Plasma desmearing apparatus and method

Abstract

The present invention is directed to employing a rectilinear chamber for desmearing in which the two transitional ends are frustopyramidal in configuration. Each frustopyramidal diffusion chamber has a controlled exhaust valve which is piped to the vacuum pump. Gas can be introduced to the diffusion chamber at a point adjacent the exhaust valve and centrally therefrom. Ideally there are an odd number of electrode pairs spaced vertically which generate a primary field, and the further spaced apart pairs generating a secondary field therebetween. Because the chamber is rectilinear, it can be proportioned to accommodate vertically spaced MPWB's in the secondary chamber portions. The method contemplates flowing plasma through a rectangular chamber by positioning the pairs of electrodes in closely spaced relationship to provide a primary field, one of the electrodes of each pair secured to a radio frequency source and the other to ground and then spacing the pairs a sufficient distance to permit the insertion of objects to be desmeared in the secondary field. The flow of plasma is directed to impact the objects and can be from left to right, then right to left thereby reversing the flow, pulsating or steady. In addition, in certain applications where plasma flow from one end to the other is not desired, the gas can be introduced centrally. The central introduction is also desirably employed for purging the rectilinear chamber.