Epitaxial layer thickness measurement by far infrared ellipsometry.

Area of Science:

• Semiconductor Physics
• Optical Metrology

Background:

• Accurate measurement of silicon epitaxial layer thickness is crucial for semiconductor device fabrication.
• Existing metrology techniques may have limitations for both thin and thick layers.

Purpose of the Study:

• To develop and validate a far-infrared (far-IR) ellipsometer for precise thickness measurements of silicon epitaxial layers.
• To assess the capability of the developed technique for analyzing both thin (<3-microm) and thick (>3-microm) layers.
• To explore the combined use of far-IR ellipsometry and near-IR interference for junction grading analysis.

Main Methods:

• Development of a novel ellipsometer system operating at a far-IR wavelength of 118.6 micrometers.
• Application of the ellipsometer to measure the thickness of n-type silicon epitaxial layers on heavily doped n-type silicon substrates.
• Integration of far-IR ellipsometry with near-IR interference measurements.

Main Results:

• The far-IR ellipsometer demonstrated accurate thickness measurements for both thin and thick silicon epitaxial layers.
• The technique proved effective for n-type silicon on n-type substrates.
• Combined measurements provided insights into the junction grading characteristics.

Conclusions:

• Far-infrared ellipsometry is a viable and accurate method for silicon epitaxial layer thickness determination.
• The developed system offers a valuable tool for semiconductor metrology.
• The integration with near-IR interference enhances the analytical capabilities for semiconductor structures.