EP3371820B1 - Electron emission electrode and process for production thereof - Google Patents

Description

The invention relates to a method for producing an electron emission electrode of an electron source, wherein the electron emission electrode has at least one emission peak which is set up for emitting electrons into the environment. The invention also relates to such an electron emission electrode and to a device having one or more electron emission electrodes.

Such electron sources with at least one electron emission electrode can be used in different applications, for example in electron microscopes, field emission screens or other devices. There are already various proposals for the production of electron sources, eg in DE 11 2012 003 268 T5 . EP 1 892 741 A1 or DE 605 15 245 T2 , The known production methods are relatively complicated and, in particular in applications in field emission screens (FED technology), do not lead to the required durability of the electron emission electrode. From the US 2003/0155859 A1 the production of electron emission electrodes by means of high-precision NC production emerges in order to produce reproducible fine emission peaks.

The invention is therefore based on the object of specifying a contrast improved method for producing an electron emission electrode and an improved electron emission electrode.

1. a) Bereitstellen eines Grundkörpers aus einem sprödbrechenden Material,
2. b) mechanische und/oder thermische Oberflächenbearbeitung des Grundkörpers zum Formen der Emissionsspitze, wobei Material vom Grundkörper zumindest um die Emissionsspitze herum sprödbrechend abgetragen wird.

This object is achieved by a method according to claim 1. The method includes producing an electron emission electrode of an electron source, the electron emission electrode having at least one emission peak configured to emit electrons into the environment, comprising the steps of:

1. a) providing a basic body made of a refractile material,
2. b) mechanical and / or thermal surface processing of the body for shaping the emission peak, wherein material from the body At least around the emission peak around brittle-breaking is removed.

The invention thus makes use of the special properties of a brittle-breaking material in an advantageous manner. A refractile material, also referred to as a brittle fracture material, is inadequate in many applications because of this property. The inventors have recognized that such a material, together with a surface treatment in which the brittle refractive properties of the material are used selectively, leads to a considerable improvement in the production of an electron emission electrode and in the resulting functional properties of the electron emission electrode. Thus, with the invention considerably longer service life can be realized in the operation of the electron emission electrode, so that field emission screens with a practical operational stability (durability) can be realized for the first time with the invention. As a result, the FED technology can be widely used in practice for the first time with the invention, with the advantage that flat panel displays with significantly lower power consumption can be realized in comparison with current display technologies.

In addition, the invention allows the mass production of such electron emission electrodes in a particularly economical manner. The manufacturing process can be scaled particularly efficiently to large quantities. For example, silicon wafers used in semiconductor technology, for example with a diameter of 300 mm, can be used for the production of electron emission electrodes according to the invention. When producing electron emitter arrays having a size of, for example, 5 × 5 mm ² , approximately 2800 such electron emitter arrays can be produced per wafer.

In addition, compared to previous approaches for the realization of electron emission electrodes in field emission screens, a significantly higher emission current per emission peak can be realized, with the effect that one pixel of a field emission screen can already be operated with a single emission peak. In previous FED cathode tips, 2000 to 3000 tips had to be used for a single pixel alone, to achieve the necessary amperages. Therefore, in this regard, the production and the economics of such electron sources, especially for use in FEDs, can be optimized.

Compared with thermal emitters, the invention has the further advantage that the electron source can be realized in a much more compact manner and, in particular, significantly flatter structures can thus be realized. Thus, the invention is particularly suitable for use in the manufacture of flat screens.

As refractory material, all materials with brittle fracture properties are suitable, i. such materials where edge chipping occurs during machining. Particularly suitable is e.g. Silicon, both in monocrystalline and in polycrystalline form. Silicon has the advantage that it has ideal brittle-breaking material properties and is also inexpensive in the appropriate form, e.g. in the form of silicon wafers, is available.

Another advantage of the silicon material is its high heat capacity and good heat conduction. This is also conducive to the durability of the emission peak, as this minimizes burnup at the emission peak.

Further suitable materials are ceramic materials, for example AITiC or LaB ₆ , or amorphous materials such as glass materials, in particular conductive glass materials such as ITO, or silicon carbide.

The surface treatment can be done by mechanical processing, in particular by machining such as grinding, milling, turning and / or drilling. A combination of such machining methods can be used advantageously. The thermal processing can be carried out in particular indirectly thermally, for example by laser machining.

According to an advantageous development of the invention, a rough surface of the refractive material is produced at least in the region of the emission peak by brittle fracture. The rough surface additionally favors the aforementioned advantageous properties of the emission peak produced according to the invention, namely the durability and the relatively high emission current.

According to an advantageous embodiment of the invention, the mechanical surface treatment comprises generating intersecting and non-intersecting grooves on the surface of the base body, e.g. by means of a cutting process. In this way, a matrix-like pattern can be generated on the surface of the base body, by which a plurality of emission peaks are generated on the base body in one step. The non-intersecting grooves may be formed in particular as parallel grooves. The intersecting grooves may in particular be formed as grooves arranged at right angles to each other.

According to an advantageous embodiment of the invention, non-intersecting grooves are produced by overlapping guidance of a cutting tool along cutting lines at which the grooves are to be produced. In this way, an "overlapping process" can be realized in which the distances between the individual grooves are smaller than the width of the cutting tool used, for example the thickness of a cut-off wheel. Accordingly, the working width of the cutting tool is greater than the distance of adjacent non-crossing grooves. By superimposing the cutting lines, the desired surface roughness can be generated as a result of the brittle fracture. No subsequent roughening of the surface is required. In addition, such a overlapping guide of the tool initially produces a sharp edge. By subsequently producing the grooves extending in a crosswise manner, which in turn can be produced by overlapping guidance of a cutting tool, the desired emission peaks can be produced in a sufficiently sharp shape in large numbers. An additional shaping step is not required.

The tool does not necessarily have to be guided over the base body in accordance with the above-explained, overlapping guide for producing the grooves. The process can also be carried out in the form of a "chipping process". Here, a superposition of the cutting lines is not sought. The desired properties of the emission peak are nevertheless generated as a result of the brittle-refracting material properties. The "chipping" causes outbreaks in the region of the emission peak to be produced due to the fracture behavior of the brittle-breaking material used. These eruptions lead to sharp-edged e.g. flocculent or scale-like forms of the emission peak.

In this case, by suitable choice of the tool, e.g. Tool parameters such as abrasive media, coatings, shape, stiffness, surface texturing, dressing and conditioning behavior, cutting radius, tool geometry, wear condition, and the cutting separation process, e.g. Cutting lines, depth of cut, feed, cutting speed, tool angle, cooling medium, the resulting shape of the emission peak can be influenced in the desired manner and brittle fracturing of the material by individual or combined factors is influenced in the desired manner. In this case, the "overlapping process" and the "chipping process" can be changed and / or combined during the manufacturing process.

In addition, the brittle-refracting material can be controlled by deliberately set voltage conditions and environmental conditions, e.g. Cooling, be brought to increased brittle fracture. For this purpose, mechanical, thermal, geometric (shape, cracks etc.) and chemical influences as well as environmental changes can be used.

According to an advantageous development of the invention, a multiplicity of emission peaks are produced on the base body by the mechanical and / or thermal surface treatment of the base body. Advantageously, the plurality of emission peaks in one operation of the mechanical and / or thermal surface processing of the body getting produced. As a result, the invention can be optimized in particular for the mass production of such emission peaks. A tool change is not necessarily required in the operation or the number of tool changes can be minimized at least.

According to an advantageous development of the invention, it is provided that in the mechanical and / or thermal surface treatment of the base body base areas forming the base body are left unprocessed or other than the emission peaks surrounding areas are processed and, the emission peaks are processed to a lower height than the height of the base areas. The base areas can advantageously be used as a mounting space and spacers for an acceleration grid, in order to realize in this way with one or more emission peaks a complete electron source.

According to an advantageous development of the invention, one, several or all emission peaks of the electron emission electrode are connected via an electrical contact with an electrical contacting terminal of the electron emission electrode. The contacting terminal is for external contacting, i. for making an electrical connection with an electrical energy source or a control device of the electron emission electrode. The electrical contacting may be e.g. from the emission peak through the remaining material of the body to the Kontaktierungsanschluss done. It is possible to realize a single contacting of each individual emission peak, so that these can be controlled separately. Several emission peaks can also be connected to one another via common electrical contacts, so that these can only be controlled together in groups.

According to an advantageous development of the invention, one or more electron emission electrodes, each having one or more emission peaks, are segmented on the processed base body and / or one or more electron emission electrodes are made of the processed base body isolated with one or more emission peaks. In this way, the desired structure of the electron emission electrode and thus of the electron source can be created in an efficient manner in terms of production technology. In this context, segmentation is understood as the further shaping of one or more emission peaks on the same base body. Separation means the separation of one or more emission electrodes, for example in the form of a group of several emission electrodes, from the base body. The mentioned steps of segmentation and / or singulation are carried out in particular after step b) of the method according to the invention. Before the segmentation and / or singling, further production steps can be carried out, for example for the encapsulation of the electron emission electrode and the mechanical and electrical contacting.

The object mentioned above is further achieved by an electron emission electrode of an electron source according to claim 10. This also makes it possible to realize the previously explained advantages of the invention. The electron emission electrode has at least one emission peak arranged to emit electrons into the environment, wherein at least the emission peak consists of a brittle refractive material having a rough surface.

According to an advantageous development of the invention, the electron emission electrode has a plurality of emission peaks, which are arranged in a matrix-like manner in a regular or irregular pattern. The emission tips may be electrically contacted in groups together or individually contacted electrically, so that they can be controlled separately.

According to an advantageous development of the invention, the electron emission electrode has a plurality of base regions which surround the emission tip or the emission tips and which are suitable as spacers for an acceleration grid and have a greater overall height than the height of the emission peak or the emission peaks. In this way, cheap mounting options for the accelerating grid of the electron source.

1. a) R_a = 0,3 - 1,5 µm, R_z = 1,5 - 7,5 µm,
2. b) R_a = 0,3 - 0,8 µm, R_z = 1,8 - 5 µm,

R_a steht dabei für die mittlere Rauheit, R_z für die gemittelte Rautiefe (auch Zehnpunkthöhe) gemäß ISO 25178.The electron emission electrode has a rough surface in the region of the emission peak, with a surface roughness of R _a = 0.3-2.5 μm, R _z = 1.2-12 μm. The surface roughness of this rough surface may in particular be in one of the following ranges a), b):

1. a) R _a = 0.3-1.5 μm, R _z = 1.5-7.5 μm,
2. b) R _a = 0.3 to 0.8 μm, R _z = 1.8 to 5 μm,

R _a stands for the mean roughness, R _z for the average roughness depth (also ten point height) according to ISO 25178.

As a result, the positive properties of the emission peak according to the invention are further improved, in particular the durability and the high current intensity.

The invention further relates to a device having one or more electron emission electrodes and / or electron sources of the type described above. a flat screen, in particular in the form of a field emission screen, or an electron microscope, an X-ray machine, an emission mass spectrometer, e.g. an ion mobility spectrometer, a radar, a magnetron or a microwave oven.

The invention will be explained in more detail by means of embodiments using drawings.

Figur 1

einen Grundkörper in perspektivischer Darstellung und

Figur 2

einen Ausschnittsbereich des Grundkörpers gemäß Figur 1 in perspektivischer Darstellung und

Figur 3

eine Emissionsspitze in perspektivischer Darstellung und

Figur 4

den Ausschnitt gemäß Figur 2 in einer Seitenansicht und

Figuren 5, 6

einen "overlapping process" und

Figuren 7, 8

einen "chipping process".

Show it

FIG. 1

a main body in perspective and

FIG. 2

a cutout area of the body according to FIG. 1 in perspective and

FIG. 3

an emission peak in perspective and

FIG. 4

the clipping according to FIG. 2 in a side view and

FIGS. 5, 6

an "overlapping process" and

FIGS. 7, 8

a "chipping process".

In the figures, like reference numerals are used for corresponding elements.

The FIG. 1 shows a main body of a brittle-refractory material, such as a silicon wafer. The base body 1 is processed according to the invention, which is explained in more detail below with reference to a cutout region of the base body 1, which forms an electron emission electrode 2.

The FIG. 2 shows the cutout area in an enlarged view, wherein already a surface treatment of the base body has taken place, through which the cutout area is formed into an electron emission electrode 2 with a plurality of emission peaks. Is recognizable in the FIG. 2 an arrangement of a plurality of tip-like projections 3, which include the emission peaks of the electron emission electrode 2. In the edge regions there are several line-like elevations 4, which surround the matrix-like arrangement of tip-like elevations 3. In respective corner regions of the electron emission electrode 2 cuboidal elevations 5 are present, which can be used as base regions of the electron emission electrode. The aforementioned elevations 3, 4, 5 are located on a remaining floor area 8 of the base body 1. Die in FIG. 2 illustrated arrangement of elevations 3, 4, 5 can be generated in a simple manner by guiding a tool in two intersecting directions A and B over the surface of the base body 1. By guiding the tool in the direction A, a plurality of non-intersecting grooves 6 are generated. By guiding the tool in the direction B, several non-intersecting ones become Grooves 7 generated. The grooves 6 intersect the grooves 7, for example at a right angle. This then inevitably results in the illustrated structures of the elevations 3, 4, 5.

This can e.g. done by generating grooves in two steps. Thus, first a V-shaped cutting blade, which defines the acute angle of the emission peaks, can be used. By means of the V-shaped cutting blade, which is guided parallel in several steps in the direction B, and then in parallel in several steps in the direction A next to each other, the tips are first generated. Hereby also the height h of the tip-shaped elevations is determined. Subsequently, by another tool, e.g. U-shaped grooves generated determines the length of the tip-shaped elevations above the bottom portion 8. The tool is also guided in the directions A and B crosswise over the base body 1, which is also referred to as segmentation. This results in elevations 3, 4 with a certain height h above the floor area 8. Since certain surface areas of the base areas 5 are not processed, these can ultimately have a greater height h than the height of the elevations 3, 4th

The FIG. 3 shows one of the surveys 3 by way of example in an enlarged scale. It can be seen that in each case one emission tip 9 of the electron emission electrode is formed on a cuboid base section 10.

The FIG. 4 shows the arrangement according to FIG. 2 in a side view, wherein in addition to further processing steps electrical contacts and an acceleration grid are shown.

Visible is first that the height h of the elevations 3 and thus the emission peaks 9 is less than the height h of the base areas 5. Accordingly, a flat acceleration grid 14 can be arranged and fixed on the base areas 5, without causing any contact with the emission peaks. 9 comes.

The emission peaks 9 can be connected individually or in groups via electrical contacts guided through the material of the main body as well as lines 11 to a contacting terminal 12. About the Kontaktierungsanschluss 12 can be made via electrical leads 13, the electrical contact and signal feed into the emission peaks 9.

The production of the emission tip 9 and the base sections 10 can be done by an "overlapping process", which in the FIGS. 5 and 6 is shown. First, a tool is passed through the material 20 along a cutting line 21, then in a parallel manner along a cutting line 22. This results in an overlapping area 25 in which the emission peak 9 is generated after the same process in the two different cutting directions A, B was carried out. Subsequently, a segmentation, as in FIG. 6 represented by guiding a further tool along the cutting line 23, 24. As a result of the material 20, the base portion 10 is generated. Instead of segmenting, as in FIG. 2 shown, at a greater depth of cut also a separation of the emission peak 9 done with its base portion 10.

Based on FIGS. 7 and 8 a "chipping process" is described. In principle, the same tools can be used. In the first step, previously based on the FIG. 5 described, but the tool is guided along cutting lines 21, 22, in which it does not come to the overlap region 25. Accordingly, in the middle, a material portion which becomes the emission peak 9 remains. This leads to material outbreaks 26, which are also referred to as "chipping". These have an advantageous effect on the function and durability of the emission peak 9 due to the brittle-refracting properties of the material used. Subsequently, a segmentation, as in FIG. 8 represented by guiding a further tool along the cutting line 23, 24. As a result of the material 20, the base portion 10 is generated. Instead of segmenting, as in FIG. 2 shown, at a greater depth of cut also a separation of the emission peak 9 done with its base portion 10.

Claims (13)

1. Process for producing an electron emission electrode (2) of an electron source, wherein the electron emission electrode (2) has at least one emission tip (9), which is set up for releasing electrons into the environment, comprising the steps of:

   a) providing a main body (1) of a brittly fracturing material,

   b) mechanical and/or thermal surface working of the main body (1) to form the emission tip (9), wherein material is removed from the main body (1), at least around the emission tip (9), by brittle fracture and the emission tip (9) is created with a rough surface, the surface roughness of which lies in the range R_a = 0.3 - 2.5 µm, R_z = 1.2 - 12 µm, where R_a stands for the average roughness and R_z stands for the average peak-to-valley height according to ISO 25178.
2. Process according to the preceding claim, characterized in that a rough surface of the brittly fracturing material is created at least in the region of the emission tip (9) by brittle fracture.
3. Process according to one of the preceding claims, characterized in that the mechanical surface working comprises creating crossing and non-crossing grooves (6, 7) on the surface of the main body (1).
4. Process according to the preceding claim, characterized in that non-crossing grooves (6, 7) are produced by overlapping guidance of a machining tool along cut lines on which the grooves are to be created.
5. Process according to one of the preceding claims, characterized in that a multiplicity of emission tips (9) are produced on the main body (1) by the mechanical and/or thermal surface working of the main body (1).
6. Process according to the preceding claim, characterized in that the multiplicity of emission tips (9) are produced in one operation of the mechanical and/or thermal surface working of the main body (1).
7. Process according to one of the preceding claims, characterized in that in the mechanical and/or thermal surface working of the main body (1) surface regions of the main body (1) that form base regions (5) are left unworked or are worked differently than the regions surrounding the emission tips (9), and wherein the emission tips (9) are worked to a lower structural height (h) than the structural height (h) of the base regions (5).
8. Process according to one of the preceding claims, characterized in that one or more or all of the emission tips (9) of the electron emission electrode (2) are connected by way of electrical contacting (11) to an electrical contacting terminal (12) of the electron emission electrode (2).
9. Process according to one of the preceding claims, characterized in that one or more electron emission electrodes (2), with in each case one or more emission tips (9), are segmented on the worked main body (1) and/or one or more electron emission electrodes (2), with in each case one or more emission tips (9), are individually separated from the worked main body (1) .
10. Electron emission electrode (2) of an electron source, wherein the electron emission electrode (2) has at least one emission tip (9), which is set up for releasing electrons into the environment, characterized in that at least the emission tip (9) consists of a brittly fracturing material with a rough surface, the surface roughness of which lies in the range R_a = 0.3 - 2.5 µm, R_z = 1.2 - 12 µm, where R_a stands for the average roughness and R_z stands for the average peak-to-valley height according to ISO 25178.
11. Electron emission electrode according to the preceding claim, characterized in that the electron emission electrode (2) has a number of emission tips (9), which are arranged in a regular or irregular pattern in the manner of a matrix.
12. Electron emission electrode according to either of Claims 10 and 11, characterized in that the electron emission electrode (2) has a number of base regions (5), with a greater structural height (h) than the structural height (h) of the emission tip (9) or the emission tips (9), which surround the emission tip (9) or the emission tips (9) and are suitable as spacers for an acceleration grating (14).
13. Device with one or more electron emission electrodes (2) according to one of Claims 10 to 12.

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