Rapid heating and cooling vacuum oven

Details Rapid heating and cooling vacuum oven Rapid heating and cooling vacuum oven

1999-11-24

2001-03-06

Walberg, Teresa (Department: 3742)

Electric heating

Heating devices

Combined with container, enclosure, or support for material...

C118S724000, C118S725000, C392S416000

Reexamination Certificate

active

06198075

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an oven for processing semiconductor wafers and more particularly to an oven having a lightweight processing canister that can be heated and cooled rapidly, surrounded by a thermal insulating canister and a heavy vacuum canister.
BACKGROUND OF THE INVENTION
A trend in semiconductor device manufacturing is to replace the silicon dioxide dielectric layer with a thinner dielectric layer. Materials suitable for thinner dielectric layers include polyimides, BCB and perylene. When polyimides are used, the semiconductor wafer is coated with the polyimide and the wafer is baked at 450° C. for about one hour in order to solidify the polyimide and remove contaminants from the polyimide layer. Since oxygen reacts with the polyimide at high temperatures, the baking must be completed in an oxygen free environment, such as in a vacuum oven or in a diffusion furnace.
Prior art vacuum ovens comprise heavy stainless steel chambers and thus take a very long time to heat up to 450° C. and cool back down to room temperature. Therefore, what is needed by semiconductor manufacturers is a vacuum oven that can be heated and cooled rapidly.
SUMMARY OF THE PRESENT INVENTION
Briefly, the present invention is a rapid heating and cooling oven comprised of a first canister, a second canister and a third canister. The first canister is adapted for holding one or more items to be heated to a temperature of approximately 450° C. A plurality of band heaters positioned around the outside circumference of the first canister provide the heating. A first chamber is formed in the first canister for allowing an inert gas to be introduced uniformly into the first canister and a second chamber is formed in the first canister through which the inert gas is removed.
The second canister encircles the first canister and has an inner surface and an outer surface, with a first cavity being formed between the first canister and the inner surface of the second canister. The heating elements for heating the first canister are positioned in the first cavity in thermal contact with the outside of the first canister. The inner surface of the second canister has a reflective finish so that heat is reflected back toward the first canister.
The third canister encircles the second canister and is adapted to hold a vacuum of at least approximately one torr around and inside of the first and second canisters. An inert gas inlet is positioned so as to direct an inert gas into the first chamber and a vacuum outlet is positioned so as to allow a vacuum to be drawn on the second chamber.


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