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Subminiature Multi-Beam Cathode Structure and Fabrication Techniques

IP.com Disclosure Number: IPCOM000035842D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 43K

Publishing Venue

IBM

Related People

Beck, V: AUTHOR [+5]

Abstract

Subminiature multi-beam cathode structure and fabrication techniques produce cathodes recessed beneath the plane of the substrate grid, by an amount approximately equal to or greater than the grid-to-cathode insulating gap.

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Subminiature Multi-Beam Cathode Structure and Fabrication Techniques

Subminiature multi-beam cathode structure and fabrication techniques produce cathodes recessed beneath the plane of the substrate grid, by an amount approximately equal to or greater than the grid-to-cathode insulating gap.

Sapphire is chosen as a substrate material because it sufficiently retains its insulation characteristics at the device operating temperature range of 800 to 900oC. The sapphire chosen for the substrate is of R-plane orientation, that is, the (1 1 0 2) plane. This plane was chosen so that a plurality of multi-beam cathode arrays could be fabricated on one wafer after which the wafer could be scribed and diced as is done in the silicon-on-sapphire process. By choosing the R-plane the wafer cleaves in a direction almost vertical to the plane of the top surface.

Fig. 1 depicts one element of a recessed multi-beam cathode structure. The substrate is sapphire 11, and the cathode 12 and grid 13 are a suitable metal, such as a refractory, refractory alloy or nickel.

(Image Omitted)

A suitable structure is fabricated by etching the sapphire 11 to the desired profile, by photon sputtering or selective negative ion etching. An array of cathode 12 is created with the cathode 12, lead and bond pad all recessed a distance beneath the surface equal to or greater than the lateral distance across the insualtion gap. Next the cathode-grid metallurgy 13 is deposited. The metallurgy 13 is then photomasked and etched to remove the metal in the insulating gap regions. The entire cathode 12, interconnection lead, and bonding pad are...