Cathode ray tube type electron gun as a source for multibeam electron lithography

Abstract

The authors have investigated the potential of using a dispenser cathode in space charge limited regime for employment in an electron beam lithography electron source. The space charge limitation guarantees stable and uniform emission even if there are small work function variations or bumps and depressions on the surface. Employment of a dispenser cathode in the space charge limited regime enables high beam currents and splitting of the electron beam into many sub-beams for parallel multibeam electron lithography. In the reported experiment, the electron beam is split into 194 sub-beams. The reduced brightness, defined as current divided by normalized emittance, was measured at different cathode temperatures and extraction potentials for a cathode ray tube type electron source equipped with an I-type dispenser cathode. In the central 25 sub-beams, reduced brightness values of up to 106Am−2sr−1V−1 were observed. Such a high reduced brightness in combination with a high total emission current (up to 20mA) indicates potential application in electron beam lithography systems. In accord with theory, the experimentally observed reduced brightness is directly proportional to the emission current density. It was found, however, that the brightness drops if the emission current density is increased beyond the level where the emitter leaves the space charge limited regime. Within the space charge regime, increasing reduced brightness as a function of increasing current density is found to be caused by a decreasing virtual source size, while the angular current density remains nearly invariant.

Hundreds of electron beams from a single source

“…In a set-up as depicted in fig. 1 , we have shown [1] that it is possible to create an array of sub-beams from an impregnated tungsten cathode with brightness values up to 106 Alm 2 srY. This system is now under development to produce 13.000 sub-beams and in a next stage 500.000 sub-beams.…”

Design of a multiple-electron-beam imaging technique for surface inspection

“…[1][2][3] However, the use of simultaneous multiple electron beams in imaging ͑for, say, parallel inspection͒ has not yet been explored. [1][2][3] However, the use of simultaneous multiple electron beams in imaging ͑for, say, parallel inspection͒ has not yet been explored.…”