Real-time laser differential confocal microscopy without sample reflectivity effects.

Area of Science:

• Optics and Photonics
• Surface Metrology
• Microscopy

Background:

• Confocal microscopy (CM) is limited by sample reflectivity variations, complicating accurate height topography imaging.
• Existing methods struggle to differentiate between surface height and reflectivity differences in real-time.
• High-resolution surface profiling is crucial for semiconductor manufacturing and materials science.

Purpose of the Study:

• To introduce a new real-time laser differential confocal microscopy (RLDCM) method.
• To overcome the limitations of sample reflectivity difference effects in height topography imaging.
• To achieve real-time, high-resolution surface imaging for heterogeneous samples.

Main Methods:

• Dividing the confocal microscopy imaging light path into two paths (before and after focus) with opposite axial detector offsets.
• Simultaneously detecting signals from both paths and calculating their difference relative to the higher signal.
• Implementing single-layer scanning for reduced imaging time.

Main Results:

• RLDCM successfully separates topographic signals from reflectivity heterogeneity in real-time.
• Achieved significant reduction in height topography imaging time for samples with reflectivity variations.
• Demonstrated 2-nm axial depth resolution with lateral resolution comparable to traditional CM.
• Successfully imaged line structures of Silicon Dioxide steps on a Silicon base.

Conclusions:

• RLDCM provides a breakthrough for real-time surface topography imaging, especially for samples with reflectivity heterogeneity.
• The method offers high axial and lateral resolution without compromising imaging speed.
• RLDCM has significant potential for applications in semiconductor inspection and advanced materials characterization.