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SEMI S6-93 © SEMI 199 3 1 SEMI S6-93 SAFETY GUIDELINE FOR VENTILATION NOTICE: This gu ideline does not pu rport to address all of the safety issues associated with its use. It is the responsibility of t he user of this g…

SEMI S5-0703 © SEMI 1993, 2003 5

Figure 1 Nitrogen Flow Rate

200

400

600

800

1000

1200

1400

1600

1800

2000

700 2100 7000 14000 21000

Cylinder Pressure (kPa)

Nitrogen Flow Rate (slm)

0.15 lo

0.15 hi

0.25 lo

0.25 hi

0.50 lo

0.50 hi

0.75 lo

0.75 hi

1.00 lo

1.00 hi

1.00 mm equiv. orifice

0.75 mm equiv. orifice

0.50 mm equiv. orifice

0.25 mm equiv. orifice

0.15 mm equiv. orifice

Figure 1

Nitrogen Flow Rate

NOTICE: SEMI makes no warranties or representations as to the suitability of the standards set forth herein for any

particular application. The determination of the suitability of the standard is solely the responsibility of the user.

Users are cautioned to refer to manufacture's instructions, product labels, product data sheets, and other relevant

literature, respecting any materials or equipment mentioned herein. These standards are subject to change without

notice.

The user’s attention is called to the possibility that compliance with this standard may require use of copyrighted

material or of an invention covered by patent rights. By publication of this standard, SEMI takes no position

respecting the validity of any patent rights or copyrights asserted in connection with any item mentioned in this

standard. Users of this standard are expressly advised that determination of any such patent rights or copyrights, and

the risk of infringement of such rights, is entirely their own responsibility.

International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o

the contents in whole or in part is forbidden without express written

consent of SEMI.

SEMI S6-93 © SEMI 19931

SEMI S6-93

SAFETY GUIDELINE FOR VENTILATION

NOTICE: This guideline does not purport to address

all of the safety issues associated with its use. It is the

responsibility of the user of this guideline to establish

appropriate safety and health practices and determine

the applicability of regulatory limitations prior to use.

NOTE: As listed or revised, all documents cited shall be the

latest publications of adopted standards.

1 Introduction

The equipment supplier should design an internal

equipment exhaust system that is efficient when

connected to potential users’ exhaust systems. Seldom,

if ever, are users’ systems designed for a specific piece

of process equipment or set of process equipment. Most

users’ exhaust systems are designed and installed to

industry-accepted exhaust principles.

2 Purpose

This document is intended to help the semiconductor

equipment supplier design equipment exhaust systems

to a common set of performance criteria as well as to

provide assistance to both users and suppliers in the

understanding of exhaust requirements for equipment

systems. It is not intended to establish design

specifications. The supplier will still own, and be

responsible for, the information it specifies. This

guideline has six concurrent performance-related

objectives.

2.1 Ensure hazardous gases, fumes, and vapors are

controlled (during normal operations of equipment and

facilities services) such that concentrations present in

the work room air should be less than 1.0% of the

Threshold Limit Value (TLV), as established by the

American Conference of Governmental Industrial

Hygienists (ACGIH) or Permissible Exposure Limit

(PEL) as published by the appropriate regulatory

agency, whichever is lower.

2.2 Ensure exhaust is provided within specifications to

support the proper operation of equipment.

2.3 Optimize the user’s exhaust system(s).

2.4 Use the most cost effective methods to interface

with user’s exhaust systems.

2.5 Provide a platform for communicating “special

case” exhaust requirements.

2.6 Establish guidelines for measurement and

communication of equipment exhaust requirements.

3 Scope

This guideline applies to all semiconductor equipment

that incorporates exhausted enclosures that are intended

to be connected to user facilities’ exhaust system(s).

This document is written with the assumption that the

users’ exhaust distribution systems will be designed

with central fans, ducting, and, where applicable,

abatement equipment. Where users use other types of

exhaust systems, equipment suppliers should acquire

exhaust specifications from the users. Whether

equipment is connected to a central exhaust system or

to one which serves only that piece of equipment, this

guideline should be applied.

4 Referenced Documents (s ee Appendix 2)

5 Terminology

5.1 balancing — Adjustments made after the

ventilated equipment and the ventilation system are

installed to assure that airflow to each piece of

ventilated equipment is within design specifications.

5.2 capture — To entrain undesirable elements (gases,

fumes, vapor, and particles) in the exhaust stream for

removal.

5.3 dilute — To reduce the concentration of

undesirable elements to acceptable levels. Dilution is a

function of flow volume.

5.4 flow velocity (V) — The average speed at which

the effluent stream travels through the exhaust duct. It

is measured in meters per second (m/s) or feet per

minute (fpm).

5.5 flow volume (Q) — The volumetric flow rate of

the effluent stream passing a given location in the

exhaust system per unit of time. It is measured in cubic

meters per second (m

/s) or cubic feet per minute (cfm).

5.6 initiate motion — To use an exhaust stream to start

contaminants (or machine parts) moving from a rest

position.

5.7 long radius elbow — An exhaust duct elbow that

has a center line radius 1.5 or more times the duct

diameter.

5.8 set point tolerance — The range (+/-) of static

pressure within which an exhaust enclosure will

perform efficiently and effectively.

5.9 static pressure (SP) — The measure of differential

pressure across the duct wall to the ambient pressure

SEMI S6-93 © SEMI 1993 2

(inside the duct). The unit of measure is pascals (Pa,

Newtons per square meter (N/m

)) or inches of water.

5.10 traverse measurements — Multiple air flow

measurements taken at points of equal separation, in a

matrix pattern, along the face plane of an exhaust duct

or opening in an exhaust enclosure.

5.11 vena contracta — A point in a duct where the

diameter of the air stream is smaller than the diameter

of the duct.

6 Attributes of Typical Semiconductor

Facilities’ Exhaust Systems

6.1 A typical semiconductor facility’s exhaust system

has three measurable working elements: (1) flow

velocity, (2) flow volume, and (3) pressure.

6.1.1 Flow Volume is related to the Flow Velocity by

the equation Q = VA. In this equation, Q = volumetric

flow rate, V = average velocity, and A = duct cross

sectional area (m

or ft

6.2 There are three duct pressure measurements

possible: (1) static pressure, (2) velocity pressure, and

(3) total pressure.

6.2.1 In exhaust distribution systems with central fans

and abatement equipment (typical of semiconductor

facilities), exhaust duct pressure (static) upstream of the

fan is less than the ambient pressure outside of the duct.

6.2.2 While Velocity Pressure (VP) and Total Pressure

(TP) provide a more reliable measure of Flow than

Static Pressure, VP and TP are normally not specified

for semiconductor facilities’ exhaust systems; therefore,

they will not be discussed in these guidelines. If more

information is desired on VP or TP, it can be found in

“Industrial Ventilation” (Appendix 2, Reference 1).

7 Exhaust Usage Typical of Semiconductor

Operations

Semiconductor equipment typically uses exhaust to

perform one or more of the following tasks:

7.1 Capture — Capture should occur as close to the

source as practical to prevent exposure of personnel or

products to the undesirable elements.

7.1.1 Capture is a function of Flow Velocity. Chapter

3 of “Industrial Ventilation,” A Manual of

Recommended Practice, 20th Edition, (Appendix 2,

Reference 1) outlines the design principles and required

velocity calculations for proper capture of process

emissions.

7.2 Moving is also a function of Flow Velocity. The

exhaust requirements specified by the equipment

supplier should be adequate to maintain motion of

undesirable elements once they are captured in the

exhaust stream.

7.3 Dilution is a function of Flow Volume. Dilution

may also provide reactive elements to undesirable

elements entrained in the exhaust stream (for example,

air and silane).

7.4 Holding — The movement of the exhaust stream is

often used to activate and hold safety control devices,

such as vane switches or differential pressure gauges in

the active state. Such safety control devices should be

used to sense adequate exhaust pressure or flow to

ensure safe operation of the process equipment.

7.5 Initiation of Motion — The use of exhaust to

intiate motion in the semiconductor industry is a special

case application and should be resolved at the time of

purchase. Most semiconductor-related gases, vapors,

fumes, and fine particles (less than 20 microns in

diameter) move with the air in which they are mixed.

8 Key Elements of Exhaust Specifications

8.1 SEMI S2 establishes specific requirements for

exhaust enclosures of equipment that use hazardous

materials. Access to enclosures serving hazardous

materials requires special design. If there is a potential

for exposure of personnel to hazardous materials when

the access hatch is open, an average face velocity

(measured at the hatch opening) sufficient to capture

the hazardous materials should be maintained in the

hatch opening. (SEMI S2 also has recommendations for

exhaust monitoring and alarms. S2 should be fully

understood before designing exhaust systems for

hazardous materials.)

8.2 Properties of chemicals (density, vapor pressure,

boiling point, flammability, etc.), the state of the

materials within the exhausted enclosure (solid, liquid,

or gas), and conditions such as temperature and

concentration will determine the final design and

exhaust specifications of the equipment enclosure.

Equipment suppliers should use available reference

books and Material Safety Data Sheets (MSDS) to

obtain information on chemical properties. The

equipment’s process requirements will dictate the state

and condition of the material.

8.3 When developing specifications for equipment

exhaust systems to be given to the equipment user,

equipment suppliers should incorporate all of the key

elements that will provide clear and accurate

information. These key elements are:

1. Point of measurement.

2. Duct size at the point of measurement.

3. Flow through the duct.