Atomic Layer Deposition, Characterization, and Dielectric Properties of HfO₂/SiO₂ Nanolaminates and Comparisons with Their Homogeneous Mixtures

Abstract

Nanolaminates of HfO 2 and SiO 2 were prepared using atomic layer deposition (ALD) methods. Successive exposure of substrates maintained at 120 or 160°C to nitrogen flows containing Hf(NO 3 ) 4 and ( t BuO) 3 SiOH led to typical bilayer spacings of 2.1 nm, with the majority of each bilayer being SiO 2 . The density of the SiO 2 layers (measured using X-ray reflectometry (XRR)) was slightly higher than expected for amorphous silica, suggesting that as much as 10 % HfO 2 was incorporated into the silica layers. Based on cross-sectional transmission electron microscopy (TEM) and XRR, oxidation of the silicon substrate was observed during its first exposure to Hf(NO 3 ) 4 , leading to a SiO 2 interfacial layer and the first HfO 2 layer. Combining the ALD of Hf(NO 3 ) 4 /( t BuO) 3 SiOH with ALD cycles involving Hf(NO 3 ) 4 and H 2 O allowed the systematic variation of the HfO 2 thickness within the nanolaminate structure. This provided an approach towards controlling the dielectric constant of the films. The dielectric constant was modeled by treating the nanolaminate as a stack of capacitors wired in series. The nanolaminate structure inhibited the crystallization of the HfO 2 in post-deposition annealing treatments. As the HfO 2 thickness decreased, the preference for the tetragonal HfO 2 phase increased.

HfxZr1−xO2 films chemical vapor deposited from a single source precursor of anhydrous HfxZr1−x(NO3)4

“…2(a), for Hf 0.61 Zr 0.39 O 2 film as-deposited at 110 1C/500 1C, between 100 s and 300 s etching time, there is a region co-existing Hf, Zr, Si and O, which indicates the interface between the film and Si substrate probably consists of hafnium zirconium silicates. The formation of silicates at the interface may be due to the oxidation of the Si substrate during its first exposure to Hf x Zr 1 À x (NO 3 ) 4 precursor, because of the strong oxidation role of anhydrous nitrate sources [27]. Fig.…”

Synthesis of carbon-rich hafnia thin films by pulsed laser deposition

“…At any rate, while the stable phase of bulk HfO 2 at room temperature is the monoclinic one, the presence of minor tetragonal phase is possible when the crystalline HfO 2 is formed by annealing from amorphous HfO 2 . In fact, published work indicates that crystallization of HfO 2 into tetragonal phase seems to be preferred when the amorphous precursor has a large surface area 37 and when long-range structural order is inhibited by geometrical constraints 38 or by mixing with other oxides. 39,40 Films of pure HfO 2 grown by PLD at room temperature are typically amorphous, 41 and it is thus not surprising that the as-deposited films studied here are amorphous as well.…”

Density Investigation by X‐ray Reflectivity for Thin Films Synthesized Using Atmospheric CVD

“…Measurements were carried out in a u/2u configuration using an X-ray (CuKa) generated at 40 kV and 40 mA [19][20][21]. Soller slits of 2.9 degree placed on both the incident and reflected sides of the sample were used to reduce the divergence angle of perpendicular to the plane of reflection.…”