mask data preparation

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.