By Yuji Setta, Tatsuo Chijimatsu, Satoru Asai, Fujitsu Ltd., Tokyo, Japan
Arrays of 100nm contact holes can be printed with adequate depth of focus (DOF) through pitch using dry 193nm wavelength exposure and a special illuminator design.
Contact holes are among the most difficult IC structures to pattern. The design rule for nested holes patterns at the 65nm-node generation assumes a spacing almost the same as the wavelength used in ArF lithography. To obtain good resolution and process stability, we need to choose a high-NA (numerical aperture) exposure tool. High NA tools, however, tend to have short DOF, reducing the available process window.