Investigating the Degradation of EUV Transmittance of an EUV Pellicle Membrane

Abstract

The extreme ultraviolet (EUV) pellicle is a freestanding membrane that protects EUV masks from particle contamination during EUV exposure. Although a high EUV transmittance of the pellicle is required to minimize the loss of throughput, the degradation of EUV transmittance during the extended exposure of the pellicle has been recently reported. This may adversely affect the throughput of the lithography process. However, the cause of this phenomenon has not yet been clarified. Therefore, we investigated the cause of the degradation in the EUV transmittance by observing the compositional change when the Ru/SiNx pellicle composite was heated in an emulated EUV scanner environment. The Ru thin film that was deposited at high pressure had more void networks but was not oxidized, whereas the SiNx thin film was oxidized after heating. This was because the void network in the Ru thin film served as a preferential diffusion path for oxygen and caused oxidation of the SiNx thin film. It was confirmed that the degradation of the EUV transmittance was due to the oxidation of SiNx. The results verified the effect of diffusivity in the thin film due to the void network on oxidation and EUV transmittance.

Study on ZrSi2 as a Candidate Material for Extreme Ultraviolet Pellicles

“…The EUV transmittance was derived by comparing the number of photons reflected by the Mo/Si multilayers with and without the pellicle. The EUV reflectivity was calculated by comparing the number of photons reflected by the EUV pellicle when it was mounted on an absorber material where the EUV reflectivity converges to zero, with the number of photons reflected by the Mo/Si multilayers [ 22 , 23 , 24 ].…”

Transverse Deflection for Extreme Ultraviolet Pellicles

“…Carbon nanotube (CNT) pellicles [10,11] with a porous structure and a nanometer-thick graphite film [12,13] as a monolayer-strong mechanical material have been developed by the IMEC company [14]. In particular, transverse deflection for EUV pellicles can locally influence pattern formations, such as critical dimension uniformity (CDU) and the lifetime of EUV masks [15]. Hence, understanding and analyzing transverse deflection of EUV pellicles are important for future EUV projection systems [16][17][18][19][20].…”