Application of light scattering tomography for Si(111) samples

Area of Science:

• Materials Science
• Semiconductor Manufacturing
• Optical Metrology

Background:

• Bulk micro-defect detection in Czochralski-grown silicon (Si) wafers is crucial for quality control.
• Light Scattering Tomography (LST) is an industry-standard optical non-contact metrology for defect detection.
• Standard LST requires sample cleavage, which is perpendicular for Si (100) but not for Si (111) wafers.

Purpose of the Study:

• To present a modified Light Scattering Tomography (LST) system capable of measuring defects in Si (111) wafers.
• To detail the design and measurement capabilities of the modified LST system.
• To validate the new technique by comparing results with standard LST measurements.

Main Methods:

• Modification of a standard LST system by tilting the detection unit.
• Cleaving Si (100) and Si (111) wafers for sample preparation.
• Performing defect detection measurements on Si (111) wafers using the modified LST system.

Main Results:

• The modified LST system successfully enables defect detection in Si (111) wafers.
• The cleavage angle of 70.5° for Si (111) wafers, which prevents standard LST measurement, is overcome by tilting the detector.
• Measurement results from the modified system are validated against standard LST on Si (100) samples.

Conclusions:

• A modified LST system with a tilted detector is a viable technique for detecting bulk micro-defects in Si (111) wafers.
• This advancement expands the applicability of LST to all major silicon wafer orientations.
• The developed technique ensures accurate wafer quality control for both Si (100) and Si (111) types.