Abstract
Background: A local tilt angle of <300 mrad results in a critical dimension uniformity (CDU) impact below 0.1 nm when a pellicle is used for extreme ultraviolet (EUV) lithography. However, the thermomechanical property guidelines satisfying this specification have not yet been established. Aim: We present the thermomechanical property guidelines that yield a CDU impact below 0.1 nm. Approach: The peak temperature ranges of the EUV pellicle, as a function of the emissivity, were calculated through experimental, numerical, and finite element method analyses. The wrinkle profiles were evaluated as a function of the coefficient of thermal expansion (CTE) within these temperature ranges. The emissivity and CTE values satisfying the specifications were obtained using the CDU impact caused by the wrinkled EUV pellicle. Results: The wrinkle amplitude in the EUV pellicle exhibited 45% attenuation with a twofold decrease in the CTE. The maximum local tilt angles for the 17, 16, and 15 nm half-pitch patterns were 290.2, 286.1, and 272.3 mrad, respectively. CTE below 2 × 10 − 5 K − 1 and emissivity above 0.1 are suggested for the EUV pellicle. Conclusions: The CTE and emissivity guidelines satisfying the CDU impact specifications can be used for developing next-generation EUV pellicles.
Highlights
Even though the extreme ultraviolet transmittance (EUVT) and thermal stability of EUV pellicles have been improved, it is necessary to confirm the effect on the imaging performance when a EUV pellicle is employed in the lithography process.[1]
The coefficient of thermal expansion (CTE) and emissivity guidelines satisfying the critical dimension uniformity (CDU) impact specifications can be used for developing next-generation EUV pellicles
Because of the wrinkles formed in the EUV pellicle during the exposure, the critical dimension uniformity (CDU) impact can be limited to 0.1 nm by maintaining the local tilt angle below 300 mrad.[4]
Summary
Even though the extreme ultraviolet transmittance (EUVT) and thermal stability of EUV pellicles have been improved, it is necessary to confirm the effect on the imaging performance when a EUV pellicle is employed in the lithography process.[1] As the temperature of the EUV pellicle increases under EUV exposure, the corresponding slit area expands and forms a wrinkle.[1,2] This wrinkle induces EUVT nonuniformity because of the different EUV-light paths through the wrinkled EUV pellicle, impacting the imaging performance.[3] It was reported that, because of the wrinkles formed in the EUV pellicle during the exposure, the critical dimension uniformity (CDU) impact can be limited to 0.1 nm by maintaining the local tilt angle below 300 mrad.[4] the value of the local tilt angle has been specified, the corresponding thermomechanical property guidelines have not been reported.[5] Previous studies assumed a twodimensional wrinkle profile and an arbitrary period independent of the material properties of the EUV pellicle.[2,6]. The thermomechanical property guidelines satisfying this specification have not yet been established
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