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SEMI F58-1000 © SEMI 2000 1 SEMI F58-1000 TEST METHOD FOR DETERMINATION OF MOISTURE DRY-DOWN CHARACTERISTICS OF SURF A CE-M OUNTED AND CONVENTIONAL GAS DISTRIBUTION SYSTE MS BY A TM OSPHERIC PRESSURE IONIZA TION M A SS S…

SEMI F57-0301 © SEMI 2000, 200111

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SEMI F58-1000 © SEMI 20001

SEMI F58-1000

TEST METHOD FOR DETERMINATION OF MOISTURE DRY-DOWN

CHARACTERISTICS OF SURFACE-MOUNTED AND CONVENTIONAL

GAS DISTRIBUTION SYSTEMS BY ATMOSPHERIC PRESSURE

IONIZATION MASS SPECTROMETRY (APIMS)

This test method 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 August 28, 2000. Initially available on SEMI OnLine August 2000; to be published

October 2000.

1 Purpose

1.1 This document describes the p rocedure for

determination of the moisture dry-down characteristics

(quantity of removable moisture) of surface mounted

and conventional gas distribution systems (integrated

gas distribution systems). APIMS is currently the

method of choice for such dynamic tests because it is

the commercially available technique capable of ppt

moisture analysis with the fastest response time. This

test method may provide guidelines for the application

of other techniques with similar detection limits and

response time to APIMS which are not commercially

available at this time.

1.2 The results of this test can be u sed for qualitative

ranking of gas delivery based on the design. It can also

be used by a sufficiently sophisticated user as input for

numerical simulation of distribution system behavior.

2 Scope

2.1 This test method applies to all types of surface

mounted and conventional gas distribution systems

used in semiconductor processing.

2.2 Test Medium — The test proce dure will be carried

out in nitrogen. Other “inert” gases will have different

purging characteristics and may dry a system more

quickly or slowly. Reactive gases may react chemically

with moisture. Considerations relating to corrosion

resistance are outside the scope of the present

document, although the test procedure may prove useful

in corrosion studies. The results will provide a ranking

with respect to moisture contribution arising as a result

of differences in design, which may be applied with due

caution to systems intended for use in other gas

applications.

2.3 Operating Situations — Moist ure contribution

from a gas delivery system may be the result of

contamination arising in its manufacture, or from

subsequent exposure to ambient air or non-dry gas.

Thus, it is necessary to consider two main situations:

2.3.1 The “initial dry-down” situatio n, which is

determined by the moisture content of the components

in the system (as received) with the effects of

manufacturing process and design, surface quality, pre-

treatment and packaging convoluted together.

2.3.2 The “response to upset” situati on, which is

determined by the amount of moisture taken up by the

system and subsequently released in any exposure after

receipt.

2.4 Safety Issues — This standard does not purport to

address safety issues, if any, associated with its use. It

is the responsibility of the users of this standard to

establish appropriate safety and health practices and

determine the applicability of regulatory limitations

prior to use.

3 Limitations

3.1 This test method allows the de termination of

moisture interactions which can be used, for example,

to rank systems in order of decreasing moisture

interaction. Because different degrees of moisture

interaction are permissible in different situations,

selecting the “best” system requires consideration of

how they will be used, either qualitatively or through a

numerical simulation of distribution system behavior.

The results of this test can only be used for qualification

for gas delivery systems based on different designs. It

cannot be used for production purposes and/or

certification/testing.

4 Referenced Standards

NOTE 1: As listed or revised, all documents cited shall be the

latest publications of adopted standards.

4.1 SEMI Standards

SEMI C15 — Test Method for ppm and ppb Humidity

Standards

SEMI F27 — Test Method for Moisture Interaction and

Content of Gas Distribution Systems and Components

by Atmospheric Pressure Ionization Mass Spectrometry

(APIMS)

SEMI F58-1000 © SEMI 2000 2

SEMI F33 — Method for Calibration of Atmospheric

Pressure Ionization Mass Spectrometer (APIMS)

4.2 ASTM Standards

ASTM-F1397-93 — Standard Test Method for

Determination of Moisture Contribution by Gas

Distribution System Components

5 Summary of Test Method

5.1 This test method consists of in itial drydown and

moisture input tests for both surface-mounted and

conventional gas delivery systems.

6 Terminology

6.1 Abbreviations and Acronyms

6.1.1 APIMS — Atmospheric Pressure Ionization

Mass Spectrometry.

6.1.2 EPSS — electropolished stain less steel.

6.1.3 ppm — molar parts per million (µmole/mole).

The same as ppmv.

6.1.4 ppb — molar parts per billion (nmole/mole). The

same as ppbv.

6.1.5 ppt — molar parts per trillion (p mole/mole). The

same as pptv.

6.1.6 slpm — standard liters per minute, the gas

volumetric flow rate measured in liters per minute at

0°C and 1 atm.

6.2 Definitions

6.2.1 baseline — an instrument response under steady

state conditions.

6.2.2 glove box — an enclosure that contains a

controlled atmosphere, usually inert.

6.2.3 induction time — the elapsed time between when

humidified gas is introduced to the test system and

when moisture is detected at the moisture analyzer. For

a test system which is perfectly transparent to moisture,

the induction time is equal to the residence time of the

gas in the system.

6.2.4 peak height — the maximum moisture

concentration recorded when a moisture input of pre-

defined length and concentration is introduced to a test

system.

6.2.5 response time — the time required for the test

system to reach steady state after a change in

concentration.

1 Available from American Society for Testing and Materials, 100

Barr Harbor Dr, West Conshohocken, PA 19428. Fax: 1-610-832-

9555. World Wide Web: http://www.astm.org.

6.2.6 test system — the gas delivery system under test

7 Required Equipment

7.1 APIMS — The APIMS used fo r moisture detection

can be of any type. Calibration of the APIMS shall be

performed as per SEMI F33, one at the beginning and

one at the end of the series. These calibrations shall

both be made under the same analytical conditions

(flow, pressures, plate voltages, etc.) as the tests and the

results shall be within 5% of each other. Provided this

condition is met, the interval between calibrations may

be left to the discretion of the operator; however, it is

suggested that calibration should be carried out

whenever the equipment is moved and/or every two

weeks of operation.

7.2 Dry Gas and Moisture Generator — A source of

extremely dry nitrogen (less than 200 ppt moisture) and

a moisture generator capable of delivering up to 13

slpm nitrogen doped with 200 ppb moisture is required.

This generator may be the same as used to calibrate the

APIMS. The output of the generator shall be verified

according to SEMI C15.

7.2.1 Most ultra-high purity gas panels are currently

fitted with metal gasket type connectors. The same type

of connector should, therefore, be incorporated into the

test bench for connection to the test system.

7.3 Test Blank — Any series of tes ts shall include the

results of testing a blank. The blank shall be the shortest

convenient length (no more than 1 m) of 1/4" EPSS tu-

bing with suitable fittings and/or adapters at either end

to enable it to be inserted in place of the test system.

7.4 Moisture Pulse Generator — A valve arrangement

capable of switching instantaneously between dry and

humidified nitrogen is also required. An example of

such a design is shown in Figure 1. In this design, flow

is maintained in both the humidified and dry gas lines at

all times. By simultaneously switching valves V

and

, or V

and V

, either humidified or dry gas is

directed through the test system while the other gas

stream is directed to vent. Note that there is a bypass

loop so that flow can be maintained to the APIMS when

the test system is removed. In this design, all gas lines,

but especially those lines between V

and V

and

between V

and V

, should be as short as possible and

constructed of EPSS tubing of high quality.

Maintaining gas lines at a constant temperature between

50 and 80ºC wherever possible is also recommended.

7.4.1 The bypass loop will contain a stagnant volume

of gas during testing. To avoid exposing the APIMS to

a large moisture upset whenever it is fed with the gas

contained in the bypass loop, the loop should be

thoroughly baked out (at ≥ 200°C) and protected from

atmospheric contamination thereafter. Valve V

should