19-nm critical dimension process using mask shift double exposure in ArF immersion

This article describes the formation of a 19 nm line critical dimension (CD) using a mask shift double exposure (MSDE) method to extend beyond the resolution limit of the current 38 nm line space pattern line CD in ArF immersion photolithography. There is no change in pitch (76 nm), but experiments are being conducted to reduce extreme line CD using optical trim. In the general photolithography process, patterning is performed by transferring the pattern of a mask to the photoresist (PR) of a wafer through a single exposure. MSDE is a method of patterning by exposing energy to the PR of the wafer twice consecutively without unloading the wafer and mask. It was confirmed that the first and second exposure energies are linearly summed, showing that the combination of the first and second exposure patterns allows for more sophisticated patterning than one exposure. When the two exposure patterns are parallel lines in the MSDE approach, a 19 nm line CD is realized by precisely controlling the line CD according to the exposure interval between the two lines. It is possible to form a line CD smaller than that in the case of a single exposure overdose. In addition, when the two exposure patterns are orthogonal lines in MSDE, a 29 nm pillar pattern can be realized, which is beyond the limit of resolution of ArF immersion lithography. If MSDE is applied to semiconductor process technology, the performance of litho-etch-litho-etch and self-aligned double patterning, which are double patterning technologies, can be improved, and the number of process steps can be reduced. It is also demonstrated that MSDE can be implemented in immersion.