Bias sputtered Ta modified diffusion barrier in Cu/Ta(Vb)/Si(111) structures

In this investigation, we have fabricated Ta(V-b)/Si(111) and Cu/Ta(V-b)/Si(111) systems using a DC bias sputtering technique at high Ar pressure (100 mTorr). For Ta/Si(111) system, tantalum layer was formed under various bias voltages ranging from 0 to -150 V. The films were characterized by Rutherford bacbscattering spectrometry (RBS), scanning electron microscopy (SEM) and four-point probe sheet resistance measurements (R-s). From electrical resistivity and SEM data, a minimum resistivity (99 mu Omega cm) and well surface morphology at an optimum bias voltage (V-b = -50 V) was obtained for the Ta(Vb)/Si(lll) system, The Ta films deposited under these conditions with 50 nm thickness are then used as a diffusion barrier in the Cu/Ta(V-b)/Si(111) multilayer structure. According to our RES, SEM and R-s analysis, the Ta barrier layer formed under the controlled bias sputtering at high Ar pressure has demonstrated an improved Ta structure with excellent thermal stability up to 650 degrees C for the Cu/Ta(Vb)/Si(111) system annealed in N-2 environment for 30 min. Formation of TaSi2 was observed at 700 degrees C after the barrier failure using RES spectra. (C) 2000 Elsevier Science S.A. All rights reserved.