NITRIDATION OF FINE-GRAIN CHEMICAL-VAPOR-DEPOSITED TUNGSTEN FILM AS DIFFUSION BARRIER FOR ALUMINUM METALLIZATION

A novel tungsten nitride (WNx) film for diffusion barrier applications has been prepared by nitridation of a fine grain chemical vapor depos ited tungsten (CVD-W) film. The fine grain CVD-W is deposited at 300 d egrees C in a low pressure chemical vapor deposition reactor with a Si H4/WF6 flow rate of 12.5/5 seem under a total gas pressure of 100 mTor r. The subsequent nitridation process is executed in nitrogen plasma a t 300 degrees C without breaking vacuum. The thickness of WN, layer as examined by secondary ion mass spectroscopy is 50 nm after 5 min expo sure to nitrogen plasma. X-ray photoelectron spectroscopy spectra show s that the atomic ratio of tungsten to nitrogen in WNx, layer is 2:1. According to the analysis by Auger electron spectroscopy and the measu rement of n(+)p junction leakage current, the Al/WNx/W/Si multilayer m aintains excellent interfacial stability after furnace annealing at 57 5 degrees C for 30 min. The effectiveness of W2N barrier is attributed to stuffing grain boundaries with nitrogen atoms which eliminates the rapid diffusion paths in fine grain CVD-W films. (C) 1997 American In stitute of Physics.