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SEMI S2-0703a E © SEMI 1991, 2004 27 NOTE 106: Sail switches (switches that are connect ed to a lever that relies upon air velocity to activate) are generally not recommended. NOTE 107: It is recommended that the pr essu…

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

SEMI S2-0703a

section can be shown by demonstrating ambient air

concentrations to be less than 25% of the OEL, in the

anticipated worst-case personnel breathing zone, during

maintenance activities.

23.5.3 Chemical emissions during equipment failures

should be minimized. Conformance to this section can

be shown by demonstrating ambient air concentrations

to be less than 25% of the OEL, in the anticipated

worst-case personnel breathing zone, during a realistic

worst-case system failure.

NOTE 111: The use of direct reading instrumentation under

simulated operating, maintenance, or failure conditions is the

preferred measurement method. Where used, it is

recommended that the sample location(s) be representative of

the worst-case, realistic exposure locations(s). It is

recommended that the peak concentration be directly

compared to the OEL to demonstrate conformance to Sections

23.5.1–23.5.3.

NOTE 112: It is recommended that integrated sampling

methods be used when direct-reading instrumentation does

not have adequate sensitivity, or when direct-reading

technology is not available for the chemicals of interest.

Where integrated sampling is used, it is recommended that the

sample duration and locations(s) be representative of the

worst-case, realistic, anticipated exposure time and locations.

The resulting average concentration is directly compared to

the OEL to demonstrate conformance to Sections 23.5.1–

23.5.3.

NOTE 113: Tracer gas testing (see SEMI F15 for an

acceptable method) may be used when direct-reading

instrumentation does not have adequate sensitivity, or when

direct-reading technology is not available for the chemicals of

interest. Tracer gas testing should be used where testing

conditions may be hazardous (e.g., system failure simulation

with potential release of hazardous gas to atmosphere). It is

recommended that tracer gas testing be used only when an

accurate rate of chemical emission can be determined. Where

used, it is recommended that the sample location(s) be

representative of the worst-case, realistic exposure location(s).

23.5.4 Chemical emissions outside the enclosure

during a realistic worst-case system failure should be

less than the lower of the following two values: 25% of

the lower explosive limit (LEL), or 25% of the OEL.

23.6 Equipment that uses hazardous gases may require

continuous detection and, if so, should have sample

points mounted in the equipment, or have

recommended sampling points identified in the

equipment installation instructions. Where the gas

supply is part of or controlled by the equipment, the

equipment should be able to accept a signal from an

external monitoring device and shut down the supply of

the gas.

23.7 Appropriate hazard warning labels should be

placed at all chemical enclosure access openings.

24 Ionizing Radiation

24.1 This section covers equipment that produces

ionizing radiation (e.g., X-rays, gamma rays) or uses

radioactive sources.

24.2 Accessible emissions of ionizing radiation should

be designed as low as reasonably achievable. This

criteria can be met by demonstrating conformance to

the provisions in Sections 24.2.1 and 24.2.2 and

Appendix 4.

24.2.1 Accessible levels of ionizing radiation during

normal operations should be less than 2 microsieverts

(0.2 millirem) per hour above background. See also

Table A4-1 of Appendix 4.

24.2.2 Accessible levels of ionizing radiation during

maintenance and service procedures should be less than

10 microsieverts (1 millirem) per hour above

background. See also Table A4-1 of Appendix 4.

24.2.3 Access to radioactive contamination or internal

exposure (e.g., inhalation, ingestion) to radioactive

materials should be minimized. The hazards and

controls for the prevention of personnel contamination

and internal exposures should be detailed in the

operation and maintenance manuals.

NOTE 114: The use of radioactive material is strictly

regulated around the world. Import, export, and transportation

of radioactive materials is also highly regulated. Licenses may

be required to possess, use, and distribute radioactive

materials.

NOTE 115: Many regions require both user and import

licenses, and the timely acquisition of these licenses depends

on the information provided by the equipment supplier.

NOTE 116: Radiation producing machines are also regulated

around the world. Regulations and licensing requirements

may cover activities such as importing, exporting, installing,

servicing and using radiation producing equipment.

24.2.4 The manufacturer should supply, in the user

documentation, a contact phone number and address for

the manufacturer’s radiation safety support personnel.

24.3 Equipment should be designed to minimize access

or exposure to ionizing radiation during normal

operation, maintenance, and service. Potential

exposures should be controlled in the following order of

preference:

24.3.1 Engineering Controls — Engineering controls

(e.g. shielding, interlocks) should be the primary

mechanism to minimize emission of ionizing radiation

or access to ionizing radiation.

24.3.1.1 Radiation shielding for the equipment

facilities connections (e.g., gas and exhaust lines)

should be designed such that removal and replacement

of the shielding during installation is minimized.