| Summary: | 碩士 === 國立東華大學 === 電機工程學系 === 91 ===
Abstract
According to the technical roadmap, the density of transistor will be double in every 18 months, therefore the size of the transistor ruled keep shrinking 0.7 in every generation. Plasma processes must be served at low enough pressure for anisotropic process relative to device scale, but the plasma density corresponding etching rate will be extremely low. A new high density plasma source with independently controlled density and ion current is needed for the future development. Magnetically enhanced dual frequency capacitive discharge has been used in oxide etcher for enhancing plasma density, decreasing ion bombardment damage, and enhancing selectivity.
In this study, we calculate the parameters of the magnetically enhanced dual frequency capacitive discharge, and model the system in an equivalent circuit. Theoretically derive the sheath width, conductivity, equivalent resistance and equivalent capacitance with intensity of magnetic field, pressure and magnitude of RF power variations. An exactly solution for a dynamic variable is our attempt. The purpose is to separate linear and nonlinear effects in the discharge and try to minimize the un-predicable variation in the manufacturing process.
From the plasma parameters with the intensity of magnetic field variation, we can know the plasma density increased by the magnetic enhanced capacitive discharge due to more collision chance induced from magnetic confinement, therefore ionization rate increases. These results could be obtained from our equivalent dual frequency circuit model which is mainly dominated by sheath thickness. In which, the plasma generated is controlled by the high frequency source and the low frequency source mainly control ion current. Power consumption ratio of the high frequency source and low frequency source has been computed in the plasma bulk and sheath from the equivalent circuit model.
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