Ion Beam Lithography

• Ions interact with the photoresist, instead of photons, changing its chemistry, the photoresist can then be removed during developing
• Advantages of ion beams:
  • Higher resist sensitivity
  • Can be focused to narrower linewidth
  • Reduced Scattering
  • Allows hybrid processes such as ion-induced etching and implantation
• Types of ion beam lithography are shown in the three pictures below: direct, contact, projection

• FIBL -projection
  • Electrostatic lenses are employed due to large mass of ions
  • Mass spectrometers are used to separate different species of ions
  • Effects of the ion beam on the substrate:
    • Displacement of atoms.
    • Emission of electrons.
    • Chemical effect - change of solubility of the resist.
    • Sputtering of substrate atoms by low energy ions.
  • May result in resist heating as high as 1500oC