The use of an electrostatic chuck to support and flatten an extreme ultraviolet (EUV) mask during scanning exposure
will be a critical component to meet the stringent requirements on image placement errors in the sub-30-nm regime.
Consequently, the ability to predict the response of the mask during e-chucking is necessary for the design and
implementation of the e-chuck system. This research focuses on characterizing the coefficient of friction between the
EUV reticle and the dielectric material of the chuck. A customized tool was constructed to test chuck and reticle
samples both in air and in a vacuum chamber. Studies were conducted to identify the friction coefficient at various
chucking pressures and to examine the effects of wear caused by repeated measurements on the same location of the
reticle surface. All experiments were performed in a cleanroom environment. Results of the friction testing illustrate the
range of values to expect for typical EUV reticles and chucks. Finite element (FE) modeling was then used to illustrate
the effects of friction on the overall capability of the chuck to flatten the mask. Additional FE simulations demonstrated
the magnitude of the friction force needed to ensure that the reticle would not slip during the acceleration / deceleration
loading seen in the scanning exposure process.