Intra-field effects on device and circuit manufacturability: a statistical simulation approach

Abstract

In spite of the numerous improvements in deep ultraviolet (DUV) lithography, minimizing lens aberrations remains critical to obtaining manufacturable logic technologies. In this paper, we investigate the effects of lens imperfections on the distributions of process, device, and circuit parameters. Lens imperfections, as manifested by intrafield gate critical dimension (CD) variations, can affect device and circuit parameters strongly. The latter is central to designing fast high-yielding logic products, especially microprocessors. Our approach employs process, device, and statistical simulations, coupled with extensive calibration, to predict manufacturing distributions for a new technology well before it is ramped to full-scale production. We study nominal channel length n- and p-channel devices, inverter ring oscillators, and four-input NAND standard cells, We compare different stepper conditions both for conventional and annular illumination. We consider the case of more than one die in a reticle field and investigate how lens imperfections affects different dice therein. We apply our approach to an experimental DUV stepper and demonstrate coma effects that potentially lower yields. Our results also include a paradox: the best annular illumination case, which betters the CD distributions of conventional illumination, ultimately yields worse circuit performance.