Hydrodynamic Simulation And Centrifugal Force Effect Analysis Of Chemical Mechanical Polishing Process

The semiconductor industry has been rapidly developing with the fast growth of the electronics industry. For the better integrated circuit, larger and multi-level layered wafers are needed with the accuracy of microscopic line width. Currently, CMP is most effectively used to plane each level of layers. A basic process of CMP is done by rubbing a work piece against a polishing pad under a load and with relative velocity in the presence of slurry between them. The slurry is a mixture of erosion solution having an affinity for wafer and sub-micro-scale abrasive. Therefore planarization of the wafer is accomplished by a combination of chemical action due to the erosion solution and mechanical action caused by the abrasive. The major process variables in CMP are the platen speed, down force, and slurry. These variables influence material removal rate, surface roughness, and planarity of the wafer. The final goal of CMP is uniformity and planarity of the wafer surface. To accomplish this goal, the mechanism of the CMP process must first be clearly understood for the optimum process variables to be determined.In this thesis, hydrodynamic analysis is done with a semiconductor wafer. Slurry pressure distribution, resultant forces and moments acting on the wafer are calculated in typical conditions of the wafer polishing, and then nominal clearance of the slurry film, roll and pitch angles at the steady state are obtained. Then, the Reynolds equation with centrifugal force terms is suggested and calculated here. The effects of centrifugal force on the slurry pressure distributions are obtained. Our main results are as follows:(1) Hydrodynamic analysis is done. The Reynolds equation is established.(2) Slurry pressure distribution, resultant forces and moments acting on the wafer are calculated in typical conditions of the wafer polishing. A program for this computation is established.(3) Then, the Reynolds equation with centrifugal force terms is suggested and calculated here. The effects of centrifugal force on the slurry pressure distributions are obtained.