Ion-beam lithography is the practice of scanning a focused beam of ions in a patterned fashion across a surface in order to create very small structures such as

integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...

s or other nanostructures.

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Ion-beam lithography has been found to be useful for transferring high-fidelity patterns on three-dimensional surfaces. Ion-beam lithography offers higher resolution patterning than UV, X-ray, or electron beam lithography because these heavier particles have more momentum. This gives the ion beam a smaller

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...

than even an e-beam and therefore almost no diffraction. The momentum also reduces scattering in the target and in any residual gas. There is also a reduced potential radiation effect to sensitive underlying structures compared to x-ray and e-beam lithography. Ion-beam lithography, or ion-projection lithography, is similar to

Electron beam lithography Electron-beam lithography (often abbreviated as e-beam lithography, EBL) is the practice of scanning a focused beam of electrons to draw custom shapes on a surface covered with an electron-sensitive film called a resist (exposing). The electron b ...

, but uses much heavier charged particles,

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

s. In addition to diffraction being negligible, ions move in straighter paths than electrons do both through vacuum and through matter, so there seems be a potential for very high resolution. Secondary particles (electrons and atoms) have very short range, because of the lower speed of the ions. On the other hand, intense sources are more difficult to make and higher acceleration voltages are needed for a given range. Due to the higher energy loss rate, higher particle energy for a given range and the absence of significant space charge effects,

shot noise Shot noise or Poisson noise is a type of noise which can be modeled by a Poisson process. In electronics shot noise originates from the discrete nature of electric charge. Shot noise also occurs in photon counting in optical devices, where shot ...

will tend to be greater. Fast-moving ions interact differently with matter than electrons do, and, owing to their higher momentum, their optical properties are different. They have much shorter range in matter and move straighter through it. At low energies, at the end of the range, they lose more of their energy to the atomic nuclei, rather than to the atoms, so that atoms are dislocated rather than ionized. If the ions don't defuse out of the resist, they dope it. The energy loss in matter follows a

Bragg curve The Bragg peak is a pronounced peak on the Bragg curve which plots the energy loss of ionizing radiation during its travel through matter. For protons, α-rays, and other ion rays, the peak occurs immediately before the particles come to rest ...

and has a smaller statistical spread. They are "stiffer" optically, they require larger fields or distances to focus or bend. The higher momentum resists space charge effects. Collider particle accelerators have shown that it is possible to focus and steer high momentum charged particles with very great precision.

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{{DEFAULTSORT:Ion Beam Lithography Semiconductor device fabrication

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