Electric lamp and discharge devices: systems – Discharge device load with fluent material supply to the... – Plasma generating
Reexamination Certificate
1999-03-23
2001-03-20
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Discharge device load with fluent material supply to the...
Plasma generating
C315S111510, C315S344000, C118S7230IR, C118S7230AN
Reexamination Certificate
active
06204604
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to igniting and sustaining plasmas, and more particularly to methods and apparatus for controlling electrostatic coupling to plasmas.
BACKGROUND OF THE INVENTION
Integrated circuits are commonly fabricated on and within a surface region of a semiconductor substrate, such as a wafer of silicon. During such fabrication, various layers are produced within the substrate or deposited thereon. Some of these layers are then sized and dimensioned to form desired geometric patterns by means of various etching techniques. Such etching techniques include “wet” etching techniques, which typically use one or more chemical reagents brought into direct contact with the substrate, or “dry” etching techniques such as plasma etching.
Numerous plasma-based etching techniques are known in the art, including what is commonly called the plasma etching mode, as well as reactive ion etching and reactive ion beam etching. In any of the wide variety of plasma etching techniques, a plasma is created from gas introduced into a reaction chamber. One or more electrodes (commonly driven by an RF generator) generate the plasma by disassociation of the gas molecules into various ions, free radicals, and electrons. The plasma then reacts with material being etched from the semiconductor wafer.
FIG. 1
depicts the major components of a prior art plasma etching system
10
, such as the Lam 9100, manufactured by Lam Research, Inc. The etching system
10
includes a reaction chamber
12
having a chamber wall
14
, which is typically grounded. An electrode, such as a planar coil electrode
16
, is positioned adjacent to a dielectric structure
18
separating the electrode
16
from the interior of the reaction chamber
12
. Source gases, from which the plasma is generated, are provided by a gas supply
20
. The gas supply
20
is coupled with the reaction chamber
12
by a gas control panel
22
, which selects and controls the flow of source gases into the chamber. Volatile reaction products, unreacted plasma species, and other gases are removed from the reaction chamber
12
by a gas removal mechanism, such as a vacuum pump
24
and throttle valve
26
.
The dielectric structure
18
depicted in
FIG. 1
may serve multiple purposes and have correspondingly multiple structural features, as is well known in the art. For example, the dielectric structure
18
may include features for introducing the source gases into the reaction chamber
12
, as well as those structures associated with physically separating the electrode
16
from the interior of the chamber.
Electrical power such as a high voltage signal is applied to the electrode
16
to ignite and sustain a plasma within the reaction chamber
12
. The high voltage signal is provided by a power generator, such as an RF generator
28
. The RF generator
28
is coupled with one end of the planar coil electrode
16
by a matching network
30
, which functions primarily to match impedances, as is well known in the art. The other end of the planar coil electrode
16
is coupled to ground potential by a terminal capacitor
32
or C
T
. The terminal capacitor C
T
is oftentimes included within the matching network
30
, but is depicted separately in
FIG. 1
for illustrative purposes.
Ignition of a plasma within the reaction chamber
12
occurs primarily by electrostatic coupling of the electrode
16
with the source gases, due to the large magnitude voltage applied to the electrode and the resulting electric fields produced within the reaction chamber. Once ignited, the plasma is sustained by electromagnetic induction effects associated with a time-varying magnetic fields caused by the alternating currents applied to the electrode
16
. A semiconductor wafer
34
is positioned within the reaction chamber
12
and is supported by a wafer platform or chuck
36
. The chuck
36
is typically electrically biased to provide ion energies impacting the wafer
34
that are approximately independent of the RF voltage applied to the electrode
16
.
Typically, the voltage varies as a function of position along the coil electrode
16
, with relatively higher amplitude voltages occurring at certain positions along the electrode
16
, and relatively lower amplitude voltages occurring at other positions along the electrode. A large electric field strength is required to ignite plasmas within he reaction chamber
12
. To create such a field, it is desirable to provide the relatively higher amplitude voltages at locations along the electrode
16
which are close to the grounded chamber wall
14
.
Referring to
FIG. 2
, a graphical representation depicts the relative amplitudes of the voltages at locations along the electrode
16
, with location A representing a position near the center of the coil electrode and location B representing a location near an outer end of the electrode (see FIG.
1
). For the coil electrode
16
used in the Lam 9100, selecting a relatively small capacitance value for the terminal capacitor C
T
produces the higher amplitude voltages at location B, whereas selecting a relatively large capacitance value produces the higher amplitude voltages at location A. Thus, in this example, selecting a relatively small capacitance value for the terminal capacitor C
T
enhances efficient ignition of plasmas within the reaction chamber
12
. Of course, voltage amplitudes produced by electrodes of different configurations and/or effective electrical lengths may vary with C
T
other than described for the electrode
16
.
As is known to those skilled in the art, producing the relatively higher amplitude voltages at positions away from the center of the electrode
16
results in improved etching uniformity, especially improved uniformity of etching depth and profile. However, locating the relatively higher amplitude voltages near the grounded chamber wall
14
also can result in increased sputtering effects on the dielectric structure
18
. The electric field between the chamber wall
14
and the dielectric structure
18
causes ion impact on the dielectric structure. This may sputter polymer or other deposits from the dielectric structure, or sputter the dielectric structure itself, and possibly cause contamination of the semiconductor wafer
34
. Thus, an unfortunate tradeoff exists in which conditions conducive to plasma ignition and etching uniformity also increase potential contamination effects.
A conventional PECVD system is similarly constructed to the conventional plasma etching system shown in
FIG. 1. A
conventional PECVD system typically includes the reaction chamber
12
, the gas removal system, such as the vacuum pump
24
and the throttle valve
26
, the gas supply
20
and the gas control panel
22
, and the RE generator
28
. The RF generator is coupled to one end of the planar coil electrode
16
by the matching network
30
. The other end of the planar coil electrode
16
is coupled to ground by the terminal capacitor
32
. However, an important difference between conventional PECVD systems and plasma etching systems is that the gas supply
20
contains the reactants for depositing a material rather than for etching a material.
As is generally known to those skilled in the art, the properties of a material deposited by a PECVD system may be altered by adjusting the strength of electrostatic coupling between the electrode
16
and the source gases within the reaction chamber
12
. For example, after effective ignition of the plasma, the strength of electrostatic coupling may be adjusted so that ionization of the source gas near a gas inlet is reduced. Reducing, or for that matter, increasing, the strength of the electrostatic coupling near the gas inlet of the source gases will alter the deposition rate, as well as other properties of the deposited material, such as film uniformity, stoichiometry, stress, and conformality.
As mentioned previously, electrostatic coupling between the electrode
16
and source gases may be adjusted by varying the voltage amplitudes at various locations along the electrode
16
. Th
Dorsey & Whitney LLP
Micro)n Technology, Inc.
Philogene Haissa
LandOfFree
Method and apparatus for controlling electrostatic coupling... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for controlling electrostatic coupling..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for controlling electrostatic coupling... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2458008