Atomic force microscopy deep trench and sidewall imaging with an optical fiber probe

Area of Science:

• Metrology
• Nanotechnology
• Surface Science

Background:

• Accurate measurement of micro- and nanostructures is crucial for advanced manufacturing.
• Traditional atomic force microscopy (AFM) methods face challenges in imaging deep trenches and steep sidewalls.

Purpose of the Study:

• To develop and demonstrate a novel AFM method for measuring critical dimensions of micro- and nanostructures.
• To enable high-resolution imaging of challenging geometries like deep trenches and steep sidewalls.

Main Methods:

• Utilized an atomic force microscope (AFM) equipped with a long and thin optical fiber probe (OFP).
• Implemented a switch control scheme for flexible feedback control transfer between Z- and Y-axes for sidewall angle measurement.
• Performed serial scans on horizontal surfaces (XY-plane) and sidewalls (YZ-plane).

Main Results:

• Successfully imaged a deep trench (243.5 μm) with tapered walls and a microhole (14.9 μm).
• Characterized a silicon sidewall using a tilted OFP, demonstrating unique profiling capabilities.
• Accurately measured the sidewall angle of an AFM calibration grating (TGZ3) using the switchable scan method.

Conclusions:

• The developed OFP-based AFM method provides a versatile solution for measuring critical dimensions of micro- and nanostructures.
• The technique overcomes limitations of conventional AFM for imaging deep, narrow features and steep sidewalls.
• This advancement offers improved metrology for nanoscale fabrication and characterization.