Tunable transmission phase mask options for 65/45nm node gate and contact processing

Today the industry is filled with intensity-balanced c:PSM and much more focus is being placed on innovative approaches such as CPL (and in conjunction with IML for Contacts) and tunable transmission embedded attenuating phase shift mask (TT-EAPSM). Each approach has its own merits and demerits depending on the manufacturing strategy and lithography performance required. Currently the only commercially available photomask blanks are different chrome thickness binary and 6% attenuating blanks using molybdenum-silicide, making the accessibility to alternate transmissions much more challenging. This paper investigates the mask manufacturability of a tunable transmission embedded attenuating phase shift mask. New film materials that are used in the mask blank manufacture are modeled, deposited and characterized to determine its ability to meet performance requirements. Sputtering models, by rate and gas component, determines film stacks with tunable transmissions and thicknesses. Chemical durability, etch selectivity and thickness are a few parameters of the films that have been characterized to enhance the manufacturability and process reliability of the masks. Lithography simulation models using measured optical properties were developed and test masks that include actual device designs were fabricated. Analysis of CD variation, pattern fidelity and process margin was performed using 3D mask simulation to understand the impact on 65nm design rules. Feasibility and performance of tunable transmission photomasks for use in design and lithography are verified. Moreover, the mask manufacturability and lithography performance is compared to other enhancement techniques and their merits presented.

[1]  Will Conley,et al.  High transmission mask technology for 45nm node imaging , 2006, SPIE Advanced Lithography.