A Ge-stabilized tetragonal ZrO2 dielectric with a permittivity (κ) value of 36.5 has been obtained by annealing a ZrO2/Ge/ZrO2 laminate at 500 °C and it is a more reliable approach toward stabilizing a tetragonal ZrO2 film. However, metal-insulator-metal (MIM) capacitors with the sole tetragonal ZrO2 film as an insulator achieve a high capacitance density of 27.8 fF/μm2 at the price of a degraded quadratic voltage coefficient of capacitance (VCC) of 81 129 ppm/V2 and unacceptably high leakage current. By capping an amorphous La-doped ZrO2 layer with a κ value of 26.3 to block grain boundaries-induced leakage paths of the crystalline ZrO2 dielectric, high-performance MIM capacitors in terms of a capacitance density of 19.8 fF/μm2, a VCC of 3135 ppm/V2, leakage current of 6.5×10−8 A/cm2 at −1 V, as well as a satisfactory capacitance change of 1.21% after ten-year operation can be realized.

By adopting an amorphous Y 2 O 3 passivation layer, which provides a wide band gap and well passivates Ge surface without the presence of GeO x , a high-permittivity ͑͒ crystalline ZrO 2 / Y 2 O 3 stack was explored as the gate dielectric for Ge metal-oxide-semiconductor ͑MOS͒ devices on Si substrate. The crystalline ZrO 2 is a Ge stabilized tetragonal/cubic dielectric with the value of 36.1 and was formed by depositing a ZrO 2 / Ge/ ZrO 2 laminate and a subsequent 500°C annealing. The high-crystalline ZrO 2 / Y 2 O 3 gate stack shows promising electrical characteristics in terms of low interface trap density of 5.8ϫ 10 11 cm −2 eV −1 , negligible hysteresis, and leakage current of 5.6 ϫ 10 −4 A / cm 2 at gate bias of flatband voltage ͑V FB ͒ 1 V for equivalent oxide thickness of 1.13 nm. This gate stack not only demonstrates the eligibility for advanced Ge MOS devices but introduces a more reliable process to form a high-crystalline gate dielectric.

CF4 plasma treatment on germanium (Ge) surface is proposed in this work to alleviate the strong Fermi level pinning between metal/Ge, and its effectiveness is also explored for n- and p-type Ge wafers. It is found that samples with CF4 plasma treatment reveal conduction behavior transition between Schottky and ohmic characteristics, a metal-work-function-dependent Schottky barrier height as well as modulated contact resistance, and these results confirm the depinning of Fermi level. This depinning can be explained by the effective capability in passivating dangling bonds at Ge surface through fluorine atoms and the formation of Ge-F binding with partial ionic property, both of which are helpful in decreasing the number of surface states and consequently release the pinning effect.

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The impact of aluminum (Al) implantation into TiN/HfO 2 /SiO 2 on the effective work function is investigated. Al implanted through poly-Si cannot attain sufficient flatband voltage (V FB ) shift unless at higher implantation energy. Al implanted through TiN at 1.2 keV with a dose of 5 × 10 15 cm −2 raised the V FB to about 250 mV compared with a nonimplanted gate stack. Moreover, the V FB shift can be up to about 800 mV at 2 keV with the same dose level accompanied with slightly equivalent oxide thickness penalty and gate leakage current degradation. Optimized process window to control Al diffusion depth was essential to minimize these impacts.Index Terms-Al Implant, effective work function (EWF), HfO 2 .