Lithography Masks (Photomasks)
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Overview
The photomask is the fundamental pattern carrier in every photolithography process — its quality directly determines the fidelity of every feature on your wafer. A single defect on a 1× contact mask replicates across every exposure field and every wafer, making mask quality one of the highest-leverage investments in the entire semiconductor fabrication flow. GINECHIP provides custom photomask fabrication services spanning chrome-on-glass, emulsion, and phase-shift mask technologies for R&D, pilot production, and low-to-mid volume manufacturing.
Our mask fabrication partners utilize industry-standard laser writers (Heidelberg DWL series), e-beam writers for submicron features, and automated defect inspection systems (KLA-Tencor) to deliver masks with verified CD uniformity, overlay registration, and defect density. Whether you need a single mask for a university MEMS project or a full reticle set for a compound semiconductor process, we provide competitive pricing, fast turnaround, and full metrology data with every mask shipment.
Photomask Technology Comparison
Chrome-on-Glass (COG)
The workhorse of semiconductor lithography. A thin chromium layer (~100nm) deposited on a precision glass or quartz substrate, patterned by laser or e-beam lithography. COG masks offer the best combination of resolution, durability, and optical density for repeated use in production environments.
- Minimum feature: ≥ 0.5μm (laser), ≥ 0.1μm (e-beam)
- Optical density: OD ≥ 3.0 at 365–436nm
- Durable — withstands contact printing and repeated cleaning
- AR (anti-reflective) chrome option for reduced back-reflection
Emulsion (Silver Halide)
Cost-effective photomasks using photographic emulsion on glass. Ideal for R&D prototyping, university labs, and applications where feature sizes above 2μm are acceptable. Fast turnaround and the lowest cost per mask of all technologies.
- Minimum feature: ≥ 2μm
- 24–48 hour express turnaround available
- Ideal for MEMS, microfluidics, and thick photoresist processes
- Not recommended for contact printing (emulsion wears with contact)
Phase-Shift Mask (PSM)
Advanced photomasks that modulate the phase as well as the amplitude of transmitted light. By engineering constructive/destructive interference at feature edges, PSMs improve resolution and depth of focus beyond the Rayleigh limit of conventional binary masks.
- Attenuated PSM (halftone): MoSi or Cr-based attenuator
- Alternating PSM: etched quartz trenches for π phase shift
- Minimum feature: ≥ 0.3μm (laser-written attenuated PSM)
- Improved process window for critical layers
Iron Oxide & Aluminum
Transparent-conductive oxide (iron oxide) or reflective metal (aluminum) masks for specialized applications. Iron oxide masks are partially transparent for alignment viewing through the mask. Aluminum masks for UV-NIL (nanoimprint) and reflective lithography setups.
- Iron oxide: OD 1.5–2.5, visible-light transparent for alignment
- Aluminum: high reflectivity for DUV and NIL applications
- Custom thin-film stacks available for specific wavelengths
- Bonded substrates for backside alignment applications
Technical Specifications
| Parameter | Available Range / Values |
|---|---|
| Mask Type | Chrome-on-glass (COG), Emulsion (silver halide), Phase-shift (PSM), Iron oxide, Aluminum-coated |
| Substrate Material | Soda-lime glass, Synthetic quartz (fused silica), Low-expansion glass (LE-30), Calcium fluoride (CaF₂) |
| Plate Size | 3″×3″ (76×76mm), 4″×4″ (102×102mm), 5″×5″ (127×127mm), 6″×6″ (152×152mm), 7″×7″ (178×178mm) |
| Plate Thickness | 0.060″ (1.5mm), 0.090″ (2.3mm), 0.120″ (3.0mm), 0.250″ (6.35mm) — per SEMI P1 |
| Minimum Feature Size | COG: ≥ 0.5μm; Emulsion: ≥ 2μm; Phase-shift: ≥ 0.3μm; Custom e-beam: ≥ 0.1μm |
| Field / Polarity | Dark field (clear features on dark background), Clear field (dark features on clear background) |
| Tone | Positive tone, Negative tone — matched to photoresist polarity |
| CD Uniformity | COG: ±0.1μm (global), ±0.05μm (local); Emulsion: ±0.5μm |
| Registration | COG: ±0.25μm overlay; Emulsion: ±1.0μm overlay; first-level to second-level alignment marks |
| Pellicle | Optional pellicle membrane: nitrocellulose, fluoropolymer; AR-coated frame; mounted or unmounted |
| Edge Quality | Ground and polished edges, chamfered; laser-engraved or etched barcode and fiducial marks |
Mask Design Guidelines & Data Formats
Accepted Design Formats
- GDSII (.gds, .gds2) — Industry standard; all hierarchy levels, any number of layers
- OASIS (.oas) — Compressed format; recommended for large multi-layer designs above 10GB
- DXF (.dxf) — AutoCAD format; suitable for simple, single-layer designs
- CIF (.cif) — Caltech Intermediate Format; legacy format, still supported
- Gerber (.gbr) — For PCB-style mask designs
Design Rule Checks (DRC)
- Minimum Feature / Gap — We verify all features meet or exceed the minimum resolvable size for your chosen mask technology
- Data Density — Verification of pattern density against mask writer write-time and cost estimates
- Tone & Polarity — Confirmation that dark/clear assignment matches your photoresist polarity (positive/negative)
- Alignment Marks — We can add standard crosshair, vernier, or box-in-box alignment marks per your specification
Lithography Mode Compatibility
Contact Lithography
Mask in direct physical contact with photoresist-coated wafer. 1× transfer, highest resolution for a given NA. Requires durable masks (COG recommended). Risk of mask contamination and defect generation with each contact cycle. Suitable for R&D and low-volume MEMS production.
Proximity Lithography
Mask separated from wafer by 10–50μm gap. Eliminates contact contamination but diffraction-limited resolution (≥ 2–3μm typical). Emulsion or COG masks acceptable. Common in MEMS, LED, and microfluidics fabrication where submicron resolution is not required.
Projection Lithography
Mask imaged onto wafer through reduction optics (typically 4× or 5× reduction). Requires reticle-scale masks (5″ or 6″ plates for steppers). Demanding registration and CD uniformity specs. COG or PSM technology required. Pellicle strongly recommended.
Applications
Quality & Certification
Every photomask undergoes automated optical inspection (AOI) for defect detection, CD-SEM metrology for critical dimension verification, and overlay registration measurement. Inspection reports including defect map, CD uniformity plot, and registration vector map are provided with each mask shipment. All masks are cleaned, inspected, and packaged in a Class 1 (ISO 3) cleanroom environment with pellicle mounting available as an option. ISO 9001:2015 certified quality management throughout.
Need Custom Photomasks for Your Process?
Send us your GDSII or DXF file, specify your preferred mask technology and plate size, and our mask engineering team will provide a quotation with estimated turnaround time within 24 hours.