Synthesis And Properties Of Chlorosilanes And Their Derivatives

Since 1960, silicon-based thin films such as silicon nitride(SiNx), amorphous silicon(α-Si), silicon carbide(SiC), polycrystalline silicon, silicon carbonitride(SiCN), silicon oxide(SiO2) and carbon incorporated silicon oxide(SiOC), have shown a wide range of properties and have various applications in integrated circuits technology, because they are easily integrated, low cost, optional to substrates and well-behaved. In recent years, with the development of IC industry to miniaturized and intelligent level, requirements of film performance become higher and higher. Therefore, precursors begin to catch headlines, which play the same important role with CVD processing factors.Currently, many precursors, such as traditional SiH4, Si2H6, SiCl4, SiF4, Si2Cl6 and new-style amido/alkyl substituted silanes, have been used to manufacture silicon-based thin films. Among these precursors, the toxicity of silanes and corrosivity of halides have limited their scale application. Futhermore, Si-H bonds of these new-style amido/alkyl substituted silanes make them sensitive to air moisture. The introduction of gaseous dimethylamine increased the difficulty in synthesis and extra request to the apparatus. Meanwhile, available precursors are not enough in amounts to meet the huge needs.Thus, the search for new silicon precursors is still a great challenge not only for the above-mentioned reasons but also because the chemical and physical properties of the Si source can be adjusted by various ligands/substituents in order to obtain films with many particular properties and thereby satisfy different application requirements.On the basic of these studies, herein, we report the synthesis of Si2Cl6 through a solid-liquid system. And many silicon compounds were synthesed by derivatizations of SiMe3 Cl with guanidine/amidine, aminopyridine and β-diketimines ligands respectively. Their thermal properties were tested and discussed to determine their potential as CVD precursors.Detailed contents are as follows:1. Si2Cl6 was synthesed through a solid-liquid reaction of SiCl4 with ferrosilicon powder in high yield(60%) for the first time, which was catalyzed by Cu(I) complexes. The device is simple and easy to operate. Compared to the existing gas-solid methods with yield 10~20%, the synthesis difficulty and the cost are greatly reduced.2. According to requirements for CVD precursors and the relationship between their structures and properties, liquid secondary amine and primary amine were first selected as ligands for derivatization of Si2Cl6, obtaining a total of 12 products, which was expected to resolve the corrosion problem by chlorosilane radically.3. Guanidine/amidine, aminopyridine and β-diketimines were selected as ligands respectively for derivatization of SiMe3 Cl, obtaining a total of 24 products. A series of characterization was conducted to determine their structures. The coordination behavior of the central silicon is discussed, which resolved the controversy in this field.4. The thermal behaviors of all 36 products for evaluating them as CVD precursors were measured by simultaneous thermal analyses(STA) including thermogravimetric analysis(TGA) and differential scanning calorimetry(DSC). Further attempts at film deposition were made through a hot-wall CVD reactor, using these precursors, which have verified their abilities as CVD precursors to manufacture silicon-based thin films. Two rules concerning the elationship between their structures and volatility were found as follows: 1) the volatility decreases with the increase in the molecular weight(Mw) of these compounds/ligands; 2) for compounds with the same or similar Mw, compounds with branched/bulky ligands possess better volatility. This suggests the future strategy for the design of new CVD silicon-based precursors.