- SEMI MF1366 - Test Method for Measuring Oxygen Concentration in Heavily Doped Silicon Substrates by Secondary Ion Mass Spectrometry
The presence of oxygen can be beneficial to certain manufacturing operations by preventing the formation of process-induced defects. Oxygen is introduced into silicon wafers during the crystal growing process. Hence, it is very important to control the oxygen content of silicon crystals.
Secondary ion mass spectrometry (SIMS) can measure the oxygen concentration in heavily-doped silicon substrates used for epitaxial silicon where the free carrier concentration obscures the infrared absorption and prevents the normal use of the infrared measurement as a characterization technique for the commercial production of silicon.
The SIMS measurement allows for the production of controlled oxygen content in heavily-doped silicon crystals.
This Test Method can be used for process control, research and development, and materials acceptance purposes.
This Test Method covers the determination of total oxygen concentration in the bulk of single crystal silicon substrates using SIMS.
This Test Method can be used for silicon in which the dopant concentrations are less than 0.2% (1 × 1020 atoms/cm3) for boron, antimony, arsenic, and phosphorus (see SEMI MF723). This Test Method is especially applicable for silicon that has resistivity between 0.0012 and 1 W × cm for p-type silicon and between 0.008 and 0.2 W × cm for n-type silicon (see SEMI MF43).
This Test Method can be used for silicon in which the oxygen content is greater than the SIMS instrumental oxygen background as measured in a float zone silicon sample, but the test method has a useful precision especially when the oxygen content is much greater (approximately 10× to 20×) than the measured oxygen background in the float zone silicon.
This Test Method is complementary to infrared absorption spectroscopy that can be used for the measurement of interstitial oxygen in silicon that has resistivity greater than 1 W × cm for p-type silicon and greater than 0.1 W × cm for n-type silicon (see SEMI MF1188). The infrared absorption measurement can be extended to between 0.02 and 0.1 W × cm for n-type silicon with minor changes in the measurement procedure.
In principle, different sample surfaces can be used, but the precision estimate was taken from data on chemical-mechanical polished surfaces.
Referenced SEMI Standards
SEMI M59 — Terminology for Silicon Technology
SEMI MF43 — Test Method for Resistivity of Semiconductor Materials
SEMI MF723 — Practice for Conversion between Resistivity and Dopant Density for Arsenic-Doped, Boron-Doped, and Phosphorus-Doped Silicon