MLM – Multi Layer Mask

MLM (Multi Layer Mask) or MLR (Multi Layer Reticle) services help reduce the tapeout NRE cost (full maskset cost). This method allows combining up to 4 masks into one, and hence reducing the total number of masks that need to be created. As the number of masks is reduces — the NRE reduced as well.

What is the catch with MLM? The drawback is the wafer price. While the NRE price decreases — the wafer price increases. Therefore MLM is recommended for projects that require low or medium production volume.

You can think of MLM as a financial service. You pay lower NRE (vs. full maskset), but on the other hand, you pay a higher wafer price. If you know your production projection it’s very easy to calculate whether to use MLR or Full Maskset. The decision here is pure economic.

Foundries do not like MLM. It slows down their production throughput. Therefore – ask you fab if they support MLM.