EP0838832A1 - Method for fabricating a vacuum field emission device and apparatuses for performing this method - Google Patents

Abstract

The method involves positioning, sealing (8), returning the device to the atmosphere, putting under vacuum and drying after which the getter (50, 51) is hydrogenated and the device closed. The getter may be introduced after sealing and return to the atmosphere or simply after sealing. Following absorption of hydrogen, the device is returned to normal temperatures and may be operated for a period to degas the phosphors during a re-pumping stage before closure. The getter may advantageously be kept cool until hydrogenation, then activated by inductive heating. The getter is zirconium or titanium with either one from vanadium, manganese, iron, cobalt, nickel or chromium or two from vanadium, manganese, iron, cobalt and chromium.

Description

TECHNICAL AREA

The present invention relates to a generally a process for manufacturing a device using an electron source to microtips ("microtips") and more particularly a method of manufacturing an emission device field, i.e. a flat screen for viewing by cathodoluminescence excited by field emission, or cold emission, using microtips.

Such devices are better known under the name of "Field Emission Displays" (FEDs).

They apply in particular to manufacturing television screens.

More specifically, the invention relates to a manufacturing process which makes it possible to generate, control and maintain a hydrogen pressure inside the device, this pressure being able to be included in the range going from approximately 10 ^-5 Pa to approximately 1 Pa.

PRIOR STATE OF THE ART

Microtip screens are tubes flat cathodes which operate under vacuum.

These screens include a cathode (formed including cathode conductors, grids and microtips) and an anode (formed of conductors and luminophores).

The lifetime of the cathodes (linked to the fall in electron current as a function of time) very much depends on the quantity and nature of the gases residuals present in such a screen.

The very flat screen structure means that its volume and conductance are very low.

The degassing, which essentially comes from the anode by the effect of electronic bombardment, is very dependent on the nature of the phosphors ("phosphors") that the anode comprises.

Therefore, it is very difficult to control and characterize the quality of the vacuum to inside the screen.

Experience shows that with some phosphors and degassing procedures and of optimized assembly the cathodes have durations of life over 10,000 hours.

With other phosphors, the durations of lives are much shorter.

Much more degassing procedures complex, industrially unacceptable, would necessary to improve these lifetimes.

In the case of three-color screens, three different phosphors are needed to get red, green and blue emissions, which makes all the more difficult the control of degassing and therefore control of the reliability of the cathodes.

We have analyzed the influence of different gases on the emissivity of metallic molybdenum microtips which are most commonly used in "Field Emission Displays".

The clearest results show that oxidizing gases and in particular oxygen have a very negative effect on the broadcast.

This effect is largely reversible, which shows that it is due to a modification superficial, by adsorption or oxidation, of the work output and not a change in configuration microtips.

Surface analyzes of the latter by Auger microscopy also show a state more oxidized surface in the case of microtips with degraded electronic transmission.

Reducing gases, and in particular hydrogen, have a very clear tendency to improve emissivity, all the more so when the hydrogen pressure is higher, at least up to the range from about 10 ^-1 Pa to about 1 Pa.

Degraded cathodes, brought together of partial pressure of hydrogen, find quickly their initial emissivity and even a higher emissivity than the latter.

All of these results appear coherent.

Hydrogen helps to conserve or even improve the metallic state of the microtips.

In the case of an oxidizing environment, hydrogen is to some extent likely to neutralize such an environment and ensure the cathode stability.

The effect of hydrogen on the emissivity of cathodes has been known for a long time.

The use of this effect in FEDs is more recent.

The authors of the present invention studied the effects of hydrogen in field emission devices by subjecting such a device (flat screen), while it was in operation and in dynamic pumping, to a controlled flow of hydrogen. allowing to maintain in the device a hydrogen pressure of the order of 10 ^-5 Pa to 5x10 ^-2 Pa.

The results obtained confirm the effect beneficial of hydrogen and show that it is thanks to it, to stabilize the cathodes even in a degraded environment.

The hydrogen pressures which are necessary to stabilize the cathodes depend on the phosphors used and range from approximately 10 ^-5 Pa to approximately 1 Pa.

To be usable, a device with field emission is closed and maintained under vacuum thanks to an element known as a getter, as it turns out made for conventional cathode ray tubes.

A getter is a metallic element which, once activated under vacuum by heating, is likely to fix the gases desorbed by the device and maintain the level of vacuum necessary for proper operation of it.

In more well-known applications, the role of a getter is to maintain the vacuum i.e. replace a vacuum pump.

In the case of a field emission screen, the problem to be resolved is twofold: the getter must pump oxidizing gases, which is its usual role, but must also make it possible to maintain a partial pressure of hydrogen of the order from 10 ^-5 Pa to 1 Pa.

SAES GETTERS S.P.A., which is specialized in the manufacturing of getters, has developed and qualified materials capable of playing this double role.

On this occasion, she filed a request patent which describes materials usable for this effect as well as a method of implementing these materials in flat screens.

This patent application was filed in Italy on July 1, 1994 and has deposit number MI94A001380.

An international demand, to which we will refer, was then filed.

Its publication number WO 96/01492 and for the title "METHOD FOR CREATING AND KEEPING A CONTROLLED ATMOSPHERE IN A FIELD EMITTER DEVICE BY USING A GETTER MATERIAL ".

• à faire absorber à un getter une quantité suffisante et contrôlée d'hydrogène dans une enceinte spéciale,
• à introduire le getter ainsi hydrogéné dans l'écran plat avant la phase d'assemblage de cet écran, et
• à assembler l'écran en le chauffant pendant environ 20 minutes à environ 450°C.

This implementation process consists of:

• to make a getter absorb a sufficient and controlled quantity of hydrogen in a special enclosure,
• introducing the getter thus hydrogenated into the flat screen before the assembly phase of this screen, and
• to assemble the screen by heating it for approximately 20 minutes at approximately 450 ° C.

The screen is evacuated either during the assembly phase or subsequently via a conduit called a queusot ("tail") which is then hermetically closed.

The implementation of a hydrogenated getter according to this known method has a significant drawback.

Indeed, during the assembly phase, the getter, filled with hydrogen, is heated to around 450 ° C under vacuum or in a neutral atmosphere.

Under these conditions, a large part of the hydrogen is desorbed and the getter is no longer likely to maintain hydrogen pressure high after returning to room temperature.

In an example described in document WO 96/01492, the final pressure is 4x10 ^-6 mbar (approximately 4x10 ^-4 Pa), which is generally insufficient to stabilize the emission current of the cathodes.

STATEMENT OF THE INVENTION

The object of the present invention is to remedy the previous drawback, that is to say the loss of hydrogen during the assembly phase of the screen.

It relates to a manufacturing process of a field emission device, this process including an assembly step, vacuum or controlled atmosphere, different elements of the device, this device further comprising at least a getter capable of being hydrogenated, this step assembly itself comprising a step of positioning of the different elements by compared to others, a step of steaming the device and a sealing step thereof, this process being characterized in that it further comprises a hydrogenation step of at least one getter capable of being hydrogenated, after the steaming step.

The getters capable of being hydrogenated can optionally be combined with other more conventional types of getters such as, for example, the “ flashable ” barium getter referenced ST14 at SAES GETTERS SPA.

This ST14 getter can be interesting for improve pumping capacity.

According to a first mode of implementation particular of the process which is the subject of the invention, successively performs the positioning step, the sealing step, a step of venting of the device, a step of vacuuming it, the steaming step, the hydrogenation step of each getter, this having previously been introduced into the device, and a step of closing the device.

In this case, the getter can be activated before the hydrogenation step. This activation can be carried out either by the steaming stage itself or after this baking stage by any means heating the getter.

According to a particular embodiment of the invention, the device further comprises at least an access duct and the getter is introduced by this access duct in the device.

The getter is preferably introduced after sealing and resetting the device to atmosphere but it can also be introduced before sealing, which can be interesting when using several queusots (see for example getter 51 in queusot 29 of Figure 4 described below).

In the case of the first setting mode particular work of the process, this process can further include a step of putting into operation temporary after the baking stage or after the baking stage hydrogenation.

In this case too, the process can further include a pump-down of the front device the closing step of it.

According to a second mode of implementation particular of the process which is the subject of the invention, assembles the device in an enclosure under vacuum or under a controlled atmosphere, successively the step of positioning the different elements and of each getter, the baking step and the sealing step and hydrogen is introduced in the enclosure, in order to perform the stage of hydrogenation, after the steaming stage and during and / or before the sealing step.

• les alliages binaires comprenant un premier élément choisi parmi Zr et Ti et un deuxième élément choisi parmi V, Mn, Fe, Co, Ni et Cr,
• les alliages ternaires comprenant un premier élément choisi parmi Zr et Ti et des second et troisième éléments choisis parmi V, Mn, Fe, Co, et Cr.

According to a preferred embodiment of the process which is the subject of the invention, each getter to be hydrogenated is chosen from:

• binary alloys comprising a first element chosen from Zr and Ti and a second element chosen from V, Mn, Fe, Co, Ni and Cr,
• ternary alloys comprising a first element chosen from Zr and Ti and second and third elements chosen from V, Mn, Fe, Co, and Cr.

These getters are mentioned in the document WO 96/01492 and reference will be made to this document, and in particular on pages 7 and 8 thereof, to find examples of usable getters for the implementation of the present invention.

• une canalisation,
• des première, deuxième et troisième vannes,
• des moyens de pompage aptes à communiquer avec le dispositif par l'intermédiaire de la canalisation et de la première vanne,
• un réservoir apte à communiquer avec le dispositif par l'intermédiaire de la canalisation et de la deuxième vanne,
• une source d'hydrogène apte à communiquer avec le réservoir par l'intermédiaire de la troisième vanne,
• des moyens de mesure de la pression à l'intérieur du dispositif, et
• des moyens de mesure de la pression dans le réservoir.

The present invention also relates to a first apparatus for implementing the method which is the subject of the invention, characterized in that it comprises:

• a pipeline,
• first, second and third valves,
• pumping means capable of communicating with the device via the pipe and the first valve,
• a tank capable of communicating with the device via the pipe and the second valve,
• a source of hydrogen capable of communicating with the reservoir via the third valve,
• means for measuring the pressure inside the device, and
• means for measuring the pressure in the tank.

• une enceinte,
• des moyens d'étuvage et d'assemblage du dispositif lorsque celui-ci est placé dans l'enceinte,
• une canalisation,
• des première et deuxième vannes,
• des moyens de pompage communiquant avec l'enceinte par l'intermédiaire de la canalisation et de la première vanne,
• une source d'hydrogène communiquant avec l'enceinte par l'intermédiaire de la deuxième vanne,
• des moyens de mesure de la pression dans l'enceinte en l'absence d'hydrogène dans celle-ci, et
• des moyens de mesure de la pression dans l'enceinte lorsque de l'hydrogène a été introduit dans celle-ci.

The present invention also relates to a second apparatus for implementing the method which is the subject of the invention, characterized in that it comprises:

• a speaker,
• steaming and assembly means of the device when the latter is placed in the enclosure,
• a pipeline,
• first and second valves,
• pumping means communicating with the enclosure via the pipe and the first valve,
• a source of hydrogen communicating with the enclosure via the second valve,
• means for measuring the pressure in the enclosure in the absence of hydrogen therein, and
• means for measuring the pressure in the enclosure when hydrogen has been introduced into it.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 est une vue en perspective schématique d'un dispositif à émission de champ,
• la figure 2 est une vue en perspective schématique de l'arrière de ce dispositif,
• la figure 3 est une vue en coupe transversale schématique du dispositif de la figure 1,
• la figure 4 est une vue schématique d'un premier appareil pour la mise en oeuvre du procédé objet de l'invention,
• la figure 5 est une vue schématique d'un deuxième appareil pour la mise en oeuvre du procédé objet de l'invention, et
• la figure 6 est une vue en coupe transversale schématique et partielle d'un dispositif à traiter dans l'appareil de la figure 5.

The present invention will be better understood on reading the description of exemplary embodiments given below, by way of purely indicative and in no way limiting, with reference to the appended drawings in which:

• FIG. 1 is a schematic perspective view of a field emission device,
• FIG. 2 is a schematic perspective view of the rear of this device,
• FIG. 3 is a schematic cross-section view of the device of FIG. 1,
• FIG. 4 is a schematic view of a first device for implementing the method which is the subject of the invention,
• FIG. 5 is a schematic view of a second device for implementing the method which is the subject of the invention, and
• FIG. 6 is a schematic and partial cross-section view of a device to be treated in the apparatus of FIG. 5.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

We will now describe a first mode of particular implementation of the process object of the invention but, before, some reminders will facts about the structure of emission devices field.

An example of an emission device field is schematically represented in perspective on Figure 1.

This device 2 of FIG. 1 comprises a front part 4 made of glass and rear part 6 also made of glass.

These parts 4 and 6 are sealed on their periphery by means of a glass paste 8 at low point of fusion.

Figure 1 also shows by hatching area 10 on which the phosphors are arranged on the inner surface of the front part 4.

Figure 2 is a perspective view schematic of the inner surface 12 of the rear part 6 of the device of FIG. 1.

This figure 2 shows the zone 14 which is opposite zone 10, inside the device 2, and on which are placed the cathode and therefore the micro-tips.

These are formed by microelectronics techniques and can reach a density of the order of tens of thousands of micro-tips per square millimeter.

Figure 3 is a sectional view schematic cross section of device 2 which is shown in figure 1.

This figure 3 shows the microtips 16 preferably formed on a resistive layer such that a layer of silicon 18 deposited on cathode conductors, grid electrodes 20 separated from layer 18 by layer 22 of a dielectric material, phosphors 24 and space interior 26 of device 2.

This space must be maintained under vacuum or under a controlled atmosphere, for example hydrogen.

As seen in Figure 3, the device 2 can be provided with one or more conduits called queusots ("exhaust tubes") which are in general glass.

Queusot 28 that we see in Figure 3 is closed.

When open, it allows you to vacuum in the space 26 of the device 2 and to introduce the getters such as the getter 50 and possibly a suitable gas in this space 26.

We now describe a first process according to the invention.

According to this first method, a device field emission, for example of the kind that has been described with reference to Figures 1 to 3, is positioned and sealed under vacuum or atmosphere controlled (e.g. an argon atmosphere) by heating at a temperature between 400 ° C and 650 ° C, for about 1 hour.

This device is equipped with a queusot or of a plurality of queues.

At least one of these channels is open.

The sealing wall (reference 8 in FIG. 1) of the two parts of the device consists of a glass with a low melting point called "fried glass" .

After sealing and returning to the atmosphere, at least one specific getter not yet hydrogenated is introduced inside the queusot (or one of the queusots).

The getters are not, however, necessarily positioned in the queues but can also be entered on the screen.

This or these getters are for example of the kind of those marketed by SAES GETTER S.P.A. under the references St 909, St 707 and St 737.

The device is then mounted on a equipment that allows it to be pumped and steamed at about 400 ° C for several hours.

During this baking phase, the getter is activated, i.e. it is made able to pump oxidizing gases and adsorb a significant amount hydrogen.

After returning to room temperature, the device can be operated for a few hours to degas the phosphors under a dynamic pumping (debugging phase).

It should be noted that this phase of operation is not compulsory.

In addition, it can take place in the presence of hydrogen, for example under a pressure of the order of 10 ^-3 Pa to 10 ^-1 Pa.

But this is also not compulsory.

Then a quantity of hydrogen calibrated is introduced into the device.

Hydrogen could also be introduced before the previous operating phase.

The getter adsorbs this hydrogen in a time between a few minutes and an hour.

Depending on the quantity introduced, the equilibrium hydrogen pressure can range from 10 ^-5 Pa to approximately 1 Pa.

We can then create a vacuum in the device but it is not compulsory.

This device is then closed by closing of the open door, by local heating.

The advantage of this first process in accordance with the invention compared to the prior art described in WO 96/01492 resides in the fact that the getter is not heated after being loaded in hydrogen.

In this way, all the hydrogen introduced is preserved and a high equilibrium pressure, greater than about 10 ^-3 Pa, is maintained in the device, this pressure being able to go up to about 1 Pa.

An advantageous alternative embodiment is keep cold getters, not activated, for the baking and possibly debugging phase. So they are not unnecessarily prematurely partially saturated by the degassing flows which occur during these phases. In that case, activation is done just before hydrogenation by suitable heating means, for example using of an inductive heating which allows to heat locally the getter.

Figure 4 is a schematic view of a apparatus according to the invention, allowing the setting in work of the first process that we have just described.

This device provides a device with field emission completed of the type of device 2 of Figure 1.

• une canalisation 30 destinée à être raccordée en une extrémité 31 au dispositif 2 par le queusot 28,
• un système de pompage de type turbo-moléculaire 32 raccordé à l'autre extrémité 33 de la canalisation 30, par l'intermédiaire d'une vanne 34,
• un réservoir 36 dont le volume est égal à 0,714 litre dans l'exemple représenté et qui est raccordé, d'un côté, à cette autre extrémité 33 de la canalisation 30, par l'intermédiaire d'une vanne 38 et, de l'autre côté, à une bouteille d'hydrogène 40, par l'intermédiaire d'une vanne à aiguille 42 dont le débit est variable,
• une jauge à membrane 44 destinée à mesurer la pression dans le réservoir 36 et par exemple du type Baratron, permettant de mesurer des pressions dans la gamme allant d'environ 1 Pa à environ 10³ Pa, et
• une jauge de pression 46 raccordée à l'autre extrémité 33 de la canalisation 30 (comme les vannes 34 et 38), cette jauge 46 étant par exemple du genre de celles qui sont commercialisées par la société Bayer Alper et permettant de mesurer des pressions dans la gamme allant d'environ 10^-8 Pa à environ 10^-1 Pa.

This device of FIG. 4 comprises:

• a pipe 30 intended to be connected at one end 31 to the device 2 by the socket 28,
• a turbo-molecular type pumping system 32 connected to the other end 33 of the pipe 30, by means of a valve 34,
• a reservoir 36 whose volume is equal to 0.714 liters in the example shown and which is connected, on one side, to this other end 33 of the pipe 30, by means of a valve 38 and, from the on the other hand, to a hydrogen bottle 40, by means of a needle valve 42 whose flow rate is variable,
• a membrane gauge 44 intended to measure the pressure in the tank 36 and for example of the Baratron type, making it possible to measure pressures in the range going from approximately 1 Pa to approximately 10 ³ Pa, and
• a pressure gauge 46 connected to the other end 33 of the pipe 30 (like the valves 34 and 38), this gauge 46 being for example of the kind which are marketed by the company Bayer Alper and making it possible to measure pressures in the range from about 10 ^-8 Pa to about 10 ^-1 Pa.

It is specified that the device 2 is placed in a zone 48 for drying this device 2.

The valve 34 isolates the device 2 of the pump 32 and the valve 38 makes it possible to isolate this device 2 of the tank 36.

Hydrogen can be introduced into the tank 36 from bottle 40 and through through the needle valve 42 which allows fine-tune the hydrogen flow rate.

The gauge 46 allows to control the pressure at the outlet of device 2 and the membrane gauge 44 measures the hydrogen pressure in the tank 36.

To implement the first process according to the invention, we start by fixing (by means not shown) a getter 50 in the queuset 28.

This getter is for example of the kind of those which are marketed by SAES GETTERS S.P.A. under the reference St 737.

Alternatively, there is a plurality of getters in the queusot 28.

This Queusot 28 has of course been previously opened.

Alternatively, as seen in the figure 4, the device 2 does not include a single rod but two lines 28 and 29 and we place respectively in these lines two getters 50 and 51.

After closing any queusot additional 29, the end 31 of the line 30 to line 28 by welding.

The queusot 29 is preferably closed with his or her getters introduced before the stage of positioning.

The device 2 and the tank 36 are put under vacuum thanks to pump 32, valves 34 and 38 then being open and the valve 42 closed.

Then, in order to degas the device 2 and activate the getters, we perform a treatment thermal.

Device 2 is steamed for sixteen hours at 360 ° C.

This temperature is reached by following a temperature ramp of 1 ° C per minute.

After cooling to the room temperature, device 2 is switched on operation (electrical test) for 20 hours.

After stopping this phase of operation, the tank 36 is isolated from the device 2 by closing valve 38.

Device 2 is isolated from the pump vacuum 32 by closing valve 34.

The valve 42 is open.

Hydrogen is introduced into the tank 36 at a pressure of 470 Pa.

The valve 42 is closed.

The valve 38 is then open and the hydrogen is adsorbed by the getters.

About 30 minutes are required to achieve this adsorption.

The device 2 and the tank 36 are re-vacuumed for approximately 5 minutes per opening of valve 34.

The device 2 is then definitively closed and it is separated from line 30 by closing the shank 28.

A hydrogen pressure greater than 10 ^-2 Pa was measured inside the device.

We now explain a second process according to the invention.

With this second process in accordance with the invention, the sealing of the emission device field is of type "integral".

This means that the device is degassed and sealed under vacuum.

This second process is such that after sealing the field emission device remains under empty unlike the previous case where, after sealing, the device is brought back to pressure atmospheric then returned to vacuum and steamed.

The phases of this second compliant process to the invention are as follows.

The different elements of the device to field emission (plate carrying the anode, plate bearing cathode, sealing glass, getter (s) are positioned under vacuum and then steamed at a temperature of around 300 ° C to 450 ° C for one or more hours.

It is specified that at this stage the getters can be hydrogenated although this does not present of interest because in any case a later step hydrogenation is required.

The device can be fitted with one or plurality of closed queues which contain the getters.

The device may also not include of queusot.

In this case, the getters must be flat enough to fit inside of the field emission device on the sides of the active area of the latter, possibly in a groove in one of the glass plates of the device.

During the steaming phase, the plate carrying the anode can be pressed against the plate carrying the cathode or being separated from it.

In the latter case, better degassing can be obtained.

After the steaming phase, the enclosure in which the field emission device is placed is brought to a hydrogen pressure of between 10 Pa and 10 ⁵ Pa.

This enclosure can be isolated or not from pumping means thereof.

Alternatively, the getters are previously charged with a known quantity of hydrogen through appropriate means.

The plate carrying the anode and the plate carrying the cathode are then brought into contact with one on the other (if they were not) then the field emission device (for example of the kind of that of FIGS. 1 and 3) is sealed, under the previously established hydrogen pressure at a temperature between 400 ° C and 650 ° C for about 1 hour.

During the cooling phase, the or the getters adsorb the hydrogen trapped in the device and maintain an equilibrium pressure which mainly depends on the hydrogen pressure imposed during the sealing phase, the volume of the device as well as the amount and type of getter (s).

Compared to the prior art described in WO-96/01 492, the advantage of this second process according to the invention is that it allows maintain a large dose of hydrogen in the or the getters during the sealing phase by performing this under a high pressure of hydrogen.

We now describe, with reference in FIG. 5, an apparatus allowing the implementation of this second method according to the invention.

The device schematically represented on FIG. 5 comprises an enclosure 52 allowing steaming and assembly of the emission device field.

This enclosure 52 is equipped with means appropriate electrical and mechanical 53 allowing this steaming and this assembly of the device.

The apparatus of Figure 5 also includes a turbomolecular pumping group 54 which communicates with the interior of the enclosure 52 via a pipe 55 on which a valve is mounted 56.

In addition, this device includes a 58 hydrogen bottle which communicates with inside the enclosure 52 by means of a needle valve 60 with variable flow.

The valve 56 makes it possible to isolate the enclosure 52 of the pumping unit 54.

The valve 60 makes it possible to introduce, so hydrogen in enclosure 52.

The apparatus of FIG. 5 also includes a secondary gauge 62 of the type of those sold by the company Bayer Alper, which makes it possible to measure pressures ranging from 10 ^-9 Pa to 10 ¹ Pa.

This gauge 62 makes it possible to control the vacuum in enclosure 52.

The apparatus of FIG. 5 also includes a primary gauge 64 making it possible to measure pressures in the range from 10 Pa to 10 ⁵ Pa.

This gauge 64 makes it possible to measure the hydrogen pressure in enclosure 52, during sealing of the field emission device.

The different elements of the device are set up in enclosure 52.

The plate carrying the anode of the device is separated from the plate carrying the cathode by a distance 1 cm.

As seen in Figure 6, a closed shutter 66 is welded to the back of the plate 6 carrying the cathode of the device.

This queusot 66 contains two getters 68 per example of type St 737 mentioned above.

A hole 70 was previously drilled in the plate 6 at the level of the queusot 66 so as to establish communication between the device and this queusot 66.

The enclosure 52 is evacuated thanks to the pumping unit 54, the valve 56 being open and the valve 60 closed.

The different elements of the device to field emission are steamed for 16 hours at 360 ° C.

The plate carrying the anode and the plate carrying the cathode of the field emission device are then brought into contact with each other.

The valve 56 is closed and the enclosure 52 is filled with hydrogen by opening valve 60.

When the hydrogen pressure is stabilized at 10 ⁴ Pa, the valve 60 is closed.

The temperature of the enclosure is brought to 450 ° C for 1 hour to assemble the elements of the field emission device.

After cooling to temperature room, valve 56 is open and hydrogen contained in enclosure 52 is pumped back.

The valve 56 is closed and the enclosure 52 is brought back to atmospheric pressure by introduction of nitrogen therein, by means suitable not shown.

The device is then removed from enclosure 52.

It is then ready to be put in operation.

The advantage of the second method according to the invention compared to the method described in document WO 96/01492 lies in the fact that the sealing is done under a high hydrogen pressure of up to 10 ⁵ Pa, which allows introduce and maintain in the getter (s) a sufficient quantity of hydrogen, this making it possible to maintain, in the device, an equilibrium pressure greater than about 10 ^-3 Pa.

In addition, this second process is more simple than the first since it only requires one pumping step while the first conforming process the invention generally requires two.

In an alternative embodiment of the apparatus of FIG. 5, which is represented by dashed lines in this figure 5, the secondary gauge 62 is mounted on the portion of the pipe 55, portion which is between valve 56 and the enclosure 52, and the hydrogen bottle 58 communicates with this portion of pipeline by through valve 60.

Claims (12)

Method of manufacturing a device for field emission (2), this method comprising a step assembly, under vacuum or under controlled atmosphere, of the different elements of the device, this device further comprising at least one getter (50, 51; 68) suitable for being hydrogenated, this assembly step itself comprising a step of positioning the different elements in relation to each other, a steaming step of the device and a step of sealing thereof, this process being characterized by what it further includes a hydrogenation step at least one getter capable of being hydrogenated, after the steaming stage. Method according to claim 1, characterized in that the step is carried out successively positioning, the sealing step, a step of venting of the device (2), a step of vacuuming thereof, the steaming step, the step hydrogenation of each getter, this one having been previously introduced into the device, and a device closing step. Method according to claim 2, characterized in that the getter is activated before the hydrogenation step. Method according to claim 2, characterized in that the device further comprises at least one access duct (28, 29; 66) and in that the getter is introduced through this access duct into the device. Method according to any one of claims 2 to 4, characterized in that the getter is introduced after sealing and returned to the atmosphere of the device. Method according to any one of claims 2 to 4, characterized in that the getter is introduced before sealing the device. Method according to claim 2, characterized in that it further comprises a step of temporary operation after the stage steaming or after the hydrogenation step. Method according to any one of Claims 2 and 7, characterized in that it comprises further a step of pumping the device (2) before the closing step of it. Method according to claim 1, characterized in that the assembly of the device in an enclosure (52) under vacuum or under controlled atmosphere, in what we do successively the step of positioning the different elements and of each getter, the baking step and the sealing step and in that we introduce hydrogen in the enclosure, in order to perform the step of hydrogenation, after the steaming stage and during and / or before the sealing step. Method according to any one of Claims 1 to 9, characterized in that each getter to be hydrogenated (50, 51; 68) is chosen from: binary alloys comprising a first element chosen from Zr and Ti and a second element chosen from V, Mn, Fe, Co, Ni and Cr, ternary alloys comprising a first element chosen from Zr and Ti and second and third elements chosen from V, Mn, Fe, Co, and Cr. Apparatus for implementing the method according to any one of Claims 2 to 8, characterized in that it comprises: a pipe (30), first, second and third valves (34, 38, 42), pumping means (32) able to communicate with the device (2) via the pipe (30) and the first valve (34), a reservoir (36) capable of communicating with the device (2) via the pipe (30) and the second valve (38), a source of hydrogen (40) capable of communicating with the reservoir via the third valve (42), means (46) for measuring the pressure inside the device (2), and means (44) for measuring the pressure in the reservoir (36). Apparatus for implementing the method according to claim 9, characterized in that it comprises: an enclosure (52), means (53) for steaming and assembling the device when the latter is placed in the enclosure, a pipe (55), first and second valves (56, 60), pumping means (54) communicating with the enclosure (52) via the pipe (55) and the first valve (56), a source of hydrogen (58) communicating with the enclosure (52) via the second valve (60), means (62) for measuring the pressure in the enclosure in the absence of hydrogen therein, and means (64) for measuring the pressure in the enclosure when hydrogen has been introduced into it.

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