Low voltage electron source with self aligned gate apertures, fabrication method thereof, and x-ray generator using the electron source

Abstract

An x-ray generating device includes at least a nano-structure based field emission electron source having a self-aligned gate aperture incorporated on a substrate. The device further includes at least an anode target. Associated fabrication method is also described.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional of U.S. application Ser. No. 11 / 929,615, filed on Oct. 30, 2007, published on Feb. 12, 2009, as US 2009 / 0039754 AI, and titled “LOW VOLTAGE ELECTRON SOURCE WITH SELF ALIGNED GATE APERTURES, FABRICATION METHOD THEREOF, AND DEVICES USING THE ELECTRON SOURCE,” which is a continuation in part of U.S. application Ser. No. 10 / 707,342, filed on Dec. 5, 2003. This application is related to U.S. application Ser. No. 11 / 927,323, filed on Oct. 29, 2007, U.S. application Ser. No. 10 / 807,890, filed on Mar. 24, 2004, U.S. application Ser. No. 11 / 467,880, filed on Aug. 28, 2006, and U.S. application Ser. No. 11 / 467,876, filed on Aug. 28, 2006.FIELD OF THE INVENTION[0002]The present invention relates to an emission electron source using nano-structures as emitters and self-aligned and nano-sized gate aperture for low voltage control, the fabrication method thereof and its use in x-ray generator.DESCRIPTION OF THE RELATED ...

AI Technical Summary

Benefits of technology

This approach enables low voltage modulation, high emission uniformity, robustness against ion bombardment, and high energy efficiency, achieving a significantly higher emitter density and longer device lifetime with improved production yield and energy efficiency.

Problems solved by technology

The cost of a device driver, which often is a major cost component, power consumption, as well as device miniaturization, and ability to operate at high frequency are all depend on the modulation voltage.

Despite the superior emission properties of a single CNT, the current state of the art of a CNT electron source does not meet most of the above requirements and, therefore, has not found any product applications yet, despite the appearance of some prototype flat panel displays.

Both methods are difficult to implement in production.

E-beam lithography is so slow and expensive that it is ill suited for any meaningful operation.

Applying a mono-layer consistently over large an area is no easy task.

b) Difficulty in Fabrication of an Integrated Gate Structure

Two obstacles make the fabrication difficult.

First, CNT films is sensitive to wet processes.

Upon exposure to a wet agent, CNTs either stick to the substrate or to themselves, diminishing their field emission properties.

The problem is that a group of densely grown CNTs in a single gate hole does not emit well because of the strong electrostatic effect amongst them and the variation in their length and aspect ratio.

CNTs mixed with other chemicals to facilitate screen-printing into gate hole do not perform well either.

In addition, deposition of CNT into the gate hole often cause short circuit between the gate and the cathode electrode, resulting in low production yield.

For many high frequency applications, these high modulation voltages make the application impossible due to high energy loss and loss of signal fidelity.

As for display application, the device become impractical, since conventional CMOS display drivers will not be able to deliver it.

And due to higher current, these sites also burn out faster and, therefore, have a short lifetime.

Carbon reacts easily with oxygen, causing emitter erosion.

Accumulated re-deposition of the sputtered Carbon can then causes short circuit between electrodes.

Both growth and screen-printing of CNT into a pre-fabricated gate holes can often cause short circuit between cathode and gate electrodes.

The strict requirements of high-resolution photolithography also contribute to lower production yield and high cost.

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