Abstract:
A lithographic process is performed on a plurality of semiconductor wafers (900; 1020). The method includes selecting one or more of the wafers as sample wafers (910-914; 1030-1034). Metrology steps (922; 1042) are performed only on the selected sample wafers. Based on metrology results (924; 046) of the selected sample product units corrections are defined for use in controlling processing of the wafers or future wafers. The selection of sample product units is based at least partly on statistical analysis of object data (902; 1006) measured in relation to the wafers. The same object data or other data can be used for grouping wafers into groups. Selecting of sample wafers can include selecting wafers (910-914; 1030-1034) that are identified by said statistical analysis as most representative of the wafers in their group. The selecting of sample wafers can include elimination of product units (916; 036) that are identified as unrepresentative.
Abstract:
A method of grouping data associated with substrates undergoing a process step of a manufacturing process is disclosed. The method comprises obtaining first data associated with substrates before being subject to the process step and obtaining a plurality of sets of second data associated with substrates after being subject to the process step, each set of second data being associated with a different value of a characteristic of the first data. A distance metric is determined which describes a measure of distance between the sets of second data; and the second data is grouped based on a property of the distance metric.
Abstract:
A method of optimizing an apparatus for multi-stage processing of product units such as wafers, the method comprising: (a) receiving object data (210, 230) representing one or more parameters measured (206, 208) across wafers (204, 224) and associated with different stages of processing of the wafers; (b) determining fingerprints (213, 234) of variation of the object data across the wafers, the fingerprints being associated with different respective stages of processing of the wafers. The fingerprints may be determined by decomposing (212, 232) the object data into components using principal component analysis for each different respective stage; (c) analyzing (246) commonality of the fingerprints through the different stages to produce commonality results; and (d) optimizing (250- 258) an apparatus for processing (262) product units based on the commonality results.
Abstract:
A diagnostic system (242, 244, 236, 248) implements a network comprising two or more sub-domains (DOM-A, B, C). Each sub-domain comprises diagnostic information extracted by analysis of object data, the first object data representing one or more first parameters measured in relation to a first set of product units that have been subjected nominally to the same industrial process as one another. The network further comprises at least one probabilistic connection (622, 624, 626) from a first variable in a first diagnostic sub-domain to a second variable in a second diagnostic sub-domain. Part of the second diagnostic information is thereby being influenced probabilistically by knowledge within the first diagnostic information. Diagnostic information may comprise for example a spatial fingerprint observed in the object data, or inferred. The network may include connections within sub- domains. The network may form a directed acyclic graph, and used for Bayesian inference operations.
Abstract:
A method of extracting a feature from a data set includes iteratively extracting a feature (244) from a data set based on a visualization (238) of a residual pattern comprised within the data set, wherein the feature is distinct from a feature extracted in a previous iteration, and the visualization of the residual pattern uses the feature extracted in the previous iteration. Visualizing (234) the data set using the feature extracted in the previous iteration may comprise showing residual patterns of attribute data that are relevant to target data. Visualizing (234) the data set using the feature extracted in the previous iteration may involve adding cluster constraints to the data set, based on the feature extracted in the previous iteration. Additionally or alternatively, visualizing (234) the data set using the feature extracted in the previous iteration may involve defining conditional probabilities conditioned on the feature extracted in the previous iteration.
Abstract:
A method and associated computer program for predicting an electrical characteristic of a substrate subject to a process. The method includes determining a sensitivity of the electrical characteristic to a process characteristic, based on analysis of electrical metrology data including measured electrical characteristics from previously processed substrates and process metrology data including measurements of at least one parameter related to the process characteristic measured from the previously processed substrates; obtaining process metrology data related to the substrate describing the at least one parameter; and predicting the electrical characteristic of the substrate based on the sensitivity and the process metrology data.
Abstract:
A method of characterizing a deformation of a plurality of substrates is described. The method comprising the steps of: - measuring, for a plurality of n different alignment measurement parameters λ and for a plurality of substrates, a position of the alignment marks; - determining a positional deviation as the difference between the n alignment mark position measurements and a nominal alignment mark position; - grouping the positional deviations into data sets; - determining an average data set; - subtracting the average data set from the data sets to obtain a plurality of variable data sets; - performing a blind source separation method on the variable data sets, thereby decomposing the variable data sets into a set of eigenwafers representing principal components of the variable data sets; - subdividing the set of eigenwafers into a set of mark deformation eigenwafers and a set of substrate deformation eigenwafers.
Abstract:
In a lithographic process product units such as semiconductor wafers are subjected to lithographic patterning operations and chemical and physical processing operations. Alignment data or other measurements are made at stages during the performance of the process to obtain object data representing positional deviation or other parameters measured at points spatially distributed across each wafer. This object data is used to obtain diagnostic information by performing a multivariate analysis to decompose the set of said vectors representing the wafers in said multidimensional space into one or more component vectors. Diagnostic information about the industrial process is extracted using said component vectors. The performance of the industrial process for subsequent product units can be controlled based on the extracted diagnostic information.
Abstract:
Method and apparatus for adapting a distribution model of a machine learning fabric. The distribution model is for mitigating the effect of concept drift, and is configured to provide an output as input to a functional model of the machine learning fabric. The functional model is for performing a machine learning task. The method comprises obtaining a first data point, and providing the first data point as input to one or more distribution monitoring components of the distribution model. The one or more distribution monitoring components have been trained on a plurality of further data points. A metric representing a correspondence between the first data point and the plurality of further data points is determined, by at least one of the one or more distribution monitoring components. Based on the error metric, the output of the distribution model is adapted.
Abstract:
Described is a method for determining an inspection strategy for at least one substrate, the method comprising: quantifying, using a prediction model, a compliance metric value for a compliance metric relating to a prediction of compliance with a quality requirement based on one or both of pre- processing data associated with the substrate and any available post-processing data associated with the at least one substrate; and deciding on an inspection strategy for said at least one substrate, based on the compliance metric value, an expected cost associated with the inspection strategy and at least one objective value describing an expected value of the inspection strategy in terms of at least one objective relating to the prediction model.