Dependence of Plasma‐Assisted BPSG Deposition on Substrate Properties
It is well known that the deposition rates and compositions of plasma‐deposited BPSG reflow glass films depend upon the deposition parameters of the reactor such as flow rates of the reactants, RF excitation, temperature distribution, and position of the wafers in the reactor. The characteristics of the deposited films also depend upon the properties of the substrates upon which they are deposited, but these dependences have not been previously characterized. We have measured the dependence of these characteristics upon commonly encountered substrate properties using a multifactoral experimental design and analysis that permitted us to separate the substrate dependences from the spatial variations in the reactor, and also to evaluate the statistical significance of the results. Experiments performed in an ASM plasma reactor produced significant dependences of deposition characteristics upon wafer thickness and upon aluminization of the wafer surface, while no dependence was found upon wafer resistivity (doping level) or doping type (p or n). We also found that the film characteristics depend upon the properties of the wafer located in the opposite position in the reactor cell, and have shown that patterns can be transferred from one wafer to another in the cell. Both doped and undoped glasses were studied.
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