Study on ta diffusion barrier in Al/Si system

초록

The property of Ta as a diffusion barrier is studied for Al/Ta/Si structure. Interfacial reactions of Al(180 nm)/Ta(130 nm)/Si and Al(180 nm)/Ta(24 nm)/Si, in the temperature range 450∼600°C for 30 min, have been investigated. In Al/ Ta(130 nm)/Si system, which is Ta-excess case, Al<inf>3</inf>Ta is formed at 500°C. At 575°C, TaSi<inf>2</inf> is formed at the interface of Ta Si. At 600°C, after Al<inf>3</inf>Ta decomposes at the interface of Al<inf>3</inf>Ta TaSi<inf>2</inf>, free Ta is bonded to TaSi<inf>2</inf> with the supply of Si from Si substrate and free Al diffuses through TaSi<inf>2</inf>, resulting in Al spiking. In Al/Ta(24 nm)/Si system, which is Al-excess case, Al<inf>3</inf>Ta is formed at 500°C. At the same temperature of 500°C, after Al<inf>3</inf>Ta decomposes at the interface of Al<inf>3</inf>Ta/Si, free Ta reacts with Si to form TaSi<inf>2</inf> and free Al diffuses to Si substrate, resulting in Al spiking. The results of interfacial reactions can be understood from the calculated Al-Si-Ta ternary phase diagram. It can be concluded that the reaction at Al/Ta should be suppressed to improve the performance of Ta diffusion barrier in Al/Si system.

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