RU2513563C2 - Sintered non-evaporating getter - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to getter materials and particularly to sintered non-evaporating getters, and can be used in vacuum engineering and microelectronics, particularly in discharge devices. The sintered non-evaporating getter comprises three layers, wherein the first and third layers are made of titanium-vanadium alloy powder in ratio of 70:30 wt %, the second layer is made of a mixture of said alloy powder and intercalated carbon in ratio of (80:20)-(99:1) wt %, thickness of the first and third layers is 20-200 times the average particle size of the alloy powder, thickness of the second layer is 1-6 times the thickness of the first or third layer, the active area of the layers is equivalent to at least 50 times the geometrical area of the getter, wherein the porosity of the sintered getter is 30-60%.

EFFECT: broader functional capabilities, improved sorption properties and mechanical strength.

6 ex, 1 tbl, 1 dwg

Description

The invention relates to various technological processes, namely to getters from non-evaporating getter materials.

The ability of non-evaporating getter materials to reversibly absorb (sorb) hydrogen and irreversibly absorb such gases as oxygen, water vapor, carbon oxides and, in some cases, nitrogen, their widespread use in vacuum technology and microelectronic industry, including discharge devices.

The main getters are getters (hereinafter getters), the non-evaporating getter materials of which are some active (transition) metals from the group Zr, Ti, Nb, Ta, V, or their alloys (double, triple) or compounds with one or more elements of groups Cr, Mn, Fe, Co, Ni, Al, Y, La and rare earth elements.

The getter can be made in the form of discrete components, for example, sintered granules or powders of a non-volatile getter material inside a suitable container, or as a thin layer of a non-volatile getter material having a thickness of tens or hundreds of microns (μm) located on the inner surface of the application device, or thin substrate, usually metal, in contact with the surface of the application device.

It is known to use a getter to obtain an ultra-deep vacuum in the chamber of a molecular pumping device. The getter is made in the form of a thin coating of non-evaporating getter material - titanium, and / or zirconium, and / or hafnium, and / or vanadium, and / or scandium, and / or their alloy on the determining surface of the metal wall of the device chamber by the method of cathodic deposition (ion spraying) [1].

Since the entire microelectronic industry is based on the use of thin-film technology, and from the point of view of integration of production, this technology is also preferred in the manufacture of coatings of non-evaporating getter material in these devices.

However, for various reasons, non-vaporizable getter coatings made up to now by ion sputtering cannot fully satisfy their requirements.

It is known to use getters made on the basis of non-evaporating getter materials - titanium, and / or zirconium, and / or hafnium, and / or vanadium, and / or scandium, and / or their alloy in an atomic beam tube on cesium or rubidium atom beams, containing in the vacuum casing a source of a beam of cesium or rubidium atoms, first and second atomic state selectors, a microwave resonator, a magnetic discharge pump, an indicator device, and getters located along the beam path.

In an indicator device, in order to provide a higher vacuum during operation or storage of devices and to increase the service life, at least one porous getter of active metals or mixtures thereof is additionally installed, the porous surface of the getter being covered with a graphite film of micron or submicron thickness [ 2].

Mentioned graphite film of micron or submicron thickness on the one hand provides the absorption of cesium atoms.

However, on the other hand, it significantly reduces the absorption of hydrogen, oxygen and nitrogen, since the graphite film prevents the absorption of these gases.

Known getter made in the form of a multilayer coating of non-evaporating getter materials, containing at least two layers made of non-evaporating getter material on a substrate, in which, in order to increase the sorbing properties, namely to increase the absorption rate at room temperature or temperature activation, incompatible with some applications, in particular miniature devices, the first layer deposited directly on the substrate consists of a non-vaporizing getter material, it surface area equivalent to at least 20 times the value of its geometric area, and located on the first layer, at least a second layer with a thickness of not more than 1 μm consists of a non-volatile getter alloy with a low activation temperature, while the deposited layers are obtained cathodic deposition [3].

The getter non-volatile material of the first layer is selected from the group consisting of zirconium, titanium, niobium, tantalum, vanadium, hafnium and Zr-Co-A alloy, where A denotes yttrium, lanthanum, rare-earth elements or mixtures thereof (wt.%) And is made with a thickness of 0 2-50 microns.

The getter non-volatile alloy material of the second layer contains Zr, V and one or more elements selected from Fe, Ni, Mn and A or Zr 80 - Co 15 - A 5, where A denotes yttrium, lanthanum, rare earth elements or mixtures thereof (wt. %) and made with a thickness of 0.05-0.5 microns.

A multilayer coating does not work as a simple sum of layers of two (or more) components, but as one single monocomponent layer, the properties of which are the combination of the best properties of existing layers.

However, this getter is characterized by low porosity and, accordingly, not a large active surface and, accordingly, low sorption properties due to the use of the method of cathodic deposition of non-evaporating getter material.

Known getter made of a powder alloy of non-volatile materials, in which to increase the mechanical and sorbing properties, the first component contains at least one element from the group Ti, Zr, the second component contains at least one element from the group V, Cr, Mn, Fe, Ni, the third component is calcium oxide (CaO), with a mass ratio between the first and second components of the getter from 10: 1 to 1: 5 and a CaO content of not more than 1 wt.%. In this case, the concentrations of these elements in the local zones of the getter are different [4] - prototype.

The presence of calcium oxide in the getter, on the one hand, increases the porosity of the getter and, accordingly, the sorbing (absorbing) properties, the value of which is expressed as sorption capacity. However, on the other hand, it leads to a decrease in mechanical strength.

Moreover, this getter does not provide absorption of cesium, which is especially important in the case of application in atomic beam tubes.

The technical result of the invention is the expansion of functionality, increasing sorption properties and mechanical strength.

The specified technical result is achieved by the claimed sintered non-vaporizing getter containing several layers each made of a given non-vaporizing getter material of a given thickness, while the active area of these layers is equivalent to the geometric area of the non-vaporizing getter.

In this case, the getter is made in the form of three layers, the first and third layers being made of titanium-vanadium alloy powder at their ratio, in wt.%, 70:30 with the thickness of each layer equal to 20-200 average size of the alloy powder, and the second layer made of a mixture of the powder of said alloy and intercalated carbon at a ratio in the mixture, in wt.% (80:20) - (99: 1), with a thickness equal to 1-6 of the thickness of the first or third layer, the getter having a porosity of 30 -60% and the active area of the layers equivalent to the geometric area of the getter is not less than 500 times the value.

Disclosure of the invention

The set of essential features of the declared getter, namely:

The implementation of the getter in the form of three layers, moreover, when the first and third layers are made of titanium-vanadium alloy powder at their ratio, in wt.%, 70:30 with a thickness of each layer equal to 20-200 average size of the alloy powder, the getter will be optimally the ratio between high sorption properties and high mechanical strength, thanks

firstly, the maximum possible open porosity of their surface,

secondly, high sinterability of titanium-vanadium metal powder.

And the execution of the second layer from a mixture of the powder of the mentioned alloy and intercalated carbon with their ratio in the mixture, in wt.%, (80:20) - (99: 1), with a thickness equal to 1-6 thickness of the first or third layer and its location between the first and third layers, will provide:

firstly, due to the high specific surface of intercalated carbon (more than 20 m / g), a significant increase in the active - effective area of the second layer and, as a result, an increase in the sorption properties of the getter as a whole, and especially high absorption of cesium atom vapors,

secondly, due to the high mechanical strength of the first and third layers - high mechanical strength of the getter as a whole,

thirdly, as indicated above, the high absorption of vapors of cesium atoms will provide enhanced functionality.

It should be noted that carbon is the most accessible getter material well sorbing - it absorbs pairs of cesium atoms from the three most famous (gold, antimony). It is known that one carbon atom binds up to three cesium atoms.

The implementation of the first and third layers of this thickness will provide a significant increase in the points of contact between the granules of the powder of the titanium-vanadium metal alloy and thereby sintering at these points is the maximum possible and, as a result, increase the mechanical strength of the getter (experimentally proven).

The implementation of the getter with a porosity of 30-60% will provide an extension of functionality due to a decrease in the activation temperature of the declared non-evaporative getter materials of titanium-vanadium (about 430 ° C), which is the optimum temperature for degassing of vacuum devices and thus does not require additional heating of the getter to activation.

The implementation of a getter with an active layer area of equivalent getter geometric area of at least 500 times the value will provide maximum sorption capacity for gases, including cesium, and, as a result, an increase in the sorption properties of the getter as a whole.

Experimentally established:

The implementation of the first and third layers:

a) from a powder of an alloy of titanium-vanadium at their ratio, in wt.%, 70:30, is optimal to ensure a low activation temperature,

b) a thickness of 20-200 of the average size of the granules of titanium-vanadium alloy powder provides the maximum sorption capacity for gases (hydrogen, oxygen, nitrogen, etc.) and optimal mechanical strength, taking into account the structural dimensions of the device.

Execution of the second layer:

a) from a mixture of the aforementioned alloy of titanium-vanadium and internally carbon at their ratio, wt.% (80:20) - (99: 1 is optimal to ensure high sorption capacity for cesium,

b) a thickness equal to 1-6 of the thickness of the first or third layer is optimal to ensure maximum sorption capacity for cesium and the mechanical strength of the getter.

The implementation of a sintered non-evaporating getter with a porosity of 30-60% is optimal to ensure high sorption capacity and mechanical strength of the getter.

So, the claimed sintered non-evaporating getter will fully provide a technical result, namely, the expansion of functionality, increase sorption properties and mechanical strength.

The invention is illustrated by drawings.

Figure 1 shows a General view of the claimed getter containing one direct sequence of layers of non-vaporizing getter, where

the first and third layer - 1 and 3, respectively, are made of a powder of an alloy of active metals titanium-vanadium,

the second layer - 2 is made of a mixture of the above-mentioned powder of an alloy of active metals of titanium-vanadium and intercalated carbon.

Declared sintered non-volatile getter works as follows.

As a result of activation of a non-evaporating getter material in a vacuum at an activation temperature of approximately 450 ° C for 30 minutes, the getter acquires the ability to absorb gases (hydrogen, oxygen, nitrogen and cesium atom pairs).

Examples of specific performance of the claimed sintered non-vaporizing getter.

Example 1

The getter dimensions are set for the application device, for example, an atomic ray tube:

The getter diameter is 40 mm, the thickness is 35 mm.

A direct sequence is made of three layers of non-evaporating getter material by powder metallurgy.

An alloy powder of the first and third layers is made of non-evaporating getter material.

Why take a powder of an alloy of titanium - vanadium (PTF TU 14-1-4699-2003), which corresponds to their ratio of 70:30, wt.%.

The arithmetic average size of the granules, which is 60 microns.

An alloy powder of the second layer is made of a non-vaporizing getter material.

Why take a mixture of the above titanium-vanadium powder and

intercalated carbon in the ratio in the mixture, in wt.%, 90:10, respectively.

Prepared powders fall asleep in direct sequence

into accessories made of stainless steel of grade 18X10T12H, pressed at a pressure of at least 100 kg / cm ² and sintered in a vacuum furnace grade E4-255 at a temperature of (970-990) ° C for 40 minutes. It is then cooled to room temperature and a getter sample is removed from the vacuum oven.

Examples 2-5. Analogously to example 1, getter samples were made, but with other structural parameters indicated in the claims (examples 2-3) and beyond (examples 4-5).

Example 6 corresponds to the data of the prototype.

On manufactured getter samples, tests were carried out for the subject: sorption capacity for hydrogen (H ₂ ) and mechanical strength.

The data are given in the table.

As can be seen from the table:

Sorption capacity:

hydrogen (H ₂ ) was approximately 1000 Pa × m ³ / kg,

for pairs of cesium atoms - about 2000 Pa × m ³ / kg,

Mechanical strength - (30-90) × 10 ⁵ N / m ² depending on the thickness of the second layer (a mixture of titanium-vanadium powder and intercalated carbon), which corresponds to operational mechanical strength.

Thus, the claimed getter will provide, in comparison with the prototype, an expansion of functionality, an increase in sorption properties (sorption capacity for hydrogen (H ₂ ) by 10 times, sorption capacity for pairs of cesium atoms by about 100 times and an increase in mechanical strength.

Information sources

1. RF patent No. 2193254, IPC H01J 41/12, 1/18, priority 06/18/97, published 12/27/2000

2. RF patent No. 2371822, IPC H01S 1/06, priority 05.06.08, published on 10.27.09.

3. RF patent No. 2277609, IPC С23С 14/14, H01J 7/18, priority 10.06.04, published 10.06.06.

4. RF patent No. 2118231, IPC B22F 3/11, C22C 1/08, priority 03/28/97, published 08/27/98 - prototype.

5. Powder metallurgy. Collection of reports of the 8th All-Union Conference on progressive methods for the production of powder parts // Higher School Publishing House, Minsk, 1966, p.165-169.

Claims (1)

A sintered non-vaporizing getter containing several layers each made of a given non-vaporizing getter material of a given thickness, the active area of the said layers being equivalent to the geometric area of the getter, characterized in that the getter is made in the form of three layers, the first and third layers being made of alloy powder titanium-vanadium at their ratio, in wt.%, 70:30 with a thickness of each layer equal to 20-200 of the average size of the alloy powder, and the second layer is made of a mixture of the powder of said alloy and intercalated carbon at their ratio in the mixture, in wt.%, (80:20) - (99: 1), with a thickness equal to 1-6 of the thickness of the first or third layer, while the getter has a porosity of 30-60% and an active area layers, equivalent to a getter geometric area of at least 500 times the value.

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