Mask Data Preparation (MDP) converts the final chip design layout (GDS/OASIS) into mask-ready format for photomask manufacturing. It is the last step before the design leaves the fab and enters the mask shop.

MDP Steps

Step 1 - Fracturing: Break complex polygons into simple rectangles and trapezoids that the mask writer (e-beam or laser) can expose. Output format: MEBES, VSB, or JEOL for e-beam writers. Step 2 - OPC Application: Add Optical Proximity Correction features (serifs, scattering bars, line biasing) to compensate for lithographic distortion. Step 3 - Job Deck Creation: Define reticle layout—how the die is arrayed, alignment marks, barcodes, and process control monitors placed in the frame area. Step 4 - Tone Assignment: Define which areas are chrome (dark) and clear for each layer. Step 5 - MRC (Mask Rule Check): Verify the fractured data meets mask manufacturing constraints (minimum feature size, minimum space for the mask writer).

Data Volumes

Advanced-node masks generate enormous data: 1-10 TB of fractured data per mask layer after OPC. A full mask set (60-80 layers) can be 100+ TB of data. Data compression and hierarchical representation are essential.

Key Considerations

Write time: Complex OPC patterns increase e-beam write time (1-10 hours per mask at advanced nodes). Curvilinear masks: Next-generation OPC uses curved shapes for better lithographic fidelity, but requires new fracturing algorithms. Multi-beam writers: IMS/NuFlare multi-beam tools dramatically reduce write time for complex patterns. MDP tools: Synopsys CATS, Siemens Calibre MDP, Cadence Pegasus MDP.