Atomic Layer Deposition
Films grown by Atomic Layer Deposition span a wide breadth of functions. Learn about about the top applications of ALD and which industries Beneq is using them in.
It is nearly impossible to spend a day without interacting with something that has been made with Atomic Layer Deposition. Perhaps you took a photo on your phone, or browsed the internet on your laptop. Maybe you passed by a solar farm or put on your favorite silver earrings. ALD is the invisible and inconspicuous method that manufacturers from electronics to space telescopes are using to either fabricate or improve their products. But what do these ALD films actually do? Below you will find some of the most important applications of ALD and where Beneq is putting them to use.
One of the most widespread and well-known ALD applications is as a high-k dielectric in semiconductor device fabrication. As the miniaturization of transistors began, gate dielectrics, the material layer responsible for insulating the active material from the electrode, also needed to reduce in size. Since capacitance is inversely proportional to dielectric thickness, the thinner the layer gets, the less effective as an insulator it becomes and traditional SiO2 dielectric layers below 2 nm were subject to increased electron tunneling. Materials with high dielectric constants (k), like Al2O3 and HfO2, therefore became necessary to compensate for the reduced capacitance and ALD emerged as the enabling technology for fabricating these layers. The precision thickness control of ALD made it ideal for depositing high-quality films on very tiny scales. Thin films with high dielectric constants were able to achieve effective limitation of electron tunneling as devices continued to scale down. ALD is still the technology used for depositing gate dielectrics and other high-k coatings.
Antireflective Coating (ARC)
Antireflective coatings, also known as ARCs, are common optical coatings used to reduce the reflection of light on lenses, glass and other optical components. They are fabricated with alternating layers of high and low index materials which causes light reflecting from interfaces to destructively interfere. ARCs are used for multiple purposes, including the elimination of reflection itself in eyeglasses, but also to improve imaging quality by reducing stray light, such as those used in camera lenses, space telescopes and LiDAR sensors. Emerging optics, like those used in guided AR/VR headsets, require extremely uniform coatings on complicated, nanostructured components. While ARC fabrication is a more recent ALD application, it has gained attention due to its simplicity in creating precise, laminated structures of multiple materials, and for its conformality ensuring excellent uniformity of optical properties across the entire substrate.
Moisture Barriers & Encapsulation
Numerous devices have an interface with harsh environmental conditions that have the potential to damage sensitive electronics and other components. Films grown by atomic layer deposition are dense and pinhole-free which makes them excellent candidates as barriers from corrosive moisture and gases. Since the number of defects in ALD films are very low, vapor transmission rates are orders of magnitude smaller than with conventional approaches, and achieved with a fraction of the thickness. Additionally, the extreme conformality of the resulting barrier ensures a complete encapsulation of even complicated device architectures.
This ALD application is another important example in semiconductor device manufacturing. Several device markets utilize active materials which are subject to performance degradation due to defect states. Oftentimes, these are the result of unstable oxides forming at their surfaces from unintended oxygen diffusion via subsequent depositions. Using ALD, device manufacturers can deposit highly conformal films on complicated and high aspect ratio active materials to both prevent future oxidation and promote better interfacial contact with subsequent layers. Conventional methods typically lack the necessary conformality for effective passivation.
Films grown by atomic layer deposition can generally be used as barriers to protect components from various chemical processes that may impact device performance. For example, nitrides are often deposited with ALD to be used as spacers in transistors to prevent contamination of copper interconnects. In lithium-ion batteries, electrodes coated with ALD can help protect the active material from degradation and dendritic shorting. Material versatility, purity and film robustness has allowed the application of ALD for barrier films in several areas.