Thermal distribution of wafers during contactless handling on active air bearings

Abstract

Current wafer handling methods in the high-tech industry rely on mechanical contact to transport and position wafers. This leads to high breakage rates and contamination, ultimately reducing product yield. To overcome these challenges, TU Delft has developed several air-based contactless handling systems. However, stringent thermal requirements in the high-tech industry demand a highly uniform and stable temperature distribution across the wafer, posing significant challenges for such systems. Hence, research is performed on the thermomechanical effects of active air bearings on wafers during contactless handling.

Initially, a comprehensive theoretical analysis is performed on fluid flow and heat transfer phenomena in simplified geometries. Both rectilinear and axisymmetric models are developed to capture essential aspects of laminar thin film flows. Analytical expressions reveal the balance between expansion and viscous dissipation effects, particularly for rectilinear Poiseuille flow. The thesis further advances to complex numerical modelling using COMSOL Multiphysics, refining the geometry to better mirror actual operating conditions and incorporating the influence of mechanical wafer deformation.

In parallel, an experimental test setup is designed and implemented to replicate the operational environment of an air bearing system in a simplified form. This setup enables controlled measurement of temperature profiles and wafer deformation using complementary sensor techniques. One technique provides absolute temperature calibration, while another maps the relative temperature distribution across the wafer surface. Additionally, an optical method inspired by free-surface synthetic schlieren is used to quantify wafer deformation. This experimental setup not only serves to validate the theoretical models and numerical COMSOL simulations but also aims to explore measurement techniques applicable to operational air bearing systems.