Plasma gas corrosion test

Plasma Gas Corrosion Testing – Material Compatibility Assessment for Semiconductor, Aerospace and High-Voltage Applications

As an ISO/IEC 17025 accredited (CNAS) independent laboratory, we provide specialized plasma gas corrosion testing services for industries in Algeria including semiconductor manufacturing, aerospace components, power transmission equipment, and vacuum systems. Plasma environments — whether generated for etching, deposition, surface activation, or occurring as parasitic plasmas in high‑voltage switchgear — can aggressively attack metals, ceramics, polymers, and coatings. Our testing evaluates material resistance to chemically reactive plasmas (fluorine‑based, chlorine‑based, oxygen, nitrogen, hydrogen), measures corrosion rates, identifies degradation mechanisms, and supports material selection for plasma‑exposed components.

Types of Samples and Components We Test

• Semiconductor process chamber components (gas distribution plates, showerheads, focus rings, electrostatic chucks, chamber liners, viewports)
• Plasma etching and deposition system parts (electrodes, RF feedthroughs, bellows, dielectric windows, susceptors)
• li>High‑voltage switchgear and circuit breaker internal components (arc chutes, contact assemblies, insulation barriers)
• Vacuum vessel materials (stainless steel 304, 304L, 316L, 316LN; aluminum alloys 6061, 5083; Inconel 625, 718; titanium and titanium alloys)
• Ceramic components (alumina Al₂O₃, yttria Y₂O₃, aluminum nitride AlN, silicon carbide SiC, silicon nitride Si₃N₄, quartz, sapphire windows)
• Polymer seals and gaskets (Viton, Kalrez, Chemraz, silicone, PTFE, PEEK, polyimide)
• Protective coatings (plasma‑sprayed yttria, anodized aluminum, CVD diamond‑like carbon, PVD coatings)
• Electrode materials (tungsten, molybdenum, tantalum, graphite, silicon, platinum, gold)
• Electrical insulation materials (epoxy, polyimide films, ceramic standoffs, glass fiber reinforced composites)
• Metallic fasteners and hardware exposed to plasma cleaning or plasma activation processes

Types of Plasma Gas Environments We Simulate

• Fluorine‑based plasmas – Tetrafluoromethane (CF₄), sulfur hexafluoride (SF₆), nitrogen trifluoride (NF₃), hexafluoroethane (C₂F₆), trifluoromethane (CHF₃). These are highly aggressive, used for silicon etching and chamber cleaning. They produce atomic fluorine (F), CFₓ radicals, and HF as by‑products, attacking most metals and many ceramics.
• Chlorine‑based plasmas – Chlorine (Cl₂), boron trichloride (BCl₃), silicon tetrachloride (SiCl₄), hydrogen chloride (HCl). Common in aluminum and III‑V compound semiconductor etching. Chlorine plasmas cause severe pitting corrosion on aluminum and stainless steels, especially at elevated temperatures.
• Oxygen plasmas – Pure oxygen (O₂) or oxygen/argon mixtures. Used for ashing (photoresist removal), surface cleaning, and activation. Oxygen plasmas attack organic materials (polymers, photoresists) through oxidation, forming CO, CO₂, and H₂O. Metals may form oxide layers.
• Hydrogen plasmas – Hydrogen (H₂) or hydrogen/noble gas mixtures. Used for reduction, surface cleaning, and in some deposition processes. Hydrogen plasmas can cause hydrogen embrittlement in high‑strength steels and can reduce metal oxides, altering surface chemistry.
• Nitrogen plasmas – Nitrogen (N₂) or ammonia (NH₃) plasmas. Used for nitridation and surface modification. Can form metal nitrides on surfaces, which may be protective or brittle depending on the material.
• Mixed gas plasmas – For example, CF₄/O₂ (enhanced etch rates), Cl₂/BCl₃ (sidewall passivation), SF₆/O₂ (high etch rate silicon), Ar/CF₄ (physical + chemical etching).
• SF₆ decomposition products in switchgear – In high‑voltage circuit breakers, arcing decomposes SF₆ into lower fluorides (SF₄, S₂F₁₀, SOF₂, SO₂F₂, HF) which are corrosive to internal components, especially under the presence of moisture.

Plasma Exposure Test Methods

• Inductively coupled plasma (ICP) reactor exposure – We use a high‑density ICP source with independent control of RF power (up to 3000 W), substrate bias (up to 500 W), gas flow rates, process pressure (10 mTorr to 100 Torr), and substrate temperature (RT to 800°C). Samples are placed directly in the plasma zone. This method closely mimics semiconductor processing conditions.
• Reactive ion etching (RIE) mode exposure – Lower plasma density but higher ion energy (bias voltage up to 1000 V). Suitable for simulating the more energetic ion bombardment found in anisotropic etching processes. The combination of chemical attack and ion sputtering can produce unique damage morphologies.
• Downstream (remote) plasma exposure – The plasma is generated in a separate region, and only neutral reactive species (radicals) flow to the sample chamber. No direct ion bombardment. This isolates purely chemical corrosion mechanisms from physical sputtering. Used to evaluate corrosion by atomic fluorine, oxygen radicals, etc.
• Plasma jet exposure (atmospheric pressure plasma) – For larger components or when simulating plasma cleaning or activation processes operating at atmospheric pressure. The sample is exposed to a plasma jet generated by dielectric barrier discharge or microwave source. Conditions: gas flow (slpm), power, scanning speed, distance from nozzle.
• Corona discharge and partial arc exposure (for switchgear simulation) – A high‑voltage electrode system generates controlled corona or low‑energy arcs in SF₆ or SF₆/N₂ mixtures. Sample coupons are placed at defined distances from the discharge. Decomposition products are analyzed by gas chromatography. Corrosion products on the sample are characterized after exposure durations from 100 to 2000 hours.
• Controlled humidity post‑exposure – Many plasma corrosion mechanisms are accelerated by the presence of moisture. After plasma exposure (especially with fluorine or chlorine plasmas), samples may be exposed to controlled humidity air (50–90% RH at 20–50°C) for a period to simulate the conditions during venting and maintenance. This step can reveal delayed corrosion that would otherwise be missed.

Corrosion Assessment Methods

• Mass change measurement (gravimetric analysis) – Samples are cleaned, dried, and weighed on a microbalance (precision ±0.01 mg) before and after plasma exposure. Mass loss indicates etching or corrosion. Mass gain may indicate oxide or fluoride formation, polymer deposition, or particle adhesion. Results are expressed as mg/cm² or converted to an effective corrosion rate (µm/hour or nm/min).
• Surface morphology (scanning electron microscopy – SEM) – High‑resolution imaging (up to 100,000×) reveals pitting, cracking, delamination, grain boundary attack, surface roughening, nodule formation, and preferential etching of specific phases (e.g., carbide precipitates in stainless steels, secondary phases in alloys).
• Chemical composition of corrosion products (energy‑dispersive X‑ray spectroscopy – EDS and X‑ray photoelectron spectroscopy – XPS) – EDS provides elemental composition of surface layers (F, Cl, O, N, C, metals). XPS (surface sensitivity ~10 nm) identifies chemical bonding states (e.g., metal‑fluoride, metal‑oxide, metal‑chloride, metal‑nitride). This distinguishes between a passive fluoride layer that may be protective versus a thick, porous, non‑protective corrosion product.
• Cross‑sectional analysis (metallographic preparation and optical or SEM examination) – Samples are mounted in resin, polished to a mirror finish, and examined at high magnification. The thickness of the corrosion‑affected layer, depth of intergranular attack, and any subsurface cracking or void formation are measured. For coatings, remaining coating thickness and coating/substrate interface integrity are assessed.
• Surface roughness measurement (profilometry or atomic force microscopy – AFM) – Before/after roughness parameters (Ra, Rz, Rq) are measured over defined scan areas (10 µm × 10 µm up to 1 mm × 1 mm). An increase in roughness indicates non‑uniform corrosion. Roughness changes affect subsequent process performance (e.g., particle shedding, film adhesion, electrical breakdown strength).
• Microhardness change (Vickers or Knoop indentation) – Corrosion can alter the near‑surface hardness of metals (e.g., hydrogen embrittlement, phase transformation, selective leaching of alloying elements). We measure hardness before and after exposure on the same sample (using low‑load microindentation, e.g., 10 gf to 200 gf).
• Electrical resistance or resistivity change (for conductive components) – A four‑point probe measures surface resistivity before and after plasma exposure. An increase may indicate the formation of a non‑conductive corrosion layer. This test is critical for electrical contacts, grounding components, and RF feedthroughs.
• Optical transmittance change (for dielectric windows, viewports) – For quartz, sapphire, or ceramic windows exposed to plasma, we measure UV‑Vis‑NIR transmittance (200–2500 nm) before and after exposure. A decrease in transmittance indicates surface roughening, deposition, or corrosion.
• Leak rate change (helium leak detection) – For sealed components (e.g., hermetic feedthroughs, window assemblies) exposed to plasma, we perform helium leak testing before and after exposure using a mass spectrometer leak detector. An increase in leak rate indicates corrosion at seals or welds.

Mechanism Identification and Failure Analysis

• Intergranular corrosion assessment – After chemical etching, the depth of grain boundary penetration (in microns) is measured. Intergranular attack is common in stainless steels exposed to fluorine plasmas when chromium depletion occurs at grain boundaries (sensitization).
• Pitting corrosion characterization – Number of pits per unit area (pits/cm²), pit diameter, and pit depth (measured by confocal microscopy or by serial sectioning) are recorded. Pitting is characteristic of chlorine plasma corrosion on aluminum and stainless steels, especially in the presence of moisture or voltage bias.
• Stress corrosion cracking (SCC) evaluation (for components under residual or applied stress) – For mechanically loaded samples (bent beam, C‑ring, or tensile specimens) exposed to plasma, we examine for crack initiation and propagation. SCC is a risk for high‑strength alloys in chloride‑ or fluoride‑containing environments under tensile stress.
• Hydrogen embrittlement detection – After hydrogen plasma exposure, samples are subjected to a sustained load test or slow strain rate tensile test. Fracture surfaces are examined for intergranular or quasi‑cleavage features characteristic of hydrogen embrittlement. Hydrogen content is measured by inert gas fusion.
• Selective phase attack (metallography and electron microprobe analysis) – In multiphase alloys (e.g., duplex stainless steels, nickel‑based superalloys), certain phases may corrode preferentially. We identify the attacked phases by combined EDS mapping and electron backscatter diffraction (EBSD).
• Deposition analysis (when the sample gains mass) – Plasma corrosion is not always material loss; sometimes polymer‑like films or metal fluorides deposit from the plasma. We analyze deposited films by XPS, FTIR, or Raman spectroscopy to identify the composition (e.g., fluorocarbon polymers, metal‑organic compounds). Deposits can cause particle contamination, electrical leakage, or process drift.

Specialized Tests for Specific Applications

• Ceramic erosion in fluorine plasmas (Y₂O₃, Al₂O₃, AlN) – For ceramic chamber components, we measure erosion rate (nm/hour) as a function of plasma conditions (ion energy, fluorine radical density). Yttria is widely used as a protective coating because it reacts with fluorine to form YF₃, which is less volatile and more protective than the fluorides of aluminum. Erosion rate comparison helps select the optimal ceramic material.
• Polymer degradation in oxygen plasma (ashing rate) – For photoresists and organic coatings, we measure the ashing rate (µm/min) under controlled conditions (O₂ flow, power, pressure). The test provides quantitative data for process optimization.
• Gas compatibility of elastomer seals (mass change, hardness change, compression set) – Elastomer O‑rings (Viton, Kalrez, silicone, Buna‑N) are exposed to CF₄/O₂ plasma or to SF₆ decomposition products. After exposure, we measure change in mass, Shore A hardness, tensile properties, and compression set (ability to recover after compression). An acceptable seal typically exhibits less than 5% mass loss, hardness change within ±10 Shore A, and compression set below 30%.
• Corrosion of aluminum anodized coatings in chlorine plasmas – Anodized aluminum (Type II or Type III, with and without sealing) is exposed to Cl₂/BCl₃ plasma. We measure the time to breakthrough (when bare aluminum becomes exposed) and the extent of undercutting corrosion. Anodization quality (pore density, sealing effectiveness) directly affects plasma resistance.
• High‑voltage withstand test after plasma exposure (dielectric strength) – For insulating components (ceramic standoffs, polymer insulators) exposed to plasma, we perform dielectric testing (AC or DC, up to 100 kV) to verify that the insulation properties have not degraded. Breakdown voltage should remain within specification after exposure.

Reporting and Deliverables

Each plasma gas corrosion test report includes the following information:

• Sample identification (material type, dimensions, surface finish, pre‑cleaning treatment, supplier if known)
• Plasma exposure conditions: gas composition (including gas purity and flow rates), total pressure, RF power (source and bias), substrate temperature, exposure duration, plasma uniformity data if measured
• Post‑exposure handling: humidity exposure (if any), cleaning procedure before analysis
• Results of corrosion assessment: mass change (mg/cm² or %), SEM images at multiple magnifications, EDS spectra of surface regions, XPS analysis of chemical bonding states, cross‑sectional optical or SEM images with measured attack depth, surface roughness parameters (Ra, Rz) before and after, microhardness change, electrical resistance change (if measured), optical transmittance change (for windows)
• Interpretation: corrosion rate, damage mechanism (pitting, intergranular, uniform, selective phase, stress corrosion), likely cause based on comparison with known failure modes, estimated remaining useful life (if requested)
• Comparison with client‑supplied acceptance criteria (if provided)
• Raw data, calibration records of plasma system parameters, and instrument validation information are archived and available upon request

No statement of compliance with any external standard or regulation is made unless the client has provided specific acceptance criteria in writing. All raw data and retained samples are stored in our quality management system for a minimum of 10 years.