Definition
A mask set is the complete group of photomasks required to manufacture a particular chip. Each photomask, also called a reticle, is a precision quartz plate carrying the patterned image of one layer of the design. A modern integrated circuit is built from dozens of stacked layers, so its mask set may contain many individual masks. The set is produced by the foundry directly from the tape-out files.
How masks are used
During fabrication, a photolithography scanner projects the image on each mask onto the wafer, exposing the photoresist to define that layer's features. The mask is reused to print the same pattern across every die on the wafer and across thousands of wafers, which is what makes high-volume chip manufacturing economical.
The cost of a mask set
Mask sets for advanced nodes are extraordinarily expensive, running into the millions of dollars, because each plate must be written with electron-beam precision and inspected for the slightest flaw. This fixed, one-time cost is a major reason new chip designs only make sense at high volume, and it is the financial weight behind every ASIC tape-out. A flaw discovered after the masks are made forces a costly re-spin.
The mask set is generated immediately after tape-out and is the tooling that photolithography uses to pattern each wafer.
In Simple Terms
A mask set is the complete group of photomasks required to manufacture a particular chip. Each photomask, also called a reticle, is a precision quartz…