Characterization of TiN/TiSi2 bilayer formed by sputter deposition from a TiN0.4 alloy target and subsequent lamp annealing and its application to a contact system

Abstract

AbstractTo develop a thermally stable barrier metal for interconnections in LSI, films deposited by sputtering a Ti‐rich TiN0.4 target were investigated (in what follows, the film deposited in this manner will be referred to as TiN0.4). Both film quality and the electrical property of the Al‐alloy/Si contact with thin barrier metal were evaluated. It was found that the TiN layer formed by this method was twice as thick as the TiN layer formed by the conventional method, the TiN/TiSi2 layer formed was smooth and the silicide layer was five times thinner than when the conventional method was used. The TiN layer formed by nitridation of TiN0.4 (50 nm)/Si had a grain structure with a grain size of approximately 10 nm and was strongly oriented to TiN (200). In the silicide layer, the grain size was approximately 50 nm and a semistable phase was formed. It was also found that contact resistance to N+Si was similar to that formed by using the conventional Ti nitridation method while the contact resistance to P+Si was slightly lower than when the conventional method was used. In addition, it was found that the contact resistance became lowest when the rapid thermal nitridation (RTN) temperature was approximately 700°C and the formed film was stable when it was thermally treated. When a Ti layer was used, the N+/P junction showed a leakage problem after it was annealed at temperatures higher than 450°C. However, when TiN0.4 was used, no leakage problem was observed even when the junction was annealed at 525 °C. These superior junction characteristics were due to the thermally stable and thick TiN layer.