Semiconductor-Grade Chemical Specification: Purity 5N-7N, Metal Ion Limit and Particle Count

Overview #

The specification parameter that separates a qualified semiconductor-grade chemical supplier from a commodity chemical distributor is not the purity grade printed on the label — it’s the metal ion profile and particle count data across consecutive production lots. A supplier can deliver 5N (99.999%) purity on a single COA and still contaminate your process if sodium or potassium ions exceed 1 ppb in a gate oxide application. When our team qualifies Chinese suppliers for semiconductor-grade chemicals, we start with three consecutive lot COAs and incoming ICP-MS verification — not the datasheet.

The Chinese semiconductor chemical supply chain has matured significantly since 2018, but the gap between tier-1 domestic suppliers (serving SMIC, YMTC) and export-grade distributors remains wide. Most overseas buyers encounter the export tier first, which operates with looser internal QC than what the domestic fab customers require. Understanding where your specification sits on the 5N–7N purity ladder — and which impurity limits actually govern your process node — is the first decision that determines whether your sourcing will succeed.

Purity Grade Classification and Metal Ion Limits by Process Node #

Semiconductor-grade chemical purity is expressed in “nines” notation: 5N = 99.999%, 6N = 99.9999%, 7N = 99.99999%. The notation is necessary but insufficient. Two chemicals both labeled 6N can have radically different metal ion profiles, and it is the metal ion profile — not the bulk purity percentage — that determines process compatibility.

The governing framework for semiconductor chemical purity in international procurement is SEMI Standards, specifically the SEMI C-series. SEMI C7 covers hydrogen peroxide, SEMI C8 covers sulfuric acid, and SEMI C12 covers hydrofluoric acid — each with tiered grades (SEMI Grade 1 through Grade 5) that map to process node requirements. Grade 3 corresponds roughly to 28nm–65nm applications; Grade 4 and Grade 5 are required for 14nm and below. Chinese domestic standards are published under SAC China Standards (GB/T), but GB/T purity tiers do not align 1:1 with SEMI grades — a point that causes specification errors at the sourcing stage more often than any other single factor.

For metal ion limits, the critical analytes in most wet process chemicals are Na, K, Fe, Cu, Cr, Ni, Al, and Ca. At 28nm nodes, individual metal ion limits are typically ≤1 ppb per element, with total metals ≤10 ppb. At 7nm and below, individual limits tighten to ≤0.1 ppb for Cu and Fe, and ≤0.5 ppb for Na and K. These are not marketing thresholds — they are process-driven limits derived from contamination studies at leading fabs. A supplier who cannot provide ICP-MS data at sub-ppb resolution is not operating at the specification level required for advanced nodes.

Particle count is the second critical axis. For 300mm wafer processing, the standard requirement is ≤50 particles/mL at ≥0.2 µm for bulk chemical delivery, tightening to ≤10 particles/mL at ≥0.1 µm for point-of-use (POU) applications. Chinese suppliers qualified for domestic 28nm production typically meet the 50 particles/mL threshold; fewer than 20% of the suppliers we have evaluated can consistently demonstrate ≤10 particles/mL at ≥0.1 µm across production lots.

Most Western buyers do not realize that the SEMI Grade classification system is voluntary — Chinese suppliers are not required to certify to SEMI C-series grades, and many use the SEMI grade label as a marketing descriptor without formal third-party verification. We have seen COAs from Chinese distributors that cite “SEMI Grade 4 equivalent” with no ICP-MS data to support the metal ion claims. That phrase — “equivalent” — is a red flag. Either the data supports the grade or it does not.

For semiconductor-grade chemical sourcing alongside related electronic substrate materials, the same incoming inspection discipline applies across the category.

Critical Selection Criteria: Six Parameters That Determine Supplier Qualification #

1. ICP-MS Detection Capability at Sub-ppb Resolution

The analytical method used to generate the COA metal ion data is as important as the numbers themselves. ICP-OES (optical emission spectrometry) has a detection limit of approximately 1–10 ppb for most metals — adequate for 65nm applications but insufficient for 14nm and below. ICP-MS (mass spectrometry) achieves detection limits of 0.01–0.1 ppb, which is the required resolution for advanced node qualification. When requesting COAs from Chinese suppliers, always ask which instrument was used and request the instrument calibration certificate. If the COA shows metal ion values of exactly “< 1 ppb” across all analytes without decimal resolution, the data was almost certainly generated by ICP-OES, not ICP-MS — and the supplier is not operating at the analytical level required for sub-28nm applications.

2. Lot-to-Lot Consistency Data (Six-Month Minimum)

Single-lot COA data is a qualification entry ticket, not a qualification. In our supplier evaluation program, we require a minimum of six consecutive monthly lot COAs before recommending a Chinese supplier for volume procurement. The acceptance criterion we apply is a coefficient of variation (CV) ≤15% for each critical metal ion across the six lots. Suppliers who cannot provide this data — or who provide it only upon request after a long delay — are typically relying on spot-testing rather than systematic QC. The difference sounds administrative. In production, a single out-of-spec lot at 7nm can result in wafer scrap costs that dwarf the annual chemical spend.

3. Packaging Material Compatibility

At 6N and 7N purity levels, the packaging material is a contamination source. HDPE containers leach trace metals and organic compounds into ultra-high-purity chemicals over time — the leaching rate accelerates above 40°C and with oxidizing chemicals like H₂O₂ and HNO₃. For Grade 4/5 applications, FEP (fluorinated ethylene propylene) or PFA (perfluoroalkoxy) containers are required. Chinese suppliers serving domestic advanced fabs use PFA containers as standard; suppliers serving the export market frequently default to HDPE unless the specification explicitly requires otherwise. This is a purchase order line item, not an assumption.

4. Particle Count Verification Method

Particle count data on a COA is only as reliable as the measurement method. The standard method for semiconductor chemical particle counting is light obscuration (LO) per ASTM International ASTM F658, or laser particle counting per SEMI C21. Suppliers who report particle counts without specifying the measurement method and particle size threshold are providing data that cannot be compared to your process specification. Require the method, the instrument model, and the size threshold (0.2 µm or 0.1 µm) on every COA.

5. Anion Impurity Profile

Metal ions receive most of the specification attention, but anion impurities — chloride (Cl⁻), sulfate (SO₄²⁻), nitrate (NO₃⁻) — are process-critical in many wet etch and clean applications. For HF used in oxide etch, chloride content above 0.5 ppm can cause stainless steel tool corrosion and introduce Fe contamination downstream. For H₂SO₄ used in SPM (sulfuric acid/hydrogen peroxide mixture) cleans, nitrate above 1 ppm interferes with photoresist strip uniformity. These limits are rarely specified on standard COAs from Chinese suppliers — they must be explicitly requested.

6. Dissolved Gas Content (for H₂O₂ and NH₄OH)

For hydrogen peroxide and ammonium hydroxide, dissolved oxygen and dissolved ammonia content affect process stability in SC-1 and SC-2 clean sequences. H₂O₂ decomposition rate — measured as % active oxygen loss per 30 days at 25°C — should be ≤0.5% for Grade 4/5 material. Chinese suppliers rarely include this parameter on standard COAs. It must be specified in the purchase order and verified by incoming titration.

Most procurement teams over-specify bulk purity grade and under-specify the parameters that actually drive process yield: particle count at the relevant size threshold, anion profile, and packaging material. We have seen buyers pay a 40% price premium for “7N” labeled material from a Chinese distributor, then fail incoming inspection on particle count because the supplier used HDPE drums for a 300mm fab application.

Compliance, Certification and Incoming Inspection Requirements #

Semiconductor-grade chemicals sourced from China for use in fabs outside China must navigate two compliance layers: the chemical safety and transport regulations of the destination country, and the process-specific purity requirements of the fab.

For chemical safety, the primary frameworks are REACH (ECHA) for EU-bound shipments and OSHA Standards for US facilities. Both require Safety Data Sheets (SDS) compliant with GHS (Globally Harmonized System) format. Chinese suppliers are required to provide GHS-compliant SDS under domestic regulations, but the English-language SDS quality from Chinese chemical exporters is inconsistent — we routinely find SDS documents that list incorrect UN numbers or missing transport hazard classifications for concentrated acids and oxidizers. Request the SDS before the first shipment and verify the UN number, hazard class, and packing group against the IATA Dangerous Goods Regulations before approving the logistics chain.

For incoming inspection, the minimum protocol we recommend for semiconductor-grade chemicals from a new Chinese supplier is:

• ICP-MS metal ion scan (all 8 critical analytes) on the first three lots
• Particle count verification by laser counter at the specified size threshold
• Titration for active ingredient concentration (±0.1% of specification)
• pH verification (±0.05 pH units of specification)
• Visual inspection for color, clarity, and container integrity

After three lots pass incoming inspection with CV ≤15% across metal ion analytes, the protocol can be reduced to ICP-MS spot-testing on 1 in 5 lots, with full re-qualification triggered by any single lot failure.

The English technical content available for semiconductor-grade chemicals from Chinese suppliers is almost entirely produced by Western chemical brand owners (BASF, Stella Chemifa, KMG) or by fab process engineers. Chinese domestic suppliers publish almost no English-language technical documentation at the process specification level. That gap is why overseas buyers consistently under-specify when writing purchase orders for Chinese-sourced semiconductor chemicals — they are working from Western brand datasheets and assuming the Chinese product maps to the same specification. It frequently does not.

For related conductive and functional materials used in display and semiconductor applications, the same incoming inspection discipline around metal ion contamination applies, particularly for ITO targets and conductive pastes where trace metal profiles affect device performance.

Practical Guidance for Buyers #

When sourcing semiconductor-grade chemicals from China, the first specification to request from any supplier is not the purity grade — it is the ICP-MS metal ion data at sub-ppb resolution, with the instrument model and calibration date on the COA. Most buyers ask for the purity certificate first. That is the wrong starting point. A supplier who cannot provide ICP-MS data at 0.1 ppb resolution for Cu and Fe is not operating at the analytical level required for 14nm and below, regardless of what purity grade is printed on the label.

The most common sourcing mistake we see is accepting a single-lot COA as qualification evidence. One lot can pass. The risk is lot-to-lot consistency — and in our evaluation program, three out of five Chinese suppliers we assessed for advanced node chemicals could not demonstrate CV ≤15% across six consecutive lots for Na and K. The consequence of that inconsistency is not a failed incoming inspection — it is a yield excursion that takes two to four weeks to trace back to the chemical source.

Before committing to volume order, require: (1) six consecutive lot COAs with ICP-MS data, (2) particle count data specifying method and size threshold per ASTM F658 or SEMI C21, and (3) packaging material certification confirming FEP or PFA containers for Grade 4/5 applications. These three documents will tell you more about a supplier’s actual capability than any factory audit.

What to Specify in Your Purchase Order: Checklist #

Use this checklist as a minimum specification framework for semiconductor-grade chemical purchase orders from Chinese suppliers:

Purity and Bulk Composition
– [ ] Purity grade: specify nines notation (5N / 6N / 7N) AND SEMI C-series grade (Grade 3 / 4 / 5)
– [ ] Active ingredient concentration: specify target % ± tolerance (e.g., 49.0% HF ± 0.5%)
– [ ] Specify that GB/T compliance alone is NOT acceptable — SEMI grade compliance required

Metal Ion Limits
– [ ] Individual metal ion limits for Na, K, Fe, Cu, Cr, Ni, Al, Ca — specify in ppb with decimal resolution
– [ ] Total metals limit — specify in ppb
– [ ] Specify ICP-MS as required analytical method (not ICP-OES)
– [ ] Require instrument model and calibration date on COA

Particle Count
– [ ] Specify particle count limit at ≥0.2 µm (e.g., ≤50 particles/mL for 28nm)
– [ ] Specify particle count limit at ≥0.1 µm if POU application
– [ ] Specify measurement method: ASTM F658 or SEMI C21
– [ ] Require instrument model on COA

Anion Impurities
– [ ] Chloride (Cl⁻): specify limit in ppm (e.g., ≤0.5 ppm for HF)
– [ ] Sulfate (SO₄²⁻): specify limit in ppm
– [ ] Nitrate (NO₃⁻): specify limit in ppm

Packaging and Handling
– [ ] Specify container material: HDPE (Grade 3), FEP or PFA (Grade 4/5)
– [ ] Specify container volume and closure type
– [ ] Require GHS-compliant English SDS with correct UN number before first shipment

Lot Consistency and Documentation
– [ ] Require six consecutive lot COAs before volume order approval
– [ ] Specify CV ≤15% acceptance criterion for critical metal ions across lots
– [ ] Require lot number, production date, and expiry date on every COA
– [ ] Specify shelf life requirement (e.g., ≥12 months from production date for H₂O₂)

Frequently Asked Questions #

Q1: What is the difference between 5N, 6N, and 7N purity for semiconductor chemicals, and which grade do I need?

A: The nines notation describes bulk purity, but your process node determines the grade: 5N (99.999%) is adequate for display and advanced packaging; 6N (99.9999%) is the minimum for 28nm–14nm fab applications; 7N (99.99999%) is required for leading-edge nodes at 7nm and below. More importantly, always cross-reference the nines grade with the SEMI C-series grade — a supplier claiming 6N but unable to meet SEMI Grade 4 metal ion limits of ≤0.1 ppb for Cu and Fe is not qualified for 14nm applications regardless of the bulk purity number.

Q2: How do I evaluate whether a Chinese supplier’s COA metal ion data is reliable?

A: Check the analytical method first. If the COA does not specify ICP-MS and shows all metal values as “< 1 ppb” without decimal resolution, the data was generated by ICP-OES — which has a detection limit of 1–10 ppb and cannot resolve the sub-ppb values required for advanced node qualification. Reliable COAs from qualified Chinese suppliers will show values like “Na: 0.23 ppb, K: 0.18 ppb” with the instrument model listed.

Q3: What is the most common quality failure when sourcing semiconductor chemicals from Chinese suppliers?

A: Lot-to-lot inconsistency on metal ions, not single-lot purity. This is where most sourcing decisions go wrong. The threshold we apply is CV ≤15% across six consecutive lots — and in our evaluation program, the majority of Chinese suppliers at the export tier fail this criterion for Na and K specifically.

Q4: What compliance documentation should I require for semiconductor chemicals shipped from China to the EU or US?

A: Require a GHS-compliant English SDS with the correct UN number, hazard class, and packing group before the first shipment — verify these against REACH (ECHA) requirements for EU destinations or OSHA Standards for US facilities. Also require the SEMI C-series grade declaration in writing on the commercial invoice, not just on the COA.

Q5: Is a Chinese supplier’s GB/T certificate equivalent to SEMI Grade certification?

A: No. SAC China Standards (GB/T) purity tiers do not align with SEMI C-series grades, and GB/T compliance does not guarantee SEMI Grade 3, 4, or 5 metal ion limits. Treat GB/T certification as a baseline quality indicator only — never as a substitute for SEMI grade compliance in a fab procurement specification.

Published by sinoraw.com Technical Team | Dr. Grace Liang, Electronic and Specialty Materials Engineer | Request a sourcing consultation