Recent Advancements in EUV Resist Materials and Process Performance

Abstract

Resist ability to simultaneously meet the requirements for Resolution, LER and Sensitivity (RLS) remains one of the critical issues EUV Lithography is facing. As good progress in resolution and sensitivity have been made, nowadays LER and pattern collapse are considered as the two main items requiring improvement. In this paper, the current performance of EUV resist on the ASML ADT is reviewed and the effectiveness of process improvements for pattern collapse and LER reduction has been investigated. Results are presented of EUV resist screening for sub-28nm LS and 30nm contact holes on the ASML ADT to prepare for a resist process on the pre-production tool NXE:3100, currently under installation at imec. Acceptable resist performance was obtained for 28nm LS with some of the new resist materials outperforming the current imec reference resist in terms of LER. By applying a 20% mask bias, imaging of 30nm contacts at <14mJ/cm 2 with wide processing latitudes was achieved. Local variation of contact CD however is a serious limitation at smaller contact sizes. The use of TBAH developer and the application of FIRM rinse were found to be effective to reduce pattern collapse and to extend processing windows. With the FIRM rinse in addition LER was improved. Finally the feasibility of printing 22nm LS at 13mJ/cm 2 with 4.7nm LER have been demonstrated on the NXE:3100 using dipole illumination.

Resist Materials and Processes for Extreme Ultraviolet Lithography

“…119) Reports have shown that improvements of LWR 119) and sensitivity 14) can be achieved for certain resists with this developer. One mechanism proposed to define the reason for this resist selectivity with TBAH is the existence of the resist surface modification phenomenon when using this developer.…”

“…Such collaborations have led to the investigation and realization of new and exciting resist platforms 5,[11][12][13] and processes. 3,14,15) These works have also shown a number of issues and challenges that need to be considered as the semiconductor industry moves to more stringent technology nodes. 16) Against this background of such international collaboration, the EUVL symposium has been organized every year by SEMATECH, IMEC, and Selete (later EIDEC).…”

Directed Self Assembly Material Development for Fine Patterning and Pattern Repair

“…Self Aligned Double Patterning [4] for 3x nm and 2x nm. Further size reduction requires triple or quadruple patterning, and it causes huge increase of CoO and the difficulty of overlay [5] Extreme ultraviolet (EUV) lithography has been the favorite candidate of successor of immersion ArF [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] [26][27][28][29][30][31][32][33][34]. Application of DSA materials may extend immersion ArF and support the rise of EUV.…”

Dissolution Characteristics of EUV Resist by High Speed AFM

“…have shown potential results. For resist related processes; non-conventional baking methods [8] , developer [8][9][10][11] , and rinse solutions [9][10][11] have been proposed to further improve the lithographic performance of presently available resists. This shift to new resist materials / processes suggests the need for more fundamental studies in better understanding and achieving the stringent targets required.…”