Sidewall Profile Inclination Modulation Mask (SPIMM): Modification of an Attenuated Phase-Shift Mask for Single-Exposure Double and Multiple Patterning

摘要

As 193 nm immersion lithography may be required to be extended beyond 20 nm node, multiple patterning lithography will become a necessity in that scenario. We present a cost-effective approach for 22 nm half-pitch double patterning, with extendibility to sub-10 nm half-pitch pitch division. Spacers on sufficiently sloped sidewalls directly transferred from a low-contrast photoresist profile can be removed by anisotropic etching. Alternatively, spacer gaps for defining trenches may be prevented from penetrating to the substrate by the use of sloped sidewalls. These sloped sidewalls are defined by attenuated phase shift mask (attPSM) features which impart phase shifts other than 180 or 0 degrees. Such features can be accommodated in the process flow for fabricating phase shift masks by the definition of one or two extra layers of processing in the mask shop. Aerial image simulations show this photomask design is more effective in generating sloped foot profiles in the photoresist than simply using sub-resolution features or reducing the width of the clear region. Loop trimming and sidewall spacer definition are accomplished in a single photomask. In addition, there is now an extra ability to define random, arbitrary breaks in the spacer-defined pattern, without using an extra exposure for specified cuts. In this way, a single exposure of a low-contrast photoresist around the sensitivity limit using a modified attenuated phase-shift photomask is sufficient to pattern regularly arranged spacer-defined lines at fixed pitch with irregularly arranged breaks, or 'cuts' in the lines.