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SEMI S2-0703a E © SEMI 1991, 2004 26  where segregation facilitates recycling or reuse; or  where separate abatement or t reatment met hods are required. NOTE 103: It is recommended that the equipment design documentat…

SEMI S2-0703a

 reduced use of resources during maintenance

procedures (e.g., parts cleaning procedures could

include minimum rinse rates and rinse times);

 recycling or reusing chemicals in the equipment,

rather than consuming only new materials;

 reducing volume of packaging, increasing recycled

content of packaging, and/or designing reusable

packaging.

21.2.3 Chemical Selection

21.2.3.1 Chemical selection for process, maintenance,

and utility uses (e.g., gases, etchants, strippers, cleaners,

lubricants, and coolants) should take into account

effectiveness, environmental impacts, volume, toxicity,

by-products, decommissioning, disposal, and

recyclability; use of the least hazardous chemical is

preferred. To the extent practicable, the utilities,

maintenance, and process should be designed so that

the equipment operates without the use of:

 ozone depleting substances (ODSs) as identified by

the Montreal Protocol, such as chlorofluorocarbons

(CFCs), methylchloroform, hydrochlorofluoro-

carbons (HCFCs), and carbon tetrachloride, or

 perfluorocompounds (PFCs), including CF

, C

, and SF

, and CHF

due to their global

warming potential.

21.2.4 Prevention and Control of Unintended Releases

21.2.4.1 Equipment design, including feed, storage,

and waste collection systems, should prevent potential

unintended releases. At a minimum:

21.2.4.2 Secondary containment for liquids should be

capable of holding at least 110% (see first row of Table

A3-1 of Appendix 3) of the volume of the single largest

container, or the largest expected volume for any single

point failure.

NOTE 99: In some circumstances secondary containment

may be specified by the equipment supplier, but provided by

the user.

21.2.4.3 Chemical storage containers and secondary

containment should be designed for accessibility and

easy removal of collected material.

21.2.4.4 Secondary containment should have alarms

and gas detection or liquid sensing, as appropriate, or

have recommended sensing points identified in the

equipment installation instructions.

21.2.4.5 Equipment design should allow personnel to

determine all in-equipment container levels

conveniently without having to open the containers,

where ignorance of the level could result in an

inadvertent release.

21.2.4.6 Overfill level detectors and alarms should be

provided for in-equipment containers.

21.2.4.7 Secondary containment and other control

systems should be designed to ensure that chemicals

cannot be combined, where the combination could

result in an inadvertent release.

21.2.4.8 Equipment components should be compatible

with chemicals used in the manufacturing process.

Chemical systems should be designed for the specified

operating conditions, and have sufficient mechanical

strength and corrosion resistance for the intended use.

21.2.4.9 Equipment should be able to accept a signal

from a monitoring device and stop the supply of

chemical, at the first non-manual valve within the

affected system.

21.2.4.10 Chemical distribution systems should be

capable of automatic shutoff and remote shutdown.

21.2.5 Effluents, Wastes, and Emissions

NOTE 100: It is recommended that the manufacturer

document its efforts to minimize the equipment’s generation

of hazardous wastes, solid wastes, wastewater, and air

emissions.

NOTE 101: It is recommended that SEMI F5 be used for

guidance in gaseous effluent handling.

21.2.5.1 Equipment design that allows connection to a

central waste collection system is preferred, except

where collection at the equipment may facilitate

recycling or reuse opportunities or otherwise reduce

environmental impacts.

NOTE 102: It is recommended that individual drains and

exhausts be kept separate (e.g., separate outlets for acid drain,

solvent drain, deionized (DI) water drain; acid exhaust,

solvent exhaust).

21.2.5.1.1 Point-of-use collection containers should be

designed for accessibility as well as the possible reuse

and recycling of the collected materials.

21.2.5.2 Equipment should use partitions, double-

contained lines, or other similar design features to

prevent the mixing of incompatible waste streams.

21.2.5.3 The manufacturer should evaluate the

feasibility of including integrated controls for effluent

and emission treatment.

21.2.5.4 Dilution in excess of process or safety

requirements should not be used to reduce contaminant

discharge concentrations.

21.2.5.5 Segregation of effluents, wastes, and

emissions should be provided in the following cases:

 where chemically incompatible;

SEMI S2-0703a

 where segregation facilitates recycling or reuse; or

 where separate abatement or treatment methods are

required.

NOTE 103: It is recommended that the equipment design

documentation show evidence of consideration of by-products

generated during equipment operation, clean-up, maintenance,

and repair. By-products can include deposits in drains or

ducts, and replaceable parts (e.g., batteries, vapor lamps,

contaminated parts).

21.2.6 Decommissioning and Disposal

21.2.6.1 Equipment design should address (see Section

8.5.3 for documentation provisions) construction

material and component reuse, refurbishment, and

recycling.

21.2.6.2 The equipment should be designed to facilitate

equipment decontamination and disposal, e.g., by use of

removable liners or replaceable modules. This includes

minimizing the number of parts that become

contaminated with hazardous materials.

NOTE 104: It is recommended that SEMI S12 “Guidelines

for Equipment Decontamination” be used for guidance during

equipment decontamination.

22 Exhaust Ventilation

22.1 Equipment exhaust ventilation should be designed

to prevent potentially hazardous chemical exposures to

employees as follows:

22.1.1 As primary control when normal operations

present potentially hazardous chemical exposures to

employees by diffusive emissions that cannot be

otherwise prevented or controlled (e.g., wet decks, spin

coaters).

NOTE 105: In the context of this section, “primary control”

means that it is the control of first choice (e.g., rather than

personal protective equipment).

22.1.2 As supplemental control when intermittent

activities (e.g., chamber cleaning, implant source

housing cleaning) present potentially hazardous

chemical exposures to employees which cannot

reasonably be controlled by other means. Supplemental

exhaust hoods or enclosures may be integrated into the

equipment design, or supplied completely by the

equipment user.

22.1.2.1 When a procedure (e.g., cleaning) specified by

the supplier requires exhaust ventilation, the supplier

should include the minimum criteria for exhaust during

the procedure.

22.1.3 As secondary control when a single-point

failure presents the potential for employee exposures to

hazardous materials, and this exposure cannot be

controlled by other means (e.g., use of all welded

fittings).

EXCEPTION: Secondary exhaust control enclosures

for non-welded connections (e.g., valve manifold boxes

that enclose piping jungles) are not included in this

guideline for those hazardous gases that are transported

below atmospheric pressure (e.g., via vacuum piping

systems) if it can be demonstrated that equivalent leak

protection is provided. Equivalent protection may

include such things as equipping the vacuum delivery

system with a fail-safe (e.g., to close) valve

automatically activated by a loss of vacuum pressure.

Loss of vacuum pressure should also activate a visual

and audible alarm provided in visual or audible range of

the operator.

22.2 Equipment exhaust ventilation should be designed

and a ventilation assessment conducted (see Section

23.5, Appendix 2, and SEMI S6) to control, efficiently

and safely, for potential worst-case, realistic employee

exposures to chemicals during normal operation,

maintenance, or failure of other equipment components

(hardware or software). All design criteria and test

protocols should be based on recognized methods. See

also Section 23.3.

22.3 Documentation should be developed showing the

equipment exhaust parameters and relevant test

methods, and should include (see also Appendix 2):

 duct velocity (where needed to transport solid

particles);

 volumetric flow rate Q;

 capture velocity (where airborne contaminants are

generated outside an enclosure);

 face velocity (where applicable);

 hood entry loss factor F

or K;

 coefficient of entry C

;

 hood static pressure SP

;

 duct diameter at the point of connection to

facilities; and

 location(s) on the duct or hood where all

ventilation measurements were taken.

22.4 Exhaust flow interlocks should be provided by the

manufacturer on all equipment that uses hazardous

production materials (HPMs) where loss of exhaust

may create a hazard. Flow (e.g., pitot probe) or static

pressure (e.g., manometer) switches are the preferred

sensing methods.

SEMI S2-0703a

NOTE 106: Sail switches (switches that are connected to a

lever that relies upon air velocity to activate) are generally not

recommended.

NOTE 107: It is recommended that the pressure or flow

measuring point be located upstream of the first damper.

NOTE 108: Section 11 contains provisions for safety

interlocks.

22.4.1 When the exhaust falls below the prescribed set

point, an alarm should be provided within audible or

visible range of the operator, and the process equipment

should be placed in a safe stand-by mode. A time delay

and exhaust setpoint for the equipment to go into

standby mode may be allowable, based on an

appropriate risk assessment. The system should be

capable of interfacing with the facility alarm system.

NOTE 109: It is recommended that non-HPM chemical

process exhaust be equipped with audible and visible

indicators only.

22.4.2 Exhaust flow interlocks and alarms should

require manual resetting.

22.4.3 Exhaust flow interlocks should be fault-tolerant.

22.5 Equipment and equipment components should be

designed using good ventilation principles and practices

to ensure chemical capture and to optimize exhaust

efficiency (see Appendix 2).

NOTE 110: It is recommended that exhaust optimization be

achieved with total equipment static pressure requirements of

–1 to –38 mm (–0.05 to –1.5") H

O (see also Section A2-1 of

Appendix 2, and Section 8.3.6.1 of SEMI S6-93).

23 Chemicals

23.1 The manufacturer should generate a chemical

inventory identifying the chemicals anticipated to be

used or generated in the equipment. At a minimum, this

should include chemicals in the recipe used for

equipment qualification or “baseline” recipe, as well as

intended reaction products and anticipated by-products.

Chemicals on this list that can be classified as

hazardous production materials (HPMs), or odorous

(odor threshold < 1 ppm) or irritant chemicals

(according to their material safety data sheets), should

also be identified.

23.2 A hazard analysis (see Section 6.8) should be

used as an initial determination of chemical risk as well

as to validate that the risk has been controlled to an

appropriate level.

23.2.1 The hazard analysis, at a minimum, should

address the following conditions:

 potential mixing of incompatible chemicals;

 potential chemical emissions during routine

operation;

 potential chemical emissions during maintenance

activities; and

 potential key failure points and trouble spots (e.g.,

fittings, pumps).

23.2.2 All routes of exposure (e.g., respiratory, dermal)

should be considered in exposure assessment.

23.3 The order of preference for controls in reducing

chemical-related risks is as follows:

23.3.1 substitution or elimination (see also Section

21.2.2);

23.3.2 engineering controls (e.g., enclosure,

ventilation, interlocks);

23.3.3 administrative controls (e.g., written warnings,

standard operating procedures);

23.3.4 personal protective equipment.

23.4 The design of engineering controls (e.g.,

enclosure, ventilation, interlocks) should include

consideration of (see also Appendix 3):

 pressure requirements;

 materials incompatibility;

 equipment maintainability;

 chemical containment; and

 provisions for exhaust ventilation (see Section 22).

23.5 During equipment development, the supplier

should conduct an assessment that documents

conformance to the following airborne chemical control

criteria (see also Appendix 2). All measurements should

be taken using recognized methods with documented

sensitivities and accuracy. A report documenting the

survey methods, equipment operating parameters,

instrumentation used, calibration data, results, and

discussion should be available.

23.5.1 There should be no chemical emissions to the

workplace environment during normal equipment

operation. Conformance to this section can be shown by

demonstrating ambient air concentrations to be less

than 1% of the Occupational Exposure Limit (OEL) in

the worst-case personnel breathing zone. Where a

recognized method does not provide sufficient

sensitivity to measure 1% OEL, then the lower

detection limit of the method may be used to satisfy this

criterion.

23.5.2 Chemical emissions during maintenance

activities should be minimized. Conformance to this