Attractive Force Increased by Rotational Degree-of-Freedom Tip Structure Used in Beam Structure Electrostatic Chucks

Abstract

Conventional Electrostatic chucks (ESC) are wafer manipulation devices widely used in silicon industry but lacks the ability to deal with irregular shaped or film targets. Beam Structure ESCs (BSESC) have been proposed as a solution to overcome this limitation. Nevertheless, they exhibit non-ideal contact behaviour between the tip and the surface, leading to low performance. This study utilizes torsion springs as medium for providing rotational degree-of-freedom (RDOF) at the tip structure of BSESC, allowing the tip to full contact the target surface, which is expected to be beneficial for attractive force generation. The paper verifies the feasibility of force increase through adding RDOF by firstly using finite element method simulation for numerical calculation, then verifies the results using experimental methods. In simulation process, BSESC Models consisting of spring linkages with different rotatabilities were set up in COMSOL and correlation between tip RDOF and attractive force generation was calculated. In experimental process, devices with only tip RDOF difference were built and force measurement were executed for the verification. The results prove that RDOF tip structure can effectively increase attractive force generation by BSESCs. Differences between simulation and experimental results are discussed, and insight into further development of BSESCs is provided.