Field emission tips, arrays, and devices

Abstract

A field emission tip includes a base with a central portion and a tapered portion. The central portion of the base includes a peripheral surface, at least a portion of which is oriented substantially vertically or perpendicularly relative to a plane in which a substrate from which the field emission tip protrudes resides. An apex may be located at an exposed end of the central portion of the base. The tapered portion of the base includes an inclined surface that extends toward the exposed end of the central portion of the base. The tapered portion of the base may be formed from material that is redeposited as the emission tip is fabricated. The apex may be formed, at least in part, from a low work function material, such as one or more of aluminum titanium silicide, titanium silicide nitride, titanium nitride, tri-chromium mono-silicon, and tantalum nitride. Field emission arrays and field emission displays that include such field emission tips are also disclosed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of application Ser. No. 09 / 939,848, filed Aug. 27, 2001, pending, which is a divisional of application Ser. No. 09 / 559,153, filed Apr. 26, 2000, now U.S. Pat. No. 6,387,717, issued May 14, 2002.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to field emitters and methods of fabricating the same. More particularly, the present invention relates to forming field emission tips by the use of facet etching. [0004] 2. Background of Related Art [0005] Various types of field emitters are used in a variety of devices, from electron microscopes to ion guns. However, one of the most prevalent commercial applications of field emitters is flat panel displays, such as cold cathode field emission displays (“FEDs”) used for portable computers and other lightweight, portable information display devices. [0006] As illustrated in FIG. 18, an exemplary flat panel cold cath...

AI Technical Summary

Benefits of technology

[0012] The facet etching is generally performed in a chamber in which ions can be accelerated to strike a substrate, such as reactive ion etchers, magnetically enhanced reactive ion etchers, low pressure sputter etchers, and high density source etchers. As opposed to anisotropic etches, such as ion etching or plasma etching processes, in which ions strike the surface of the substrate substantially perpendicular to result in a vertical etch, a facet etch results in ions dispersed in a fashion which results in the ions striking 90 degree features (i.e., comers) of structures on the substrate at a rate which is about four to five times that of the rate at which ions strike substantially planar surfaces (e.g., surfaces laying substantially perpendicular to the ion emission source) on the substrate. In fact, with facet etching, the planar surfaces experience very little substrate loss. The facet etch creates a gradual slope of about 45 degrees at the comers of the structures on the substrate.

[0013] The facet etch is preferably performed in a reactive ion etcher wherein the substrate is placed on a cathode within a high-vacuum chamber into which etchant gases are introduced in a controlled manner. A radio frequency power source creates a plasma condition in the high-vacuum chamber which generates ions. The walls of the high-vacuum chamber are grounded to allow for a return radio frequency path. Due to the physics of the radio frequency powered electrodes, a direct current self-bias voltage condition is created at the substrate location on the cathode, which causes the generated ions in the plasma to accelerate toward and strike the substrate. The etchant gases utilized in the facet etch are preferably inert gases, including, but not limited to, helium, argon, krypton, and xenon. These inert gases have been found to enhance the uniformity of the facet etch process. It is, of course, understood that any other suitable gas or mixture of gases which are inert with respect to the material of the substrate may also be used.

[0014] Thus, the present invention eliminates the use of isotropic etching to form field emission tips and, thereby, eliminates the problems associated with isotropic etching. Although the present invention requires more steps than the typical isotropic etching technique of forming field emission tips, the methods of the present invention result in more uniform distribution, size, and height for the field emission tips, since the location and size of the etch mask elements defining the tip locations, as well as the depth of the anisotropic etch, can be precisely controlled. This precise control results in a field emission tip array having regular uniform tip spacing as well as precise, uniform tip height, thus improving the performance and reliability of the field emission display device formed therefrom. Furthermore, the precise control of the tip spacing allows the tips to be packed closer to one another, which results in a higher fidelity screen with more pixels per square inch.

[0015] The present invention also allows for low work function materials to be easily incorporated into the field emission tips. The overall work function of a field emission tip affects its ability to effectively emit electrons. The term “work function” relates to the voltage (or energy) required to extract or emit electrons from a field emission tip. The lower the work function, the lower the voltage required to produce a particular amount of electron emission. Thus, the incorporation of low work function materials in field emission tips can substantially improve their performance for a given voltage draw.

[0019] Thus, the present invention allows for easy incorporation of a variety of materials on top of the field emission tips to improve their performance.

Problems solved by technology

Although the method taught in the Kumar patent eliminates the use of an isotropic etch to form field emission tips, it lacks control over the field emission tip distribution and dimensions.

The discontinuous layer of etch mask material results in a nonuniform distribution of field emission tips, since the positions of the openings in the discontinuous layer cannot be controlled.

Furthermore, the discontinuous layer of etch mask material results in nonuniform dimensions between the field emission tips, since the thickness difference across the discontinuous layer cannot be controlled.

Moreover, since the etch mask material is a discontinuous layer rather than a patterned mask, the size or diameter of the field emission tips formed cannot be controlled.

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