What is ALD?

Atomic Layer Deposition (ALD) is a thin-film deposition technique used in the fabrication of semiconductor devices, microelectronics, and various nanotechnology applications. It allows for precise control over the thickness and composition of thin films at the atomic level.

In ALD, thin films are grown by sequentially exposing a substrate surface to alternating precursor gases or vapors in a controlled vacuum environment. Each precursor gas reacts with the substrate surface in a self-limiting manner, forming a monolayer of material. This self-limiting reaction ensures precise control over the thickness of the deposited film. After each precursor exposure, the excess precursor and reaction byproducts are purged from the chamber before introducing the next precursor, preventing unwanted reactions and ensuring the purity of the deposited film.

The process typically involves four main steps:

1. = Purge: The substrate is exposed to an inert gas, such as nitrogen, to remove any contaminants or residual gases from the chamber.
2. Precursor A exposure: The substrate is exposed to the first precursor gas, which reacts with the substrate surface, forming a monolayer of material.
3. Purge: Any excess precursor and reaction byproducts are purged from the chamber.
4. Precursor B exposure: The substrate is then exposed to the second precursor gas, which reacts with the surface, forming another monolayer. This cycle of alternating precursor exposures is repeated until the desired film thickness is achieved.

ALD offers several advantages over other thin-film deposition techniques, including precise thickness control at the atomic level, uniformity across complex substrate geometries, excellent conformality even in high aspect ratio structures, and the ability to deposit a wide range of materials, including oxides, nitrides, metals, and semiconductors.