Fast wafer focus measurement system for photolithography using on-axis structure illumination method

•The method proposed in this article requires only a single-step sampling process to calculate the average defocus distance of each point on the silica wafer, thereby ensuring the exposure consistency of the whole exposure area as possible.•The surface profile of the silica wafer is measured at the same time. This data can be used to adjust the height and tilt degree of the wafer stage or directly mark this exposure field as a bad shot if it is damaged.•The measured area is highly overlapped with the exposure area because of the on-axis optical path.