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High-Aspect-Ratio (HAR) Etching

High-aspect-ratio (HAR) etching is a microfabrication technique used to create structures with a high height-to-width ratio (at 100:1). Control of the plasma ions is critical during the etching process to prevent defects in the features.

In 3D NAND flash memory manufacturing, HAR etching is a key process used to create a device structure with trenches and holes having the desired aspect ratio. The primary structure is created by alternating film depositions, then completing a high aspect ratio etch through the entire stack. This process has unique control requirements since the channels are on the order of microns deep with angstrom-level requirements for precision.

The massive quantity of data needed for AI training requires high levels of parallel processing, abundant non-volatile memory, and fast data transfer rates. Advanced devices rely on architectures that are fabricated in three dimensions and etch is a powerful tool in shaping them. Gate-all-around (GAA) transistors, 3D NAND memory with low cost-per bit, and high bandwidth memory are integral to AI’s future and all need new, novel etch approaches to sculpt their device structures. They demand not only unprecedented etch precision, but also the ability to selectively remove one material while leaving another in place, modify surface characteristics of the remaining materials, etch structures with ever-higher aspect ratios, and sometimes even etch laterally rather than only vertically.