CN221759514U - Thin film getter structure for improving gettering efficiency - Google Patents

Abstract

The utility model discloses a film getter structure for improving the getter efficiency, which comprises a getter alloy layer with the initial activation temperature less than or equal to 300 ℃, a stainless steel, a kovar substrate layer and a getter alloy layer with the initial activation temperature greater than 300 ℃, wherein getter films with different materials are respectively deposited on two opposite surfaces of a sheet-shaped substrate with the thickness less than 1mm, such as the stainless steel, the kovar substrate and the like, by a PVD method, wherein one surface of the getter film is a getter film with lower initial activation temperature and higher activity, and the other surface of the getter film is a getter film with higher initial activation temperature and higher getter capacity; the thin film getter structure of the utility model can greatly shorten the activation time without influencing the getter capacity of the thin film getter at room temperature, and is particularly suitable for MEMS devices with chips fixed by an organic adhesive mode.

Description

A thin film getter structure for improving getter efficiency

Technical Field

The utility model relates to the technical field of electronic component materials, and more specifically to a thin film getter structure for improving air absorption efficiency.

Background Art

In recent years, as various MEMS devices are miniaturized, flattened, and integrated, the getters they need have gradually evolved from sintered non-evaporable getters to PVD-deposited thin-film getters. Generally, getter alloys such as zirconium-vanadium-iron and titanium-zirconium-vanadium are deposited on both sides of a long strip substrate with stainless steel, Kovar, and other metal materials as the substrate. After the MEMS device is baked to exhaust or exhaust sealed, the heat generated by the long strip substrate is transferred to the surface to activate the thin-film getter alloy on the surface.

These getter films are the same as ordinary non-evaporable getters. When heated and activated, nitrogen, carbon, and oxygen in the passivation layer on the surface of the getter alloy diffuse inward, exposing the active surface, which has a certain ability to absorb active gases. The activation temperature that can make the passivation layer diffuse inward and make the getter have a gettering rate of not less than 20% of full activation is called the initial activation temperature of the getter. Different getter alloys require different initial activation temperatures, and the absorption capacity of the fully activated alloys for different gases is very different. Generally speaking, getter materials with low initial activation temperatures are more active and react faster with gases; getter materials with high initial activation temperatures are generally less active and react slower with gases. For highly active gases such as hydrogen, they have a faster absorption rate and capacity even at room temperature. For carbon-containing gases such as carbon monoxide, nitrogen, and CmHn, their room temperature gettering capacity is extremely limited. In order to absorb a large amount of these less active gases, it is necessary to continue working at high temperatures so that these gases can be cracked on the surface of the getter alloy and diffuse into the alloy.

There are two ways to activate getters in MEMS devices. One is to complete the activation of the getter while the MEMS device is being baked and exhausted. The getter activation is generally completed in a high vacuum of less than 1E-3Pa, and then the MEMS device is sealed in a vacuum. This method of activating the getter can quickly obtain a clean active getter surface, but it requires special equipment and the efficiency of the equipment is very low. The other is to bake and exhaust, and after sealing and removing the MEMS device, the current is passed through the pin of the MEMS device through the substrate deposited with a thin film getter material, and the getter is activated by Joule heat. This activation method can use a general baking exhaust sealing equipment with high efficiency. However, since there is residual gas inside the device that is released again after sealing, the vacuum when activating the getter is generally only a few Pa to tens of Pa. In this way, the load of the getter is very large, and it is necessary to completely absorb this part of the residual gas and maintain it for a period of time before a fresh surface can be exposed on the surface. This part of the fresh surface is the key factor in maintaining the vacuum degree during the life of the MEMS device.

In addition, for MEMS devices currently packaged in ceramics, the chip is generally bonded to the ceramic shell with an organic fixing adhesive. These organic substances will release a large amount of CO, CO2, and CmHn in a vacuum, especially under heated conditions. These gases are the main gas sources during the life of MEMS devices, and are also the residual gases that need to be absorbed first when activating the getter. In order to quickly eliminate this part of the gas, some getter alloys with low initial activation temperatures, such as zirconium, cobalt, and cerium, can be used, while using a higher activation temperature. However, the gas absorption capacity of these alloys with low initial activation temperatures after high-temperature activation and cooling is very small. While the use of alloys with high initial activation temperatures, such as titanium, zirconium and other getter materials, although their gas absorption capacity after activation and cooling is large, their activity is limited, and it takes a long time to absorb carbon-containing gases.

Some existing thin film getter technologies only try to reduce the initial activation temperature or increase the getter capacity, without optimizing the speed and capacity for the absorption of carbon-containing gases. For example, Chinese invention patent 200410049383 discloses a non-evaporable getter multilayer deposit obtained by cathode deposition and its manufacturing method, in which a layer of titanium is deposited on a substrate as a main getter layer by magnetron sputtering, and then a very thin getter layer with a low initial activation temperature is deposited to prepare a composite getter film to reduce the overall initial activation temperature. For another example, Chinese invention patent 201811622378 discloses a sandwich-structured getter film, which first deposits a dense layer of titanium on a substrate as a barrier layer to prevent the impurity gas released by the substrate during activation from poisoning the getter layer, and it is also beneficial to adjust the microstructure of the getter film; then a zirconium-cobalt-rare-earth getter layer is deposited on the barrier layer; finally, a thin layer of precious metal palladium is deposited as a protective layer to prevent the open surface of the getter layer from being exposed to the atmosphere for a long time and causing oxidation.

Utility Model Content

To achieve the above-mentioned purpose, the utility model proposes a thin film getter structure for improving the air absorption efficiency, comprising an air absorption alloy layer with an initial activation temperature less than or equal to 300°C, a base layer such as stainless steel and Kovar, and an air absorption alloy layer with an initial activation temperature greater than 300°C, wherein the base layer such as stainless steel and Kovar is two layers, and is achieved by depositing air absorption films of different materials on two opposite surfaces of a sheet substrate such as stainless steel and Kovar with a thickness less than 1mm by a PVD method, and depositing 0.1-15μm air absorption films on two surfaces of a stainless steel and Kovar base with a thickness less than 1mm by a PVD method, wherein the air absorption film on one side is an air absorption film with an initial activation temperature less than or equal to 300°C and a larger activity, and the air absorption film on the other side is an air absorption film with an initial activation temperature greater than 300°C and a larger air absorption capacity.

Furthermore, the getter film has two sides, one of which is an getter film with an initial activation temperature less than or equal to 300°C, which can be a titanium zirconium vanadium or titanium zirconium cobalt rare earth getter film. The getter film with an initial activation temperature less than or equal to 300°C is one of titanium zirconium vanadium, titanium zirconium cobalt rare earth, and zirconium cobalt rare earth.

Furthermore, the other side is an air-intake film with an initial activation temperature greater than 300°C, which can be a titanium film or a zirconium film. The air-intake film with an initial activation temperature greater than 300°C and a large air-intake capacity can be one or more of titanium, zirconium, zirconium-vanadium-iron, zirconium-aluminum, titanium-tungsten, molybdenum-titanium, and zirconium-tungsten, or a multi-layer film combination of the prior art.

The thin film getter structure for improving the air absorption efficiency proposed by the utility model can bring the following beneficial effects:

1. The difference between the present invention and the existing multilayer film technology is that the getter alloys with different initial activation temperatures are distributed on both sides of the substrate. If the existing multilayer film technology is used to stack two getter alloy films with different initial activation temperatures on one side, either the getter alloy with a low initial activation temperature becomes dense after high-temperature activation, thereby reducing the getter capacity of the getter alloy with a high initial activation temperature at room temperature, or the getter alloy with a high initial activation temperature hinders the absorption efficiency of the alloy with a low initial activation temperature for carbon-containing gas.

2. Compared with the prior art, the thin film getter structure of the utility model can significantly shorten the activation time without affecting the air absorption capacity of the thin film getter at room temperature, and is particularly suitable for MEMS devices in which the chip is fixed by organic adhesive bonding.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

FIG1 is a schematic diagram of the structure of a thin film getter for improving the air absorption efficiency of the utility model.

In the figure: 1. Getter alloy layer with initial activation temperature less than or equal to 300°C; 2. Stainless steel, Kovar and other substrate layers; 3. Getter alloy layer with initial activation temperature greater than 300°C.

DETAILED DESCRIPTION

In order to more clearly illustrate the overall concept of the present invention, a detailed description is given below in the form of examples in conjunction with the accompanying drawings.

In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

In the present utility model, unless otherwise clearly specified and limited, the first feature "above" or "below" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. In the description of this specification, the description of reference terms "one scheme", "some schemes", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the scheme or example are included in at least one scheme or example of the present utility model. In this specification, the schematic representation of the above terms does not necessarily refer to the same scheme or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more schemes or examples.

As shown in FIG1 , an embodiment of the present utility model proposes a thin film getter structure for improving the gettering efficiency.

Example

A 2-micron titanium-zirconium-cobalt rare earth getter alloy is deposited on one side of a 0.05-mm-thick stainless steel substrate using PVD technology. The initial activation temperature of the getter alloy is 250°C. A 2-micron titanium film is deposited on the other side. The initial activation temperature of the getter material is 400°C. This is sample 1.

Example

This embodiment is suitable for comparison with the existing technology. PVD technology is used to first deposit a 1-micron layer of titanium-zirconium-cobalt rare earth getter alloy on one side of a stainless steel substrate with a thickness of 0.05 mm, and then deposit a 1-micron layer of titanium on its surface. Then, titanium-zirconium-cobalt-cerium and titanium are deposited on the other side in the same order and thickness as sample 2.

Example

This embodiment is suitable for comparison with the existing technology. PVD technology is used to first deposit a 1-micron titanium layer on one side of a 0.05-mm-thick stainless steel substrate, and then deposit a 1-micron titanium-zirconium-cobalt rare earth getter alloy layer on its surface. Then, titanium, titanium-zirconium-cobalt-cerium are deposited on the other side in the same order and thickness as sample 3.

Example

In this embodiment, CO is used as the test gas, and the constant volume method is used to test the inhalation capacity of samples 1-3. The test steps are as follows:

First, seal the sample into a vacuum chamber with a fixed volume, and then bake out the test system. After the system cools down, activate it at 450℃×30min. After the sample cools down to room temperature, fill the system with a known amount of CO. After the system pressure is balanced, measure the residual pressure inside the system. The difference between the amount filled into the system and the residual amount inside the system is the CO suction capacity of this test.

The test conditions and results (unit: Pa×L/cm2) are shown in Table 1 below:

Sample 1 0.19 Sample 2 0.17 Sample 3 0.10

Table 1

Example

In this embodiment, CO is used as the test gas, and samples 1-3 of the same area are tested for the inhalation rate using the constant volume method to simulate the actual working environment. The test steps are as follows:

First, seal the sample into a vacuum chamber with a fixed volume, and then bake and exhaust the test system. After the system cools down, fill it with 10Pa of CO, heat the getter to 450℃ and start keeping warm, and record the time required for the system pressure to drop to 0.1Pa. The shorter the time, the faster the reaction speed of the getter and the carbon-containing gas. The test results (unit: seconds) are shown in Table 1 below:

Sample 1 985 Sample 2 1782 Sample 3 976

Table 2

It can be seen from Table 2 that when the getter alloy with a low initial activation temperature is covered with the getter alloy with a high initial activation temperature, the getter alloy with a low initial activation temperature cannot take advantage of the high gettering rate due to the gas diffusion channel.

In summary, Example 4 and Example 5 show that the structure of the present invention has a faster air intake rate when activated at high temperature, and has a larger air intake capacity after cooling to room temperature, and is particularly suitable for MEMS devices in which chips are fixed by organic adhesive bonding.

Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims (2)

1. A thin film getter structure for improving gettering efficiency, characterized in that: the method comprises the steps of starting an air-absorbing alloy layer with the activation temperature less than or equal to 300 ℃, stainless steel, kovar and other basal layers and starting an air-absorbing alloy layer with the activation temperature greater than 300 ℃, wherein the stainless steel, kovar and other basal layers are two layers, and the air-absorbing films with different materials are respectively deposited on two opposite surfaces of a sheet-shaped substrate with the thickness less than 1mm, such as the stainless steel, the kovar and the like, by a PVD method.

2. A thin film getter structure for enhancing gettering efficiency as claimed in claim 1, wherein: the air suction film is provided with two sides, wherein one side is an air suction film with the initial activation temperature less than or equal to 300 ℃, and can be a titanium zirconium vanadium rare earth air suction film and a titanium zirconium cobalt rare earth air suction film, and the other side is an air suction film with the initial activation temperature greater than 300 ℃, and can be a titanium film and a zirconium film.