Heating – Work chamber having heating means – Having means by which work is progressed or moved mechanically
Reexamination Certificate
1999-11-04
2001-05-22
Wilson, Gregory (Department: 3749)
Heating
Work chamber having heating means
Having means by which work is progressed or moved mechanically
C432S141000, C432S239000, C414S936000, C414S937000, C118S719000, C118S730000
Reexamination Certificate
active
06234788
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to apparatus and methods for thermal processing of substrates.
BACKGROUND
Several types of furnaces are used in the materials processing industry. For example, one type of furnace used for thermal processing in the semiconductor industry is a batch furnace. Batch furnaces typically include a large area that supports and thermally processes multiple substrates simultaneously. Batch furnaces are relatively simple because they have no internal moving parts. However, they are typically energy inefficient and have relatively low throughput and long processing times. In addition, batch furnaces typically can not generate complex or rapid thermal profiles that are required for some applications.
Another type of furnace used in the industry for thermal processing is a belt furnace. Belt furnaces typically comprise an elongated passageway and a plurality of heating elements positioned at locations along the passageway. In operation, substrates are loaded onto a belt or conveyor and transported through the passageway in proximity to the plurality of heating elements at a predetermined speed.
Typically, each of the plurality of heating elements is individually controllable to achieve a predetermined thermal profile. The rate of transport though the passageway is also controllable. Consequently, belt furnaces can achieve a predetermined thermal profile that can be both complex and rapid. Belt furnaces can achieve a significantly higher ramp rate compared to batch furnaces. For example, belt furnaces can heat a substrate with a ramp rate greater than 100 degrees per minute, and cool a substrate with a ramp rate greater than 30 degrees per minute. Such ramp rates are required for certain manufacturing processes, such as reflow processes.
Belt furnaces are generally more energy efficient and simpler to use compared to batch furnaces and can be used to generate complex and rapid thermal profiles. In addition, belt furnaces are less expensive than batch furnaces. However, belt furnaces have a relatively large footprint, and therefore take up valuable clean room space. Belt furnaces also have a long warm-up time, and are relatively difficult to automate. In addition, it is difficult to control the ambient temperature within a belt furnace.
SUMMARY OF THE INVENTION
The present invention relates to a furnace for thermal processing of materials such as semiconductor substrates. It is an object of the invention to provide a furnace that has a relatively high ramp up and ramp down rate. It is another object of the present invention to provide a furnace that has a relatively small physical footprint.
Accordingly, the present invention features a furnace for thermal processing of substrates. The furnace includes a substrate cassette that supports at least one substrate. A vacuum chamber having a gate valve may enclose the substrate cassette. A cassette elevator may be included to vertically position the substrate cassette relative to a transport mechanism.
The furnace also includes a process chamber having a port for receiving and removing substrates from the process chamber. The process chamber may be a cylindrical chamber. A gate valve may be positioned in the port of the process chamber that creates a vacuum seal at the port. An ambient control chamber may be positioned between the process chamber and the substrate cassette. At least one gas transport member may be positioned in the process chamber that introduces a gas into the process chamber. The gas transport member may include an arm that extends radially from the center of the process chamber.
A rotatable member that includes a substrate support is rotatably disposed in the processing chamber. The rotatable member rotates a substrate positioned on the substrate support so that a temperature of the substrate is controlled according to a temperature profile. In one embodiment, the rotatable member comprises a disk-shaped member. A motor drive may be coupled to the rotatable member in order to power the rotation. The motor drive may be coupled to the rotatable member through a vacuum feedthrough. In one embodiment, a controller is in electrical communication with the motor drive and causes the motor drive to rotate the rotatable member at a predetermined time and at a rotation rate.
A heater is positioned in thermal communication with the process chamber. The heater may be positioned on at least one of a top and a bottom of the process chamber. The heater generates a thermal distribution in the process chamber. In one embodiment, the heater includes a plurality of heating elements that are individually controllable. Each of the plurality of heating elements generates a thermal distribution in a respective one of a plurality of regions of the process chamber. A transport mechanism transports substrates between the substrate cassette and the substrate support of the rotatable member. The transfer mechanism may be a robot arm.
The present invention also features a method for thermal processing of materials. The method includes transporting a substrate through a port of a process chamber to a substrate support disposed in the process chamber. A thermal distribution is generated in the process chamber. The thermal distribution in the process chamber may be generated by heating a plurality of regions of the process chamber. The furnace may have a temperature ramp up rate of at least 100 degrees per minute and a temperature ramp down rate of at least 30 degrees per minute. The substrate is rotated through the thermal distribution to expose the substrate to a temperature profile. The substrate is then transported out of the process chamber through the port of the process chamber.
REFERENCES:
patent: 5091217 (1992-02-01), Hey et al.
patent: 5404894 (1995-04-01), Shiraiwa
patent: 5766360 (1998-06-01), Sato et al.
patent: 5944940 (1999-08-01), Toshima
patent: 5951770 (1999-09-01), Perlov et al.
Applied Science and Technology Inc.
Testa Hurwitz & Thibeault LLP
Wilson Gregory
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