Mesh patterning process for 40nm contact hole

Contact hole patterning is more difficult than line/space patterning as mask error factor is higher in contact hole patterning which has 2-dimensional patterns. As the industry moves towards 40nm node and beyond, the challenges associated with contact hole having a manufacturable process window have become increasingly difficult. Current 1.35NA ArF lithography is capable of printing 50nm contact hole with a stable process window at best. Conventional contact hole patterning processes such as resist reflow and RELACS are no longer able to be used for half-pitch 40nm contact hole pattern because we have to shrink not only hole diameter but also pattern pitch. In this paper, we will demonstrate and compare the patterning performance of the mesh patterning processes including litho-etch-litho-etch, cap freezing and self freezing process.