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Thin-film deposition is a group of processes that deliberately form a thin layer of material on a substrate or on layers already present. The deposited film can provide electrical, optical, chemical, protective or mechanical properties. The main process families differ in how they create the film: physical vapor deposition (PVD) vaporizes a condensed source, chemical vapor deposition (CVD) uses gaseous reactants and chemical reactions, and atomic layer deposition (ALD) builds a film through saturated surface reactions.
What thin-film deposition does
A substrate is the surface that receives the film. It may be a wafer, photovoltaic material, optical component or another object, and deposition may be one step in a larger fabrication process. The layer is chosen to add a function or change the surface—for example, to conduct or insulate electricity, control light, act as a diffusion barrier, or resist corrosion or wear.
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“Thin film” does not have one universal thickness cutoff across all fields. The appropriate thickness depends on the application and the process; it is not possible to define the term by one number for every deposited layer.
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How the main deposition methods differ
| Method | How the film forms | Useful distinction |
|---|---|---|
| PVD | Material from a condensed source is physically vaporized; the vapor reaches the substrate and condenses there. | Common examples include thermal evaporation and sputtering. |
| CVD | Gaseous reactants decompose or react near the substrate, producing the deposited material. | The defining route is chemical formation from gaseous precursors; energy may be supplied in different ways. |
| ALD | Saturated surface reactions form the film in controlled reaction steps. | Often useful when conformal coverage and step coverage on complex features matter. |
Physical vapor deposition (PVD)
In basic PVD, material is vaporized from a solid source, commonly in a vacuum, and atoms or molecules condense on the substrate. Thermal evaporation and sputter deposition are two common examples. PVD is used for metals, alloys, metal oxides and some composites. The University of Akron’s facility overview gives a general range of a few angstroms to thousands of angstroms for film thickness and typical deposition rates of 1–100 Å/s; these are that facility page’s figures, not universal specifications, and the page does not state a publication year: University of Akron: Thin Film Physical Vapor Deposition (PVD) System.
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PVD should not be reduced to simple evaporation in every case. Some variants introduce reactive gases to help synthesize compound coatings; the Australian Government’s technical note describes gas additions as a modification of thermal evaporation PVD: Australian Government: Technical note: Deposition techniques.
Chemical vapor deposition (CVD)
CVD supplies gaseous reactants that decompose or combine near the substrate, leaving the desired material on its surface. In the Australian Government’s definition, deposition occurs on a heated substrate, with reaction energy potentially supplied by substrate heat, glow-discharge plasma or laser irradiation. The method is therefore distinguished from PVD by chemical production of the deposit from vapor-phase reactants, rather than physical vaporization of a condensed source. See the Australian Government’s technical note and the INFLIBNET Centre chapter on thin-film deposition techniques.
Atomic layer deposition (ALD)
ALD uses saturated surface reactions to grow a film in controlled steps. Because the reactions take place at the surface, ALD can be useful when a substrate has difficult-to-coat features and the film must follow their contours. Eindhoven University of Technology identifies excellent step coverage and low processing temperatures among the circumstances where ALD can be useful: Eindhoven University of Technology: ALD.
Stanford Nanofabrication Facility describes ALD use for highly conformal films under 50 nm. That is a facility capability description, not a universal thickness limit or part of ALD’s definition: Stanford Nanofabrication Facility: Deposition.
Where thin films are used
Deposited films appear in semiconductor and photovoltaic devices, optical and reflective coatings, electrical and insulating layers, diffusion barriers, and protective or other functional coatings. These are examples, not fixed rules assigning each material to only one process.
Facility listings illustrate the range: Shanghai Jiao Tong University identifies CVD silicon dioxide and silicon films, PVD aluminum, copper and tantalum oxide, and ALD high-k hafnium oxide and ferroelectric films. The materials named reflect that platform’s capabilities rather than an exhaustive mapping of materials to methods: Shanghai Jiao Tong University, Advanced Electronic Materials and Devices Platform: Thin Film Growth & Deposition. The University of Akron and INFLIBNET also describe applications in electronics, photovoltaics and coatings.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to choose a deposition method
There is no method that is best for every film. A useful process choice starts with the required result and the limits of the substrate and available equipment.
- Film material and function: Specify composition and the electrical, optical, mechanical, chemical or protective properties the layer must provide.
- Geometry and coverage: A flat surface and a high-aspect-ratio feature may have very different coverage needs. Consider whether the film must coat sidewalls and recessed areas conformally.
- Thermal limits: Check both the substrate’s temperature tolerance and the process temperature or other energy input.
- Thickness and uniformity: Define the target thickness and acceptable variation across the substrate or feature.
- Tool and process constraints: Confirm compatibility with the source material or precursors, equipment capability and facility access.
These criteria reflect the distinct capabilities and examples described by facilities such as Stanford Nanofabrication Facility and Shanghai Jiao Tong University’s Advanced Electronic Materials and Devices Platform. A specific recommendation requires the material, geometry, thermal limits and performance requirements; the process name alone is not enough.
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