X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy investigation of Al-related dipole at the HfO2/Si interface

Abstract

The presence of an ultrathin oxide layer at the high-k/SiO2 interface may result in an interfacial dipole related to the specific high-k dielectric used for the gate stacks. 1 nm HfO2/x nmAl2O3/SiO2/Si stacks with different x values (x=0, 0.4, 0.8, 1.2) have been prepared by atomic layer deposition. Using photoelectron spectroscopy, an Al-related interfacial dipole in the HfO2/Al2O3/SiO2 gate stack has been identified. X-ray photoelectron spectroscopy analysis shows that the dipole is correlated with the formation of an interfacial Al-silicate. The dipole is located at the Al-silicate interface between Al2O3 and SiO2, and its strength increases with the increase in Al2O3 thickness because of Al silicate growth. Such Al-related interfacial dipole should have potential applications in future positive metal-oxide-semiconductor devices.

Integrations and challenges of novel high-k gate stacks in advanced CMOS technology

“…Recently, there are increased interests on the physical insight of the dipole layer formation by X-ray photoelectron spectroscopy (XPS) [353,[372][373][374][375][376]. The direct evidence of the dipole effects in high-k stacks is expected to be obtained.…”

The electrostatics of Ta2O5 in Si-based metal oxide semiconductor devices

“…It was shown that the position of the capping layers' atoms is important for their functionality, 19,20 and particularly it was shown with different configurations that the contact of Al oxide with SiO 2 is responsible for the EWF increase. 12,21,22 These effects have been further utilized recently for improving metal-semiconductor contacts. 23,24 In a recent study, 22 we have shown that the formation of a Ta suboxide layer formed at a Ta-Al 2 O 3 interface resulted in an EWF increase of 0.4 eV.…”

Ab initiostudy of the electrostatic dipole modulation due to cation substitution in HfO2/SiO2interfaces

“…7,[9][10][11]14,15 Narayanan et al reviewed the construction of high-κ gate nFETs and pFETs, discussing the inclusion of capping layers as an important means of controlling the threshold voltage, 14 while Bosman et al recently studied the distribution of chemical elements within a HfO 2 /SiO 2 gate stack from Al and La capping layers. 7 When these studies are coupled with the measurements of the valence band offset (VBO), 11 it shows that Al tends to decrease the VBO of HfO 2 /SiO 2 , while La increases it, but without any clear explanation of the intrinsic cause.…”

“…Several types of dopants have recently been studied both theoretically and experimentally, including Al, [7][8][9][10][11][12][13] La,7,[10][11][12][13][14] Mg, 14,15 and Sr. 10 Of particular interest here are the dopants introduced through diffusion from capping layers of La, Al, or Mg containing materials. 7,[9][10][11]14,15 Narayanan et al reviewed the construction of high-κ gate nFETs and pFETs, discussing the inclusion of capping layers as an important means of controlling the threshold voltage, 14 while Bosman et al recently studied the distribution of chemical elements within a HfO 2 /SiO 2 gate stack from Al and La capping layers.…”