Pixel-based partially coherent image method for maskless lithography system

Maskless lithography (ML) provides a fast and low-cost method for projecting the images of IC or micro features onto photoresist. However, it needs an efficient simulation method to evaluate the performance of lithography process. In this paper, a pixel-based partially coherent image method for digital micro-mirror device (DMD) based ML is proposed based on the linear invariant theory. In our method, the mask is sampled by DMD pixel (each pixel corresponding to each micro-mirror) and expressed by rect function. Using the shift theory of Fourier transform and the stacked pupil operator approach, we build a matrix Φ for system response function of rect function. If the DMD pixel state matrix is S, then the aerial image can be calculated with two matrix multiplication I(x,y) = SΦ.