Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
1999-11-10
2001-06-12
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C156S345420
Reexamination Certificate
active
06244211
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma processing apparatus employing a plasma to form a thin film on a surface of a sample, etching a surface of a sample, and the like.
2. Description of the Background Art
A conventional radio frequency (RF) plasma processing apparatus with parallel plates has been widely used as an apparatus using a plasma to process a sample, such as a substrate, a semiconductor wafer (simply referred to as a “wafer” hereinafter), in a processing chamber thereof. In this plasma processing apparatus, an RF power is applied to one or both of electrodes to generate a plasma between the electrodes and a self-bias voltage between the plasma and a sample allows ions to be introduced into a surface of the sample. This plasma processing apparatus is configured to form a thin film through plasma CVD, provide etching process, and the like.
For the above-mentioned parallel plate RF plasma processing apparatus, however, it is difficult to achieve required fine pattern formation and damage reduction associated with high integration and performance of semiconductor devices. In other words, in order to implement such processes, it is important to generate and control a low-pressure high-density plasma. Furthermore, the plasma should be uniform over a large area to process a wafer of a large diameter.
To satisfy such demands, various plasma sources have been proposed and applied to semiconductor processes. In particular, an inductively coupled plasma apparatus employing an RF antenna
7
, as shown in
FIG. 11
, may be applied to semiconductor processes since the apparatus can relatively simply be constructed and is also capable of generating a low-pressure high-density plasma.
In the apparatus, as shown in
FIG. 11
, that side of a processing chamber which is opposite to a sample mounting stage
4
is constructed of a dielectric window
18
made, e.g., of quartz glass. Dielectric window
18
has an external surface having mounted thereto RF antenna
7
comprised of a planar, spiral coil. An RF electric field is radiated in processing chamber
2
through RF antenna
7
. By allowing electrons present in the electromagnetic field to collide with neutral particles of processing gases, the processing gases disociate ions and neutrals, resulting generation of a plasma. Ions in the plasma are accelerated toward a sample by an RF bias voltage independently applied to sample mounting stage
4
and the ions are thus introduced into a sample to form a thin film, provide an etching process, and the like.
For the above-mentioned inductively coupled plasma processing apparatus used to form a thin film, provide etching process, and the like, dielectric window
18
of quartz glass or the like existing between RF antenna
7
and a generated plasma degrades the transmission efficiency of an RF power to the plasma. Accordingly, the power applied to RF antenna
7
should be increased to obtain a low-pressure high-density plasma.
Furthermore, the phenomenon that plasma density rapidly increases at more than an RF power (i.e., a mode jump phenomenon) is frequently observed and processing conditions can thus be disadvantageously limited.
Furthermore, the ionized species, reaction products and the like of the processing gases can be deposited on an internal surface of dielectric window
18
and ions can sputter dielectric window
18
and thus vary its thickness, so that L and C matching circuits formed via dielectric window
18
can change to disadvantageously vary a discharge condition. In particular, a conductive film deposited on dielectric window
18
can cause short-circuit of an RF electric field.
Furthermore, dust particles can be produced from a film deposited on dielectric window
18
by ion sputtering on, dielectric window
18
, or the like.
Furthermore, if a grounded electrode (not shown) for an RF bias voltage applied to a sample is provided around mounting stage
4
, the bias is not uniformly applied to the sample, often disadvantageously resulting in uneven processing rate. In particular, in the case that the grounded electrode is far from a sample, an arc discharge can be occurred between the stage and other grounded metallic parts of the apparatus.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above disadvantages.
An object of the present invention is to generate a low-pressure high-density plasma to achieve a high processing rate.
Another object of the present invention is to apply an RF bias voltage uniformly to a sample to achieve a more uniform process.
To achieve the above objects, a plasma processing apparatus in one aspect of the present invention is a plasma processing apparatus for processing a sample in a processing chamber including therein one or more RF antennas and a grounded electrode located opposite to the sample so that when the RF antenna receives an RF power an inductively coupled plasma is excited in the processing chamber to provide the above process.
The above configuration with an RF antenna provided in a processing chamber can enhance the transmission efficiency of an RF power to a plasma and consequently can generate a low-pressure high-density plasma with low power to achieve high processing rate in the apparatus. Furthermore, a grounded electrode located opposite to a sample allows an RF bias voltage to be uniformly applied to the sample to uniformly process the sample. Furthermore, since one or more RF antennas may be used, a plurality of RF antennas may be used to vary the plasma density distribution in the processing chamber.
In the present invention, preferably the plasma processing apparatus has a device applying an RF bias voltage or a direct current voltage to the electrode located opposite to a sample (opposite electrode).
With the above configuration, a self-bias voltage can be produced at the opposite electrode and the opposite electrode can be sputtered to allow the control of the composition ratio between ions and neutral particles in a plasma, depending on appropriate material selection for the opposite electrode.
In the present invention still preferably the plasma processing apparatus has the RF antenna and the opposite electrode that are spaced.
The configuration with the opposite electrode and the RF antenna spaced can prevent short-circuit between the RF antenna and the opposite electrode if a conductive foreign matter or conductive film deposits on or adsorbs on the RF antenna.
In another aspect of the present invention, the plasma processing apparatus has the RF antenna made of a material having no more than {fraction (1/100)} the volume resistivity of the opposite electrode.
With the above configuration, if the RF antenna is in contact with the opposite electrode most of RF current can flow in the RF antenna rather than the opposite electrode and the RF antenna can thus generate a low-pressure high-density plasma.
In the present invention still preferably the RF antenna and the opposite electrode are in contact with each other.
The above configuration can reduce a distance between the opposite electrode and a sample. This ensures that an RF bias voltage are more uniformly applied to the sample and that the aspect ratio of processing apparatus is also reduced in size.
In another aspect of the present invention, the plasma processing apparatus has the RF antenna buried in the opposite electrode such that the RF antenna is partially exposed to the plasma.
The above configuration can reduce dust particles, preventing reaction products and the like from depositing on a corner otherwise formed by the opposite electrode and the RF antenna or a gap otherwise created between the opposite electrode and the RF antenna that is attributed to poor working precision, thermal distortion and the like.
In the present invention still preferably the plasma processing apparatus includes a dielectric film covering a portion of the RF antenna that contacts the opposite electrode.
With the above configuration, the RF antenna can be electrically isolated from the opposite
Nishikawa Kazuyasu
Oomori Tatsuo
Ootera Hiroki
Alejandro Luz
McDermott & Will & Emery
Mills Gregory
Mitsubishi Denki & Kabushiki Kaisha
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