Electron beam lithography (EBL)(Raith ELPHY Quantum module)

The system can expose with energies up to 30 keV and can cover an area of 100 µm by 100 µm without stitching. Depending on the resist and processing conditions, the system can write structures with dimensions down to a few tens of nanometers. Specifications can be found here.

Electron Beam Lithography refers to a lithographic process that uses a focused beam of electrons to form the circuit patterns needed for material deposition on (or removal from) the wafer, in contrast with optical lithography which uses light for the same purpose.  
Electron lithography offers higher patterning resolution (down to 20-30 nm) than optical lithography because of the shorter wavelength of the employed electrons of 10-50 keV.  
          
Given the availability of technology that allows a small-diameter focused beam of electrons to be scanned over a surface, an EBL system doesn't need masks anymore to perform its task (unlike optical lithography, which uses photomasks to project the patterns).  An EBL system simply 'draws' the pattern over the resist wafer using the electron beam as its drawing pen.  Thus, EBL systems produce the resist pattern in a 'serial' manner, making it slow compared to optical systems.
               
A typical EBL system consists of the following parts:  1) an electron gun or electron source that supplies the electrons; 2) an electron column that 'shapes' and focuses the electron beam; 3) a mechanical stage that positions the wafer under the electron beam; 4) a wafer handling system that automatically feeds wafers to the system and unloads them after processing; and 5) a computer system that controls the equipment.

The resolution of optical lithography is limited by diffraction, but this is not a problem for electron lithography.  The reason for this is the short wavelengths (0.2-0.5 angstroms) exhibited by the electrons in the energy range that they are being used by EBL systems. However, the resolution of an electron lithography system may be constrained by other factors, such as electron scattering in the resist and by various aberrations in its electron optics. (source: www.siliconfareast.com)