Patent ID: 7494560

Claim:
An apparatus comprising: a chamber adapted for holding a workpiece having a surface layer adapted for being etched; a distribution plate including I rings within the distribution plate and around a common point on the distribution plate such that no other ring exists within the distribution plate, wherein each ring of the I rings is formed within a corresponding groove in the distribution plate such that each ring is the only ring within its corresponding groove; wherein I is an integer of at least 2, wherein the I rings are denoted as R 1 , R 2 , . . . , R I in order of increasing distance from the common point and consist of I 1 rings of a first type and I 2 rings of a second type such that I 1 is at least 1, I 2 is at least 1, and I 1 +I 2 =I, wherein the I rings collectively comprise N channels and no other channels such that each ring of the I rings comprises at least 2 channels of the N channels and no other channels, wherein a flow inlet of each channel of the at least 2 channels of each ring are positioned at a same constant distance from the common point, wherein N is at least 2*I, wherein the N channels consist of N 1 channels of a first kind within the I 1 rings of the first type and N 2 channels of a second kind within the I 2 rings of the second type such that N 1 +N 2 =N, wherein each channel of the N 1 channels of a first kind is oriented at a same constant angle θ 1 with respect to an exposed surface of the distribution plate and provides a first fluid to flow into the chamber at the same constant angle θ 1 with respect to the exposed surface of the distribution plate, wherein each channel of the N 2 channels of the second kind is oriented at a same constant angle θ 2 with respect to the exposed surface of the distribution plate and provides a second fluid to flow into the chamber at the same constant angle θ 2 with respect to the exposed surface of the distribution plate, wherein θ 1 and θ 2 are each at least 45 degrees and less than 90 degrees, wherein θ 1 is unequal to θ 2 , and wherein the first fluid differs from the second fluid; a first fluid feed line connected to a source of the first fluid, wherein the first fluid feed line is fluidically coupled to the N 1 channels of the first kind for providing the first fluid to the N 1 channels of the first kind, and wherein the first fluid feed line is not fluidically coupled to the N 2 channels of the second kind and cannot provide the first fluid to the N 2 channels of the second kind; and a second fluid feed line connected to a source of the second fluid and to be fluidically coupled to the N 2 channels of the second kind so as to provide the second fluid to the N 2 channels of the second kind, and wherein the second fluid feed line is not fluidically coupled to the N 1 channels of the first kind and cannot provide the second fluid to the N 1 channels of the first kind.