ALD (atomic layer deposition) is a vapor phase procedure for depositing thin films on a substrate. ALD involves exposing the Surface of a substrate to alternating precursors that do not overlap but are introduced sequentially. ALD precursors not only provide excellent thickness control and uniformity but can also cover 3D structures with a conformal coating for high-aspect-ratio structures.
ALD precursors are based on self-limiting surface reactions and typically produce very low pin-hole and particle levels, which can benefit many applications. Many applications require the level of film and interface control and high film quality provided. The use of plasma allows for improved film properties, control, and a diverse range of materials. The adaptability of unique surface pretreatments enables low-damage processing.
Advantages of ALD
ALD precursors have several advantages, all of which stem from self-limiting, and sequential reactions. First, while deposition is not exactly one atomic layer per cycle, the film thickness is well controlled, and excellent uniformity across the wafer can be achieved. Perhaps more importantly, ALD produces layers that conform to the wafer topography extremely well, with identical film thicknesses deposited on the tops, sides, and bottoms of device features. This high conformality is essential for high-aspect ratios and three-dimensional structures. Finally, ALD surfaces are atomically smooth and have a well-controlled chemical composition.
How Atomic Layer Deposition((ALD) Precursors works
The ALD process begins by flooding the reaction chamber with a precursor that coats (or “adsorbs”) onto the wafer’s exposed Surface. This process is referred to as self-limiting because the precursor can only adsorb onto exposed areas; once those are covered, adsorption ceases. After that, a second gas is introduced and reacts with the precursor to produce the desired material. This second step is also self-limiting: when the available precursor sites are depleted, the reaction comes to a halt. The first and second steps are repeated until the desired film thickness is achieved.
These precursors are based on Surface controlled thin film deposition. Two or more chemical condensation or gaseous precursors react sequentially on the substrate surface during coating, producing a solid thin film.
Most ALD coating systems use a flow-through traveling wave setup, in which an inert carrier gas runs through the system, and precursors are injected as very short pulses into the carrier flow. The precursor pulses are carried as sequential “waves” through the reaction chamber by the carrier gas flow, which is then followed by a pumping line, filtering systems, and, finally, a vacuum pump.
The precursor molecule reacts with the Surface in a self-limiting manner in each alternate pulse, ensuring that the reaction stops once all of the reactive sites on the substrate have been used.
The nature of the precursor-surface interaction determines the complete ALD cycle. Depending on the requirements, the ALD cycle can be repeated multiple times to increase the layers of the thin film. ALD is frequently performed at lower temperatures, which is advantageous when working with fragile substrates. They can deposit a wide variety of materials, including oxides, metals, sulfides, and fluorides, and a wide range of materials are available.
Conclusion
ALD precursors are gaining traction in the biomedical industry, particularly with the increased use of nanoporous materials in drug delivery, tissue engineering, and implants. We have created a one-of-a-kind, commercially viable atomic layer deposition process for creating precision on particles. We take pride in assisting our customers in utilizing technology to improve their products and services. Please make contact with us if you need ALD precursor manufacturing.
Optima Chemical 