An accuracy improvement method for the topology measurement of an atomic force microscope using a 2D wavelet...

Area of Science:

• Materials Science
• Nanotechnology
• Metrology

Background:

• Topology imaging relies on Z nano scanner height data, but nonlinear effects (hysteresis, creep) cause inaccuracies with large variations.
• Direct displacement measurement using strain gauges offers linearity but suffers from low precision and high-frequency noise.
• Controller output provides low noise but may lack precision for accurate topology reconstruction.

Purpose of the Study:

• To develop a method for accurate topology imaging by overcoming the precision limitations of strain gauges while maintaining their linearity.
• To integrate high-frequency noise data from controller output with low-frequency, linear data from strain gauges.
• To improve the accuracy and reduce noise in topology images generated from PZT-driven nano scanners.

Main Methods:

• A 2D Haar wavelet transform was employed to separate and combine low-frequency (strain gauge) and high-frequency (controller output) signals.
• The proposed method leverages the linearity of strain gauges and the precision of controller output for enhanced topology image construction.
• Experimental validation using topology images was performed to demonstrate the method's advantages.

Main Results:

• The 2D Haar wavelet transform effectively separated high-frequency noise from controller output and low-frequency signals from the strain gauge.
• The combined approach yielded topology images with both high accuracy (from strain gauge linearity) and low noise (from controller output).
• Experimental results confirmed the proposed method's ability to produce superior topology images compared to traditional methods.

Conclusions:

• The proposed wavelet-based method successfully integrates the strengths of strain gauges and controller output for high-fidelity topology imaging.
• This technique overcomes the inherent limitations of individual sensors, leading to more accurate and precise nanoscale surface measurements.
• The validated method offers a significant advancement in metrology for applications requiring detailed surface topology analysis.