nand process flow

# NAND Process Flow

A NAND process flow connects array-stack construction, deep-feature etching, memory-film formation and electrical connection. This entry uses a simplified replacement-gate charge-trap example.

## Build and pattern

Repeated films create the array height. Channel-hole etching connects many intended memory levels along a vertical opening. Staircase and access structures serve different purposes and require their own patterning operations.

## Form the cell

Memory dielectrics and a semiconductor channel are formed in the opening. Their exact sequence and implementation depend on the integration. In replacement-gate schemes, sacrificial layers are removed and gate structures are completed through suitable access paths.

## Connect the array

Word-line contacts, channel connections and interconnect connect the cells to their peripheral circuits. Peripheral circuits may be integrated using different layouts or bonding approaches; they are not described by a single universal sequence.

## Test what fabrication produced

Electrical tests assess programming, reading and erasing as well as defects and variability. A deep hole reaching its intended depth does not by itself establish a working flash string.

## Further reading

[Manufacturer technical overview](https://www.micron.com/products/storage/nand-flash/176-layer-nand). The illustration is original and schematic; dimensions, layer counts and materials are illustrative rather than a vendor recipe.