New imaging technique for 64M-DRAM

TLDR: In this paper, a new photolithographic technique called SHRINC (Super High Resolution by Illum-nation Control ) is proposed to improve the resolution and depth-of-focus by optimum arrangement of the illumination system in respect of the angle of the 1st-order of diffraction generated by the reticle pitch.

Abstract: We have established a new photolithographic technique called SHRINC ( Super High Resolution by Illum-Nation Control ) which is based on an innovative illumination system. SHRINC improves the resolution and depth-of-focus ( DOF ) by optimum arrangement of the illumination system in respect of the angle of the 1st-order of diffraction generated by the reticle pitch. The capabilities of SHRINC have been studied by computer simulation. Results from phase shift, annular illumination, and conventional illumination are compared with those of SHRINC. The results show that using SHRINC with 0.35μm line and space patterns, the DOF, defined as the distance over which the aerial image contrast exceeds 60%, is 2.5x larger than that obtained with conventional illumination, and almost the same as that with phase shift techniques. In our experiments we have obtained a critical resolution of 0.275μm and more than 2.8 μm DOF with 0.35μm L/S patterns, using an i-line stepper and SHRINC illumination. Moreover SHRINC is effective not only for simple line and space patterns, but also for complicated patterns with 0.30 or 0.35μm design rules, such as memory cell patterns or peripheral circuit patterns in the DRAM. From these results we conclude that i-line steppers with SHRINC will make possible pass production of 64M-DRAMs with single layer resist.