Communications: electrical – Visual indication
Reexamination Certificate
1999-07-26
2002-08-06
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Visual indication
C340S468000, C340S473000, C340S679000
Reexamination Certificate
active
06429783
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to manufacturing methods, and more particularly, to an apparatus and a method for indication of the operational status of equipment used in semiconductor fabrication.
2. Description of the Relevant Art
Fabrication of integrated circuits upon semiconductor substrates (“wafers”) involves numerous pieces of equipment (“tools”), processing steps, and personnel. Wafer fabrication technicians (WFTs) are responsible, in part, for preparing wafers and processing wafers on various tools. Maintenance technicians' duties include maintaining and repairing tools. Tool manufacturer (“vendor”) representatives may be present for evaluating and correcting problems with one or more tools. Engineers determine the required processing steps, a tool to be used for each processing step, and processing parameters to be used by the tool while performing that step. Managers may be responsible for overseeing a portion or all of the fabrication processing steps and coordinating the efforts of personnel associated with those steps. Efficient fabrication requires good communication between all personnel associated with the fabrication process.
A tool may have one of several operational statuses. For example, a tool may have an “up”, “down”, or “qualification” status. A tool with an up status is available to be used for processing wafers. A tool with a down status cannot be used for processing wafers. The tool may have the down status if a problem with the operation of the tool is discovered and corrective action is being taken. The tool may also be given the down status during regularly scheduled preventative maintenance. A tool with a qualification status cannot be used for processing product wafers, which are wafers upon which functional circuits are being fabricated. One or more test wafers, however, may be processed by the tool having the qualification status. Test wafers, which are wafers that do not have functional circuits being fabricated upon them, are typically processed using only a single tool for the purpose of assessing the performance of that tool. The tool may be given the qualification status during routinely scheduled checks of the tool's performance. The tool may also be given the qualification status after corrective action or after preventative maintenance has been performed on the tool having the down status.
Some of the tools used in semiconductor fabrication have multiple chambers within which wafers are processed. Each chamber of these tools may have its own individual operational status. For instance, one chamber may be broken and therefore have a down status while the remaining chambers are in good working order and have up statuses. For multiple-chambered tools, the operational status of the tool refers to the operational status of every chamber of the tool.
Semiconductor fabrication is typically performed in clean rooms. These are special areas in which the quantity of particles in the air is kept extremely low by continually flowing air from the ceiling to the floor and by ensuring the equipment and people in the clean room generate as few particles as possible. This is necessary since any particle that adheres to the surface of a wafer may destroy the integrated circuit being fabricated upon that portion of the wafer. Any device brought into the clean room must be essentially free of particles and further the operation of any device within the clean room must not generate large quantities of particles.
Each tool used in semiconductor fabrication is generally controlled by its own computer. Typically such a computer has one or more terminals next to the tool it controls. Each of these terminals usually consists of a monitor for sending output to a tool user and one or more input devices for the user. An automated factory system is often used to control the flow of wafers among tools and to ensure that the correct processing parameters are used for each wafer. This system is typically connected to the computers controlling the individual tools and this system may also maintain a database of the operational status of each tool. An example of an automated factory system is WorkStream™ sold by Consilium, Inc. of Mountain View, Calif.
It is important that all personnel associated with a tool are kept informed of the tool's operational status. Typically, two different forms of communication are used. The first form involves maintaining a record of the operational status of a tool in a computer database, typically the automated factory system. Personnel can find out the operational status of a given tool by logging onto the automated factory system and reading the operational status off the appropriate screen. The second form of communication is verbal. When a person changes the operational status of a tool, that person can then tell other personnel the tool's new operational status. Additionally, when personnel working with the tool are changed, such as during a shift change, the departing personnel can inform the arriving personnel of the current operational status of a tool.
Several problems can occur with these two forms of indicating the operational statuses of tools. Typically, a WFT is responsible for processing wafers on multiple tools in addition to other duties such as preparing wafers for processing. Preparing wafers for processing may include sorting wafers and performing pre- and post-processing measurement of the wafers. A tool with a down status may be repaired and given an up status by a maintenance technician while the WFT responsible for processing wafers on that tool is performing other duties at a different location. In this case, the maintenance technician will change the status of the tool in the automated factory system; however, since the WFT is not currently present, the maintenance technician cannot inform the WFT verbally of the change in operational status. If the WFT does not have occasion to check the operational status of the tool in the automated factory system, the WFT will not realize the tool is available for use. Hours may elapse before the WFT becomes aware that the tool can be used to process wafers. This idle time of the tool results in lost productivity and increased manufacturing costs.
During shift changes, the departing WFT has to inform the arriving WFT of the operational status of every tool for which he is responsible. Since a single WFT is often responsible for processing wafers on multiple tools, of which one or more of these tools may have multiple chambers, the WFT is required to remember the operational status of every tool in addition to other assignments the WFT may have. If the WFT forgets the operational status of a tool, he or she will have to stop what he is doing to check on the operational status in the automated factory system.
High-level managers may visit the fabrication area to check on the quality of the work being performed. Idle tools represent significant loss of productivity and increase of manufacturing costs. If a manager sees a tool not being currently used, he or she may find the WFT responsible for processing wafers on that tool and require the WFT to explain why the tool is idle. This takes time away from the WFT's duties and decreases his or her efficiency even though the tool may be currently idle for good reason. For example, the tool may have a qualification status, a test wafer may have recently been run on the tool, and the WFT is currently waiting on an assessment of that test wafer.
Tools may also be scheduled to be temporarily removed from production. For instance, a tool may be given a down status for regularly scheduled maintenance or a tool may be given a qualification status for a regularly scheduled check of the tool's performance. In these instances, the WFT that is processing wafers on a tool may be unaware that the tool will be taken out of production at a specific time. If the WFT had a reminder that the tool was to be taken out of production, the WFT could adjust the processing of wafer
Friede Donald K.
Garcia, Jr. Alfredo
McCarthy Michael
Morrissette Kelvinoge
Ramirez Joanna
Advanced Micro Devices , Inc.
Conley & Rose & Tayon P.C.
Daffer Kevin L.
Hofsass Jeffery
Previl Daniel
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