Erik Sohmen

Update on the SEMATECH 0.5 NA Extreme-Ultraviolet Lithography (EUVL) Microfield Exposure Tool (MET)

In support of the Extreme Ultraviolet Lithography (EUVL) roadmap, a SEMATECH/CNSE joint program is underway to produce multiple EUVL (wavelength of 13.5 nm) R&D photolithography tools. The 0.5 NA projection optic magnification (5X), track length and mechanical interfaces match the currently installed 0.3 NA micro-field exposure tools (MET) projection optic [1] [2] [3]. Therefore, significant changes to the current tool platforms and other adjacent modules are not necessary. However, many of the existing systems do need upgrades to achieve the anticipated smaller exposure feature sizes [4]. To date we have made considerable progress in the production of the first of the two-mirror 0.5 NA projection optics for EUVL [5]. With a measured transmitted wave front error of less than 1 nm root mean square (RMS) over its 30 μm × 200 μm image field, lithography modeling shows that a predicted resolution of ≤12 nm and an ultimate resolution of 8 nm (with extreme dipole illumination) will be possible. This paper will present an update from the 0.5 NA EUVL program. We will detail the more significant activities that are being undertaken to upgrade the MET and discuss expected performance.

Aerial image improvements on the Intel MET

Since its installment in 2004, Intels extreme ultraviolet (EUV) micro-exposure tool (MET) has demonstrated significant improvements in ultimate resolution capability. Initially capable of printing 45nm half-pitch (HP) lines with a 160nm depth of focus (DOF), it is now capable of printing 22nm HP lines with up to a 275nm DOF and demonstrating modulation down to 18nm HP. Initial improvements in resolution have been chiefly attributable to the maturation of EUV masks and photoresists. Recent improvements that have enabled the 22nm HP imaging with a sizeable process window are largely due to new illumination options that have become available as a result of recent tool upgrades. In particular, the installation of a new nested Wolter collector with an additional outer shell that extended the maximum partial coherence (σ) from 0.55 to 0.68, in conjunction with an updated pupil wheel and apertures, has enabled new rotated quadrapole and on-axis dipole illumination settings with 0.36 inner σ and 0.68 outer σ. Here we present simulated contrast curves alongside the experimental imaging results for the Intel MET using the newly available quadrapole and on-axis dipole illumination settings and discuss our future plans for continued improvements to the Intel MET aerial image.