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SEMI E49.8-1103 © SEMI 1996, 2003 2 ASTM F 1397 — Test Method for Determination of Moisture Con tribution f o r Gas Distri bution System Compone nts NOTICE: Unless ot herwise i ndicated, all docum ents cited shall be the…

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SEMI E49.8-1103 © SEMI 1996, 2003 1
SEMI E49.8-1103
GUIDE FOR HIGH PURITY AND ULTRAHIGH PURITY GAS
DISTRIBUTION SYSTEMS IN SEMICONDUCTOR MANUFACTURING
EQUIPMENT
This guide was technically approved by the Global Gases Committee and is the direct responsibility of the
North American Gases Committee. Current edition approved by the North American Regional Standards
Committee on September 3, 2003. Initially available at www.semi.org October 2003; to be published
November 2003. Originally published in 1996; previously published February 1998.
NOTICE: This document was completely rewritten in
2003.
1 Purpose
1.1 This document specifies guidelines for high purity
(HP) and ultrahigh purity (UHP) gas distribution
systems in semiconductor manufacturing equipment.
2 Scope
2.1 This guide applies to gas distribution systems
consisting of stainless steel components designed to
supply the following types of gases to the process
chamber:
2.1.1 Specialty Gases — Corrosive, flammable,
pyrophoric, oxidizer, toxic, inert, and mixtures.
2.1.2 Bulk Gases — Nitrogen, oxygen, argon,
hydrogen, and helium.
2.2 Typical processes include diffusion, anneal, plasma
etch, chemical vapor deposition, physical vapor
deposition, and ash.
NOTICE: 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 health practices and determine the
applicability or regulatory limitations prior to use.
3 Referenced Standards
3.1 SEMI Standards
SEMI E49 — Guide for Standard Performance,
Practices, and Sub-Assembly for High Purity Piping
Systems and Final Assembly for Semiconductor
Manufacturing Equipment
SEMI E49.6 — Guide for Subsystem Assembly and
Testing Procedures - Stainless Steel Systems
SEMI F1 — Specification for Leak Integrity of High-
Purity Gas Piping Systems and Components
SEMI F17 — Specification for High Purity Quality
Electroplished 316L Stainless Steel Tubing, Component
Tube Stubs, and Fittings Made from Tubing
SEMI F19 — Specification for the Finish of the Wetted
Surfaces of Electropolished 316L Stainless Steel
Components
SEMI F20 — Specification for 316L Stainless Steel
Bar, Extruded Shapes, Plate, and Investment Castings
for Components Used in High Purity Semiconductor
Manufacturing Applications
SEMI F37 — Method for Determination of Surface
Roughness Parameters for Gas Distribution
Components
SEMI F58 — Test Method for Determination of
Moisture Dry-Down Characteristics of Surface-
Mounted and Conventional Gas Distribution Systems
by Atmospheric Pressure Ionization Mass Spectroscopy
(APIMS)
SEMI F60 — Test Method for ESCA Evaluation of
Surface Composition of Wetted Surfaces of Passivated
316L Stainless Steel Components
SEMI F70 — Test Method for Determination of
Particle Contribution of Gas Delivery System
SEMI F73 — Test Method for Scanning Electron
Microscopy (SEM) Evaluation of Wetted Surface
Condition of Stainless Steel Components
SEMI F78 — Practice for Gas Tungsten Arc (GTA)
Welding of Fluid Distribution Systems in
Semiconductor Manufacturing Applications
SEMI F81 — Specification for Visual Inspection and
Acceptance of Gas Tungsten Arc (GTA) Welds in Fluid
Distribution Systems in Semiconductor Manufacturing
Applications
SEMI S2 — Environmental, Health, and Safety
Guideline for Semiconductor Manufacturing Equipment
3.2 ASTM Document
1
1 American Society for Testing and Materials, 100 Barr Harbor
Drive, West Conshohocken, Pennsylvania 19428-2959, USA.
Telephone: 610.832.9585, Fax: 610.832.9555, Website:
www.astm.org
SEMI E49.8-1103 © SEMI 1996, 2003 2
ASTM F 1397 — Test Method for Determination of
Moisture Contribution for Gas Distribution System
Components
NOTICE: Unless otherwise indicated, all documents
cited shall be the latest published versions.
4 Terminology
4.1 See Section 4 in SEMI E49.
5 Design Guidelines
5.1 All weld joints should be automatically orbital butt-
welded in accordance with SEMI F78 and SEMI F81.
5.2 Directional changes in the process flow path should
be minimized. Required directional changes should be
accomplished by butt-weld elbows or block
components. Tube bends may be used on tubing ≤ ½
inch O.D. and should be formed using manual or CNC
bending equipment. CNC tube bending is preferred to
manual tube bending because during manual bending
uniform deformation of the tubing is more difficult to
control and reproducibility of bend geometries is much
less than that achieved by bending using CNC methods.
An internal mandrel must not be used during bending as
it can contaminate and/or damage the internal surface.
Recommended minimum bend radii are the following:
• For inert gas lines, a bend radius (as measured
from the tube centerline) as small as 2 × tube
diameter may be used for 90 degree directional
changes.
• For reactive gas lines, a bend radius (as measured
from the tube centerline) as small as 5x tube
diameter may be used for 90 degree directional
changes; however, it is recommended that
corrosion testing be performed to determine if bent
tubing is suitable in each particular reactive gas
application.
5.3 Components that may need to be removed or
replaced should be installed with metal seal fittings.
5.4 Dead volumes should be minimized in the process
gas stream. The system internal volume should be
minimized.
5.5 All potentially pyrophoric or reactive gases should
have upstream and downstream purge/vacuum
capability for MFC maintenance. To speed the purge
process and allow the system to be evacuated even if
the MFC is clogged, the design should also have the
ability to provide vacuum both upstream and
downstream of the MFC. A gas is defined to be reactive
if it has a Hazardous Production Material (HPM) rating
of 3 or 4 per SEMI S2.
5.6 Inert gases do not need an input for an independent
purge gas. Inert gases can act as their own purge gas
and only need to purge in the intended direction of
flow. Inert gas lines do not need upstream vacuum
capability or downstream purge capability. To speed
the purge process, the design should have the ability to
provide vacuum downstream of the MFC.
5.7 For low pressure equipment, the vacuum path from
the MFC manifold to the pump should bypass the
process chamber during purging or maintenance and
should connect directly to the foreline.
5.8 For atmospheric pressure equipment, a vacuum
Venturi to vent/exhaust method should be required for
reactive gases.
5.9 Design should include a means of cycle purging
upstream and downstream of removable components or
subassemblies for reactive gases and should include a
means of flow-through purging for all removable
components.
5.10 Backflow/back pressure protection should be
included for all purge gases in the system.
5.11 All incoming gas lines should have filters.
5.12 Any additional filters, located at point of use
before a process chamber or loadlock, should have a
means of isolation from atmosphere.
5.13 Test/sample ports should be located on each
process chamber supply line or the designated
purge/vent line.
5.14 For processes requiring additional purification of
process gases, purifiers should be included in the gas
system and located upstream of MFC’s. The system
should include a means of purging and removing
purifiers in a safe manner.
6 Materials Guidelines
6.1 Stainless Steel
6.1.1 Components should be fabricated from
electropolished 316L stainless steel per SEMI F17, or
SEMI F20.
6.2 Other Materials
6.2.1 Materials for valve seals, diaphragms, gaskets,
and O-rings should be chemically compatible with the
process gas. All materials exposed to process gas
should be reported.
SEMI E49.8-1103 © SEMI 1996, 2003 3
Table 1 Summary of Requirements for High Purity and Ultrahigh Purity Components and SubAssemblies
Description High
Purity
Value
Ultrahigh
Purity
Value
Units
Internal Surface Chemistry (ESCA) — Test method per SEMI F60
Total chromium to iron ratio including both reduced and oxidized states
refer to
SEMI F19
refer to
SEMI F19
value
Internal Surface Defects (SEM) — Test procedures per SEMI F73
Photos per test method
Counts per photo
refer to
SEMI F19
refer to
SEMI F19
value
value
Internal Surface Roughness — Test procedure per SEMI F37
Average surface roughness (Ra)
Maximum surface roughness from an individual measurement
refer to
SEMI F19
refer to
SEMI F19
µm (µin.)
µm (µin.)
Static Flow Particulate Contribution (valves, regulators, flow controllers) —
Test procedures per SEMI F70
Particles ≥ 0.1 µm
Particles ≥ 0.02 µm
≤ 0.71 (≤ 20)
≤ 2.6 (≤ 75)
≤ 0.18 (≤ 5)
≤ 0.71 (≤ 20)
ptc/L (ptc/ft
3
)
ptc/L (ptc/ft
3
)
Internal Absorbed Moisture – Test procedures per ASTM F 1397 or SEMI F58
For low surface area component (valve, regulator), time to recover to
baseline from a 2 ppm spike (ASTM F 1397) or 200 ppb spike
(SEMI F58)
For high surface area component (filters, tubing), time to recover to
baseline from a 2 ppm spike (ASTM F 1397) or 200 ppb spike
(SEMI F58)
≤ 4
≤ 6
≤ 1
≤ 4
hour
hour
Cycle Life (valves, regulators, and MFC’s) — sample at least 4 and no more than
10 components using a 90% confidence interval and exponential hazard
function:
Manual valves – MTTF of ≥ 25 K cycles
Pneumatic valves, regulators, and MFC’s – MTTF of ≥ 500 K cycles
Following cycling, components must meet
the particulate contribution requirements in
this table and the leak rate requirements in
Sections 6.2, 7.2 and 7.3.
7 Component Guidelines
7.1 Components in subassemblies should comply with
the surface requirements listed in SEMI F19, and with
additional requirements listed in Table 1.
7.2 All components should meet the inboard/outboard
leak rate requirements of SEMI F1.
7.3 Valves should be springless, packless diaphragm
type with all metal bonnet seals. All valves should
meet the leak across the seat requirements of SEMI F1.
7.4 Valve flow coefficients (C
v
) should be selected
based on gas flow requirements and gas characteristics.
The C
v
should be determined using SEMI F32.
7.5 Regulators should be sized based on gas flow
requirements and gas characteristics by examination of
a droop curve that shows regulator pressure drop as a
function of flow at the specific inlet pressure and set
outlet pressure conditions.
7.6 Filters in the final line just upstream of the chamber
that are intended to protect the chamber from upstream
particulate contamination should be 9-LOG retention
for particles greater than or equal to 0.003 µm and
should be tested per SEMI F38. The filters should be
made of PTFE, stainless steel, nickel or ceramic media.
7.7 Pressure transducers should minimize the dead
space below the diaphragm.
8 Subsystem Assembly Guidelines
8.1 See SEMI E49.6 for recommended stainless steel
system assembly procedures.