Study on Transition Metal Nitride Used as a Diffusion Barrier in Silicon Devices

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It becomes very urgent problem to suppress interdiffusion between the semiconductor Si and the contact metal Al, because interdiffusion of them leads to fracture of the p-n junction and brittleness of contacts. Present study aims tofind whether Ti an TiN are effective as a diffusion barrier between Si and Al.Results are as follows. (1) In the Al/Ti/Si system, the Ti film with the (0002) texture is better to supress interdiffusion at 400゜C than that without the texture. Further, the former is more adhesive to the Si substrate an high temperatures. (2) The TiN file is very excellent diffusion barrier to Al as high as the melting point of Al. (3) In the TiN/Si system, the TiN film does not peel off from the Si substrate as high as 1000゜C The films with N/Ti=0.9 do not change their structure by heating. But those with N/Ti=0.8 and 0.5 change their structure near the interface between Si and TiN, firstly to metastable TiSi_2 (C49) and next to stable TiSi_2 (C54). At the same time, N/Ti near the surface approaches unit. (4) Films with N/Ti close to unit show small sheet resistance. Those with N/Ti=1 and0.8 decrease their sheet resistance to the level of films with N/Ti=1 resulted from the formation of TiSi_2 at the interface. (5) In conclusion, the TiN film can be an excellent diffusion barrier not only to the Al contact, but also to the n-type and p-type Si.