The present invention relates to a plasma processing apparatus.
A plasma processing apparatus having an upper electrode and a lower electrode provided to face opposite each other within an airtight processing chamber is widely employed in semiconductor device manufacturing processes in the related art. Such a plasma processing apparatus adopts a structure that enables a specific type of plasma processing to be executed on a substrate with plasma generated from a process gas supplied into the processing chamber by applying high-frequency power to the upper electrode after placing the substrate on the lower electrode.
In addition, an evacuation ring is mounted around the periphery of the lower electrode between the side surface of the lower electrode and the inner wall surface of a processing container, and this evacuation ring divides the space within the processing container into a processing space where the substrate is placed and an evacuation path which communicates with an evacuating mechanism. A plurality of through holes are formed at the evacuation ring, and the processing space and the evacuation path are made to communicate with each other through these through holes. Thus, since the gas within the processing space is guided into the evacuation path via the through holes during the process, the conductance within the processing space and the evacuation path is sustained in a specific state, thereby enabling stable evacuation of the processing space. The plasma is trapped inside the processing space, and a ground area is assured by the inner wall surface of the processing container and the evacuation ring, whose potentials are held at the ground potential level.
However, the evacuation ring, which is constituted of a metal such as an aluminum alloy so as to sustain its potential at the ground potential level, is bound to be damaged by the plasma generated within the processing container. In addition, if a sufficiently large ground area is not assured, an abnormal discharge tends to occur due to an uneven distribution of the plasma inside the processing container or the like. The stability in the electrical discharge is disrupted by such an abnormal discharge and, furthermore, the abnormal discharge causes damage to the substrate, resulting in lowered yield. Moreover, the abnormal discharge damages the inner wall of the processing chamber and the evacuation ring as well.
An object of the present invention, which has been completed by addressing the problems discussed above, is to provide a plasma processing apparatus having an evacuation ring with high plasma resistance and capable of minimizing occurrence of abnormal discharge.