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In Situ Infrared Absorption Spectroscopy for Endpoint Detection

IP.com Disclosure Number: IPCOM000121094D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 82K

Publishing Venue

IBM

Related People

O'Neill, JA: AUTHOR [+2]

Abstract

Disclosed is a method which uses infrared absorption spectroscopy to determine the endpoint of an etching reaction. This is a general technique suitable for implementation in situ in a discharge as well as in high temperature reactive environments. One embodiment of the method uses a Fourier transform infrared spectrometer (FTIR) to monitor the concentration of etch products in a flowing reactive ion etching system. The presence of a particular molecular species in the plasma is indicated by absorption of the infrared probe beam at specific spectral wavelengths. For example, in the etching of a SiO2 film on aluminum in a CF4/O2 plasma, the SiF4 etch product is easily detected by its characteristic absorption feature at 1028 cm-1 .

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In Situ Infrared Absorption Spectroscopy for Endpoint Detection

      Disclosed is a method which uses infrared absorption
spectroscopy to determine the endpoint of an etching reaction.  This
is a general technique suitable for implementation in situ in a
discharge as well as in high temperature reactive environments.  One
embodiment of the method uses a Fourier transform infrared
spectrometer (FTIR) to monitor the concentration of etch products in
a flowing reactive ion etching system.  The presence of a particular
molecular species in the plasma is indicated by absorption of the
infrared probe beam at specific spectral wavelengths. For example, in
the etching of a SiO2 film on aluminum in a CF4/O2 plasma, the SiF4
etch product is easily detected by its characteristic absorption
feature at 1028 cm-1 .  By monitoring the time-dependent intensity of
this absorption feature throughout the course of the etching
reaction, the progress of the etch process can be followed.  The
endpoint of the etching reaction is detected when the SiF4 etch
product is no longer detected in the plasma.  While this example
illustrates the etching of SiO2 on aluminum, this infrared probe
method is a general technique applicable to other systems as well.
For example, the progress of a photoresist etching process in an O2
plasma can be followed by monitoring the CO or CO2 etch product in
the plasma.

      The figure illustrates the apparatus used to observe the
etching endpoint in a parallel plate reactive ion etching reactor 1.
The probe beam 2 from an infrared spect...