Low k1 contact hole formation by double L&S formation method with contact hole mask and dipole illumination

Contact hole (C/H) patterns are one of the pattern types that are difficult to form. The methods to form ∼0.3 k₁ C/H patterns are investigated. One of the methods proposed is the double L&S formation method, which provides high resolution and wide process margin (Nakamura et al., 2004). One of the drawbacks of the L&S formation method is the use of two masks, which increases the production cost. So the use of one C/H mask instead of two L&S masks with dipole illumination was proposed to form L&S resist pattern on a wafer (Nakamura et al., 2004). The method with one C/H mask is expected to have the same performance as that with two L&S masks in view of simulation results.