Electric lamp and discharge devices: systems – Discharge device load with fluent material supply to the... – Plasma generating
Reexamination Certificate
2000-04-06
2003-01-14
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Discharge device load with fluent material supply to the...
Plasma generating
C315S111210, C118S7230AN
Reexamination Certificate
active
06507155
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is generally related to controlling power distribution from a single power source to multiple components. More particularly, this invention is related to distribution of RF power to a plurality of radio frequency (RF) coils disposed on a RF plasma reactor.
2. Background of the Related Art
Plasma reactors are typically employed in performing various processes on semiconductor wafers, including etching processes and chemical vapor deposition processes. An inductively coupled RF plasma reactor typically has an inductive coil antenna wound around the reactor chamber and connected to a plasma source RF power supply. An inductively coupled RF plasma reactor can achieve a very high plasma ion density for high production throughput, while avoiding a concomitant increase in ion bombardment damage of the wafer.
Inductively coupled plasma reactors typically have a plasma ion density distribution that can vary greatly depending upon various processing parameters, including the particular process gas or gas mixture introduced into the reactor chamber. For example, the plasma ion density may be high at the wafer center and low at the wafer periphery for one process gas, while for another process gas it may be the opposite pattern (i.e., low at the wafer center and high at the wafer periphery). As a result, the RF coil designs are customized for each different process or process gas to provide commercially acceptable uniformity across a wafer surface in the reactor. A plurality of RF coils, typically two coils, are utilized to improve plasma uniformity in the processing chamber, and each RF coil is connected to a separate individual RF power source through separate RF match networks dedicated to control the amount of RF power delivered to the RF coil.
FIG. 1
is a cross sectional schematic view of a typical plasma processing chamber having two RF coils disposed on a lid of the chamber. The plasma processing chamber generally includes a vacuum chamber
10
having a generally cylindrical side wall
15
and a dome shaped ceiling
20
. A gas inlet tube
25
supplies process gas (e.g., chlorine for etch processing) into the chamber
10
. A substrate support member or wafer pedestal
30
supports a substrate, such as semiconductor wafer
35
, inside the chamber
10
. An RF power supply
40
is also typically connected to the pedestal
30
through a conventional RF impedance match network
45
. A plasma is ignited and maintained within the chamber
10
by RF power inductively coupled from a coil antenna
50
consisting of a pair of independent (electrically separate) antenna loops or RF coils
52
,
54
wound around different portions of the dome-shaped ceiling. In the embodiment shown in
FIG. 1
, both loops are wound around a common axis of symmetry coincident with the axis of symmetry of the dome-shaped ceiling
20
and the axis of symmetry of the wafer pedestal
30
and wafer
35
. The first RF coil
52
is wound around a bottom portion of the dome-shaped ceiling
20
while the second RF coil
54
is positioned centrally over the ceiling
20
. First and second RF coils
52
,
54
are separately connected to respective first and second RF power sources
60
,
65
through first and second RF impedance match networks
70
,
75
. RF power in each RF coil
52
,
54
is separately controlled. The RF power signal applied to the first RF coil (bottom/outer antenna loop)
52
predominantly affects plasma ion density near the periphery of the wafer
35
while the RF power signal applied to the second RF coil (top/inner antenna loop)
54
predominantly affects plasma ion density near the center of the wafer
35
. The RF power signals delivered to each of the RF coils are adjusted relative to each other to achieve substantial uniformity of plasma ion distribution over a substrate disposed on a substrate support member.
The addition of an independent RF power source and associated RF impedance match network for with each RF coil increases the equipment and operation costs for each additional RF coil utilized on a processing chamber, resulting in increased cost for processing wafers. Furthermore, the independent RF source and matching network configuration presents difficulties in matching the impedance of the coils, which leads to more difficulties in controlling the plasma power delivered to each of the coils.
Another attempt to control plasma power in an inductively coupled plasma reactor having multiple coils utilizes a plurality of high power relays for switching connection from the power source to each of the coils. However, the switching mechanisms do not provide efficient operation of the coils and do not provide sufficient control of the power delivered to each of the coils on a continual basis.
Therefore, there is a need for an apparatus for distributing power from a single power source to a plurality of coils disposed on a processing chamber which provides controllable plasma uniformity across a substrate disposed in the processing chamber.
SUMMARY OF THE INVENTION
The invention generally provides method and apparatus for distributing power from a single power source to a plurality of coils disposed on a processing chamber which provides controllable plasma uniformity across a substrate disposed in the processing chamber.
The apparatus for distributing power from a power source to two or more coils disposed on a process chamber comprises a connection between the power source and a first coil; a series capacitor connected between the power source and a second coil; and a shunt capacitor connected to a node between the second coil and the power source, the shunt capacitor being connectable to a ground connection.
The method for distributing power from one power source to a plurality of coils comprises connecting a first coil between the power source and a ground connection; connecting a power distribution network to the power source, wherein the power distribution network comprises a series capacitor and a shunt capacitor; and connecting a second coil between the power distribution network and a ground connection.
The invention also provides an apparatus for plasma processing comprising a chamber; a first coil and a second coil disposed on the chamber; a power source connected to the first coil; and a power distribution network connected between the second coil and the power source, the power distribution network comprising a series capacitor connected between the power source and the second coil; and a shunt capacitor connected to a node between the second coil and the power source, the shunt capacitor being connectable to a ground connection.
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Yamada et al., “Mode for a Large Area Multi-Frequency Multiplanar Coil Inductively Coupled Plasma Source”, Journal of Vacuum Science and Technology A, Sep./Oct. 1996, pp. 2859-2870.
PCT International Search Report from PCT/US 01/12178, Dated Jan. 25, 2002.
Barnes Michael
Holland John
Todorov Valentin
Applied Materials Inc.
Bach Joseph
Moser Patterson & Sheridan
Vu Jimmy T.
Wong Don
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