ILT for double exposure lithography with conventional and novel materials

Abstract

Multiple paths exists to provide lithography solutions pursuant to Moore's Law for next 3-5 generations of technology, yet each of those paths inevitably leads to solutions eventually requiring patterning at k 1 < 0.30 and below. In this article, we explore double exposure single development lithography for k 1 ≥ 0.25 (using conventional resist) and k 1 < 0.25 (using new out-of-sight out-of-mind materials). For the case of k 1 ≥ 0.25, we propose a novel double exposure inverse lithography technique (ILT) to split the pattern. Our algorithm is based on our earlier proposed single exposure ILT framework, and works by decomposing the aerial image (instead of the target pattern) into two parts. It also resolves the phase conflicts automatically as part of the decomposition, and the combined aerial image obtained using the estimated masks has a superior contrast.For the case of k 1 < 0.25, we focus on analyzing the use of various dual patterning techniques enabled by the use of hypothetic materials with properties that allow for the violation of the linear superposition of intensities from the two exposures. We investigate the possible use of two materials: contrast enhancement layer (CEL) and two-photon absorption resists. We propose a mathematical model for CEL, define its characteristic properties, and derive fundamental bounds on the improvement in image log-slope. Simulation results demonstrate that double exposure single development lithography using CEL enables printing 80nm gratings using dry lithography. We also combine ILT, CEL, and DEL to synthesize 2-D patterns with k 1 = 0.185. Finally, we discuss the viability of two-photon absorption resists for double exposure lithography.

Double-exposure materials for pitch division with 193nm lithography: requirements, results

“…In order to allow for straightforward analytical solutions, for now we assume no variation in material absorption throughout the depth of the photoresist (that is no photobleaching during the exposure process). The rate equations are given below (2 …”

“…However, as will be explained below, such a material must possess a strong non-reciprocal photoresponse. While the usefulness of such materials that lack dose reciprocity was highlighted sometime ago [2,3], the verification of such behavior at 193nm to the extent necessary for practical application has yet to be reported. In this paper, we present our results from exploring the feasibility of formulation and use for two different classes of such materials: reversible Contrast Enhancement Layers (rCEL) and Two-Stage Photo Acid Generators (Two-Stage PAGs).…”

Massively-parallel FDTD simulations to address mask electromagnetic effects in hyper-NA immersion lithography

“…Interest in CPL masks has risen as part of the Computational Technology (CT) development effort because they constitute the most efficient phase shifting masks for the advanced optimization of the illumination source and the mask layout. 10,11 Large values of the BL imaginary transmission combined with significant BL widths indicate however, that this mask suffers from pronounced distortions through focus and overall severe EMF effects as is well known for these type of masks. 12 Therefore rigorous electromagnetic simulations become necessary.…”

Pixelated phase mask as novel lithography RET

“…Yet it is remains to be seen if it will find significant use in the manufacturing environment as both ILT and PPM technologies are complex, relatively immature and might be at the limits of their usefulness in support of single exposure patterning for 22nm node for logic products. Its extension to double patterning is possible [5,6] yet its use there is not assured either due to its relative complexity as compared to many other methods suggested in support of the pitch division to be used in support of future IC manufacturing with 193nm exposure tools.…”