Standard Test Method for Measuring Surface Sodium, Aluminum, Potassium, and Iron on Silicon and EPI Substrates by Secondary Ion Mass Spectrometry
|Publication Date:||10 May 1998|
|ICS Code (Chemical analysis of metals):||77.040.30|
This test method covers the determination of total sodium, aluminum, potassium, and iron on the surface of mirror-polished single crystal silicon and silicon epi substrates using secondary ion mass spectrometry (SIMS). This test method measures the total amount of each metal, because this test method is independent of the metal's chemistry or electrical activity.
This test method can be used for silicon with all dopant species and dopant concentrations.
This test method is especially designed to be used for surface metal contamination that is located within approximately 5 nm of the surface of the wafer.
This test method is especially useful for determining the surface metal areal densities in the native oxide or chemically grown oxide of polished silicon substrates after cleaning.
This test method is useful for sodium, aluminum, potassium, and iron areal densities between 10 9 and 10 14 atoms/cm². The limit of detection is determined by either the BLANK value or by count rate limitations, and may vary with instrumentation.
This test method is complementary to:
Total reflection X-ray fluorescence (TXRF), that can detect higher atomic number Z, surface metals such as iron, but does not have useful (<10 11 atoms/cm²) detection limits for sodium, potassium, and aluminum on silicon.
Electron spectroscopy for chemical analysis and Auger electron spectroscopy that can detect metal surface areal densities down to the order of 10 12 to 10 13 atoms/cm².
Vapor phase decomposition (VPD) of surface metals followed by atomic absorption spectroscopy (AAS) or inductively coupled plasma mass spectrometry (ICP-MS) of the VPD residue, where the metal detection limits are 10 8 to 10 10 atoms/cm². There is no spatial information available and the VPD preconcentration of metals is dependent upon the chemistry of each metal.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.