The impact of forming gas annealing on the electrical characteristics of sulfur passivated Al2O3/In0.53Ga0.47As (110) metal-oxide-semiconductor capacitors

Abstract

This study reports the impact of forming gas annealing (FGA) on the electrical characteristics of sulfur passivated, atomic layer deposited Al2O3 gate dielectrics deposited on (110) oriented n- and p-doped In0.53Ga0.47 As layers metal-oxide-semiconductor capacitors (MOSCAPs). In combination, these approaches enable significant Fermi level movement through the bandgap of both n- and p-doped In0.53Ga0.47 As (110) MOSCAPs. A midgap interface trap density (Dit) value in the range 0.87−1.8×1012 cm−2eV−10.87−1.8×1012 cm−2eV−1 is observed from the samples studied. Close to the conduction band edge, a Dit value of 3.1×1011 cm−2eV−13.1×1011 cm−2eV−1 is obtained. These data indicate the combination of sulfur pre-treatment and FGA is advantageous in passivating trap states in the upper half of the bandgap of (110) oriented In0.53Ga0.47 As. This is further demonstrated by a reduction in border trap density in the n-type In0.53Ga0.47 As (110) MOSCAPs from 1.8×1012 cm−21.8×1012 cm−2 to 5.3×1011 cm−25.3×1011 cm−2 as a result of the FGA process. This is in contrast to the observed increase in border trap density after FGA from 7.3×1011 cm−27.3×1011 cm−2 to 1.4×1012 cm−21.4×1012 cm−2 in p-type In0.53Ga0.47 As (110) MOSCAPs, which suggest FGA is not as effective in passsivating states close to the valence band edge

Lack of correlation between C-V hysteresis and capacitance frequency dispersion in accumulation of metal gate/high-k/n-InGaAs metal-oxide-semiconductor stacks

“…This is clearly not the case for most of the samples that can be found in the literature. Results by Fu et al 23 (see diamond markers and dashed arrow number 5 between them in Fig. 7) show a strong decrease in C-V hysteresis after FGA, with a slight reduction of frequency dispersion, adding up to the difficulty of tracing a clear correlation between these two charge trapping figures of merit.…”

“…45 This discussion highlights the impact of FGA on the C-V hysteresis of the sample, although there is a strong lack of correlation between widely accepted N bt indicators. 21,23 In this framework, while frequency dispersion probes only those defects located around the Fermi level, dynamic stress sweeps in hysteresis measurements reveal the full defect profile throughout the bandgap. 18,33 Therefore, it is difficult to explain, using these interpretations, a reduction in frequency dispersion (linked to lower N bt 14,21,33 ) and an increase in hysteresis (linked to steeper profiles or larger N bt 18,19 ) after FGA treatments.…”

“…In addition, oxide defects are also accounted for the hysteresis observed on C-V sweeps in trace back mode, and special attention has been drawn toward the energy and spatial distribution of such defects. [18][19][20][21] Surface treatments such as sulfur passivation, 22,23 nitridation, 24 As 2 capping and decapping, [25][26][27][28] hydrogen, 29 oxygen, 30,31 and forming gas anneals (FGA) 21, 23,32,33 have shown diverse levels of success in the passivation of D it and BTs, resulting in different values for the capacitance dispersion with frequency. Dependences on fabrication process have been also observed on the widths of the loops during C-V hysteresis sweeps.…”

“…On the other hand, in previous work by Tang et al, 21,34 it is possible to observe hydrogen isotope effects and defect depassivation on forming gas (FG) annealed Pd/Al 2 O 3 /n-InGaAs MOS stacks, highlighting that although FGA treatment reduces the initial D it and N bt , it also causes significant hysteretic behavior, indicating that C-V hysteresis is not directly correlated with the initial D it and N bt . Contrarily, a study of the FGA impact on the electrical characteristics of sulfur passivated Pt/Au/Al 2 O 3 /InGaAs(110) MOS capacitors by Fu et al 23 showed a strong reduction of hysteresis in both p-type and n-type substrate capacitors, in addition to marginally reduced D it and N bt . Additionally, independent results by Do et al 35 have shown that oxygen segregation can form unstable interfacial layers at the metal gate (MG)/high-k interface depending on the MG material and the high-k/III-V interface preparation.…”

Brief Review of Surface Passivation on III-V Semiconductor

“…The S-bonds provide protection against further oxidation and reduce the density of surface states. Among various sulfurs, (NH 4 ) 2 S solutions had been mostly used to produce S terminate III-V surfaces [12,13]. Using alcoholic instead of aqueous sulfide solutions had been reported to have a superior passivation effect.…”