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High Etch Rate Ratio for Silicon Dioxide Relative to Silicon Nitride

IP.com Disclosure Number: IPCOM000109524D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Burke, PA: AUTHOR [+2]

Abstract

By using a polymer forming etch gas, e.g., CHF3/Ar, in reactive ion etching (RIE) and eliminating oxygen sources, e.g., photoresist, during etching of oxide and nitride film structures, better than ten to one etch rate ratio (ERR) of oxide to nitride is achieved.

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High Etch Rate Ratio for Silicon Dioxide Relative to Silicon Nitride

       By using a polymer forming etch gas, e.g., CHF3/Ar, in
reactive ion etching (RIE) and eliminating oxygen sources, e.g.,
photoresist, during etching of oxide and nitride film structures,
better than ten to one etch rate ratio (ERR) of oxide to nitride is
achieved.

      Referring to Fig. 1, to etch a pattern through oxide layer 2
and dependably stop on thin nitride layer 4 before exposing substrate
6, masking layer 8 is deposited before creating a pattern in
photoresist 10.  Masking layer 8 may be nitride or any material,
e.g., a metal, which does not contribute oxygen to the RIE
environment, especially at the time of reaching the top surface of
etch stop, nitride 4.

      The etching process to achieve the structure shown in Fig. 2
follows.  First, etch through masking layer 8 using photoresist layer
10 as the mask.  Next, photoresist 10 is stripped by oxygen ashing,
for instance.  Then, using layer 8 as the mask and a polymer forming
etch gas, e.g., CF4/Ar, oxide layer 2 is etched through to nitride
layer 4.  Polymer formation is retarded on oxide surfaces but not on
nitride surfaces.  Thus, nitride etching is inhibited while oxide
etch rate remains high.  The enhanced ERR of oxide to nitride at the
time of break through to etch stop layer 4 is especially valuable
when oxide layer 8 varies in thickness.

      Masking layer 8 may then be removed and, if layer 8 is nitride,...