Method and apparatus for critical dimension and tool resolution determination using edge width

摘要

A method for monitoring a process in which a feature is formed on a substrate. A plurality of dimensions of the feature are measured using a tool. An edge width of the feature is calculated based on the plurality of dimensions. The edge width is used to determine whether the process is operating within a desired specification. The calculated edge width is compared to a baseline edge width measurement to determine a difference between them. The process is determined to be operating within the specification if the difference is less than a threshold value. If the difference is greater than or equal to the threshold value, the method determines whether the difference is caused by a change in resolution of the tool. A plurality of diagnostic measurements of the edge width may be performed. The tool is adjusted to have a respectively different focus for each respective one of the plurality of diagnostic measurements. The method includes determining that the difference between the calculated edge width and the baseline edge width is caused by a change in resolution of the tool if any one of the plurality of diagnostic measurements of the edge width differs from the baseline edge width by less than the threshold value. The method also includes determining that the process is not operating within the specification, if the difference is greater than or equal to the threshold value, and the difference is not caused by a change in resolution of the tool.