Particle Count Certification
Comprehensive particle count inspection and certification — laser surface scanning down to 0.09μm, full wafer defect maps, size distribution analysis, and SEMI M52/M53 compliant reporting in ISO Class 1 cleanroom.
Overview
Particle contamination on wafer surfaces is arguably the single largest cause of yield loss in semiconductor manufacturing. A single particle ≥ 50% of the minimum feature size can cause a killer defect — bridging adjacent lines, blocking an etch, or creating a void in a deposited film. As device dimensions shrink below 10nm, the critical particle size that constitutes a "killer defect" has decreased proportionally, now extending well below 0.1μm for advanced logic and memory devices.
GINECHIP's particle count certification service provides KLA-Tencor Surfscan-based inspection and certification of particle levels on bare and blanket-film wafers. With detection sensitivity down to 0.09μm PSL equivalent, full-wafer defect mapping, particle size distribution analysis, and comprehensive statistical reporting — our certification gives you the quantitative surface quality data needed to qualify incoming materials, verify cleaning process effectiveness, and monitor contamination trends across your wafer lifecycle.
Particle Inspection Services
Laser Surface Scanning (SP2/SP3/SP5)
KLA-Tencor Surfscan SP series unpatterned wafer inspection systems provide the industry-standard platform for particle and defect detection on bare and blanket-film wafers. The SP5 (current generation) achieves <strong>sensitivity down to 0.09μm polystyrene latex (PSL) equivalent</strong> on bare silicon with full-wafer scanning in under 60 seconds per 300mm wafer. Earlier SP2 and SP3 models provide 0.16μm and 0.12μm sensitivity respectively. The dark-field laser scattering principle detects particles by their scattered light signature while discriminating against surface roughness (haze) and subsurface defects.
Particle Size Distribution Analysis
Beyond total particle count, particle size distribution (PSD) analysis provides critical insight into contamination sources and process cleanliness. A wafer with 50 adds of 0.2μm particles may be acceptable, while 5 adds of 2.0μm particles may not — PSD separates these cases. Our PSD analysis reports particle counts binned by size: 0.2–0.5μm, 0.5–1.0μm, 1.0–2.0μm, 2.0–5.0μm, and > 5.0μm, with per-wafer and per-lot histograms.
Full Wafer Defect Maps
Every particle detection event is recorded with its x,y coordinate, enabling generation of <strong>full-wafer defect maps</strong> showing the spatial distribution of particles across the wafer surface. These maps are essential for contamination source identification: a radial pattern suggests spin-coater or spinner contamination; random distribution suggests airborne or cassette-originated contamination; edge-concentrated particles indicate edge chipping or handling damage; localized clusters may indicate point-source contamination from a specific process step.
Haze Measurement
Haze is the <strong>non-localized background scattering signal</strong> measured by the laser surface scanner, representing sub-resolution surface roughness, very small particles below the detection threshold, or thin surface contamination layers. Elevated haze indicates poor surface quality — from incomplete CMP clean, residual slurry, chemical residue, or microscopic pitting — even when individual particle counts appear acceptable. Haze is reported in parts per million (ppm) of the incident laser intensity and is trended alongside particle count for comprehensive surface quality monitoring.
Pre-and-Post Process Delta Analysis
The most actionable quality metric is not the absolute particle count, but the <strong>particle adders</strong> — the difference between post-process and pre-process particle counts. A pre-process baseline scan establishes the initial particle count. After your process (or our cleaning/polishing service), a second scan quantifies particles added. The delta (adders) directly measures process cleanliness. For our internal processes, standard acceptance criteria are ≤ 10 adders at 0.2μm and ≤ 5 adders at 0.5μm for the full process sequence.
Process Flow — Particle Count Certification
入荷検査とコンディション確認
Class 1 クリーンルーム環境でのウエハ受入。目視検査により、著しい汚染、取扱いによる損傷、または目に見える欠陥の有無を確認する。レーザスクライブのID検証を実施。LIMSに一意なロットおよびウエハIDを登録し、完全な計測トレーサビリティを確保する。カセット間での搬送—ウエハへの手動による接触は行わない。
プリスキャン（ベースライン測定）
初期のレーザ表面スキャンで、入荷粒子のベースラインを確立する。指定した感度閾値（0.09–0.16μm：SPモデルおよびウエハ表面タイプに依存）で、全面ウエハスキャンを実施。粒子数、サイズ分布、および欠陥マップを記録する。このスキャンは、洗浄／研磨が行われる場合の加算計算の参照として用いられる。
欠陥分類
自動欠陥分類（ADC）では、粒子を他の欠陥タイプから分離します：傷（線状の特徴）、スリップライン（結晶学的欠陥）、ピット（表面の空隙）、およびスタッキングフォルト（結晶欠陥）です。分類は、散乱光の強度、偏光、空間的特徴に基づいて行われます。分類された画像のうち曖昧な欠陥は目視で再確認します。
ヘイズ解析
ウェーハ全面にわたるヘイズを定量化する。平均ヘイズ値とヘイズ均一性（平均に対する標準偏差の％）を算出する。ヘイズマップを生成する。さらに、ヘイズと粒子数の相関解析を行い、潜在的な根本原因を特定する（例：ヘイズが高いのに粒子数が低い場合、粒子由来の汚染ではなくCMP残渣を示唆する）。
統計データ集計
すべての粒子データを集約し、ウェーハごとおよびロットごとの統計サマリーを作成する。適用可能な場合、粒子アダー（post-preスキャン比較）を算出する。ウェーハソースに対してSPCトレンドを実施し、過去データと比較する。管理限界を超えるロット（通常、平均値＋3σ）では、失降下アクションプランを起動する。
レポートと認証
粒子計数証明書を作成する。内容には以下を含む：ウェーハID、スキャンパラメータ（装置、感度、スキャン面積）、各サイズビンの総粒子数、particle adders（該当する場合）、欠陥マップ、ヘイズデータ、ならびに顧客仕様に基づく合否判定。ウェーハは乾燥剤を備えたクラス1のクリーンルーム対応カセットにて真空シールする。
Quality Specifications — Inspection System
| Parameter | Target Specification | Measurement Method |
|---|---|---|
| Minimum Detectable Particle | ≥ 0.09μm PSL (SP5) | PSL deposition standard wafer |
| Particle Count Accuracy | ± 10% (k=2) for ≥ 0.2μm | NIST-traceable PSL deposition standards |
| Scan Coverage | Full wafer minus edge exclusion | Edge exclusion: 3mm default, configurable |
| False Count Rate | < 1 false count per scan | Clean reference wafer, 10 scans |
| Haze Measurement Range | 0.05–500 ppm | Calibrated haze standards |
| Coordinate Accuracy | ± 50μm in X and Y | Laser-interferometer stage calibration |
| Throughput (300mm) | ≤ 60 seconds per wafer (SP5) | Cycle time measurement |
| Cleanroom Class | ISO Class 1 (ISO 14644-1) | Continuous particle monitoring |
All specifications based on KLA-Tencor SP5 system performance on bare silicon (100) wafers. Specifications for other surfaces (oxide, nitride, metal films, SOI) may differ due to increased background scattering. Contact us for film-specific capabilities. System calibration verified daily with NIST-traceable PSL deposition standards.
Dark-Field Laser Scanning — How It Works
The KLA-Tencor Surfscan system operates on the principle of dark-field laser scattering. A focused laser beam (typically 488nm argon-ion or 355nm UV, depending on model) is scanned across the wafer surface in a spiral pattern (r-θ scan). When the laser spot encounters a particle, the particle scatters light in all directions. Detectors positioned at oblique angles (outside the specular reflection path — hence "dark field") collect this scattered light. The scattered intensity correlates with particle size (larger particles scatter more light). Sophisticated signal processing algorithms discriminate true particle scattering from background noise caused by surface roughness (haze), film grain, and sub-surface defects. The system records the x,y location and scattered light intensity for each detected event, enabling generation of wafer maps and size distribution histograms.
Defect Classification — Beyond Particle Counting
Not everything that scatters light is a particle. The Surfscan system includes Automatic Defect Classification (ADC) capabilities that distinguish between different defect types based on their scattering signatures:
Particles
Discrete scattering events with well-defined, approximately Gaussian intensity profiles. Particles can be spherical (atmospheric dust, dried slurry residue), irregular (silicon fragments from edge chipping), or aggregated. Particles are typically the primary target of certification. Post-cleaning particle counts below 10 adders at 0.2μm are considered excellent for most applications; sub-5 adders is achievable with optimized cleaning protocols.
Scratches & Other Defects
Scratches appear as linear features with extended scattering profiles — recognized by ADC through their elongated spatial signature. Crystal defects (slip lines, stacking faults) produce characteristic linear patterns aligned with crystallographic directions and are distinguished from scratches by their straight, crystallographically oriented geometry. Pits (surface voids) appear as negative-contrast scattering events. Residue/stains produce diffuse scattering with low peak intensity. All defect types are reported alongside particle data to provide a complete surface quality assessment.
Particle Size Distribution & SPC Trending
The particle size distribution (PSD) provides significantly more diagnostic value than a single total particle count number. Consider two wafers, each with 50 total particle adds at 0.2μm. Wafer A shows 48 particles in the 0.2–0.5μm bin and 2 particles in the 0.5–1.0μm bin. Wafer B shows 35 particles in the 0.2–0.5μm bin, 12 in the 0.5–1.0μm bin, and 3 in the > 1.0μm bin. Wafer B represents a more severe contamination problem because larger particles have a proportionally larger "kill ratio" for device defects. PSD analysis enables process engineers to set size-bin-specific limits (e.g., ≤ 50 adds at 0.2μm, ≤ 10 adds at 0.5μm, ≤ 2 adds at 1.0μm) that more accurately reflect device-killing risk than a single total-count specification.
Edge Exclusion Zone Configuration
Particle count certification supports configurable edge exclusion zones — a radial band at the wafer perimeter where particles are excluded from the count because they fall outside the usable die area. Standard edge exclusion is 3mm for 200mm and 300mm wafers, but can be set to 1mm, 2mm, 5mm, or any customer-specified value. This is critical because particle counts in the extreme edge region (< 3mm from edge) are often 3–10× higher than in the central region due to edge handling and contact with cassette slots — and these edge particles may or may not be relevant depending on whether the customer uses that edge region for device fabrication.
SEMI M52/M53 Compliance
Our particle count certification reports are compliant with SEMI M52 (Guide for Specifying Scanning Surface Inspection Systems for Unpatterned Wafers) and SEMI M53 (Practice for Calibrating Scanning Surface Inspection Systems Using Deposited Polystyrene Latex Spheres on Unpatterned Semiconductor Wafers). This ensures that our particle count data is directly comparable with data from your in-house Surfscan systems and with your wafer supplier's particle certification — eliminating the "our scanner vs. your scanner" calibration discrepancies that can lead to false accept/reject decisions.
Class 1 Cleanroom Handling
All particle count certification is performed in an ISO Class 1 (ISO 14644-1) cleanroom environment — the most stringent level of cleanroom classification. In a Class 1 environment, the maximum allowable particle concentration is 10 particles per cubic meter at ≥ 0.1μm and 2 particles per cubic meter at ≥ 0.2μm. This ensures that the particles we measure originated from your wafer or process, not from our inspection environment. Cassette-to-cassette automated handling eliminates human contact with wafers. Wafer cassettes are stored in sealed containers with continuous dry N₂ purge when not actively being processed. All personnel wear full Class 1-compatible cleanroom garments (bunny suit, hood, booties, face mask, double gloves) and follow strict cleanroom protocols.