Roles of Ti, TiN, and WN as an Interdiffusion Barrier for Tungsten Dual Polygate Stack in Memory Devices

Abstract

Tungsten dual polygate (W-DPG) stacks with diffusion barriers formed by the Ti(N) process were investigated in terms of gate contact resistance (R c ) and the polydepletion effect. The Ti layer in the Ti/WN diffusion barrier is found to be converted into a TiSi x /TiN bilayer during the postdeposition annealing process. The TiSi x reaction between Ti and p+ polycrystalline silicon (poly-Si) effectively prevents the formation of a parasitic dielectric layer, which could lead to low-gate R c . The TiN reaction between Ti and WN minimizes the occurrence of the TiSi x reaction, which effectively reduces p+ polydepletion caused by the out-diffusion of boron during the postdeposition annealing process. Therefore, poly-Si/Ti/WN/W could be a promising tungsten dual polygate stack, which satisfies high-speed requirements in dynamic random-access memory (DRAM) devices.

Dependence of Gate Interfacial Resistance on the Formation of Insulative Boron–Nitride for p-Channel Metal–Oxide–Semiconductor Field-Effect Transistor in Tungsten Dual Polygate Memory Devices

“…Large portions of dissociated nitrogen from WN react with the Ti layer, which lead to TiN formation. 28) Most of the Ti in terms of volume was converted into TiN during the postdeposition thermal process, because the Gibbs free energy of the formation of Ti-N (À243 kJ/mol) is higher than that of B-N (À225 kJ/ mol). It was reported that compound formation between B and Ti could occur inside TiSi 2 .…”

Study on the oxidation and reduction of tungsten surface for sub-50 nm patterning process

“…[7][8][9][10] Tungsten (W) has the most attention among various materials as the next-generation word line to replace silicon, due to advantage such as high thermal stability, sheet resistance lower than 5 X/sq, uniform resistance per area regardless of pattern size, and excellent patterning properties due to the small grain size. [11][12][13][14] Other properties required for nanoscale patterning regarding factors such as contamination, morphology, resistance control, surface reaction, and patterning properties have been considered. 11,15 However, the oxidation of tungsten surfaces during processing is a critical problem that needs to be solved for the application of tungsten as the word line for nanoscale semiconductor devices.…”

Dependence of the Switching Characteristics of Resistance Random Access Memory on the Type of Transition Metal Oxide; TiO2, ZrO2, and HfO2

“…2 Also metal nitride such as TiN, TaN, and WN are widely used for the contact plug or barrier metal during metal interconnecting process. 3 Recently, superior performance of the HfO 2 switching using Ti/ TiN electrode was reported. [4][5][6] It showed lower operating voltage and current and stable endurance properties than other TMOs with Pt as an electrode.…”