Electrical reliability issues of integrating thin Ta and TaN barriers withCu and low-K dielectric

This work investigates the integration of very thin sputtered Ta and reacti vely sputtered TaN barriers with Cu and a low-dielectric-constant (low-K) l ayer of poly(arylene ether) (PAE-2). It is found that Cu readily penetrates into PAE-2 and degrades its dielectric strength in metal-insulator semicon ductor capacitors of Cu/PAE-2/Si structure at temperatures as low as 200 de grees C. Very thin Ta and TaN films of 25 nm thickness sandwiched between C u and the low-K dielectric served as effective barriers during a 30 min the rmal annealing at temperatures up to 400 and 450 degrees C, respectively. W e propose a failure mechanism of outgassing induced gaseous stress of PAE-2 under the Ta film to explain its premature barrier degradation. The TaN ba rrier did not suffer from this gaseous stress problem because of its strong er adhesion to PAE-2 than that of Ta to PAE-2, leading to a better long-ter m reliability. (C) 1999 The Electrochemical Society. S0013-4651(99)04-046-X . All rights reserved.