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 unit. This object data is used to obtain diagnostic information by performing a multivariate analysis to decompose a set of vectors representing the units in said multidimensional space into one or more component vectors. Diagnostic information about the industrial process is extracted using the component vectors. The performance of the industrial process for subsequent product units can be controlled based on the extracted diagnostic information.
Abstract:
A reticle is loaded into a lithographic apparatus. The apparatus performs measurements on the reticle, so as to calculate alignment parameters for transferring the pattern accurately to substrates. Tests are performed to detect possible contamination of the reticle or its support. Either operation proceeds with a warning, or the patterning of substrates is stopped. The test uses may use parameters of the alignment model itself, or different parameters. The integrity parameters may be compared against reference values reflecting historic measurements, so that sudden changes in a parameter are indicative of contamination. Integrity parameters may be calculated from residuals of the alignment model. In an example, height residuals are used to calculate parameters of residual wedge (Rx′) and residual roll (Ryy′). From these, integrity parameters expressed as height deviations are calculated and compared against thresholds.