KR100621293B1 - Impedance-assisted electrochemical technique and electrochemistry for removing material, particularly excess emitter material in electron-emitting device - Google Patents

Abstract

The impedance utilizing (supporting) electrochemical process of the present invention is characterized in that it is used to selectively remove certain materials without significant electrochemical erosion, i.e., substantial removal of certain other materials of the same chemical type as the removed material.

Description

IMPEDANCE-ASSISTED ELECTROCHEMICAL TECHNIQUE AND ELECTROCHEMISTRY FOR REMOVING MATERIAL, PARTICULARLY EXCESS EMITTER MATERIAL IN ELECTRON-EMITTING DEVICE}

The present invention provides a method of removing unnecessary portions of a material from a partially completed structure without removing the necessary portions of the same type of material, in particular products such as flat panel cathode ray tube (CRT) displays. The present invention relates to a method for removing unnecessary portions from an electron-emitting device, commonly referred to as a cathode.

Field emission cathodes (or field emitters) comprise a group of electron-emitting devices that emit electrons when an electric field of sufficient strength is applied. The electron-emitting device is generally located on a patterned layer of emitter electrodes. In gated field emitters, the patterned gate layer is generally located above the patterned emitter layer at the location of the field emitter. Each electron-emitting device is exposed through an opening in the gate layer. When an appropriate voltage is applied between the selected portion of the gate layer and the selected portion of the emitter layer, the gate layer extracts electrons from the electron-emitting device at the intersection of the two selected portions.

The electron-emitting device usually has a conical shape. 1A-1D illustrate a conventional method as disclosed in a number of US Pat. Nos. 3,755,704 granted to Spindt et al. For forming conical electron-emitting devices in gated field emitters for flat panel CRT displays. Doing. In the step shown in FIG. 1A, the partially completed field emitter consists of an electrically insulating substrate 20, an emitter electrode layer 22, an intermediate dielectric layer 24, and a gate layer 26. Gate opening 28 extends through gate layer 26. Thus, the slightly wider dielectric opening 30 extends through the dielectric layer 24.

Using a grazing-angle deposition process, a liftoff layer 32 is formed on top of the gate layer 26 as shown in FIG. 1B. The emitter material is deposited in the top of the structure and in the dielectric opening 30 in such a way that the aperture through which the emitter material enters through the opening 30 is gradually sealed. In US Pat. No. 3,755,704, the closure material is deposited simultaneously at a grazing angle to help seal the deposition aperture. Thus, generally conical electron-emitting device 34A is formed in composite opening 28/30 on emitter layer 22. See FIG. 1C. A continuous layer 34B of emitter / sealing material is formed on top of the gate layer 26. The liftoff layer 32 is then removed to lift off the excess emitter / sealing material layer 34B. 1D shows the finally obtained structure.

Using the liftoff layer 32 to remove the excess emitter / sealing material layer 34B is not good for several reasons. The lift-off material portion is constantly accumulated along the side ends of the gate layer 26. This reduces the size of the opening where the emitter material is initially deposited and makes it difficult to make the scale of the electron-emitting device 34A small. Gradient deposition of the liftoff layer 32 becomes increasingly difficult as the edge region of the field emitter increases, thus impeding the scale of the field emitter region to increase.

Liftoff material deposition must be performed carefully to ensure that no liftoff material accumulates on the emitter layer 22 and does not allow the conical electron-emitting device 34A to lift off during the liftoff of the excess layer 34B. do. Since layer 34B is removed as a sacrificial layer of liftoff layer 32 removal, the particles of emitter material removed may contaminate the field emitter. In addition, deposition of the liftoff material requires processing time and hence cost.

Wilshaw's PCT patent application WO96 / 06443 discloses a process for producing a gated field emitter in which each electron-emitting device consists of molybdenum cones positioned on a cylinder. The electron-emitting device is formed on the bottom metal layer. Using an aqueous electrolyte solution, Wilshaw used 2-4 volts on the niobium gate layer to electrochemically remove the excess molybdenum layer that accumulates on the gate layer during the deposition of molybdenum through the opening in the gate layer to form the cone of the electron-emitting device. Was applied.

Just before electrochemically removing excess molybdenum, Wilshaw removed the bottom metal layer. Thus, Wilshaw's electron-emitting devices are electrically insulated from one another during the electrochemical removal of excess emitter material. Since some electron-emitting devices may be electrically shorted to excess molybdenum during the electrochemical removal step, Wilshaw needed this insulation to protect the unshorted electron-emitting devices, which would otherwise cause the un-shorted electron-emitting devices to short-circuit. This could be due to electrical shorts with excess molybdenum through the device and backside metal layer and thus electrochemically eroded when removing the excess molybdenum. Wilshaw then operated on the back to negate the presence of the shorted electron-emitting device. Finally, Wilshaw formed a resistive layer on the bottom of the electron-emitting device and an emitter electrode layer on the resistive layer.

Wilshaw's electrochemical removal method did not require the use of a liftoff layer to remove the excess emitter material layer. However, removing the backside metal layer before the electrochemical removal of excess molybdenum and creating the emitter electrode after the completion of the electrochemical removal was time consuming and required several complex process steps. In addition, performing additional electro-short invalidation operations increases process time and complexity. When fabricating a gated field emitter having an electron-emitting device formed at least partially conical, a layer comprising excess emitter material without incurring the process difficulties associated with using Wilshaw's process inefficiency or the liftoff layer. There is a need for a method for removing this.

The use of an aqueous electrolyte solution to remove Wilshaw's excess molybdenum is difficult. The high charge-to-radius values of metal ions such as molybdenum (typically ionic charge state of +6) are readily available from aqueous solutions as metal hydroxides, metal oxides, and / or metal hydroxides. Precipitate the metals. The precipitate coats the electron-emitting device and destroys its usefulness. Wilshaw's electrochemical removal potential of 2-4 volts, which overcomes the precipitation problem without causing electrochemical removal of niobium in the gate layer, is very high and can cause significant electrochemical erosion to many other very interesting candidate materials for gate metals. have. There is a need for an easier and more flexible way to overcome unwanted precipitation.

The present invention provides an efficient and relatively simple electrochemical process for selectively removing certain materials from a structure without large electrochemical erosion and without large removal of certain other materials of the same chemical type as the removed material. The electrochemical removal process of the present invention typically utilizes impedance. The present invention also provides an organic based electrochemistry for the electrochemical removal process.

Impedance utilization (support) in the electrochemical removal method of the present invention is generally realized with an impedance component that forms a permanent component of the structure and is present in the structure, at least during the electrochemical removal operation. Impedance components have properties designed to overcome electrical short-circuit problems that occur when one or more portions of the material remaining in the structure are electrically connected with the material to be removed. Due to the presence of an impedance component, each of these electrical shorts typically recovers automatically (ie, is removed) during electrochemical removal without reducing the selectivity of the removal. The liftoff layer need not be used at all when electrochemically removing the material according to the invention. When the electrochemical method of the present invention is used to remove excess emitter material that accumulates on the control electrode of the electron emitter during deposition of the emitter material through an opening in the control electrode at least partially to form an electron emitting device, The emitter electrode located below the emitting element can remain intact during electrochemical removal. Unlike Wilshaw's method, it is not necessary to remove the lower electrically conductive layer before performing electrochemical removal to ensure that the electron-emitting device is electrically insulated during the removal operation and basically to form a replacement emitter electrode after removal.

Also unlike Wilshaw's method, there is no need to perform complicated operations to repair electrically shorted electron-emitting devices. In the present invention, the number of process steps can be reduced, thereby saving process time and cost.

The present invention alleviates the problems created when the electron-emitting device is reduced and the edge area of the electron emitter is enlarged by using the lift-off layer. The use of the lift off layer eliminates the possibility of unintentionally lifting off the electron-emitting device. In addition, the present invention avoids the problem of emitter material particulate contamination that can occur with the use of liftoff layers. Thus, the present invention allows the manufacture of the electron-emitting device to be completed in an efficient and economical way.

The first step in the electrochemical removal process of the present invention is to provide an initial structure comprising a first electrically non-insulated region at least partially composed of a first material. As will be described later, "non-electrically insulating" means electrically conductive or electrically resistive. The first non-insulating region can be, for example, an excess emitter material layer that accumulates during deposition of the emitter material to form an electron emitting device.

When the electrochemical removal process uses impedance, the initial structure includes an impedance component (consisting of one or more impedance elements) electrically connected to a plurality of electrically non-insulating members such as electron emitting devices. Each non-insulating member is at least partially composed of a first material, such as a first non-insulating region. Electrodes, such as emitter electrodes, are generally electrically connected to non-insulating members through impedance components. Although not intended, a small portion of the non-insulating member may short-circuit with the non-insulating region at this point and / or short with the non-insulating region during the electrochemical removal operation of the present invention.

With the initial structure so arranged, at least a portion of the first material of the first non-insulated region is electrochemically removed by applying a selected potential to the non-insulated region. The removal step typically includes immersing the initial structure in an electrolyte solution, preferably an electrolyte solution containing an organic solvent and an acid. During the removal step, the impedance component has a sufficiently high impedance so that the first material of each non-insulating member that is not shorted to the non-insulating region is not significantly eroded.

In particular, selecting the impedance element to be sufficiently high impedance allows the non-shorted non-insulated member to be electrically electrically isolated from any non-insulated member shorted to the first non-insulated region. The potential applied to the non-insulated region to electrochemically remove the selected potential, ie, the first material of the non-insulated region, is not transferred to the uninsulated non-insulated member. Therefore, the non-shorted non-insulated member does not erode significantly electrochemically as a result of applying the selected potential to the non-insulated region.

Importantly, the first material of any shorted non-insulating member is substantially eroded during the electrochemical removal process. Erosion ends when enough first material has been removed to remove the short. Thus, a short between the first non-insulating region and any non-insulating member is automatically recovered by the present invention without the need for the removal of the underlying electrode or impedance component. Depending on how much of the first material of the non-insulating member remains, the recovered non-insulating member can perform the intended function.

When the organic based electrochemistry of the present invention is used in the electrochemical removal process of the present invention, a plurality of non-insulating members can be simply replaced with a second electrically non-insulating region composed of at least part of the first material together with the impedance component. It may be. The second non-insulating region is generally an electron emitting device. Similar to the above, at least a portion of the first material of the first non-insulated region is now electrically prepared by contacting the first solution of the first non-insulated region with an electrolyte solution containing an organic solvent and an acid. Chemically removed. The removal process is performed such that the first material of the second non-insulated region is not significantly eroded during the removal step.

The use of organic solvents in the electrolytic solution of the present invention, as used by Wilshaw, offers many advantages over electrolytic solutions where water is a solvent. Electrolysis-output ions of metals such as molybdenum, which are particularly suitable for electron-emitting devices but have high ionic radius charge ratio values, typically have high solubility in organic solvents. Compared with Wilshaw's aqueous electrolyte solution, the problem of metal precipitation is significantly reduced with the organic solvent used in the present invention. While avoiding unwanted precipitation, there is no need to use excessively high electrochemical removal potentials that significantly limit the choice of material for the gate or control electrode.

Electrochemical removal can be performed considerably faster in electrolytic solutions using organic solvents than in aqueous electrolyte solutions. In particular, electrolysis proceeds faster at high temperatures due to increased reaction rates, high ion mobility, and reduced electrolyte viscosity. By appropriately selecting the organic solvent used in the electrolytic solution of the present invention, the organic solvent can have a higher boiling point than water. Thus, electrolysis can be carried out at higher temperatures in the electrolytic solution of the invention than in aqueous solutions. Since higher temperatures allow for faster electrolysis, the process time is reduced in the electrolytic solution of the present invention.

The solubility of the electrolysis reaction product is increased at high temperatures. This factor, combined with greater metal-ion solubility in organic solvents than in water, results in increased lifetimes for the electrolytic solutions of the present invention. The manufacturing cost is further reduced in the present invention.

The acid used in the electrolytic solution of the present invention is generally an organic acid as described above. Preferably, the organic acid is formed of sulfur containing acid. In addition, the electrolytic solution generally contains a salt, typically an organic salt.

In summary, the electrochemistry provided by the present invention is particularly useful in the step of selectively removing material from one part of a structure while preventing the same chemical type of material from being removed from another part of the structure. The removal operation is processed in a fast, efficient and uncomplicated way. Certain types of electrical shorts are automatically repaired in the present invention. It is not necessary to remove the impedance element or, if present, the emitter electrode before performing the electrochemical removal. In addition, no lift-off layer is required. Thus, the present invention provides a significant advance over the prior art.

1A-1D are structural cross sectional views showing steps of a prior art process for generating an electron-emitting device in an electron emitter;

2A-2C are cross-sectional views illustrating the steps of a process sequence in accordance with the electrochemical method of the present invention for producing conical electron-emitting devices in a gated field emitter;

3A-3B are schematic cross-sectional views illustrating two implementations of the potentiostat electrochemical system used in the process of FIGS. 2A-2C;

4A-4B are graphs of cell current as a function of drive voltage for electrochemically removing a particular metal in a electrolytic device electrochemical system of the type shown in FIG. 3A or 3B;

5A-5D are structural cross-sectional views illustrating implementation steps of the process sequence of FIGS. 2A-2C;

6A-6B are layout views of the respective structures of FIGS. 5C and 5D, and those obtained on plane 5c-5c of FIG. 6A are cross-sections of FIG. 5C, and those obtained on plane 5d-5D of FIG. 6B,

7 is a cross-sectional structural view of a structure produced according to another embodiment of the process sequence of FIG.

8a-8d illustrate cross-sectional views of emitter impedance components in field emitters manufactured according to the process of FIGS. 2A-2C or 5A-5D;

9 is a structural cross-sectional view of a flat panel CRT display device including a gate type field emitter having an electron-emitting device manufactured according to the present invention.

Like reference numerals have been used in the description and the drawings of appropriate embodiments to indicate the same or very similar item (s).

The present invention utilizes an impedance utilizing electrochemical method to remove excess emitter material when creating an electron emitting device for a gated field emission cathode. Each electric field emitter is suitable for exciting a phosphor region in a faceplate in a cathode ray tube of a flat panel display such as a flat panel television or a flat panel video monitor for a PC, a laptop computer, or a workstation.

In the following description, the term "electrical insulation" (or "dielectric") generally applies to materials having resistivities greater than 10 ¹⁰ kPa-cm. The term "electrically non-insulating" thus refers to a material having a resistivity of less than 10 ¹⁰ kPa-cm. The electrically non-insulating material is divided into (a) an electrically conductive material having a resistivity of less than 1 kV-cm and an electrically resistive material having a resistivity in the range of 1 kV-cm to 10 ¹⁰ kPa-cm. This category is determined at electric fields below 1 volt / μm.

Examples of electrically conductive materials (or electroconductors) include metals, metal-semiconductor compounds (such as metal silicides), and metal-semiconductor eutectics. Electrically conductive materials also include semiconductors that are doped at intermediate or high levels (n-type or p-type). Electrically resistive materials include intrinsic and lightly doped (n-type or p-type) semiconductors. Additional examples of electrically resistive materials include (a) metal-insulator composites such as cermet (ceramic embedded with metal particulate), (b) graphite, amorphous carbon, and modified (eg doped, or laser). Carbon modified such as -modified) diamond, and (c) specific silicon-carbon compounds such as silicon-carbon-nitrogen.

For convenience, the potential value generated when performing the electrochemical removal method of the present invention is defined based on the standard hydrogen electrode rating of the International Union of Pure and Applied Chemists. This standard is referred to herein as a normal hydrogen electrode.

2A-2C (collectively "FIG. 2") illustrate a method in which an electrochemical method using impedance is used in accordance with the present invention to remove excess emitter material during generation of an electron-emitting device for a gated field emitter. have. The starting point in the process of FIG. 2 is an electrically insulating substrate 40 formed generally of ceramic or glass. See FIG. 2A. The substrate 40, which provides the support for the field emitter, consists of a plate. For example, the substrate 40 generally consists of a Schott D263 glass plate having a thickness of about 1 mm. In a flat panel CRT display, the substrate 40 constitutes at least part of the backplate.

Emitter region 42 is positioned over substrate 40. The emitter region 42 consists of (a) a lower electrically conductive layer (A) patterned with an emitter electrode and (b) an upper emitter impedance component 42B. Emitter electrode layer 42A is positioned on top of substrate 40. Emitter electrode layer 42A generally extends substantially parallel to each other in the direction of the column of screen components (pixels) in the CRT flat panel display to form a row electrode. Layer 42A generally consists of a metal such as nickel or aluminum. The thickness of layer 42A is 100-500 nm, generally 200 nm.

Emitter impedance component 42B lies on top of emitter electrode layer 42A. At least, the impedance component 42B needs to be under each electron-emitting device. Component 42B need not be present in a location without an electron emitting device thereon.

Impedance component 42B can be constructed and formed in a variety of ways. For example, impedance component 42B generally consists of a blanket layer of one or more electrically resistive materials. Component 42B may also be formed of one or more patterned layers of electrically resistive material. When component 42B is formed of an electrically resistive material, emitter region 42 becomes an electrically non-insulating region. Other examples of the construction and formation of the impedance component 42B are described below. The thickness of the impedance component 42B depends on how the component 42B is implemented to obtain its own impedance value and the required impedance value.

An electrical insulating layer 44 used as an inter-electrode insulator (dielectric) is provided on top of the structure. The thickness of the insulating layer 44 is typically in the range of 0.05-3 μm. More specifically, layer 44 has a thickness of 100 nm-500 nm, generally 150 nm. The insulating layer 44 is generally composed of silicon oxide or silicon nitride. Although not shown in FIG. 2A, some of the insulating layer 44 may contact the substrate 40, depending on the shape of the impedance component 42B.

A patterned electrically non-insulated gate layer 46 composed of the selected gate material is positioned on the inter-electrode insulator layer 44. Gate layer 46 typically has a thickness in the range of 30-500 nm. More specifically, the gate thickness is 30-100 nm, generally 50 nm. The gate material is typically a metal, preferably chromium and / or nickel. Alternative candidates for gate materials include molybdenum, platinum, niobium, tantalum, titanium, tungsten, and titanium-tungsten.

The gate layer 46 can be patterned in a variety of ways. For example, the gate layer 46 may be formed of a plurality of control electrodes that are substantially parallel to control electron emission from the electron-emitting device. Layer 46 generally forms part of a group of control electrodes having a main control portion (not shown herein) in contact with a portion of layer 46 and extending substantially horizontally to each other. In either case, the control electrode constitutes a column electrode extending perpendicular to the column electrode of the emitter layer 42A and thus extending along the column of pixels.

A number of nearly circular openings 48 extend through the gate layer 46. The diameter of the gate opening 48 depends on how the opening 48 is created, but the gate opening diameter is typically in the range of 0.05-2 μm. More specifically, the gate opening diameter is 80-400 nm, generally 150 nm.

A plurality of substantially circular dielectric openings (or dielectric openings) 50 extend through the insulating layer 44 below the impedance component 42B of the emitter region 42. Each dielectric opening 50 is arranged perpendicular to the corresponding one of the gate openings 48 to form a composite opening 48/50 that exposes a portion of the impedance component 42B. Each dielectric aperture 50 is slightly wider than the corresponding gate aperture 48. Thus, insulating layer 44 undercuts gate layer 46 along composite opening 48/50.

Various methods can be used to form the composite opening 48/50 in the layers 44, 46. For example, openings 48/50 generally etch gate layer 46 through apertures in the photoresist mask to form gate openings 48, and then to create dielectric apertures 50. It may be produced by etching the insulating layer 44 through the opening 48. Composite openings 48/50 may also be created using etched charged-particle tracks as described in PCT patent application WO95 / 07543 to Macaulay et al.

Selective etching or micromachining methods of the type disclosed in US Pat. No. 3,755,704, described above, may be used to form the composite opening 48/50. Subject to their names and their respective materials, the openings 48/50 are described in Spindt et al., "Research in Micron-Size Field-Emission Tubes," ( IEEE Conf. Rec. 1966 Eighth Conf. On Tube Techniques , 1996.9. 20, pages 143-147).

The electrically non-insulating emitter conical material is deposited by evaporation on top of the structure in a direction substantially perpendicular to the top surface of insulating layer 44 (or gate layer 46). Emitter conical material accumulates on the gate layer 46 and passes through the gate opening 48 to accumulate on the impedance component 42B in the dielectric aperture space 50. Due to the accumulation of conical material on the gate layer 46, the opening through which the conical material enters the opening space 50 is gradually closed. Deposition is performed until the opening is completely closed. As a result, conical material is accumulated in the dielectric aperture 50 to form the corresponding conical electron-emitting device 52A as shown in FIG. 2B. A continuous (blanket) layer 52B of conical material is formed simultaneously on the gate layer 46.

The emitter conical material is typically metal, preferably molybdenum when the gate layer 46 is chromium and / or nickel. Alternative candidates for conical materials include nickel, chromium, platinum, niobium, tantalum, titanium, tungsten, titanium-tungsten, and titanium carbide, subject to gate materials and other conical materials.

Using a suitable photoresist mask (not shown), one or more portions of excess emitter-material layer 52B along the edge of the partially completed field emitter are removed. Thus, a portion of the main control and / or a portion of the gate layer 46 in contact with the gate layer 46 (if present) is exposed along the perimeter of the field emitter. The interior and / or (if present) main portion of the selected gate layer 46 is also generally exposed during the masked etch.

The electrochemical removal operation is now carried out on the etched structure as in FIG. 2B using a electrolytic device electrochemical system of the type schematically shown in FIG. 3A. Reference numeral 52C in FIG. 3A is a portion of excess emitter-material layer 52B remaining after the masked etching described in the preceding paragraph. Excess emitter-material layer 52C is removed during the electrochemical operation.

A small portion of the conical electron-emitting device 52A is electrically shorted with gate layer 46 and / or electrically with gate layer 46 during the electrochemical removal operation prior to electrochemical removal of excess layer 52C. Short circuit. Since the excess layer 52C contacts the gate layer 46, both of the electron emission cones 52A are shorted to the excess layer 52C and generally eroded significantly during removal as described below. The remaining cone 52A, that is, the cone 52A that is not shorted with the layer 52C, does not erode significantly as the layer 52C is removed. Similarly, the electrochemical removal operation (if present) is performed without substantially eroding the main portion of the control electrode and the patterned gate layer 46.

The electrochemical removal system is formed of a control system 62 and an electrochemical cell 60 in the form of a potentiostat that controls cell operation. The electrochemical cell 60 is composed of an electrolytic solution 64, a battery wall 65, a counter electrode 70, and a reference electrode 72. The partially completed field emitter is immersed in electrolytic solution 64.

Generally, the platinum-plated titanium or platinum counter electrode 70 is immersed in the electrolytic solution 64 and extends horizontally with the excess emitter material layer 52C. A reference electrode 72, generally made of silver / silver chloride or mercury / mercury chloride (magenta), is located in solution 64 close to layer 52C, and preferably close to excess emitter material layer 52C.

The control system 62 has a working electrode terminal WE, a reference electrode terminal RE, and a counter electrode terminal CE. The cell 60 is electrically connected to the control system 62 by an operating electrode conductor 73, an electrically insulated reference electrode conductor 74, and a counter electrode conductor 76. Conductors 73, 74, and 76 are all generally comprised of platinum wire or electrically insulating copper wire.

The operating electrode conductor 73 is electrically connected to the control electrode. When layer 46 is patterned with a control electrode or (if present) by the main control portion of the control electrode, the connection is directly connected with gate layer 46 as shown in FIG. 3A. Since the gate layer 46 is in contact with the excess emitter material layer 52C, the combination of the layers 46 and 52C with the main control portion forms an operational anode electrode for the battery 60. The reference electrode conductor 74 is electrically connected to the reference electrode 72. The counter electrode conductor 76 is electrically connected to the counter electrode 70.

The electrochemical cell 60 is operated in a potential electrolytic device (constant potential) mode. Reference electrode 72 provides a reproducible fixed reference potential V _R. When electrode 72 is a silver / silver chloride reference electrode, the reference potential V _R is about 0.2 volts relative to the standard hydrogen electrode at room temperature.

The control system 62 operates the operating electrode conductor at a substantially constant operating electrode drive potential V _WE that exceeds the normal reference potential V _R on the reference electrode conductor 74 by a substantially fixed anode potential V _A. It acts as a potential electrolytic device for positioning (73). Under some operating conditions, the anode potential can be negative to allow the working electrode drive potential V _WE to be less than V _R. In FIG. 3A, the potential V _A is schematically shown to be provided by the voltage source 62A in the potential control system 62. The driving potential V _WE is equal to V _A + V _R based on the standard hydrogen electrode. To dissolve excess emitter material during the electrochemical removal process, the potential V _WE is controlled by the conductor 73 and the control electrode (composed by the coupling of the gate layer 46 or the main control portion adjacent to the gate layer 46). It is applied to the excess layer 52C through.

The control system 62 makes the counter electrode conductor 76 nearly constant counter electrode potential V _CE . The reference potential V _R exceeds the counter electrode potential V _CE by a substantially fixed counter potential V _C. In FIG. 3A, the counter potential V _C is schematically shown to be supplied by the voltage source 62C in the control system 62. The counter electrode potential V _CE is equal to V _R -V _C.

The potential on the emitter electrode layer 42A can be treated in any of three ways, all of which result in (a) the excess emitter material layer 52C being electrochemically removed, and (b) Any shorted cone 52A generally erodes sufficiently to recover the short, but unshorted cone 52A does not erode significantly.

First, the potential on the emitter electrode layer 42A can be left unregulated. That is, no action is taken to control the potential of layer 42A. Depending on the material comprising any shorted cone 54A and electrically connected to layer 42A, the potential on layer 42A is controlled by gate layer 46, excess layer 52C, and (if present). A value close to the driving potential V _WE on the working electrode formed by each main control portion of the electrode can be reached. In order to prevent large erosion of the unshorted cone 52A during electrochemical removal of the excess layer 52C, the minimum value of the impedance provided by the impedance element 42B regulating the potential on the layer 42A is three different ways. This is the highest value generated by.

Secondly, the emitter electrode layer 42A may be magnetically biased to a negative potential electrolytically with respect to the potential V _WE . The emitter electrode magnetic bias method is realized by appropriately selecting an electrically non-insulating material electrically connected with the electron emission cone 52A and in contact with the electrolytic solution 64. The non-insulating material consists of an impedance component 42B, an emitter electrode layer 42A, and a material that forms additional metal regions (not shown) that provide external electrical connection with the layer 42A. Because cone 52A is electrically connected to emitter electrode layer 42A through impedance component 42B, cone 52A is at a negative potential with respect to the working electrode.

Third, the emitter electrode layer 42A can be kept active at a substantially constant emitter electrode potential V _{EE that} is lower than the working electrode potential V _WE . For this purpose, the nearly fixed emitter potential V _E is provided by a voltage source 77 connected between the additional electrical conductor 79 and the working electrode conductor 73 connected to the emitter electrode layer 42A. . Since the voltage source 77 and the additional conductor 79 are optional, they are indicated by dashed lines in FIG. 3A. The emitter electrode potential V _EE is equal to V _WE -V _E. Since the working electrode potential V _WE is equal to V _A + V _R , the potential V _EE is also equal to V _A + V _R -V _E.

In the third method, when there is no large current flow through the emitter electrode layer 42A, the cone 52A is usually close to the emitter electrode potential V _EE , thus becoming almost V _{E which} is lower than V _WE . The magnitude of the emitter potential V _E should not be so large that the emitter material of the excess layer 52C will cover the cone 52A during the electrochemical removal of the excess layer 52C.

With respect to the reference voltage V _R , the arrangement of the voltage source supplying the potential V _WE and the potential V _CE to the electrochemical cell 60, if used, the potential V _EE is a desired value of the potential V _WE. , V _CE , V _EE ) can be varied as long as it can be obtained. FIG. 3B illustrates an alternative method of setting up the electrochemical removal system of FIG. 3A. The electrochemical cell 60 of FIG. 3B has an edge wall 66 and an O-ring 68 instead of the cell wall 65. The electrolytic solution 64 contacts only the top of the field emitter of FIG. 3B. O-ring 68 prevents solution 64 from leaking out of cell 60 at the bottom of wall 66.

In the alternative electrochemical system of FIG. 3B, the working electrode conductor 73 and the additional conductor 79 (if used) make an electrical connection to the exterior of the cell 60. The optional voltage source 77 is electrically connected to the counter electrode conductor 76 instead of the working electrode conductor 73. To at substantially the same value in both the electrochemical removal system the emitter electrode potential (V _EE) so that already provided by emitter electrode layer (42A), the potential (V _E) of Figure 3a is the potential (V _E) of Figure 3b The value is different.

The emitter materials of the excess layer 52C and cone 52A consist almost of refractory metals, such as molybdenum, whose ions have high radial charge ratios (i.e., essentially high valences for metal ions of near-average radius). In this case, the electrolyte solution 64 is formed of an organic solvent and an acid electrolyte. The organic solvent in the electrolytic solution 64 is composed of a polar organic solution at room temperature. In the case of molybdenum, examples of suitable organic solvents for the solution 64 are dimethyl sulfoxide ("DMSO"), ethanol, and methanol. The highly charged molybdenum ions (Mo ⁶⁺ ) produced by electrolysis in solution 64 dissolve very well in each of these solvents.

The acid electrolyte in solution 64 may be an inorganic or organic acid. In general, acids become sulfur-containing acids because sulfur-containing acids have high disassociation constants for high reaction rates. Examples of suitable sulfur-containing inorganic acids are sulfuric acid, sulfuric acid, and sulfamic acid. In the case of organic acids, sulfur-containing acids are usually sulfonic acids and are generally aromatic sulfonic acids, in particular aromatic sulfonic acids with benzene rings. An example of a suitable aromatic sulfonic acid having a benzene ring is paratoluenesulfonic acid ("p-TSA").

The electrolyte solution 64 may also contain an organic or inorganic salt electrolyte. Since organic salts generally dissolve better in organic solvents, electrolyte salts usually become organic salts. In particular, organic salts generally become aromatic sulfonates and especially those having benzene rings. Examples of suitable sulfonates having a benzene ring are tetraethylammonium paratoluenesulfonate ("TEAp-TS"), tetramethylammonium paratoluenesulfonate, and tetrabutylammonium paratoluenesulfonate.

Where present, the main control portion of the control electrode and the material of the patterned gate layer 46 consist essentially of chromium and / or nickel, while the emitter material of the excess layer 52C and cone 52A is basically Preferred examples of the electrolytic solution 64 when composed of molybdenum are:

a. DMSO ((CH ₃ ) ₂ SO) as an organic solvent,

b. P-TSA at a molar concentration (moles / liter) of 0.1-1.5, preferably 0.5, and

c. TEAp-TS (N (CH ₂ CH ₃ ) ₄ CH ₃ C ₄ H ₄ SO ₃ ) at a molar concentration of 0.05-0.75, preferably 0.1.

At the appropriate 0.5-mole p-TSA and 0.1-mole TEAp-TS values, the voltage source 62A in the control system 60 is the global drive potential in the range of 0.2-0.9 volts, typically 0.6 volts, for a standard hydrogen electrode. Set the anode potential (V _A ) to an appropriate value to fix (V _WE ). When voltage source 77 is used in the electrochemical system of FIG. 3A with a potential V _WE at a typical 0.6 volt value, emitter potential V _E is already at this V _E value lower than the operating electrode potential V _E. To set the emitter electrode potential (V _EE ), 0.4–2.4 volts, typically 0.5 volts.

DMSO has a boiling point of nearly 190 ° C. Thus, electrolysis using the solution 64 of the above example can be carried out at a temperature above the boiling point of 100 ° C. of water. The removal rate of the excess emitter material layer 52C is very high. Since DMSO is flammable, electrolysis is carried out at a safe temperature below the DMSO boiling point. Using DMSO as the solvent, electrochemical removal is usually carried out at 20-120 ° C., generally 40-60 ° C.

By operating the electrochemical cell 60 under the above conditions, the driving force provided by the anode drive potential V _WE causes the molybdenum in the excess emitter-material layer 52C to oxidize to the anode, thereby allowing the electrolyte to oxidize in the electrolyte solution 64. In general, to dissolve in Mo ⁶⁺ ions. Thus, excess layer 52C is electrochemically removed from the top of the structure. The p-TSA is used to adjust the rate at which molybdenum in excess layer 52C is oxidized and removed from the field emission structure. Increasing the p-TSA concentration increases the rate at which molybdenum in layer 52C is oxidized at a given value of potential V _WE , and vice versa. Hydrogen ions (H ⁺ ) are reduced at the counter electrode 70 to produce hydrogen gas.

As noted above, a small portion of the electron emission cone 52A is electrically shorted with the excess emitter-material layer 52C either directly or through the gate layer 46. Such electrical shorts generally occur as a result of the cone 52A being forced to contact the gate layer 46, or as a result of the presence of one or more electrically conductive particles between the cone 52A and the layer 46 or 52C. do. The conductive fine particles are generally composed of emitter conical material separated from the excess layer 52C.

Each cone 52A shorted to excess layer 52C receives a working-electrode potential V _WE . When the two meters electrode layer (42A) is maintained in activity by selective voltage source 77 is at a low potential (V _EE) than the self-bias or V _WE at a potential lower than V _WE, and the emitter electrode potential for electrochemical removal operation The difference between the potentials V _WE drops greatly across the portion of the impedance component 42B that is under the shorted cone 52A. Thus, each shorted cone 52A is contaminated with the remainder of the excess layer 52C and at the time until a sufficient amount of emitter material is removed from the excess layer 52C and the cone 52A. It is electrochemically eroded until a moderately wide gap is formed between any remaining portions of 52A). If the gap reaches the width where the potential on cone 52A originally shorted falls below the value required to electrochemically remove material, the erosion on cone 52A is terminated.

When only a relatively small portion of the cone 52A is removed, the electrochemical erosion on the shorted cone 52A sometimes ends. Depending on how much of the pre-shorted cone 52A remains and what the remaining portion looks like, the remaining portion of the cone 52A can function properly as an electron-emitting device. In any case, the short circuit between cone 52A and excess layer 52C is removed (recovered) by using the present electrochemical process to remove layer 52C.

At the current and potential present during electrochemical removal of the excess emitter material layer 52C, the impedance of the impedance component 42B is sufficiently high that both the excess emitter-material layer 52C and the unshorted cone 52A It is effectively electrically insulated from each other, in particular from any cone 52A shorted to the excess layer 52C. In particular, the unshorted cone 52A allows the electrons generated during the oxidation of the cone material to pass through the gate layer 46, excess layer 52C, main portion (if present), and any shorted cone by the current path. Electrochemical erosion can only occur if there is a current path that can reach a portion of the extended working electrode formed by 52A. The impedance of the high component 42B during the electrochemical removal operation virtually closes any current path from the unshorted cone 52A to the shorted cone 52A through the emitter electrode layer 42A.

Depending on how close the potential on the emitter electrode layer 42A can be to the driving potential V _E , a cumulative short circuit of 1-2% of the shorted cone 52A, for example 1-2% of the total cone 52A Impedance of component 42B is controlled such that the current is insufficient to remove a substantial amount of material from cone 52A that is not shorted. Typically, there is no significant current path outside of each shorted cone 52A for carrying the current required to electrochemically erode the unshorted cone 52A. Thus, substantially no chemical activity occurs on the surface of the unshorted cone 52A.

If the potential on the emitter electrode layer 42A is unregulated and potentially close to V _WE , the high impedance provided by the component 42B during the electrochemical removal operation may cause the electrochemical of the unshorted cone 52A to be shorted. It works primarily to prevent removal. Self-biasing or keeping layer 42A active at a moderate potential, typically about 0.5 volts below V _WE , provides electrolytic support to impedance component 42B when protecting the unshorted cone 52A. do. In summary, the use of a self-biased or active-potential-maintaining method makes it difficult for non-shorted cones 52A to reach potentials that can be electrochemically removed, easing the requirements for component 42B. In other words, the impedance of component 42B during the electrochemical removal operation may be slightly smaller than in the unregulated method.

Examples may be useful in understanding the present invention. When the impedance component 42B is made of an electrically resistive material, the component 42B is at least 10 ⁶ -10 ¹¹ Ω, typically between the emitter electrode layer 42A and each cone 52A during normal display operation. Provides an impedance of 10 ⁹ Ω (Z _B ). Component 42B is formed to provide an impedance Z _B with a significantly higher value during electrochemical removal of layer 52C. In particular, component 42B provides a high impedance to the (positive) current flow to the unshorted cone 52A. In an unregulated method, impedance Z _B is generally at least 10 ¹¹ Hz during removal of excess layer 52C. When a self bias or active-potential-maintaining method is used to maintain layer 42A at a potential lower than V _WE , the minimum value of impedance Z _B during electrochemical removal is determined by the number of shorted cones 52A and the electrical It depends on the nature of the chemistry.

In an electrochemical removal cell, the (positive) anode current (I _WE ) flowing through the working electrode represents the rate at which the material is electrochemically removed from the structure and drive potential immersed in the electrolytic solution. The removal rate typically increases with increasing anode current I _WE .

In the preferred 0.5-mol p-TSA and 0.1-mol TEAp-TS, the preferred V _WE potential ranges described above are the anode polarization curve (applied driving potential) for electrochemical cells formed to remove samples of molybdenum, chromium, and nickel, respectively. It was determined by experimentally monitoring the current (I _WE ) as a function of V _WE ). 4A shows that the removal rate in chromium and nickel is very small compared to the removal rate of molybdenum when the driving potential V _WE is in the range of 0.2-0.9 volts for the standard hydrogen electrode.

Electrolyte solution 64 using organic solvent when gate layer 46 and adjacent main control portion (if present) are made of chromium and / or nickel, while cone 52A and excess layer 52C are formed of molybdenum Another embodiment of:

a. Ethanol (CH ₃ CH ₂ OH) as a solvent, and

b, sulfuric acid (H ₂ SO ₄ ).

By selecting and using an appropriate molar concentration of sulfuric acid, excess layer 52C is generally electrochemically removed in the manner described above.

If the patterned gate layer 46 and (if present) the adjacent main control portion are formed of chromium or / and nickel, while the cone 52A and excess layer 52C are composed of molybdenum, the electrolytic solution 64 is:

a. Sodium hydroxide (NaOH) at a molar concentration of 0.005-0.05, generally 0.01, and

b. It may also be an aqueous solution containing sodium nitrate (NaNO ₃ ) at a molar concentration of 0.005-3.0, generally 2.0.

At typical 0.01-mol NaOH and 2.0-mol NaNO ₃ values, the anode potential (V _A ) is fixed at the cell drive potential (V _WE ) at values in the range of 0.6-1.0 volts, typically 0.8 volts, for a standard hydrogen electrode. Is set to an appropriate value by the control system 62. This range was determined experimentally by the method described above. The experimental results are shown in Figure 4b. The removal rates in chromium and nickel are very small compared to those in molybdenum when the drive potential V _WE is in the range of 0.6-1.0 volts, as shown in FIG. 4B.

Using electrochemical cell 60 operated in the main gun given in the paragraph above, excess layer 52C is electrochemically removed from the structure. The driving force provided by the anode potential V _WE oxidizes the molybdenum in the layer 52C and dissolves generally as Mo (VI) ions in the electrolyte solution 64. Sodium nitrate is used to coordinate molybdenum oxidation. NO ₃ ions produced by dissociation of NaNO ₃ act as oxidizing agents. Increasing the NaNO ₃ concentration increases the rate at which molybdenum in the layer 52C is oxidized, and vice versa. In addition, hydrogen ions are reduced to generate hydrogen gas at the count-electrode 70.

5A-5D (collectively "FIG. 5") show an embodiment of the process sequence of FIG. 2 in the case where the field emitters have respective electrically conductive main controllers in contact with the patterned gate layer 46. FIG. 5A illustrates one such main controller 80 extending perpendicular to the plane of the figure. The combination of the main control part 80 and a portion (s) of the gate layer 46 in contact with the main control part 80 forms the composite control electrode 46/80. One of the group of large control apertures 82 shown in FIG. 5A extends through each main controller 80. Each large control aperture 82 exposes a number of compound openings 48/50. The emitter electrode of the non-insulated region 42A of FIG. 5A extends horizontally in the plane of the figure.

The appearance of the partially completed field emission structure after deposition of blanket excess emitter material layer 52B and cone 52A is shown in FIG. 5B. In addition to contacting a portion of the gate layer 46 previously exposed through a large control aperture 82, the excess layer 52B is located above the main control portion 80 and a portion of the insulating layer 44.

5C shows the appearance of the structure after performing a mask etch to remove a portion of the excess emitter material layer 52B, including excess emitter material located along the side edges of the structure. The remainder of the excess layer 52B consists of a group of rectangular islands 52C located on the corresponding portion of the gate layer 46. The top view of FIG. 5C is shown in FIG. 6A. Each island is formed by using the same reticle to create a photoresist mask used to form excess emitter material island 52C as used when patterning the gate material to form patterned gate layer 46. The outer boundary of 52C is generally arranged perpendicular to the outer boundary of the portion underlying the gate layer 46.

5D shows the appearance of the structure after each island 52C has been electrochemically removed using the impedance support method of the present invention. As shown in FIG. 5D, gate layer 46 or main portion 80 is substantially not electrochemically eroded during removal of layer 52C. Similarly, the unshorted cone 52A does not erode significantly electrochemically during the removal operation, and the erosion on the unshorted cone 52A (if any) is much more than the (very small) erosion on the controller 46,80. small. A plan view corresponding to the structure of FIG. 5D is shown in FIG. 6B.

In the process sequence of FIG. 5, the main controller 80 is located on a portion of the patterned gate layer 46. In addition, the gate layer 46 may be located on a portion of the main control part. 7 illustrates a case in which the gate layer 46 partially extends over a group of electrically conductive main controllers 84 extending perpendicular to the plane of the figure. Reference numeral 52D indicated by the dotted line in FIG. 7 indicates the remainder of the excess emitter material layer 52B after the masked pattern etching. The shape of the excess layer 52D is almost the same as the shape of the excess layer 52C in the process sequence of FIG. 5C.

Impedance characteristics of the impedance component 42B include providing protection against short circuits to the display device, and methods for improving flat panel display performance during normal operation of the field emitters of the present invention, and unshorted. It is selected as a way to improve the ability to remove excess emitter material layer 52C without removing a significant amount of cone 52A material. During a typical display operation, component 42B avoids excessive power consumption and has a large impact on the luminance level achieved using other cones 52A at control apertures 82 of the same size as the shorted cones 52A. Limiting the short circuit current to a value low enough to avoid exposing it provides protection to the electrically shorted cone 52A.

In particular, when looking at the impedance characteristics of component 42B, it is assumed that V _GE represents the voltage between gate layer 46 and emitter electrode layer 42A. Suppose V _Z represents the voltage across the thickness of the lower impedance component 42B below any one of the electron emission cones 52A. The impedance voltage V _Z is one component of the gate-to-emitter voltage VGE. Almost all of the V _GE drop for a particular unshorted cone 52A occurs in the gap between the gate layer 46 and the cone 52A. Thus, the impedance voltage V _Z for the unshorted cone 52A is much less than the gate-to-emitter voltage V _GE .

Pixels in a flat panel display usually have multiple levels of grayscale luminance corresponding to different values of gate-to-emitter voltage (V _GE ). Assume that V _ZL represents an operating V _Z value that occurs at the minimum pixel luminance level during a normal display operation. At a typical maximum VGE level of 35 volts, the low operating value V _ZL is typically less than 1 volt. Assume that V _ZU represents a high V _Z value that occurs during a normal display operation. Although shorted cones 52A are automatically recovered using the present invention, some shorted cones 52A generally exist during normal display device operation. In the shorted cone 52A, substantially the entire value of the gate-to-emitter voltage V _GE appears across the impedance element 42B. The high operating value V _ZU is typically the maximum value of the voltage V _GE . Thus, V _ZU is typically 35 volts.

Current (I_ZIs the current of a single cone 52A, the impedance Z_BIs the current I flowing through the thickness of component 42B._ZIs the vertical impedance represented by component 42B. The characteristic of component 42B is its impedance voltage (V)._Z) (Absolute value) is the electrochemical removal value (V_ZR), The vertical impedance (Z_B) Becomes high and the voltage (V_ZLow operating value (V)_ZL) At high operating value (V_ZUV within normal operating range up to_ZR It is chosen to be relatively low compared to the value. In particular, the voltage (V_Z) -Z Is the impedance (Z_B) Is high. Normally -V_ZU To -V_ZL V of degree_Z Note that the value does not take field emitters. Thus, -V_ZU To -V_ZL V of degree_Z The characteristic of component 42B in the value is not of interest here.

The Z _B dependence on the impedance voltage V _Z can be represented mathematically using the transition V _Z value between the electrochemical rejection value V _ZR and the low operating value V _ZL . Assuming that V _ZT represents this transition value, the magnitude of the vertical impedance Z _B is (a) greater than the transition value Z _BT if the impedance voltage V _Z is between -V _ZT and 0, ( b) less than the transition value Z _BT when the voltage V _Z is between V _ZT and V _ZU . The magnitude of the impedance Z _B is also generally not necessarily but greater than Z _BT when the voltage V _Z is between 0 and V _ZT . Note that the Z _B characteristic is not specified in the region where the impedance voltage V _Z is smaller than -V _ZT . This is consistent with the fact that the change in impedance Z _B at a value of V _{Z on the} order of -V _ZU to -V _ZT is not of interest here. In the positive V _Z range of V _ZL to V _ZU , the magnitude of impedance Z _B is generally nearly constant. Because impedance Z _B varies with voltage V _Z , the current-voltage “IV” characteristic of impedance component 42B is nonlinear, usually very nonlinear.

By placing the impedance component 42B to have the non-linear IV characteristics described above, the magnitude of the impedance Z _B can be easily reached to a value at which the current I _Z can easily reach the required value to achieve a predetermined pixel luminance level. Low enough during device operation. On the other hand, if the magnitude of the impedance voltage V _Z is a significantly lower value V _ZR that occurs during electrochemical removal of the excess layer 52C, then the magnitude of the impedance Z _B is different from that of the unshorted cones 52A. And is sufficiently increased to effectively electrically insulate from any shorted cone 52A. Thus, any electrical short of cone 52A to excess layer 52C does not interfere with the electrochemical removal operation or damage the unshorted cone 52A.

8A-8D illustrate four different ways of implementing impedance component 42B to obtain the I-V characteristic.

In FIG. 8A, component 42B consists of a layer 90 of electrically resistive material. Assuming that R _B is the vertical resistance of the resistor layer 90, the vertical resistance R _B is (a) greater than the transition resistance value R _BT when the voltage V _Z is between −V _ZT and 0, (b) If the voltage V _Z is between V _ZT and V _ZU , it is less than R _BT . The IV characteristic of the resistive layer 90 is usually symmetrical with respect to the zero-I _Z point. Thus, resistor R _B is greater than R _BT when voltage V _Z is between 0 and V _ZT .

The resistive layer 90 is formed of a cermet (ie metallic particulate embedded in ceramic) or a silicon-carbon compound such as silicon-carbon-nitrogen. Other candidates for layer 90 are lightly doped polycrystalline semiconductor materials (such as polycrystalline silicon), intrinsic amorphous semiconductor materials (such as intrinsic amorphous silicon), large-bandgap semiconductor materials, aluminum nitride, and gallium nitride.

In FIG. 8B, an impedance component 42B is formed as a two-layer resistor. The two layer resistor consists of a lower electrical resistive layer 92 and an upper electrical resistive layer 94. The resistors 92/94 have the same basic resistive IV characteristics as described above for the resistor layer 90. Lower resistive layer 92 provides a nearly linear IV characteristic for I _Z in the range of I _ZL to I _ZU to resistor 92/94 during typical display operation. The upper resistor 94, which typically consists of a cermet, usually provides the increased vertical resistance needed during the electrochemical removal operation. International patent application PCT / US98 / 12461 (filed Jun. 9, 1998) to Knall et al. Provides further information on registers 92/94, the contents of which are incorporated herein by reference.

In FIG. 8C, impedance component 42B consists of a diode formed of an upper anode layer 96 and a lower cathode layer 98. Current flows down through diodes 96/98 during typical display operation. Diodes 96/98 are generally semiconductor diodes having a threshold voltage (V _T ) of less than 0.9 volts. If the impedance voltage V _Z is greater than V _T , current flows through the diode 96/98 and is limited by the internal resistances of the cathode 98 and anode 96. If the magnitude of the impedance voltage V _Z is less than zero (ie, the diode 96/98 is reverse biased), no current flows substantially through the diode 96/98. In fact, the internal resistance of diode 96/98 is very high when voltage V _Z is negative.

Impedance component 42A is formed to implement the capacitor of FIG. 8D. The capacitor is composed of a lower plate formed of the upper electrically conductive plate 100, the dielectric layer 102, and the emitter electrode 42A. Top plate 100 may be removed. Then, the electron-emitting device 52A forms a top plate. The I-V characteristics for the impedance component 42B are satisfied with the capacitor 100/102/104 due to the switching / unswitching nature of how the flat panel display is used during normal display operation and electrochemical removal operation.

FIG. 9 shows a general example of the core active area of a flat panel CRT display using a field electric emitter as in FIG. 5D (or FIG. 7), manufactured in accordance with the present invention. The substrate 40 forms a baseplate or backplate for a CRT display. Emitter region 42 is located along the inner surface of baseplate 40. One main controller 80 is shown in FIG.

The transparent, generally glass faceplate 110 is positioned away from the baseplate 40. One of the ones shown in FIG. 9, a phosphor emitting region 112, is located on the inner surface of the faceplate 110 spaced from the corresponding large control aperture 82. A thin light reflecting layer 114, typically aluminum, is placed over the fluorescent region 112 along the inner surface of the faceplate 110. Electrons emitted by the electron-emitting device 52A pass through the light reflection layer 114 and allow the fluorescent region 112 to emit light for producing a visible image on the outer surface of the face plate 110.

The core active area of the flat panel CRT display generally includes other components not shown in FIG. For example, black matrices located along the inner surface of faceplate 110 generally surround each fluorescent region 112 to separate each other laterally from other phosphorescent regions 112. A focusing ridge provided on the inter-electrode dielectric layer 44 helps control the electron trajectory. Spacer walls are used to maintain a relatively constant gap between the baseplate 40 and the faceplate 110.

When assembled into a flat panel CRT display of the type shown in Fig. 9, the field emitter manufactured according to the present invention operates in the following manner. The light reflection layer 114 functions as an anode for the field emission cathode. The anode is held at high positive potential for the gate and emitter lines.

When a suitable potential is applied between (a) a selected one of the emitter column electrodes 42A and (b) a selected one of the column electrodes partially or wholly composed of the gate layer 46, the gate portion thus selected is selected from two selected electrodes. Electrons are extracted from the electron-emitting device at the intersection of and the magnitude of the obtained electron current is controlled. When the fluorescent region 112 is a high potential phosphor, the applied gate-to-cathode horizontal-plate electric field is 20 volts / mm or less at a current density of 0.1 mA / cm 2 as measured on the sulfur-coated faceplate in the display device. In general, the required level of electron emission is generated. When hit by the extracted electrons, the fluorescent region 112 emits light.

Directional terms such as "lower" and "upper" are used when describing the present invention to establish criteria that will allow the reader to more easily understand how the various components of the present invention are constructed. It became. In actual implementation, the components of the electron-emitting device may be located in a different orientation than indicated by the directional terminology used herein. This fact applies equally to the method by which the manufacturing step is carried out in the present invention. Since directional terminology has been used to facilitate the description, the present invention encompasses settings that differ in orientation from those strictly applied by the directional terminology used herein.

Although the present invention has been described with reference to specific embodiments, this description is for illustrative purposes only and does not limit the scope of the invention as set forth in the claims below. For example, a suitable metal other than the one specified above may be subjected to an electrochemical removal test on a candidate metal using another electrolyte solution, as in FIGS. 4A and 4B, to determine the appropriate range of drive potentials (V _WE ). By performing and checking the result, it can be selected for the emitter material of electron emission cone 52A and the gate / column material of gate layer 46 and for each main control portion 80 or 84 (if present).

Electrical comprising a working electrode conductor, a counter electrode, a counter electrode conductor similar to conductor 76, and an optional counter electrode conductor similar to conductor 79, but without a reference electrode (or reference electrode conductor). A chemical removal system may be used instead of the electrochemical removal system of FIG. 3A or 3B. This change simplifies the operating process and is particularly suitable for production scale production of electron emitters (production on an industrial scale). Alternatively or additionally, it may be possible to remove the counter electrode 70 (and associated conductor 76) in certain situations for simplicity.

Instead of being located in the electrolytic solution 64 over the excess layer 52C, as part of the substrate 40, a counter electrode may be provided inside the electron emitter itself. The optional counter electrode conductor 79 may be connected to each terminal on the control system 62 rather than being commonly connected via terminal WE of FIG. 3A or terminal CE of FIG. 3B.

Galvanostatic (constant-current) electrochemical removal systems may be used in place of the electropotential devices described above. The electrolytic device control system 62 of FIG. 3A or 3B is a galvanic electrolysis control system including a current source for flowing a substantially constant current through the working electrode conductor 73 and the count electrode conductor 76. Replaced. The potential between the counter electrode 70 and the working electrode conductor 73 in the galvanic electrolysis system will rise to a value sufficient to electrochemically remove each main control portion of the gate layer 46 and / or (if present). As such, the electrochemical removal operation is generally terminated after a pre-selected removal time. In addition, a potentiometer may be included in the system to terminate when the removal process reaches a preselected potential between the potentials of conductors 73 and 76.

The electrochemical removal system of FIG. 3A or 3B may be modified such that a controllable potential exists between the working electrode conductor 73 and the counter electrode conductor 76 rather than maintaining the conductor 73 at a fixed potential. have. The potential between the conductors 73 and 76 can be set to a fixed value or programmatically controlled during operation.

Impedance component 42B may be formed of three or more electrical resistive layers. Combinations of resistors, capacitors, diodes, and other basic electrical components may be used to form the impedance component 42B.

2 and 5 may be modified to make the non-conical electron-emitting device. For example, deposition of the emitter material may end before the emitter material completely closes the opening entering the dielectric opening 52. Then, the electron-emitting device 52A is generally formed into a truncated cone. The electrochemical removal operation of the present invention is sequentially performed on the excess emitter material layer 52C with the cut cone 52A initially exposed to the electrolytic solution 64 through the aperture in the layer 52C.

The organic solvent in the electrolytic solution 62 may be formed of two or more organic solutions. The acid may also be formed of two or more acids, typically two or more organic acids. Two or more salts, generally organic salts, can similarly be used in solution 64.

Any one or more of lithium nitride (LiNO ₃ ), potassium nitride (KNO ₃ ), rubidium nitride (RbNO ₃ ), and cesium nitride (CsNO ₃ ) are selected from sodium nitride as a source of oxidant ions in the aqueous solution of electrolytic solution 64. It may be substituted or used in combination with it. Similarly, any one or more of lithium hydroxide (LiOH), potassium hydroxide (KOH), rubidium hydroxide (RbOH), and cesium hydroxide (CsOH) are used as a base in solution 64 or substituted with or in combination with sodium hydroxide. Can be. Any one or more oxidants may be used with any one or more bases. In either of these substitutions or bonds, the total molarity of the oxidant and base is the same as described above for sodium nitride and sodium hydroxide, respectively.

Nitrides of one or more Group II metals, in particular magnesium, calcium, strontium, and barium, may be used in place of or in addition to the Group I metal nitrides described above to implement an aqueous solution of the electrolytic solution 64. Similarly, one or more hydroxides of the Group II metal may be used in solution 64 instead of or in addition to the Group I metal hydroxides described above.

When performing a masked etch on the blanket excess emitter material layer 52B (prior to the electrochemical removal operation), (a) substantially all of the main controller portions 80 are over emitters on the controller 80. Masked etching can be performed in such a way that it is covered with excess emitter material rather than leaving only islands 52C of material, and (b) the excess emitter material is removed from the area between the controller 80. The electrochemical removal process of the present invention is long enough to create an opening through the patterned excess emitter material layer 52C to expose the electron emission cone 52A, but not long enough to remove all of the layers 52C. It may also be performed. By combining the two above modifications, the residual excess emitter material located on the controller 80 can function as part of the controller 80 to increase the current conducting capability.

 It may be desirable to have a tip formed of an emitter material, such as a refractory metal carbide, which electron emitting source cannot be directly and directly electrochemically removed. Titanium carbide is an attractive refractory carbide for the tip of an electron emission cone. In this case, an electrically non-insulating emitter material (such as molybdenum), which can be electrochemically removed, is deposited on top of the structure in the steps shown in FIG. 2A or 5A and for the electron emitting device in the dielectric opening 50. Form a truncated cone. The cone forming process is then completed by depositing non-electrochemically removable material on top of the structure and in opening 50 until the aperture through which the material enters opening 50 is completely sealed.

The electrochemical removal operation is then performed in the manner described above to remove excess electrochemically removable emitter material located directly on the gate layer 46 and, if present, on the separate main control. During this operation, excess non-electrochemically removable emitter material located along the top of the structure is lifted off. Thus, a conical electron-emitting device having a tip of nonelectrochemically removable emitter material and a base of electrochemically removable emitter material is exposed through gate opening 48.

Given that the layer 32 consists of electrochemically removable material in the prior art process of FIG. 1, the principles of the present invention provide an intermediate layer, such as layer 32, located between the gate layer and the layer comprising excess emitter material. It can be extended to remove it electrochemically. On this extension line, the excess material layer is generally lifted off as a result of removing the intermediate layer. Any of the electrochemical removal systems described above can be used in this extended process sequence.

If the emitter region 42 has a thickness sufficient to support the structure, the substrate 40 can be removed. The insulating substrate 40 may be replaced with a composite substrate on which a thin insulating layer is placed over a relatively thick non-insulating layer that provides structural support.

The electrochemical removal method of the present invention can be used when making an ungateed electron emitter. Electron emitters produced according to the present invention can be used to make flat panel devices other than flat panel CRT displays. Accordingly, various changes and applications may be made by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (60)

(a) the first non-insulating area comprises a first material, (b) the impedance means is electrically connected to the plurality of non-insulating members, and (c) each non-insulating member comprises the first material. Providing an initial structure; And 20. A method comprising electrochemically removing at least a portion of a first material of a non-isolated region by a process comprising applying a selected potential to the non-insulated region. The first material of each non-insulating member that is not electrically connected to the non-insulating region outside of the impedance means and outside of the interposed electrolytic solution because the impedance means provides a high impedance during the removing step is the removal of the first material. Characterized in that it does not erode significantly electrochemically during the step. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete (a) an electrical non-insulating control electrode is placed on an electrical insulating layer located in impedance units, (b) a plurality of composite openings extend through the control electrode and the insulating layer, and (c) a first electrical non-insulating emitter (D) providing an initial structure wherein an excess layer of material is positioned over the control electrode, and (d) a plurality of electron-emitting devices are each located within the composite opening; And 10. A method comprising electrochemically removing at least a portion of a first material of said excess layer by a process comprising applying a selected potential to said excess layer. Each of the electron-emitting devices comprises a first emitter material and is electrically connected to the impedance means, The first material of each electron-emitting device that is not electrically connected to the excess layer outside of the impedance means and outside of the interposed electrolytic solution because the impedance means has a high impedance during the removal step, during the removal step Electrochemically not highly eroded. delete delete delete delete delete delete delete delete delete delete delete delete delete (a) providing an initial structure wherein the first electrically non-insulated region comprises a first material, and (b) the second electrically non-insulated region not electrically connected to the first region comprises a first material; And Electrochemically removing at least a portion of the first material of the first region by a process comprising contacting at least a first material of the first region with an electrolytic solution containing an organic solvent and an acid. To Wherein the first material of the second region is at a different potential than the first material of the first region so that the first material of the second region does not erode significantly electrochemically during the removal step. delete delete delete (a) the first non-insulating area comprises a first material, (b) the impedance means is electrically connected to the plurality of non-insulating members, and (c) each non-insulating member comprises the first material. Providing an initial structure; And Applying at least a portion of the first material of the non-insulated region to a non-insulated region by a process comprising applying a selected potential to the non-insulated region while at least the first material of the non-insulated region is in contact with an electrolyte solution containing an organic solvent and an acid In a method comprising the step of removing, Since the impedance means have a high impedance during the removing step, the first material of each non-insulating member that is not electrically connected to the non-insulating area outside of the impedance means and outside of the interposed electrolytic solution is electrically charged during the removing step. Characterized in that it is not highly eroded chemically. delete delete delete delete delete (a) an electrical non-insulated control electrode is located on an electrical insulation layer located in impedance units, (b) a plurality of composite openings extend through the control electrode and the insulation layer, and (c) a first electrical non-insulated emitter material. (D) providing an initial structure in which an excess layer comprising a; And Electrochemically removing at least a portion of the first material of the excess layer by a process comprising contacting at least the first material of the excess layer with an electrolyte solution containing an organic solvent and an acid. , Each electron-emitting device comprises a first material and is electrically connected with the impedance means, Each non-shorted electron because the first material of each electron-emitting device that is not electrically connected to the first material of the excess layer outside of the impedance means and outside of the electrolytic solution is at a different potential than the first material of the excess layer. Wherein the first material of the emissive element is not highly eroded electrochemically during the removal step. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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