PLASMA UNIFORMITY CONTROL BY GAS DIFFUSER HOLE DESIGN

摘要

A uniform plasma control by a gas diffusion hole structure is provided to control uniformly the thickness and characteristic of a layer over an entire substrate by forming a thin film on the substrate by a PECVD method. A diffusion plate member has an upstream part and a downstream part. Inner and outer gas paths(262) pass through a gap between the upstream and the downstream parts in the diffusion plate member. Each gas path includes an orifice hole and a hollow cathode cavity. The orifice hole has a length and a diameter to promote the uniform distribution of gas passing through the upstream part. The hollow cathode cavity is a downstream of the orifice hole, positioned in the downstream part. The hollow cathode cavity is of a cone shape or a cylindrical shape. With respect to the cones or cylinder, the diameter, depth or a composition of the diameter and the depth increases as it goes from the center of the diffusion plate member to the edge of the diffusion plate member. The size of the hollow cathode cavity of the inner gas paths is smaller than that of the hollow cathode cavity of the outer gas paths. The diffusion plate member can be a rectangular shape. The gas paths can promote a uniform flow of gas passing through the gas paths.