Electronic beam evaporation, also known as e-beam evaporation, is one of the four forms of physical vapour deposition (PVD). It uses an intense beam of high-energy electrons to evaporate the source material [1], reducing limitations on maximum evaporation temperatures.
E-beam evaporation works in contrast to sputtering, which collides energetic ions with a target to sputter or eject the target material. Electron beam evaporation expands upon the applications of thin film deposition common to more traditional vaporisation processes.
But which method is better? Is electron beam evaporation what you need from your thin film deposition system?
Read ahead to learn the ins and outs of electron beam evaporation, along with its advantages over sputtering, from our Korvus Technology team.
How Does Electron Beam Evaporation Work?
Electron beam evaporation is a form of physical vapour deposition that uses a focused electron beam within a vacuum environment to heat evaporation material. The e-beam evaporation process is based on the evaporation of tungsten filaments.
The evaporation system sends an electric current of sufficient energy, between five and ten kV, through the tungsten filament, which is located outside the deposition area. This high-voltage current heats the tungsten to high temperatures, allowing the thermionic emission of electrons to occur.
The e-beam evaporation system then uses permanent magnets or electromagnetic focusing to direct the high-energy electrons toward the target material, which is placed in a water-cooled crucible.
When the electron beam hits the target material, its kinetic energy transforms into heat, releasing high thermal energy as a vapor phase. The evaporated material disperses in its gaseous phase within the high vacuum chamber.
This focused, high kinetic energy can evaporate high melting point materials not capable of evaporation through traditional deposition methods. It yields very high deposition rates at low substrate temperatures.
This method of thermal evaporation is useful for deposit metals, refractory metals, optical thin films, and a range of other electron beam evaporation applications.
How Is Sputtering Different from Electron Beam Evaporation?
While sputtering and e-beam evaporation are both forms of physical vapour deposition, their deposition processes differ significantly.
Electron beam evaporation is a form of thermal evaporation. The thermal evaporation process focuses an electron beam on a source material to produce very high temperatures, allowing it to vaporise high-temperature materials.
Meanwhile, magnetron sputtering collides positively charged energetic ions with a negatively charged target material, ejecting atoms from the target material and depositing them onto a substrate. Sputtering occurs within a closed magnetic field, while electron beam evaporation occurs within a vacuum or deposition chamber.
Both sputtering and e-beam evaporation have a low level of impurity, but e-beam PVD has a higher deposition rate. However, sputtering has the highest rate of scalability, as it can be automated in many applications.
In some cases, using ion-beam-assisted deposition, such as that involved in sputtering, can expand the functionality of thermal evaporation. Understanding the right evaporation system, or the right combination of systems is essential to optimising precision, functionality, and efficiency in your desired application.
What Are the Advantages of Electron Beam Evaporation?
One significant advantage of electron beam heating is its higher maximum evaporation temperature than traditional thermal evaporation. This method of evaporation can vaporise metals with high melting temperatures, such as
- Tungsten
- Niobium
- Silicon dioxide
- Ruthenium
By heating the target material directly, electron beam evaporation allows for high material utilisation and is applicable across a broad range of evaporation materials. Electron beam evaporation applications vary between ceramic coating deposition [2], the growth of zinc oxide thin films [3], creating coatings to protect surfaces in corrosive environments, and more.
One of the most promising uses of electron beam evaporation is within laser optics. The thin films produced by this thermal deposition process are ideal for optical coatings, such as those on solar panels, eyeglasses, architectural glass, and more.
Electron beam evaporation is also applicable in the aerospace and automotive industries. These industries often have high temperature requirements and strict guidelines for the wear resistance of their materials.
Why Is Evaporation Better than Sputtering?
Electron beam evaporation and sputtering both have a range of applications. However, electron beam physical vapour deposition allows for the vaporisation of high-melting-point materials with a relatively low deposition time [4].
E-beam evaporation is more suitable for high-volume batch production and thin-film optical coatings. While sputtering is applicable to some optical processes, its applications are more limited. As such, sputtering is more commonly used within applications requiring high levels of automation.
What Are the Disadvantages of E-Beam Evaporation?
While electron beam PVD has some industrial applications, it is not suitable for coating the inner surface of complex geometries. Additionally, the filament degradation used within this vaporisation process can produce a non-uniform evaporating rate, producing less precise results than other methods.
Evaporation deposition also has limited scalability with a lower utilisation and deposition rate. Further, this system is relatively complex, leading to a higher cost compared to other deposition methods, like pulsed laser deposition or chemical vapor deposition.
Weighing up the advantages and disadvantages of this thermal evaporation technique can help you determine whether it is suitable for your application.
The TAU Electron Beam Evaporation System
The TAU e-beam evaporation system from Korvus produces a heating and evaporation effect through a “mini” source. While larger e-beam evaporation systems use beam-bending magnets, the TAU system uses low voltage and an enclosed head, containing the thermal load within a high vacuum chamber.
Our TAU e-beam evaporator is a source for the HEX thin film deposition system that enables electron beam evaporation. Explore our thin-film deposition systems today to learn more.
References
[1] Bashir, Almas, Iqbal Awan, TAhir, Tehseen, Aqsa, Bilal Tahir, Muhammad, Ijaz, Mosin. (2020, May 27). Interfaces and surfaces. Chemistry of Nanomaterials. Retrieved December 28, 2022, from https://www.sciencedirect.com/science/article/pii/B9780128189085000032
[2] Shamala, K. S., Metzner, C., Maiti, N., Zhigarev, A. A., Evans, ?., Kanareykin, A. D., Ganz, S. N., Avdeeva, D. K., Garshin, A. P., Balkevich, V. L., Kunevich, A. V., … Hocking, M. G. (2017, June 19). Ceramic coating deposition by electron beam evaporation. Surface and Coatings Technology. Retrieved December 28, 2022, from https://www.sciencedirect.com/science/article/abs/pii/S025789721730645X
[3] Caglar, M., Fang, G. J., Karuppasamy, A., Asmar, R. A., Zhu, B. L., Daniel, G. P., Fang, Z. B., Zhang, D. H., Chu, S. Y., Zhaoyang, W., Li, X. H., & Kim, D. C. (2011, March 29). Effect of heat treatment on characteristics of nanocrystalline ZnO films by electron beam evaporation. Vacuum. Retrieved December 28, 2022, from https://www.sciencedirect.com/science/article/abs/pii/S0042207X11001205[4] Maiti, N., Karmakar, P., Barve, U. D., & Bapat, A. V. (2008). An evaporation system for film deposition using electron beam sources. IOPScience. Retrieved December 28, 2022, from https://iopscience.iop.org/article/10.1088/1742-6596/114/1/012049
