Electric lamp and discharge devices: systems – Discharge device load with fluent material supply to the... – Electron or ion source
Reexamination Certificate
2000-03-31
2002-05-14
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Discharge device load with fluent material supply to the...
Electron or ion source
C156S345420, C118S7230IR
Reexamination Certificate
active
06388383
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a method of and apparatus for obtaining electrically neutral gas atoms from ionizable gas molecules including the atoms and, more particularly, to such a method and apparatus wherein the gas molecules are converted into a plasma by plural oscillating electromagnetic fields.
BACKGROUND ART
It is known that electrically neutral gas atoms can be dissociated from ionizable gas molecules including the atoms by supplying the molecules to a plasma generator including a chamber having an electromagnetic field applied to it. The electromagnetic field ionizes the molecules to form a plasma including positively charged ions, electrons, and dissociated electrically neutral atoms.
Such plasma generators are extensively used on a commercial basis to process workpieces, such as semiconductor wafers, glass panels used in flat panel displays, and metal plates. The plasmas are frequently employed to etch materials from the workpieces or are used in chemical vapor deposition (CVD) processes for depositing materials on the workpieces.
In one class of processors, the electromagnetic field is coupled to the gas in the chamber via a dielectric window from a planar or substantially planar plasma excitation coil located outside the chamber. The coil produces an oscillating RF electromagnetic field coupled into the chamber via the window, which is usually in the chamber roof. The oscillating RF field has magnetic and electric field components that propagate through the dielectric window to heat electrons in the gas in a portion of the plasma in the chamber close to the window. The oscillating RF fields induce in the plasma currents that heat electrons in the plasma. The spatial distribution of the magnetic field in the plasma portion close to the window is a function of the sum of individual magnetic field components produced by each turn of the coil. The magnetic and electric field components produced at each point along the coil are respectively functions of the magnitude of RF current and voltage at each point.
The current and voltage differ for different points because of transmission line effects of the coil at the frequency of the RF source. For spiral-like designs, e.g., as disclosed by Ogle, U.S. Pat. No. 4,948,458, and Holland et al., U.S. Pat. No. 5,759,280, the RF currents in the coil are distributed to produce a torroidal shaped magnetic field region in the portion of the plasma close to the window, which is where power is absorbed by the gas to excite the gas to a plasma. The electric field components start at one portion of the coil, propagate through the window in the chamber and return through the window to a second portion of the coil having a potential different from the first portion.
At pressures greater than 10 millitorr, gas phase collisions of electrons, ions, and neutrons in the plasma prevent substantial diffusion of the plasma charged particles outside the torroidal region. As a result, there is a relatively high plasma density (i.e. flux) in a ring like region below the window but low plasma fluxes below the center and peripheral window portions.
Plasma processing of such workpieces is typically performed at vacuum pressures of between 1 millitorr and 100 millitorr, in relatively large vacuum chambers. The vacuum chambers frequently have a diameter of about 30 centimeters. The workpiece is usually mounted on a chuck located on or in proximity to the chamber floor such that there is typically about a 12 centimeter separation between the coil and workpiece. The plasma in such a chamber typically has a concentration of approximately 10
9
charge particles per cubic centimeter. The ionized particles and the dissociated atoms are evacuated from the processing chamber by a pump connected to an outlet of the chamber. There is no particular effort to provide a source of dissociated atoms in the effluent evacuated from the chamber.
We, and others, invented an apparatus and method which enables a plasma generator somewhat similar to the prior art plasma chambers excited by RF coils to be used as a source of electrically neutral dissociated atoms. The source supplies the atoms to a downstream workpiece processor, in particular a resist etcher for a semiconductor to wafer. Our copending, commonly assigned, U.S. patent application Ser. No. 09/052,906, filed Mar. 31, 1998, now U.S. Pat. No. 6,203,657, entitled “Inductively Coupled Plasma Downstream Strip Module,” discloses such an apparatus and method wherein a plasma generator serves as a source of electrically neutral dissociated atoms for a downstream etcher.
FIG. 1
is a schematic diagram of such an etcher.
In the arrangement of
FIG. 1
gas from a suitable source
8
, e.g., oxygen gas (O
2
) or water vapor (H
2
O), flows into plasma generator
10
where the gas is converted into an RF plasma including ionized particles, electrons and dissociated neutral atoms (e.g., O resulting from O
2
or H
2
O being dissociated). The dissociated electrically neutral atoms flow from generator
10
into secondary cylindrical chamber
12
, thence into cylindrical processor chamber
13
through openings
14
in quartz baffle plate
16
. Gas from a second source
9
flows through tube
15
into chamber
12
. Processing chamber
13
includes chuck
18
for holding workpiece
20
in situ. RP source
22
, typically having a frequency of 13.56 MHz, supplies an RF bias Voltage to chuck
18
. Gas in processing chamber
13
is sucked out of the processing chamber by vacuum pump
23
through annular exhaust
24
, at the base of chamber
13
. The vacuum pump maintains the pressure in generator
10
, as well as chambers
12
and
13
, in the range of about 500 millitorr to 5 torr.
Plasma generator
10
includes chamber
26
having interior wall surfaces shaped as a right parallelepiped. Chamber
26
has a root formed of dielectric window
28
which carries spiral, substantially planar coil
30
, having interior and exterior excitation terminals, as disclosed, e.g., by Ogle, U.S. Pat. No. 4,948,458. The excitation terminals of coil
30
are connected via matching network
31
to be powered by RF plasma excitation source
32
, typically having a frequency of 13.56 MHz and an output power of 2 kilowatt. Matching network
31
typically has a T configuration, including a fixed series capacitor, as well as variable series and shunt capacitors having values controlled by a controller (not shown).
The walls and base
34
of chamber
26
are metal, electrically grounded and arranged to include a dielectric, e.g., quartz, liner
36
on the inner surfaces of the chamber. All interior surfaces of chambers
12
,
13
and
14
, as well as metal grounded conduit
38
connecting chambers
12
and
26
, are lined with the same solid dielectric that lines chamber
26
. The dielectric liners in chambers
12
,
13
,
26
and conduit
38
are made of a material that prevents recombination of the oxygen neutral atoms into O
2
oxygen molecules and captures charge particles. The gas incident on workpiece
20
typically has a total density of about 10
16
atoms per cubic centimeter at a pressure of 1 Torr, and charge particle density of less than 10
6
charges per cubic centimeter, i.e., the charge particle concentration is less than 10
10
. In contrast, in commercial prior art processors wherein the plasma generator and the workpiece are in the same chamber, the gas incident on the workpiece typically has a total concentration of about 10
14
atoms per cubic centimeter at a 10 millitorr pressure and a charge particle density of about 10
9
charges per cubic centimeter, i.e., a charge particle concentration of about 10
5
.
Chamber
26
includes opposed end walls
40
and
42
respectively including aligned ports
44
and
46
. Conduit
38
includes a bend just downstream of port
46
to assist in capturing a large number of charge particles which are electrically attracted to the metal conduit wall and are captured by the quartz liner in the conduit. The walls of cylindrical chambers
12
and
13
and the roof of chambe
Collison Wenli
Ni Tuqiang
Alemu Ephrem
Lam Research Corporation
Lowe Hauptman & Gilman & Berner LLP
Wong Don
LandOfFree
Method of an apparatus for obtaining neutral dissociated gas... 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 of an apparatus for obtaining neutral dissociated gas..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of an apparatus for obtaining neutral dissociated gas... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2828774