EEE439 project S24

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Arizona State University *

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439

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Electrical Engineering

Date

Apr 3, 2024

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Semiconductor Facilities and Cleanroom Practices - EEE439/591 Spring '24 – Class Project Create a model for the system below, which is a 10 ft x 10 ft x 1 ft “slice” of a cleanroom, that gives the particle count in any 1 ft 3 unit in the volume (all other slices in the room are numerically identical to this so they can be ignored in this analysis). Assume that air only flows sideways when it is forced to do so by the equipment (dark gray) but ignore the effect of people on airflow. For recirculation purposes, all the air in Zone 1 (light gray) is recirculated whereas the portion of air recirculated in Zone 2 (light blue) depends on the flow rate into this zone and the exhaust flow rate . Test your model with the following “test case” input, which includes two people in the room: • Final filter flow rate = 100 cfm/column • Exhaust flow rate = 125 cfm • Make-up filter efficiency = 99.9% • Recirc filter efficiency = 99.9% • Final filter efficiency = 99.97% • External particle density = 7.5 x 10 5 /ft 3 • Generation rate (per min) of 0.5 µm particles in each ft 3 : 1 2

If you have designed the model properly, for these inputs you should obtain the particle counts (number of particles in each 1 ft 3 volume shown to one decimal place for clarity) shown below. Note that the number of particles penetrating the final filters in each column for these input parameters is around 2.8/min - your model should also give this value (a more exact value is 2.812844707, which is much more precision than you would ever need but it will help you to determine if your model is working!). Since none of the counts in this volume exceeds 100 particles/ft 3 of 0.5 µm diameter, this could be a Class 100 environment under Fed. Std. 209E. Now consider the following scenarios: Case 1. (For all sections of the class.) Better cleanroom garments, materials, and operating practices lead to smaller generation rates inside the room, to give the particle generation map below. Note that the flow rates and final filter efficiency have also been altered. Show the particle counts in the volume. What class under Fed. Std. 209E would this room attain? • Final filter flow rate = 120 cfm/column • Exhaust flow rate = 150 cfm • Make-up filter efficiency = 99.9% • Recirc filter efficiency = 99.9% • Final filter efficiency = 99.997% • External particle density = 7.5 x 10 5 /ft 3 • Generation rate (per min) of 0.5 µm particles in each ft 3 :

Case 2. (For all sections of the class.) For the same internal generation rates as in Case 1 above, an earthquake causes serious damage to the air handlers, HEPA filter grid, and exhaust. The new operating conditions are as follows: Show the particle counts in the volume. Can we still attain the same Fed. Std. 209E class as in Case 1? Case 3. (For EEE 591/graduate sections of the class only .) Select your own input parameters for internal particle generation rates, external particle density, flow rates, and filter efficiencies, and run your model to see how the environment performs. Cite all sources of the values you use. Notes on format of report The report should be in the form of a briefing , using PowerPoint (or similar presentation software) rather than Word, etc., so that the key points are shown as bullets which support the graphics. The content should have the following structure: Slide 1 – report title, your name, affiliation, and a short (100 word max.) summary of the work. Slide 2 – introduction to the issue (why it is important to have a cleanroom model) and a high-level description of your approach (software used, general modelling method). Slide 3 – specifics of your approach, equations, assumptions, and techniques. You must show the equations for local airflow, internal count, recirculation airflow/particle flow, etc., and how you have used them in your model. Slide 4 – test case demonstration, showing that your model gives the same output as the test case. Don’t just show data, add comments to your output. Slide 5 and 6 – “Case 1” and “Case 2”. Don’t just show data, add comments to your outputs. Slide 7 (EEE 591/graduate sections only) – “realistic data case”. Don’t just show data, add comments to your outputs and make sure you include citations for and data used in your inputs. Slide 8 – concluding comments. Discuss what the model shows, possible limitations, and interesting findings. • Final filter flow rate = 75 cfm/column • Exhaust flow rate = 110 cfm • Make-up filter efficiency = 60% • Recirc filter efficiency = 95% • Final filter efficiency = 99.5% • External particle density = 2.5 x 10 6 /ft 3 • Generation rate (per min) of 0.5 µm particles in each ft 3 : same as Case 1

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