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Collimated Sputtering for High Aspect Ratio Trench Via Fill with a Liner

IP.com Disclosure Number: IPCOM000110127D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 4 page(s) / 113K

Publishing Venue

IBM

Related People

Cuomo, JJ: AUTHOR [+4]

Abstract

The deposition of liner seed layers in the contacts or trenches are essential for subsequent growth of CVD metals to promote adhesion. The liner can further act as a barrier to prevent diffusion of low resistivity metal. The current art involves deposition of a liner by ordinary sputtering. The replacement for sputtering of liners is deposition by CVD which is not yet proven. A technique of collimated sputtering to deposit Al-Cu or Cu into trenches with an aspect ratio of 2 using a lift-off technique has been described in [*]. We have invented a process to deposit liner films conformally on the side wall as well as on the bottom of the hole or trench to be used as diffusion barriers and adhesion layers in high aspect ratio vias or lines.

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Collimated Sputtering for High Aspect Ratio Trench Via Fill with a Liner

       The deposition of liner seed layers in the contacts or
trenches are essential for subsequent growth of CVD metals to promote
adhesion.  The liner can further act as a barrier to prevent
diffusion of low resistivity metal.  The current art involves
deposition of a liner by ordinary sputtering.  The replacement for
sputtering of liners is deposition by CVD which is not yet proven.  A
technique of collimated sputtering to deposit Al-Cu or Cu into
trenches with an aspect ratio of 2 using a lift-off technique has
been described in [*].  We have invented a process to deposit liner
films conformally on the side wall as well as on the bottom of the
hole or trench to be used as diffusion barriers and adhesion layers
in high aspect ratio vias or lines.  The technique allows the
deposition of metals such as Ti, W, Ta and their nitrides as well as
other relevant metals into very high aspect ratio contacts/trenches
using directional sputtering.  Normally the gas scattering effects
are dominant in the normal range of sputtering operation which
results in poor step coverages.  It is possible to deposit a liner
composed of a refractory metal at low pressures.  For a diffusion
barrier technology for a fast diffusing metal like Cu, a two-step
collimation process is proposed to fill high aspect ratio sub-half
micron vias or lines.  The process can be easily applied for
inorganic/organic dielectrics.

      The process for forming a liner in the via can be described as
follows: First a thin seed layer is deposited by higher aspect ratio
collimator followed by lower aspect ratio collimator at pressures
below 4 mT.  The higher powers (8-12 KW) are essential to improve the
growth rate.  The experiments are carried out using Ti a seed layer
and W or Ta on top.  Using the hollow cathode electron source near
the magnetron cathode which allows the operation of the cathode at
full power in the low pressure range (10-4 Torr), the liners are
deposited.  To prevent the cosine distribution of the atoms emitted
from the sputtered target collimated tubes with various aspect ratios
were utilized.  A detailed s...