0.12 µm Optical Lithography Performances Using an Alternating Deep UV Phase Shift Mask

Manufacturing the next generation of devices will demand lithographic capability in the sub-0.18 µm range. The phase shift mask (PSM) is a key emerging technology which is thought to extend 248 nm optical lithography. Using the Levenson PSM technique allows us to improve resolution by as much as 50% at gate level. This paper describes the lithographic performances of the Shipley UV5 photoresist on SiO_xN_y bottom antireflective coating (BARC), using alternating PSM and an ASM/90 Deep UV stepper. Critical dimension (CD) measurement was done on an OPAL 7830i metrology scanning electron microscope (SEM). Results on sub-0.18 µm design rules are presented as follows. –The first part concerns experimental conditions: masks, process conditions, anti-reflective substrates, etching and metrology are discussed. –The second part concerns lithographic performances: process linearity from 0.12 µm to 0.18 µm, 0.12 µm isolated line process latitudes of 7% energy latitude for 0.8 µm depth of focus (DOF) have been exhibited. Finally we try to evaluate the proximity effect and the ultimate resolution of this technology.