FR3128307A1 - NON-EVAPORABLE GETTER ACTIVATED AT LOW TEMPERATURE, PUMPING DEVICE AND ENCLOSURE CONTAINING SUCH A GETTER - Google Patents

Abstract

Non-evaporable getter for obtaining and/or maintaining a high vacuum in an enclosure defined by a metal wall capable of releasing gas at its surface, characterized in that the getter comprises vanadium, zirconium and titanium, or elements having a degree of oxidation equivalent to these, in the following atomic proportions: between 20% and 60% vanadium, between 19% and 57% zirconium, and between 10% and 43% titanium. Pumping device and enclosure containing such a getter. ABRIDGE FIGURE: Fig.1

Description

Non-evaporable getter activatable at low temperature, pumping device and enclosure containing such a getter.

The present invention relates to enclosures under partial gas pressure, in particular enclosure vacuuming and more particularly getter pumping to obtain and/or maintain a high vacuum in an enclosure defined by at least one metal wall capable of releasing gas. gas on its surface.

BACKGROUND OF THE INVENTION

Certain microelectronic and/or nanoelectronic systems, such as those of the MEMS type ( Micro Electro Mechanical Systems ), NEMS ( Nano Electro Mechanical Systems ), MOEMS ( Micro Optical Electro Mechanical Systems ), NOEMS ( Nano Optical Electro Mechanical Systems ) or detector type infrared, require for their proper functioning to be enclosed or encapsulated in a hermetic manner in an enclosure whose atmosphere is controlled (control of the nature of the gases present in the enclosure and of the pressure prevailing in the enclosure).

The enclosure is generally defined by metal walls capable of releasing gas on their surface, in particular hydrogen when a very high vacuum (i.e. a pressure lower than 10 ^-7 hectopascal, see 10 ^{- 8} hectopascal) must be made inside said enclosure. Such degassing is also likely to be carried out by any element enclosed in the enclosure (microelectronic and/or nanoelectronic systems, infrared detector, etc.) but also by any material holding these elements (glue, solder, etc.).

Under these conditions, it is known, in order to obtain and/or maintain as high a vacuum as possible, to supplement the vacuum produced by mechanical pumps by carrying out additional pumping using a non-evaporable getter (NEG) placed in a thin layer on at least one of the walls of the enclosure. The getter is capable of producing chemically stable compounds by reaction with the gases present in the vacuum chamber (in particular oxygen, carbon monoxide, nitrogen, etc.) and this reaction gives rise to the disappearance of said gases, which which corresponds to a pumping effect in particular by adsorption of gas atoms by the getter.

For this reaction to occur, it is necessary that the surface of the getter is clean, i.e. free from any passivation layer formed during the exposure of the getter to ambient air. This passivation layer is classically eliminated by diffusing the surface gases inside the getter by heating under vacuum.

Thus, the getter must have an activation temperature as low as possible, compatible with the stoving temperatures of the enclosure walls.

It is known from document FR-A-2750248 that titanium and/or zirconium and/or hafnium and/or vanadium and scandium can constitute suitable non-evaporable getters. Indeed, these have a solubility limit greater than 2% for oxygen, which allows the adsorption of oxygen pumped to the surface during a large number of cycles of activation and exposure to oxygen. 'air.

It is specified in this document that titanium can be activated at 400 degrees, zirconium at 300 degrees and the titanium 50% - zirconium 50% alloy at 250 degrees. However, the electronic system(s) inserted into the vacuum enclosures generally melt at a temperature substantially close to 150 degrees. To avoid any degradation of these electronic systems during the activation of said getter, it is therefore necessary to strongly cool said electronic systems, which has the effect of complicating the production of vacuum devices.

OBJECT OF THE INVENTION

The object of the invention is to propose a solution which at least partially overcomes the aforementioned drawbacks.

To this end, a non-evaporable getter is proposed for obtaining and/or maintaining a high vacuum in an enclosure defined by at least one metal wall capable of releasing gas at its surface. According to the invention, the getter comprises vanadium, zirconium and titanium, or elements having a degree of oxidation equivalent to these, in the following atomic proportions:

• between 20% and 60% vanadium,
• between 19% and 57% zirconium, and
• between 10% and 43% titanium.

Such a getter has a minimum activation temperature substantially between 180 and 200 degrees, in other words relatively low compared to usual getters and close to the temperature at which the electronic systems of vacuum devices melt, which limits the amount of heat. to be evacuated to protect said electronic systems or surrounding equipment during getter activation.

According to one particular characteristic, the getter comprises 47% vanadium, 33% zirconium and 20% titanium. Such a getter has a minimum activation temperature substantially equal to 180 degrees.

According to another particular characteristic, the getter comprises 37.5% vanadium, 37.5% zirconium and 25% titanium. Such a getter has a minimum activation temperature substantially equal to 180 degrees.

The invention also relates to a pumping device for obtaining and/or maintaining a high vacuum in an enclosure defined by at least one metal wall capable of releasing gas on its surface, the device comprising such a getter arranged to be arranged at the interior of the enclosure.

The invention also relates to an enclosure defined by at least one metal wall capable of releasing gas on its surface, such a getter being placed inside the enclosure.

The invention will be better understood in the light of the following description, which is purely illustrative and not limiting, and must be read in conjunction with the appended figures, among which:

there schematically represents an electronic device according to the invention;

there schematically represents a first embodiment of the getter that can be used in the device illustrated in ;

there schematically represents a second embodiment of the getter that can be used in the device illustrated in .

Claims (5)

Non-evaporable getter (7) for obtaining and/or maintaining a high vacuum in an enclosure (3) defined by at least one metallic wall capable of releasing gas on its surface, characterized in that the getter comprises vanadium, zirconium and titanium, or elements having a degree of oxidation equivalent to these, in the following atomic proportions:

• between 20% and 60% vanadium,
• between 19% and 57% zirconium, and
• between 10% and 43% titanium.

Non-evaporable getter (7) according to claim 1, comprising 47% vanadium, 33% zirconium and 20% titanium. Non-evaporable getter (7) according to claim 1, comprising 37.5% vanadium, 37.5% zirconium and 25% titanium. Pumping device for obtaining and/or maintaining a high vacuum in an enclosure (3) defined by at least one metal wall capable of releasing gas on its surface, the device comprising a getter (7) according to any one of claims 1 at 3 arranged to be placed inside the enclosure. Enclosure (3) defined by at least one metal wall capable of releasing gas on its surface, containing a getter (7) according to any one of Claims 1 to 3.