Engineering >> Chemical & Biomedical EngineeringDepostion of Silicon Dioxideby Adrian Bociu
Submitted : Fall 2010 The problem was divided into 3 parts. Part a asked for the initial partial pressure of tetraethylsilane (TEOS) in the reactor if the desired thickness of the passivation layer is 150 nm. To find the initial partial pressure, first the volume of the layer needed to be established by using the equation for the volume of a cylinder. Using the density of silicon dioxide (SiO2) and the volume calculated, the mass of SiO2 can be found out. The molecuar weight of SiO2 was then used to convert the mass of SiO2 into moles of SiO2. Once the number of moles of SiO2 was established, the one-to-one relationship between moles of TEOS and moles of SiO2 was used to determine the moles of TEOS that are to be reacted. The final step involved in finding the initial partial pressure of TEOS was to use the ideal gas law using the given values of pressure, temprerature and volume to give an initial partial pressure. Part b asked for the rate constant. This was done by plotting the given values of the rate with respect to the square root of the given partial pressures. Then a linear regression was performed in Microsoft Excel, the slope of the line was the rate constant,k. Part c asked for the time it would take for all of the TEOS carged to the reactor to react. This was done by substituting in the rate expression into the governing equation for the rate of deposition. After this the variables were separated and the differential equation was solved to give the time required, 96.6 seconds.
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