Method of manufacturing a pump element including deposition of a getter material produced by ion beam sputtering

Abstract

A method for manufacturing a pump element for a chamber (3) under gas partial pressure, the pump element comprising a substrate covered with a getter layer based on a metallic material, characterized in that it comprises the following steps: - placing the substrate and a target (C) in a metallic material in a vacuum treatment chamber, - pushing ions (I) against the target to extract particles of metallic material therefrom and project them against the surface of the substrate at an oblique angle of incidence. A chamber under gas partial pressure containing a getter produced in this way.

Description

Technical Field

[0001] The present invention relates to a chamber under gas partial pressure, and more specifically, to depositing a getter material on a substrate. Background Technology

[0002] Certain microelectronic and / or nanoelectronic systems, such as MEMS (microelectromechanical systems), NEMS (nanoelectromechanical systems), MOEMS (micro-opto-electromechanical systems), and NOEMS (nano-optoelectronic systems) types, or infrared detector types, require to be hermetically confined or encapsulated in a chamber for proper operation, with the chamber's air environment controlled (controlling the properties of the gases present in the chamber and the pressure within the chamber).

[0003] The chamber is typically defined by metal walls, which can release gases, particularly hydrogen, at their surfaces when an extremely deep vacuum (i.e., pressure less than 10⁻⁷ hPa, or even 10⁻⁸ hPa) must be generated inside the chamber. This degassing can also be performed by confining any components within the chamber (microelectronic and / or nanoelectronic systems, infrared detectors, etc.), but can also be performed by any materials used to hold these components (glue, solder, etc.).

[0004] In these conditions, it is known that, in order to obtain and / or maintain the deepest possible vacuum, a vacuum generated by a mechanical pump is achieved by supplemental pumping using a non-evaporable getter (NEG) in a thin layer disposed on at least one wall of the chamber. The getter is capable of reacting with gases present in the vacuum chamber (particularly oxygen, carbon monoxide, nitrogen, etc.) to produce chemically stable compounds, and this reaction causes the gas to disappear. This corresponds to a pumping effect, particularly a pumping effect through the adsorption of gas atoms by the getter.

[0005] Getter deposition in thin layers is typically performed under vacuum via cathodic sputtering. Cathodic sputtering involves using the energy of plasma (partially ionized gas) on the surface of a target (cathode) to individually acquire atoms of the material constituting the target and deposit them onto a substrate. For this purpose, a pure gas (typically argon) is ionized to generate plasma due to a potential difference or electromagnetic excitation. This plasma consists of argon ions, which are accelerated and confined around the target due to the presence of a magnetic field. Each ionized atom transfers its energy to the target by impacting it, acquiring an atom with sufficient energy to project onto the substrate, thus forming a getter layer.

[0006] However, such a deposition process has the disadvantage of forming impurities at the deposition layer because there are not enough electrons to ionize the plasma.

[0007] More importantly, the pressure present during such deposition is significant (approximately 10⁻³ hPa), which leads to contamination of the plasma by gases and the target environment. Summary of the Invention

[0008] The present invention aims to provide a solution that overcomes at least some of the aforementioned disadvantages.

[0009] To this end, a method for manufacturing a pump element for a chamber under gas partial pressure is proposed, the pump element comprising a substrate covered with a getter layer based on a metallic material. The method includes the following steps:

[0010] - Place the substrate and the target in the metallic material within a vacuum processing chamber; and

[0011] - Ions are pushed against the target to extract metallic material particles, and they are projected against the substrate surface at an angle of incidence.

[0012] Compared to cathode sputtering, this sputtering process generates very few particulate contaminants (without contaminating elements from the machine performing the process) and imparts greater atomic energy to the metal particles, which results in better strength of the getter on the substrate.

[0013] According to a specific characteristic, a getter includes several materials, and a target includes a band of materials constituting the getter.

[0014] According to a specific characteristic, a getter includes several materials, and a target includes an inlay of materials constituting the getter.

[0015] Specifically, these materials together form a substantially flat sputtering surface on which ions bombard. The materials are shaped and assembled together such that the sputtering surface is continuous and consists only of the materials.

[0016] Specifically, the material includes side portions having substantially complementary profiles in a plane orthogonal to the sputtering surface, the length of which is greater than the thickness of the material.

[0017] Specifically, the materials are assembled by bevel cutting.

[0018] Specifically, the materials are assembled in an interlocking manner.

[0019] Specifically, the getter includes several materials, and the target includes an alloy of different materials constituting the getter.

[0020] Depending on the specific characteristics, the angle of incidence is between approximately 5 and 30 degrees.

[0021] The present invention also relates to a chamber under gas partial pressure, the chamber containing a getter produced in this manner. Attached Figure Description

[0022] The invention will be best understood from the following description, which is purely illustrative and non-limiting, and must be read in conjunction with the accompanying drawings, including:

[0023] [ Figure 1 ] Figure 1 This schematically illustrates a prior art electronic device equipped with a getter;

[0024] [ Figure 2 ] Figure 2 Schematic illustration of the process for execution Figure 1 The method for depositing the getter material shown;

[0025] [ Figure 3A ] Figure 3A Showing the implementation Figure 2 A first embodiment of the target of the method shown;

[0026] [ Figure 3B ] Figure 3B Showing the implementation Figure 2 A second embodiment of the target of the method shown;

[0027] [ Figure 3C ] Figure 3C Showing the implementation Figure 2 A third embodiment of the target of the method shown;

[0028] [ Figure 4A ] Figure 4A yes Figure 3A The cross-sectional view of the target shown illustrates a first method of assembling the materials of the target;

[0029] [ Figure 4B ] Figure 4B yes Figure 3A The cross-sectional view of the target shown illustrates a second method for assembling the materials of the target. Detailed Implementation

[0030] refer to Figure 1The electronic device 1 includes an encapsulation structure 2 defining a chamber 3, which encapsulates a microelectronic or nanoelectronic system 4 (e.g., MEMS, NEMS, MOEMS, NOEMS type) or an infrared detector 5 (e.g., microbolometer type). In this case, the encapsulation structure 2 includes a base 2b and a cap 2a that are sealed to each other by a sealing seam 6 to form an hermetically sealed housing. A non-evaporative getter 7 (NEG) is deposited in a thin layer on the inner surface of the cap 2a. In this example, the cap 2a is flat to trap the gas surrounding it, thereby controlling the air environment in the chamber 3, both in terms of pressure and properties of the gas present in the chamber 3. The thickness of the getter layer 7 is substantially less than 10 micrometers, particularly between 1 and 5 micrometers. The general arrangement of the electronic device 1 known from the prior art is given only as an example and will not be described in more detail in this example, and a large number of other arrangements are possible. The inner surface of the cap 2a on which the getter 7 is deposited may in particular be a curved shape.

[0031] Getter 7 is a metal-based material with gas absorption and adsorption properties. In this example, it comprises vanadium (V), zirconium (Zr), and titanium (Ti) in the following atomic ratios:

[0032] Vanadium content ranges from -20% to 60%;

[0033] Zirconium content ranges from -19% to 57%; and

[0034] Titanium content ranges from -10% to 43%.

[0035] This ratio keeps the minimum activation temperature of the getter between 180 and 200 degrees Celsius, which is lower than that of titanium-based or zirconium-based getters, which are approximately 400 and 300 degrees Celsius, respectively.

[0036] Preferably, the getter 7 basically comprises:

[0037] -47% vanadium, 33% zirconium, and 20% titanium; or

[0038] -37.5% vanadium, 37.5% zirconium and 25% titanium.

[0039] This ratio makes the minimum activation temperature of the getter essentially equal to 180 degrees Celsius.

[0040] refer to Figure 2According to the present invention, the deposition of getter 7 on a substrate formed by a cap 2a is performed in a rarefied air environment within a reactor R by ion beam sputtering (IBS). (For simplicity, this is referred to as vacuum: the key point is that the reactor contains the minimum amount of atoms found in the getter, given the required purity of the getter layer.) Ions I from the ion source S are thus accelerated to a target C, which comprises materials constituting the getter 7, in other words, vanadium, zirconium, and titanium. The impact of ions I on the target C results in the sputtering of vanadium, zirconium, and titanium particles outside the target C. Therefore, by applying the principle of OAD (angled deposition), the sputtered particles emitted from the target C are collected on the surface of the cap 2a at an angled incident angle α to form a thin getter layer 7 with optimized roughness. Such a layer gives the getter 7 better strength and better pumpability on the cap 2a.

[0041] The ion source S can be, for example, a Kaufman-type DC (direct current) source.

[0042] In this example, the cap 2a is supported by a rotating support, which allows for uniformity of the deposition received by the cap 2a about the axis of rotation of the support.

[0043] The ions used are typically argon ions (Ar+) because they are readily generated, do not cause any chemical reaction with the materials constituting the target, and have a relatively high atomic mass, which is necessary for significant sputtering.

[0044] like Figure 3A and Figure 3B As shown, target C can be primarily rectangular ( Figure 3A ) or round ( Figure 3B In this example, target C is a multi-strip structure consisting of a vanadium strip M1, a zirconium strip M2, and a titanium strip M3. Therefore, considering the sputtering yield of the materials constituting strips M1, M2, and M3, ions I simultaneously bombard different strips M1, M2, and M3 in proportions corresponding to the desired stoichiometry. It should be understood that the width of each strip is proportional to the stoichiometric proportion of the material in getter 7 and inversely proportional to its sputtering yield: a higher desired material proportion results in a wider strip for a given sputtering yield, but a higher sputtering yield results in a narrower strip for the desired material proportion.

[0045] like Figures 4A to 4B As shown, each of the strips M1, M2, and M3 includes:

[0046] - Front section M1.1, M2.1, M3.1;

[0047] - The rear sections M1.2, M2.2, and M3.2, opposite to the front section M1.1; and

[0048] - Two side sections M1.3, M2.3, M3.3, each side section is connected to the longitudinal edge of the front section M1.1 and the longitudinal edge of the rear section M1.2.

[0049] The front portions M1.1, M2.1, and M3.1 together form a substantially flat sputtering surface on which ions I impact. Strips M1, M2, and M3 are formed and assembled together such that the sputtering surface is continuous, in other words, without gaps, and is composed solely of material, in which the strips M1, M2, and M3 are generated.

[0050] In this example, the strips M1, M2, and M3 are assembled by welding the longitudinal edge of the rear face M1.2 of the strips M1, M2, and M3. To limit any rise of solder (a source of undesirable metallic contaminants) on the sputtering surface, the side faces M1.3, M2.3, and M3.3 of the strips M1, M2, and M3 have substantially complementary profiles in a plane orthogonal to the sputtering surface, the length of which is greater than the thickness e of the strips M1, M2, and M3. For example, the assembly of the strips M1, M2, and M3 is a bevel assembly (…). Figure 4A ) or staggered assembly ( Figure 4B Advantageously, the side portions M1.3, M2.3, and M3.3 of strips M1, M2, and M3 are arranged to form a gap G between each of strips M1, M2, and M3, thereby preventing any rise of solder on the sputtering surface (in a manner known per se, the height of the risen solder is inversely proportional to the width of the gap G).

[0051] Target C can also be a vanadium, zirconium, and titanium inlay, or a vanadium, zirconium, and titanium alloy with controlled stoichiometry. Here, the ratio of vanadium, zirconium, and titanium in target C depends on the required ratio of vanadium, zirconium, and titanium in getter 7 and the sputtering yield of vanadium, zirconium, and titanium. (Reference) Figure 3C For example, target C is a predominantly rectangular inlay composed of multiple vanadium square pieces M1', zirconium square pieces M2', and titanium square pieces M3'.

[0052] Similar to strips M1, M2, and M3, square pieces M1', M2', and M3' each include:

[0053] - Front section;

[0054] - The rear portion opposite to the front portion; and

[0055] - Four side sections, each side section connecting to the edge of the front section and the edge of the rear section.

[0056] The front portions together form a substantially flat sputtering surface on which ions I impact. Square pieces M1', M2', and M3' are formed and assembled together such that the sputtering surface is continuous, in other words, without gaps, and is composed solely of material, in which the square pieces M1', M2', and M3' are generated.

[0057] Regarding strips M1, M2, and M3, in this example, the square pieces M1', M2', and M3' are assembled by welding the edges of the rear faces of the square pieces. To limit any rise of solder (a source of undesirable metallic contaminants) on the sputtering surface, the side portions of the square pieces have substantially complementary profiles in a plane orthogonal to the sputtering surface, the length of which is greater than the thickness of the square pieces. For example, the square pieces M1', M2', and M3' are assembled by bevel assembly or staggered assembly. Advantageously, the side portions of the square pieces M1', M2', and M3' are arranged to form gaps between each of the square pieces M1', M2', and M3', thereby preventing any rise of solder on the sputtering surface (in a manner known per se, the height of the risen solder is inversely proportional to the width of the gap).

[0058] The incident angle α is chosen to be as small as possible to create a porous getter layer, thereby increasing the active surface area of ​​the getter 7 deposited on the cap 2b and thus increasing the pumpability of the getter. Preferably, the incident angle α is between approximately 5 degrees and 30 degrees relative to the surface of the cap 2a.

[0059] For example, the heating element E can be introduced into the reactor R by infrared radiation to increase the intensity of deposition, adjust the minimum activation temperature of the getter 7, and also improve the pumpability of the getter 7, thereby increasing the service life of the microelectronic or nanoelectronic system 4 or the infrared detector 5.

[0060] The getter 7 is activated by heating before the cap 2a is fixed to the base 2b. Once the getter 7 is activated, the electronic device 1 is sealed by fixing the cap 2a to the base 2b, either by vacuum welding or by pressing a flattened cold tube.

[0061] Of course, the present invention is not limited to the described embodiments, but includes any variations that fall within the scope of the invention as defined by the claims.

[0062] Although in this example, getter 7 is deposited on the wall of cap 2a, it can also be deposited on one or more walls of base 2b, on the base, or on any other sub-component added to chamber 3 before chamber 3 is closed.

[0063] The shape of target C can be similar to Figure 3A and Figure 3B The shapes shown are different.

[0064] The atomic ratio of getter 7 may differ from those described.

[0065] The composition of getter 7 may differ from that described and may include, for example, scandium and / or hafnium and / or vanadium and / or zirconium and / or titanium. Specifically, it may include elements with an oxidation degree equal to that of these elements.

[0066] The deposition of getter 7 inside electronic device 1 by ion beam sputtering extends to any device including electronic, mechanical, chemical, and other components that require a sealed and dry environment: cold machines, infrared detection modules, cryogenic thermostats, inertial units, missile heads, or guided bombs, etc.

[0067] The chamber can contain any component whose operation and / or optimal performance require gas partial pressure, such as one or more electronic components, mechanical components of MEMS, etc.

[0068] The components of strips M1, M2, M3 or square pieces M1', M2', M3' can be cuboid or cubic components.

[0069] Although in this example the assembly of strips M1, M2, and M3 is performed by welding, it can also be performed by any other means (electron beam welding, laser welding, friction stir welding, arc welding, etc.) to obtain a continuous sputtered surface.

Claims

1. A method for manufacturing a pump element for a chamber (3) under gas partial pressure, said pump element comprising a substrate covered with a getter layer (7) based on a metallic material, characterized in that, The method includes the following steps: - Place the substrate and the target (C) in the metallic material in a vacuum processing chamber; and - Ions (I) are pushed against the target to extract metallic material particles, and they are projected against the substrate surface at an inclined incident angle (α). The getter (7) comprises several metal materials (M1, M2, M3), and the target (C) comprises a strip of material constituting the getter; or the getter (7) comprises several metal materials (M1', M2', M3'), and the target (C) comprises an inlay of material constituting the getter. The materials (M1, M2, M3, M1', M2', M3') collectively form a substantially flat sputtering surface. The ions (I) bombard the sputtering surface, shaping and assembling the materials together such that the sputtering surface is continuous and constitutes only the materials. The materials (M1, M2, M3, M1', M2', M3') include side portions having substantially complementary profiles in a plane orthogonal to the sputtering surface. The length of these profiles is greater than the thickness (e, e') of the materials. The getter layer comprises vanadium (V), zirconium (Zr), and titanium (Ti) in the following atomic ratios: - 47% vanadium, 33% zirconium, and 20% titanium; or - 37.5% vanadium, 37.5% zirconium and 25% titanium.

2. The method according to claim 1, characterized in that, The materials (M1, M2, M3, M1', M2', M3') are assembled by bevel cutting.

3. The method according to claim 1, characterized in that, The materials (M1, M2, M3, M1', M2', M3') are assembled in an alternating manner.

4. The method according to claim 1, characterized in that, The getter (7) comprises several metallic materials, and the target (C) comprises an alloy of different materials constituting the getter.

5. The method according to any one of claims 1 to 4, characterized in that, The incident angle (α) is between 5 degrees and 30 degrees.

6. A chamber (3) under gas partial pressure, the chamber comprising a getter (7) produced by the method according to any one of claims 1 to 5.

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