Co-sputter deposited Ta–Si diffusion barrier between Si and Cu: the effects of Si content on the barrier property

The barrier properties and failure mechanism of co-sputtered Ta-Si amorphous thin films of various concentrations were studied for the application as a Cu diffusion barrier in Cu metallization schemes. After annealing the Si/Ta-Si(30 nm)/Cu(100 nm)/Ta(100 nm) structures at temperatures from 500 to 600 degree C in an Ar-H sub(2)(10%) ambient for 1 h, the failure temperatures of Ta-Si barriers were determined using X-ray diffraction (XRD), Auger electron spectroscopy (AES) and cross-sectional transmission electron microscopy (XTEM). Ta sub(74)Si sub(26) and Ta sub(63)Si sub(37) amorphous barriers containing less Si than Ta sub(5)Si sub(3) undergo an abrupt failure between Si and Cu at 575 and 600 degree C, respectively, with the crystallization to tantalum silicides. However, Ta sub(60)Si sub(40) and Ta sub(56)Si sub(44) amorphous barriers containing more Si than Ta sub(5)Si sub(3) react with the Cu overlayer before the crystallization and form the Cu sub(3)Si precipitates at the local Ta-Si/Cu interface at 575 and 550 degree C, respectively. Among all compositions presented in this work, Ta sub(63)Si sub(37) was the most stable barrier between Si and Cu.