Fabrication of extreme ultraviolet lithography pellicle with nanometer-thick graphite film by sublimation of camphor supporting layer

Abstract

An extreme ultraviolet (EUV) pellicle consists of freestanding thin films on a frame; these films are tens of nanometers in thickness and can include Si, SiN X , or graphite. Nanometer-thick graphite films (NGFs), synthesized via chemical vapor deposition on a metal catalyst, are used as a pellicle material. The most common method to transfer NGFs onto a substrate or a frame is to use polymethyl methacrylate (PMMA) as a supporting layer. However, this PMMA-mediated technique involves several disadvantages in term of manufacturing NGF EUV pellicles. When removing the PMMA using acetone or O 2 plasma, defects or deflections can occur in the NGFs. Furthermore, PMMA residues are generally present on large-area NGFs. In this study, a transfer method using camphor instead of PMMA as the supporting layer was developed to overcome these problems. After the camphor/NGF was formed on the frame, camphor was removed via sublimation in an atmosphere of ethanol vapor. This study investigated the deposition and sublimation of camphor, and confirmed that no residue was present and no deflection or defects were observed in the NGFs. Thus, a large-area NGF pellicle was successfully fabricated using the camphor transfer process.

Development of nanometer-thick graphite film extreme ultraviolet pellicle with hydrogen-resistant TiN capping layer

“…Subsequently, CH 4 (100 sccm, total pressure up to 0.33 Torr) was introduced into the chamber at 900 °C and the system was maintained for 10 min. The NGF was synthesized on Ni using a natural cooling process without shutting off the gas flow (cooling rate of approximately 3 °C s −1 ) [17]. As shown in figure 1, TiN was not coated on the NGF in the form of a film, and the O 2 plasma pre-treatment was conducted at 100 W with a 100 sccm flow rate for 60 s. TiN was coated on the NGF/Ni/SiO 2 /Si wafer using TiCl 4 as the source material and NH 3 as the reactant gas.…”

“…Because the manufacturing process can change the chemical properties, a hydrogen evaluation sample was prepared using the same method as that for the NGF pellicle. The details of the camphor coating and stamping method are presented in a previously published paper [17].…”

“…It was confirmed that 20nm large-area freestanding (110 mm × 144 mm) NGF was successfully fabricated using Ni(110) film and camphor. On the basis of the research results, we carried out our investigation to improve the mechanical and chemical properties of NGF [13][14][15][16][17]. In this study, hydrogen resistance was improved by manufacturing titanium nitride (TiN) on an NGF using atomic layer deposition (ALD).…”

“…However, preparation of free-standing samples through the back-etching process is difficult for NGF pellicle because NGFs are grown on Ni thin films. A free-standing 20 nm thick NGF was prepared in a previous study without a back-etching process [17]. In this study, Ni was sputtered on an eight-inch SiO 2 wafer.…”

Fabrication of a 100 × 100 mm2 nanometer-thick graphite pellicle for extreme ultraviolet lithography by a peel-off and camphor-supported transfer approach

“…Therefore, for large freestanding samples that exceeding 50 × 50 mm 2 , PMMA cannot be removed with acetone and require to use O 2 plasma treatment. However, the method of removing PMMA with O 2 plasma treatment still leaves PMMA residues on the NGF surface and also causes additional defects and deflection in free-standing NGF 18 . The way to solve various problems caused by using PMMA as a supporting layer is to use sublimable substances such as anthracene 19,20 , naphthalene 21 , and camphor [22][23][24] .…”