Particle Contamination Particle contamination Size of typical air - - PowerPoint PPT Presentation

2011 Monsoon EE669: Contamination Control; Anil Kottantharayil

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Particle Contamination

• Particle contamination

– Size of typical air borne particles can be of the order of magnitude

• f the structural dimensions of the devices and structures to be

made – Sources

• Air
• Human beings: 5000000 to 10000000 particles/minute
• Clean room walls
• Gases and chemicals
• Processes and equipment

www.semguy.com

80µm

2011 Monsoon EE669: Contamination Control; Anil Kottantharayil

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Particle control: clean rooms

• W. Whyte (ed.), Cleanroom Design, IInd edition, Wiley, 1991

HEPA filter: High Efficiency PArticulate filter. Minimum efficiency of particle removal = 99.97% ULPA filter: Ultra Low Penetration Air filter. Efficiency of 99.999% for ~0.1 to 0.2µm

2011 Monsoon EE669: Contamination Control; Anil Kottantharayil

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Particulate Filters

• W. Whyte (ed.), Cleanroom Design, IInd edition, Wiley, 1991

HEPA filter Filter medium: glass fiber

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Clean room classification: ISO 14644-1

Definitions

• Cleanroom or clean zone – room or zone in which the

concentration of airborne particles is controlled, and which is used in a manner to minimize the introduction, generation, and retention

• f particles inside the room, and in which other relevant

parameters, e.g. temperature, humidity and pressure are controlled as necessary

• Classification – the process of specifying the level of airborne

particulate, expressed in terms of an ISO Class N, which represents maximum allowable concentrations (in particles per cubic metre of air) for considered sizes of particles

2011 Monsoon EE669: Contamination Control; Anil Kottantharayil

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Clean room classification: ISO 14644-1

where Cn- is the maximum permitted concentration (in particles per cubic meter

• f air) of airborne particles that are equal to or larger than the considered

particle size, D. Cn is rounded to the nearest whole number. N – is the ISO classification number, which shall not exceed the value of

• 9. Intermediate ISO classification numbers may be specified with 0.1, the

smallest permitted increment of N D – is the considered particle size in micrometers 0.1 – is a constant with dimensions of micrometers Classification number (N) –

Cn =10N 0.1 D ⎛ ⎝ ⎜ ⎞ ⎠ ⎟

2.08

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Clean room classification: ISO 14644-1

ISO Class (N) Maximum Concentration (Cn) of Particles in Air {Particles in each cubic meter equal to or greater than the specified size (D in µm)} Particles size > 0.1 µm > 0.2 µm > 0.3 µm > 0.5 µm > 1 µm > 5 µm ISO Class 1 10 2 ISO Class 2 100 24 10 4 ISO Class 3 1,000 237 102 35 8 ISO Class 4 10,000 2,370 1,020 352 83 ISO Class 5 100,000 23,700 10,200 3,520 832 29 ISO Class 6 1,000,000 237,000 102,000 35,200 8,320 293 ISO Class 7 352,000 83,200 2930 ISO Class 8 3,520,000 832,000 29,300 ISO Class 9 35,200,000 8,320,000 293,000

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Clean room design thumb rules

ISO class Controls Air Velocity: FPM Air changes per hour Filter coverage % of ceiling (filter, air flow) 1 Stringent 70 - 130 > 750 100 (ULPA, UD) 2 Stringent 70 - 130 > 750 100 (ULPA, UD) 3 Stringent 70 - 130 > 750 100 (ULPA, UD) 4 Stringent 70 - 110 500 - 600 100 (ULPA, UD) 5 Stringent 70 - 90 150 - 400 100 (HEPA, UD) 6 Intermediate 25 - 40 60 - 100 33 – 40 (HEPA) 7 Intermediate 10 - 15 25 - 40 10 – 15 (HEPA) 8 Less Stringent 3 - 5 10 - 15 05 – 10 (HEPA)

• W. Whyte (ed.), Cleanroom Design, IInd edition, Wiley, 1991

UD – unidirectional air flow

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CEN Cleanroom Design: CEN clean room

ISO Class 6

HEPA Filters

Fresh Air Damper Pre-filters Cooling Coils Air Blower Balancing Damper Heater Return Air Riser

ISO 6/ 7 Clean room Laminar Flow

Return Air Return Air

30% coverage

Drawing courtesy: Prof. Richard Pinto, EE, IIT-B

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Clean Room Layouts

• W. Whyte (ed.), Cleanroom Design, IInd edition, Wiley, 1991

Ball room design Service chase Mini environment type

2011 Monsoon EE669: Contamination Control; Anil Kottantharayil

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Clean rooms: mini environment

• W. Whyte (ed.), Cleanroom Design, IInd edition, Wiley, 1991

2011 Monsoon EE669: Contamination Control; Anil Kottantharayil

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Particle Contamination

• Particle contamination

– Size of typical air borne particles can be of the order of magnitude

• f the structural dimensions of your devices and structures you

make – Sources

• Air
• Human beings: 5000000 to 10000000 particles/minute
• Clean room walls
• Gases and chemicals
• Processes and equipment

With permission from www.semguy.com

80µm

2011 Monsoon EE669: Contamination Control; Anil Kottantharayil

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Particle Contamination: human beings in cleanrooms

• All exposed parts of our body and cloths carry contaminants

– Skin – Exhalation – Hair – Apparel – Costumes

• Wear lint free bunny suits, hair nets, goggles, hand gloves – do not

expose any part of your body in clean rooms

• Reduce the presence of human beings in clean rooms – more

automation Fats, salts, bacteria & fungi Hair, particles & fibers

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Particle control requirements: example ITRS 2001

ITRS 2001 edition