Resonant chamber applicator for remote plasma source

Details Resonant chamber applicator for remote plasma source Resonant chamber applicator for remote plasma source

2000-06-13

2003-08-05

Wong, Don (Department: 2821)

Electric lamp and discharge devices: systems

Discharge device load with fluent material supply to the...

Plasma generating

C118S7230ME, C156S345420, C250S492200

Reexamination Certificate

active

06603269

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a remote plasma source for exciting a process gas into a plasma state. More particularly, the present invention relates to a plasma applicator for delivering excited gas species into a processing chamber in which a substrate is to be processed.
2. Description of the Related Art
Plasma processing is an important tool of the semiconductor manufacturing industry. This processing uses electromagnetic radiation to strike a plasma that produces a reactive species that is used for such process steps as wafer etching. A plasma may be produced directly above the surface of the wafer within the process environment, or the plasma may be remotely generated in an applicator, and then conducted to the surface of the wafer.
FIG. 1
illustrates a known, remote plasma source
10
which can be used as a stand alone plasma source for cleaning, etching or depositing materials in a processing chamber
4
or in conjunction with other plasma sources inside or outside a processing chamber. The remote plasma source
10
generally comprises a microwave generator
2
coupled by a waveguide
11
in communication with a generally cylindrically-shaped resonant cavity or chamber
12
.
The resonant chamber
12
, generally defined by a microwave reflective shell such as an outer metal housing or cover
13
, includes a microwave transparent tube
14
that extends down through the chamber
12
along its radial axis for the passage of gases to be activated or excited and delivered to the processing chamber
4
. The tube
14
is typically made of a microwave transparent, dielectric material, such as sapphire, quartz, ceramic, borosilicate glass or the like. A compressible material layer
25
may be disposed between the outer shell
13
and the tube
14
to secure the two members while allowing for differences in expansion under a wide range of temperatures.
The housing
13
of the plasma source
10
has a removable first lid
20
with a gas inlet port
21
and a removable second lid
22
with a gas outlet port
23
. The gas inlet and outlet ports
21
and
23
are typically aligned with and centered on the radial axis of the chamber
12
. The gas inlet port
21
in the first lid
20
supplies low pressure precursor gases into the microwave transparent tube
14
in the resonant chamber
12
where the gases can be ionized. The gas outlet port
23
in the second lid
22
allows the excited gases to flow from the resonant chamber
12
into the processing chamber (not shown).
A rectangular, transverse slot
24
is disposed through a cylindrical central portion
6
of the outer metal cover
13
to inject microwave energy from the microwave generator through the internal microwave tube wall
14
to the cavity. The microwave energy enters the resonant chamber
12
through the cylindrical side wall of portion
6
to excite a gas provided therein into a plasma state.
A plurality of coolant passages
15
are disposed in the cylindrical walls of the central portion
6
of the outer metal cover
13
so that a cooling fluid may be passed through them in order to dissipate heat generated in the plasma cavity. The cooling fluid enters a coolant inlet port
16
whereupon it flows through an inlet manifold
17
disposed in the first lid
20
, down parallel flow paths through the passages
15
to an outlet manifold
18
and exits via the coolant outlet port
19
disposed in the second lid
22
.
FIGS. 2-6
depict another, known plasma applicator of a different design. Referring first to
FIGS. 2 and 3
, the plasma applicator
30
includes a removable, front cover plate
32
, a removable, rear cover plate
33
and a central body member
31
having a resonant chamber
46
. The central body member
31
and resonant chamber
46
are cylindrical in shape, the radial axis of which extends through the front and rear cover plates
32
and
33
. A gas inlet port
34
and a gas outlet port (not shown) are formed on generally opposite sides of the cylindrical side walls of the body
31
and are typically centered approximately midway between the front cover plate
32
and rear cover plate
33
. A coolant inlet port
35
and coolant outlet port
36
are located generally adjacent to one another on the same side of the body
31
.
Situated between the front cover plate
32
and the body
31
are a microwave transparent window member
37
and an aperture plate
38
having a rectangular aperture
39
which is centered in the middle of the plate
38
. The window member
37
is usually made of aluminum nitride, a material which is transparent to microwaves, yet substantially impermeable to the plasma gases typically contained within the resonant chamber
46
. Three O-rings
40
,
41
and
42
, form a pressure-tight seal between the front cover plate
32
, the window member
37
, the aperture plate
38
, and the body
31
. As best seen in
FIG. 6
, the O-ring
40
is an aluminum member disposed in the front cover plate
32
and having teats
58
formed along opposing sides of the O-ring. A force is applied by the O-ring
40
against the window
37
which pushes it towards the O-ring
41
and the aperture plate
38
.
The front cover plate
32
includes a plurality of cover plate bolt holes
43
for securing the cover plate
32
to the remainder of the assembly. A plurality of waveguide bolt holes
44
are also disposed in the front cover plate
32
in order to permit the attachment of the waveguide portion of a microwave generator (not shown) to the cover plate
32
. Finally, a generally rectangular opening
45
is also disposed in the cover plate
32
in order to permit passage of microwaves from a microwave generator through the cover plate
32
, the aluminum nitride window
37
, the rectangular aperture
39
of the aperture plate
38
and into the resonant chamber
46
.
FIG. 4
shows the end of the plasma applicator
30
containing the rear cover plate
33
assembly. Situated between the rear cover plate
33
and the body
31
are an aluminum nitride window
47
and a center plate
48
having a sensor port
49
disposed in the center of the plate
48
. O-rings
50
and
51
are placed between the body
31
, the center plate
48
and the aluminum nitride window
47
in order to form a pressure-tight seal. A microwave detector
52
is attached to the center of the rear cover plate
33
directly over a rear cover plate port
53
in order to receive and detect microwaves passing from the resonant chamber
46
, through the sensor port
49
, the aluminum nitride window
47
and the rear cover plate port
53
. The detector
52
measures the amount of microwave energy in the chamber
46
thereby permitting the operator to make energy adjustments as operational conditions require.
FIG. 5
shows the coolant flow path of the plasma applicator
30
. Coolant fluid, such as water, enters the body
31
via the coolant inlet port
35
. The coolant then flows into a circular inlet manifold
55
which is formed within and encircles the body
31
. From the inlet manifold
55
the coolant flows in parallel paths through a plurality of straight, parallel channels
56
to a circular outlet manifold
57
which, like the inlet manifold
55
, encircles the body
31
. The coolant exits through the coolant outlet port
36
. This arrangement has some problems however. It has been noted by the present applicants that the water pressure in some channels can be greater than in others. It is believed that this can result in uneven water flow rates and uneven heat removal rates which in turn can cause localized hot spots within the body
31
.
The use of aluminum nitride material for the window
37
presents certain other problems. While effective for its transparency to microwaves and impermeability to gases, aluminum nitride is a material which is typically relatively brittle and can crack or fracture relatively easily in the high temperature, operational environment of a microwave applicator.
SUMMARY OF THE PREFERRED EMBODIMENTS
A remote microwave plasma applicator of an improved des

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