Native oxide film thickness

After the rearrangement of the formula. Equation (3) gives the relation of the film thickness d with the intensity ratio Iso/Is for LW spectrum of the native oxide on the silicon wafer. As shown in Table I, the native oxide film thickness of d for Figure 1 or Figure 5 were calculated by equation (3) from the measured intensity ratio Iso/Is. The mean value of the thickness was 0.8 nm on the relatively thin region and was 1.2 nm on the relatively thick region. 

Figure 6. Cross sectional schematic diagram for the calculation of the native oxide film thickness of d. The normal of the sample surface was set coincident with the axes of the CMA and the primary electron beam.

In water after a suffieient time lapse the surfaee is always eovered with a thin oxide film and the steady state thiekness depends on the initial surface condition. The steady state thickness of the native oxide films formed on the silicon surface in water is similar to that formed in air. Water is essential for the formation of oxide on the silicon surface in different solutions, organic or inorganic. Oxide film does not form on the surface in water when the concentration of HF is higher than 10 ppm. 

In recent development of the semiconductor industries, thermal oxide film thickness of less than 5 nm has been used in semiconductor devices such as metal-oxide-semiconductor (MOS) structures. Thickness of less than 5 nm is almost near the thickness of a native oxide film on the surface of silicon wafer. Therefore the characterization of ultra thin native oxide film is important in the semiconductor process technology. The secondary electron microscopy (SEM), the scanning Auger electron microscopy (SAM), the atomic force microscopy (AFM) and the X-ray photoelectron spectroscopy (XPS) might be the useful characterization method for the surface of the silicon wafers. 

A number of works have been performed about the thickness estimation of native oxide film on a silicon wafers by using XPS, and obtained good results to characterize the raw surface of the silicon wafers (1-2). However, XPS is an analytical method which is applicable to a relatively large area, due to the primary X-ray probe cannot focus on a small spot. Therefore a micrometer-scale structure... 

In this report, the author presents the investigative study of the preferred analytical conditions to observe a micrometer-scale structure of the native oxide film on a silicon wafer and the thickness estimation method by using LVV Auger spectra intensity ratio for the elemental silicon and the silicon oxide. 

The relative sensitivity factor (RSF) of LW spectra of the silicon were obtained for the calculation of the thickness estimation of the ultra thin native oxide film. Although the characteristics nature of the thermal silicon oxide film on the silicon wafers might be different from that of the ultra thin native oxide film, RSF of LVV spectra for the silicon were obtained by the measurement of Auger signal intensity using thermally grown silicon oxide film of 100 nm thickness as a reference sample... 

Table I. Thickness of the native oxide film calculated by equation (3)...

Kim and coworkers [147] have studied the lithiation of pure Mg. They have obtained a capacity of 3070 mAh/g for the first lithiation (probably going deep into the P phase region) and 2150 mAh/g for the first delithiation. However, they have noticed that the pure Mg electrode could not be lithiated at a current larger than 10 mA/g, which corresponds to a very small rate ( C/300). This poor rate capability has been attributed to the presence of a native oxide film on the surface of Mg or to the formation of an excessive SEl thickness. Alloys composed of inactive Mg2Ni and Mg (global composition Mgo.75Nio.25) reacted quite well with Li, but for pure Mg as well as Mg-Ni alloys, the initial capacity was almost lost after 10 cycles. 

A1 is thermodynamically unstable, with an oxidation potential at 1.39 V. Its stability in various applications comes from the formation of a native passivation film, which is composed of AI2O3 or oxyhydroxide and hydroxide.This protective layer, with a thickness of 50 nm, not only stabilizes A1 in various nonaqueous electrolytes at high potentials but also renders the A1 surface coating-friendly by enabling excellent adhesion of the electrode materials. It has been reported that with the native film intact A1 could maintain anodic stability up to 5.0 V even in Lilm-based electrolytes. Similar stability has also been observed with A1 pretreated at 480 °C in air, which remains corrosion-free in LiC104/EC/ DME up to 4.2 However, since mechanical... 

Before film deposition, several Al substrates were annealed in air at 590°C for two hours. Under these conditions, a 40 nm thick thermally grown Al Oj is formed. With these substrates also coated with SijN films (system B) and SiO 4.5 wt.% P films (system E), the aim is to compare the mechanical behavior of systems with a native oxide interlayer (systems A and C) to that of systems having a thermally grown Al Oj interlayer (systems B and E). 

The surface of silicon in air is always covered with a very thin oxide film. Table 2.10 shows that the thickness of native oxide formed on the surface of silicon after several days in air varies from 5 to 20 A depending on preparation conditions. Such a large variation in the thickness of native oxide indicates the great sensitivity of the surface reactivity to minute variations of environmental and material conditions. 

The materials discussed in this chapter are limited to the relatively thick oxides formed at potentials greater than several volts. It thus concerns mainly the growth and the bulk properties of anodic oxides. The data on thin oxide films are presented in other chapters. In particular, the oxide films involved in passivation at potentials within a few volts above OCP are dealt with in Chapter 5. Native oxides, which are almost always present on the surface of silicon electrodes, are discussed in Chapter 2. 

The thin oxide film, usually no more than 1 or 2nm in thickness, which spontaneously forms in the air and in water, is referred to as native oxide. Native oxide of a certain form and thickness exists essentially on all silicon surfaces due to the abundance of air and water and the inevitable encounters with them during the production and processing of silicon material and devices. Thicker oxides, up to 1 [dm in thickness. 

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