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Mixed Gas Composition for CVD Reactor Cleaning

IP.com Disclosure Number: IPCOM000019386D
Publication Date: 2003-Sep-12
Document File: 1 page(s) / 91K

Publishing Venue

The IP.com Prior Art Database

Abstract

A blend of 2 to 12 % F2 in NF3 has been proposed for in situ CVD reactor cleans. This blend had been shown to give improved "clean" rates downstream from the primary discharge in a plasma clean step. Unfortunately this mixture represents a much more difficult gas handling challenge than either of the two individual constituents. NF3, a strong oxidizer, can be used in a safe, routine manner if the proper safety precautions are followed. On the other hand, molecular fluorine is an extremely reactive chemical and extensive safety measures must be taken for its safe use. The danger occurs when the NF3 is heated, either through chemical reaction or adiabatic compression, to a temperature where free fluorine is generated. The potential problem exists since the free fluorine can act as an initiator if it contacts any incompatible materials, and the NF3 could sustain a fire or an explosion.

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Mixed Gas Composition for CVD Reactor Cleaning

Problem Definition

A blend of 2 to 12 % F2 in NF3 has been proposed for in situ CVD reactor cleans. This blend had been shown to give improved “clean” rates downstream from the primary discharge in a plasma clean step. Unfortunately this mixture represents a much more difficult gas handling challenge than either of the two individual constituents. NF3, a strong oxidizer, can be used in a safe, routine manner if the proper safety precautions are followed. On the other hand, molecular fluorine is an extremely reactive chemical and extensive safety measures must be taken for its safe use. The danger occurs when the NF3 is heated, either through chemical reaction or adiabatic compression, to a temperature where free fluorine is generated. The potential problem exists since the free fluorine can act as an initiator if it contacts any incompatible materials, and the NF3 could sustain a fire or an explosion.

Process Description

A much safer method of delivering fluorine is as a dilute mixture in an ‘inert’ gas (e.g., He, N2, Ne, Ar, Kr, Xe). It is well known that 100% NF3 plasmas are not stable under many conditions, and even under stable conditions give relatively low etch rates. Thus, a pure mix of F2 with NF3 will be less effective as a cleaning gas than a mix of F2, NF3, and an inert gas. The F2 can be delivered in an inert diluent and mixed with the NF3 in the plasma reactor, thus reducing the handling challenges related t...