Determination of flux ionization fraction using a quartz crystal microbalance and a gridded energy analyzer in an ionized magnetron sputtering system

Abstract

A diagnostic which combines a quartz crystal microbalance ͑QCM͒ and a gridded energy analyzer has been developed to measure the metal flux ionization fraction in a modified commercial dc magnetron sputtering device. The sensor is mounted on a linear motion feedthrough and embedded in a slot in the substrate plane to allow for measuring the uniformity in deposition and ionization throughout the plane of the wafer. Radio-frequency ͑rf͒ power is introduced through a coil to ionize the Al atoms. The metal flux ionization fraction at the QCM is determined by comparing the total deposition rate with and without a bias that screens out the ions, but that leaves the plasma undisturbed. By varying the voltage applied to the grids, the plasma potential is determined. At a pressure of 35 mTorr, a magnetron power of 2 kW, and a net rf power of 310Ϯ5 W, 78Ϯ5% ionization was found.

The Effect of Magnetic Field Strength and Geometry on the Deposition Rate and Ionized Flux Fraction in the HiPIMS Discharge

“…The total error of F flux was estimated to be up to 15% for a single result mainly based on the accuracy of the mass deposition rate determination. Since the QCM electrode was grounded during the measurement of the total deposition rate, no significant collimation of the ions [35] was expected at this stage due to the low plasma potential, which potentially could introduce additional errors in the measurements. The ion meter was mounted on the probe holder shown in Figure 1 and could thereby map out the same region of interest as the standard QCM.…”

Downstream plasma transport and metal ionization in a high-powered pulsed-plasma magnetron

“…This originates from the consideration that for the non-directional neutral flux, the ceramic casing will shadow part of the neutrals from reaching the QCM sensor while there is no shadowing effect for directional ion flux. A more specific description on the calculation of G was done by Green et al 34 For the current GEA setup, G ¼ 0.42 will be used in the calculation assuming an isotropic distribution of neutrals…”

“…Meanwhile, the Cu ion fractions in the deposition fluxes were measured using a gridded energy analyzer (GEA) combined with a quartz crystal microbalance (QCM). 34 Theoretical calculations are performed to understand the ion extraction process. In the calculations, the diffusion process of sputtered Cu flux towards the substrate is considered, the mapped n e and T e data are used to find ionizing probability, the ion extraction efficiency is determined based on the plasma potential (V p ) distribution.…”

Development and characterization of a secondary RF plasma-assisted closed-field dual magnetron sputtering system for optical coatings on large-area substrates

“…The bottom grid, which acts as the ion repeller, was applied with an adjustable potential. When it was negatively biased (−10 V), the total flux of ions and neutrals ψ tot was recorded by QCM [15].When a positive bias was applied to the grid and gradually increased up to 50 V, only neutral flux ψ N reached the QCM. The ion and neutral flux were further used to determine the ionization fraction of the metal flux.…”