A 3D nano-resolution scanning probe for measurement of small structures with high aspect ratio

• A 3D nano-resolution scanning probe based on differential detection of astigmatic focus error is proposed and developed using commercial DVD optical pick-ups as sensing elements, and proposed for measurement of small structures with high aspect ratio.
• A design of parallel kinematic flexible suspension with vertical and orthogonal layout of commercial DVD optical pick-ups is proposed, solving the serious conflict between resolution and lateral size of the probe, and common mode interference is suppressed by differential detection of signals.
• A probe whose displacement resolution is up to 1 nm with a ϕ3 mm probing ball and a 150 mm long stylus is developed. Experimental results show it is competent for measurement of small structures with high aspect ratio with high precision and low cost.

A tactile 3D scanning probe based on differential detection of astigmatic focus error is developed using commercial DVD optical pick-ups as sensing elements, and proposed for measurement of small structures with aspect ratio up to 30:1. The conflict between resolution and lateral size of the probe is resolved by a design of parallel kinematic flexible suspension with vertical and orthogonal layout of sensing elements, and common mode interference is significantly suppressed by differential detection of astigmatic focus error signals. Experimental results show that the displacement resolution of the probe is up to 1 nm with a ϕ3 mm probing ball and a 150 mm long stylus. It is therefore concluded that the probe proposed is a solution for measurement of structures with high aspect ratio with high precision and low cost.