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SEMI F39-0699 © SEMI 1999 1 SEMI F39-0699 GUIDELINE FOR CHE MICA L BLENDING SYSTEM S This g u ideline was tec hnically approved by the Global Fa cilities Committee and is the direct respo nsibility of the Nort h America …

SEMI F38-1104 © SEMI 1999, 2004 5

ansion

stem

Differential

Pressure

Diffusion

Gas

Inlet

FM2

FM1

Gas

Inlet

Radioactive

Neutralizer

Radioactive

Neutralizer

Mixin

Chamber

Differential

Pressure

F1, F2 = 10” PTFE Membrane Filter or Equivalent Filter with Sufficient Flow Capacity (LRV  9)

R1 = @ 0 - 100 psig Outlet Regulator

FM1, FM2 = Low Flow ( 0 - 50 slm) Flowmeter

Figure 1

Schematic Diagram of Filter Test System

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SEMI F39-0699 © SEMI 19991

SEMI F39-0699

GUIDELINE FOR CHEMICAL BLENDING SYSTEMS

This guideline 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 December 18, 1998. Initially available on www.semi.org January 1999; to be

published June 1999.

1 Purpose

1.1 This guideline establishes terminology,

classification, performance characterization, and

qualification methods for chemical blending equipment.

2 Scope

2.1 This guideline applies to chemical blending

equipment interfaced with Bulk Chemical Distribution

Systems (BCDS).

3 Limitations

3.1 This guideline does not cover subject matter

concerning chemical distribution capability of some

chemical blending equipment, chemical blending

methodology, or materials of construction used in this

equipment.

4 Referenced Documents

4.1 SEMI F31 — Guide for Bulk Chemical

Distribution Systems

5 Terminology

5.1 accuracy  A quantity describing the deviation of

the mean blend ratio produced by the chemical blending

equipment from the desired constituent ratio.

5.2 assay  A term used to determine the amount of a

chemical constituent in a blend.

5.3 baseline contamination level  The level of

impurity measured in the source fluids, including UPW

and chemical.

5.4 batch  The end quantity of chemical resulting

from the blending of the chemical constituents.

5.5 blending  Combination of two or more

chemicals to create a mixture which contains a desired

ratio of constituents. A dilution process by this

definition is also a blending process. However,

blending is a more general case where UPW is not

always one of the constituents. Therefore, the term

blending will be used in the remainder of the document.

5.6 Central Limit Theorem (CLT)  The CLT is a

probability theorem which allows the approximation of

normality for any distribution. The CLT applied to

chemical blending states that if a sufficient number of

random samples are taken from the distribution of all

chemical produced by chemical blending equipment,

then the average measurement of these samples can be

approximated to follow a normal distribution. A rule of

thumb for the “sufficient number of batches” is thirty or

greater.

5.7 dilution  Combination of a concentrated

chemical and UPW to create a lower concentration of

the aqueous chemical.

5.8 duty cycle  The normal percentage of time that

the chemical blending equipment is operating.

5.9 mixing  Mechanical energy imparted to a

combination of two or more chemical constituents used

to create a homogenous solution.

5.10 on-site blending  Chemical blending

equipment used for blending chemical on location of

the semiconductor manufacturing facility

5.11 precision or repeatability  A quantity

describing the degree of achieving the same ratio of

chemical constituents in the blend over time.

5.12 production rate  The volume of chemical able

to be blended and provided to the BCDS per day.

6 Classification

6.1 Batch Blending  The process of chemical

blending where the chemical constituents are combined

and mixed in a tank before being made available for

use.

6.2 Feed-forward Controlled Blending  Blending

process which uses information (i.e. incoming chemical

assay) of the chemical constituents as the basis for

combining these constituents. Examples of feed-

forward blending processes include, but are not limited

to, those processes that use weight or volume for

control.

6.3 Feedback Controlled Blending  Blending

process which combines constituents based on

measurements of the blended chemical. Examples of

feedback controlled blending process include, but are

not limited to, those processes controlled by

measurements of density, conductivity, and chemical

assay (by titration).

SEMI F39-0699 © SEMI 1999 2

6.4 In-line Blending  The process of chemical

blending where the chemical constituents are combined

in line and are immediately available for use.

7 Performance Characteriza tion

7.1 Blending Repeatability :

7.1.1 Batch Blending

7.1.1.1 Sample Collection: A sample of at least thirty

batches of blended chemical is taken. Assay of this

chemical is measured.

7.1.1.2 Calculations: The mean and standard deviation

of the batches are computed.

7.1.1.3 Reporting: When reporting repeatability, either

of two methods is acceptable. Both methods quote

precision in terms of the chemical assay.

7.1.1.3.1 Repeatability at one concentration = mean ±

3σ (where=σ is in units of concentration)

7.1.1.3.2 Repeatability in range of concentrations:

Individually calculate percent relative standard

deviation at 3σ = (3σ / mean) × 100% for representative

concentrations within the desired range (30 samples for

each concentration, calculate a standard deviation and

mean for each concentration). Repeat largest percent

relative standard deviations at 3σ=and concentration

range examined or report percent relative standard

deviation at 3σ for each individual concentration.

7.1.1.3.3 Multiple Components: If more than one non-

aqueous chemical constituent exists in the blend, the

precision for each must be quoted individually.

7.1.2 In-Line Blending

7.1.2.1 Sample Collection: At least thirty samples of

blended chemical are taken. The time interval between

samples must be at least one hour. Assay of this

chemical is measured.

7.1.2.2 Calculations: The mean and standard deviation

of the samples are computed.

7.1.2.3 Reporting: When reporting repeatability one of

two methods is acceptable. Both methods quote

precision in terms of the chemical assay.

7.1.2.3.1 Repeatability at one concentration = mean ±

3σ (where=σ is in units of concentration)

7.1.2.3.2 Repeatability in range of concentrations:

Individually calculate percent relative standard

deviation at 3σ = (3σ / mean) × 100% for representative

concentrations within the desired range (30 samples for

each concentration, calculate a standard deviation and

mean for each concentration). Repeat largest percent

relative standard deviations at 3σ=and concentration

range examined or report percent relative standard

deviation at 3σ for each individual concentration.

7.1.2.3.3 Multiple Components: If more than one non-

aqueous chemical constituent exists in the blend, the

precision for each must be quoted individually.

7.2 Blending Accuracy

7.2.1 Since calculation of accuracy takes into account

both equipment operational parameters (calibration

frequency and drift) and also changes in chemical input

(feed forward blending), calculation of blend accuracy

will not be standardized. However, by definition, a

reported accuracy can not be less than blend precision.

7.2.2 Reporting of Accuracy

7.2.2.1 Accuracy at one concentration = desired

concentration ± 3σ

7.2.2.2 Accuracy in range of concentrations: Report

range of concentrations where this accuracy applies and

the accuracy in terms of a percentage of the chemical

concentration. Report accuracy with statistical

significance of 3σ.

7.3 Production Rate

7.3.1 All production rates described should reference

the duty cycle, i.e. the percentage of time that the

equipment is operating to achieve the quoted

production rate.

7.3.2 Batch Production Rate = batch volume / time to

produce one batch (hours) × 24 hours × duty cycle

7.3.3 In-line Production Rate = flow rate (volume

/day) of blended chemical × duty cycle

7.4 Purity

7.4.1 Particles  Particle performance should be

expressed in the same manner as BCDS (i.e. < x

particles / ml @ > 0.y µm)

7.4.2 Trace Metals  Metallic purity performance

should be expressed in a similar manner as BCDS.

However, blending systems, by definition, have several

source materials, which could include water. Each

source material contributes to the “baseline

contamination level” (equivalent to drum contamination

level in BCDS). A volumetric combination (based on

the volumetric combination of source materials) of the

contamination levels should be used to construct the

baseline contamination level.

7.4.3 Ionic Contamination / TOC  Should be

expressed in a similar manner as BCDS.

7.5 Uptime

7.5.1 MTBA  Mean Time Between Assists should