Dechuck Operation of Coulomb Type and Johnsen-Rahbek Type of Electrostatic Chuck Used in Plasma Processing

Abstract

Comparative study on Coulomb type and Johnsen-Rahbek type of electrostatic chuck used for holding a silicon wafer in plasma processing is presented. The remarkable differences between the two types are found in dechuck operation where a high voltage applied to the chuck electrode is turned off to release the wafer from the chuck stage. In case of the Coulomb type, an instantaneous large short-circuit current flows exponentially decreasing with a short time constant (τ = 0.14 ms). In case of the J-R type, a non-exponentially decaying small current is sustained for much longer time (∼1000 ms), thus giving rise to the considerable delay of wafer dechuck. The mechanism of such decay is explained by a microscopic bi-layer model where the interfacial layer is divided into three distinct regions having their own capacitance and surface resistance.