The Ultimate Guide To Electron Beam Lithography

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Nanotechnology is a subset of nanoscale science, engineering, and technology that aims to build functional materials, devices, and systems with novel features and functions by manipulating matter at the atomic, molecular, and macromolecular levels. Nanoscale structures, which are typically less than 100 nm in size, occupy a dimensional space between ordinary macro- and mesoscale products and microdevices on the one hand, and single atoms and molecules on the other.

A scanning electron microscope (SEM)-like apparatus guides a nanometer-sized concentrated stream of electrons into a resist layer to generate a latent picture. The resist becomes more soluble (positive tone resist) or less soluble (negative tone resist) in an appropriate developer solution as a result of this exposure. After that, the pattern is transferred using etching or other methods. Complex structures with very tiny length scales can be formed by iterating a number of stages of this type.

An electron beam lithography system uses technology similar to that of a scanning electron microscope (SEM) to direct a nanometer-sized focused electron beam into a layer of resistance to create a latent picture. Depending on the tone of the resist, this exposure makes it more or less soluble in a developer solution. The resulting design is transferred to another surface via etching or deposition. Several processes of this type must be iterated upon repeatedly to develop complex structures with very small length scales.

Some of the technology’s most important features are as follows:

  1. It has an extraordinarily high resolution, almost down to the atomic level.
  2. It’s a flexible technique that can be applied with a variety of materials to create nearly limitless designs.
  3. Instruments for electron beam lithography can cost millions of dollars and require routine maintenance to keep them in good operating order.

The scanning electron microscope (SEM) was the basis for the first electron beam lithography machines, which were created in the late 1960s. The ubiquitous polymer PMMA (polymethyl methacrylate) was soon found to be a good electron beam resist. It’s amazing how much work is still being done using PMMA resist on converted SEMs today, despite huge technological advancements, significant development of commercial EBL, and a wide range of positive and negative tone resists. When an electron beam passes through the column, it is formed and controlled by the column itself. It is possible to load and unload the sample in a chamber beneath the column. This allows for easy sample movement.

A vacuum system linked to the chamber is required to keep the machine’s vacuum at an acceptable level during the load and unload cycles. The machine’s different components are powered and signaled by a system of control electronics. Finally, a computer, which may be anything from a laptop to a mainframe, manages the system.

Schematic of the electron beam lithography (EBL) fabrication process...   Download Scientific Diagram

The datapath refers to the portion of the computer or electronics that handle pattern data.

Applications Of Electron Beam Lithography

Electronic beam lithography now serves three specialized areas in the integrated circuit industry. Optical lithography tools employ chrome-on-glass masks for their optical lithography tools as the first type of mask they make. It’s the ideal method for masks since it allows for quick turnaround of a finished component based solely on information contained in a computer CAD file. Meeting rigorous linewidth control and pattern placement requirements of 50 nm each is an impressive accomplishment. Because optical steppers often lower the mask dimensions by a factor of four or five, the resolution isn’t a concern, as long as the mask is within the existing one- to the two-m range. The masks created are mostly utilized in the manufacture of integrated circuits, but they are also used in other products such as disk drive heads and flat panel displays.

Meeting rigorous linewidth control and pattern placement requirements of 50 nm each is an impressive accomplishment. Because optical steppers often lower the mask dimensions by a factor of four or five, the resolution isn’t a concern, as long as the mask is within the existing one- to the two-m range. The masks created are mostly utilized in manufacturing integrated circuits, but they are also used in other products such as disk drive heads and flat panel displays.

The second use is for sophisticated integrated circuit prototypes and small volume specialized product manufacturing, such as gallium arsenide integrated circuits and optical waveguides. Here, electron beam lithography’s flexibility and resolution are combined to create devices that are at least one or two generations ahead of current optical lithography techniques.

Finally, EBL is utilized in integrated circuit scaling limitations research as well as investigations of quantum effects and other new physics phenomena at extremely small dimensions. Here, EBL’s resolving power makes it the go-to option. For instance, the Aharanov Bohm effect, where electrons moving along two distinct micrometer-long pathways can interact constructively or destructively depending on the intensity of an applied magnetic field, is a typical use.

Nanostructured devices such as electronic, optoelectronic, and quantum structures, as well as metamaterials and investigations of semiconductor/superconductor interface transport mechanisms, can all benefit from e-beam lithography. Direct writing on non-planar substrates may be done with e-beam lithography as well as mask creation with e-beam lithography.