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Hybrid Bright-Dark-Field Microscopic Fringe Projection System for Cu Pillar Height Measurement in Wafer-Level
Dezhao Wang1,2, Weihu Zhou1,2,3, Zili Zhang2,3
1College of Opto-Electronic Engineering, Changchun University of Science and Technology, Changchun 130022, China.
Sensors (Basel, Switzerland)
|August 29, 2024
Summary
A new hybrid bright-dark-field system enhances microscopic fringe projection profilometry (MFPP) for measuring copper (Cu) pillar height. This method improves on-line measurement accuracy for 3D chip stacking in heterogeneous integration.
Area of Science:
- Materials Science
- Optical Metrology
- Semiconductor Manufacturing
Background:
- Copper (Cu) pillars are critical for 3D chip stacking in heterogeneous integration.
- Uniform Cu pillar height is essential for maximizing chip yield.
- Existing measurement techniques like interferometry and confocal microscopy lack the throughput for on-line wafer-level packaging measurements.
Purpose of the Study:
- To develop an advanced measurement technique for Cu pillar height uniformity in wafer-level packaging.
- To overcome the challenges posed by the large curvature and smooth surfaces of Cu pillars for optical measurement.
- To enable accurate, high-throughput on-line measurement of Cu pillars.
Main Methods:
- Utilized rigorous surface scattering theory to model the bidirectional reflective distribution function of Cu pillar surfaces.
- Developed a hybrid bright-dark-field microscopic fringe projection profilometry (MFPP) system.
- Leveraged scattering properties to detect weak signals from pillar tops and reflected signals from substrates.
Main Results:
- The proposed hybrid MFPP system successfully measures Cu pillar height.
- Achieved an effective field of view of 15.2 mm × 8.9 mm.
- Demonstrated a maximum measurement error of less than 0.65 μm.
Conclusions:
- The hybrid bright-dark-field MFPP system offers a viable solution for on-line Cu pillar height measurement.
- This technique enhances throughput and accuracy for heterogeneous integration applications.
- The study provides a foundation for improved quality control in wafer-level packaging.
