Fabrication of a Field Emitter Array with a Built-in Einzel Lens

A field emitter array (FEA) with four stacked gate electrodes, that is, FEA with a built-in einzel lens, was fabricated using an etch-back technique. In our method, gate hole opening is a self-aligned process; therefore, the axes of electrode holes are well aligned without precise lithography. Emitter tip opening is also a unique process: the tip opening is usually carried out using buffered hydrofluoric (BHF) acid to prevent tip damage. However, in the case of the FEA with a multistacked electrode, BHF etching produces a long undercut under the electrode, particularly under the upper electrode. In our process, the upper lens electrode is used as a photolithography mask when etching silicon dioxide in order to prevent excess undercut. In this paper, the details of fabrication are described.