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Photochemically Enhanced Deposition of Silicon Nitride

IP.com Disclosure Number: IPCOM000119875D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 76K

Publishing Venue

IBM

Related People

Jasinski, JM: AUTHOR [+2]

Abstract

The deposition of silicon nitride by conventional techniques, such as the low pressure co-pyrolysis of silane (SiH4) and ammonia (NH2) results in high quality, stoichiometric films of silicon nitride. The temperatures required for this process center on 800@C, and thus are higher than desirable for a material preferred for use as a back end of the line passivation coating. In an effort to lower the temperatures required for nitride deposition, several alternative deposition schemes have been attempted, most notably those involving the use of a plasma to dissociate the source gases into reactive deposition precursors.

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Photochemically Enhanced Deposition of Silicon Nitride

      The deposition of silicon nitride by conventional
techniques, such as the low pressure co-pyrolysis of silane (SiH4)
and ammonia (NH2) results in high quality, stoichiometric films of
silicon nitride.  The temperatures required for this process center
on 800@C, and thus are higher than desirable for a material preferred
for use as a back end of the line passivation coating.  In an effort
to lower the temperatures required for nitride deposition, several
alternative deposition schemes have been attempted, most notably
those involving the use of a plasma to dissociate the source gases
into reactive deposition precursors.  Since this type of process
involves the homogeneous (gas phase) generation of these species,
rather than the heterogeneous chemistry commonly associated with a
thermal process, the actual mechanism of film growth is altered.  It
has been generally observed that films deposited by these alternate
excitation schemes are inferior in dielectric properties to those
prepared thermally, but they have the advantage in that they are
deposited at far lower temperatures (200@C-700@C).

      The elevated temperatures required to produce silicon nitride
(800@C) at growth rates comparable to those for intrinsic silicon
from pure silane (625@C) may be related to the strong adsorption of
ammonia molecules on the growth interface, thus effectively poisoning
the growth surface with respect to further silane adsorption.
Ammonia has a strong absorption band at 200 nanometers, which should
allow the selective photolysis of the adsorbed molecules, thus
creating free adsorption sites which allow the growth process to
proceed.  This wi...