Oxidative CVD

Etch rates in nm s I Thermal oxide CVD- nitride Undoped poly-Si Bulk Si (100) Aluminum... 

We present results for two standard tin oxide precursors, DMTC and MBTC, as well as for tin tetrachloride. The latter compoimd is included in the analysis to provide perspective on the thermal stabihty of the inorganic system relative to the organometalhc ones. All chemical equihbrium calculations were performed with the EQUIL-code from the CHEMKIN-suite [ 100], using the thermochemical data discussed in the previous sections. The temperature range selected was 298-1023 K, the concentration of tin precursor was kept at 2 mol %, while the concentrations of oxygen and water were held at 20 mol % and 5 mol %, respectively. The total pressure was 1 atm. These conditions are similar to those used in commercial tin oxide CVD processes. Note that in the following discussion of reaction mechanisms, all heats of reaction (AHg) are given at 298 K. 

Stripping of chlorine from hydroxides such as Cl2Sn(OH)2 could eventually lead to gas-phase SnO or Sn02. However, at the relatively low temperatures typical of tin oxide CVD ( 873-973 K), we do not expect these oxides to form, based on the equilibrium calculations described above. Thus, the formation of tin hydroxides is not only thermodynamically favored (i.e., based on minimization of the Gibbs free energy), but there are also exothermic reaction pathways that we expect to be kinetically favorable. The primary tin carrier in the CVD process could therefore be a tin hydroxide. Complete conversion to Sn02 would most likely occur via reactions on the surface. 

Our first example that attempts to imravel this complexity is entitled Gas-Phase Thermochemistry and Mechanism of Organometallic Tin Oxide CVD Precursors . The authors, M. Allendorf and A.M.B. van Mol, describe the development of quantum chemistry methods that can predict heats of formation for a broad range of tin compounds in the gas phase, which need to be considered when Sn(CH3)4 or (CH3)2SnCl2 and other tin alkyls are used as precursors together with oxygen and water for tin oxide deposition. 

Gas-Phase Thermochemistry and Mechanism of Organometallic Tin Oxide CVD Precursors... 

R.J. Holdsworth, PA. Martin, D. Raisbeck, and M.E. Pemble, In Situ, Monitoring of Atmospheric Pressure Tin Oxide CVD Using Near-Infrared Diode Laser... 

There are many types of silicon oxides such as thermal oxide, CVD oxide, native oxide, and anodized oxide. Only native oxide and anodic oxide are directly relevant in the context of this book. Anodic oxide film, which is involved in most of the electrochemical processes on silicon electrodes, has not been systematically understood, partly due to its lack of application in mainstream electronic device fabrication, and partly due to the great diversity of conditions under which anodic oxide can be formed. On the other hand, thermal oxide, due to its importance in silicon technology, has been investigated in extremely fine detail. This chapter will cover some aspects of thermal oxide such as growth kinetics and physical, electrical, and chemical properties. The data on anodic oxide will then be described relative to those of thermal oxide. 

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