Field-emitter having a sharp apex and small-apertured gate and method for fabricating emitter

A method of fabricating a minute field-emitter comprising the steps of,

• forming an etching mask of circular or diagonal shape on a conductive substrate or a conductive layer,
• etching the part of the surface of the conductive substrate or the conductive layer not covered by the mask to form a pillar-shaped structure with the side perpendicular to the substrate surface,
• removing the etching mask and etching the surfaces of upper and side parts of the pillar-shaped structure to obtain a minute pillar-shaped structure having a diameter or a width which is smaller than the pillar-shaped structure,
• depositing a protection layer on the upper surface of the minute pillar-shaped structure and the substrate surface,
• forming an oxide layer on the side of the minute pillar-shaped structure,
• depositing around the minute pillar-shaped structure an insulator and then a conductor for a gate, using the protection layer formed on top of the minute pillar-shaped structure as a mask, and
• removing the protection layer and oxide layer to form a cathode having a minute cathode and a gate with a small aperture.

A method of fabricating a minute field-emitter on a conductive substrate of silicon with a surface in the (100) plane of silicon comprising the steps of:

• forming an etching mask of circular or polygonal shape on the surface,
• applying dry etching to the surface to form, under the etching mask, a pillar-shaped structure perpendicular to the surface, and
• applying anisotropical etching to form an upper inverted conical structure and a lower conical structure facing each other;
• removing the etching mask,
• isotropical etching the surface of the conical structures to reduce the size thereof to form a minute upper structure and a lower minute structure,
• thermally oxidizing the minute structures to form a silicon oxide layer on the minute structures to separate the upper minute structure from the lower minute structure,
• depositing around the lower minute structure an insulator and then a conductor as a gate employing the upper minute structure as a mask, and
• etching off the oxide layer to remove the upper minute structure together with insulator and conductor thereon as well as the oxide covering the top of the lower minute structure to obtain a cathode with a sharp apex and a gate with a small aperture.

A method of fabricating a minute field-emitter on a conductive substrate or a conductive layer comprising the steps of:

• a structure forming process, which includes applying dry etching to the surface of the conductive surface or conductive layer to form, under an etching mask, a cylindrical structure perpendicular to the surface or layer,
• applying anisotropic etching to form a conical structure having an upper inverted structure and a lower structure facing each other;
• thermally oxidizing the surface of the conical shaped structured to form a silicon oxide layer on the structures and separating the upper structure from the lower structure;
• vacuum depositing in directions, slanted from the substrate surface to deposit on the surface of the lower structure covered with silicon oxide film a conducting material for a gate, and
• etching off the oxide layer to remove the upper structure together with the oxide layer near the top of the lower structure to form a minute cathode with a cathode having a sharp apex and a gate with a small aperture around the cathode.

A method of fabricating a field-emission element comprising:

• a conductive substrate having a cathode with a sharp apex protruding from the conductive substrate,
• an insulating material covering the surface of the substrate and surrounding said cathode, and
• a conductive material covering the surface of the insulating material having an aperture with a width of less than 1 .mu.m,
• wherein said aperture is produced including the steps of:
• patterning a covering layer of said substrate using an etching mask made by lithography, and
• etching the patterned covering layer to form a minute etching mask of the covering layer that is smaller than said etching mask made by lithography.