Suppressed Thermally Induced Flatband Voltage Instabilities with Binary Noble Metal Gated Metal--Oxide--Semiconductor Capacitors

• Published in: Japanese Journal of Applied Physics 2012-02, Vol.51 (2), p.02BA05-02BA05-4
• Main Authors: Choi, Changhwan, Ahn, Jinho, Choi, Rino
• Format: Article
• Language: English
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.51.02BA05

We investigated thermally induced flatband voltage ($V_{\text{FB}}$) instabilities with single noble metals (Pt, Ir, Pd), their binary metal (IrPt) and control TiN used for gate electrodes in metal oxide semiconductor devices with atomic layer deposited HfO 2 gate dielectric. As-deposited e-beam evaporated noble metals and sputtered TiN gated devices show near band-edge p-type metal--oxide--semiconductor (pMOS) characteristics and higher $V_{\text{FB}}$ than midgap value, respectively. After 450 °C at 30 min forming gas anneal, $V_{\text{FB}}$ of devices with e-beam evaporated single metals and sputtered TiN is substantially shifted toward mid-gap position, indicating thermally induced $V_{\text{FB}}$ instability. However, device with binary metal alloy gate shows suppressed $V_{\text{FB}}$ shifts and work-function as high as 4.95 eV is attained with 450 °C at 30 min FGA. It can be explained by oxygen diffusion within gate stack structure into interfacial layer (IL) between Si and HfO 2 during anneal, leading to thicker IL and vacancy generation in dielectric.