Cylindrical Gas Diffuser
Original Publication Date: 1984-Jul-01
Included in the Prior Art Database: 2005-Feb-04
In a plasma chemical vapor deposition (CVD) or reactive ion etch (RIE) system, the process gas is emitted through a flat screen at the center 1 of the wafer platen 2, at a fairly high velocity towards the top electrode 3. The gas rebounds off the electrode resulting in a rather turbulent flow pattern, as shown in Fig. 1. Because of the direction of the inlet gas 4, a large build-up of deposits occurs near the center of the top electrode. The heavier deposits would tend to flake off as particulates. The gas flow distribution can be further affected by the angle of incidence of the gas stream on the electrode, which in turn affects the thickness distribution of the film deposits. Large thickness variations may occur from even a small tilt between the wafer platen and the electrode. The new inlet gas diffuser (Fig.