A 1:1 electron stepper

Abstract

A new approach to the design of a 1:1 electron stepper has been suggested. A metal-insulator–metal (MIM) cathode is used in place of the photoemission one. The mechanism of the electron emission from the MIM cathode is markedly different from that of photoemission. In the MIM cathode the electrons from the base metal layer move through the thin dielectric layer, in which a strong electric field is generated (about 7×108 V m−1), into the outer thin metal layer. Those electrons that have enough energy remaining after scattering in the dielectric and outer thin metal layer (to overcome the work function barrier of the outer metal layer) will escape into the vacuum. Compared to photoemission, the described mechanism has some advantages if considered for use in electron projection lithography. For example, an emission current density of the order of 10−4 A cm−2; the cathode can be easily and quickly switched on and off with the image of the mask and independently of the orientation marks; and finally, the possibility of preparing cathodes outside the vacuum chamber of the stepper and their storing. To verify the advantages of the MIM cathode and experimental 1:1 electron stepper has been constructed and orientation experiments have been evaluated.