Electron-beam lithography simulation for mask making: V. Impact of GHOST proximity effect correction on process window

As the requirements for photomask linewidth control continue to tighten, the necessity for performing proximity correction for electron beam mask exposure will increase. GHOST proximity effect correction is one method that can be used to ensure that critical dimension linearity over a large range of feature sizes meets mask user requirements. The GHOST strategy uses an additional exposure to correct for the backscatter component of the primary exposure. Because of the way the image using a GHOST correction is constructed, image contrast will be lower than exposures done without GHOST. This paper uses simulation to examine the process window that is available when GHOST is used and this process window is compared to that without GHOST. The effect of resist contrast on the process window is examined by simulating ZEP 7000 resist and comparing it to resists with other contrasts. The effects of dose, develop time, data bias and spot size on the process window are also examined.