Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
2000-04-26
2003-01-07
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C156S345430, C156S345470, C118S7230AN, C118S728000
Reexamination Certificate
active
06502530
ABSTRACT:
The present invention is generically directed on improvements with respect to so-called shower head gas inlet technique into a plasma discharge space of a plasma reactor operated with a plasma which is electrically fed by RF, RF plus DC or pulsed RF. Thereby, it is directed to parallel plate reactors, where RF energy is coupled to the discharge space via a pair of electrodes in a capacitance plate-like arrangement, in contrary to other reactors, where the discharge energy is introduced via microwave coupling or via induction field.
Such capacitive-coupling plasma reactors are commonly used for exposing at least one substrate at a time to the processing action of a plasma glow discharge. A wide variety of such processes are known and used to modify the nature of the substrate's surfaces. Depending on the process and in particular on the nature of gas injected in the glow discharge space of the reactor, one can modify the substrates surface property, apply thin films thereto or remove, especially selectively remove, material therefrom.
The substrates can be plane or curved as e.g. car windshields. In such case the arrangement of the electrodes wherebetween the plasma discharge space is defined may be not coplanar, but accordingly curved in parallelism, so that the distance between the curved surface of the substrate and an electrode is substantially constant over the substrate's surface extent.
Although the present application claims for plasma reactors, it fully describes different inventive methods to manufacture substrates by means of process steps being performed by the claimed plasma reactor. Such manufacturing processes are especially directed on semiconductor waters, disks for memory devices, flat display panels, window panes and web or foils.
The processes for surface treatment of substrates performed in a vacuum vessel, wherein a plasma discharge is generated with an RF component of electric field, are widely known as PVD, PECVD, as reactive ion etching, ion plating etc. processes.
In
FIG. 1
there is schematically shown a commonly used design for an RF plasma reactor with a “shower head” gas inlet. A conventional RF plasma reactor comprises a reactor vessel
1
with a pumping port
3
. Oppositely disposed, spaced metallic surfaces
4
and
6
are the plasma discharge electrodes and concomitantly define the plasma discharge space
8
. Between the two electrode surfaces
4
and
6
the plasma discharge supplying electric field E at least with an RF component is applied.
At least one of the plasma discharge electrode surfaces
4
,
6
is provided with a multitude of gas feed openings
10
, the respective electrode being the surface of a plate
11
. With respect to the plasma discharge space
8
on the backside of that plate
11
there is provided a reservoir chamber
12
with a back wall
14
and lateral rim wall
16
. Centrally with respect to the extent of the reservoir chamber
12
there is provided a gas inlet opening and feed line
18
. Besides of the gas feed openings
10
and opening
18
the reservoir chamber
12
is sealed.
The bordering metallic walls and plate enclosing the reservoir chamber
12
are fed with plasma discharge supplying electric energy as by a central electric feed line
20
. As reactor vessel
1
is customarily not operated at the same electric potential as the electrode surface
4
, especially not on full RF power, but is customarily operated at a reference potential as on ground potential, the overall reservoir chamber
12
is mounted within the reactor vessel
1
in an electrically isolated manner as schematically shown by an electrically isolating support and feed-through
22
. The centrally disposed gas feed line
18
is analogously connected to a usually grounded gas supply line
24
to the reactor vessel
1
via an electrically isolating connector
26
.
The gas feed openings
10
in electrode surface
4
and plate
11
of reservoir chamber
12
have a small gas conductance and, accordingly, a high gas flow resistance factor, so that the internal volume of reservoir chamber
12
, centrally fed with inlet gas, acts as distributing and pressure equalisation chamber to feed gas through the gas feed openings
10
at a well-controlled and desired manner most often as homogeneously distributed as possible along the electrode surface
4
and into the plasma discharge space
8
. As shown in
FIG. 1
gas fed to the overall reactor is submitted to a large change of electric potential (pipe
24
to feed line
18
). Thereby, the conditions in the area where this high potential difference occurs, i.e. at the connector
26
, is quite critical for avoiding occurrence of unwanted plasma discharge therein.
A further drawback of this known arrangement is primarily its low response time. As the internal volume of the reservoir chamber
12
must be rather large to allow even gas distribution and constant pressure along plate
11
, a rather large quantity of gas is accumulated in this reservoir chamber
12
at a relatively high pressure. Thus, if during processing one wants to change the gas composition or outflow rate, such change, considered in the plasma discharge space, will occur during a rather uncontrolled transient phase with large time constants up to reaching the desired stable, newly established gas composition and/or outflow rate.
Additionally, the volume of reservoir chamber
12
must be evacuated by vacuum pumping prior to starting a treatment process in the reactor, which takes the more time the larger the respective volume is construed. This especially considering the fact that the volume
12
is only connected to the pumping port of the vessel via small, low-conductance openings
10
, so that pre-processing conditioning of the overall reactor, including degassing walls, takes a long time. Nevertheless and due to the low-conductance gas feed openings
10
and the large volume of reservoir chamber
12
this technique results in a satisfying control of gas outflow distribution along the electrode surface
4
, as e.g. in a homogeneous distribution. By varying the density of gas feed openings
10
along the plasma discharge space bordering electrode surface
4
the gas distribution may easily be tailored according to specific needs.
It is a generic object of the present invention to improve a shower head RF reactor as principally shown in
FIG. 1
, thereby maintaining its advantages. We understand under the term RF reactor a reactor wherein plasma discharge is electrically supplied with at least an RF component of electric energy.
Under a first aspect of the present invention this object is resolved by an RF plasma reactor comprising a reactor vessel and therein a pair of electrodes consisting of spaced apart and oppositely disposed metallic surfaces defining therebetween a plasma discharge space, at least one of the metallic surfaces being the surface of a metallic plate having a multitude of gas feed openings therethrough and through the metallic surface towards the discharge space and from a distribution chamber extending along the plate opposite the discharge space, whereby the distribution chamber has a back wall opposite and distant from the plate and comprises a gas inlet arrangement with a multitude of gas inlet openings, which are distributed along the back wall and which are connected to at least one gas feed line to the reactor.
Thereby and in opposition to well-known techniques according to
FIG. 1
, gas inlet to the inventively provided distribution chamber is not performed locally, but via a multitude of gas inlet openings. This leads to the advantage that the requirements to the distribution chamber itself with respect to large volume pressure equalisation are significantly reduced compared with the teaching according to FIG.
1
: The volume of the distribution chamber may be significantly reduced, which significantly improves response time when varying gas flow and/or gas composition to the plasma discharge space.
The above mentioned object is resolved under a second aspect of the present invention by an RF plasma react
Barreiro Jean
Chevrier Jean-Baptiste
Schmitt Jacques
Turlot Emmanuel
Crowell & Moring LLP
Mills Gregory
Unaxis Balzers Aktiengesellschaft
Zervigon Rudy
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