Qinetiq Limited

Allister W E Dann

David John Robbins

John L Glasper

Christopher Pickering

Alan D Marrs

John Russell

Layer processing to grow a layer structure upon a substrate surface comprises supplying a vapor mixture stream to the substrate ( ) to deposit constituents, monitoring growth with an ellipsometer ( ) and using its output in real-time growth control of successive pseudo-layers. A Bayesian algorithm is used to predict a probability density function for pseudo-layer growth parameters from initial surface composition, growth conditions and associated growth probabilities therewith, the function comprising discrete samples. Weights are assigned to the samples representing occurrence likelihoods based on most recent sensor output. A subset of the samples is chosen with selection likelihood weighted in favor of samples with greater weights. The subset provides a subsequent predicted probability density function and associated pseudo-layer growth parameters for growth control, and becomes a predicted probability density function for a further iteration of pseudo-layer growth.

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Malvern, United Kingdom

Allister W E Dann