Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
1998-10-14
2001-11-06
McDonald, Rodney G. (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S298250, C204S298310, C204S298340, C204S298350, C156S345420, C118S715000, C118S7230ER, C118S7230ER, C134S001100
Reexamination Certificate
active
06312569
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to methods of cleaning semiconductor production equipment, and relates in particular to a cleaning method for a chemical vapor deposition chamber for depositing a thin film of a ferroelectric or highly dielectric material, such as barium/strontium titanate, on a semiconductor substrate.
2. Description of the Related Art
In recent years, there has been a quantum jump in circuit density of integrated circuit devices produced by the semiconductor industries, and intense development activities are underway in anticipation of giga-bit order DRAMs replacing the prevailing mega-bit order DRAMs of today. Dielectric thin film materials used to make high capacitance devices necessary for producing DRAMs have, in the past, included silicon oxide or silicon nitride films of dielectric constant less than ten, tantalum pentaoxide (Ta
2
O
5
) films of dielectric constant of about twenty; metal oxide films of dielectric constant of about three hundred, such as barium titanate (BaTiO
3
) or strontium titanate (SrTiO
3
) films, or barium/strontium titanate films of a mixed composition, appear to be promising.
To deposit a thin film of such a high dielectric constant material on a substrate, a chemical vapor deposition apparatus is used in which one or more gaseous feeds of organo-metallic compounds and an oxygen containing gas are supplied onto a substrate heated to a certain constant temperature.
In such an apparatus, reaction products produced during the film deposition process are adhered to the inside surfaces of the deposition chamber, causing problems of degradation in product quality and hindering of the process of stable deposition. It is therefore necessary to periodically remove (clean) such reaction products accumulated inside the chamber. Cleaning operation has traditionally been performed by opening and exposing the apparatus to air atmosphere, and cleaning the apparatus physically or chemically.
However, cleaning in air atmosphere means that the apparatus must be shut down to break the vacuum inside the chamber, and restarted to restore deposition conditions, so that the process is not only time-consuming but results in loss of operating efficiency.
A cleaning method based on plasma etching using a halogen gas has also been proposed for silicon oxide deposition apparatus. A plasma is generated in the deposition chamber by introducing a halogen gas (e.g. SF
6
) into the chamber for producing halogen radicals to react with the reaction products adhering to the inside wall of the chamber, thereby to produce gaseous halogen compounds which will be easily exhausted by a subsequent evacuation process.
However, such a cleaning method based on plasma etching cannot be applied to deposition apparatus for making high capacity memories made of highly dielectric thin film materials, because the resulting halogen compounds are not volatile, and therefore the reaction products are left unaffected in the deposition chamber.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a chemical vapor deposition apparatus for depositing a thin film of highly dielectric materials for giga-capacity memory devices which can be reliably cleaned of reaction products formed within the deposition chamber without sacrificing the production efficiency, and an associated method of cleaning the apparatus.
The object has been achieved in a chemical vapor deposition apparatus comprising: a hermetic deposition chamber containing a substrate holding section for supporting a substrate; a gas supply head disposed opposite to the substrate holding section for directing a gaseous feed material onto the substrate; a trapping member supporting device for supporting a trapping member so as to be opposite to a target cleaning area inside the deposition chamber; and a plasma generation device for generating a plasma between the target cleaning area and the trapping member supported by the trapping member supporting device. Accordingly, reaction products accumulated in certain inner areas of the deposition chamber are dislodged by ionic sputtering caused by ions in the plasma and are captured by the trapping member which is removed from the deposition chamber after the cleaning process is completed. The trapping member supporting device may be installed inside the deposition chamber or may be introduced when cleaning is required.
The trapping member supporting device may comprise a supporting member provided in the deposition chamber. Otherwise, the supporting member may be insertable into and retractable from the deposition chamber with the trapping member carried thereon.
The trapping member may be electrically conductive, and the trapping member supporting device is provided with plasma electrodes, in electrical contact with the trapping member, for generating a plasma. Accordingly, a plasma is generated selectively between a target cleaning area and the trapping member. A plasma gas may be introduced through the gas supply head.
An electrode cover member is provided for the apparatus for preventing reaction products from depositing on the plasma electrodes. By protecting the plasma electrodes with the electrode cover member during a film deposition process, deposition of reaction products on the surfaces of electrodes can be prevented to maintain good electrical conduction.
In any of the foregoing apparatus arrangements, trap transporting means are provided so that the trapping member can be loaded into or unloaded from the deposition chamber while maintaining hermetic sealing of the deposition chamber. Such an arrangement permits the inside of the deposition chamber to be cleaned without losing the vacuum in the apparatus. This process can be carried out by connecting an auxiliary chamber adjacent to the deposition chamber through a gating valve so that the trapping member can be transported in and out of the deposition chamber by means of a robotic arm or other suitable means.
Reaction products accumulated in the deposition apparatus are cleaned out by a method for cleaning reaction products accumulated on inner surfaces of a chemical vapor deposition apparatus, comprising: placing a trapping member inside the deposition chamber; generating a plasma between the trapping member and a target cleaning area inside the deposition chamber; dislodging reaction products from the target cleaning area by ionic sputtering and capturing the sputtered particles on the trapping member; and removing a used trapping member out of the deposition chamber.
In the method, a target cleaning area is selected by varying a distance between the trapping member and the target cleaning area in the deposition chamber. For example, a device for elevating the substrate stage is a usual component in any chemical vapor deposition apparatus. Therefore, this device can be used to select a cleaning area to be either the top surface of the substrate stage or the lower surface of the gas supply head.
As explained above, the present invention provides an apparatus and an associated method of cleaning a chemical vapor deposition apparatus for producing giga-capacity memory devices, by dislodging the reaction products accumulated in critical operating parts of the apparatus with plasma ion sputtering, and capturing the released particles on the trapping member for removal from the deposition chamber without sacrificing the vacuum atmosphere, thereby enabling the apparatus to be reliably cleaned without losing the production efficiency.
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patent: 5298720 (1994-03-01), Cuomo et al.
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Abe Masahito
Nakada Tsutomu
Saitoh Masao
Suzuki Hidenao
Ebara Corporation
McDonald Rodney G.
Wenderoth , Lind & Ponack, L.L.P.
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