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The objective of this thesis is to develop a polishing model,
which considers the patterns on the wafer surface, and investigate the
effects of the polishing parameters of CMP process.
With isolating the roles of chemical and mechanical effects, this
thesis focuses on the mechanical polishing behaviors and polishing
kinematics of CMP. The polishing motion is modeled by the open-loop
manipulator, which is kinematically equivalent to the motion of CMP. The
polishing velocity is obtained as a function the polisher geometry, the
angular velocity ratio and the table speed. A polishing model is
established with the consideration of the influences caused by the
patterns. A time-dependent removal rate formula is established based on
the decrement of pattern step height. Comparisons with experimental data
demonstrate how to acquire necessary parameters and verify the validity of
the model.
From the polishing model, the symbolic formulation of the
polishing time, polished thickness and the planarization efficiency can be
obtained. The local polishing behaviors can be expressed by the polishing
time, polished thickness and the planarization efficiency of considered
point. The relation of the uniformity of the global planarization and the
angular velocity ratio of carrier and pad, applied pressure and the pad
material are also presented. The effects of the variation of the polishing
parameters are summarized and illustrate the trends in adjusting the
polishing parameters. The results of this thesis can lead to a rational
and efficient predict and improve the CMP process.
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