Molybdenum carbide pellicle for high-power EUV lithography

Abstract

As the power of EUVL (extreme ultraviolet lithography) scanners increases, the thermal load and hydrogen plasma environment applied to the pellicle become harsher. If the core material of the pellicle membrane is unstable in the EUV environment, reliability depends on the top-most layer (capping). However, the loss of EUV transmission restricts the thickness of the capping and raises concerns related to hydrogen radicals or protons. In our previous report, we introduced molybdenum carbide (Mo2C) as a new pellicle material with high EUV transmittance (91.4 %), transmission uniformity (3ρ=0.49 %, 5 × 5 mm2), and chemical stability against a hydrogen plasma. 1 In this report, we demonstrate the stability against high-intensity (30 W/cm2) EUV irradiation and hydrogen plasma for Mo2C membranes. Large-Area (≥5 × 5 cm2) Mo2C membranes with high EUV transmittance (≥88 %) were fabricated using MEMS technology. The membranes were tested for thermal load test using an 808 nm infrared laser under the same conditions producing up to 3000 wafers in the EUV scanner. The chemical properties of the membranes were evaluated using an inductively coupled plasma device in a high-Temperature (<900 °C) hydrogen gas and plasma environment. Furthermore, the EUV transmittance for the Mo2C membrane and the difference after thermal load and hydrogen plasma evaluation were characterized by EUV coherence scattering microscopy. Consequently, we show the feasibility of high-volume manufacturing (HVM) Mo2C pellicles by fabricating the membrane over 5 × 5 cm2.