Electrical transmission or interconnection systems – Personnel safety or limit control features
Reexamination Certificate
2001-02-02
2004-01-13
Toatley, Jr., Gregory J. (Department: 2836)
Electrical transmission or interconnection systems
Personnel safety or limit control features
Reexamination Certificate
active
06677690
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the manufacture of semiconductor wafers, and in particular to a system for safeguarding fab operators and workpieces such as semiconductor wafers from harm as the workpieces are transported between tools by a workpiece transport assembly.
2. Description of Related Art
A SMIF system proposed by the Hewlett-Packard Company is disclosed in U.S. Pat. Nos. 4,532,970 and 4,534,389. The purpose of a SMIF system is to reduce particle fluxes onto semiconductor wafers during storage and transport of the wafers through the semiconductor fabrication process. This purpose is accomplished, in part, by mechanically ensuring that during storage and transport, the gaseous media (such as air or nitrogen) surrounding the wafers is essentially stationary relative to the wafers, and by ensuring that particles from the ambient environment do not enter the immediate wafer environment.
A SMIF system has three main components: (1) minimum volume, sealed pods used for storing and transporting wafers and/or wafer cassettes; (2) an input/output (I/O) minienvironment located on a semiconductor processing tool to provide a miniature clean space (upon being filled with clean air) in which exposed wafers and/or wafer cassettes may be transferred to and from the interior of the processing tool; and (3) an interface for transferring the wafers and/or wafer cassettes between the SMIF pods and the SMIF minienvironment without exposure of the wafers or cassettes to particulates. Further details of one proposed SMIF system are described in the paper entitled “SMIF: A TECHNOLOGY FOR WAFER CASSETTE TRANSFER IN VLSI MANUFACTURING,” by Mihir Parikh and Ulrich Kaempf,
Solid State Technology,
July 1984, pp. 111-115.
Systems of the above type are concerned with particle sizes which range from below 0.02 microns (&mgr;m) to above 200 &mgr;m. Particles with these sizes can be very damaging in semiconductor processing because of the small geometries employed in fabricating semiconductor devices. Typical advanced semiconductor processes today employ geometries which are one-half &mgr;m and under. Unwanted contamination particles which have geometries measuring greater than 0.1 &mgr;m substantially interfere with 1 &mgr;m geometry semiconductor devices. The trend, of course, is to have smaller and smaller semiconductor processing geometries which today in research and development labs approach 0.1 &mgr;m and below. In the future, geometries will become smaller and smaller and hence smaller and smaller contamination particles and molecular contaminants become of interest.
A SMIF system includes a minimum volume, sealed pod used for storing and transporting wafers. Within a wafer fab, a first automated transport system is provided for transferring the SMIF pods from one processing tool bay to another (interbay delivery systems), and a second automated transport system is provided for transferring the pods around within each particular bay (intrabay delivery systems). Each tool bay, typically on the order of about eighty feet long, consists in general of a number of processing tools for performing various wafer fabrication functions, and at least one stocker, where the pods may be stored before or after processing. Additionally, as a pod is generally transferred to several processing tools within a particular bay, the pod may be stored in the stocker between processes. A stocker is typically a large unit having a plurality of shelves on which the pods may be stored, and a transport system for transferring pods into and out of the stocker, and for moving pods around within the stocker.
U.S. Pat. No. 5,980,183 to Fosnight, previously incorporated by reference, discloses an intrabay pod storage and transport system comprising a plurality of pod support surfaces, or nests, distributed throughout the tool bay and mounted to the sides, on the front and/or above the tools within the bay. The intrabay pod storage and transport system further includes a transport assembly comprised of at least one robotic pod gripper mounted on horizontal and vertical rails to enable pod transport in the X-Z plane, i.e., along the length and height of the tool bay, to transport the pods between the various storage nests and load ports for the process tool.
Typically, some processing tools within a tool bay are high throughput tools which are capable of performing their particular wafer process at a relatively higher rate than other processing tools. Additionally, some tools within a bay are metrology tools, which in general monitor or test a single wafer from within a pod of wafers. A pod may store, for example, 25 wafers. If a normal throughput tool can process 50 wafers in an hour, the transport system need only supply 2 pods per hour to that tool. However, for metrology tools which can process 50 wafers in an hour, but only use one wafer per pod, 50 pods must be provided to the metrology tool in an hour to keep the tool from sitting idle.
In order to accommodate high throughput and metrology tools, it is known to include a local tool buffer adjacent the tool port of high throughput and metrology tools, so that pods may be stored locally adjacent such tools and quickly transferred to these tools without having to constantly retrieve a pod from the remotely located stocker. Such local tool buffers are generally configured adjacent the high throughput and metrology tools, and include shelves for storing pods, and a transport system for transferring pods to, from, and within the local tool buffer.
U.S. patent application Ser. No. 08/891,543 to Bonora et al., previously incorporated by reference, discloses a local tool buffer including a plurality of nests proximate to high throughput tools and a local transport assembly comprised of at least one robotic gripper capable of transporting the pods in the X-Z plane to transport the pods between the various storage nests and the high throughput process tool at which the nests are located.
Pod storage and transport systems such as those disclosed in U.S. Pat. No. 5,980,183 and U.S. patent application Ser. No. 08/891,543 provide several advantages with respect for example to flexibility of tool bay design and refit, the ease with which the storage and transport system may be scaled to fit tool bays of different sizes, and improved pod delivery times and throughput. However, the coexistence of pod storage and transport systems in a tool bay with the human fab operators within the tool bay present several concerns which must be addressed.
A first concern is to avoid injury to fab operators as a result of collision with the pod transport assembly or pods carried thereby as the transport assembly transports the pods within the tool bay. Fab operators commonly work within the tool bays to monitor the operation of the tools, manually transport pods to and from tools and perform maintenance on the tools within the bay. Semiconductor Equipment and Handling International (SEMI) Draft Document 2843D requires that all high speed horizontal transport of pods by the transport assembly occur above 2135 mm from the floor. Alternatively, the system could be configured for the OSHA minimum egress height of 7′6″. However, the pod transport assembly must be able to lower into the areas occupied by the fab operators (which areas are referred to herein as human/automation common areas) to transfer pods to and from load ports, typically located at 900 mm from the floor, and storage nests in the common areas. Therefore, there is a danger of collision between the transport assembly or pods carried thereby and an operator in these human/automation common areas. There are known safety procedures in place to prevent an operator from being hurt by the moving transport assembly, but these procedures can be ignored by an operator, thus potentially placing the operator in harm's way.
Another concern with the coexistence of the pod storage and transport system and the fab operators is the potential for damage to the workpieces carried in t
Babbs Daniel
Feindel David
Fosnight William J.
Gould Richard
Krolak Michael
Asyst Technologies, Inc.
O'Melveny & Myers LLP
Toatley , Jr. Gregory J.
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