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

Abstract

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 I on /I off ratio over 10 5 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.

The physics and chemistry of the Schottky barrier height

“…144,307,[378][379][380][381][382][383][384][385][386][387][388][389][390] However, the net effect of interfacial chalcogen varied, as both significant increases 307 and decreases 386 in the n-type SBH were observed. To introduce impurities such as metals, [391][392][393][394][395] dopants, 348,389,390,[396][397][398][399][400][401][402][403][404] semiconducting, 405,406 and insulating 407 elements to the MS interface, various other methods have also been used, including deposition, ion implantation, segregation, etc. As shown in Fig.…”

Enhancing the Performance of Germanium Channel nMOSFET Using Phosphorus Dopant Segregation

“…The phosphorus dopants (10 keV, 1 × 10 15 cm −2 ) were then implanted in the metal S/D regions. The dopants segregated at the NiGe/p-Ge interface when they were activated using RTA at 500°C for 60 s. Moreover, an interesting approach often referred to as the snowplow effect, or the pile-up of phosphorus dopants, has been verified by using a secondary ion mass spectrometry (SIMS) depth profile [10]- [12], [14]. A GeO 2 was used as a surface passivation layer using rapid thermal oxidation (RTO) at 520°C for 30 s and then an Al 2 O 3 deposition was performed by atomic layer deposition (ALD) after the active area was defined.…”

“…Recently, many elements from group V, including phosphorus, arsenic, and antimony, have been proven to modulate the Schottky barrier height (SBH) of NiGe/Ge [10]- [13] because they segregate at the interface. Li et al successfully fabricated a NiGe/p-Ge Schottky diode with a low electron SBH of 0.1 eV by implanting phosphorus after NiGe formation [12]. Koike et al induced phosphorus atoms in the NiGe/p-Ge to tune the SBH [13].…”

A study on NiGe-contacted Ge n+/p Ge shallow junction prepared by dopant segregation technique

“…And, As was found to be superior to P for Schottky barrier lowering. P ion implantation after NiGe formation was also proposed [36]. However, junction characteristics and contact resistance were not reported in these literatures.…”