Diffusion of silicon in titanium nitride films. Efficiency of TiN barrier layers

Abstract

Abstract. Two kinds of reactively evaporated titanium nitilde films with columnar (/3o films) and fine-grained film structure (B+ films) have been examined as diffusion barriers, preventing the silicon diffusion in silicon devices. The silicon diffusion profiles have been investigated by 2 MeV 4He+ Rutherford backscattering spectrometry (RBS) after annealing at temperatures up to 900 ° C, in view of application of high-temperature processes. The diffusivity from 400 to 900 ° C: D (m 2 s -x) = 2.5 x 10 -18 exp[-31 kJ/mol/ (RT)] in B0 layers and D (m 2 s -1) = 3 x 10 -19 e x p [ -2 6 k J / mol/(RT) in B+ TiN layers. The diffusivities determined correspond to grain boundary diffusion, the difference being due to the different microstructure. The very low diffusivity of silicon in B+ TiN layer makes it an excellent high-temperature barrier preventing silicon diffusion. 66.30.-h, 73.40.-c There has been considerable interest, since the early eighties, in refractory metal nitride films, especially in titanium nitride, investigated for applications in the microelectronics industry [1][2][3][4][5][6][7]. Titanium nitride thin films have been reported to be of interest in silicon technology particularly as a diffusion barrier allowing the achievement of thermally stable and reliable contacts as well in integrated circuits as in solar cells [8][9][10][11][12][13]. Lately thermally stable contact and metallization technologies are becoming increasingly important for advanced VLSI where high-temperature processes are applied and annealing temperatures could reach 1000 ° C. PACS:The general requirement of an effective contact barrier layer in the above mentioned cases consists of preventing an interaction between metal (contact material) and silicon in metallization schemes undergoing high temperature processing and annealing. There are two interfaces where thermal stability must be ensured, namely the metal/barrier layer and the barrier layer/silicon interfaces. The barrier layer should interact not at all or only slightly with the contact metal and the underlying silicon. No matter which contact material is used the interdiffusion at the barrier layer (in that case titanium nitride)/silicon interface remains of constant interest. The silicon diffusivity in the titanium nitride characterizes in an explicit and precise manner the barrier thermal stability at that interface. Nevertheless, we are not aware of studies having as objective the determination of the silicon diffusivity in TiN layers. In the comparatively large number of papers dealing with properties and applications of TiN its barrier performance has been investigated and estimated in a more or less indirect way on the basis of test structures and qualitative interpretation of RBS and AES spectra. The present paper deals with a quantitative determination of the silicon diffusion in TiN, achieved through RBS depth profiling of the diffused silicon in TiN layers with different types of microstructure which exhibit different permeability for the silicon atoms. Tita...

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Low Reversible Capacity of Nitridated Titanium Electrical Terminals

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