Detecting 20 nm wide defects in large area nanopatterns using optical interferometric microscopy

Area of Science:

• Optics and Photonics
• Semiconductor Manufacturing
• Metrology

Background:

• Visible laser light is typically unsuitable for detecting subwavelength defects in semiconductor wafers due to resolution limits and speckle noise.
• Existing methods may struggle with sensitivity and field of view for nanoscale defect detection.

Purpose of the Study:

• To develop a nondestructive, low-noise interferometric imaging method for detecting nanoscale defects in patterned semiconductor wafers using visible light.
• To demonstrate the capability of imaging subwavelength defects with high sensitivity and a wide field of view.

Main Methods:

• Utilized a common-path laser interferometer for stable measurements.
• Employed digital image processing techniques for noise reduction and image enhancement.
• Generated panoramic phase and amplitude images of nanopatterns.

Main Results:

• Achieved significant noise reduction and high sensitivity in the imaging process.
• Successfully detected sparse defects as small as 20 nm wide, 100 nm long, and 110 nm tall.
• Produced 70 μm by 27 μm panoramic images of the test nanopattern.

Conclusions:

• The developed interferometric imaging method is practical for detecting deep subwavelength defects in semiconductor wafers using visible light.
• This technique offers a low-noise, high-sensitivity solution for nanoscale metrology in semiconductor inspection.