阅读说明：本技术 一种吸气薄膜及其制备方法 (Getter film and preparation method thereof ) 是由 赵晨阳 杜兆富 祁焱 赵栋梁 安静 尚宏伟 于 2020-07-30 设计创作，主要内容包括：本发明属于微型器件真空封装技术领域,涉及一种吸气薄膜及其制备方法。所述吸气薄膜为吸氢薄膜；所述吸气薄膜包括生长在基体1上的金属过渡层2以及生长在所述金属过渡层2上的吸气薄膜层3；所述金属过渡层2为Cr或Fe金属薄膜,所述吸气薄膜层3的化学组成为Ti<Sub>x</Sub>Fe,其中,x表示元素的原子百分比,1≤x≤2。根据本发明的吸气薄膜具有低激活温度、优异的机械性能、与衬底结合力强以及良好的抗温度冲击性：Ti<Sub>x</Sub>Fe吸气薄膜的激活温度小于300℃,薄膜杨氏模量约为110-140GPa,硬度约为4-6GPa。(The invention belongs to the technical field of vacuum packaging of micro devices, and relates to a getter film and a preparation method thereof. The air suction film is a hydrogen suction film; the getter film comprises a metal transition layer 2 grown on a substrate 1 and a getter film layer 3 grown on the metal transition layer 2; the metal transition layer 2 is a Cr or Fe metal film, and the chemical composition of the gas-absorbing film layer 3 is Ti x Fe, wherein x represents the atomic percent of elements, and x is more than or equal to 1 and less than or equal to 2. The getter films according to the invention have low activation temperature, excellent mechanical properties, strong bonding to the substrate and good resistance to temperature shocks: ti x The activation temperature of the Fe getter film is less than 300 ℃, the Young modulus of the film is about 110-140GPa, and the hardness is about 4-6GPa。)

1. A getter film, characterized in that: the getter film comprises a metal transition layer (2) growing on a substrate (1) and a getter film layer (3) growing on the metal transition layer (2); the metal transition layer (2) is a Cr or Fe metal film, and the chemical composition of the air suction film layer (3) is Ti_xFe, wherein x represents the atomic percent of elements, and x is more than or equal to 1 and less than or equal to 2.

2. Getter film as in claim 1, wherein: the base body (1) is a silicon substrate or the inner surface of an MEMS micro device packaging cover.

3. Getter film as in claim 1, wherein: the thickness of the metal transition film layer (2) is 3nm-5nm, and the thickness of the air suction film layer (3) is 100 nm-5 mu m.

4. Getter film as in claim 3, wherein: the thickness of the air suction film layer (3) is 0.5-3 mu m.

5. Getter film as in claim 3, wherein: the thickness of the air suction film layer (3) is 1-2 mu m.

6. Getter film as in claim 1, wherein: x is more than or equal to 1 and less than or equal to 1.5.

7. Getter film as in claim 1, wherein: the metal transition layer (2) and the air suction film layer (3) are prepared through a magnetron sputtering process.

8. Getter film according to claim 2, wherein: the substrate (1) is a rough silicon wafer, the obtained air-suction film layer (3) is a rougher granular surface, and the diameter of the granules is 10-40 nm.

9. Getter film as in claim 1, wherein: the activation temperature of the air suction film is 280-300 ℃; the film absorbs hydrogen at room temperature, the Young modulus of the film is 110-150GPa, and the hardness is 4-6 GPa.

10. A method for the preparation of a getter film according to any of claims 1 to 9, wherein: the preparation method comprises the following steps:

a. cleaning the substrate (1) to remove impurities on the surface of the substrate;

b. putting the cleaned substrate (1) into magnetron sputtering equipment, vacuumizing, introducing inert gas, and heating to 18-150 ℃;

c. a Fe or Cr metal thin film sputtered on the substrate (1) by an Fe target or a Cr target;

d. by passing Ti_xSputtering Ti on Fe or Cr metal film by Fe target_xAnd the Fe gettering film layer, wherein x represents the atomic percent of elements, and x is more than or equal to 1 and less than or equal to 2.

11. The production method according to claim 10, characterized in that: the thickness of the Fe or Cr metal film is 3nm-5nm, Ti_xThe thickness of the Fe gettering film layer is 100 nm-5 μm.

12. The production method according to claim 11, characterized in that: ti_xThe thickness of the Fe gettering film layer is 0.5-3 μm.

13. The production method according to claim 11, characterized in that: ti_xThe thickness of the Fe gettering film layer is 1 μm to 2 μm.

14. The production method according to claim 10, characterized in that: x is more than or equal to 1 and less than or equal to 1.5.

15. The production method according to claim 10, characterized in that: in the step c, the purities of the Cr target and the Fe target are both higher than 99.95%, and the power densities of the Cr target and the Fe target are both 50W/pi (38cm)²。

16. The production method according to claim 10, characterized in that: in step d, Ti_xThe power density of the Fe target is 50W/pi (38cm)²～200W/π(38cm)²。

17. The production method according to claim 10, characterized in that: in step b, the purity of the inert gas is greater than or equal to 99.9999%.

Technical Field

The invention belongs to the technical field of vacuum packaging of micro devices, and particularly relates to a getter film with low activation temperature, excellent mechanical properties and good temperature impact resistance and a preparation method thereof.

Background

In recent years, with the continuous progress of Micro-Electro-Mechanical systems (MEMS), MEMS sensor technology has been rapidly developed, and MEMS devices or systems are widely used in the fields of gyroscopes, accelerometers, etc., these devices often include Mechanical moving parts such as diaphragms and cantilevers, which rotate or vibrate at a specific frequency or absorb infrared radiation to generate pulse output when operating, so that in order to meet the use requirement of the devices on Q value (the ratio of the inductance presented when an inductor operates under an ac voltage of a certain frequency to the equivalent loss resistance), the inside of the devices must be kept in a high vacuum environment to maintain a low gas viscosity coefficient and a large electron and ion mean free path, etc.

The actual air damping is related to the pressure under low pressure, and the Q value of the air damping is rapidly increased along with the increase of the vacuum degree, so that the vacuum packaging is favorable for improving the quality factor Q of the vibrating type micro-mechanical structure. The vacuum packaging provides a high-airtight vacuum environment for the MEMS device or system through the sealed cavity, and protects the sensitive elements and the electrical interconnection structure inside the vacuum packaging from being interfered and damaged by the external environment.

Since hydrogen is used in the packaging process, and the packaging material and the device material have the hydrogen evolution characteristic, in order to ensure that the residual hydrogen and the evolved hydrogen do not influence the performance of the MEMS device, a getter material is required to be placed in the device sealing process to prolong the service life of the device. Due to the particularity of MEMS devices, the block or sheet high-temperature activated getter element widely applied to the electric vacuum devices is difficult to directly transplant and use in MEMS vacuum packaging, and the material selection of the getter is requiredVarious adjustments are made in the aspects of shape and thickness design, activation process control, and the like. At present, the effective integration of the film type getter becomes the technical key of the micro-vacuum packaging process of the MEMS device, and the packaging difficulty and cost can be greatly reduced, so that the market-oriented pace of the micro-electro-mechanical system is accelerated. For example, the Chinese invention patent application No.201710579178.X (application date 2017.07.17) discloses a non-evaporable low-temperature activated zirconium-based getter film and a preparation method thereof, the invention comprises a regulating layer, a gas-absorbing layer and a protective layer which are sequentially grown on a rough monocrystalline silicon piece, wherein the gas-absorbing layer comprises 75-77 wt% of zirconium, 18-22 wt% of cobalt, 2-5 wt% of yttrium and other unavoidable impurities in terms of chemical composition in percentage by mass; the microstructure is composed of densely arranged columnar structure grains, wherein the height of the columnar structure is 100-300 nm. The technical scheme is that the Zr-based getter material mainly improves the hydrogen absorption performance of the film, the activation temperature is 300 ℃, the activation time is 20min, and the getter rate reaches 31cm³s^-1cm^-2However, the mechanical properties and temperature shock resistance of the film are not improved.

Disclosure of Invention

In view of the above technical problems, it is an object of the present invention to provide a getter film having a combination of excellent hydrogen gettering properties and excellent mechanical properties, with low activation temperature, excellent mechanical properties and good temperature shock resistance.

Another object of the present invention is to provide a process for the preparation of the above getter film.

In order to achieve the purpose, the invention provides the following technical scheme:

a getter film comprises a metal transition layer 2 grown on a substrate 1 and a getter film layer 3 grown on the metal transition layer 2; the metal transition layer 2 is a Cr or Fe metal film, and the chemical composition of the gas-absorbing film layer 3 is Ti_xFe, wherein x represents the atomic percent of elements, and x is more than or equal to 1 and less than or equal to 2.

The base body 1 is a silicon substrate or the inner surface of a MEMS micro device packaging cover.

The thickness of the metal transition film layer 2 is 3nm-5nm, and the thickness of the air suction film layer 3 is 100 nm-5 mu m.

Preferably, the thickness of the getter film layer 3 is 0.5 to 3 μm.

Further preferably, the thickness of the getter film layer 3 is 1 to 2 μm.

Preferably, 1. ltoreq. x.ltoreq.1.5.

The metal transition layer 2 and the air suction film layer 3 are prepared by a magnetron sputtering process.

The substrate 1 is a rough silicon wafer, the obtained air-breathing film layer 3 is a rougher granular surface, and the diameter of the granules is 10-40 nm.

The activation temperature of the air suction film is 280-300 ℃; the film absorbs hydrogen at room temperature, the Young modulus of the film is 110-150GPa, and the hardness is 4-6 GPa.

A method for preparing a getter film, comprising the steps of:

a. cleaning the substrate 1 to remove impurities on the surface of the substrate;

b. putting the cleaned substrate 1 into magnetron sputtering equipment, vacuumizing, introducing inert gas, and heating to 18-150 ℃;

c. a metallic film of Fe or Cr sputtered on the substrate 1 by an Fe target or a Cr target;

d. by passing Ti_xSputtering Ti on Fe or Cr metal film by Fe target_xAnd the Fe gettering film layer, wherein x represents the atomic percent of elements, and x is more than or equal to 1 and less than or equal to 2.

The thickness of the Fe or Cr metal film is 3nm-5nm, Ti_xThe thickness of the Fe gettering film layer is 100 nm-5 μm.

Preferably, Ti_xThe thickness of the Fe gettering film layer is 0.5-3 μm.

Further preferably, Ti_xThe thickness of the Fe gettering film layer is 1 μm to 2 μm.

Preferably, 1. ltoreq. x.ltoreq.1.5.

In the step c, the purities of the Cr target and the Fe target are both higher than 99.95%, and the power densities of the Cr target and the Fe target are both 50W/pi (38cm)²。

In step d, Ti_xThe power density of the Fe target is 50W/pi (38)cm)²～200W/π(38cm)²。

In step b, the purity of the inert gas is greater than or equal to 99.9999%.

Compared with the prior art, the invention has the beneficial effects that:

the getter films of the invention have a low activation temperature, excellent mechanical properties and good resistance to temperature shocks. Ti_xThe activation temperature of the Fe getter film is less than 300 ℃, hydrogen is absorbed at room temperature, the Young modulus of the film is about 110-140GPa, and the hardness is about 4-6 GPa. The rough silicon wafer is selected as the substrate, the film layer presents a rough surface appearance, the film obtains a larger specific surface area through the criss-cross interface, and the obtained air suction film keeps stable air suction performance in the air suction platform area.

Compared with the Zr-based getter material in the prior art, the TiFe film has similar hydrogen absorption and desorption performances, but has lower preparation cost and longer cycle life which can reach 2000 times. In addition, the TiFe film has more excellent mechanical property and temperature impact resistance so as to meet the packaging requirement of devices.

Drawings

FIG. 1 is a schematic view of the structure of a getter film according to the present invention;

FIG. 2 is a surface microstructure of a getter layer according to example 1 of the present invention.

Wherein the reference numerals are:

1 base body

2 transition layer of metal

3 air-breathing film layer

Detailed Description

The invention will be further described with reference to the drawings and examples, which are, however, illustrative and not limiting.

As shown in fig. 1, a getter film may include a metal transition layer 2 and a getter film layer 3. The metal transition layer 2 is a Cr or Fe metal thin film formed on the base 1 (i.e., the silicon substrate or the inner surface of the package cover), and the Cr or Fe metal thin film can improve the bonding strength between the gettering thin film layer 3 and the base 1.The chemical composition of the getter film layer 3 is Ti_xFe, wherein x represents an atomic percentage of an element, 1. ltoreq. x.ltoreq.2, preferably 1. ltoreq. x.ltoreq.1.5. The getter film layer 3 may be 1: the TiFe gettering film layer of 1 can be prepared according to the components with equal atomic percentage, and can also be a non-equal atomic percentage TiFe gettering film layer, wherein the atomic percentage of Ti is more than 1.

In some embodiments, the thickness of the Cr or Fe metal film may be 3nm to 5 nm. The Cr or Fe metal thin film having a thickness within the above range can effectively improve the bonding strength between the gettering thin film layer 3 and the substrate 1 without affecting the overall effect of the gettering thin film according to the present invention.

In some embodiments, the thickness of the getter film layer 3 may be l00nm-5 μm, preferably, the thickness of the getter film layer 3 may be 0.5 μm-3 μm, and more preferably, the thickness of the getter film layer 3 may be 1 μm-2 μm. The air suction film layer with the thickness within the range can ensure that the film has enough hydrogen suction amount on the basis of keeping the bonding force with the substrate 1, and the service life of the MEMS device is prolonged.

In some embodiments, the metal transition layer 2 is a Cr film with a thickness of 3nm, the bonding force between the Cr film and the silicon-based substrate or the MEMS package cover is good, and the thickness of 3nm is enough to realize the connection between the substrate 1 and the gettering film layer 3 without affecting the performance of the gettering film.

In some embodiments, the metal transition layer 2 is a 5nm thick Cr film, which has good adhesion to the silicon substrate or the MEMS package cover, good impact resistance at high and low temperatures, and does not affect the performance of the gettering film.

In some embodiments, the metal transition layer 2 is a 3nm thick Fe film, which has a better bonding force with the silicon-based substrate than the Cr film, and is preferably used as the transition layer in the silicon-based package.

The method for preparing the getter film of the present invention will be described below.

First, the substrate 1 is cleaned. Specifically, in some embodiments, the substrate 1 is first placed in acetone or other organic solvent, ultrasonically cleaned for 15-20min to remove oil stains on the surface, then ultrasonically cleaned with deionized water for 15-20min to remove residual acetone, then placed in absolute ethanol for dehydration, and finally dried at 80 ℃. However, the present invention is not limited thereto, and the substrate may be cleaned in other methods.

Then, the substrate 1 was heated to 18 ℃ to 150 ℃ under an inert gas atmosphere in a magnetron sputtering apparatus. Specifically, in some embodiments, the cleaned substrate 1 is loaded into a magnetron sputtering apparatus; vacuumizing to a vacuum degree of less than 5 xl 0^-7Torr; introducing inert gas to maintain the vacuum degree at 0.1 Pa-lPa; starting the heating device, and heating the substrate 1 to 18-150 ℃. Here, the inert gas may be argon gas, but the present invention is not limited thereto.

Then, a Cr metal film was sputtered on the substrate 1 by a Cr target. Specifically, in some embodiments, a DC or RF power source connected to a Cr target is turned on at a power density of 50W/π (38cm)²Sputtering for 1-15 min to form Cr metal film. An Fe metal film may also be sputtered on the substrate 1 by an Fe target. Specifically, in some embodiments, a DC or RF power source connected to the Fe target is turned on at a power density of 50W/π (38cm)²Sputtering for 5min-30min to form Fe metal film.

Then, passing through Ti_xThe power density of the Fe target is 50W/pi (38cm) under the direct current or radio frequency power supply²～200W/π(38cm)²Sputtering of Ti_xA Fe getter film. Specifically, in some embodiments, the inert gas is argon and the flow of argon is adjusted such that the sputtering chamber pressure is adjusted to between 0.3mTorr and 8 mTorr. Then the Cr target, the Fe target and the Ti are connected in an opening way_xPower supply of Fe target to produce Cr film, Fe film and Ti film_xA Fe getter film. The composition of the TiFe getter film can be adjusted by changing the composition of the target material. The flow rate of the inert gas can be adjusted by controlling the pressure of the sputtering chamber.