Proximity Effect in Electron-Beam-Induced Deposition

We studied the proximity effect in electron-beam-induced deposition (EBID), namely, the frequent deformation of deposited structures as a result of a subsequent deposition performed nearby. Our study showed that this effect largely depends on the conductivity of the substrate used, indicating that electrostatic forces are responsible for the effect. An alternate scan sequence, aimed at reducing charge accumulation during the deposition, was proposed and demonstrated. Using this scan sequence, we were able to fabricate closely separated rods. The electrostatic force responsible for the proximity effect has a scaling feature: the smaller the scale, the stronger the effect of the electrostatic force. For three-dimensional nanostructure fabrications, this feature will enforce another limitation in the size, besides the usual achievable resolution limits imposed by EBID.