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Materials for Vacuum and Semiconductor Equipment Parts
Grade, temper and certificate decide whether a part can go into the tool. The designations below cover ASTM and UNS, EN and JIS, so a drawing written in one system reads the same to a shop that buys stock in another.
Metal grades and their designations
Equivalents are close, not identical. Chemistry limits differ slightly between standards, so name the standard you release against and let the shop buy to it.
| Material | UNS | EN | JIS | Usual form and temper | Where it is used |
|---|---|---|---|---|---|
| Aluminum 6061 | A96061 | EN AW-6061 | A6061 | T6 or T651 plate and bar | Chamber bodies, lids, brackets, most structural parts |
| Aluminum 5083 | A95083 | EN AW-5083 | A5083 | O, H111 or H321 plate | Large chamber bodies, welded vacuum structure |
| Aluminum 5052 | A95052 | EN AW-5052 | A5052 | H32 sheet and plate | Covers, ducting, sheet metal enclosures |
| Stainless 304L | S30403 | 1.4307 | SUS304L | Annealed bar and plate | Frames, foreline parts, non wetted vacuum structure |
| Stainless 316L | S31603 | 1.4404 | SUS316L | Annealed bar, plate and tube | Gas wetted parts, flanges, UHV hardware |
| Stainless 316LN | S31653 | 1.4429 | SUS316LN | Annealed, often remelted | CF flanges and bakeable UHV parts |
| Titanium Grade 2 | R50400 | 3.7035 | Class 2 | Annealed bar and plate | Corrosive process areas, PVD parts |
| Titanium Grade 5 | R56400 | 3.7165 | TAP6400 | Annealed bar and plate | Light stiff parts, wafer handling arms |
| Molybdenum | R03600 | n/a | n/a | Stress relieved rod and plate | Heat shields, hot zone and implant hardware |
| OFE copper | C10100 | CW009A | C1011 | Annealed or half hard | CF gaskets, cooling blocks, RF parts |
Plate and bar standards worth naming on the drawing: ASTM B209 and B221 for aluminum, ASTM A240 and A276 for stainless, ASTM B265 and B348 for titanium, ASTM F68 for oxygen free copper.
Aluminum or stainless
Most chamber parts are one or the other. The choice is made by temperature, process chemistry and how the part is joined, more than by strength.
Aluminum 6061 and 5083
- Light, fast to machine, cheaper per part
- Conducts heat well, good for cooled lids and plates
- Takes Type III hard anodize for plasma facing surfaces
- Lower bake temperatures than stainless
- Sealing faces scratch easily, so handling and packing matter
Stainless 304L and 316L
- Bakeable to higher temperatures for UHV work
- Welds to leak tight joints, standard for CF hardware
- Electropolished for gas wetted purity
- Heavier and slower to machine, work hardens
- Low carbon L grades limit sensitization at welds
Plate choice inside aluminum: 6061, 5083 and cast tooling plate for chambers. Purity grades of stainless: 316L VIM-VAR for UHP gas lines.
What to keep out of a vacuum part
These are the materials and habits that pass a dimensional check and then fail at pump down or bake.
- Zinc and cadmiumBoth have a high vapour pressure and contaminate a chamber when baked. That rules out brass, 7075 and other zinc bearing alloys and cadmium plated fasteners inside the vacuum.
- Free machining gradesSulfur and lead are what make 303, 12L14 and 2011 cut easily. They outgas, they hurt weld quality and they show as inclusions on a polished face. Specify 304L or 316L, not 303.
- Porous cast materialCasting porosity traps gas and cleaning fluid and releases both under vacuum. Wrought plate or bar for anything that sees vacuum, unless the casting is qualified for it.
- Silicone and unknown lubricantsSilicone migrates and is hard to remove. Ask the shop which coolant and lubricants touch the part, and say on the drawing if silicone is banned.
- Unvented blind volumesNot a material, but it behaves like one. Gas trapped behind a screw or in a blind hole leaks out slowly and reads as a bad pump down.
Why it matters at low pressure: outgassing.
Polymers and ceramics
Temperatures are typical continuous service limits from material makers, not vacuum bake limits. Fillers, pigments and the grade change both the limit and the outgassing.
| Material | Usual form | Typical service limit | Where it is used |
|---|---|---|---|
| PEEK, unfilled | Extruded rod and plate | About 250 °C continuous | Insulators, wafer contact parts, CMP rings |
| Polyimide (Vespel SP-1 type) | Direct formed shapes | About 290 °C continuous | High temperature insulators, wear pads |
| PPS | Extruded or compression molded | About 220 °C continuous | CMP retaining rings, chemical side parts |
| PTFE and PFA | Molded rod and sheet | About 260 °C continuous | Wet process parts, seals, liners |
| Alumina 99.5 percent | Fired, then ground or lapped | Well above process range | Insulators, wafer contact parts, usually a ceramic house |
ASTM E595 is the common outgassing screen for polymers: total mass loss of 1.0 percent or less and collected volatile condensable material of 0.10 percent or less. Ask for the maker's data on the exact grade. More in PFA, PVDF and PEEK for wet process tools and alumina and AlN in wafer tools.
Certificates and traceability
The paperwork is part of the material. Put the certificate type on the drawing or it will not be in the quote.
- EN 10204 3.1Inspection certificate from the material maker with the measured chemistry and mechanical results of the heat. The normal request for vacuum and gas parts.
- EN 10204 3.2The same results, also confirmed by an independent inspector or the buyer's representative. Asked for on critical parts only, and it adds time at the mill.
- Heat lot traceabilityThe heat number from the certificate is marked or recorded against each part or lot, so a material question can be traced to the stock that was used.
- Restricted material listIf your company bans substances or requires a declaration, send the list with the RFQ. It narrows which stock a shop can buy at all.
- Finish certificatesAnodize, plating and electropolish lines issue their own certificate per batch. Ask for it with the dimensional report.
Questions about materials
Is 6061 or 5083 better for a chamber body?
6061-T6 machines cleanly, holds a sealing face well and takes hard anodize evenly, so it covers most machined chamber bodies and lids. 5083 is the usual pick for large welded bodies, because it keeps more of its strength after welding and is supplied in thick plate. Weld design usually decides it.
Do I need 316L or will 304L do?
For structure and foreline parts 304L is normally enough. Gas wetted parts, parts that are electropolished for purity and parts that see corrosive process gas usually call for 316L, and ultra high purity gas lines often go further to 316L VIM-VAR. The molybdenum in 316L is what improves the corrosion resistance.
What is a 3.1 certificate and do I need one?
An EN 10204 type 3.1 inspection certificate is issued by the material maker and states the measured chemistry and mechanical results for that heat. Most vacuum and gas part drawings ask for one, tied to the heat lot of the actual stock used. A stockist certificate that only repeats the grade name is not the same document.
Can PEEK go inside the chamber?
Often, yes. Unfilled PEEK and polyimide are common inside vacuum because they outgas little after a bake. Check the grade, because fillers and pigments change the result, and ask the material maker for outgassing data measured to ASTM E595.
Material decided? Send the drawing.
Put the grade, the standard and the certificate type in the RFQ. We pass it to up to 3 shops that already buy that stock and reply within 24 business hours.
- ProcessesMachining, finishing, cleaning and test steps.
- ApplicationsWhich material goes where, by tool module.
- Molybdenum and titaniumRefractory and light metals in vacuum.