Mold-type SiC field emitters with heavily boron-doped gates

Abstract

A new fabrication process for mold-type SiC sharp tips for field-emission arrays has been presented. Gated emitters have been fabricated in a multi-step process using the transfer-mold technique. Gates were made of heavily boron-doped silicon, and a boron etch-stop technique for the KOH anisotropic etching was applied. The critical points of the fabrication process: anodic bonding of the silicon covered with a thin-film multi-layer of silicon oxide and boron-doped silicon carbide have been discussed in detail. The new method can be applied in the fabrication of double-gate mold-type emitters able to emit convergent electron beams.

Anodic bonding

“…This assembly was then bonded anodically to commercial borosilicate glasses before subsequent etching and deposition steps to produce the final tips. 56 The successful use of anodic bonding with interlayers was the critical step in this technology. It also has wider significance in the context of the possibility of bonding bulk wide-gap semiconductors to borosilicate glasses, as has the even more recent work of Tudryn et al 34 There are two types of anodic bonds between two conductors using interlayers.…”

“…At room temperature silicon is a good electrical conductor while Pyrex is an insulator: values of the resistivity of n-type silicon and p-type silicon wafers quoted in the anodic bonding literature range from 3 to 30 V cm, 51,56,68,74,98 while the resistivity of Pyrex at room temperature is y10 14 V cm (Ref. 10).…”

“…This increases the possible applications of anodic bonding dramatically, for instance through the formation of 3D structures. 13,109 In addition to these reasons for using interlayers, a novel interlayer approach has recently been used by Go ´recka-Drzazga et al 56 to fabricate SiC sharp tips for field-emission arrays which have potential applications in devices such as flat panel displays and cold cathodes. To fabricate these tips a silicon wafer was first oxidised.…”

“…To analyse the creation of intimate contact in slightly more detail, we can once again choose to let the two materials to be joined to be silicon and Pyrex. At room temperature silicon is a good electrical conductor while Pyrex is an insulator: values of the resistivity of n-type silicon and p-type silicon wafers quoted in the anodic bonding literature range from 3 to 30 V cm, 51,56,68,74,98 while the resistivity of Pyrex at room temperature is y10 14 V cm (Ref. 10).…”