Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
1999-06-24
2001-03-20
Pelham, Joseph (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S411000, C219S413000, C219S483000, C219S494000, C219S486000, C065S118000, C065S162000, C374S124000
Reexamination Certificate
active
06204483
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods and apparatus for rapid thermal processing of large area substrates, such as glass panels for flat panel displays, and, more particularly, to heating assemblies for rapid thermal processing systems.
BACKGROUND OF THE INVENTION
Systems for rapid thermal processing of glass panels for flat panel displays are known in the art. Such systems include a heating assembly and a transport assembly within an enclosure. Glass panels having one or more coatings enter the system in a horizontal orientation and are transported through the system on rotating quartz cylinders. The glass panels pass through a series of preheating zones at increasing temperatures. The preheating zones contain infrared heaters that are oriented perpendicular to the direction of movement of the glass panels. The panels then move through a region where they are exposed to intense ultraviolet radiation supplied by a xenon arc lamp mounted in a reflector. The panels then move through a cooling zone and exit the system at the end opposite the first preheating zone.
An important parameter in the operation of rapid thermal processing systems is temperature uniformity across the surface of the glass panel or other substrate. Prior art systems have provided generally satisfactory performance but have had certain drawbacks.
The system requires a non-contact temperature measurement technique. An optical pyrometer, which measures temperature based on sensed infrared energy, is typically utilized. The conventional prior art approach is to mount a pyrometer sensing head in a fixed position such that a line profile at one location along the direction of workpiece motion is produced. This configuration has limited temperature measurement capability and thus limits the ability to achieve uniform heating.
Prior art rapid thermal processing systems typically utilize long filament infrared heaters positioned at 90° to the direction of glass panel movement. This arrangement produces excellent longitudinal uniformity, but limited lateral uniformity due to edge effects. It is therefore desirable to provide a lamp configuration having improved lateral heating uniformity. Lateral uniformity refers to uniformity in a direction perpendicular to the direction of substrate movement.
As noted above, glass panels typically enter the rapid thermal processing system at one end and exit at the opposite end. The distance between the entrance end and the exit end increases as the dimensions of the glass panels being processed increases. This distance may be unacceptable in some fabrication facilities.
A method for selectively heating a film on a substrate, such as a glass substrate for a flat panel display, is disclosed in U.S. Pat. No. 5,073,698 issued Dec. 17, 1991 to Stultz. A semiconductor wafer heating chamber, including an optical element between a light source and a wafer and an optical pyrometer for measuring wafer heating, is disclosed in U.S. Pat. No. 4,755,654 issued Jul. 5, 1988 to Crowley et al. A long arc lamp for semiconductor wafer heating is disclosed in U.S. Pat. No. 4,820,906 issued Apr. 11, 1989 to Stultz.
All of the known prior art rapid thermal processing systems have had one or more of the drawbacks discussed above. Accordingly, there is a need for improved methods and apparatus for rapid thermal processing of large area substrates.
SUMMARY OF THE INVENTION
According to a first aspect of the invention, a rapid thermal processing system for large area substrates is provided. The rapid thermal processing system comprises a processing chamber, a transport assembly for transporting a substrate through the processing chamber in a substrate transport direction, and a heating assembly for heating the substrate. The heating assembly comprises a bank of elongated heating elements disposed in the processing chamber. The heating elements having longitudinal axes aligned with the substrate transport direction.
The heating elements may have lengths equal to or greater than the length of the substrate in the substrate transport direction. The bank of heating elements may be disposed above the substrate and may extend laterally beyond the edges of the substrate.
The rapid thermal processing system may further comprise a control system for supplying controlled electrical energy to the heating elements. The control system may comprise means for individually controlling the electrical energy supplied to each of the heating elements. The control system may comprise a temperature sensor for sensing a temperature of the substrate and a heating element controller for supplying electrical energy to the heating elements in response to a difference between a sensed temperature profile of the substrate and a desired temperature profile. The control system may further comprise a carriage assembly for scanning the temperature sensor laterally with respect to the substrate to provide a lateral temperature profile.
According to another aspect of the invention, a rapid thermal processing system for large area substrates is provided. The rapid thermal processing system comprises a processing chamber, a transport assembly for transporting a substrate through the processing chamber in a substrate transport direction, and a heating assembly for heating the substrate. The heating assembly comprises first and second banks of the elongated heating elements disposed in the processing chamber on opposite sides of the substrate. The heating elements of at least one of the first and second banks have longitudinal axes aligned with the substrate transport direction. In one embodiment, the heating elements of the first bank have longitudinal axes aligned perpendicular to the substrate transport direction and the heating elements of the second bank have longitudinal axes aligned parallel to the substrate transport direction.
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Fair James E.
Harris Fritz B.
Cole Stanley Z
Intevac, Inc.
McClellan William
Pelham Joseph
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