Overview
ISO 12406:2010 specifies a standardized secondary‑ion mass spectrometry (SIMS) method for quantitative depth profiling of arsenic in silicon. It covers SIMS measurement using magnetic‑sector or quadrupole mass spectrometers and requires depth calibration by stylus profilometry or optical interferometry. The method applies to single‑crystal, polycrystalline or amorphous silicon with arsenic atomic concentrations from 1 × 10^16 to 2.5 × 10^21 atoms/cm^3 and to sputter crater depths of 50 nm or deeper.
Key topics and requirements
- Instrumentation: Use of magnetic‑sector or quadrupole SIMS systems; caesium (Cs+) or oxygen (O2+) primary ion beams; detection of appropriate As and Si secondary‑ion species.
- Depth calibration: Crater depth must be measured by stylus profilometry or optical interferometry (note: optical interferometry is generally applicable in the ~0.2 µm to 5 µm range).
- Concentration calibration: Use certified reference materials (CRMs) or traceable ion‑implanted materials to determine relative‑sensitivity factors (RSFs). At publication, available CRMs included NIST SRM 2134 and NMIJ CRM 5603‑a.
- Measurement practice: Optimize primary‑ion current and scan area to avoid detector saturation (pulse pile‑up); alternate arsenic and silicon ion measurements cyclically; maintain instrument stability and consistent transmission settings between reference and test measurements.
- Quality controls: Follow documented instrument alignment and vacuum practices to minimize interfering background signals (e.g., SiOx species), and use traceable depth standards for profilometer calibration.
Practical applications
- Semiconductor process control and failure analysis for arsenic‑doped silicon devices.
- Implant dose verification and dopant profiling in research and production wafers.
- Metrology and calibration labs performing absolute concentration and depth‑scale verification for SIMS instruments.
- Materials science studies of dopant diffusion, junction depth, and implantation profiles in silicon substrates.
Who should use this standard
- SIMS laboratory managers and operators in semiconductor fabs and contract analytical labs.
- Instrument manufacturers, calibration laboratories and national metrology institutes.
- Quality assurance engineers and R&D teams requiring traceable arsenic depth profiles and standardized reporting.
Related standards
Keywords: ISO 12406:2010, SIMS depth profiling, arsenic in silicon, secondary‑ion mass spectrometry, depth calibration, stylus profilometry, optical interferometry, NIST SRM 2134, RSF.