Electric lamp and discharge devices: systems – Discharge device load with fluent material supply to the... – Plasma generating
Reexamination Certificate
2002-02-14
2004-06-01
Lee, Wilson (Department: 2821)
Electric lamp and discharge devices: systems
Discharge device load with fluent material supply to the...
Plasma generating
C118S7230ER, C118S7230IR, C156S345180, C315S111910
Reexamination Certificate
active
06744212
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention is related to semiconductor fabrication. More particularly, the invention is related to plasma processing during semiconductor fabrication.
2. Description of Related Art
In the fabrication of semiconductor based devices (e.g. integrated circuits or flat panel displays) layers of material may alternately be deposited onto and etched from a workpiece surface (e.g., the semiconductor wafer or the glass panel). As is well known in the art, the etching of the deposited layer(s) may be accomplished by a variety of techniques, including plasma-enhanced etching. In plasma-enhanced etching, the actual etching of the workpiece takes place inside a plasma processing chamber. During the etching process, a plasma is formed from a suitable etchant source gas to etch areas of the workpiece that are unprotected by the mask, leaving behind the desired pattern.
There are two types of plasmas that are employed in plasma-enhanced etching, namely, confined plasmas and unconfined plasmas. Unconfined plasmas touch the plasma processing chamber walls and may contaminate the workpiece by re-depositing atoms from the chamber walls on to the workpiece. Typically, the plasma processing chamber walls are made of materials that are incompatible to the workpiece. With confined plasma, there is little or no contamination since the plasma is stopped by some means from reaching the chamber walls. Thus, confined plasmas provide a level of cleanliness that is not provided by well-known unconfined plasmas.
Generating confined plasma may prove, however, difficult since it has a high electric potential with respect to the chamber walls. This high potential in connection with a given geometry of the reactor and gas pressure outside the confinement means can lead to electric breakdown of the gas and the ignition of plasma outside the confined region. Furthermore, large RF return currents on the inner surface of the chamber walls may inductively couple RF energy into the gas outside the confinement means. This may also lead to electric breakdown of the gas and, therefore, will enable the plasma to spread to the chamber walls. This undesirable state will be referred to as unconfinement.
Typically, plasma can be prevented from reaching the chamber walls by establishing a variety of repulsive fields, either electric or magnetic in nature. By way of example, the plasma is confined by a plurality of confinement rings resident within the chamber walls and by means of draining charge out of the plasma just before it can reach the inner limits of the confinement rings. Since the confinement rings are made from an insulating material they will charge to a potential comparable to that of the plasma. Consequently, a repulsive electric field will emanate from the leading edge of each confinement ring that will keep plasma from protruding any further out toward the chamber walls.
Among the different types of plasma etching systems, those utilizing confinement rings have proven to be highly suitable and effective for the production of semiconductors. An example of such a system may be found in commonly assigned U.S. Pat. No. 5,534,751 and U.S. Pat. No. 6,019,060 which are hereby incorporated by reference.
The Lenz et al. U.S. Pat. No. 5,534,751 disclosure describes a plasma etching apparatus utilizing plasma confinement. The plasma etching apparatus includes confinement rings that comprise quartz rings that are positioned to surround an interaction space between two electrodes of the apparatus where a plasma is formed during operation of the apparatus. The dimensions of the slots are chosen to insure that charged particles of spent gases in the plasma exiting the interaction space are neutralized by wall collisions as they exit the slots. Two voltage sources of different frequencies are used to apply voltages to the electrodes in a fashion that isolates each source from the other. The other Lenz U.S. Pat. No. 6,019,060 disclosure describes the use of confinement rings in which the confinement rings are raised and lowered to facilitate workpiece transport.
An illustrative example of a plasma processing chamber having confinement rings is shown in FIG.
1
. The Figure shows a cross-sectional view of the plasma processing chamber
100
having confinement rings
102
a
and
102
b
. Although only two confinement rings are shown, it should be understood that any number of confinement rings may be provided. Within plasma processing chamber
100
, there is shown a first electrode
104
, representing the workpiece holder on which a workpiece
106
is positioned during etching. The first electrode
104
may be implemented by any suitable chucking system, e.g. electrostatic, mechanical, clamping, vacuum, or the like, and is surrounded by an insulator
108
. During etching, RF power supply
110
may generate RF power having a frequency of about 2 MHz to about 27 MHz to first electrode
104
.
Above workpiece
106
, there is disposed a second upper electrode
112
, which is coupled to a reactor top formed of a conductive material such as aluminum. The reactor top is coupled to confinement rings
102
. Second upper electrode
112
is electrically insulated from grounded chamber wall
116
by insulator
118
and is powered by an RF power supply
120
to facilitate the formation of a plasma out of etchant source gases supplied via a gas line (not shown). RF power supply
120
may have any suitable frequency, such as 2 MHz to 27 MHz. It shall be appreciated by those skilled in the art that the plasma processing chamber of
FIG. 1
represents a capacitively coupled plasma processing chamber although the confinement rings also operate well with other types of processing chambers such as inductively coupled plasma processing chambers.
Other approaches for confining plasma include magnetic confinement. The U.S. Pat. No. 5,767,628 and U.S. Pat. No. 5,936,352 both use magnetic confinement to generate a partially confined plasma and are hereby incorporated by reference.
Keller et al. in U.S. Pat. No. 5,767,628 discloses a processing apparatus including a chamber, an induction coil for providing a RF induced electromagnetic field to generate a plasma, and a plurality of magnetic dipoles that produce a confined plasma within the processing chamber.
Samukawa et al. in U.S. Pat. No. 5,936,352 discloses a processing apparatus that includes a plasma chamber having a first set and a second set of parallel electromagnetic elements. An oscillating energy having a first phase is applied to the first set of parallel electromagnetic elements. Another oscillating energy having an opposite phase is applied to the second set of parallel electromagnetic elements to produce oppositely moving energy fields in the processing chamber such that electrons are confined in a plasma produced in the chamber.
In spite of the well-known method for confining plasma either partially or fully, a novel system and method for generating confined plasma is needed. This need is caused by the semiconductor industry shifting from 200 mm wafers to 300 mm wafers. The 300 mm wafer occupies more than twice the area of the 200 mm wafer. As a result of the 300 mm wafer being larger, the operating conditions for semiconductor fabrication change substantially. Prior art methods for generating a confined plasma that worked for 200 mm wafer do not work on 300 mm wafers due to the higher gas flows and higher radio frequency (RF) power levels.
Therefore it would be beneficial to provide an apparatus that generates a confined plasma that occupies a substantially larger volume.
Additionally, it would be beneficial to provide an apparatus that confines plasma in processing chamber that operates using high gas flows.
It would also be beneficial to provide an apparatus that confines plasma in a processing chamber that operates with high RF power levels.
Furthermore, it would be beneficial to provide a method for generating a confined plasma in a processing chamber that operates using high gas flows.
Further still, it would be beneficial t
Fischer Andreas
Kennedy Bill
Loewenhardt Peter
Trussell Dave
Lam Research Corporation
Lam Research Corporation
Lee Wilson
LandOfFree
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