Physical vapour deposition (PVD) is a process of thin film deposition using either a thermal evaporation process or magnetron sputtering to deposit thin films of a source material onto a substrate surface[1].
But how does the PVD process affect film quality and deposition rate? What PVD methods should you consider for good film quality with excellent uniformity? In optical applications, is an evaporative or a sputtering process more effective?
Learn more below about the differences between sputter systems and evaporation in the PVD process to help you choose between evaporation vs sputtering for your application.
Understanding Physical Vapour Deposition
In physical vapour deposition, molecules from a source material are vaporised to form thin films that coat a substrate surface inside a vacuum chamber. The target material that forms the thin film is subject to either energetic ions in ion beam sputtering or vaporisation temperature in electron beam evaporation.
The sputtering process allows the application of thin film technology for any target material with high melting temperatures, and is a proven option for architectural glass and thin film transistors. Electron beam evaporation is better for any solid source material with low melting points that don’t need much thermal energy to vaporise[2].
E-beam evaporation has a higher deposition rate and excellent uniformity and is popular in the aerospace, tool manufacturing, and semiconductor industries.
Evaporation: Overview and Applications
Most physical vapour deposition (PVD) evaporation systems use an electron beam to bombard a tungsten substrate or other materials in a vacuum chamber or a resistive heat source to vaporise the material, allowing it to settle over a substrate to form a thin film coating. However, these evaporation methods have several differences.
Thermal Evaporation by Resistive Heating
In resistive thermal evaporation, the target material is placed in a boat or crucible in a resistive electrical coil. The coil receives a high current, heating the material. The material heating in the vacuum chamber vaporises to coat the substrate, as in the Korvus TES thermal boat system.
Review thermal evaporation explained in more depth, and learn more about the TES here.
Electron Beam Evaporation
E-beam evaporation uses an electron beam to bring the source material to its gaseous form to create thin films. Learn more about the TAU E-Beam source and how it differs from typical electron evaporation.
Low Temperature Thermal Evaporation
In low temperature evaporation, resistive thermal evaporation or e-beam evaporation is balanced with a cooling source around the boat for better control of the evaporation and deposition rate.
Learn more about the ORCA Organic Evaporation source.
Pros and Cons of Evaporation
Each evaporation method to deposit thin films onto a substrate has benefits and disadvantages.
Pros:
- Suitable for a wide range of sources and excellent for applications over electrical contacts
- High deposition rate
- Excellent uniformity when using masks or planetary
- Electron beam evaporation is good for materials with high melting points
- E-beam evaporation offers high throughput
- Useful in solar panels, architectural glass, thin film transistors, eyeglasses, and more
Cons:
- Poor uniformity without planetary or masks
- Moderate system complexity in electron beam evaporation
Sputtering: Overview and Applications
Sputtering is another PVD process that uses ionised gas in processes such as ion beam sputtering, reactive sputtering, plasma sputtering, and other types of magnetron sputtering to produce high-quality films[3].
Sputtering offers high deposition rates and volume production, including thin film application in semiconductor circuits, thin film transistor parts, anti-reflective glass coatings for eyeglasses, and low-e architectural glass coatings.
In magnetron sputtering, a plasma-based coating method, positively charged ions from magnetically confined plasma collide with negatively charged substrates in a closed magnetic field, offering the highest scalability of any PVD process[4].
Learn more about the sputtering process here, and discover the benefits of the FISSION Sputtering source.
Pros and Cons of Sputtering
Sputtering methods to deposit thin films onto substrates come with their own pros and cons.
Pros:
- High deposition rate
- Moderate to high stress film density
- High throughput
- Highest uniformity in ion beam sputtering (IBS), good uniformity in magnetron sputtering
- Highest quality films using IBS
- Magnetron sputtering is excellent for dense films, strong adhesion to the substrate, film deposition for optical applications and electrical parts, and automated applications
- IBS is ideal for high-quality film deposition when control over stoichiometry or film thickness is essential
Cons:
- Poor deposition rate for dielectrics
- High system complexity and high cost
- Energised vapour material can cause substrate heating
- Low deposition rates for IBS
Sputtering vs Evaporation: Which To Choose?
How do you know which method to choose: evaporation or sputtering? Evaporation is more cost effective and less complex. Additionally, evaporation offers higher deposition rates, allowing for high throughput and high-volume production.
In contrast, sputtering offers better film quality and uniformity, potentially leading to a higher yield. It also offers scalability, although at a higher cost and with more complex setups.
For thicker metallic or insulation coatings, sputtering may be the better option. For thinner films of metals or nonmetals, resistive thermal evaporation may be better for film materials with lower melting temperatures. Electron beam evaporation could be the right choice for improved step coverage or if working with a wide selection of materials.
Choose Korvus Technology for Physical Vapour Deposition Systems
At Korvus Technology, we offer the HEX Series PVD system with several customisation options for TAU, TES, ORCA, and FISSION sources for applying thin films under carefully controlled parameters. Contact us today to learn more about our systems and decide whether evaporation vs sputtering is right for you.
References
[1] Donald M. Mattox (2010). Chapter 1 – Introduction, Handbook of Physical Vapor Deposition (PVD) Processing (Second Edition), 1-24, DOI: 10.1016/B978-0-8155-2037-5.00001-0
[2] M. R. Rashidian Vaziri, F. Hajiesmaeilbaigi, M. H. Maleki; Monte Carlo simulation of the subsurface growth mode during pulsed laser deposition. Journal of Applied Physics 15 August 2011; 110 (4): 043304. https://doi.org/10.1063/1.3624768
[3] Martin, P.J. Ion-based methods for optical thin film deposition. J Mater Sci 21, 1–25 (1986). https://doi.org/10.1007/BF01144693
[4] Ghazal, H., & Sohail, N. (2023). Sputtering Deposition. IntechOpen. doi: 10.5772/intechopen.107353
