Combinatorial Experiments Using a Spatially Programmable Chemical Vapor Deposition System
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A CVD reactor concept featuring a segmented design allows individual regions of a wafer to be exposed to different precursor concentrations simultaneously during a run resulting in different thickness profiles on the wafer and a thickness gradient at the boundaries between segment regions. Different recipes were cycled through each of the segments in a sequence of deposition experiments to develop a model relating precursor concentration to film thickness in each segment region. As a demonstration of spatial programmability, the system was re-programmed using this model to produce uniform thickness amongst the segments; inter-segment uniformity approaching 0.48 % (thickness standard deviation) was demonstrated. In a subsequent study, segmented CVD reactor designs enabling spatial control of across-wafer gas phase composition were evaluated for depositing graded films suitable for combinatorial studies. Specifically two reactor designs were evaluated with experiments and response surface model (RSM) based analysis to quantify the reactor performance in terms of film thickness uniformity, sensitivity to adjustable reactor operating conditions, range of thickness over which uniformity could be achieved and each reactor's ability to control the thickness gradient across the wafer surface. Design features distinguishing the two reactor systems and their influence on gradient control versus deposition rate performance are summarized. Response Surface (RS) models relating wafer state properties to process recipes are shown to be effective tools to quantify, qualify and compare different reactor designs.