Technological advancement has revolutionized the world of printing. One such technology is the electron beam lithography. This powerful technology can draw patterns on the surface of any material when coated with a layer of resist. The material, when exposed to the electrons, becomes highly soluble. As a result, it can be removed by immersing it in a solvent. Thus, it becomes solvent-resistant so that the surrounding resist gets removed easily. 

With the help of electron lithography, tiny nanostructures can be manufactured with high accuracy. Eventually, there won’t be any need for a photomask because the technology is strong enough to create those nanostructures at less than 10nm resolution. Thus, this electron beam lithography system becomes more suited for designing high-resolution patterns, for which photomask would have been just wasteful.

How Does It Work?

In electron lithography, the electron source is Hot W/ZrO2. To focus the beam, magnetic or electrostatic lenses are used. The layers of the resist are multiple having varying sensitivities with each other. This helps in adjusting their solubility of the electron beam depending on the volume. Thus, with the help of processes like secondary electron production, diffusion or scattering, the whole work gets done. 

Why ‘Grounding’ Becomes Important

Under the set-up of an electron beam lithography, the materials remain exposed to an intense beam of electrons. However, it becomes important to ground these materials just to prevent charging effects. But, how is it done? Often, a thin metal layer of aluminium or gold is added between the resist and the substrate. In most cases, the layer is also added on top of the resist. 

Biological Advancements

In the field of Biology or Molecular Sciences, this technology is of great use. Using an electron beam lithography system, Biomolecules are patterned on the substrate surface. This helps in creating repeating structural features having different chemistries. Hence, they become suitable for immobilizing different biomolecules in various directions.

Research Tools

Various research tools are now using this technology in renowned laboratories across the world. Some of them are listed below.

• ELS-F150

The ELS-F150 has 4nm line width, making it the world’s first 150 kV electron beam lithography system. It can expand on the 100kV and 125kV systems as well, but the speciality of this is that it enables single nanoscale device fabrication. It features a 1.5nm beam diameter, with a minimum proximity effect of 150kV. However, the wider process margin in it makes it easier for fabricating nanodevices. It further has a single-cassette auto-loader that supports 8” wafers.

• ELS-G100

This electron beam lithography system comes with a 1.8nm diameter. It uses acceleration voltages up to 100kV, along with high beam currents. By using this tool, one can easily draw fine patterns with a line width of less than 6nm. Further, the device is equipped with a 20bit DAC that provides high beam positioning resolution. In short, without stitching, 20nm lines can be easily drawn over 500µm field.

Production Tools

The electron beam lithography system is also used in industries and factories via various production tools.

• ELS-H50

The ELS-HS50 features a 10nm beam spot size for 100nA of beam current. The device can reach sub-micron scales that are unachievable using laser lithography. Its meticulous designing works for low volume device fabrication causing little line edge roughness. Under this model, both single cassette and multiple cassettes are available. 

• ELF-10000

This ELF model is undoubtedly a beast! Within just 24 hours, the device enables 9-inch wafer-seized fabrications of nanoimprint moulds. It also reduces the number of stitching boundaries drastically. When compared with other devices and models, the ELF-10000 has the largest field size of 10mm square. As a result, this machine is just perfect for large fabrication write fields of machining fabrication. 

Advantages

• Best resolution

In electron lithography, resolution mostly depends on the type of resist used, its thickness and the type of substrate, taking into consideration other conditions as well. Nevertheless, since it can write custom patterns with 10nm resolution, therefore, the resolution remains mostly high. 

• Accuracy

The technology uses a writing area of 1-2 mm. But, in case of larger areas patterns, they ought to be subdivided into other fields. However, there can be hardly any stitching errors in the electron beam lithography system since it uses a laser interferometer stage. 

Undoubtedly, The Best Technology!

The best aspect of this technology is that it can automatically detect alignment marks. Therefore, the accuracy remains high and mostly remains within 10s of nms. It has splendid mark detection techniques. Presently, most practical devices need lithography because of less overlay error. Most importantly, the technology is effective in reducing the problem of diffraction. Electron beam lithography system have automated working, backed by a well-balanced operation. Unlike optical lithography, it has a greater depth of focus. It can complete bulks of work in no time.