Overview
ISO 16531:2020 - Surface chemical analysis - Depth profiling - Methods for ion beam alignment and the associated measurement of current or current density for depth profiling in AES and XPS - specifies practical procedures to align ion beams and measure ion current or current density for sputter depth profiling in Auger electron spectroscopy (AES) and X‑ray photoelectron spectroscopy (XPS). The standard covers methods suitable for ion guns with beam spot sizes ≤ 1 mm and describes two main approaches: Faraday cup current measurements and imaging-based alignment. It does not prescribe depth resolution optimization but provides a faster, routine check to ensure the ion beam is centered and uniform before detailed depth-resolution assessments.
Key Topics and Requirements
- Scope and applicability
- Focusable inert-gas ion guns commonly used for AES/XPS sputtering.
- Beam spot or raster area larger than the analysis area; applicable for beams ≤ 1 mm diameter.
- Two method types
- Faraday cup methods: circular- and elliptical-aperture Faraday cups for measuring ion current, current density and current distributions; Annex B discusses co‑axial electrode measurements.
- Imaging methods: detection of ion-induced secondary electrons, photoelectron/imaging systems, direct observation of ion beam spots or sputter craters, and phosphor screen luminescence.
- System requirements
- Electron energy analyser and analytical probe beam must already be aligned to the analysis position.
- Instrumentation must permit ion current detection or imaging (secondary electron detector, optical microscope, phosphor screen).
- Practical considerations
- Methods describe when alignment is needed (e.g., after filament change or bake‑out).
- Guidance on selecting methods based on equipment capability and raster size.
- Limitations noted: does not cover specialized sputtering procedures (grazing incidence, dual guns, sample rotation) though it supports standard fixed‑angle profiling workflows.
- Supplementary content
- Annex A: examples comparing AES profiles with good/poor alignment.
- Annex B: co‑axial cup method.
Applications and Who Uses ISO 16531:2020
- Surface analysis laboratories performing AES and XPS depth profiling.
- Materials scientists and engineers characterizing thin films, coatings, multilayers and semiconductor stacks.
- QA/QC teams in microelectronics and thin‑film manufacturing needing reproducible sputter rates and uniform cleaning.
- Instrument vendors and service engineers validating ion gun performance and providing routine maintenance checks.
Related Standards (if applicable)
- ISO 14606 - procedures for measuring depth resolution in sputter profiling (more detailed, time‑consuming evaluation).
- ISO 18115‑1 - vocabulary for surface chemical analysis (terms used in ISO 16531:2020).
Keywords: ISO 16531:2020, ion beam alignment, depth profiling, AES, XPS, Faraday cup, ion current density, sputter depth profiling, surface chemical analysis.