Feedforward control of multi-layer stacks during device fabrication

A method of forming a multi-layer stack on a substrate comprises: processing a substrate in a first process chamber using a first deposition process to deposit a first layer of a multi-layer stack on the substrate; removing the substrate from the first process chamber; measuring a first thickness of the first layer using an optical sensor; determining, based on the first thickness of the first layer, a target second thickness for a second layer of the multi-layer stack; determining one or more process parameter values for a second deposition process that will achieve the second target thickness for the second layer; and processing the substrate in a second process chamber using the second deposition process with the one or more process parameter values to deposit the second layer of the multi-layer stack approximately having the target second thickness over the first layer.