Study on the Vt variation and bias temperature instability characteristics of TiN/W and TiN metal buried-gate transistor in DRAM application

The Vt variation and positive bias temperature instability (PBTI) of TiN/W and TiN metal buried-gate (BG) cell transistors in DRAM are characterized. The use of TiN gate shows a larger Vt variation and different PBTI behavior as compared with TiN/W gate and these are attributed to the formation of chlorine (Cl)-related trap sites during the etch-back process of metal gate. This indicates that Cl in the chemical vapor deposition (CVD) TiN gate is responsible for the phenomena.