Coating processes – Direct application of electrical – magnetic – wave – or... – Plasma
Reexamination Certificate
1996-12-27
2001-02-27
Padgett, Marianne (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Plasma
C427S579000, C438S788000, C438S792000
Reexamination Certificate
active
06194037
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma processing method and a plasma processing apparatus, and particularly to a plasma enhanced CVD (Chemical Vapor Deposition) method and a plasma enhanced CVD apparatus which are used for manufacturing semiconductor devices and liquid crystal display (LCD) devices.
2. Description of the Related Art
According to a conventional CVD method, while the interior pressure of a processing chamber is being controlled at a predetermined pressure through use of a predetermined gas, an RF power is applied between a cathode and an anode by an RF generator so as to generate plasma to thereby form a film on a substrate placed on a substrate table.
After the elapse of a predetermined period of time required to form the film, the application of the RF power, the feed of the reaction gas, and the pressure control of the processing chamber are simultaneously terminated, and the processing chamber is evacuated to establish a high vacuum therein. After the interior of the processing chamber reaches a predetermined degree of vacuum, the substrate is lifted off the substrate table, and subsequently the substrate is taken out from the processing chamber by a transfer robot.
However, in the case where a substrate is transferred in accordance with the above-described sequence of the conventional plasma enhanced CVD method after the formation of a film on the substrate, a transfer error occurs in some cases due to the following causes: the substrate remains adhered to an adjacent cathode while being transferred; the substrate once adheres to the cathode and then drops onto the substrate table; and the dropped substrate breaks. Furthermore, in some cases, the substrate sparks to a nearby grounded site. Such a spark blows out a part of the formed film or a device pattern, resulting in pattern missing. This has lead to a so-called dielectric breakdown wherein an insulated portion breaks down. As a result of such a potential substrate transfer error or dielectric breakdown, the sequence of the conventional plasma enhanced CVD method fails to provide a stable film formation process.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a plasma processing method and a plasma processing apparatus capable of preventing a substrate transfer error or a dielectric breakdown which may occur during the transfer of a plasma-processed substrate.
The inventors of the present invention have carried out extensive studies, and as a result, have come to think that the above-described substrate transfer error and dielectric breakdown are caused by a charge established in a substrate by plasma discharge while a film is being formed, as well as by a charge established in the substrate by separation electrification which takes place when the substrate is separated from a substrate table. That is, when the substrate, which has already been charged on the substrate table by plasma discharge conducted to form a film thereon, is lifted off the substrate table under high vacuum, a separation electrification occurs, which further increases the electric potential of the charged substrate. This electrification-induced electric potential increases as the lifting speed of the substrate increases. By contrast, as the lifting speed decreases, the electrification-induced electric potential is suppressed accordingly. As described above, since the substrate is charged by plasma and the electrification-induced electric potential of the charged substrate increases due to the separation-electrification, strong static electricity is generated, so that the substrate remains electrostatically adhered to an adjacent cathode while being transferred, the substrate electrostatically once adheres to the cathode and subsequently drops onto the substrate table, or the dropped substrate breaks, thus causing a transfer error. Moreover, since the charge established in the substrate tends to escape to a nearby grounded site, the substrate sparks to the nearby grounded site. Such a spark blows out a part of a formed film or a device pattern, resulting in pattern missing. This leads to a so-called dielectric breakdown wherein an insulated portion breaks down.
The present invention was made based on the above-described findings, and according to a first aspect of the present invention, there is provided a first plasma processing method comprising the steps of:
performing plasma processing for a substrate placed on a substrate table in a processing chamber through use of plasma generated by applying an RF power to a gas or gases within the processing chamber;
exposing the substrate to a predetermined gas atmosphere within the processing chamber for a predetermined period of time after stopping the application of the RF power; and
thereafter taking the substrate out of the processing chamber.
The inventors of the present invention consider that an electrification-induced charge established in a substrate due to plasma discharge during plasma processing is removed by exposing the substrate to a predetermined gas atmosphere within the processing chamber for a predetermined period of time after stopping the application of the RF power.
According to a second aspect of the present invention, there is provided a second plasma processing method as recited in the first method, wherein the step of exposing the substrate to the predetermined gas atmosphere is the step of removing a charge from the substrate in the predetermined gas atmosphere.
According to a third aspect of the present invention, there is provided a third plasma processing method as recited in the first method, wherein the step of exposing the substrate to the predetermined gas atmosphere comprises the step of separating the substrate from the substrate table in the predetermined gas atmosphere.
The inventors of the present invention also consider that when the substrate is separated from the substrate table in a predetermined gas atmosphere, an electrification charge created due to separation of the substrate can be removed, or creation of such a charge can be suppressed or prevented.
According to a fourth aspect of the present invention, there is provided a fourth plasma processing method as recited in the first method, wherein the step of exposing the substrate to the predetermined gas atmosphere is the step of exposing the substrate to the predetermined gas atmosphere for a predetermined period of time in a state in which the substrate is placed on the substrate table within the processing chamber, and
the method further comprises the step of separating the substrate from the substrate table within the processing chamber after the exposing step.
According to a fifth aspect of the present invention, there is provided a fifth plasma processing method as recited in the fourth method, wherein the step of separating the substrate from the substrate table is performed in a second predetermined gas atmosphere.
According to a sixth aspect of the present invention, there is provided a sixth plasma processing method as recited in the fifth method, wherein the second predetermined gas atmosphere consists essentially of the same gas or gases as the predetermined gas atmosphere consists essentially of.
In this case, it is preferred that after the substrate is exposed to a predetermined gas atmosphere for a predetermined period of time while being placed on the substrate table, the substrate is separated from the substrate table in the same gas atmosphere.
According to a seventh aspect of the present invention, there is provided a seventh plasma processing method as recited in any one of the first to sixth methods, wherein the step of exposing the substrate to the predetermined gas atmosphere is the step of exposing the substrate to a predetermined gas atmosphere within the processing chamber for a predetermined period of time immediately after stopping the application of the RF power.
According to a eighth aspect of the present invention, there is provided a eighth plasma processing method
Terasaki Masato
Tsutsuguchi Kazunori
Birch & Stewart Kolasch & Birch, LLP
Kokusai Electric Co. Ltd.
Padgett Marianne
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