0026-2714/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.microrel.2005.07.045 Microelectronics Reliability 45 (2005) 1449–1454 www.elsevier.com/locate/microrel Effect of vacuum break after the barrier layer deposition on the electromigration performance of aluminum based line interconnects Cher Ming Tan a, * , Arijit Roy a , Kok Tong Tan b , Derek Sim Kwang Ye b , Frankie Low b a School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639 798 b Failure Analysis and Reliability Section, Systems on Silicon Manufacturing Co. Pte. Ltd., 70 Pasir Ris Industrial Drive 1, Singapore 519 527 Abstract Electromigration (EM) experiments have been performed for aluminum (Al) based interconnect of samples with and without air exposure after barrier layer deposition and prior to aluminum deposition. The intention of air exposure is normally performed to improve the efficiency of barrier layer against the Al diffusion. However, the EM performance of such air exposed samples is found to be controversial. It has been found that in the case of highly accelerated tests, the EM life-time decreases and failure rate increases for the samples with air exposure, while these variations has been found to be negligible in the case of moderate accelerated tests. Finite element analyses reveal that high temperature gradient exists in the metallization at highly accelerated test and this gradient enhances the atomic flux divergence due to triple point formed by titanium nitride, titanium oxide and aluminum. * Corresponding author. ecmtan@ntu.edu.sg Tel: +(65) 6790 4567; Fax: +(65) 6792 0415 1. Introduction Dramatic improvement in EM life-time is achieved by the incorporation of barrier layer into the interconnect metallization. Barrier layer is used in interconnect metallization for two purposes. Firstly, the barrier layer protects metal diffusion into the surrounding dielectric and secondly, the barrier layer serves as an alternative current path during the void growth in EM. Titanium (Ti) is one of the promising metal used for barrier layer in Al based interconnection. Since TiN and Al are both of fcc lattice structure and of similar lattice constant (e.g., TiN: 0.424 nm, Al: 0.405 nm) [1,2], TiN layer is usually formed on top of Ti layer to prevent Ti and Al interdiffusion. However, oxygen incorporation into the TiN layer is needed to effectively protect this interdiffusion [3]. As a result, chamber vacuum break prior to Al deposition was proposed to create an effective diffusion barrier layer. On the other hand, to improve EM life-time, the grain orientation of TiN layer should be <111> so that Al can grow on it in the preferred <111> orientation normal to the film surface [4,5]. However, the preferred texture quality of Al is found to be difficult to achieve in the presence of TiN as underlayer [6]. Atakov [7] reported that TiN underlayer reduces Al-alloy EM resistance but it improves EM resistance Ó 2005 Elsevier Ltd. All rights reserved.