Contact hole formation by multiple exposure technique in ultralow-k 1 lithography

Abstract

The double line and space (L&S) formation method with L&S masks and dipole illumination was found to have high capability to fabricate about 0.3-k₁ contact hole (C/H) pattern. The procedure was as follows. The first L&S pattern was formed and was hardened to avoid the dissolution and mixing during the second resist coating. The second L&S pattern perpendicular to the first one was formed on the first resist pattern. The common space area of the two patterns became 1:1 C/H pattern. Simulation results showed that the double L&S formation method has much wider lithography latitude than other methods, such as single exposure of a C/H mask with quadrupole illumination, single exposure of a vortex mask with conventional illumination, and double exposure of L&S masks with dipole illumination to a single layer resist. 75-nm (0.30-k₁) 1:1 C/H pattern was fabricated. 80-nm (0.32-k₁) 1:1 C/H pattern had 280 nm and 600 nm depth of focus (DOF) in each resist layer. Moreover, a new method, in which a C/H mask replaces the L&S masks, is proposed to achieve cost reduction and the same high performance as the L&S masks.