Ceravision Adopts FED Technology From RAL
Fig. 1. A double grid field emitter system is used with a tip radius of under 10 nm.
Staff -- Semiconductor International, 7/1/1998
Ceravision, a small company located at the Rutherford Appleton Laboratory (RAL, Oxon, UK), is to use a novel field emission display (FED) technology to produce large, cost-effective displays. A proprietary ceramic material will be used as the substrate of each display module. Within the next 18 months. Ceravision expects to produce 40 in. diagonal displays with a thickness of the order of 2 mm at a target price of $2800 (about two-thirds of the cost of current flat screen displays).
The double grid FED technology has been developed in the Central Microsructure Facility (CMF) at RAL. An array of millions of gated silicon microtips is formed on a wafer, as shown in Figures 1 and 2, by the use of high-resolution lithography and plasma etching. Each tip has a radius of <10 nm and can emit an electron current of about 5 µA when the lower extractor grid is at a potential of some +60 V relative to the wafer. An upper grid is separated from the extractor grid by an insulating layer of silicon dioxide. This grid is used for focusing the emitted electrons onto a phosphor coating on an anode that is placed a few mm above the structure of Figure 1. Both grids have holes of the order of 1 µm in diameter through which the emitted electrons pass. Ejaz Huq, who leads this work at the CMF, told us that the structures have been monitored more than 1100 hours of continuous operation.
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| Fig. 1. A double grid field emitter system is used with a tip radius of under 10 nm. |
Ceravision intends to produce its screens by joining together 4 in. ceramic tiles that resemble bathroom tiles. For example, three ceramic panels can be joined to form an automobile dashboard display, four panels to form a laptop computer screen and 12 panels to form a display to replace the cathode ray tube of a desktop computer. The tiles can be processed on standard 150 mm silicon wafer lines. After the panels have been joined, they are sealed in an evacuated enclosure. Ceravision plans very large displays, also.
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| Fig. 2. A silicon field emitter is shown with the additional focus electrode. |
Dick Cooper, managing director of Ceravision, said, "To complement the low-voltage application of the field emitter tips, Ceravision has collaborated with its technology partners to develop low voltage phosphor materials. We have also perfected a low-temperature, proprietary, high-vacuum alignment pilot-line sealing machine that has a 40 in. diagonal flat panel display capability. We are now being pursued by various global display manufacturers to consider potential licensing, technology transfer and prototype display construction to their specification. Ceravision has a selected international specialist team in this field using numerous technology partners."
In March, Ceravision signed a three-year contract with the British government's Central Laboratory of the Research Councils (CLRC, which operates RAL). This contract provides the CLRC with a stakeholding in Ceravision in return for access to clean room facilities, microtechnology equipment and collaborative expertise. Cooper said this deal persuaded Ceravision to return to Britain from Silicon Valley and represents a new commitment by the UK government to help industry
