0.10 µm Dense Hole Pattern Formation by Double Exposure Utilizing Alternating Phase Shift Mask Using KrF Excimer Laser as Exposure Light

Abstract

Dense 0.10 µm hole pattern formation is achieved by optical lithography with a KrF excimer laser. A Double exposure utilizing two alternating phase shift masks (PSMs) of the line-and-space (L/S) pattern laid out in different directions produces a dense and small hole image in bright field with large focus and exposure latitude. Applying this method with a KrF excimer laser stepper and a chemically amplified negative-tone resist, a two-dimensional (2-D) 0.10 µm hole array with 0.40 µm pitch is resolved with a 0.6 µm depth of focus (DOF). The hole diameter and pitch in the resolution limit seem to be less than 0.10 µm and 0.28 µm, respectively. Also, 2-D hole arrays with different pitches in the x and y directions are easily formed using masks with different pitches in each direction. The hole pattern of an actual DRAM cell is successfully formed by this method. Because of the excellent patterning performance, this method will enable the fabrication of multi giga bit DRAMs by KrF excimer laser lithography.