Patent ID: 7105436

Claim:
A method for characterizing an etching process, the method comprising: performing an etching process to a first layer to form an array of via regions and to a second layer to form at least a first via outside the array of via regions, the first layer associated with a first thickness, the second layer associated with a second thickness; obtaining an image of the array of via regions; determining a plurality of via regions in the array of via regions, each of the plurality of via regions includes a second via and a third via corresponding to a dark area and a bright area on the image respectively; processing information associated with the plurality of via regions and the first via; determining a first depth associated with the first via relative to the second thickness based on at least information associated with the plurality of via regions and the first via; wherein: the processing information associated with the plurality of via regions and the first via includes determining a threshold depth with respect to the first thickness; the threshold depth is related to a transition from a dark region to a bright region on the image.