Patent ID: 8437870

Claim:
A virtual metrology (“VM”) advanced process control (“APC”) system comprising: a process tool for processing a plurality of wafers in accordance with process inputs received thereby; a metrology tool for measuring a feature of one or more wafers of the plurality of wafers and generating actual metrology data therefrom, wherein the one or more wafers comprises one or more quality control (“QC”) sample wafers; a VM model for predicting metrology data for each of the plurality of wafers; an APC controller for receiving the predicted metrology data and the actual metrology data and for generating the process inputs to the process tool in accordance with the predicted and actual metrology data; and an adjustment unit configured to filter the predicted metrology data for each of the wafers from the plurality of wafers by applying an exponentially weighted moving average (“EWMA”) filter to the predicted metrology data using historical EWMA metrology data and current actual EWMA metrology data, wherein the current actual EWMA metrology data is described by a model equation expressed as: Y Current Actual EWMA =(1−ω)* Y Historical EWMA +ω*Y Metrology wherein ω denotes a weight factor, Y Historical EWMA denotes the historical EWMA metrology data collected from other QC sample wafers, and Y Metrology denotes the actual metrology data for the QC sample wafer processed by the metrology tool, wherein the filtered predicted metrology data for each of the wafers from the plurality of wafers is described by a model equation expressed as: Y Filtered Predicted Metrology Data =(1−ω)* Y Current Actual EWMA +ω*Y Predicted Metrology Data wherein ω denotes the weight factor, Y Current Actual EWMA denotes the current actual EWMA metrology data, and Y Predicted Metrology Data denotes the predicted metrology data from the VM model for one of the wafers from the plurality of wafers; and wherein the actual metrology data for the QC sample wafer is used to update the VM model; and wherein key variables of the VM model are updated only in response to a determination that the metrology data predicted by the VM model is inaccurate; and wherein parameters of the VM model are updated responsive to receipt of the actual metrology data for the QC sample wafer.