CD control comparison for sub-0.18-μm patterning using 248-nm lithography and strong resolution enhancement techniques

Abstract

In the constant drive to go to smaller feature sizes, the control of the linewidth become more important than ever before, with the intra-field CD-control as a major contributor. It is expected that 248 nm lithography will be used for volume manufacturing of the 0.15 micrometers generation and may even be pushed to 0.13 micrometers . In order to do so, strong resolution enhancement technique such as aggressive optical proximity correction (OPC) and alternating phase- shifting masks (altPSM) will be needed. However a strong interaction with reticle CDs and lens aberrations is expected. With the use of state-of-the-art reticles and lenses, not only the process latitudes at one point in the field but the CD-control across the full field become very important. In this paper an illumination optimization has been done in terms of individual process latitudes, CD- proximity effect and especially the across-field CD- variation. With these optimized stepper settings, a comparison of the intra-field CD-control of binary masks with OPC and altPSM for 0.15 micrometers and 0.13 micrometers features with various duty cycles using a high NA 248nm stepper has been carried out. With binary masks the across-field CD- control for the 0.15micrometers isolated lines is not below 15nm in best focus. The use of sub-resolution assist features improved the across-field CD-uniformity as compared to the binary mask even in best focus. Over a limited focus range 150nm lines had a 3 sigma value below 15nm. It is expected that a higher NA will show this over an even larger focus range, making the assist feature sufficient for 0.15micrometers patterning with an adequate CD-control. For the 0.13micrometers lines alternating phase-shifting masks result in an across- field CD-variation below 13nm over a focus range of 0.4micrometers . For this work ,state-of-the-art reticles have been sued and no attempt was made to remove reticle CD errors from the CD-control data.