Suppression of boron diffusion using carbon co-implantation in DRAM

• The impact of Ge + C co-implantation on dopant diffusion was investigated.
• DIBL and VTH variation was improved by Ge + C co-implantation.
• The VTH mismatch and the write characteristics were improved in the DRAM device.

In this paper, germanium pre-amorphization implantation (PAI) and carbon co-implantation (Ge + C co-IIP) were applied to suppress boron diffusion. The corresponding characteristics were investigated in terms of the dopant diffusion, device performance, and its application to dynamic random access memory (DRAM). A shallow dopant profile was indicated and the threshold voltage (VTH) was reduced by approximately 45 mV by Ge + C co-IIP. In the DRAM device, the VTH mismatch of the sense amplifier NMOS pairs was reduced by approximately 15% and the write characteristics were improved two-fold.

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