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SEMI F31-0698 © SEMI 1998 4 7.2 Sour ce — The source of all flu i d s for incoming Bulk Chemical Distribution Systems is a container suitable for holding reactiv e che micals in a size 55 gallo ns or great er, which ma y…

SEMI F31-0698 © SEMI 19983

incorporates all of the physical activities and testing

parameters and establishes check points for approvals at

each stage.

6.3 Acceptance Tests — Acceptance tests are

conducted on each subsystem or system produced. They

are the basis for acceptance or rejection by the

purchaser.

6.3.1 Acceptance testing may include performance

demonstrations, demonstration of reliability criteria,

and achievement of purity standards. Safety

considerations are addressed elsewhere.

6.4 Qualification Testing — Qualification testing is

performed on the liquid chemicals being transported

through each chemical piping subsystem.

6.4.1 Qualification testing may include tests for trace

metals, anions, particles, and total organic carbon.

Assay analysis is recommended for blending or dilution

operations.

6.5 Chemical Specifications — Particulate BCD

Systems are specified as to the level of impurities at the

point of use as compared to the quality of the incoming

chemical. Impurities in the chemical are generally

specified in terms of particles per ml; metallic

impurities are specified for each element and for total

adders; and organic impurities are specified for total

added.

7 Basic Design Elements

7.1 General — Each Bulk Chemical Distribution

System contains certain basic components and a variety

of design options to meet particular customer and

facility needs. A simple example system is shown in

Figure 1.

Figure 1

Schematic of Basic Bulk Chemical Distribution System

SEMI F31-0698 © SEMI 1998 4

7.2 Source — The source of all fluids for incoming

Bulk Chemical Distribution Systems is a container

suitable for holding reactive chemicals in a size 55

gallons or greater, which may include drums, totes,

vessels, or ISO containers.

7.3 Fluid Transfer — Fluids in the Bulk Chemical

Distribution Systems are transported through pipes

using either a pumping system, a pressure differential

system, or some combination of the two types of basic

systems. All fluids are transported in secondary

containment piping systems for safety reasons.

7.4 Distribution — The transfer is made from the

source by means of certain types of mechanisms,

usually through one or more valve manifold boxes, that

direct the fluid to a point of use, to subordinate levels of

distribution, and/or to a day tank.

7.5 Control Systems — Manual and/or automated

mechanical, pneumatic, hydraulic, optical, and

electronic systems control the movement of the liquids.

This includes the volume, flow rate, pressure, start-up,

and shut-off.

8 Optional Design Features

8.1 Polishing — BCD Systems ma y be designed with

the possibility of chemical recirculation (1) from the

incoming source and back, to polish the incoming

chemical; (2) from the day tank and back for further

polishing or timed recirculation if activity is limited;

and (3) fabwide in continuous recirculation.

8.2 Filtration — Chemicals in the system may be

recirculated through filters placed on-line in the system.

The relevant design issues include types of filters,

efficiency, useful lifetime, qualification, filter bleed,

removal, and replacement.

8.3 Day Tank — The vessel that generally stores a

limited amount of chemical volume generally

equivalent to that used in about one day of operation.

This holding vessel usually stores prefiltered chemical

before it is transferred to the manufacturing process.

8.4 Blending — Certain chemicals in distribution are

blended together for use in the semiconductor

manufacturing process. For example, Buffered Oxide

Etchant is a blend of Hydrofluoric Acid and

Ammonium Fluoride and may be sourced as two

separate chemicals and blended together in the correct

concentrations within the BCD Systems.

8.5 Dilution — Certain chemicals used in the

semiconductor manufacturing process require various

concentrations, depending on the process used at a

particular point in the system. For example, 49%

Hydrofluoric Acid is brought in as the source chemical

and then mixed with DIW in a blend unit to achieve

various concentrations of 10:1, 100:1, etc., depending

on the requirements of the manufacturing process.

8.6 Automated Control Systems — Electronic systems

may be programmed to control system parameters such

as volume, pressure, fill rate, flow, drain times,

maintenance diagnostics, purge cycles, recirculation,

and bypass.

8.7 Sampling Ports — Sampling ports may be

incorporated into the system to facilitate chemical

sampling for qualification and monitoring programs.

8.8 On-Site Chemical Generation — Liquid

chemicals, such as Ammonium Hydroxide, may be

generated on-site at the required concentration from a

clean Ammonia gas source and DIW to the required

concentration. Generally, this activity is done in a

location apart from the dispense room. The resulting

chemical is used as a source for the distribution system.

8.9 Reprocessing — Integrated with the general

chemical distribution system may be a chemical

reprocessing unit which purifies or recycles a chemical

such as sulfuric acid, isopropanol, or hydrofluoric acid.

Such a system enables the chemical to reenter the

system as a clean source of material for manufacturing

processing.

8.10 Stabilized Filtration — Some systems include a

design feature that provides for the continuous flow of

chemical over filters to minimize shocking and

pulsating of the filters.

8.11 Surge Suppression — Some systems include a

device or in-line chamber that minimizes hydraulic

forces caused by a pump. This option may also be

referred to as pulsation dampener.

9 Monitoring and Maintenance of Systems

9.1 General Considerations — Bulk Chemical

Distribution Systems may require a significant level of

maintenance and monitoring to determine that

specifications and performance are initially and

continually met.

9.2 Functional Management System — The entire

dispense system can be monitored by means of

PC/PLC/ or any hybrid system, recording events as they

occur and alerting operators as necessary to take

corrective action. Monitoring systems may include a

variety of operational parameters:

9.2.1 on-line real-time monitoring of all chemical

dispense units

9.2.2 status of components and subsystems

9.2.3 events logging

9.2.4 data management

9.2.5 reliability parameters, including lead detection

9.2.6 chemical usage

9.2.7 display of dispense systems

9.2.8 communication gateway to the factory alarm

system

9.2.9 on-line documentation

9.2.10 predictive maintenance planning

9.2.11 chemical interruptions to the fab by location,

indicating location of fault.

9.3 Maintenance — Maintenance of the BCD Systems

includes routine and preventative maintenance of

pumps, filters, valves, and other components.

9.4 Monitoring Programs — Each BCD System

should be monitored to determine if liquid chemicals

delivered to the tools for use in the manufacturing

process continually meet specifications and are within

initial and ongoing established process control limits.

9.4.1 Monitoring programs may include periodic

testing of the liquid chemicals to determine levels of

particles, trace metals assay, and other parameters of

interest. Certain tests may be done continuously on-line

(e.g., particles), and other analytical tests are performed

periodically from samples taken at various points in the

system.

NOTICE: These standards do not purport to address

safety issues, if any, associated with their use. It is the

responsibility of the user of these standards to establish

appropriate safety and health practices and determine

the applicability of regulatory limitations prior to use.

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 manufacturer’s

instructions, product labels, product data sheets, and

other relevant literature respecting any materials

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, are entirely their own responsibility.

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