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SEMI F46-0999 © SEMI 1999 2 process plum bing. Clear PVC pipe is typi cally, but not exclusively , used for the secondary containm e nt. SPC scheme  an alternate quality verification scheme that woul d invol ve rand om …

SEMI F46-0999 © SEMI 19991

SEMI F46-0999

GUIDE FOR ON-SITE CHEMICAL GENERATION (OSCG) SYSTEMS

This guide was technically approved by the Global Facilities Committee and is the direct responsibility of the

North American Facilities Committee. Current edition approved by the North American Regional Standards

Committee on April 15, 1999. Initially available on www.semi.org August 1999; to be published September

1999.

1 Purpose

1.1 This guide establishes the minimum System and

Overall Implementation requirements for requirement

of On-Site Chemical Generation (OSCG) used in

semiconductor manufacturing. It is also intended to

establish a common basis for developing detailed

guides in subsequent documents concerning design,

performance, and certification of OSCG systems.

2 Scope

2.1 This guide applies to the OSCG system design

used for the generation of chemicals, particularly ultra

high purity, used in the silicon wafer, integrated circuit,

and/or substrate manufacturing processes. These will

include, but are not limited to, various concentrations of

OH, HCl, HF, and NH

F aqueous solutions.

2.2 This standard does not purport to address all of the

safety issues associated with its use. It is the

responsibility of the users of this standard to establish

appropriate safety and health practices and determine

the applicablity of regulatory limitations prior to use.

3 Limitations

3.1 This guide is not intended to cover all chemicals

used in these processes but only to those that can be

generated, on-site, by means of reacting ultra-pure

process gas with the appropriate liquid solution.

3.2 This guide is not intended to be applicable to

“Point-of Use” generated process solutions.

3.3 This guide excludes construction protocols for

OSCG such as clean manufacturing, integrity of

fabrication, and prequalification of materials.

3.4 This guide does not intend to cover all the

important safety considerations which relate to the

OSCG systems, feed gas, equipment, or installations.

4 Referenced Standards

4.1 SEMI Standard

SEMI S2  Safety Guidelines for Semiconductor

Manufacturing Equipment

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

latest publications of adopted standards.

5 Terminology

blending (or dilution)  the combination of two or

more chemicals (one of which may be DI water) to

create the desired solution mixture.

clean sampling  a specifically designed scheme to

allow for the taking of chemical samples, avoiding any

contamination from the operator or background

environment of the area.

day tank  a chemical storage vessel, of appropriate

material(s), used to store a volume of product chemical

that could be consumed in one or more days.

DI water  high purity 18 megohm water

OSCG system  the stand-alone unit that produces (or

uses) a high purity gas and reacts it with water (or the

appropriate aqueous solution) to produce the desired

ultra pure chemical solution. This unit is intended for

use on the manufacturing site and in a centralized

scheme to support all or a portion of the site’s chemical

requirement(s).

overall implementation  this term is used to refer to

the entire scope for an OSCG installation, including the

Gas Storage/Supply system, the OSCG system,

chemical storage tanks, chemical plumbing, and

interface with the chemical distribution system. Gas

supplies are covered in related guides.

process plumbing  tubing or piping whose surface is

directly in contact with the chemical. Typically

constructed from high purity perfluorinated materials or

other high purity polymers.

product chemical  the name given to the actual

chemical produced on site by the OSCG system.

pump  a mechanical or pneumatically operated

device used to create hydraulic force for chemical

transfer.

QC tank  storage tank for the staging of chemical to

be quality verified prior to release to the Product

storage tank. This optional quality verification scheme

allows for 100% chemical verification.

secondary containment  pipe or tubing that contains

the process plumbing intended to provide a second level

of containment in the event of failure of the primary

SEMI F46-0999 © SEMI 1999 2

process plumbing. Clear PVC pipe is typically, but not

exclusively, used for the secondary containment.

SPC scheme  an alternate quality verification scheme

that would involve random sampling and analysis of

product chemical. This scheme relies on Statistical

Process Control to monitor and ensure product

chemical quality.

6 General Requirements

6.1 Materials



Only specific materials are permitted

to be in direct contact with the gas(es) and/or chemi-

cal(s) used or produced in the OSCG system. This is

driven by both chemical compatibility to ensure long

term system survivability and product chemical purity.

6.1.1 Cabinet Construction  Polypropylene or other

suitable materials house chemical handling components

(pumps, valves, filters, etc). All cabinets must be

designed to be leak tight and provide a minimum of

110% liquid containment within the cabinet.

6.1.2 Process Plumbing and Components 

Polymeric materials are recommended for all plumbing

and components that will be in direct, routine contact

with the chemical solutions.

6.1.3 Feed Gas Plumbing and Components  Feed

Gas, prior to purification (when gas purification is part

of the OSCG system), will be plumbed using

compatible materials such as stainless steel.

6.1.4 Storage Tanks  Liner materials used in

chemical storage tanks that will be in direct contact

with the chemical solution will be chosen to maintain

chemical purity.

6.2 Overall System Installation

6.2.1 All OSCG systems, support equipment, process

plumbing, and tanks will be installed and facilitated

according to vendor guide which ensures mechanical

integrity, leak integrity, minimal contamination, and

overall proper operation.

6.2.2 All OSCG implementations will require the

following basic components: Feed Gas Storage and

Delivery Subsystem, the OSCG system(s), some type of

Quality Control Scheme with “Clean Sampling”

provisions, Product Chemical Storage with a suitable

volume of Product storage, and, optionally, a Back-up

Chemical scheme.

6.2.3 Prior to any introduction of chemical to any

system or subsystem, a complete water test is perf-

ormed to verify leak integrity. This process will also be

used to provide the initial clean-up of all systems,

tanks, and process plumbing.

6.2.4 The protocol for the installation and start-up of

all systems and subsystems follows a predefined

procedure and timeline which incorporates all of the

physical activities, testing parameters, and check points

for approval at each stage.

6.2.5 Cleanroom environment is not necessary.

6.3 Initial System Qualification



T he following

general procedure will be required for the initial

mechanical and chemical qualification of the OSCG

installation.

6.3.1 Electro-mechanical check-out

6.3.2 Initial chemical charge

6.3.3 Initial processing to fill and purge all systems,

plumbing, and tanks with chemical.

6.3.4 Initial sampling to verify purity and assay.

6.3.5 Continuous processing to prove purity and

capacity through a specific number of samples.

6.3.6 Continuous processing to establish overall

system reliability.

7 Basic Design Specificatio ns

7.1 General  Each OSCG installation contains

certain basic components and a variety of design

options to meet a specific customer’s needs. This

section describes the basic installation requirements.

7.2 Feed Gas Storage  All OSCG implementation

will require an appropriately sized Feed Gas storage

vessel.

7.2.1 The Feed Gas Storage vessel should be of

sufficient volume per customer, vendor, and logistical

considerations.

7.2.2 The gas delivery system must be designed to

deliver sufficient gas flowrates at the correct pressure to

the OSCG system.

7.2.3 The appropriate containment and controls are

required to ensure safe and reliable operation.

7.3 Gas Supply Plumbing  Gas supply plumbing

will be required to bring Feed gas from the storage

vessel to the OSCG system.

7.3.1 Materials used for the gas supply plumbing will

be chosen based on compatibility with the specific feed

gas.

7.3.2 Supply plumbing size will be c hosen based on

the flow requirements and delivery distance to ensure

adequate supply volume and pressure at the OSCG

system.

7.3.3 Secondary containment may be required based

on the Feed gas, delivery plumbing routing, and local

SEMI F46-0999 © SEMI 19993

and/or company codes.

7.3.4 An appropriate component design must be used

for the gas/liquid interface(s).

7.4 The OSCG System  The appropriate OSCG

system will be defined based on overall capacity

requirements.

7.4.1 The OSCG system can provide feed gas

purification and chemical generation within a stand

alone packaged unit or use externally purified feed

gases. Optional Feed gas purification may also be

provided in this package.

7.4.2 The OSCG system will have a dedicated control

system to control all process parameters and monitor all

system safety interlocks including external safety

systems.

7.4.3 The OSCG will provide pressurized chemical to

the Product Quality verification subsystem.

7.5 Product Quality Verification  All OSCG

installation will include some type of Product sampling

and quality verification scheme.

7.5.1 The standard quality verification scheme will

provide for an in-line, “Clean Sample” station to allow

for random samples to be taken for analysis.

7.5.2 A SPC quality assurance scheme can be utilized

to track and record product chemical purity and assay

guides. Readings are plotted using X-bar/R format and

reacted to based on standard SPC rules.

7.5.3 In this scheme product chemical is transferred to

the Product storage tank directly from the OSCG

system, through the sampling subsystem or directly to

chemical delivery systems.

7.6 Product Storage  All OSCG implementation

will include a Product chemical storage scheme to

ensure chemical availability to the customer.

7.6.1 Product storage is achieved, typically, by

including an appropriately sized storage tank. This tank

becomes the source to the chemical distribution system.

7.6.2 Product storage volume is defined to provide

suitable inventory of product chemical storage. This

will provide chemical available to the distribution

system during periods of both scheduled and

unscheduled maintenance.

7.6.3 Additionally, a back-up supply of prequalified

chemical may be available to transfer into the Product

tank, if required.

7.7 Central Monitoring System  A central CPU

based monitoring system is required for multiple

purposes in the overall implementation.

7.7.1 The central CPU will communicate with all

subsystems and tanks to share information, as required,

to ensure total system operations.

7.7.2 The central CPU also provides data logging and

database features to track and log product quality and

system failure data as required.

7.7.3 The central CPU can also provide a remote

monitoring feature and interface with the customer’s

facility tracking system (if desired).

8 Optional Configurations and Support

Systems

8.1 Feed Gas Supply  Some customers may already

have an existing source of an appropriate Feed gas for

the OSCG system. Implementation schemes can be

configured to utilize this existing gas storage and

supply system. The existing system will need to meet

the vendors guides for gas purity and line pressures.

8.2 Product Storage and Staging Tanks  Some

customers may already have tanks that can be used for

Product Storage and/or staging applications.

Implementation schemes can be configured to utilize

these existing storage tanks. The existing tanks must

meet vendors guides for materials, inlets/outlets, and

volume. Level sensor data will be provided to the

central CPU system.

8.3 Multiple OSCG Systems  Depending on capacity

requirements, OSCG installations can be configured to

have multiple Generator systems in parallel. All

product outputs should have the capability to be

sampled individually before combining into a common

product stream for storage.

8.4 Support Systems  Various support systems and

options can be provided to support the overall

implementation scheme.

8.4.1 Stand-alone, water-cooled Chiller(s) may be

required, if the house chilled water is not available.

8.4.2 Redundant pump options should be available in

any pumping system to allow for either manual switch

over or automatic back-up.

8.4.3 Transfer pumping systems or transfer options

should be available for the transfer of chemical from or

to remote storage tanks.

8.5 Chemical Distribution  Chemical distribution

systems may or may not be in existence at specific

customer sites. The distribution of chemical from the

product storage to use points will be important to

maintain chemical purity. These distribution systems

should be available as a directly supplied option or

offered through a sub-contracted supplier.