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Use of Aluminum Oxide for Increased Selectivity During Chemical Vapor Deposition of Selective Tungsten

IP.com Disclosure Number: IPCOM000100412D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Ahn, K: AUTHOR [+3]

Abstract

Low-pressure chemical vapor deposition (LPCVD) of tungsten (W) is frequently performed in systems where the substrates rest on a fused quartz window and are heated from the backside with lamps. Tungsten is deposited wherever silicon or metal is exposed on the substrate, but it is not deposited on the quartz window, or wherever there is SiO2 on the substrate. One drawback of this technique is the occasional loss of selectivity which results in W growing on SiO2 and on the quartz window. The mechanism of the selectivity loss is not yet fully understood (1,2), but once any W has grown on the quartz window, it will continue to do so until the quartz window is cleaned by removing all of the W from it.

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Use of Aluminum Oxide for Increased Selectivity During Chemical Vapor Deposition of Selective Tungsten

       Low-pressure chemical vapor deposition (LPCVD) of
tungsten (W) is frequently performed in systems where the substrates
rest on a fused quartz window and are heated from the backside with
lamps.  Tungsten is deposited wherever silicon or metal is exposed on
the substrate, but it is not deposited on the quartz window, or
wherever there is SiO2 on the substrate.  One drawback of this
technique is the occasional loss of selectivity which results in W
growing on SiO2 and on the quartz window.  The mechanism of the
selectivity loss is not yet fully understood (1,2), but once any W
has grown on the quartz window, it will continue to do so until the
quartz window is cleaned by removing all of the W from it.  The
presence of tungsten on the quartz window causes poor process
control, thereby resulting in the need for a good cleaning procedure.
 Typical ways of cleaning the window are mechanical methods
(scrubbing) or chemical methods, usually involving hazardous gasses,
such as nitrogen trifluoride.  Both procedures result in significant
amounts of system downtime.

      Disclosed here is a process to reduce these significant amounts
of downtime by coating the top of the wafer and the quartz window
with aluminum oxide (A12O3).  It has been reported that during
selective tungsten growth, there is no growth on aluminum oxide (3).
Since sapphire is transparent to IR radiation (4), th...