Thermal Stability of Nickel Germanide Formed on Tensile-Strained Ge Epilayer on Si Substrate

Abstract

The thermal stability of a nickel germanide film formed on a tensile-strained Ge epilayer on a silicon substrate with a low-temperature Si 0.77 Ge 0.23 (50-nm)/Ge (50-nm) buffer is investigated. A record temperature of 700 • C for the stability of sheet resistance of nickel germanide is reported, which is increased by about 150 • C compared to that on bulk Ge and comparable to the temperature for nickel silicide on the Si substrate. The improvement of the thermal stability is demonstrated due to the delay of the agglomeration of the nickel germanide film on Ge-on-Si, which is proposed to be attributed to the increase of the tensile strain in the Ge epilayer during thermal annealing due to the thermal mismatch between Si and Ge.

Improvement of thermal stability of nickel germanide using nitrogen plasma pretreatment for germanium-based technology

“…Self-aligned metal germanide, adopted for S/D contact of Ge-based MOSFETs, is a key process to reduce S/D series resistance. Among metal germanides, nickel germanide (NiGe) is regarded as one of the most promising candidates due to its low resistivity, low formation temperature and low consumption of Ge [3]. However, NiGe film suffers from the poor thermal stability and starts to agglomerate at about 400 • C due to low activation energy of agglomeration in NiGe (2.2±0.2 eV) [4].…”

“…Therefore, it is quite important to improve the thermal stability of NiGe. Different methods have been proposed, such as the adoption of TiN capping layer to suppress the grainboundary grooving [5], adding ultrathin Zr, Ti, Ta, Yb, Pt or Pd interlayer to suppress the agglomeration of NiGe [3,4]. Yet, the thermal stability of NiGe becomes severe as the downscaling of NiGe film thickness.…”

Effects of Carbon Pre-Germanidation Implantation on the Thermal Stability of NiGe and Dopant Segregation on Both n- and p-Type Ge Substrate

“…9,[13][14][15] The agglomeration of NiGe films inevitably gives rise to increased sheet resistance and leakage current, and this hinders its widespread application in advanced Ge MOSFETs. In order to solve this problem, many methods such as alloying Ni with Pt, Zr, Ta and Pd, [16][17][18][19] inserting an ultrathin Ti, Yb, Pd or Pt interlayer between Ni and Ge before germanidation, [20][21][22][23] adding a capping layer 24 and forming epitaxial NiGe on tensile-strained Ge-on-Si substrate, 25 have been extensively reported to improve the thermal stability of NiGe films. The incorporation of carbon, in previous work, has been proved to be an effective way to suppress the agglomeration of NiSi [26][27][28][29][30][31][32] and NiSiGe, 33 as well as to improve the thermal stability of NiGe films formed on undoped Ge substrate.…”

Texture Evolution and Grain Competition in NiGe Film on Ge(001)

“…2,3) NiGe grown on tensile-strained epitaxial Ge-on-Si was also found to have a higher agglomeration temperature probably due to the reduced interface energy. 4) NiGe has a MnP-type orthorhombic structure with lattice constants a ¼ 5:811 # A, b ¼ 5:381 # A, and c ¼ 3:428 # A. The large difference between NiGe and cubic Ge (a ¼ 5:657 # A) prohibits the pseudomorphic epitaxial growth of NiGe on Ge.…”