operation.
It is therefore desirable that a wafer sorter be devised that handles multiple wafers at a time when splitting, transferring, or randomizing wafers of a cassette. Further, it is desirable that a wafer sorter need not require a second cassette for randomizing wafers of a cassette. A wafer sorter with these features would reduce the time required to order wafers according to the previous or subsequent processing steps. As such, the throughput needed to manufacture an integrated circuit can be reduced when the improved wafer sort characteristics are achieved.
SUMMARY OF THE INVENTION
The problems outlined above are in large part solved by an improved wafer sorting system of the present invention. That is, the wafer sorter system may handle more than one semiconductor wafer of a cassette at one time. Further, the present wafer sorter system does not require a second cassette when randomizing wafers of a cassette. The present wafer sorter system may be used in conjunction with any semiconductor processing tool, or can be used within a processing sequence separate from a processing tool.
In one embodiment, the wafer sorter system includes a “tower” which acts as a base for the components of the wafer sorter system. The wafer sorter system preferably includes multiple movable arms for holding wafers. These arms are located at different elevational levels, each of which are distributed a spaced distance from one another along a vertical axis of the tower. Each arm preferably protrudes horizontally from within the tower to outside the tower. Each arm may rotate horizontally about a portion of the tower in substantially clockwise and counterclockwise directions. The wafer sorter system preferably includes a robotic arm for moving the tower. The robotic arm may move vertically and horizontally, and it may rotate about a vertical axis. The wafer sorter system further preferably includes a belt which forms a substantially oval loop from the top of the tower to the bottom of the tower. The belt is capable of moving one or more arms along a vertical axes into which an arm or a plurality of arms can be rotated.
In an embodiment, each arm is hollow, and a vacuum conduit is contained partially inside each arm for applying a vacuum suction to each arm. A vacuum suction is a force sufficient to hold a wafer against each arm. The vacuum conduit preferably extends from a port of each arm to a vacuum system. In another embodiment a vacuum system is connected to the bottom of the tower. A valve is preferably disposed within each arm to control when a vacuum suction is applied from the vacuum system to each arm for holding the wafer.
In an embodiment, each arm preferably includes an opening, in its upper surface through which the vacuum source is drawn. In another embodiment, each arm preferably includes a plurality of openings in its upper surface. A plate is preferably attached to an end of each arm on the inside of the tower. The width of the plate is preferably longer than the width of the arm. A clamp may be attached to the arm which may be clamped to a handle extending from the belt. Each handle is preferably an elongated arm. Two handles which are opposite to each other are connected to different sides of the belt at every level of the tower. An arm motor and shaft may be attached to the bottom of each arm. Further, each shaft contacts an inner surface of the tower so that each arm may be moved to the belt when the shaft rotates. A belt motor and shaft are located near the bottom of the belt. This shaft contacts the belt in order to move the belt in a clockwise direction when the shaft rotates. A computer is preferably used to program the movements of each arm and to control when the vacuum suction is applied.
In an embodiment, the tower includes several slots in its body that allow each arm to extend from within the tower to a point outside of the tower. A first interior slot preferably exists for each arm of the wafer sorter system. The first interior slot allows an arm to move horizontally in a counterclockwise direction from its original position to a position near one portion of the belt. The first interior slot further allows the same arm to move in a clockwise direction from its original position to a position near another portion of the belt. A second slot may extend from the top of the tower to the bottom of the tower to allow arms to move vertically down the tower. A third slot may extend from the top of the tower to the bottom of the tower to allow arms to move vertically up the tower.
In an embodiment, when sorting wafers of a cassette, the robotic arm moves the tower to a position near the cassette which allows each arm to be placed under a wafer located in a slot of the cassette. The vacuum suction is preferably is applied to only those arms which contact wafers that need to be moved for sorting. When the vacuum suction is applied to an arm, a wafer preferably becomes attached to the arm. Each arm motor may be activated in order to rotate a shaft which moves an arm about the tower from its original position in a direction either 90 degrees clockwise or 90 degrees counterclockwise. The shaft's rotation direction may be pre-programmed so that each arm moves in almost any desired direction. An arm preferably rotates about the tower in a clockwise direction if the wafer needs to be moved down in a cassette. An arm preferably rotates about the tower in a counterclockwise direction if the wafer needs to be moved up in a cassette.
In an embodiment, after an arm is rotated about the tower, it is clamped onto the belt. The belt motor is then activated in order to rotate the belt shaft. The shaft preferably causes the belt to rotate in a clockwise direction. Each arm attached to the belt is preferably moved vertically. The belt motor is programmed to stop running when each arm reaches its destination above or below its first level of location (or point of origination). Once an arm has reached its desired new level, it is unattached from the belt. The arm motor is then activated so that the arm is rotated to a new slot in a cassette, and the vacuum suction is removed so that the wafer remains in the new slot.
In an embodiment, the plate attached to the end of each arm prevents an arm from rotating to a position where another arm is located within the same horizontal plane. If the plate contacts a different arm, rotation is ceased and the rotating arm is preferably maintained in its original pos
Advanced Micro Devices , Inc.
Conley Rose & Tayon
Daffer Kevin L.
Werner Frank E.
LandOfFree
System for sorting multiple semiconductor wafers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System for sorting multiple semiconductor wafers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System for sorting multiple semiconductor wafers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2514603