1. A modeling method, comprising: inputting tool parameters into a model; inputting basic model parameters into the model; generating a simulated, corrected reticle design using the tool parameters and the basic model parameters; comparing an image of test patterns for an integrated circuit against the simulated, corrected reticle design; determining whether a difference between the simulated, corrected reticle design and exposure results of the image of the test patterns is less than a predetermined criteria; completing the model when the difference between the simulated, corrected reticle design and the exposure results of the image of the test patterns is less than the predetermined criteria; and outputting information about variation of image to the tool parameters in order to determine which tool parameters are to be used in the model.