Electrical Reliability of Integrating Low-k Silicon-Oxycarbide Barrier Film with Cu Metallization

• Main Authors: I-Hsiu Ko, 柯依秀
• Other Authors: Mao-Chieh Chen
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/jzc8zm

碩士 === 國立交通大學 === 電子工程系所 === 92 === This thesis studies the thermal stability and physical property for three PECVD low-k (k-value less than 4) amorphous silicon-oxycarbide (α-SiCO:H) dielectric barrier films with different elemental compositions designated as SiCO-A (SiC1.19O0.73), SiCO-B (SiC1.12O0.77) and SiCO-C (SiC1.34O0.85). More importantly, this study also explores the electrical reliability of integrating these silicon-oxycarbide dielectric barrier films with Cu metallization using planar MIS capacitor structure. It is found that the film density, dielectric constant and refractive index all decrease with increasing content of oxygen in the dielectric composition; this is presumably because higher content of oxygen tends to make the Si-O-Si bond of the dielectrics forming a cage-like bonding, which is a relatively loose microstructure. All of the three dielectrics are thermally stable up to 500oC (in N2 ambient for 30 min). However, the dielectric constant of the α-SiCO:H films decreases slightly at temperatures above 500oC because the H2O outgassing at the elevated temperatures would diminish the ionic and dipolar polarization, and thus the dielectric constant. Leakage current of the dielectrics at room temperature exhibited different conduction mechanisms at different electric fields, including ohmic conduction at very low electric fields, Frenkle-Poole emission at low electric fields, and electric breakdown generally at electric fields above 0.36 MV/cm. All the three α-SiCO:H dielectric films are presumably capable of retarding Cu diffusion at temperatures up to 400oC without an applied electric field because no difference in room temperature leakage current was observed between the Al-gated and TaN/Cu-gated MIS capacitors, whether as-fabricated or 400oC-annealed. The SiCO-A dielectric film exhibited a good dielectric barrier property against Cu penetration; its MIS capacitors were able to withstand BTS at 200℃ under 1 MV/cm electric field up to at least 15h. This indicates that the SiCO-A dielectric is a potential candidate to replace the higher dielectric constant SiN film as a Cu-cap barrier and etching stop layer in the Cu damascene structure. The SiCO-B dielectric, presumably due to its loose and more cage-like Si-O-Si bonding structure, can not prevent Cu from diffusion into the film under the BTS (at 200oC with 1 MV/cm electric field). The SiCO-C dielectric has an even weaker dielectric strength; in fact, breakdown occurred to the 400oC-annealed TaN/Cu/SiCO-C/Si MIS capacitor under an electric field of 0.8 MV/cm at 200oC.