Band alignment at the SiO2/HfO2interface: Group IIIA versus group IIIB metal dopants

Abstract

Abstract:Using density functional theory we examine the effect of Al and La incorporation on the electronic properties of the interface in the SiO 2 /HfO 2 high-k gate stacks recently introduced into the advanced modern field effect transistors. We show that La and Al doping have opposite effects on the band alignment at the SiO 2 /HfO 2 interface: while the Al ions, which substitute preferentially for Si in the SiO 2 layer, promote higher effective work function (EWF) values, the substitution of La for Hf decreases EWF. The analysis of the electronic structure of the doped interface suggests a simple relation between the electronegativity of the doping metal, screening properties of the interfacial layer and the band offset, which allows predicting qualitatively the effect of the high-k gate stack doping with a variety of metals on its EWF.

Band alignment and electronic structure of the anatase TiO2/SrTiO3(001) heterostructure integrated on Si(001)

“…However, oxide heterointerfaces are not as well-understood as those between metals and semiconductors. The band alignment at oxide heterointerfaces has attracted considerable attention in the context of the high-k dielectric gate stack in field effect transistors [43][44][45][46][47]. More recently, the band alignment between complex oxides has been of great interest following the discovery of novel interfacial electronic phases emerging at the epitaxial complex oxide heterointerfaces [48][49][50][51].…”

“…More recently, the band alignment between complex oxides has been of great interest following the discovery of novel interfacial electronic phases emerging at the epitaxial complex oxide heterointerfaces [48][49][50][51]. To describe and control the band alignment between two materials, the interfacial chemistry of a given heterointerface has to be well understood [44,45,[52][53][54]]. …”

“…We calculate the valence band offset to be 0.76 eV, thus ΔV is -0.2 eV. This process is often described as the creation of an interface dipole or double layer involving charge transfer and subsequent dielectric screening at the interface [44,45].…”

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

“…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. Theoretically, Luo et al 13 also confirm the direction of the VBO shifts in their investigation of the location of Al and La dopants within the interfaces. They have also discussed the modification of the electronic dipole by these dopants with a phenomenological model including the effect of electronegativity of the metal dopant.…”

“…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.…”