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Removal of Byproducts from CVD Copper Effluent Streams

IP.com Disclosure Number: IPCOM000019380D
Publication Date: 2003-Sep-12
Document File: 5 page(s) / 38K

Publishing Venue

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Abstract

Copper deposition has become one of the most important and most rapidly growing areas in integrated circuit manufacturing. Copper metallization can be accomplished by several means, one of the most popular is the use of chemical vapor deposition (CVD). However, as in most processes, 100% utilization of the chemical is not possible, and by-products and unreacted precursor materials exit the process chamber. This is not only unattractive from the perspective of low utilization of precursor but is also problematic since copper is not generally permitted to escape into the environment. Simple burn box treatment of the effluent can result in precursor degradation into fluorine containing potentially corrosive compounds that can also be environmentally hazardous. To avoid these problems a simple, novel and non-destructive method for capturing copper CVD effluent has been developed and is described here. It avoids pollution from the release of copper and fluorocarbon containing species and allows for the recycle of captured materials.

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Removal of Byproducts from CVD Copper Effluent Streams

         Copper deposition has become one of the most important and most rapidly growing areas in integrated circuit manufacturing. Copper metallization can be accomplished by several means, one of the most popular is the use of chemical vapor deposition (CVD). However, as in most processes, 100% utilization of the chemical is not possible, and by-products and unreacted precursor materials exit the process chamber. This is not only unattractive from the perspective of low utilization of precursor but is also problematic since copper is not generally permitted to escape into the environment. Simple burn box treatment of the effluent can result in precursor degradation into fluorine containing potentially corrosive compounds that can also be environmentally hazardous. To avoid these problems a simple, novel and non-destructive method for capturing copper CVD effluent has been developed and is described here. It avoids pollution from the release of copper and fluorocarbon containing species and allows for the recycle of captured materials.

Chemistry of Copper CVD

         There are a number of compounds that can be used for the CVD of copper metal films. These generally fall into a class of compounds that combine copper atoms with a pair of ligands to produce a volatile liquid compound whose vapors can be easily delivered to a process chamber. The molecule thus described must be easily decomposed to free the copper atoms for the formation of the copper film. An example of these precursors is the compound “CupraSelectTM” (Cu(hfac)(TMVS), chemical formula: C10H13CuF6O2Si , which combines copper with TMVS and ‘hfac’ ligands. The deposition takes place by a process called disproportionation, wherein an electron is transferred from one molecule of precursor to another, causing the formation of a copper film, along with Cu+2(hfac)2, and free TMVS by-products. The maximum theoretical efficiency of this process is 50%, meaning that only half the copper going into the process chamber can be consumed by growing a copper film, with the other half of the copper atoms being exhausted from the chamber as Cu+2(hfac)2 by-product. In practice, this theoretical efficiency cannot be met, so some unreacted precursor escapes the chamber, as well as the process by-products of Cu+2(hfac)2 and TMVS. Thus, in this example, it is the unreacted CupraSelectand the Cu+2(hfac)2 and TMVS by-products that requires abatement processes.

Advantages and Benefits to Copper CVD Abatement

         While copper CVD produces far less effluent than processes such as electroplating, there is still a reasonable quantity of potential waste generated during the process. Typically, waste is in the range of 0.5 to 5 grams per wafer processed. In a typical wafer fabrication environment this can mean as much as 25 to 250 kilograms of by-products can be generated per month. This is material that cannot be released into the environment and if abated by a simpl...