Metal Liner Prime Etch for Uniform 3D NAND Memory Holes

The etching process is segmented into multiple sequential steps: wet etching for rapid material removal, followed by dry etching for precise trench penetration. This segmentation allows each method to perform its optimal function without the drawbacks of using either method alone for the entire process.

A plasma activation step is introduced as an intermediary between wet and dry etching. The plasma treatment modifies the trench surface to enable subsequent dry etching penetration, acting as a mediator that bridges the gap between the two etching methods and allows the dry etch to effectively follow the wet etch into constrained features.

The harmful electric arc component is extracted or removed from the plasma process by using a remote plasma source instead of direct contact plasma. The reactive species are generated remotely and then delivered to the substrate without the damaging ion bombardment and arc formation that occur with local plasma discharge.

The mechanical/physical plasma discharge method is replaced with a chemical vapor deposition-style remote plasma approach. Instead of using ion bombardment to drive the etching, the process uses chemically reactive species delivered through a remote plasma source, substituting a chemical mechanism for a physical one to avoid substrate damage.

The wet etching step is performed as a preliminary action before dry etching. This preliminary wet etch removes the majority of the material and creates initial trench access, which then enables the subsequent dry etch to proceed uniformly to the bottom of high aspect-ratio features without suffering from loading imbalances.

The etching process uses periodic alternation between wet and dry etching steps. This periodic action allows the process to switch between the high-speed bulk removal of wet etching and the precise, uniform penetration of dry etching, achieving both speed and uniformity in high aspect-ratio feature fabrication.