| AVS 55th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Tuesday Sessions |
| Session NS-TuP |
| Session: | Poster Session |
| Presenter: | H.Y. Kang, Inha University, Republic of Korea |
| Authors: | H.Y. Kang, Inha University, Republic of Korea M.K. Kim, Inha University, Republic of Korea C.K. Hwangbo, Inha University, Republic of Korea |
| Correspondent: | Click to Email |
The lithography performance of extreme ultraviolet lithography (EUVL) mask depends on the correct choice of absorber materials because it is directly related to imaging contrast, shadowing effect, focus shift effect, and thermal effect.1 The optical constant of the absorber materials in the EUV region should have higher extinction coefficient for higher attenuation. Also, the absorber material should exhibit good conductivity, which can alleviate the charging effect during electron-beam patterning. In the past, a wide range of materials (Ti, TiN, Al–Cu, TaSi, Ta, TaN, Cr, etc) has been evaluated as possible conductive absorbing materials for EUVL mask.2,3 The total thickness of the absorber stack by using the materials used to be greater than 80 nm because the available absorbing materials are limited and an anti-reflection coating is necessary to maximize pattern inspection efficiency at deep ultraviolet wavelength. It is reported that the large thickness of the absorber stack may cause a geometric shadow effect in an exposure step and as a result, the printed patterns are shifted and biased.4 In this study, we propose a new absorber stack with a silver doped zinc oxide absorber layer. The optical constants of ZnO layers with various concentration of Ag at 13.5 nm are calculated. It is found that the optical constants of ZnO layers with high concentration of Ag show lower refractive index and higher extinction coefficient at 13.5 nm than those of TaN layer. Thus ZnO layers doped with Ag enables EUVL masks to be designed to have very small height difference between high reflecting and absorbing stacks, suggesting that the geometric shadow effect can be significantly reduced.
1 P. Yan, Pro. SPIE 4688, 150-160 (2002).
2 J. Y. Robic, P. Schiavone, V. Rodillon, R. Payerne, Microelectronic Eng 61–62, 257–263 (2002).
3 P. Mangat, S. Hectora, S. Rosea, G. Cardinaleb, E. Tejnil, A. Stiverse, Proc. SPIE 3997, 76 (2000).
4 M. Goethals, R. Jonckheere, G. F. Lorusso, J. Hermans, and F. Van Roey, Proc. SPIE 6517, 651709 (2007).