Electrical Reliability Issues of Integrating Thin Ta and TaN Barriers with Cu and Low‐K Dielectric

Abstract

This work investigates the integration of very thin sputtered Ta and reactively sputtered TaN barriers with Cu and a low‐dielectricconstant (low‐K) layer of poly(arylene ether) (PAE‐2). It is found that Cu readily penetrates into PAE‐2 and degrades its dielectric strength in metal‐insulator semiconductor capacitors of Cu/PAE‐2/Si structure at temperatures as low as 200°C. Very thin Ta and TaN films of 25 nm thickness sandwiched between Cu and the low‐K dielectric served as effective barriers during a 30 min thermal annealing at temperatures up to 400 and 450°C, respectively. We propose a failure mechanism of outgassing induced gaseous stress of PAE‐2 under the Ta film to explain its premature barrier degradation. The TaN barrier did not suffer from this gaseous stress problem because of its stronger adhesion to PAE‐2 than that of Ta to PAE‐2, leading to a better long‐term reliability. © 1999 The Electrochemical Society. All rights reserved.