Laser ablation of titanium nitride coated on silicon wafer substrate for depth profiling using ICP-MS

Depth profiling of titanium nitride coated on silicon substrate at a thickness of 1 pin as a diffusion barrier for semiconductor application was studied using laser ablation (LA)-ICP-MS. The ablated particles and craters were characterized by SEM, TEM and a surface mapping microscope. Several unique characteristics were observed in this work. Although the laser beam had a short wavelength of 213 nm with flat energy, the ablated craters showed an inverse triangular shape, rather than a rectangular shape, with severe thermal degradation at the brink. In addition, the crater shape and depth were strongly dependent on the structure and thermal properties of the target. Since the TiN had a columnar structure with lower thermal conductivity and a higher melting point, it showed clear craters with less thermal degradation compared to Si substrate. The average rate of depth profiling was 40 nm per pulse. In addition, the repetition rate of the laser also significantly influenced the shape and depth of the craters. A low repetition rate produced deep craters due to high residual stress and providing sufficient time for energy concentration and heat dissipation, indicating that the repetition rate should be optimized for each material. (C) 2014 Elsevier B.V. All rights reserved.