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SEMI S2-0703a E © SEMI 1991, 2004 34 APPENDIX 2 DESIGN PRINCIPLES AND TEST METHODS FOR EVALUATING EQUIPMENT EXHAUST VENTILATIO N — Design and Test Method Supplement Intended for Internal and Third Party Evaluation Use NO…

SEMI S2-0703a

APPENDIX 1

ENCLOSURE OPENINGS

NOTICE: The material in this appendix is an official part of SEMI S2 and was approved by full letter ballot

procedures on December 15, 1999 by the North American Regional Standards Committee.

A1-1 This appendix provides guidance on sizes of

openings in enclosures.

Table A1-1 Examples of Openings for Protection

Against Access from Operators

Distance Between Opening

and Danger Point

Maximum Opening

mm inches mm inches

13–38 0.5–1.5 6 0.250

38–64 1.5–2.5 10 0.375

64–89 2.5–3.5 11.9 0.470

89–140 3.5–5.5 16 0.625

140–165 5.5–6.5 19 0.750

165–191 6.5–7.5 22 0.875

A1-1.1 Alternatively, an IEC accessibility probe, as

specified in SEMI S9, may be used to determine

suitability of mesh openings.

A1-2 Top Openings in Electrical Enclosures — The

top openings in electrical enclosures should meet one of

the following:

 not exceed 5 mm in any dimension, or

 not exceed 1 mm in width regardless of length, or

 be so constructed that direct, vertical entry of a

falling object is prevented from reaching

uninsulated live parts within the enclosure by

means of trap or restriction (see Figure A1-1 below

for examples of top cover designs that prevent such

direct entry), or

 meet the intent through other equivalent means.

Figure A1-1

SLANTED OPENINGS VERTICAL OPENINGS

SEMI S2-0703a

APPENDIX 2

DESIGN PRINCIPLES AND TEST METHODS FOR EVALUATING

EQUIPMENT EXHAUST VENTILATION — Design and Test Method

Supplement Intended for Internal and Third Party Evaluation Use

NOTICE: The material in this appendix is an official part of SEMI S2 and was approved by full letter ballot

procedures on December 15, 1999 by the North American Regional Standards Committee.

A2-1 Introduction

A2-1.1 This appendix provides specific technical

information relating to Section 22. In general, it

provides guidelines for:

 ventilation design for semiconductor manufac-

turing equipment, and

 test validation criteria.

A2-1.2 This appendix is intended to be used as a

starting point for reference during equipment design.

A2-1.3 This appendix is not intended to limit hazard or

test evaluation methods or control strategies (e.g.

design principles) employed by manufacturers or users.

Many different methods may be employed if they

provide a sufficient level of protection.

A2-1.4 This appendix is not intended to provide

exhaustive methods for determining final ventilation

specifications. Other methods may be used where they

provide at least equivalent sensitivity and accuracy.

A2-1.5 The exhaust velocities, volume flow rates and

pressures listed are derived from a mixture of

successful empirical testing and regulatory

requirements.

A2-1.6 Test validation criteria are generally referenced

from the applicable internationally recognized standard.

It is the user’s responsibility to ensure that the most

current revision of the standard is used.

Table A2-1 Ventilation

Hood Type Recommended Test Methods Typical Design and Test Exhaust

Parameters (See NOTE 1.)

References

Wet Station Primary: vapor visualization, air

sampling

Supplemental: Capture velocity, slot

velocity, tracer gas, air sampling

0.28–0.50 m/s (55–100 fpm) capture

velocity for non-heated

0.36–0.76 m/s (70–150 fpm) capture

velocity for heated

110–125% of the laminar flow

volume flow rate across the top of

the deck

ACGIH Industrial

Ventilation Manual

SEMI F15

Gas Cylinder

Cabinets

Primary: face velocity, tracer gas

Supplemental: vapor visualization

1.0–1.3 m/s (200–250 fpm) face

velocity

ACGIH Industrial

Ventilation Manual

SEMI F15

Equipment Gas

Panel Enclosure

Primary: tracer gas, static pressure

Supplemental: vapor visualization

4–5 air changes per minute

–1.3 to –2.5 mm (–0.05 to –0.1 in.)

O static pressure

ACGIH Industrial

Ventilation Manual

SEMI F15

Diffusion

Furnace

Scavenger

Primary: face velocity, vapor

visualization

Supplemental: tracer gas, air sampling

0.50–0.76 m/s (100–150) fpm face

velocity

NOTE: Do not use hot wire

anemometer.

ACGIH Industrial

Ventilation Manual

SEMI F15

Chemical

Dispensing

Cabinets

Primary: static pressure

Supplemental: vapor visualization, air

sampling where safe, tracer gas where

emission rates can be accurately

calculated

–1.3 to –2.5 mm (–0.05 to –0.1 in.)

O static pressure

2–3 air changes per minute

ACGIH Industrial

Ventilation Manual

SEMI F15

SEMI S2-0703a

Hood Type Recommended Test Methods Typical Design and Test Exhaust

Parameters (See NOTE 1.)

References

Parts-Cleaning

Hoods

Primary: face velocity, vapor

visualization

Supplemental: tracer gas, air sampling

0.40–0.64 m/s (80–125 fpm) face

velocity

ASHRAE Standard 110

SEMI F15

ACGIH Industrial

Ventilation Manual

Pump and

Equipment

Exhaust Lines

Primary: static pressure

Supplemental: tracer gas

–6 to –25 mm (–0.25 to –1.0 in.)

O static pressure

125% maximum volume flow rate

from pump

ACGIH Industrial

Ventilation Manual

SEMI F15

Glove Boxes Primary: static pressure, tracer gas

Supplemental: vapor visualization, air

monitoring

No consensus for a reference at the

time of publication of this guideline.

ACGIH Industrial

Ventilation Manual

SEMI F15

Drying/ Bake/

Test Chamber

Ovens

Primary: static pressure, tracer gas

Supplemental: vapor visualization, air

monitoring

–1.3 to –2.5 mm (–0.05 to –0.1 in.)

O static pressure

SEMI F15

ACGIH Industrial

Ventilation Manual

Spin-Coater

(cup only)

Primary: vapor visualization,

velometry

Supplemental: air sampling

(see SEMI S2 Sections 23.5.1–3) ACGIH Industrial

Ventilation Manual

Supplemental

Exhaust

Primary: capture velocity, vapor

visualization, air sampling

0.50–0.76 m/s (100–150 fpm)

capture velocity

ACGIH Industrial

Ventilation Manual

NOTE 1: All measurements should be within ± 20% of average for face velocity, ± 10% of average along the length of each slot for slot velocity,

and ± 10% of average between slots for slot velocity.

A2-2 Exhaust Optimization

A2-2.1 Exhaust optimization is the use of good

ventilation design to create efficient equipment exhaust.

The design and measurement methods discussed below

confirm that equipment exhaust is acting as the

manufacturer intended. This information is not meant to

prohibit alternate methods of achieving or verifying

good ventilation design. References for ventilation

design are included at the end of this Appendix.

A2-2.2 Design Recommendations

A2-2.2.1 Equipment exhaust design can attempt to

reduce inefficient static pressure losses caused by:

friction losses from materials; openings, and duct

geometries (elbows, duct expansions or contractions);

turbulent air flow; fans; internal fittings such as blast

gates and dampers; directional changes in airflow.

A2-2.2.2 Other good design principles can include

minimizing distance between the source and hood, and

reducing enclosure volumes.

A2-2.2.3 For non-chemical issues such as heat from

electrical equipment, heat recapture rather than exhaust

may be appropriate.

A2-2.2.4 The possible impact of highly directional

laminar airflow found in most fabs should be

considered when designing equipment exhaust.

A2-2.3 Recommended Equipment Controls — The

location of internal blast gates or dampers inside

equipment, and their appropriate settings, should be

clearly identified. The number of equipment dampers

and blast gates should be minimized. Gates/dampers

should be lockable or otherwise securable. Static

pressure or flow sensors installed on equipment by the

manufacturer should have sufficient sensitivity and

accuracy to measure exhaust flowrate fluctuations that

place the equipment out of prescribed ranges.

A2-2.4 Recommended Measurement/Validation

Method — Measurements should be made to identify

optimal exhaust levels and confirm that safety and

process requirements are being addressed. The

manufacturer should be able to identify any critical

equipment locations for chemical capture, and quantify

appropriate exhaust values. Multiple validation/

measurement methods may be needed.

A2-2.4.1 Measurements should be done after

equipment components are assembled.

A2-2.4.2 Computer modeling can be done to predict

exhaust flow and hazardous material transport in

equipment by solving fluid mechanics conservation of

energy and mass equations. Modeling can be used in

the equipment design stage or to improve existing

equipment. Computer models should be verified

experimentally, using one or more of the methods

discussed below.

A2-2.4.3 Tracer gas testing provides a method to test

the integrity of hoods by simulating gas emission and

measuring the effectiveness of controls. Testing until