Abstract
A knowledge-based understanding of the plasma-surface-interaction with the aim to precisely control (reactive) sputtering processes for the deposition of thin films with tailored and reproducible properties is highly desired for industrial applications. In order to understand the effect of plasma parameter variations on the film properties, a single plasma parameter needs to be varied, while all other process and plasma parameters should remain constant. In this work, we use the Electrical Asymmetry Effect in a multi-frequency capacitively coupled plasma to control the ion energy at the substrate without affecting the ion-to-growth flux ratio by adjusting the relative phase between two consecutive driving harmonics and their voltage amplitudes. Measurements of the ion energy distribution function and ion flux at the substrate by a retarding field energy analyzer combined with the determined deposition rate Rd for a reactive Ar/N2 (8:1) plasma at 0.5 Pa show a possible variation of the mean ion energy at the substrate Emig within a range of 38 and 81 eV that allows the modification of the film characteristics at the grounded electrode, when changing the relative phase shift θ between the applied voltage frequencies, while the ion-to-growth flux ratio Γig/Γgr can be kept constant. AlN thin films are deposited and exhibit an increase in compressive film stress from −5.8 to −8.4 GPa as well as an increase in elastic modulus from 175 to 224 GPa as a function of the mean ion energy. Moreover, a transition from the preferential orientation (002) at low ion energies to the (100), (101) and (110) orientations at higher ion energies is observed. In this way, the effects of the ion energy on the growing film are identified, while other process relevant parameters remain unchanged.
Highlights
Thin film deposition on bulk materials has become an important sector of modern industry to improve and control surface properties of various components [1, 2]
Measurements of the ion energy distribution function and ion flux at the substrate by a retarding field energy analyzer combined with the determined deposition rate Rd for a reactive Ar/N2 (8:1) plasma at 0.5 Pa show a possible variation of the mean ion energy at the substrate Emig within a range of 38 and 81 eV that allows the modification of the film characteristics at the grounded electrode, when changing the relative phase shift θ between the applied voltage frequencies, while the ion-to-growth flux ratio Γig/Γgr can be kept constant
By tuning the relative phase shift, θ, between the two excitation frequencies as an additional process parameter it is possible to adjust the mean ion energy at both electrodes, target and substrate, with a precision of ±1 eV, while the ion flux is nearly constant with only 4% alteration
Summary
Thin film deposition on bulk materials has become an important sector of modern industry to improve and control surface properties of various components [1, 2]. There is a broad domain of applications for high quality films with specific properties, e.g. hard coatings or optical filters. For industrial demands it is highly relevant to precisely control (reactive) sputter processes for the deposition of high-quality, reproducible thin films [11,12,13]. It is essential to investigate these processes with experimental diagnostics and simulations to replace the current empirical approach in industry by a knowledge-based approach resting upon a fundamental understanding of the plasma-surfaceinteraction. The insights into these interactions enable reproducible synthesis of coatings with tailored properties [14, 15]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
