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EnglishWhat is Thin Film Deposition?
Thin film deposition is the process of building up material on a substrate ranging from a few nanometers to about 100 microns. There are several types of thin film deposition, and each technique has different characteristics in terms of how the source evaporates, how fast the material is deposited, what materials are available, and the properties of the film produced.
Thin film deposition can be broadly divided into chemical and physical methods. Chemical methods deposit material through chemical reactions on the surface, while physical methods produce the source of the film mechanically or thermally. Chemical vapor deposition (CVD) is one of the most commonly used chemical methods, where a gaseous precursor reacts or decomposes to deposit the film. Physical methods are very broad and are often referred to as physical vapor deposition (PVD). PVD is usually divided into evaporation and sputtering processes.
ALD vs CVD
Atomic layer deposition (ALD) is a high-precision CVD method. Both utilize chemical reactions to deposit thin films, but ALD utilizes surface-controlled reactions rather than via flux. By separating the individual reactions in the ALD process, film thickness, density, and conformality can be better controlled. This makes ALD the method of choice for depositing ultra-thin films (10-50 nm) and/or high aspect ratio structures (> 10:1). CVD is better suited for depositing thick films at high deposition rates. CVD also has a wider range of available precursors, as decomposition is an efficient pathway.
ALD vs. PVD
PVD methods, such as sputtering, work on a very different principle than ALD and other CVD processes. For example, in sputtering, a high-energy beam bombards the source material and sends atoms toward the substrate, where they condense on the substrate surface. The key difference here is that deposition is “line of sight,” meaning only surfaces that are directly in the path of the source are coated. ALD is an isotropic process, so all surfaces are coated the same. PVD is well suited for low temperature processes and alloy deposition, especially at high deposition rates and simpler substrate geometries.
Below you can find a high-level comparison between ALD, CVD and PVD.
Comparison of Thin Film Deposition Methods
