Photomasks for advanced lithography

The mask in lithography is the heart of the resulting image on the semiconductor wafer. The mask defines the image to be transferred to the wafer. The evolution of semiconductor manufacturing has seen masks improve from contact devices, that were good for a few pattern transfers, to projection/reduction masks that can be employed for tens of thousands of transfers. As the shrinking of the device dimensions continues, the challenges of obtaining the required quality mask images increases. Optical Proximity Correction (OPC) and Phase Shift Masks (PSM) are increasing the complexity of the masks and producing finer images. As the Next Generation lithography evolves, additional challenges will face the mask manufacturing professional. This paper is an overview of the requirements for the various types of masks.