Electric heating – Heating devices – With power supply and voltage or current regulation or...
Reexamination Certificate
1998-09-11
2001-01-16
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
With power supply and voltage or current regulation or...
C219S486000, C219S214000, C219S494000
Reexamination Certificate
active
06175103
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the control of metallic material heat treatment, particularly of sputtering target heat treatment in electric furnaces.
BACKGROUND OF THE INVENTION
Grieve ovens, also referred to as furnaces, are utilized to process materials at elevated temperatures for homogenization, recrystallization, die pressing, annealing, stress relief, and hot rolling. These heat treatment processes provide methods of controlling grain structures, grain sizes, distributions of alloying elements, and grain orientations. Desirable sizes and shapes are obtained by rolling after the heat treatments. Manual operations are employed to control all heat treatment processes. Operators set the cycle temperature at the setpoint, or the “aim temperature,” of the temperature controller
30
. When the oven is heated to a temperature close to the cycle temperature, materials are loaded in the oven for heat treatment. Heat treatment time begins to count once the oven door is closed.
This manual process has many disadvantages, which leads to improperly heat treated materials and thus waste or defective products.
Exposure time to the cycle temperature might not be consistently controlled. This can be due to the operator failing to initiate the timer properly or to remove the material promptly when cycle time has expired. Since recipe parameters are manually referenced, the operator may reference the cycle time incorrectly.
Variations in temperature control occur since process control is subject to the discretion of individual operator. Mistakes happen for many reasons, such as when the operator incorrectly references the appropriate heat treatment recipe. A different operator assumes control of an ongoing treatment at shift change and may make a mistake as to the temperature parameters. The operator may take more or less than time than average in loading the material, allowing the starting temperature to vary from the expected temperature due to the door being open. Undetected degraded hardware could cause loss of control over the cycle temperature.
This lack of real-time monitoring creates additional disadvantages of the manual system. The lack of an automatic alert wastes time causing an economic loss. Relying on an individual operator to monitor the process closely causes increased labor expense in staffing and training. Moreover, the mundane nature of such manual monitoring makes timely detection difficult.
Improvements using statistical process control are difficult to accomplish since historical temperature data is not automatically gathered. As is the real-time data, the historical data is subject to the errors during manual collection. Moreover, errors are introduced when inputting the manually-collected data for analyzing for statistical process control (SPC) purposes. These additional steps make the time delay and frequency in such calculations problematic.
Therefore, a significant need continues to exist for a manner of controlling heat treatment furnaces to reduce amount of improperly processed materials and to reduce the labor expense.
SUMMARY OF THE INVENTION
The invention addresses these and other problems associated with the prior art by providing an apparatus and method that controls both the heat treatment cycle exposure time and cycle temperature for a heat treatment furnace, especially for the heat treatment of metallic targets used in semiconductor manufacturing. Achieving a consistent control of heat treatment cycle time and temperature for a variety of targets and oven types in the manner disclosed herein results in a consistent product with less required labor.
Consistent with one aspect of the invention, an automated heat treatment controller, operably coupled to the furnace and including an operator interface, maintains the cycle temperature by controlling a setpoint temperature of the furnace, and manages the cycle exposure time during heat treatment by prompting an operator via the operator interface to remove a heat treated target after the cycle exposure time has elapsed.
Consistent with another aspect of the invention, an automated heat treatment method is provided which includes accessing a heat treatment recipe including a cycle temperature and a cycle exposure temperature; executing the cycle exposure time while maintaining the cycle temperature; and prompting the operator to unload the target after the cycle exposure time has elapsed.
These aspects of the invention, as well as others discussed below, allow the automated heat treatment furnace to mitigate human error and variances in furnace performance that would otherwise result in defectively heat treated targets.
REFERENCES:
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Lam Raymond K. F.
Sica Tony
Switzer Edward N.
Biederman Blake T.
Praxair S.T. Technology, Inc.
Pwu Jeffrey
Walberg Teresa
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