ISO 22278:2020

Overview

ISO 22278:2020 defines a standardized test method for evaluating the crystalline quality of single‑crystal thin films (wafers) using the X‑ray diffraction (XRD) method with a parallel X‑ray beam. Applicable to both bulk and epitaxial layer structures, the standard provides procedures to reduce measurement variability and produce reproducible results for wide‑area wafers used in advanced ceramics and semiconductor substrates.

Key Topics

• Scope and purpose: Standardizes measurement conditions and procedures for crystalline quality assessment to minimize user‑dependent errors.
• Fundamentals: Principles of Bragg diffraction, rocking curves (RC) and how crystal defects (dislocations, mosaic spread, curvature, misorientation, inhomogeneity) broaden diffraction peaks.
• Instrumentation and setup: Requirements and schematic configuration for XRD systems with parallel X‑ray beams, including X‑ray generator, X‑ray mirror, monochromator, slits, goniometer, detector and calibration procedures.
• Sample preparation: Guidance on sample attachment, flat zone selection, and surface conditioning (e.g., CMP) to ensure accurate measurement.
• Test procedures: Step‑by‑step methods for optics alignment, sample alignment, initial goniometer positioning, symmetric and asymmetric diffraction, microscopic adjustments (Φ, χ axes) and ω scans.
• Measurement metrics: Use of rocking curve full width at half maximum (FWHM) as the primary indicator of crystalline quality and procedures to measure FWHM reliably.
• Data analysis and reporting: Recommended analysis steps, interference considerations (wafer curvature, doped epitaxy), and required elements for the test report.
• Annexes: Informative examples and interlaboratory test results to aid implementation.

Applications and Practical Value

• Quality control and acceptance testing for single‑crystal substrates used in high‑power and high‑frequency devices (e.g., SiC, GaN).
• Process monitoring during epitaxial growth and substrate manufacturing to detect and quantify crystal defects.
• R&D and materials characterization in advanced ceramics, optoelectronics, laser host materials and piezoelectric single crystals.
• Metrology labs seeking reproducible, standardized XRD rocking curve measurements for wafer benchmarking.

Who Should Use This Standard

• Substrate and wafer manufacturers, materials scientists, process engineers, metrology laboratories, and quality assurance teams in semiconductor, power electronics and fine‑ceramics industries.

Related Standards

ISO 22278:2020 was prepared by ISO/TC 206 (Fine ceramics). For a complete conformity and cross‑reference picture, consult your national ISO member body or the ISO Online Browsing Platform for related XRD and semiconductor substrate standards.