Ion energy determination for r.f. plasma and ion beam using a multigrid retarding field analyser

Abstract

The ion energy distribution of a capacitively coupled r.f. (13.56 MHz) plasma and ion beam source has been measured. The extraction optics consists of two stainless steel grids. The source has been operated in two different configurations, either with or without extraction optics. In the latter case the discharge serves only as a plasma source to be used directly or as remote plasma. For measurements of ion energy in the plasma mode a four-grid retarding field analyser (RFA) was used. For analysis of ion energy in the ion beam mode a slightly different RFA was used, because the retarding voltage here is higher, corresponding to extraction voltages of several hundred volts. In the plasma mode, all distributions exhibit a single-peak structure with a low-energy tail. With increasing pressure from 4 × 10 −2 to 4 Pa the distribution width shows an increase from 1.5 to 4.5 eV, whereas the average ion energy decreases from 48 to 17.4 eV. In the ion beam mode, the ion energy distribution is studied as a function of the r.f. power and pressure.