Semiconductor Facilities and Cleanroom Practices Project

Semiconductor Facilities and Cleanroom Practices - EEE439/591 Spring '26 – Class Project

Consider the 10 ft x 10 ft x 1 ft “slice” of a cleanroom below. Create a computer model for this part of the cleanroom that gives the particle count in any 1 ft3 unit. Assume that the air flows vertically in each column and only flows laterally when it is forced to do so by the equipment (dark gray) or the exhaust (orange). Ignore the effect of people on airflow direction – only consider their particle generation. To simplify the recirculated particle calculations, assume all the air in Zone 1 (light gray) is recirculated whereas the portion of air recirculated in Zone 2 (blue) depends on the flow rate into this zone (two columns) and the exhaust flow rate. The exhausted air is the only loss from the system and must be replaced by the make-up airflow.

Test your model with the following conditions to produce a particle count map and determination of cleanroom class in each case:

1. Normal operation.

HEPA filters (supply)

Grated floor (return)

Make-up AHU

Recirc AHU

Make-up prefilters

Recirc prefilters

2 1

Exhaust

 Final filter flow rate = 100 cfm/column  Exhaust flow rate = 100 cfm  Make-up filter efficiency = 99.9%  Recirc filter efficiency = 99.8%  Final filter efficiency = 99.97%  External particle density = 5 x 105/ft3  Generation rate (per min) of 0.5 µm particles in each ft3 - see Generation Map 1

2. Enhanced operation.

3. Disaster scenario.

4. Real world data (For EEE 591/graduate sections of the class only).

Provide 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 submission

You are required to submit a report and an Excel file.

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.

 Final filter flow rate = 120 cfm/column  Exhaust flow rate = 90 cfm  Make-up filter efficiency = 99.95%  Recirc filter efficiency = 99.9%  Final filter efficiency = 99.997%  External particle density = 5 x 105/ft3  Generation rate (per min) of 0.5 µm particles in each ft3 - see Generation Map 2

 Final filter flow rate = 50 cfm/column  Exhaust flow rate = 30 cfm  Make-up filter efficiency = 95%  Recirc filter efficiency = 90%  Final filter efficiency = 99%  External particle density = 106/ft3  Generation rate (per min) of 0.5 µm particles in each ft3 - see Generation Map 3

Slide 4 – normal operation case, showing airflow in each unit, cumulative number of particles entering each unit, and particle counts in each unit, as well as the number of particles penetrating the final filters and the expected cleanroom class (according to Fed. Std. 209). Add comments to your outputs.

Slide 5 – enhanced operation case, showing airflow in each unit, cumulative number of particles entering each unit, and particle counts in each unit, as well as the number of particles penetrating the final filters and the expected cleanroom class (according to Fed. Std. 209). Add comments to your outputs.

Slide 6 – disaster scenario case, showing airflow in each unit, cumulative number of particles entering each unit, and particle counts in each unit, as well as the number of particles penetrating the final filters and the expected cleanroom class (according to Fed. Std. 209). Add comments to your outputs.

Slide 7 (EEE 591/graduate sections only) – real world data case, showing airflow in each unit, cumulative number of particles entering each unit, and particle counts in each unit, as well as the number of particles penetrating the final filters and the expected cleanroom class (according to Fed. Std. 209). Add comments to your outputs.

Slide 8 – concluding comments. Discuss what the model shows, possible limitations, and interesting findings.

The Excel file should contain your particle counts (numerical results, not formulas or macros) and the expected cleanroom class for the three operational cases. These results should be entered into the appropriate cells in the template. The real world data case (graduate sections only) should not be put in this file. Replace the template name “Lastname_Firstname_XXX.xlsx” with your own first name and last name (as they appear on Canvas) and your course number (439 or 591). Do not alter the template file, other than pasting in your numerical results for the particle count map, and keep the underscores_in_the_filename!

Generation Map 1 - generation rate (per min) of 0.5 µm particles in each ft3 unit. Nominal airflows, filter efficiencies, and particle generation rates.

2 0 0 0 0 0 0 0 0 2

1 0 0 0 0 0 0 0 0 5

1 0 0 0 0 0 0 0 25 10

5 0

0 0 0 0 0 0 50 30

40 20 0 2500 0 0 0 0 60

60 150 400 150 50 50 2000 50

600 150 500 300 500 100 400 300 300

200 300 150 150 300 200

200 300 150 150 300 200 200

500 750 500 300 650 300 300

Generation Map 2 - generation rate (per min) of 0.5 µm particles in each ft3 unit. Better filters, cleanroom garments, materials, and operating practices lead to smaller generation rates, to give the particle generation map below. Note that the flow rates have also been altered.

0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 2 1

0 0 0 0 0 0 0 0 4 3

4 2 0 200 0 0 0 0 5

5 20 40 20 5 50 200 5

100 10 40 30 40 8 40 300 40

20 30 20 20 30 20

20 30 20 20 30 20 20

40 60 40 40 60 40 30

Generation Map 3 - generation rate (per min) of 0.5 µm particles in each ft3 unit. An earthquake causes serious damage to the facility and causes higher particle generation rates.

10 0 0 0 0 0 0 0 0 10

10 0 0 0 0 0 0 0 0 10

10 0 0 0 0 0 0 0 30 10

100 0 0 0 0 0 0 0 80 150

200 40 0 2500 0 0 0 0 120

100 150 400 150 50 50 2000 150

800 200 500 300 500 100 400 300 300

200 300 150 150 300 200

200 300 150 150 300 200 300

500 750 500 500 750 500 400