High transmission pellicles for extreme ultraviolet lithography reticle protection

Abstract

The authors present the results of a full-field extreme ultraviolet (EUV) pellicle for reticle protection and defect mitigation. Based on novel microelectromechanical systems based fabrication, it comprises a 50 nm Si membrane attached to a wire-grid. Two types of pellicle fabrication techniques are described. The authors present the first actinic results of extreme ultraviolet lithography reticle with pellicle exposed on IMEC Advanced Demo Tool. The impact of different pellicle types on imaging is evaluated as a function of pellicle standoff distance and mesh geometry. A new prototype pellicle has been developed with a measured transmission of 82% in EUV. Actinic exposures are complemented with aerial image modeling, thermal analysis, vacuum cycling, resist outgas tests, and >5 g repeated scan cycle robustness tests.

Large-scale freestanding nanometer-thick graphite pellicles for mass production of nanodevices beyond 10 nm

“…1a. The EUV transmission of the freestanding NGF with a thickness of 18 nm was 92% (51% @ 550 nm), which was the best EUV transmission among the EUV pellicles using Si and other thin films, 6,8,10 and represents excellent optical properties and shows the feasibility of NGF for EUV pellicles. The correlation between the transmission at the EUV and visible light wavelengths suggests a convenient way to assess the EUV transmission from visible light transmission.…”

“…6 Based on these strict requirements of EUVL pellicles, freestanding thin films composed of several different materials, including Si, Ru, Mo, and Nb, have been investigated. 6,8,10 Among them, a 60 nm thick Si-based pellicle with a size of 110 × 140 mm showed the highest EUV transmission of ∼85%. 6,9 However, it was crippled by the high temperature induced by EUV irradiation with a power density of 5 W cm −2 due to the low thermal conductivity and reduced emissivity of the very thin Si layer.…”

Impact of the non-uniform intensity distribution caused by a meshed pellicle of extreme ultraviolet lithography

“…Unfortunately, the extremely thin film can easily sag and be damaged in the exposure process due to gravitational force and the accelerating force of the scanner [10,11]. Thus, a mesh-supported pellicle is suggested to stabilize the thin film during the process [12][13][14][15][16][17]. A hexagonal-shaped mesh has the highest rigidity and largest open area among various shapes including rectangles or triangles.…”

Protection of extreme ultraviolet lithography masks. I. Thermophoretic protection factors at low pressure for diffusing nanoscale particles

“…Although particle deposition probabilities were not calculated, the studies did suggest a steadily decreasing effectiveness of thermophoretic protection as the particles became more diffusive with decreasing size. Much work has been devoted to understanding the EUV transmission of such an assembly, 23,25 differential radiative heating of the supported film and mesh (which can lead to wrinkling), 26,28 and the effect of the Ni mesh on EUV image quality. Sogard has patented several mask protection approaches involving thermophoresis.…”