1. Field of Invention
The present invention relates to an apparatus for inductively coupled plasma chemical vapor deposition (ICP CVD), and more particularly to an ICP CVD apparatus for preventing pollution of impurities from a dielectric shield constituting, in part, a reaction chamber.
2. Related Art
The laid-opened publication of Japanese Patent Application (No. 95-60704) discloses an ICP CVD apparatus capable of forming a thin film. The above ICP CVD apparatus includes: a ring shaped antenna where a radio frequency (RF) power is applied; a dielectric shield disposed adjacent to the antenna; a chamber having the dielectric shield, capable of maintaining an air-tight seal; a stage disposed within the chamber for heating a work piece to be processed; a gas supply unit for supplying at least two or more reactant gases in predetermined quantities to the chamber; and an exhaust unit for exhausting the remnant gases inside the chamber.
The above ICP CVD apparatus operates as follows. If, radio frequency power is applied to the ring shaped antenna, plasma is induced on the opposite side of the dielectric shield, that is, the inside of the chamber. The dielectric shield is made of quartz and is disposed adjacent to the antenna. The stage is arranged in the inside of the chamber, and the work piece, that is loaded onto the stage, is heated. The exhaust unit exhausts the remnant gases inside the chamber, leaving a vacuum. The gas supply unit then supplies at least two or more gases in predetermined quantities to the chamber.
In the ICP CVD apparatus, however, the dielectric shield is made of material containing oxygen, such as quartz. Accordingly, there is a disadvantage in that oxygen or impurities dissociate from the dielectric shield to adversely affect film quality.
Furthermore, in the above ICP CVD apparatus, because an inlet port of the gas supply unit is disposed at the side portion and not the central portion of the vacuum reaction chamber, the gas is not uniformly spread over a large area so that an uniform plasma of high density is not induced.