Contact Displacement of Diffusion Barrier Layer by Metal Ion and Its Application on IC Process

• Main Authors: Yang Wu, 吳洋
• Other Authors: Chi-Chao Wan
• Format: Others
• Language: en_US
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/46894933619786988349

碩士 === 國立清華大學 === 化學工程學系 === 88 === The fabrication of interconnect has become an essential part of IC industry in recent years. In order to improve the function and efficiency of a chip, the dimension of interconnect must be shrunk to deep submicron. Copper is regarded as the best conducting material for interconnect in the next generation by virtue of its lower resistivity, higher melting point, and better electromigration endurance. Moreover, some drawbacks in the application of copper have already been overcome, e.g., the development of barrier layer material which solves the problem of thermal diffusion between copper and silicon oxide. Before the electrodeposition of copper, a diffusion barrier layer and copper seed layer must be deposited on top of the silicon wafer by PVD or CVD process. Titanium nitride and tantalum nitride are majorly used as the material for barrier layer in order to prevent the whole structure from thermal diffusion. Besides, seed layer was used to conduct electricity in electrodeposition process. It was found that nitride barrier material could react with some metal ions by contact displacement and deposit metal upon silicon substrate. The research of contact displacement reaction is therefore useful for evaluating the reliabilty of titanium nitride and tantalum nitride as barrier layer. Additionally, if copper can be deposited directly through this reaction or other electrochemical methods without seed layer, the cost of vaccum facilities accompanied with PVD or CVD process can be saved. The following table shows the results of different solutions in contact with various substrates. Solution SiTiN film TiN powder TaN film Ti F- / Cu2+ ○ ○ × × ○ F- / Ag+ ○ ○ ○ × ○ F- / Pd2+ ○ ○ ○ ○ ○ BHF ※ × × × ※ Cu2+ × × × × ○ Ag+ × × × × ○ Pd2+ × × × × ○ Time: 15 minutes. Temp: 20℃. Symbol ○ represents that the deposition of metal was observed. Symbol ×represents that no reaction was observed. Symbol ※ represents that the corrosion of substrate was observed. It can be seen that TiN film can react with Cu2+, Ag+, and Pd2+ in the presence of fluoride ion, while TaN film reacts with Pd2+ and F- only. Further more, metal deposition on silicon sample also takes place only when the fluoride ion exists. Thus, we concluded that fluoride ion should play an essential role in displacement reaction in all cases, which is not a simple redox reaction like the Mz+-Ti couple. In addition, the details of contact displacement reaction can be studied with the aid of some instruments, such as XRD, ESCA, SEM, and IR Spectroscopy. Three possible mechanisms of TiN displacement reaction were proposed in this study based on the results of experiments. Besides, KI and NaI were found to activate the palladium displacement without corrosion on TiN, which is superior to BHF if Pd is applied to serve as seed layer for subsequent copper deposition. Furthermore, palladium deposition atop TaN by contact displacement was found to serve as a platform or seed layer for subsequent copper electrodeposition.