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Intermediate Transistor Structure Using PSG and SiO2

IP.com Disclosure Number: IPCOM000121888D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 1 page(s) / 50K

Publishing Venue

IBM

Related People

Oehlrein, GS: AUTHOR [+2]

Abstract

Disclosed is an intermediate transistor structure using PSG for the main insulator and SiO2 in place of Al2O3 as an etch stop layer. This approach uses a reactive ion etching process to selectively etch PSG over the SiO2 etch stop layer.

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Intermediate Transistor Structure Using PSG and SiO2

      Disclosed is an intermediate transistor structure using
PSG for the main insulator and SiO2 in place of Al2O3 as an etch stop
layer.  This approach uses a reactive ion etching process to
selectively etch PSG over the SiO2 etch stop layer.

      In the final stages of transistor fabrication it is necessary
to form vias through an insulator, e.g., sputtered quartz.  Because
of non-uniform etch depths of vias across the structure, an Al2O3
etch stop layer is conventionally deposited by sputtering or chemical
vapor deposition. Reactive ion etching of quartz stops on the Al2O3
layer, but this layer then has to be removed to make an electrical
contact to the underlying film.  Al2O3 etches solely by physical
sputtering or aggressive wet etchants and both removal processes are
undesirable.

      A reactive ion etching process has been disclosed [*] which
allows selective etching of PECVD phosphosilicate films (PSG) over
thermal or sputtered SiO2 without phosphorus.  The process relies on
the large difference observed in the etch characteristics of the two
films in mixtures of CF4 and H2 .  The process is conducted in a
diode reactor with a TEFLON*-covered cathode using 200 W of RF power,
a pressure of 25 mTorr and a total gas flow of 40 sccm.  A mixture
of CF4 and H2 is used and the proportion of hydrogen is varied
between 50% and 100% of the total gas flow.  Since the process
results in the deposition...