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SEMI E49.8-1103 © SEMI 1996, 2003 3 Table 1 Summary of Requirements for High Purity and Ultrahigh Purity Components and SubA ssemblies Description High Purity Value Ultrahigh Purity Value Units Internal Surface Chemistry…

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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.
SEMI E49.8-1103 © SEMI 1996, 2003 4
NOTICE: 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.
Copyright by SEMI® (Semiconductor Equipment and Materials
International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o
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