Fabrication of Biosensor Chips - From Bioimaging to Biosensors: Noble Metal Nanoparticles in Biodetection - page 123

used for holographic exposure. Figure 6.11 is the SEM image of a
holographic grating with a grove density of 1800 groves/mm.

6.3.4 Electron-Beam Direct Writing

Electron-beam direct writing is the method of scanning a beam of
electrons in a patterned fashion across the surface of a substrate and
selectively removing the exposed regions. The depth of the substrate
removed by the electron beam depends on the energy and scanning
velocity of the electron beam. As the diameter of the electron
beam could be less than 5 nm, this method has a very high spatial
resolution, far better than the diffraction limit of optical masks
employed by other methods. This method, however, suffers from the
long fabrication time, as it takes a long time to scan the electron beam
across the entire substrate. Figures 6.12 and 6.13 show the photo of
the ELIONIX ELS-7500 EX electron-beam direct writing system and
the SEM image of a grating fabricated by this system, respectively.

Figure 6.12 Photo of the ELIONIX ELS-7500 EX electron-beam direct
writing system [29].

Figure 6.13 SEM image of silicon gratings [37].