150nm Dense/Isolated Contact Hole Study with Canon IDEAL Technique

摘要

This paper presents the results of a joint development effort between Canon U.S.A., Inc. and Photronics, Inc. on 150nm contact hole application. A double exposure technique, Canon's IDEAL technique, is used to achieve the very small dense contact hole and isolated contact hole simultaneously. Canon's IDEAL exposure technique has shown, through numerous documented investigations, to be beneficial for extending the current lithography tool life with regards to line patterns. However it is also now equally important to evaluate IDEAL's advantages for contact holes. We look to apply the IDEAL technique to contact holes by using a Hole-shaped alternating Phase Shift Mask (alt-PSM) for the grid and a binary mask for trimming. This experiments were performed on a Canon FPA-3000EX6 5X stepper with maximum NA0.65, using JSR TMX1260Y 300nm thick resist. All masks were made by Photronics. Since image intensity imbalances of Hole shaped alt-PSMs were too large to generate a perfect grid, we exposed twice with the same Hole-shaped alt-PSM reticle. The second exposure was shifted to combine 0 degree and 180-degree space, thereby creating a well-balanced grid. Subsequently, we used a binary mask for trimming. Through this method, 0.15um dense holes and 0.15um isolated holes with simple reticle bias were resolved simultaneously, and over 0.6um common Depth of Focus (DoF) was obtained. Due to the high accuracy alignment between the PSM hole mask and binary mask from this experiment, double and triple exposure schemes can be used in actual production. Based on these experimental results, we also confirmed that the IDEAL technique allows for a 50nrn (on wafer) combination error of stage stepping and reticle alignment without inducing significant CD error. A well-balanced grid can be generated using the vertical line PSM and horizontal line PSM, by minimizing image intensity imbalances due to PSM structures, however, the three-reticle application may prove prohibitive due to the increase in reticle cost.