Surface Chemistry and Interface Formation during the Atomic Layer Deposition of Alumina from Trimethylaluminum and Water on Indium Phosphide

Abstract

The surface chemistry and the interface formation during the initial stages of the atomic layer deposition (ALD) of Al2O3 from trimethylaluminum (TMA) and H2O on InP(100) were studied by synchrotron radiation photoemission spectroscopy and scanning tunneling microscopy. The effect of the ex situ surface cleaning by either H2SO4 or (NH4)2S was examined. It is shown that the native oxide on the InP surface consisted mainly of indium hydrogen phosphates with a P enrichment at the interface with InP. After a (NH4)2S treatment, S was present on the surface as a sulfide in both surface and subsurface sites. Exposure to TMA led to the formation of a thin AlPO4 layer, irrespective of the surface cleaning. The surface Fermi level of p-type InP was found to be pinned close to midgap after H2SO4 cleaning and moved only slightly further toward the conduction band edge upon TMA exposure, indicating that the AlPO4/InP interface was rather defective. (NH4)2S passivation led to a Fermi level position of p-type InP close to the conduction band edge. Hence, the InP surface was weakly inverted, which can be attributed to surface doping by S donors. TMA exposure was found to remove surface S, which was accompanied by a shift of the Fermi level to midgap, consistent with the removal of (part of) the S donors in combination with a defective AlPO4/InP interface. Further TMA/H2O ALD did not lead to any detectable changes of the AlPO4/InP interface and suggested simple overgrowth with Al2O3.

Indium diffusion through high-k dielectrics in high-k/InP stacks

“…The peak with a binding energy separation of 1.6 6 0.05 eV and 1.8 6 0.05 eV to InP is assigned to In-O for samples A and B, respectively, after annealing. 19 The decrease in intensity of both the In-P and In-O features for both samples A and B before annealing (due to the decreasing sampling depth as the analysis angle is changed from 80 to 45 ) is consistent with equal attenuation of both features by the overlying HfO 2 film (with the In-O located at the interface). However, after annealing for both samples A and B, the lack of a similar change in the In-O feature (the In-O areas are approximately the same from scans at 45 and 80 ) suggests that the In-O is distributed throughout the HfO 2 , as well as possibly on the sample surface.…”

“…16,20 The actual assignment of these states is still a matter of debate, with the formation of AlPO 4 also possible, which would have a similar BE position to that of peak assigned here to P 2 O 5 . 19 However, the interfacial oxide clearly becomes more phosphorous rich with respect to In with an increase of the binding energy for P-oxide. For sample A, both before and after annealing, the decrease in intensity of both the In-P and P-oxides features due to the decreasing sampling depth as the XPS angle FIG.…”

Chemical Nature and Control of High-k Dielectric/III-V Interfaces

“…(10) At temperatures of 300 °C or below, the formation of a hydrophosphate was also observed. (3) 700 800 900 1000 1100 1200 1300 1400 We have therefore examined the chemical evolution of the surface of both epi-ready oxide and HF/(NH 4 ) 2 S-treated InP(100) as a function of annealing. Annealing is performed up to the ALD growth temperatures of 200 °C -300 °C for five min under 100 sccm of flowing N 2 gas prior to atomic layer deposition (ALD), and then characterized by IR absorption spectroscopy with the substrate at 80 °C under 100 sccm of flowing N 2 gas.…”

Deposition of O atomic layers on Si(100) substrates for epitaxial Si-O superlattices: investigation of the surface chemistry

“…Alternative channel materials like Ge and III-V materials are also being investigated, as they offer a higher bulk carrier mobility than silicon [4]. Still, a major challenge is the integration of these channel materials with suitable high-k gate dielectric layers with sufficiently low electrical defect densities at and near the interface with the channel [5,6]. To overcome all the above issues and to be compatible with the current manufacturing technologies, Si-O superlattice structures are explored as alternative channel material [7].…”