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Aggressive Endpoint Overetch with Maximum Selectivity to Underlayer

IP.com Disclosure Number: IPCOM000110241D
Original Publication Date: 1992-Nov-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 4 page(s) / 112K

Publishing Venue

IBM

Related People

Ng, HY: AUTHOR

Abstract

A technique is described whereby an aggressive endpoint overetch can reach maximum selectivity to the underlayer in etching dielectrics to silicon.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Aggressive Endpoint Overetch with Maximum Selectivity to Underlayer

       A technique is described whereby an aggressive endpoint
overetch can reach maximum selectivity to the underlayer in etching
dielectrics to silicon.

      Etching of dielectrics, such as SiO2 and Si3N4, by means of
fluorocarbon chemistry (1-3), such as CF4/H2, CHF3/CO2 or O2, and
CHF3/ C2F6, etc., with high selectivity to silicon is obtained by
controlling the polymer deposition rate.  Although polymerization
provides selectivity of etching dielectrics to silicon, excessive
polymer formation will prohibit the etching of the dielectrics as
well as the silicon.  Selectivity to the underlayer, silicon, of
etching dielectrics can be obtained by balancing between the etch
rate of the dielectrics and the polymer deposition rate.  This thin
fluorohydrocarbon polymer film normally can be removed by means of
oxygen plasma.

      The concept described herein provides an aggressive endpoint
overetch technique so as to have maximum selectivity of etching
dielectrics to the silicon with minimum polymer deposition.  This is
because selectivity to the underlayer is only necessary at the
endpoint to compensate for non-uniform etching of the material at the
interface.

      The method incorporates methyl fluoride (CH3F) in the mixture
of CHF3/CO2 to deflect the fluorine concentrate and to increase the
amount of unsaturated fluorocarbon as well as the polymer deposition,
as shown in Fig. 1.  Oxide has the capability to etch continuously
for 10 to 15 minutes at the average etch rate of 300 ang./in., where
the CH3F flow volume percent is below 10 percent.  The silicon etch
rate decreases as the flow volume percent of CH3F increases.  The
following table lists the amount of silicon etch at various
compositions:

      % CHF3F in CHF3/CO2           TOTAL          THE AMOUNT OF
        MIXTURE                ETCH TIME        SILICON ETCH
        ...