Electrical characterization of TiN/TiSi2 and WN/TiSi2 Cu-diffusion barriers using Schottky diodes

For application of copper in contact level metallization, diffusion barriers between Cu and Si are indispensable. As copper can cause serious deterioration to device performance when diffusion through the barrier occurs, characterization of barrier stability requires extremely sensitive methods for detection of copper. For that purpose, reactively sputtered TiN and WN barriers on SALICIDE TiSi2 contacts were intensively investigated using capacitance-voltage (C-V) and current-voltage (I-V) measurement on Schottky diode test structures. The results are compared to simultaneously fabricated nip junction test structures. It is shown that Schottky diode test structures provide early and simple detection of barrier failure, by alteration of the electrical barrier height and by additional diode capacitances. The determined failure temperatures are 600-700 degrees C for TiN/TiSi2 and 600-800 degrees C for WN/TiSi2, depending on the test structure applied. Lower failure temperatures always refer to Schottky diode test structures. The additional capacitances which appear along with barrier failure are significantly frequency and temperature dependent.