Measurements of plasma ion energy distributions with a submicron retarding field energy analyzer

Abstract

A retarding field energy analyzer has been fabricated using standard Si integrated circuit materials and processing techniques. The analyzer features submicron apertures and micron scale grid/collector separation allowing the measurement of ion energy distributions in situ. The analyzer consists of a shielding grid, an electron repeller grid, and a collector plate. The grids, 1 cm2 in area, are made of 400 nm thick polycrystalline silicon thin films and are supported and insulated from each other by SiO 2. The openings in the grids are nominally 0.75 |J.m in diameter and are self-aligned, thereby minimizing field leakage and optimizing energy resolution. The basic functionality of the analyzer has been demonstrated in inductively coupled argon plasmas and measurements show energy spreads of 3-5 eV, which are consistent with the expected presheath voltage drops, and agree well with measurements made with a differentially pumped, macroscopic ion energy analyzer. Variations in mean ion energy as a function of power and pressure agree with the expected scaling trends. Passivation of the Si surfaces with Ni allows for operation of the analyzer in reactive gas plasmas.