Abstract: Objective: For conventional optical discs

the pit width and depth remain the same. But for multi-level run-length-limited optical discs

both the pit width and depth vary with the levels. Thus stricter requirement for mastering process is needed. The mastering process is worthy of in-deep research. Method: A photolithography model for optical disc mastering is built

where the vector diffraction is used to calculate the intensity distribution of the focused light spot

and the light propagation in multi-layer film structure is used to describe the light propagation in photo-resist. Result: The experiment and simulation results are present

including the influences of key process parameters on typical multi-level pit width and depth. These process parameters include photo-resist thickness

development time and developer concentration. The decrease of photo-resist thickness will cause increased width and deceased depth. The effects of the increases of development time and developer concentration are similar

each of which will cause increased width and depth. Conclusion: The accordance of experiment and simulation validates the model. Analysis results are helpful to the practical multi-level disc mastering. Meanwhile

the model can be used to analysis other process parameters

and mastering of other disc format mastering.