Investigation of target erosion profiles sputter-eroded by a low-energy broad ion beam

Wjatscheslaw Sakiew,Detlev Ristau,Eileen Klocke

doi:10.1063/6.0000909

Abstract

The demand for ion beam sputtering (IBS) coated substrates is growing. In order to find new fields of application for IBS coating technology, it is necessary to understand in detail the distributions of the involved particles in an industrial-scale reactive coating process. In pursuit of this goal, in the present investigation, profiles sputter-eroded from tantalum, silicon, and silicon dioxide targets by a low-energy broad ion beam (ion energy ≤ 1.9 keV, ion source RIM-20) are measured with a mechanical profilometer and compared. To approximate the discrete and two-dimensional erosion data accurately, an empirical function is developed. For an applied target tilt angle of 55°, the results indicate that the actual angle-dependent ion–solid interaction mechanisms at the atomic level have a rather subordinate role in the macroscopic surface modification of the target in terms of the qualitative distribution of the erosion profile. The applied process geometry seems to have a much larger impact. Furthermore, in the case of silicon, a linear erosion rate as a function of erosion time is observed. Thus, the form of the broad erosion profile does not seem to have a measurable effect on the erosion rate.

Highlights

Ion beam sputter deposition (IBSD) is a well-established coating technology in optical thin film production facilities
It is to be expected that larger coatings with an IBSD quality level will be required for future applications, e.g., meter-sized optical coatings for astronomy and space applications or meter-sized high-power laser optics for large optical systems
The ions are extracted from the plasma and accelerated by 847 beamlets distributed in a quasi-hexagonal pattern

Summary

Introduction

Ion beam sputter deposition (IBSD) is a well-established coating technology in optical thin film production facilities. The properties, applications, and achievable quality parameters have been welldocumented in open literature.. Mirror coatings for gravitational wave detectors and ring laser gyroscopes for inertial rotation measurements are prominent scientific applications. The productivity parameters and economic factors involved have not received much attention. It is only in the last few years that a certain trend toward large-area optical coatings in the field of IBSD has been observed. It is to be expected that larger coatings with an IBSD quality level will be required for future applications, e.g., meter-sized optical coatings for astronomy and space applications or meter-sized high-power laser optics for large optical systems. The achievable uniform deposition areas are still smaller than 1 m in diameter. it is to be expected that larger coatings with an IBSD quality level will be required for future applications, e.g., meter-sized optical coatings for astronomy and space applications or meter-sized high-power laser optics for large optical systems.

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