Etch Process Mixing Guidelines from AMAT

Jim McVittie mcvittie at snf.stanford.edu
Fri Jul 11 09:19:42 PDT 2003


PQuest Users,

Since we have had lots of questions about mixing etch processes on the
PQuest, I thought it would interested for you to see what Applied
Materials recommends for their dielectric chambers.  Jim


MxP+ Process Mixing Guidelines

The MxP+ chamber has been designed to confine polymer deposition to the
chamber liners.  Because the chamber liner polymer can be removed and
deposited during the etch process, there are secondary process effects
that need to be considered when the MxP+ chamber is used in a mixed
process mode.  Below are general process mixing guidelines for the
various dielectric etch processes.

Pad and Via vs. Front End Processes
Due to metal contamination concerns from sputtered metals (Al, Pt, etc.)
and etched TiN or TaN, it is recommended that processes such as via,
pad, oxide and nitride hardmask open for metal (Al, Pt, etc.) processes
typically stopping on TiN or TaN liners be kept separate from front end
processes.  An additional reason to separate these processes is that the
polymer produced is different from the insulating polymer produced from
contact, spacer, etc., processes and may affect the processes
differently.  All CoSix contact etch processes should be in dedicated
chambers.

Polymerizing vs. Lean Processes
The concern from mixing polymerizing and lean processes is that lean
processes will tend to etch the chamber liner polymer more so than
polymerizing processes.  The excessive etching of the chamber liner
polymer can become a particle source.  Another concern is that the
Fluorine containing species are released from the chamber liner polymer
and will contribute to the process, so maintaining the chamber liner
polymer becomes critical especially with low etch rate or F-starved
processes.  Mixing of these processes is possible through management of
the process loading, however, chamber seasonings may be required.

High O2 Processes vs. Low O2 Processes
Oxygen containing processes can be divided into two categories of low
O2/CHxFy ratio (polymer depositing ) processes and high O2/CHxFy ratio
(non-polymer depositing) processes.  The same concerns would apply when
mixing polymerizing vs. lean processes.  In the case of mixing nitride
etch processes such as high O2/CH3F processes (i.e. nitride spacer )
with low O2/CH3F processes (ie. nitride locos) can create problems.  The
polymer produced from CH3F processes does not adhere as well as polymer
produced from non-CH3F containing processes.  Processes relatively high
in O2 will remove the powdery, poorly adhering polymer and can result in
particle and process drift problems.

Planarization Processes
Planarization processes such as SOG and photoresist etch back are
usually kept separate from other processes due to their sensitivity to
chamber conditions and low MTBC when mixed with other processes due to
particle problems.  For processes that are more polymerizing due to
selectivity requirements, such as SOG etch back processes with SOG:TEOS
selectivity <1, these processes can be mixed with other processes.

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