You look at Electronic beam lithography all wrong. Here’s what you need to now
When it comes to electron beam lithography systems, some people get all the aspects wrong. In fact, there have been cases where electron lithography cases have been confused for conventional photolithography. It is important noting that photolithography uses the UV light to expose the design pattern on the wafer surface. While the photolithography technology has been successful in the industry, several alternative forms of lithography that do not rely on use of UV light have been introduced into the industry. A good example is the Electron Beam Lithography technology.
In this post, we cover important aspects about electron lithography technology.
What is Electron Beam Lithography?
Electron Beam Lithography is a powerful technology that involves creation of nanostructures. Compared to conventional photolithography, the electron lithography technology creates nanostructures that are too small to fabricate.
Basically, E-beam systems feature a modern technology that uses beams of electrons extracted, focused and accelerated to 20kV. In E-beam systems, the three major sources of electrons are thermionic emitters, the photo emitters, and the field emitters.
Why is the Use of Electron Lithography Technology Important Today?
As explained above, the EBL systems involve creation of nanostructures that are too small to fabricate with the conventional photolithography. There are two important reasons why EBL is an important technology.
- Scale: Electron Beam Lithography allows patterning of small features often with the dimensions of sub micrometer down to a few nanometers.
- Direct Writing: The technology covers the selected areas of surface by the resist, or exposes the resist covered areas. Therefore, the advantage of e-beam lithography stems from the shorter wavelength of the accelerated electrons compared to the wavelength of ultraviolet light that is used in photolithography.
Therefore, modern electron beam lithography systems are capable of achieving resolutions of a few nanometers. The technique involves moving the highly focused electron beam over a sample, hence writing out the patterns designed with suitable CAD tools.
While Electron Beam Technology has several advantages over conventional photolithography, the technology has some disadvantages. To begin with, the electron lithography systems are very expensive. Therefore, organizations have to put in a substantial amount to afford the systems. Second, the E-beam lithography systems feature a high maintenance cost. Therefore, apart from the high cost of acquiring the E-beam systems, the user has to cope with the high maintenance costs. Another challenge has to do with backscattering and forward scattering, along with slower speeds. The slower speed is because as the electrons penetrate the resistor, some fraction of the electrons undergo small angle scattering. Forward scattering problem could result in a significantly broader beam profile at the bottom of the resist compared to the top.
Pattern Transfer Technologies in E-Beam Systems
Electron Beam Lithography exposes and develops the resist layer on top of the sample. The resist layer serves as a mask or as a template for transferring the pattern into a more useful medium. Generally, two main pattern transfer techniques apply in electron beam lithography.
The first pattern transfer technology involves etching material away underneath the voids in the resist layer. The second E-Beam lithography pattern transfer technology involves depositing a layer of metallic material covering the sample, and then dissolving away the remainder resist in order to lift off the deposited material on top, and leave the deposited material only in the areas where there is no resist present.
What Are the Distinct Uses of Electron Beam Lithography?
Ideally, the uses of e-beam lithography span a wide range of nanostructure devices. This includes but is not limited to:
- Electronic devices
- Opto-electronic devices
- Quantum structures
- Transport mechanism studies of semiconductors or superconductor interfaces
- Microelectromechanical systems
- Photonic devices
Therefore, the E-beam lithography systems can be used for mask making and for direct writing on the non-planar systems.
We have covered important aspects you need to know about the electron beam lithography systems. The electron beam lithography systems are derived from the early scanning electron microscopes. The systems are classified according to the beam shape and the beam deflection strategy. It is important noting that the technology is not the same as photolithography.