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Effect of enhanced nitridation in PECVD-Ti process for sub-0.2 μm metal bit-line common contact process

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7 Author(s)
Hee Sook Park ; Semicond. R&D Center, Samsung Electron., Kyungki, South Korea ; Kwang Jin Moon ; Myoung Bum Lee ; Sang Bom Kang
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The implementation of W bit-line enabled the integration of n+ and p+ common contact process at bit-line level. Despite the advantages of the common contact process such as chip-area reduction and elimination of the burden associated with MC dry etch, the immediate implementation of the common contact is difficult due to large increase of p+ contact resistance with high thermal budget capacitor process. The results of the present investigation indicate that the thickness of TiSi2 layer must be minimized in order to prevent the out-diffusion of boron into silicide layer. However, simply reducing the thickness of TiSi2 presents another problem since it leads to a discontinuous layer of TiSi2. Heavily increasing the dosage of p+ plug implantation, which is another way of preventing the depletion of boron dopants, resulted in degradation of p+ contact resistance. Therefore, the dopant out-diffusion alone cannot explain the degradation of p+ contact resistance. In order to minimized the thickness of TiSi2, enhanced nitridation after deposition of PECVD-Ti was tested and resulted in effective reduction of the p+ contact resistance by 25%. The TEM and SIMS analysis showed that the additional growth of TiSi2 during high thermal budget post annealing was suppressed by the enhanced nitridation. The mechanism responsible for reducing the p+ contact resistance by the enhanced nitridation is attributed to the prevention of the dopant depletion at the interface between TiSi2 and Si due to the suppressed formation of additional TiSi2

Published in:

VLSI Technology, Systems, and Applications, 2001. Proceedings of Technical Papers. 2001 International Symposium on

Date of Conference:

2001