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Pr0x1mo
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Homework Statement
In the semiconductor industry, integrated circuit (IC) production begins with the mechanical
slicing of silicon rods into wafers. Once the wafers are sliced, the surfaces are lapped and
polished to uniform flat surfaces. Contaminants and microscopic defects (work damage) are then removed chemically by etching. A tradition etching solution consists of a 4:1:3 volumetric ratio of 49% hydrofluoric (HF), 70% nitric (HNO3), and 100% acetic (CH3CO2H) acids, respectively.
Although work damage is usually 10 μm deep, overetching to 20 μm per side is common. The
reaction for dissolving the silicon surface is:
3 Si + 4 HNO3 + 18 HF -> 3 H2SiF6 + 4 NO + 8 H2O
Calculate the flow rate of the etching solution in kilograms per hour if 20μm per side is to be
etched for 6000 wafers per hour of 150 mm diameter. What is the limiting reagent?
Si – 2.33 g/cm3 M.W. 28.09g/mol
Sp gr 49% HF is 1.198 M.W. 20.01g/mol
Sp gr 70% HNO3 is 1.4134 M.W. 63.01g/mol
Sp gr 100% CH3CO2H is 1.0492 M.W. 60.05g/mol
Ok, this is a question that i have for my chemical engineering class, its one out of 10 questions (its not due, or has to be done). But looking at it, i want to know how to solve this. I've tried looking up in my textbook for a way to calculate this but i couldn't find anything on it. Maybe my teacher pulled this question from another book.
I don't even know the first step into solving this. Can someone get me on the right track?