Material or article handling – Apparatus for charging a load holding or supporting element...
Reexamination Certificate
1999-03-31
2001-11-20
Underwood, Donald W. (Department: 3652)
Material or article handling
Apparatus for charging a load holding or supporting element...
C198S341010, C198S464300, C198S575000, C414S940000
Reexamination Certificate
active
06318946
ABSTRACT:
TECHNICAL FIELD
The present invention broadly relates to semiconductor wafer transport apparatus, and deals more particularly with an interlock system which prevents collision of handling equipment and damage to wafers when the equipment is operated in a manual mode by an operator.
BACKGROUND OF THE INVENTION
The high level of automation used in fabricating semiconductor devices relies on sophisticated handling and transport equipment for moving semiconductor wafers between various processing stations. Most handling and transport operations are conducted under automatic control using a programmable logic controller, or other programmed computer which issues control signals for operating the equipment with little or no intervention by an operator. Nevertheless, there are certain situations where operator intervention becomes necessary, consequently the automated wafer handling equipment mentioned above normally includes a series of manual controls that permit the operator to separately control each stage of movement of the wafers. By way of example, standard mechanical interface (SMIF) pods are used to transport a number of wafers which are typically stored in cassettes. The SMIF pod normally includes robotically operated arms that transport wafer cassettes to a stage from which the cassette is in turn automatically transported to another area, or into processing equipment, such as a deposition chamber.
The transport of the wafer-carrying cassette just described is normally carried out completely automatically, without operator intervention. However, the control system for the handling equipment normally has an off-line mode of operation that can be used by an operator to individually control movements of the transport, which might be required during the initial set up of the equipment in preparation for processing a batch of wafers, or to either clean the equipment or test it to ensure that the movements are smooth and accurate. Because the SMIF pod, the transport arms and the stage are all capable of moving in various directions, the possibility exists that a collision may occur between these elements if the operator does not properly operate the manual controls, and in the proper sequence of control movements. For example, the SMIF arm could be actuated so as to attempt to move a cassette onto a stage before a previously placed cassette could be removed from the stage, thus resulting in a collision that could easily damage or destroy wafers and/or the handling equipment. Up to the present time, there have been no means provided for avoiding such collisions of equipment and resultant damage to wafers. Consequently, many wafers and transport equipment are damaged in this manner, causing undesirable down time as well as reduced manufacturing throughput.
It may thus be appreciated that there is a clear need in the art for a safety interlock system, which overcomes each of the deficiencies described above, and prevents damage to wafers and handling equipment when the equipment is under manual control by an operator.
SUMMARY OF THE INVENTION
The present invention provides an interlock system for automatic handling and transport equipment used to fabricate semiconductor devices, such as wafers. The system employs a series of sensors to sense the current condition or position of either wafer cassettes or elements of the transport mechanism. Depending upon the status and position of the cassette and transport elements, manually operable controls are selectively disabled or “locked out” where activation thereof by an operator would result in collision of certain elements of the equipment. A series of visual or audible indicators are used to alert the operator as to the condition of certain transport elements and sub-systems so that the operator will know in advance when it is safe to activate the manual controls to effect cassette movement.
According to one aspect of the invention, an interlock system is provided for use in a semiconductor fabrication operation of the type including a stage for holding and moving semiconductor devices between first and second staging positions, and a transport mechanism which includes an arm to transport the devices from a storage location onto a stage. The interlock system broadly comprises means for sensing the position of the transport arm and for producing a first signal indicative of the position of the arm; means for sensing the position of the stage and for producing the second signal indicative of the position of the stage; and control means responsive to the first and second control signals for controlling the transport mechanism and the stage, such that the movement of the arm and the stage are coordinated with each other so as to prevent an equipment collisions that may damage either the equipment or wafers. As noted above, visual indicators such as LEDs are employed to provide the operator with a visual indication revealing the readiness of either the arm or stage to carry out a safe transport operation. Additionally, lockout means are provided, operated by the control means, for preventing the operation of the transport arm except when the stage is in its home position, and a cassette is not already present on the stage. The interlock means preferably includes an electrically operated switch, such as an electrical relay, for selectively enabling the operation of the transport arm.
According to another aspect of the invention, apparatus is provided for transporting semiconductor devices from a first staging area to a second staging area which is operable both in an automatic and a manual mode. The apparatus broadly includes a wafer stage for staging wafers thereon; a wafer transport mechanism including a transporter arm for transporting wafers from the first to the second stage; and control means for controlling the operation of the wafer stage and the transport mechanism. The control means preferably includes programmed logic means for automatically controlling the operation of transport mechanism when the apparatus is in an automatic mode of operation, and manually operable means for controlling the operation of the transport mechanism when the apparatus is in a manual mode of operation. The apparatus further includes first sensing means for sensing the position of the transport arm and for delivering to the control means a first signal indicative of the position of the transport arm, and second sensing means for sensing the position of the stage and for delivering to the control means a second signal indicative of the position of the stage. Finally, the apparatus includes lock-out means operated by the control means when the apparatus is in the manual mode of operation thereof, which prevents the operation of the transport arm except when wafers are not on the stage and the stage is in its home position.
Accordingly, it is the primary object of the present invention to provide apparatus for transporting semiconductor wafers which includes a lock-out system that prevents damage to equipment or wafers as a result of equipment collisions when the equipment is being manually controlled by an operator.
Another object of the present invention is to provide apparatus as described above which provides the operator with an audible or visual signal alerting the operator to the status or position of each transport element so that the operator knows whether it is safe to initiate movement of a transport element.
A further object of the present invention is to provide apparatus as mentioned above which senses the position of the transport elements, which information is then used by a lockout system to prevent improper operation of the transport element.
A still further object of the present invention is to provide a lock-out system for a semiconductor wafer transport system which prevents equipment collision and damage, thereby increasing thru-put and wafer yield.
These, and further objects and advantages of the present invention will be made clear or will become apparent during the course of the following description of a preferred embodiment of t
Chen Wen-Yao
Liao Shih-Chieh
Lin Li-Ren
Tsay Yuh-Dean
Taiwan Semiconductor Manufacturing Company Ltd
Tung & Associates
Underwood Donald W.
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