Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
2000-01-19
2001-12-11
Mills, Gregory (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C118S733000
Reexamination Certificate
active
06328847
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to plasma processing equipment and, more particularly, to downstream plasma reactor systems usable in semiconductor processing.
2. Description of the Related Art
The information described below is not admitted to be prior art by virtue of its inclusion in this Background section.
Plasma processing is commonly used in semiconductor fabrication. One use for plasma processing is in the removal of layers formed on a substrate, typically by etching some or all of a particular layer. Plasma processing is often performed in single chamber reactor systems in which plasma is generated exclusively in the chamber in which processing is carried out. Alternatively, downstream plasma reactor systems may be used that first convert gases into plasma in a plasma tube and then transport the plasma-generated reactive species downstream into the reaction chamber. These reactor systems can be used to avoid the radiation damage and resist hardening common in single chamber plasma reactor systems. And like single chamber plasma reactor systems, downstream plasma reactor systems can be used to create reactive species capable of etching layers of silicon dioxide, silicon nitride, aluminum, and various other materials commonly used in semiconductor fabrication.
A common application for downstream plasma reactor systems is resist stripping, i.e., the removal of patterned photoresist after completion of an etch step. Resist stripping usually is carried out in an ashing process in which the resist is oxidized to a gaseous form and removed from the reaction chamber. Those downstream plasma reactor systems that are specifically configured for resist stripping are often labeled downstream plasma strippers.
FIG. 1
presents a schematic view of an exemplary downstream plasma reactor system
100
, the GaSonics L3500, which is commercially available from GaSonics International (San Jose, Calif.). Because it is primarily configured to remove resist, downstream plasma reactor system
100
may be properly labeled a downstream plasma stripper. Reactor system
100
includes a plasma tube
104
. Plasma tube
104
is made up of an intake portion
106
, a central portion
108
, and a discharge portion
110
. Gas source
102
is configured to be in gaseous communication with (i.e., may be operably connected such that gases can flow therebetween) intake portion
106
. Plasma tube
104
is coupled to inlet conduit
112
. Inlet conduit
112
is connected to reaction chamber
114
. Reactor system
100
also includes plasma generating apparatus
111
, which is positioned adjacent to plasma tube central portion
108
and includes a power supply and a microwave generator. Outlet conduit
116
is connected to reaction chamber
114
and is configured to be in selective gaseous communication with vacuum pump
118
.
During operation of downstream plasma reactor system
100
, vacuum pump
118
may be used to evacuate gases from reaction chamber
114
and all conduits in gaseous communication with reaction chamber
114
, including inlet conduit
112
and plasma tube
104
. Gases may be introduced into plasma tube
104
from gas source
102
via intake portion
106
. The desired amounts and proportions of gases supplied by gas source
102
may be regulated using one or more mass flow controllers. These gases are typically selected such that the reactive species generated upon plasma formation are appropriate for the particular process being performed. As the gases enter central portion
108
, microwaves created by plasma generating apparatus
111
convert at least a portion of the entering gases into plasma (i.e., creating a partially ionized plasma). The plasma generated in central portion
108
subsequently passes into discharge portion
110
. From discharge portion
110
, the plasma is conveyed into inlet conduit
112
. The plasma is then transported through inlet conduit
112
into reaction chamber
114
to be used in processing.
FIG. 2
presents an expanded cross-sectional view of section A of reactor system
100
. Section A includes parts of discharge portion
110
of plasma tube
104
and coupling portion
126
of inlet conduit
112
. As shown in
FIG. 2
, discharge portion
110
may be subdivided into an initial section
120
, an expanded section
122
, and a tube extension
124
. As shown in
FIG. 2
, tube extension
124
is a tube positioned partially within and extending beyond initial section
120
and expanded section
122
. Initial section
120
, expanded section
122
, and tube extension
124
are composed of fused quartz, and tube extension
124
is fixably attached (i.e., coupled such that it is not capable of significant independent movement) to initial section
120
at glass weld
123
. Discharge opening
125
is defined at the end of tube extension
124
. Sealing o-ring groove
128
is defined within expanded section
122
and is configured to hold sealing o-ring
130
. Sealing o-ring
130
is composed of an elastomeric material. Being composed an elastomeric material, sealing o-ring
130
is able to conform to the surfaces of plasma tube
104
and inlet conduit
112
to achieve good sealing action. Sealing o-ring
130
should be configured to make a seal between plasma tube
104
and inlet conduit
112
sufficient to maintain the level of vacuum desired within the plasma tube and inlet conduit. Coupling section
126
includes socket
131
and throat
133
. Socket
131
is configured to fit snugly around expanded section
122
when sealing o-ring
130
is in place.
Sealing o-ring
130
should not only provide a good seal between plasma tube
104
and inlet conduit
112
, but should also be able to maintain such a seal over numerous operation cycles carried out over a sizable time period. One factor that determines the life of a seal over repeated operational cycles is whether the seal posses sufficient resiliency. Sufficient resiliency in sealing o-ring
130
is important because when reactor system
100
is under vacuum during an operation cycle, coupling portion
126
exerts substantial lateral (i.e. radial) force on the sealing o-ring, compressing it. Then when then the cycle is completed, vacuum is released and the lateral force exerted by coupling section
126
subsides. A sufficiently resilient sealing o-ring
130
is able to be significantly compressed during a vacuum cycle and then return to its original shape after completion of the cycle. As such, a sufficiently resilient sealing o-ring may maintain high seal quality over numerous operation cycles.
With time, repeated compression and expansion can cause even the most resilient of o-rings to fail; however, it is desired that the mean time between failures of a sealing o-ring be extended as long as is reasonably possible. For example, replacing sealing o-ring
130
requires the purchase of a new o-ring and necessitates the expenditure of limited employee time. Over time, the reduction in the throughput of reactor system
100
during these replacement periods can result in a substantial loss of production value. It is thus beneficial to reduce the frequency with which replacement of sealing o-ring
130
is required (i.e., to extend the mean time between failure for the o-ring).
Unfortunately, the operating conditions of reactor system
100
can greatly reduce the amount of time between failures of sealing o-ring
130
. One explanation for this outcome is the presence of numerous reactive species (e.g., ions and radicals) in the plasma exiting the plasma tube. Most of these reactive species will pass directly into the inlet conduit, but some end up in contact with sealing o-ring
130
. While these plasma-generated reactive species do not substantially erode the fused quartz of which plasma tube
104
is constructed, other elements of the plasma system, such as sealing o-ring
130
, arc often constructed of materials more susceptible to such erosion. Furthermore, resist stripping often incorporates hydrogen- and oxygen-containing plasmas that have a particularly pronounced ability to
Advanced Micro Devices , Inc.
Alejandro Luz
Conley & Rose & Tayon P.C.
Daffer Kevin L.
Mills Gregory
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