Patent ID: 9087677
Filing Date: 2015-07-21
Classification: H01J,H05H,Y10T

Abstract:
1. A method of generating a signal with an ion energy analyzer for use in determining an ion energy distribution of a plasma, the ion energy analyzer comprising: a first grid forming a first surface of the ion energy analyzer positioned to be exposed to the plasma at a reference voltage when the ion energy analyzer is positioned in a plasma processing apparatus, the first grid including a first plurality of openings, each of the openings of the first plurality having a dimension that is less than a Debye length for the plasma such that the plasma sheath does not penetrate openings of the first plurality; an ion collector forming a second surface of the ion energy analyzer; a first voltage source operably coupled to the ion collector; a second grid positioned between the first grid and the ion collector and electrically isolated from the first grid; a second voltage source operably coupled to the second grid; an ion current meter operably coupled to the second grid; a first insulator positioned between the first grid and the second grid, wherein a geometry of the first insulator is selected to project, from outside of a respective channel between the first grid and the second grid, inwardly toward and orthogonal to a center axis of the ion energy analyzer such that no straight line path that is parallel to the optic axis exists between any two points on the first grid and the second grid, respectively, from a set of all possible paths extending along a surface of the first insulator; and a second insulator positioned between the second grid and the ion collector, wherein a geometry of the second insulator is selected to project, from outside of a respective channel between the second grid and the ion collector, inwardly toward and orthogonal to the center axis of the ion energy analyzer such that no straight line path that is parallel to the optic axis exists between any two points on the second grid and the ion collector grid, respectively, from a set of all possible paths extending along a surface of the second insulator; the method comprising: preventing plasma from penetrating the first grid with the first plurality of openings; selectively and variably biasing the ion collector relative to the first grid with the first voltage source; selectively and variably biasing the second grid relative to the first grid with the second voltage source; with the selected geometry of the first insulator, electrically isolating the first grid from the second grid and reducing or preventing electrical breakdown therebetween; with the selected geometry of the second insulator, electrically isolating the second grid from the ion collector and reducing or preventing electrical breakdown therebetween; measuring an ion current flow at the ion collector with the ion current meter; and transmitting a signal representing the measured ion current flow.