Overview
Wafer geometry — total thickness variation (TTV), bow, and warp — directly impacts lithography focus budget, chucking uniformity, and downstream bonding yield. GINECHIP's metrology lab uses capacitive gauging and interferometric scanning to characterize these parameters across the full wafer surface, from 100mm to 300mm diameters.
Every measurement report includes site-by-site TTV maps, bow and warp values per SEMI M1 and M58 methodology, with NIST-traceable calibration standards. Data is delivered in industry-standard formats compatible with fab MES systems.
Measurement Services
TTV Measurement
Total Thickness Variation (TTV) is quantified via multi-point capacitive gauging across the full wafer surface, reported as the difference between maximum and minimum thickness readings.
Bow Measurement
Free-state bow is measured by optical profilometry — the deviation of the wafer's median surface from a reference plane at its center point, reported as positive (convex) or negative (concave).
Warp Measurement
Free-state warp is measured against a best-fit reference plane, capturing the peak-to-valley deviation across the entire median surface of the wafer.
Flatness vs. Shape Analysis
Chucked flatness (thickness-variation based) and free-state shape (curvature based) are measured independently and reported together — both metrics are required to fully characterize wafers for lithography and thin-wafer handling.
Process Flow
Wafer Receipt & ID
Incoming wafers are logged with lot and wafer ID, visually inspected for handling damage, and routed to the metrology lab via cassette-to-cassette transfer.
Environmental Stabilization
Wafers stabilize in the measurement chamber at 23 ± 0.5°C and 45 ± 5% RH before scanning, eliminating thermal drift from thickness and shape readings.
TTV Capacitive Scan
A multi-point capacitive gauge scans the full wafer at ≥ 2,500 points per 300mm wafer, generating a dense thickness map with NIST-traceable calibration.
Bow/Warp Optical Scan
The wafer is measured in free state via optical profilometry to capture bow and warp against a best-fit reference plane, without chucking-induced distortion.
Statistical Compilation
TTV, bow, and warp results are compiled per wafer and per lot, with SPC trending against historical data and pass/fail flags against customer specification limits.
Report & Certification
A geometry measurement certificate is issued with wafer ID, scan parameters, TTV/bow/warp values, and pass/fail determination, exported as PDF and CSV/SPC data.
Quality Specifications
| Parameter | Target Specification | Measurement Method |
|---|---|---|
| TTV Accuracy | ± 0.2μm (k=2) | NIST-traceable thickness standards |
| TTV Repeatability | ± 0.1μm (3σ) | Repeat measurements (30 cycles) |
| Bow Measurement Accuracy | ± 1.0μm (k=2) | NIST-traceable optical flat reference |
| Warp Measurement Accuracy | ± 1.5μm (k=2) | NIST-traceable optical flat reference |
| Bow/Warp Repeatability | ± 0.5μm (3σ) | Repeat measurements on standard wafer |
| Measurement Speed (300mm) | TTV: 30 sec; Bow/Warp: 60 sec | Cycle time measurement |
| Environmental Control | 23 ± 0.5°C; 45 ± 5% RH | NIST-traceable sensors, continuous log |
| Data Export Format | CSV, PDF report, SPC data package | LIMS data export module |
Values above are typical for standard measurement processes. Custom tolerances available upon request.
Measurement Methods
Capacitive Gauging
Capacitive thickness measurement provides non-contact, high-speed TTV (Total Thickness Variation) characterization with resolution down to 0.1μm. Our multi-point capacitive gauging systems map the entire wafer surface for comprehensive thickness profiling.
Optical Profilometry
White light interferometry and confocal microscopy provide nanometer-resolution surface topography measurement for critical applications. These techniques characterize surface roughness, step heights, and local surface features with sub-nanometer vertical resolution.
Shape vs. Flatness
While flatness (TTV, STIR, SFQR) measures the thickness variation across the wafer, shape parameters (Bow, Warp) characterize the 3D deformation of the wafer independent of thickness. Understanding both is critical for lithography depth-of-focus budgets and wafer handling.
Thin Wafer Measurement
Ultra-thin wafers below 200μm present unique metrology challenges due to gravitational sag and handling-induced deformation. We use specialized support fixtures and gravity-compensated measurement algorithms to achieve accurate measurements on thin and ultra-thin substrates.
Data Output & Reporting
Every measurement lot includes comprehensive digital deliverables for your quality records and SPC systems.
PDF Reports
Each measurement lot is accompanied by a comprehensive PDF report including wafer maps, statistical summaries, pass/fail classification, and trend charts. Reports include traceability information linking each wafer to its unique ID, measurement date, and operator.
CSV Data Export
All measurement data is available in industry-standard CSV format for direct import into your SPC software. Data includes raw measurement points, calculated statistics, and pass/fail classification per your specified limits.
Applications
Incoming QC Integration
Our measurement data integrates directly into your incoming quality control workflow, with pass/fail flags and lot disposition recommendations based on your specified acceptance criteria.
Quality Assurance
Our metrology laboratory maintains ISO 17025 accreditation with NIST-traceable reference standards. All measurement equipment undergoes daily calibration verification with certified reference wafers, and our measurement uncertainty is documented for each parameter type.
Ready to Get Started?
Contact our engineering team to discuss your specific requirements and receive a detailed quotation within 24 hours.