Quantitative phase retrieval with arbitrary pupil and illumination

Area of Science:

• Optics and Imaging
• Materials Science
• Nanotechnology

Background:

• Quantitative phase imaging is crucial for analyzing microscopic structures.
• Existing methods struggle with diverse illumination and imaging conditions.
• Accurate defect characterization in Extreme Ultraviolet Lithography (EUV) masks is vital for semiconductor manufacturing.

Purpose of the Study:

• To develop a general algorithm for quantitative extraction of object wave amplitude and phase.
• To extend the algorithm beyond the weak object approximation.
• To demonstrate the algorithm's efficacy on EUV multilayer mask defects.

Main Methods:

• Utilizing a weak object transfer function incorporating arbitrary pupil functions and partially coherent illumination.
• Employing an iterative algorithm to extend the approach beyond the weak object regime.
• Applying the method to measurements from an EUV zone plate microscope with standard and phase contrast zone plates.

Main Results:

• Successfully combined measurements from various conditions to quantitatively extract amplitude and phase.
• Demonstrated the algorithm's capability in analyzing Extreme Ultraviolet Lithography (EUV) multilayer mask defects.
• Validated the method using both standard and Zernike phase contrast zone plates.

Conclusions:

• The presented algorithm offers a robust method for quantitative phase imaging under diverse conditions.
• This technique significantly enhances the analysis of defects in EUV masks.
• The iterative extension broadens the applicability of quantitative phase retrieval.