The effect of the Ti glue layer in an integrated Ti/TiN/Ti/AlSiCu/TiN contact metallization process

Abstract

A Ti/TiN bilayer deposited under an Ti/AlSiCu/TiN interconnect is generally used at the contact level to stabilize the contact resistance of small diameter contacts as well as to prevent junction spiking during postdeposition anneals. An air break followed by a furnace or a RTP anneal is generally required after the deposition of the Ti/TiN bilayer to improve the barrier stability. This three step interconnect scheme results in a low net effective throughput process if the same metallization system is used twice or, alternatively, in a high cost-of-ownership process if two metallization systems are used, a first for the Ti/TiN barrier and a second for the Ti/AlSiCu/TiN interconnect. In this article, it is shown that collimation permits the deposition of very thick TiN barriers at the bottom of high aspect ratio contacts which allows contact metallization integration in a single metallization system. In addition, it is found that the use of a Ti glue layer between the barrier and the AlSiCu contact interconnect to promote the filling of these high aspect ratio contacts with Al alloys results in a yield loss of n+ and p+ contact chains and therefore should be avoided. Finally, it is demonstrated that an integrated Ti/TiN/AlSiCu/TiN contact metallization with excellent electrical properties is possible with collimated TiN barriers.