Subwavelength lithography (PSM, OPC)

Fabrication of fine features of smaller than 0.15 /spl mu/m is vital for future ultra-large scale integrated (ULSI) devices. An area of particular concern is whether and how optical lithography can delineate such feature sizes, i.e., smaller than the exposure wavelength. Resolution enhancement techniques for achieving subwavelength optical lithography are presented. Various types of phase shift mask (PSM) techniques and their imaging characteristics are discussed and compared to conventional binary mask technique. To apply these masks effectively to practical patterns, optical proximity effect correction (OPC) technique and a phase shifter pattern design tool must be established. These techniques offer the capability to improve resolution to exceed the wavelength limitation and to increase depth of focus.