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Fabrication Technique for Diffusion Furnace Process Tubes

IP.com Disclosure Number: IPCOM000087989D
Original Publication Date: 1977-Apr-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 35K

Publishing Venue

IBM

Related People

Albert, FJ: AUTHOR [+5]

Abstract

Creating process tubes for use in diffusion furnaces requires a complex process, and when contoured baffles are to be provided within the interior of these process tubes, unique spacers are needed especially when the ends of the baffle are lower than its center region.

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Fabrication Technique for Diffusion Furnace Process Tubes

Creating process tubes for use in diffusion furnaces requires a complex process, and when contoured baffles are to be provided within the interior of these process tubes, unique spacers are needed especially when the ends of the baffle are lower than its center region.

Fig. 1 shows an isometric view of a quartz process tube 10 in which semiconductor wafers may be processed. The basic supporting structure for the process tube 10 is a commercially procured rectangular quartz tube normally measuring 3/4 inch high, 2 1/2 inches wide and 72 inches long. A flat tube is preferred since it facilitates working of the tubes, as well as stacking of the tubes, in the furnace. Mounted within the ends of each tube 10 and designated by phantom lines, there is provided a longitudinally extending quartz baffle or partition 12. As can be seen, these baffles divide the tube into top and bottom portions 14 and 16. A gas inlet tube 18 through which suitable gases may be passed into the interior of the tube may be mounted on the side of the tube.

The process tube is created in the following manner: The baffle comprised of clean quartz stock is positioned in the desired position within the center of the tube by supporting each corner on a carbon block of which only three, 20, 22 and 24, are shown. It is also necessary to support the raised central portion of the baffle especially when the tube is being annealed after welding of the baffle in place. Because the center portion is significantly higher than either of the end portions of the baffle, it is necessary that a unique separable spacer, shown in Fig. 2, be provided to support this central portion. The spacer 30 is comprised of two wedge-shaped tools 32 and 34 which, when fitted together, provide a single spacer having the correct height to support the central portion of the baffle. The wedge-shaped portions are provided with suitably long handles, so that they can be inserted into the tube and forced together under the raised portion of the baffle. By having the spacer separable into two parts, each thinner than the whole, it can be readily removed from the unit after the positioning, welding and annealing steps are complete...