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The material and electrical properties of HfO 2 hi gh-k gate dielectric are reported.In the first part,the band alignment of H fO 2 and (HfO 2) x(Al 2O 3) 1-x to (100)Si substrate and thei r thermal stability are studied by X-ray photoelectron spectroscopy and TEM.The energy gap of (HfO 2) x(Al 2O 3) 1-x,the valence band offset, and the conduction band offset between (HfO 2) x(Al 2O 3) 1-x and the Si substrate as functions of x are obtained based on the XPS results .Our XPS results also demonstrate that both the thermal stability and the resist ance to oxygen diffusion of HfO 2 are improved by adding Al to form Hf aluminat es.In the second part,a thermally stable and high quality HfN/HfO 2 gate stack is reported.Negligible changes in equivalent oxide thickness (EOT),gate leakage, and work function (close to Si mid-gap) of HfN/HfO 2 gate stack are demonstrat ed even after 1000℃ post-metal annealing(PMA),which is attributed to the super ior oxygen diffusion barrier of HfN as well as the thermal stability of the HfN/ HfO 2 interface.Therefore,even without surface nitridation prior to HfO 2 depo sition,the EOT of HfN/HfO 2 gate stack has been successfully scaled down to les s than 1nm after 1000℃ PMA with excellent leakage and long-term reliability.T he last part demonstrates a novel replacement gate process employing a HfN dummy gate and sub-1nm EOT HfO 2 gate dielectric.The excellent thermal stability of the HfN/HfO 2 gate stack enables its use in high temperature CMOS processes.Th e replacement of HfN with other metal gate materials with work functions adequat e for n- and p-MOS is facilitated by a high etch selectivity of HfN with respe ct to HfO 2,without any degradation to the EOT,gate leakage,or TDDB characteris tics of HfO 2.
The material and electrical properties of HfO 2 hi gh-k gate dielectric are reported in the first part, the band alignment of H fO 2 and (HfO 2) x (Al 2 O 3) 1-x to (100) Si substrate and the thermal barrier was studied by X-ray photoelectron spectroscopy and TEM. The energy gap of (HfO 2) x (Al 2 O 3) 1-x, the valence band offset, and the conduction band offset between (HfO 2) x Al 2 O 3) 1-x and the Si substrate as functions of x are obtained on the XPS results. Our XPS results also demonstrate that both both thermal stability and the resist ance to oxygen diffusion of HfO 2 are improved by adding Al to form Hf aluminas es. In the second part, a thermally stable and high quality HfN / HfO 2 gate stack is reported. Negligible changes in equivalent oxide thickness (EOT), gate leakage, and work function (close to Si mid-gap) of HfN / HfO 2 gate stack are demonstrat ed even after 1000 ℃ post-metal annealing (PMA), which is attributed to the super ior oxygen diffusio n barrier of HfN as well as the thermal stability of the HfN / HfO 2 interface. Before, even without surface nitridation prior to HfO 2 depo sition, the EOT of HfN / HfO 2 gate stack has been successfully scaled down to les s than 1 nm after 1000 ℃ PMA with excellent leakage and long-term reliability. T last part demonstrates a novel replacement gate process employing a HfN dummy gate and sub-1nm EOT HfO 2 gate dielectric.The excellent thermal stability of the HfN / HfO 2 gate stack enables its use in high temperature CMOS processes. Thre replacement of HfN with other metal gate materials with work functions adequat e for n- and p-MOS is facilitated by a high etch selectivity of HfN with respe ct to HfO 2, without any degradation to the EOT, gate leakage, or TDDB characterization of HfO 2.