Abstract
The imaging performance of an optical imaging system is difficult to quantify, even more so, to compare between different situations or systems. Though there exist physical parameters such as the contrast of the aerial image, the log slope of image intensity, the aberration coefficients of the imaging lens, the condenser apertures, the resist dissolution contrast, diffusion constant, resist processing parameters, and many others to define an imaging system, there are too many of them. It is desirable to have a single figure of merit to compare the performance implication of these parameters, to monitor and document the performance of a manufacturing line. This paper presents the linewidth-derived γ (LWD-γ) and LWD-η as single-figure lithography performance indicators. In addition to the need to quantify lithography performance universally, there is also a need to quickly convert a given aerial image to its resist image. We introduce LWD-γ to replace the conventional resist-development-based γ as a better parameter for use in the lumped parameter equations. We also introduce LWD-β to replace LWD-γ in low k 1 situations.