Topographic measurement of encapsulated microstructures via active wavefront-compensatory coherence scanning...

Area of Science:

• Optical Metrology
• Microstructure Analysis
• Semiconductor Packaging

Background:

• Accurate measurement of buried microstructures is critical for advanced semiconductor packaging.
• Existing techniques face challenges with signal degradation through encapsulating layers.

Purpose of the Study:

• To introduce a novel, robust, high-precision measurement technique for buried microstructures.
• To enhance signal fidelity and signal-to-noise ratio under encapsulating layers.

Main Methods:

• Development of active wavefront-compensatory coherence scanning interferometry (AWC-CSI).
• Integration of high numerical aperture (NA) optics and a deformable mirror for aberration correction.
• Utilizing a dispersion-matched compensation plate in the reference arm.

Main Results:

• Demonstrated average topographic lateral resolution of approximately 0.95 μm under 100-300 μm encapsulation.
• Achieved a system optical resolution of 0.89 μm.
• Significantly enhanced signal fidelity and signal-to-noise ratio.

Conclusions:

• AWC-CSI provides effective high-precision inspection of buried microstructures.
• The technique shows potential for advanced packaging process optimization.
• Validated performance on packaged micro-electromechanical systems (MEMS) devices.