Sputter deposition and annealing of Ta, TaSix and TaBx composite films andtheir application in next generation lithography masks

Ta and Ta composites with other elements have been developed as low stress absorbers for x-ray mask technology. These thin films are often produced in small quantities by sputter deposition from targets of pure Ta with chips of the minor elements placed on the target to create the composites. For me mbrane-mask manufacturing it is important that absorber films have uniform composition, thickness, and low, uniform stress to assure that image size a nd pattern placement errors are minimal. Since sputtered films containing T a often have highly compressive stress, several methods have been used to r educe the final stress, including careful control of sputtering conditions, deposition of layered films with different stresses, and thermal annealing . Much data has been reported regarding the effects of thermal annealing of Ta films but less information is available on multiple element films such as TaSix and TaBx. Previous reports on these materials have generally not d iscussed the behavior of these films under long term, higher volume manufac turing conditions. During the last several years IBM has been engaged in de velopment and fabrication of refractory x-ray membrane masks using Ta compo sites as absorber materials. Films were sputter deposited from hot isostati cally pressed powder targets of Ta, Si, and B using an S-gun magnetron clus ter deposition system. This article reports on the deposition and annealing of these films and their application to membrane-mask fabrication in a man ufacturing environment. The effects of deposition parameters such as de pow er, argon gas pressure, and substrate composition on film stress, compositi on, and density are discussed. The results of nitrogen annealing on TaSix a nd TaBx films are presented. Absorber film quality data and its impact on i mage size, image placement, and defect density of some x-ray masks is prese nted. (C) 2000 American Vacuum Society. [S0734-2101(00)05604-9].