Impact of thermal expansion coefficient on the local tilt angle of extreme ultraviolet pellicle

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.