Thin films silicon dioxide

Beta SiC (PSiC) has good chemical resistance, particularly to oxidation owing to the formation of a thin adherent and protective film of silicon dioxide on the surface. Its characteristics are summarized in Table 9.6. 

CVD, the other major deposition process, is used on a large scale. A typical low-E glass is obtained by depositing a thin film of silicon dioxide followed by another thin film of fluorine-doped tin oxide. The Si02 acts as a diffusion barrier and the Sn02 reduces the emissivity. A typical CVD apparatus is shown in Fig. 

As an example of the latter technique, Volkman et al. demonstrated the feasibility of using spin-cast zinc oxide nanoparticles encapsulated in 1-dodecanethiol to fabricate a functional transistor.44 The zinc oxide was deposited on a thermally grown silicon dioxide layer on a conventional silicon wafer, with thermally evaporated gold source and drain electrodes. As reported, the process requires very small particles (3nm or less) and a 400 °C forming gas anneal. A similar approach was also reported by Petrat, demonstrating n-channel thin-film transistor operation using a nanoparticle solution of zinc oxide dispersed onto a thermally grown silicon dioxide layer on a conventional... 

Metal oxide semiconductor field-effect transistors (MOSFETs) are field effect transistors with a thin film of silicon dioxide between the gate electrode and the semiconductor. The charge on the silicon dioxide controls the size of the depletion zone in the polype semiconductor. MOSFETs are easier to mass produce and are used in integrated circuits and microprocessors for computers and in amplifiers for cassette players. Traditionally, transistors have been silicon based but a recent development is field-effect transistors based on organic materials. 

M.E. Coltrin, P. Ho, H.K. Moffat, and R.J. Buss. Chemical Kinetics in Chemical Vapor Deposition Growth of Silicon Dioxide from Tetraethoxysilane (TEOS). Thin Solid Films, 365 251-263,2000. 

D.R. Lamb, Some electrical properties of the silicon-silicon dioxide system, Thin Solid Films, 5(4) (1970) 247-276. 

E. Hedborg, F. Winquist, H. Sundgren and I. Lundstrom, Charge migration on hydrophobic and hydrophilic silicon dioxide, Thin Solid Films, 340(1-2) (1999) 250-256. 

As long as the film is not reflective (i.e., specular aluminum) and is deposited on a reflective substrate (i.e., Si02 on silicon), optical techniques are available. It was recognized early that the color of a thin film could be correlated to its thickness. Although not very precise, such information is very useful for quick evaluation in the laboratory. For example, silicon dioxide films on silicon substrates can be evaluated with the data of Table 1. In fact, one of the more useful aspects of this technique is that one can make rapid judgements as to film uniformity. 

One commercial wafer deflection gauge is available, and is sketched in Figure 6. The degree of light reflection is used to indicate the amount of wafer deflection. The only difficulty with this technique occurs when relatively low stress films are measured. For normal films (i.e., thermal CVD silicon dioxide) and a stress of 109 dynes/cm2, a typical 100-mm silicon wafer (0.62-mm thick) with a 1-jum thick film will deflect 10 jum at its center. The Ionic Systems gauge claims a 0.03-pm sensitivity, so the typical stress can be measured readily. For smaller stresses 108 dynes/cm2, it may be useful to use a thinned wafer to make deflection measurements. 

There are a number of subtle effects that have to be considered when making thin film stress measurements on silicon wafers First of all, the crystal orientation of the wafer Influences the resulting stress. The same thermal CVD silicon dioxide film thickness on the same substrate indicates larger tensile stresses on (100)-oriented wafers as compared with (111 (-oriented wafers. 

The ellipsometric technique described earlier has the unique feature that the index of refraction can be determined independently of the film thickness. Then, knowledge of this index can be used to infer the chemical composition of a film. For example, thin silicon dioxide films have an index of 1.46, while silicon nitride films have a value of 2.0 typically. Now, when either of these films are deposited by PECVD techniques, their stoichiometry can vary depending on deposition conditions. It turns out that this variation in stoichiometry can be related to the measured refractive index. Accordingly, measurements of the refractive index can be used as an approximate guide to film stoichiometry. 

CFD [Chemical Fluid Deposition] A process for depositing thin films on solid surfaces by a chemical reaction in a liquid such as supercritical carbon dioxide. Superior to CVD in being capable of operation at almost ambient temperatures. Demonstrated for depositing platinum metal on silicon wafers, polymer substrates, and porous solids by hydrogen reduction of an organo-platinum compound at 80°C. 

Since positron annihilation spectroscopy is highly sensitive to atomic defects in solid materials, positron annihilation experiments have been carried out extensively on silicon (Si) and silicon dioxide (Si02), both of which are extremely important for the microelectronic device industry. While several reviews are available [1], those reviews are mainly focused on positron (not positronium) annihilation behavior because positronium (Ps) formation dose not occur in bulk crystalline Si. Recent positron annihilation experimental studies revealed that Ps formation occurs in some Si-based thin films, such as porous Si and hydrogenated amorphous Si furthermore, Ps formation is dominant in high-purity amorphous Si02 thin films. In this chapter, Ps annihilation characteristics in Si and Si02 thin films will be discussed from the experimental point of view. 

Ferroelectrics are high dielectric materials that are easily polarized in an electric field and can remain polarized to some degree after the field is removed. Such properties make them ideal candidates for computer memory applications and they have been used in the form of thin films as ferroelectric random access memories (FeRAMs) and as high permittivity dielectrics for Dynamic Random Access Memory DRAMs. They have also been looked at as a replacement for silicon dioxide in certain MOS applications. 

Tin dioxide thin films can be grown on silicon at room temperature by XeCl excimer laser metal-organic deposition (MOD 100 mJ cm, repetition rate 10 Hz for 5 min) from a solution of Sn(acac)2 in w-BuOH, whereby crystalline films were obtained without heat treatment . Increasing the laser energy to 260 mlcm resulted in an improvement of the crystallinity, which is even better than that of films prepared at 900 °C without laser irradiation. Molloy and coworkers used bimetallic [Sn(dmae)2Cd(acac)2]2 (dmae = dimethylaminoethanol) as precursor for AA-CVD of amorphous Sn02 films, containing no detectable amounts of cadmium. 

In the production of many microelectronic devices, continuous chemical vapor deposition (CVD) processes are used to deposit thin and exceptionally uniform silicon dioxide films on silicon wafers. One CVD process involves the reaction between silane and oxygen at a very low pressure. 

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