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Techniques for Reducing Nh4cl Contaminations in Low Pressure Chemical Vapor Deposition Systems

IP.com Disclosure Number: IPCOM000046641D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Depin, JP: AUTHOR [+4]

Abstract

It has been recognized that NH4Cl crystals are formed inside the reaction tube of low pressure chemical vapor deposition (LPCVD) systems during the Si3N4 deposition. This formation affects both the front and the rear of the reaction tube. Silicon wafers are contaminated by these crystals, and therefore cleaning (e.g., brush cleaning) is required. In addition, in order to reduce this contamination, it is recommended to remove and clean the reaction tube every 40 runs and the H2O getter box every 20 runs. Changing the reaction tube is quite a complex operation, as well as time consuming. One has noticed the tendency of NH4Cl crystals to form in certain of the relatively cold places (360ŒC) of the tube, near the H2O getter box at the rear of the tube and near the exhaust outlet at the front side.

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Techniques for Reducing Nh4cl Contaminations in Low Pressure Chemical Vapor Deposition Systems

It has been recognized that NH4Cl crystals are formed inside the reaction tube of low pressure chemical vapor deposition (LPCVD) systems during the Si3N4 deposition. This formation affects both the front and the rear of the reaction tube. Silicon wafers are contaminated by these crystals, and therefore cleaning (e.g., brush cleaning) is required. In addition, in order to reduce this contamination, it is recommended to remove and clean the reaction tube every 40 runs and the H2O getter box every 20 runs. Changing the reaction tube is quite a complex operation, as well as time consuming. One has noticed the tendency of NH4Cl crystals to form in certain of the relatively cold places (360OEC) of the tube, near the H2O getter box at the rear of the tube and near the exhaust outlet at the front side. Deposition of NH4Cl crystals may be drastically reduced at the rear of the reaction tube by mounting (such as represented in the figure) a metal (such as aluminum) reflector which reduces the thermal gradient between the rear part of the tube and the H2O getter box. With the reflector in place, the reaction tube needs to be cleaned only every 400 runs while the getter box is to be cleaned every 40 runs. Those figures may even be improved a little by introducing a purge of nitrogen through the rear part of the tube, the flow of nitrogen (80 liters/minute is performed before loadin...