We investigated HfO2 etching characteristics in conventional Si gate etching chemistries, namely, CF4 and Cl2/HBr/O2-based chemistries. We obtained an adequate etch rate of 2.0 nm/min for both chemistries and a selectivity of 1.9 over SiO2 for Cl2/HBr/O2-based chemistry. We examined the etch rate dependence on source power, bias power, O2 flow rate, and Cl2 flow rate in the Cl2/HBr/O2 chemistry. It was clarified that a physical component is dominant in HfO2 etching in this chemistry. The possibilities of achieving a higher HfO2/SiO2 selectivity and of controlling the anisotropic/isotropic component in HfO2 patterning were also discussed. Moreover, it was clarified that the surface portion of the damaged layer created by the dry-etching step can be removed by a subsequent wet etching. Based on these results, the sub-100 nm patterning of poly-Si/HfO2 gate stacks was successfully demonstrated.
We achieved 635/250µA/µm@Ioff=20pA/µm unstrained FuSI/HfSiON nMOS/pMOS devices (Vdd=1.1V, Ioff=20pA/µm, Jg=20/8 mA/cm 2 ) representing a 20%/2% device improvement enabling 10% power delay improvement compared to our previous report [1]. This was reached by a careful optimization of the nitrogen content into our HfSiON gate dielectric (to be 3-6%). Second, we demonstrate that the nitrogen content impacts not only the device performance but also the gate leakage current, the gate oxide integrity as well as PBTI and NBTI. We also report for the first time a 0.8 nm EOT HfSiON dielectric with Ni-FuSI gate and its impact on ring oscillator delay resulting in 9ps delays. This is an absolute record for any CMOS with metal gate to date.
Thin HfAlO x films grown on SiON(0.9 nm)/Si by atomic layer deposition technique were characterized by using monoenergetic positron beams. The lifetimes of positrons in the HfAlO x film after post-deposition annealing (PDA) ranged between 412-403 ps. Since these lifetimes were longer than the lifetime of positrons trapped by point defects in metal oxides, such as LaCoO 3 , PbTiO 3 , and BaTiO 3 , the positrons in HfAlO x films were considered to annihilate from the trapped state by open spaces which exist intrinsically in their amorphous structure. The line-shape parameter S of the Doppler broadening spectrum corresponding to the annihilation of positrons in HfAlO x films decreased by PDA, and the S value decreased with increasing an O 2 -content in an atmosphere during PDA (0.004-1%). The observed behavior of the S value was attributed to the shrinkage of the open spaces due to the change in the matrix structure of HfAlO x . After P + -and B + -implantation into poly-Si films grown on the HfAlO x films, the diffusion of positrons in the Si substrates toward the HfAlO x film was suppressed. This fact was attributed to positive charges introduced near the HfAlO x films.
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