MRC (Mask Rule Check) is the verification that OPC/ILT-corrected mask patterns are physically manufacturable by the mask shop — checking that mask features satisfy minimum feature size, minimum spacing, maximum jog angle, and other constraints imposed by the mask writing and inspection tools.

MRC Rules

• Minimum Feature Size: Mask features must be large enough for the mask writer to resolve — typically >40-60nm on mask (4× reduction = >10-15nm on wafer).
• Minimum Space: Minimum gap between mask features — constrained by mask etch resolution.
• Maximum Jog Width: The width of jogs (steps in edge position) must be large enough to be written reliably.
• Corner Rounding: Sharp corners are rounded during mask writing — MRC defines minimum radius.

Why It Matters

• Manufacturability: OPC/ILT can create features that look great in simulation but cannot be fabricated on the mask.
• Feedback Loop: MRC violations require OPC/ILT re-run with tighter constraints — iterate until MRC-clean.
• Cost/Yield: MRC violations that reach the mask cause mask defects — expensive rework ($100K-$500K per mask).

MRC is can the mask shop actually make this? — verifying that OPC-corrected designs are physically manufacturable within mask fabrication constraints.