Interfacial and structural properties of sputtered HfO2 layers

Abstract

Magnetron sputtered HfO2 layers formed on a heated Si substrate were studied by spectroscopic ellipsometer (SE), x-ray diffraction (XRD), Fourier transform infrared (FTIR), and x-ray photoelectron spectroscopy (XPS) depth profiling techniques. The results show that the formation of a SiO x suboxide layer at the HfO2 /Si interface is unavoidable. The HfO2 thickness and suboxide formation are highly affected by the growth parameters such as sputtering power, O2 /Ar gas ratio during sputtering, sputtering time, and substrate temperature. XRD spectra show that the deposited film has (111) monoclinic phase of HfO2, which is also supported by FTIR spectra. The atomic concentration and chemical environment of Si, Hf, and O have been measured as a function of depth starting from the surface of the sample by XPS technique. It shows that HfO2 layers of a few nanometers are formed at the top surface. Below this thin layer, Si-Si bonds are detected just before the Si suboxide layer, and then the Si substrate is reached during the depth profiling by XPS. It is clearly understood that the highly reactive sputtered Hf atoms consume some of the oxygen atoms from the underlying SiO2 to form HfO2, leaving Si-Si bonds behind

Effects of physical growth conditions on the structural and optical properties of sputtered grown thin HfO2 films

“…The results infer that there existed a very thin perfect Hf-oxide layer, later Si-Si bonds are detected even before Si suboxide layer is reached and then Si substrate is reached. Since Si-Si bonds were measured just before Si-oxide is reached, it can be realized that highly reactive sputtered Hf atoms consume some of the oxygen atoms from the underlying SiO 2 to form hafnium-oxide by leaving Si-Si bonds behind [3]. Our results also confirm what Yamamoto et al revealed with their experiment that the oxygen radicals oxidize the Hf metal more selectively than Si substrate [11].…”

“…oxide film gives the idea of causing elementally active sputtered Hf radicals decompose the native SiO 2 to form elemental silicon atom and oxygen molecule and/or atom explicitly. As a result, the oxygen gained from the native SiO 2 oxide is used to form HfO 2 while leaving unbonded elemental Si atoms or Si-suboxide behind [3].…”

“…Having high-κ value around 25 and being thermodynamically stable when grown on Si, HfO 2 is considered to be the most promising candidate to replace SiO 2 [1]. Important film properties including dielectric constant and refractive index of grown thin oxide film depend on the growth parameters [2] as well as the initial thin film constitution [3]. Moreover, the interfacial properties of grown film play crucial role in the electrical properties of the devices [4].…”

Evolution of SiO2/Ge/HfO2(Ge) multilayer structure during high temperature annealing

“…Many research groups have studied interfacial layer formations in Si/HfO 2 structure during both fabrication and annealing. Thermodynamically driven SiO 2 /Si formation at Si/HfO 2 interface is usually observed on the substrate side of HfO 2 [4]. This may degrade the performance of device.…”

Impact of temperature increments on tunneling barrier height and effective electron mass for plasma nitrided thin SiO2 layer on a large wafer area

“…5 Important film properties as well as interfacial structure affecting especially electrical properties including dielectric constant and refractive index of the grown film, depend on the growth parameters as well as the initial thin film constitution. [6][7][8] Therefore, it should be noted that the applied physical conditions on thermally grown SiO 2 must be well controlled through the whole stages during further processing steps in order to improve its dielectric properties.…”