Laser ablation patterning of dielectric layer stacks for 193-nm mask fabricaton

Juergen Ihlemann; Katharina Rubahn; Roland Thielsch

doi:10.1117/12.456875

25 February 2002 Laser ablation patterning of dielectric layer stacks for 193-nm mask fabricaton

Juergen Ihlemann, Katharina Rubahn, Roland Thielsch

Proceedings Volume 4426, Second International Symposium on Laser Precision Microfabrication; (2002) https://doi.org/10.1117/12.456875
Event: Second International Symposium on Laser Precision Micromachining, 2001, Singapore, Singapore

Abstract

Fabrication of dielectric optical masks by ablation patterning using a 193 nm laser is demonstrated. Ablation of layer systems that are highly reflective at 193 nm (HR 193nm) is accomplished by using an absorbing layer to initiate ablation. This absorbing layer is deposited on the substrate under the HR system. Thus it is possible to induce spatially defined ablation of the whole stack by irradiating the absorbing layer through the substrate (rear side ablation). Using the system as a mask, i.e. irradiating it from the front side, the reflective layer system prevents penetration of high fluence radiation to the absorbing layer, so that the function of the reflective mask is not restricted. A HR 193 nm system, composed of 42 layers, alternating Al₂)₃ and SiO₂ was prepared. The substrate was fused silica. For the absorbing layer (a) HfO₂ and (b) SiO_x (x<2) of about 30 nm thickness were used. In the case of HfO₂, residual fragments of the absorbing layer diminish the transmission in the ablated areas. In the case of SiO_x, which is absorbing at 193 nm for x<2, these residuals can be oxidized to SiO₂ has high transmission at 193 nm improving the mask performance. For the ablation process single pulse irradiation with a fluence of about 800 mJ/cm² is sufficient. The mask has a damage threshold of >1 J/cm².

Citation Download Citation

Juergen Ihlemann, Katharina Rubahn, and Roland Thielsch "Laser ablation patterning of dielectric layer stacks for 193-nm mask fabricaton", Proc. SPIE 4426, Second International Symposium on Laser Precision Microfabrication, (25 February 2002); https://doi.org/10.1117/12.456875

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