As it has been recognized previously in the first memo Silicon Nitride (Si3N4) is manufactured by using Low Pressure Chemical Vapor Deposition. OSU’s Virtual CVD reactor is an apparatus demonstrating the growth and measurements of Silicon Nitride. It might be essential not to just manufacture Silicon Nitride, instead, to produce it in a high quantity and quality spending the least amount of money as possible. In order to manufacture this type of aforementioned Silicon Nitride, it is required to set proper measurements to pressure, the flow rate of ammonia and dichlorosilane, time and 5 zones of temperature which have dimensions such as 200mtorr, 1000sccm for ammonia and 160sccm for dcs, 120-140 minutes and 700-800 ̊̊̊C respectively. In addition, one of the main aims is to have Silicon Nitride of 750 Å thickness which is tested by using equipment called a Virtual ellipsometer. Also the spaces among wafers should be 6.35 mm and the furnace has 200 wafers which have dimension of 300mm each. The objective of this memo is to attempt to define an ideal “recipe” for producing Si3N4 by setting proper measurements in order to gain the Silicon Nitride of high quality and quantity.
One of the 9 parameters that should be adjusted is the deposition time. The initial reaction time could be varied between 120 and 140 minutes. The deposition time strongly affect the thickness of silicon nitride wafers, there is a linear dependence between deposition time and thickness. (Velasko A.A, 2002) In addition to this, when the deposition time is increased and flow rate is decreased; there is an increase in thickness. (Velasko A.A, 2002) Controlled temperature and time provide better uniformity in the thickness. It means, that with an increase in time, the number of collisions during the chemical reactions will be larger, which leads to more layers within the film. That is why the deposition time should be minimal to produce high-qualitative silicon nitride wafers. Therefore, the deposition time for the first experiment would be 120 minutes.
Next parameter is pressure. Pressure during the experiments would be fixed, p= 200mtorr, in order to do the experiments more comfortably (decrease the number of possible experiments because of their cost).
Another two of the parameters which we can adjust are the flow rates of dichlorosilane (DCS) and ammonia (NH3). The given ranges for them are 130-160sccm and 1000-2000sccm respectively. These parameters also can be represented in the form of total flow rate and NH3: DCS flow rate ratio. They strongly affect various characteristics of the process: for instance, according to Campbell (1996) the concentration of DCS can be increased in order to avoid high stress. At the same time, higher NH3:DCS flow rate ratio allows us to obtain a product with appropriate refractive index within the 1.8-2.2 range and deposition rate (Tonnberg S., 2006). Finally, the increase of total flow rate will also lead to deposition rate and final...