Purity 99.9999% · CAS 7440-50-8 · Cu
Copper Powder 99.9999% (6N) — semiconductor grade
Semiconductor interconnect, ultra-high purity PVD
Overview
At six nines, copper is typically zone-refined after electrolytic refining and handled under inert gas, with alkali and radioactive element counts controlled for front-end semiconductor use. GDMS and ICP-MS are the usual certification methods at this grade; the scope that applies to a given lot is confirmed in writing.
Typical trace impurities
| Impurity | Typical max |
|---|---|
| O (oxygen) | ≤ 300 ppm |
| Na + K | ≤ 0.1 ppm |
| U + Th | ≤ 0.001 ppm |
| Fe | ≤ 0.5 ppm |
Indicative values. The certificate of analysis for your lot is the binding document.
Where this grade is used
- ▪Semiconductor interconnect and damascene plating
- ▪Ultra-high-purity sputtering target manufacture
- ▪Compound semiconductor and photovoltaic research
- ▪Metrology and calibration standards
Common forms
Argon-packed spherical powder, nanopowder
Specification at a glance
| Material | Copper Powder (Cu) |
|---|---|
| Purity | 99.9999% (6N), metals basis |
| CAS | 7440-50-8 |
| Production route | Electrolytic refining followed by inert-gas atomisation and zone-refined feedstock control |
| Available forms | Argon-packed spherical powder, nanopowder |
| Analysis method | GDMS (glow-discharge mass spectrometry) full trace scan |
| Documentation | Certificate of analysis per lot, RoHS and REACH statements, country of origin, full GDMS scan and conflict-minerals declaration on request |
| Typical packaging | Packing confirmed per lot, in writing |
What 99.9999% (6N) actually means
6N is shorthand for 99.9999% purity on a metals basis: at most 0.0001% of the material, by weight, is something other than Cu. The metals-basis convention excludes dissolved gases and, for powders, surface oxygen — which is why oxygen is quoted separately in the trace table below.
Two lots at the same nominal purity are not interchangeable if the residual elements differ. For this grade the limiting element is typically O (oxygen) at ≤ 300 ppm. What matters is which impurities your process is sensitive to — judge a lot on its full trace analysis, not on the headline number.
Choosing 6N versus the neighbouring grades
Coming from 99.999% (5N): the step up buys you tighter trace control for semiconductor interconnect, ultra-high purity pvd. If your process tolerates the residuals of 5N, the lower grade remains the more economical and more widely available choice.
Going up to 99.99999% (7N) is worth it when research quantities only — zone-refined describes your application; expect a materially higher cost per kilo and scarcer availability for a difference few processes can detect otherwise.
When in doubt, qualify both adjacent grades on a sample and run your own incoming inspection before committing a process to either.
Why 6N is the semiconductor reference grade
At six nines, the specification stops being about the copper and becomes about what is absent. Two impurity families dominate front-end semiconductor thinking: alkali metals (sodium, potassium), which drift under electric fields and degrade gate oxides, and the naturally alpha-active elements uranium and thorium, whose emissions cause soft errors in memory and imaging devices. At 6N both families sit at or below what routine ICP-MS can quantify, which is why lots at this level are certified by GDMS.
Producing 6N copper is a chain of purifications rather than a single step: electrolytically refined cathode is zone-refined, re-melted and atomised under argon, then screened and packed without re-exposure to air. Every handling step is a chance to pick up iron from tooling or oxygen from the atmosphere, so a serious lot certificate documents the whole chain, not a single measurement.
Powder adds a further difficulty that solid 6N metal does not have: surface area. A kilogram of 20 µm powder presents square metres of copper to the air, and surface oxide is excluded from the metals-basis assay — so oxygen is quoted separately, and argon packing is part of the specification, not a packaging option.
- ▪Typical 6N limits: alkalis (Na + K) around 0.1 ppm for interconnect and gate-oxide integrity
- ▪Typical 6N limits: alpha emitters (U + Th) around 0.001 ppm against soft errors
- ▪Iron and oxygen are watched separately; oxygen sits outside the metals-basis assay
- ▪The limits and analysis scope that apply to your lot are confirmed in writing
Where 6N copper powder is actually used
The defining use is semiconductor interconnect: damascene plating chemistry and ultra-high-purity sputtering targets for copper metallisation, where the target or bath becomes the wiring of the chip. Beyond that, 6N feedstock serves compound-semiconductor and photovoltaic research, metrology and calibration standards, and cryogenic work where residual-resistance ratio is the figure of merit.
If your process is not sensitive to alkali or alpha emitters, 5N or even 4N will usually measure identically in your application — the comparison section above covers how to decide.
Quality control and traceability
Copper Powder at 99.9999% is normally released against a lot-specific certificate of analysis stating the assay, the trace elements measured and the method used (GDMS (glow-discharge mass spectrometry) full trace scan). Well-run lots stay traceable from the refinery batch through to the container that reaches the laboratory.
- ▪A retained sample per lot, so a later question can be re-tested against the original material
- ▪Independent third-party verification, used when the assay is contractually critical
- ▪Incoming inspection on the receiving side — the certificate states the method, not the result you will measure
Handling, storage and shipping
- ▪Fine copper powder oxidises at the surface; keep containers sealed and open them under inert gas or dry air for grades from 5N upward.
- ▪Sub-45 µm cuts are classified as a combustible dust — ground equipment, avoid dust clouds and follow ATEX or NFPA 484 practice on site.
- ▪Store between 5 °C and 30 °C at low humidity, away from ammonia, acids and sulphur compounds.
Frequently asked questions
Common questions from buyers specifying copper powder at 99.9999%.
- Is 99.9999% copper powder the right grade for my application?
- It is the usual choice for semiconductor interconnect, ultra-high purity pvd. Below it, 99.999% (5N) covers less demanding work at lower cost. Above it, 99.99999% (7N) is reserved for research quantities only — zone-refined.
- What does the 6N designation mean?
- The N notation counts the nines in the assay: 6N equals 99.9999% Cu on a metals basis, with the balance made up of the trace elements listed in the analysis table.
- Which impurities are measured and reported?
- GDMS (glow-discharge mass spectrometry) full trace scan is used, and a certificate of analysis reports each element in the table above, starting with O (oxygen) at ≤ 300 ppm. The scope of a scan can be widened to further elements when a process is sensitive to one in particular.
- How is this grade normally packed?
- Packing confirmed per lot, in writing. Sub-45 µm cuts are classified as a combustible dust — ground equipment, avoid dust clouds and follow ATEX or NFPA 484 practice on site.
- Which forms is 99.9999% copper powder available in?
- Commonly: argon-packed spherical powder, nanopowder. The form is often a bigger practical constraint than the assay itself, because the last processing step has to preserve the purity already achieved.
- What is the practical difference between 5N and 6N copper powder?
- Ten times less total metallic impurity — but the decisive gap is in specific elements: 6N controls alkali metals (Na + K ≤ 0.1 ppm) and alpha emitters (U + Th ≤ 0.001 ppm) that 5N certificates often do not quantify. If your process touches gate oxides or memory devices, that difference is the reason 6N exists.
- Why are uranium and thorium limited in 6N copper?
- Both are naturally occurring alpha emitters. In a chip, an alpha particle from a trace of uranium or thorium can flip a memory bit — a soft error. Front-end specifications therefore cap U + Th at parts-per-trillion level, a range that only GDMS can verify reliably.
- Why is oxygen quoted separately at 6N?
- The nines count metals only. A powder's surface oxide is real contamination for your process but invisible in the metals-basis assay, so certificates at this grade list oxygen on its own line. The value and the packing that apply to your lot are confirmed in writing.
Buying copper powder?
We supply 2N to 7N copper powder from high-security bonded storage at Zurich Airport — no import duties or VAT while in bond, from a qualification jar to recurring tonnage. Written trade inquiries only.
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