Measurement of ion energy distributions at the powered rf electrode in a variable magnetic field

Abstract

High-resolution energy distributions of ions, accelerated by the sheath at the powered electrode of a low-pressure 13.56-MHz gas discharge, have been measured. The observed spectra are compared to existing models. Excellent agreement between measured and calculated spectra is obtained. Detailed information on rf sheath behavior is derived from the observed energy profiles and from the measured total ion current densities towards the electrode surface. Analogous to the case of dc discharges, a decrease of sheath thickness is observed when a homogeneous variable magnetic field (0≤B≤315 G) is applied. However, the product of magnetic-field strength B and sheath thickness d is found to be independent of sheath voltage. This leads to the conclusion that in rf discharges, sheath contraction under influence of a magnetic field proceeds by a different mechanism than in dc discharges. It is suggested that the value of the product Bd is determined by the (virtually constant) temperature of the plasma electrons, rather than by the energy of secondary electrons that have been liberated from the electrode surface by ion bombardment. The decrease of sheath thickness d with magnetic-field strength B leads to a changing capacitive-voltage division of the applied generator voltage over the discharge. When the magnetic-field strength is sufficiently high, this may result in a sign reversal of the electrode self-bias voltage.

Influence of target power on properties of CuxO thin films prepared by reactive radio frequency magnetron sputtering

“…In deposition by sputtering, the stoichiometry of Cu 2 O is retained by the ratio of the partial pressure of the reactive gas over the flux of Ar, Φ(Ar), that erodes the target surface [12]. At a fixed Q(Ar) inlet, Φ(Ar) depends on the sheath potential/target potential [15], which is correlated to the target power [16]. Once the partial pressure of Ar and O 2 are set, the flux of the non-reactive gas and consequently the balance of Cu versus O atoms accumulated on the substrate will be controlled by the target power during the reactive sputtering process.…”

Investigating the plasma parameters of an Ar/O2 discharge during the sputtering of Al targets in an inverted cylindrical magnetron

“…7-10 Cook and Donohoe 11 suggested that methods must be developed to control the energies and ion fluxes of species in discharges for the benefit of future semiconductor devices, due to the effect energetic species have on the nature of materials when they are bombarded by such species. To understand the role of plasma species in a discharge, theoretical [12][13][14] and experimental [15][16][17][18][19] studies of the Ion Energy Distribution (IED) of particles in a deposition discharge have been under taken and reported. However, most of these studies focused on Ar þ ions since argon is generally the gas used in sputtering discharges and also because of the relative simplicity of its chemical kinetics in such plasmas.…”

Simulation of plasma processes for microelectronic fabrication

“…5. The experimental date (curves b) were taken from Kuypers et al [3]; the calculated distribution functions (curves a) were folded with a Gaussian of 3 eV standard deviation, in order to represent the limited energy resolution of the mass spectrometer.…”