Entering Mask Process Correction era for EUV mask manufacturing

摘要

The 50keV ebeam exposure of EUV blanks leads to additional electron backscattering from the tantalum layer and the mirror portion of the blank substrate that cannot be adequately corrected by in-tool algorithms. Coupling this additional backscatter with process effects, such as develop and etch micro/macro loading, results in significant systematic Critical Dimension (CD) errors for through pitch and linearity patterns on EUV masks. In wafer production EUV masks are targeted as single layer exposure, which requires extremely stringent CD control. The systematic CD errors can easily exceed the CD requirements of a typical EUV mask, facilitating the need for a correction scheme or mask process correction (MPC). AMTC and GLOBALFOUNDRIES have started a program to evaluate MPC solutions and drive improvements. Working closely with companies that provide solutions for ebeam and process modelling along with the corresponding correction, we have completed several iterations of MPC evaluations. Specifically, we have tested different equipment, processes and process partitioning for model calibration including a verification of the results. We report on the results of these evaluations, which include simulation of available models, as well as verification data from mask prints. We conclude by summarizing the current capabilities of available MPC solutions and present the remaining gaps for model and correction accuracy as well as the remaining questions for fully implementing MPC into the process landscape.