Band structure and electrical properties of Gd-doped HfO2 high k gate dielectric

Abstract

Effects of Gd doping on band gap, band offset, oxygen vacancies, and electrical properties of amorphous HfO2 film have been studied. The results show that Gd incorporation helps increase band gap, conduction band offset and conduction band minimum, and reduce oxygen vacancies simultaneously. Kept at the same physical thickness of 5 nm, Gd-doped HfO2 gate dielectric has a leakage current density of 9.0×10−4 A/cm2 at 1 V gate voltage, one and a half orders of magnitude lower than that of the pure HfO2. Gd doping also enhances the dielectric constant. The capacitance equivalent thicknesses of 0.98 nm and 0.81 nm for HfO2 and Gd-doped HfO2 films, respectively, have been obtained.

Computational investigation of the phase stability and the electronic properties for Gd-doped HfO2

“…14 These calculations seem to conflict with the experimental observation 12 that the Gd doping suppresses the formation of oxygen vacancies.…”

“…The band gap size is in coincident to the experimental value of 5.97 eV at the 25% Gd concentration for the amorphous phase. 12 The band gap increase is somehow larger than the experimental value of 0.16 eV for the amorphous phase.…”

“…4 The RE doping also enlarges the band gap, increases the permittivity, and suppresses the formation of oxygen vacancies. 12 Recent experimental studies 4,6 found when the Gd doping is beyond a certain concentration around 15%-20% the doped HfO 2 is completely transformed to the tetragonal phase. The density functional theory (DFT) calculations were also used to investigate the phase stability, point defects and defect complexes in Gd-doped HfO 2 .…”

Structure and dielectric properties of amorphous high-κoxides: HfO2, ZrO2, and their alloys

“…1 Several promising candidates are metal oxides such as HfO 2 , 2,3 ZrO 2 3-5 and Al 2 O 3 , 6 all of which have high value of dielectric constant κ. High-κ metal oxides in their amorphous (a-) form are more preferable as a gate oxide over their crystalline form due to several important advantages they provide: (i) isotropic physical properties; (ii) no crystalline domain boundary which leads to less defects at the interface with the Si substrate; and (iii) good compatibility with the conventional CMOS fabrication process. Some alloy structures of these high-κ metal oxides are also being studied extensively [7][8][9][10][11][12] and, in fact, a Hf based alloy material has already been in its third generation of production as a gate oxide in the semiconductor industry and further improvements of thermal stability, dielectric constant and material preparations are underway. [8][9][10] In clear contrary to the abundance of experimental results in the literature, theoretical studies of the structure and dielectric properties of amorphous metal oxides and their alloys are quite limited.…”

“…Some alloy structures of these high-κ metal oxides are also being studied extensively [7][8][9][10][11][12] and, in fact, a Hf based alloy material has already been in its third generation of production as a gate oxide in the semiconductor industry and further improvements of thermal stability, dielectric constant and material preparations are underway. [8][9][10] In clear contrary to the abundance of experimental results in the literature, theoretical studies of the structure and dielectric properties of amorphous metal oxides and their alloys are quite limited. One of the reasons is the difficulties in generating reasonable and reliable amorphous structures with the available theoretical methods.…”