SEMI E49.6-95 © SEMI 19951

SEMI E49.6-95GUIDE FOR SUBSYSTEM ASSEMBLY AND TESTING PROCEDURES -STAINLESS STEEL SYSTEMS1 PurposeThe objective of this document is to establish standardguidelines for cleanroom activities specific to themanufacturing, assembly, testing, and integration ofmaterials and components used in stainless steelsemiconductor process equipment.

2 ScopeThis standard has been developed as a guide for theassembly and testing of high purity and ultrahigh puritygas and solvent subsystems.

3 Referenced DocumentsNote: Refer to the latest version of the following documentsfor general cleanroom protocol.

3.1 Federal Standard (FED-STD)1

Federal Standard Cleanroom and Work StationRequirements, Controlled Environment

3.2 Institute of Environmental Sciences (IES)2 IES-RP-CC-001 — Recommended Practices for HEPAFilters

IES-RP-CC-002 — Recommended Practices forLaminar Flow Clean Air Devices

IES-RP-CC-003 — Recommended Practices forGarments Required in Cleanrooms and ControlledEnvironmental Areas

IES-RP-CC-006 — Recommended Practices forTesting Cleanrooms

4 TerminologySee Section 4 of SEMI E49.

5 Facility Guidelines5.1 Gowning Area Class 10,000/1 ,000 (HP/UHP) —All personnel working in cleanrooms should wear paperbooties prior to entering the gowning area. Personnelshould wear polyester gowns, hood, and boots, pure

1 Available from General Service Administration, Federal SupplyService Bureau, Specification Section, Suite 8167, 470 East L’EnfantPlace SW, Washington, D.C. 20407.

2 Available from Institute of Environmental Sciences, 940 E.Northwest Hwy., Mount Prospect, IL 60056.

latex gloves (no talc), and safety glasses before enteringclean areas.

5.2 Materials Staging Area Class 10,000/1,000(HP/UHP) — Materials used in the cleanroom shouldhave the outer bag removed and the inner bag wipeddown with cleanroom wipes saturated with a 50/50IPA/DI mix in the materials staging area prior to entryinto the cleanroom.

5.3 Cutting Area Class 10,000 or Better — Cuttingarea should be a Class 1,000 area while in normal (atrest) operation. Work areas should maintain a Class1,000 average at all times.

5.4 Welding and Cleaning Area Class 1,000/100(HP/UHP) — Welding and cleaning area — ultrasonictanks, DI rinse stations, and dry-down stations —should be Class 1,000 or 100, depending on purityclassification. After final cleaning operation, thereshould be a Class 100 station for final bagging ofcleaned parts prior to their entry into the cleanroom.

5.5 Assembly, Final Integration, and Final Test Class100/10 (HP/UHP) — All areas used for gas/liquidsystem assembly, integration, and test should be Class100/10 under all working conditions. This area shouldbe segregated by hard or soft walls from all otherfabrication areas.

5.6 Common Plenums — Adjoining clean areas ofvarying classifications should be separated with floor-to-ceiling hard or soft walls, have separate return airgrilles, and be positively pressurized to a minimum of1.3 mm (0.05 in.) H20 (W.C.) over the lower adjacentclass clean area when otherwise common by access orpass-through.

6 Utility System Guidelines6.1 Nitrogen for Drying after Clea ning (Both HP andUHP Classes)

• Filtration — 0.01 µm rated

• Oxygen Content — < 1.5 ppm

• Moisture Content — < 1.0 ppm

• Hydrocarbon Content — < 2.0 ppm

6.2 Purge Gases — Argon or nitro gen for purging gassystems during assembly and for testing, usingcryogenic source and 0.01 µm filtered. The followingpurity levels should be as certified by the gas supplier.

SEMI E49.6-95 © SEMI 1995 2

HP UHP

Oxygen Content < 40 ppb < 10 ppbMoisture Content < 20 ppb < 10 ppbTotal Hydrocarbon Content < 40 ppb < 20 ppbParticles < 0.1 particles per ft3 ≥ 0.1 µm

and 0 > 0.2 µm (both classes)Purified at POC Optional Required

6.3 Weld Gases — Welding argon (minimumspecification, purifiers and 0.01 µm rated filter),recommended for ID/OD purge for both HP and UHPsystems):

• Oxygen Content — < 50 ppb

• CO Content — < 50 ppb

• CO2 Content — < 50 ppb

• THC as Content — < 50 ppb

• Moisture Content — < 50 ppb

• These contaminant levels should be as measured atthe POC to the parts to be welded.

6.4 DI Water - HP/UHP Classes

• Resistivity — ≥ 18 mega ohm-cm @ 25°c (77°F)

• TOC — < 20 ppb

• Silica — < 5 ppb

• Particles — < 1 particle/millimeter @ ≥ 0.1 µm

• Bacteria — < 10 colonies/100 millimeter

• Hot DI Temperature — 80°C (176°F), minimum

7 Materials Procedures7.1 Procedures for Incoming Materials andComponents (Component Suppliers)

7.1.1 Identification Guidelines

7.1.1.1 Every deliverable item should have somescheme of positive and permanent identification, so thattraceability is provided from the steel melt source to thefinal metal finishing and packaging through siteinstallation.

7.1.1.2 This identification should providenondestructive post installation traceability.

7.1.1.3 Clearly visible labeling (witho ut the need toopen the package) should be provided at each level ofpackaging.

7.1.2 Packaging and Shipping Guidelines

7.1.2.1 Double bagging should be required.

7.1.2.2 The inner bag should be nonpermeable(minimum six mil polyethylene or Nylon 6) and shouldprevent damage from normal handling.

7.1.2.3 Vacuum sealing or dry inert ga s purgingshould be used on the inner bag.

7.1.2.4 The ends of the component sho uld be protectedusing some noncontaminating method.

7.1.2.5 The outer bag may be any suit able material butshould be purged with a dry inert gas prior to sealing.

7.1.3 Documentation

7.1.3.1 Test results should be provided for eachshipment.

7.1.3.2 Shipment should be in comple te lot sizes.

7.1.3.3 The performance tests should be consideredproduction qualification tests. It is the responsibility ofthe component manufacturer to provide statisticallyvalid data which correlates their production tests tothese qualification tests (e.g., Statistical ProcessControl, MIL-STD-105D).

7.1.3.4 The equipment supplier should be responsiblefor maintaining and supplying, upon request,documentation that proves their components meet theuser’s materials performance requirements.

7.2 Receiving

7.2.1 All incoming material should be segregated from“acceptable material” until it has been formallyaccepted through documented procedure.

7.2.2 All cartons should be opened (100%); all goodsshould be checked visually for damage (e.g., torn bags,inadequate padding causing damage).

7.2.3 Material should be stored in or iginal packaging.Do not open until ready to use or inspect. Inspectioninvolving opening sealed plastic bags should beconducted within the materials staging prefabcleanroom. After inspection, purge and heat-seal thematerial into a clean polyethylene bag.

7.2.4 Any material failing initial inspection should beimmediately “red tagged” and set aside in a“quarantine” area until the supplier of the material isnotified and disposition is determined.

7.3 Acceptance and Rejection

7.3.1 All material should be uniquel y identified with aheat number, lot number, and serial number, allowingtraceability back to source and documentation. Onlymaterial so marked should be accepted.

7.3.2 All material should meet a purchasingspecification and be provided with documentation

SEMI E49.6-95 © SEMI 19953

demonstrating compliance. Only material sodocumented should be accepted.

7.3.3 A certain percentage of materi al should undergoincoming QA checks for parameters such as: surfacecontamination (e.g., hydrocarbon, particulate), tubingquality, wall thickness, nicks, scratches; surfaceroughness, pits, stringers, particle count, weldability,helium leak rate (inboard/outboard/across seat), anddimensions.The material should be accepted only after theseincoming QA checks are completed. A statisticallyvalid sample size should be determined. This meansthat sufficient pieces must be checked to guarantee thatno defective parts arrive at the buyer's location.

7.3.4 Any material that does not pass the basicincoming QA requirements should be “red tagged” andplaced in “quarantine” pending final disposition.

7.3.5 Material that passes incoming QA should beuniquely tagged.

8 Construction Procedures8.1 Tube Cutting and Preparation

8.1.1 Stainless steel tubing should be opened, cut,faced, and deburred in a required cleanroomenvironment, leaving no visible particulates inside thecut end.

8.1.2 For tube cutting, use a wheel cutter with lathe-type facing tool or a special designed power saw withalignment guide. Do not use lubricant. If any “nicks”are found, reface or discard the tube.

8.1.3 When practical during cutting and during allfacing operations, use an argon or nitrogen purge(50-100 f/s) to preclude particles from entering tubing.

8.1.4 The prepared end should conform to ASTM A632 (or ASTM A 269 ≥ 1/2" O.D.) tubing specificationwith regard to ovality and wall thickness.

8.1.5 The prepared end should be square to tube runwithin 1/4 deg. (angle).

8.1.6 After preparing, debur the inside diametercarefully and lightly. Do not scratch the insidediameter. Any scratched tubes should be reprepped orscrapped. Chamfering is not required.

8.1.7 Avoid cross-contamination fro m dissimilarmaterials.

8.2 Tube Cleaning

8.2.1 After cut and prep, tubing shou ld be cleanedusing a process which removes all debris and assuresthat the surface is totally free of hydrocarbons. Thisprocess should be custom-tailored to the supplier’s need

based on tubing supplier quality control (QC) and onpurity grade requirement (HP/UHP).

8.2.2 If using tubing certified “hydrocarbon-free” froma tubing supplier, a cleaning procedure as follows isrecommended:

• Primary rinse in cold running DI water.

• Secondary rinse in hot [80°C (176°F)] DI water.

• Final rinse in cold DI water with “pressure flush.”

• Blow dry with high velocity > 305 meters/min. (>1,000 feet/min.) hot (150°C (318°F) N2. Ensurethat drying occurs immediately after final rinse toprevent evaporation of DI from the tubing IDsurface.

• Use immediately or seal in plastic sleeves.

• Document the process through ESCA elementalchemical composition analysis and SEMphotographs that procedure does remove allcontaminants. Once process is documented, auditperiodically to assure process continues to producenoncontaminated goods.

8.3 Orbital Welding — All orbital welding should beperformed only by certified welders. Certificationprocedures should include, at the minimum, producingthree acceptable welds in a row of all types of typicalorbital weld joints of all sizes of tubing to be welded.Welding parameters should be set by the welderwithout the use of any written aids. Certificationprocess should be performed every six months.

8.3.1 Weld Equipment Setup

8.3.1.1 All welding fixtures should be clean and freeof any particulates and excessive discoloration. Weldhead should rotate freely and smoothly at all speeds. Allclamping and holding fixtures should fit tightly aroundapplicable fittings/tubing, allowing no fitting movementafter clamping in excess of 0.008 cm (0.003 in.).

8.3.1.2 Electrodes should be precision ground.Electrode gap should be set using tooling andprocedures which provide accurate and repeatable gapsto be set to within 0.005 cm (0.002 in.).

8.3.1.3 Documented procedures should exist for eachweld configuration including all parameters (includingpurge times, orifice sizes, purge rates, and internalpressure).

8.3.1.4 Purge gas apparatus should be stainless steeltubing and components with face seal fittings. Plastictubing is acceptable as the final run to allow flexibilityfor hook-up. Lengths should be restricted to less thanten feet. All components which come into contact withthe weldment should be stainless steel.

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8.3.2 Weld Bead Characteristics

8.3.2.1 All weld beads should conform to thefollowing specifications:1. All welds should exhibit complete penetration

around the entire internal surface.

2. Internal weld bead width should be 1.5 times wallthickness (± 20%).

3. Bead “snaking” should not exceed 20% of beadwidth.

4. ID encroachment of the weld bead should notexceed 0.0013 cm (0.005") from the tubing IDsurface. Weld bead should be zero undercut at allpoints.

5. Misalignment of welded pieces should be less than10% of wall thickness.

6. Zero oxidation visible on internal surfaces.

7. Light straw oxidation on external surfacespermissible.

8.3.3 Sample Welds

8.3.3.1 Sample welds or coupons shou ld be performedat the beginning of each shift, after breaks, and afterany alteration to the weld parameters. Coupons shouldbe cross-sectioned and inspected visually forpenetration, bead concavity, bead variation, andoxidation. Coupons should be logged with the date andtime and operator identification. Coupons and couponlogs should be retained for one year.

8.3.4 Purging — Extreme care shou ld be taken toensure that all contiguous flowpaths are fully purged.All dead legs must be purged out completely prior towelding. All welds should be performed with full purgeflow sweeping the weld area during and after welding.Vacuum devices may be required to overcome back-pressure in components such as regulators, filters,purifiers, check valves, or others. Dead-endcomponents such as gauges may be purged using asmall-diameter tube placed inside the tubing to bewelded and back-flowing purge through the weld zone.Pre-purging should occur for as long as necessary toassure that moisture and oxygen levels in the weld zoneare less than 100 ppb. Post-purging should continueafter the welding process until the weld zone has cooledto below 200°C (424°F). Light external oxidationshould be removed with a stainless steel wire brushimmediately after welding. Purge should be maintainedduring the brushing process, and care should be taken toperform the brushing process in an appropriate area soas not to contaminate the work area.

8.3.5 Welding Electrode

8.3.5.1 Welding electrodes should be changed asfrequently as necessary to prevent weld deterioration.At the least, electrodes should be changed every 25welds.

8.3.6 Weld Inspection

8.3.6.1 All welds should be 100% inspected to insureconformance to the weld bead specifications listed in8.3.2 and 8.3.7.

8.3.6.2 Bore scope inspections should be performed bythe welder of at least 20% of his work-in-process. Allaccessible welds should be bore scope inspected duringfinal inspection process, while protecting tubing fromscratches.

8.3.7 Dimensional and Configuration Inspection —Dimensional and configuration inspection should beperformed as follows:1. One hundred percent subassemblies should be

inspected within a cleanroom of same class asassembly area.

2. Confirm spool fabrication drawing is attached to theassembly; if not, reject.

3. Use spool sheet to verify conformance of assemblyto drawing. Check dimensions, squareness, offsets,straightedges, and levels to verify all dimensions.

4. Inspect each weld externally for undercut, widthoxidation, overlap, uniformity, and alignment.Where possible, use sightube/bore scope to inspectinterior of welds (scratch preventers essential).Where welds are not inspectable, a statisticallysignificant sample of the welds will need to be cutout to verify that the welding is done correctly.

5. When subassemblies have passed inspection, theyshould be tagged as such, rebagged, and released forfinal testing.

6. Any items found defective during inspection andrepairable may be repaired if they will not degradethe system quality measurably. If a cut must bemade into a closed system, a purge from both sides(upstream and downstream) should be established.

8.4 Subsystem Assembly Protocol — Gas panel andsolvent system assembly should be performed only bytrained competent personnel. Proper procedures fortightening face seal and other connections, valvebonnets, regulator bonnets, and other componentsshould be followed at all times. Manufacturersrecommended torque values should be followed at all

SEMI E49.6-95 © SEMI 19955

times, using a calibrated torque wrench. Purge gas atthe required purity level should be flowing throughcomponents and subassemblies at all times during theassembly process to minimize entrained contaminants.Partially assembled gas panels should be under purge orcapped at all times. Assemblers should at all times bewearing clean gloves; soiled, discolored or torn glovesshould be replaced immediately. Components,assemblies or subassemblies which are dropped ordamaged during the assembly process should be red-tagged and inspected before use. Face seal gasketswhich are dropped should be discarded. It isrecommended that two technicians should work as ateam during the assembly process. One should bedesignated as the handler and should position allcomponents. The other should exclusively handle theface seal gaskets and hand-tighten the mating fit set.

9 Testing Procedures9.1 Tests should be successfully completed and resultsdocumented for all performance parameters (purityindices) specified.

9.2 Leak rate tests should be cond ucted on 100% of allsubsystems. For UHP, use hydrocarbon free testinstruments.

9.3 Design Qualification — Gas delivery systemdesign performance should be qualified in threeparameters: particulate generation, contaminant spikerecovery, and mass flow controller replacementrecovery. This testing should be performed on theinitial gas delivery system prototype and on any designrevision which significantly impacts the componentselection or system configuration. Test results should bekept on file and made available to the end user uponrequest.

9.3.1 Particulate Generation — Stat ic and dynamicparticle testing should be performed with a flow rate ofat least 3 times the maximum process flow rate at therecommended supply pressure, except during mass flowcontroller testing when test flow rates should bebetween 0% and 80% of the MFC value. Testing shouldbe performed on all flow paths that differ significantlyin components or configuration. Dynamic test protocolsshould be as follows:

• Each valve in the test flow path should be cycledindividually.

• Starting with the valve furthest upstream, cycleeach valve once every 20 seconds.

• MFC valves should be cycled from 0% to 100%.

• Test interval should last until 0.085 std. m3/hr. (3std. ft3/hr.) of gas flow through the test flow pathhas been sampled by the particle counter.

9.3.2 Contaminant Spike Recovery — Contaminantspike recovery testing should be performed on all flowpaths which differ significantly in configuration orcomponents. This test should be performed at a flowrate equivalent to typical flow rates achieved in purgeand vent cycles for the specific flow path. Contaminantspike recovery test protocols are:

• With all components placed in the full openposition, mass flow gas moisture level should be atbaseline for 30 minutes prior to testing to establishstable background.

• When a stable background is achieved, initiate a 2ppm (v) moisture spike until the outlet moistureconcentration reaches 2 ppm. (Remove themoisture source from the test gas, and monitorelapsed time until moisture level reaches specifiedlevel.)

• Spike recovery time should be ≤ 8 hours for highpurity systems and ≤ 4 hours for ultra high puritysystems.

• Similar procedure should be conducted for oxygenand THC level tests where required.

9.3.3 Mass Flow Controller Replacement Recovery —MFC replacement recovery testing should be performedon all flow paths differing significantly in componentsand configuration. This test should be performed with aflow rate equivalent to flow rates achieved in typicalpurge and vent cycles for the specific flow path. MFCreplacement recovery test protocols should be:

• Valves and purge flows should be set up in thecomponent replacement mode, and the MFCshould be removed from the flow path.

• After 15 minutes, a replacement MFC should beinstalled.

• Cycle purging should be performed at therecommended pressures and for the recommendednumber of cycles.

• Typical purge and vent flow rates should then beestablished, and the moisture level of the test gasshould be monitored over time.

• For high purity systems, the moisture level shouldachieve background levels within one hour.

• For ultra high purity systems, the moisture levelshould achieve background levels within 15minutes.

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9.4 Manufacturing Qualification — Manufacturingqualification tests should be performed to verify themanufacturing and quality control procedures followedin the manufacturing of the gas delivery system. As theconfiguration of gas systems varies greatly fromprocess to process, no specification should be givenhere other than to state that static and dynamic particletesting, moisture level, oxygen level, and hydrocarbontesting should be performed to provide statisticallysignificant data showing that the gas delivery systemwill meet the purity levels required.

9.5 Certification — Certification for gas deliverysystems should include: leak rate certification, particlecounts with specified flow rates at specified pressuresand flow schematic indicating which flow paths weretested and which components were cycled; moisturelevel plotted against time with specified flow rates atspecified pressures and flow schematic indicatingwhich flow paths were tested; and oxygen orhydrocarbon levels plotted against time with specifiedflow rates at specified pressures and flow schematicindicating which flow paths were tested.

10 Labeling ProtocolAll lines should be labeled by gas type and flowdirection.

11 Pre-Packaging Protocol11.1 After testing is completed, the subassemblyshould be pressurized with UHP grade Argon or N2.Each process line should be sealed with a closed valveand metal fitting cap or plug; all nonprocess linesshould be sealed with a plastic cap or plug before beingshipped.

11.2 Lines separate from gas system should beshipped double bagged from the cleanroom. Bagsshould be nonpermeable material and purged with inertgas, then sealed from atmosphere.

12 Documentation ProtocolDocumentation logs should be kept for all shopactivities. Example log sheets are shown as Tables 1–6below.

SEMI E49.6-95 © SEMI 19957

Table 1 Stainless Steel Component Inspection Log

Stainless Steel Component Inspection Log

Customer: Date:

Location: Page __ of __

Project: Cert: Yes/No

Date Received: Lot No.: Heat No.:

Description Wall Thickness Diameter Visual Surface Finish RA QA

Min. Max. Min. Max.

Table 2 Weld Log or Weld Coupon Log

Weld Log or Weld Coupon Log

Customer: Date Begun:

Location: Page __ of __

Project: Welder:

Number Size Description Visual Color Uniformity Heat/Lot Coupon Date Comments QA

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Table 3 Pressure Hold Test Report

Pressure Hold Test Report

Customer: Date:

Location: Report:

Project:

System:

Time Started: Time Finished:

Start Temperature: Finish Temperature:

Start Pressure: Finish Pressure:

Elapsed Time: Finish Pressure Corrected:

Pressure Difference Corrected:

Elapsed Time:

Gas (or Mixture) Used for Test:

Pressure Gauge Range:

Comments:

Tested by: Date:

QA Representative: Date:

Table 4 Particle Count Test Report

Particle Count Test Report

Customer: Date:

Location: Report:

Counter Instrument/Model Serial Number

LPC

CNC

Date Time System Particle Counts > 0. µm Flow Rate/Pressure

Comments:

Tested by:

QA Representative:

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Table 5 Trace Moisture and Oxygen Test Report

Trace Moisture and Oxygen Test Report

Customer: Date:

Location: Report:

Type Instrument/Model Serial Number

Trace O2

Trace H2O

Date Time System Inboard Leak Rate Comments

Comments:

Tested by:

QA Representative:

Table 6 Helium Leak Test Report

Helium Leak Test Report

Customer: Date:

Location: Report:

Project:

Type Instrument/Model Serial Number

He MSLD

Date Time System Inboard Leak Rate Comments

Comments:

Tested by:

QA Representative:

SEMI E49.6-95 © SEMI 1995 10

NOTICE: These standards do not purport to addresssafety issues, if any, associated with their use. It is theresponsibility of the user of these standards to establishappropriate safety and health practices and determinethe applicability of regulatory limitations prior to use.SEMI makes no warranties or representations as to thesuitability of the standards set forth herein for anyparticular application. The determination of thesuitability of the standard is solely the responsibility ofthe user. Users are cautioned to refer to manufacturer’sinstructions, product labels, product data sheets, andother relevant literature respecting any materialsmentioned herein. These standards are subject tochange without notice.

The user’s attention is called to the possibility thatcompliance with this standard may require use ofcopyrighted material or of an invention covered bypatent rights. By publication of this standard, SEMItakes no position respecting the validity of any patentrights or copyrights asserted in connection with anyitem mentioned in this standard. Users of this standardare expressly advised that determination of any suchpatent rights or copyrights and the risk of infringementof such rights, are entirely their own responsibility.

Copyright by SEMI® (Semiconductor Equipment and MaterialsInternational), 3081 Zanker Road, San Jose, CA 95134. Reproduction ofthe contents in whole or in part is forbidden without express writtenconsent of SEMI.