Impact of nitrogen ion-implantation on deep sub-micron salicide process

In this paper, key issues of salicide process are studied for a variety of additional nitrogen (N⁺) implantation step. As devices are scaled down to deep sub-micron level, transformation of TiSi₂ from the high resistivity metastable C49-phase to final C54-phase is retarded. Different techniques had been developed to enhance the silicidation process, including PAI (Pre-amorphization implant) to enhance C54-phase TiSi₂ nucleation, and ITM (implant through metal) to introduce Ti/Si interface-mixing. It is of great interest to further improve the process such that the use of self-aligned TiSi₂ process can be further extended down to deep sub-micron devices without switching to other materials. Impact of incorporating N⁺ implantation into the conventional self-aligned TiSi₂ sub-micron CMOS devices is presented. Silicidation reaction is found to be enhanced by N ⁺ implantation. As a result, lower sheet resistance is achieved on narrow polysilicon line. Low energy and dosage ion-implantation conditions are preferred in order to minimise the gate to source/drain leakage. p+ and n+junction leakage will be further discussed in this article. This is the very first study on the effect of N⁺ ion-implantation on silicidation reaction. SEM and AFM were used to study the impact of N⁺ incorporation, cross-section TEM were performed to study the defects generated after N⁺ implantation.