Atomic layer deposition of W1.5N barrier films for Cu metallization

An atomic layer deposition process to grow tungsten nitride films was established at 350 degrees C with a pulse sequence of WF6/NH3/C2H4/SiH4/NH3. The film composition was determined with Rutherford backscattering as W1.5N, being a mixture of WN and W2N phases. The growth rate was similar to 1 x 10(15) W atom/cm(2) per cycle (monolayer of W2N or WN). The films with a thickness of 16 nm showed root-mean-square roughness as low as 0.43-0.76 nm. The resistivity of the films was stable after 50 cycles at a value of 480 mu Omega cm. Results of four-point probe sheet resistance measurements at elevated temperature demonstrated that our films are nonreactive with Cu at least up to 500 degrees C. Results of I-V measurements of p(+)/n diodes before and after heat-treatment in (N-2 + 5% H-2) ambient at 400 degrees C for 30 min confirmed excellent diffusion barrier properties of the films. (c) 2005 The Electrochemical Society. All rights reserved.