Quanxin Yun

Low Electron Schottky Barrier Height of NiGe/Ge Achieved by Ion Implantation After Germanidation Technique

In this letter, an extremely low electron Schottky barrier height (SBH) of NiGe/Ge contact has been experimentally demonstrated with P+ ion implantation after germanidation. The results show that the current characteristics of NiGe/p-Ge diode changes from ohmic to well rectifying with Ion/Ioff ratio over 105 and the corresponding hole barrier height increases to 0.56 eV, which indicates that a record-low electron barrier height of 0.10 eV is achieved. The remarkable Schottky barrier modulation is attributed to phosphorus segregation near the NiGe/Ge interface. In addition, the slight dependence of the SBH on drive-in annealing temperature is also observed ranging from 350 °C to 500 °C, and the wide temperature window is beneficial for the process integration of Ge MOS device. The low electron SBH achieved in this letter is very critical to reduce the source/drain resistance and may provide new ideas for the performance improvement of Ge devices, particularly for nMOSFETs.

Morphology and Electrical Performance Improvement of NiGe/Ge Contact by P and Sb Co-implantation

In this letter, co-implantation of P and Sb dopants into NiGe film is first proposed to improve the characteristic of NiGe/Ge contact. Through this technique, obvious enhancement of NiGe thermal stability is achieved. The surface morphology of NiGe film even keeps smooth and flat after post-germanidation annealing up to 600

Low Specific Contact Resistivity to n-Ge and Well-Behaved Ge

^{\circ}{\rm C}

{\rm n}^{+}/{\rm p}

. The current characteristics of the formed NiGe/p-Ge diodes are also improved, exhibiting better rectifying performance. It is believed that the improved interface quality and the enhanced dopant activation contribute to these improvements. Therefore, this technique shows great potential for high performance Ge device technology.

Diode Achieved by Multiple Implantation and Multiple Annealing Technique

In this letter, the specific contact resistivity of metal on n-doped germanium is significantly reduced to 3.8×10^-7 Ω·cm² by P⁺ multiple implantation and multiple annealing (MIMA) technique. The dramatic reduction of specific contact resistivity is attributed to the enhanced activation of n-type dopants, and a high electrical activation over 1×10²⁰ cm^-3 is demonstrated by the spreading resistance profiling analysis. In addition, the fabricated germanium n⁺/p diode by P⁺ MIMA technique exhibits an ION/IOFF ratio over 10⁵ with low ideality factor of 1.11. The low specific contact resistivity of metal on n-doped germanium and well-behaved germanium n⁺/p diode are beneficial for the performance improvement of Ge nMOSFETs.

Surface passivation of the Ge substrate by novel nitrogen plasma immersion treatment

In this paper, a novel nitrogen plasma immersion treatment (NNPIT) with accelerating power for Ge surface passivation is presented and compared with conventional nitrogen plasma immersion treatment (NPIT). Results show that the Ge–N bond formed at a surface by NPIT can suppress the growth of Ge suboxide during high-K dielectric deposition. As for NNPIT, more nitrogen plasma drifts to the Ge surface, which is induced by the accelerating electric field, to enhance the dangling bond passivation, and thus the NNPIT method can further suppress Ge suboxide growth during high-K dielectric deposition. As a result, the C–V characteristics in terms of a flat-band voltage, hysteresis and interface state density can be significantly improved, which is promising for high performance Ge MOSFETs fabrication.

Ge surface passivation by GeO 2 fabricated by N 2 O plasma oxidation

In this paper, Ge surface passivation by GeO2 grown by N2O plasma oxidation is presented and experimentally demonstrated. Results show that stoichiometrically GeO2 can be achieved by N2O plasma oxidation at 350°C. The transmission electron microscope observation reveals that the GeO2/Ge interface is automatically smooth and the thickness of GeO2 is ∼0.9 nm with 120 s N2O plasma oxidation. The interface state density of Ge surface after N2O plasma passivation is about ∼ 3×1011 cm−2eV−1. WithGeO2 passivation, the hysteresis of MOS capacitor with Al2O3 as gate dielectric is reduced to ∼55 mV, compared to 130 mV of the untreated one. The Fermi-level at GeO2/Ge interface is unpinned, and the surface potential is effectively modulated by the gate voltage, which is promising for high performance NMOSFETs fabrication.

Study on Schottky barrier modulation of NiGe/Ge by ion-implantation after Germanidation technique

In this letter, the As+ implantation after Germanidation technique is comprehensively studied to modulate the Schottky barrier height of NiGe/Ge contact. With the optimized drive-in annealing temperature, ion-implantation energy and dose, the current characteristics of NiGe/p-Ge diode changes from Ohmic to well rectifying with Ion/Ioff ratio over 104, and the corresponding hole barrier height increases to 0.52eV, which indicates a low electron barrier of 0.14eV has been achieved by this technique. In addition, an Ohmic behavior is obtained on n-Ge substrate, verifying the effective modulation of the electron Schottky barrier. The results may provide the guideline for improvement the performance of Ge-based Schottky barrier nMOSFETs.

Reactive ion etching of Germanium using SF 6 /CHF 3 /He gas mixture

The effect of CHF3 gas flow rate on the trench shape and etch rate was studied for germanium-based device fabrication. In this study, a sidewall tilt angle larger than 80° with the trench depth of 300nm was achieved by optimizing the flow rate ratio of SF6/CHF3/He gas mixture. Then, based on the experimental results, a Linear Reactive Ion Etching (RIE) Model was proposed to predict the optimized composition of the SF6/CHF3/He gas mixture to obtain steep trenches with low etch rate, which may provide the guideline for the germanium etching process design.

Enhanced nitrogen plasma immersion passivation method for high-K/Ge stack formation

In this paper, an enhanced Ge surface passivation method by nitrogen plasma immersion with adding RIE power is presented and experimentally demonstrated. With the acceleration effect resulting from electric field induced by proper RIE power, more nitrogen plasma will drift to Ge surface to passivate the dangling bonds. It is shown that nitrogen plasma immersion with RIE power is efficient in suppressing Ge suboxide growth during high-K dielectric deposition, reducing interface states and improving the C-V characteristic of both p-MOS and n-MOS capacitors in terms of flat-band voltage and hysteresis.