Low-temperature deposition method and passive vacuum maintenance film getter

Abstract

The invention relates to the field of getter alloys, and discloses a low-temperature deposition method and a passive vacuum maintenance film getter, a deposition chamber is provided, a substrate is loaded on a sample table, and the sample table is sent into the deposition chamber; introducing a first reaction gas containing boron and a second reaction gas containing carbon into the deposition chamber; turning on an RF plasma source to perform low-temperature deposition, and enabling the first reaction gas and the second reaction gas to react with sputtered metal atoms or ions by controlling the power of the RF plasma source, the partial pressure of the trimethylborane gas and the partial pressure of the methane gas, and co-depositing on the substrate to form the amorphous alloy film. According to the invention, crystallization and grain growth of the amorphous film during long-term work or subsequent thermal process are inhibited through process regulation and control, so that the high-activity structure of the amorphous substrate is stabilized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of getter alloys, in particular to a low-temperature deposition method and a passive vacuum maintenance thin film getter. BACKGROUND

[0002] Thin film getters are prepared by physical vapor deposition technology to pre-prepare a layer of thin film state getter material inside the device. This method avoids evaporation pollution, and the thin film has a larger specific surface area, which is expected to obtain a higher initial gettering rate. However, the existing thin film getter technology still faces challenges: first, in order to obtain a thin film with good crystallization and stable performance, the traditional deposition process often requires a higher substrate temperature, which is incompatible with the low-temperature packaging process of many devices; second, even if the thin film is made, it is still mostly crystalline structure, and the performance degradation problem caused by crystallization and grain growth has not been fundamentally solved, and the long-term stability is still insufficient.

[0003] Therefore, there is an urgent need in the art to develop a new type of passive vacuum maintenance thin film getter and its preparation method. The method should be able to complete the deposition at low temperature (≤200°C) to be compatible with a wider range of packaging processes; at the same time, the getter itself should have excellent structural stability, which can effectively resist the performance degradation caused by crystallization and grain growth during long-term use, thereby providing a high-activity, long-life, high-reliability vacuum maintenance solution for high-precision devices. SUMMARY

[0004] The main purpose of the present application is to solve the technical problem of performance degradation caused by grain growth in the prior art. A low-temperature deposition method, comprising the following steps: Providing a deposition chamber and loading a substrate on a sample table, and sending the sample table into the deposition chamber; Introducing a first reaction gas containing boron and a second reaction gas containing carbon into the deposition chamber; Turning on the RF plasma source for low-temperature deposition, and by controlling the power of the RF plasma source, the partial pressure of the trimethylborane gas and the partial pressure of the methane gas, the first reaction gas and the second reaction gas react with sputtered metal atoms or ions to form an amorphous alloy thin film on the substrate.

[0005] The present application also relates to a passive vacuum maintenance thin film getter prepared by the low-temperature deposition method.

[0006] The present application has the following beneficial effects: The present application can prepare a thin film structure mainly of amorphous solid solution by precisely controlling deposition parameters (such as using lower RF power and reaction gas partial pressure). The structure has the characteristics of short-range order and long-range disorder of atomic arrangement, has a large number of "free volume" and dangling bonds, and provides a large number of active sites for gas adsorption, so that the thin film exhibits extremely high initial adsorption rate and high adsorption capacity for gas without activation or only with low-temperature activation.

[0007] The present application can generate nanoscale boride and / or carbide dispersed phase in-situ in the amorphous matrix through process control. These nanoparticles can effectively pin "crystal-like boundaries" and inhibit crystallization and grain growth of the amorphous thin film during long-term operation or subsequent thermal processes (such as solder reflow), thereby stabilizing the high-activity structure of the amorphous matrix. The composite structure of "amorphous matrix + nanodispersed phase" makes the thin film getter have unprecedented anti-aging properties, ensuring the vacuum maintenance capability of the device throughout its life cycle. DETAILED DESCRIPTION

[0008] The terms "first", "second", "third", "fourth" and the like in the description and claims of the present application (if any) are used for distinguishing between similar objects and are not necessarily used to describe a particular sequential or chronological order. It is to be understood that the use of the terms so construed can interchange under appropriate circumstances. Moreover, the terms "comprising", "having", "including", and "containing" or any variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, product, or device that comprises, has, includes or contains a list of steps or elements, but not limited to only those steps or elements, but can include other steps or elements not expressly listed or inherent to such process, method, product, or device.

[0009] For the convenience of understanding, the specific process of the embodiments of the present application is described below. An embodiment of a passive vacuum maintenance thin film getter in the embodiments of the present application comprises: A deposition chamber is provided, and a substrate is loaded on a sample table, and the sample table is sent into the deposition chamber; A first reaction gas containing boron and a second reaction gas containing carbon are introduced into the deposition chamber; An RF plasma source is turned on for low-temperature deposition, and by controlling the power of the RF plasma source, the partial pressure of the trimethylborane gas, and the partial pressure of the methane gas, the first reaction gas and the second reaction gas react with sputtered metal atoms or ions to co-deposit an amorphous alloy thin film on the substrate.

[0010] As an embodiment of the present application, the amorphous alloy thin film is composed of zirconium, vanadium, iron, manganese, erbium and a metalloid element, the metalloid element includes boron and carbon, and the atomic percentage content of the metalloid element is 0.1% to 5%.

[0011] As an embodiment of the present application, the trimethylborane gas flow rate is 1% to 5% of the inert gas flow rate. The methane gas flow rate is 2% to 10% of the inert gas flow rate. A low power of 50 W to 150 W is used, and a lower reaction gas partial pressure is used to make the metalloid elements mainly exist in the form of solid solution. A high power of 200 W to 300 W is used, and a higher reaction gas partial pressure is used to promote the formation of nanoscale borides / carbides.

[0012] As an embodiment of the present application, in the preparation process, first, 200 W to 300 W of RF power and a high reaction gas partial pressure are used for deposition for 5-15 minutes, and then 50 W to 100 W of RF power and a low reaction gas partial pressure are used for deposition for 5-15 minutes.

[0013] As an embodiment of the present application, the amorphous alloy thin film is prepared by a low-temperature plasma-enhanced chemical vapor deposition process at a substrate temperature of ≤200°C.

[0014] Specifically, the method of the present application specifically comprises the following steps: Substrate pretreatment: A standard 4-inch <100> crystal direction single crystal silicon wafer is selected as the substrate.

[0015] The silicon wafer is sequentially placed in acetone and ethanol for ultrasonic cleaning for 15 minutes, respectively, to remove organic contaminants.

[0016] A standard RCA cleaning process is used to further remove inorganic impurities and particles.

[0017] After being washed with high-purity deionized water, the silicon wafer is dried with high-purity nitrogen gas and quickly loaded into the sample transfer chamber of a magnetron sputtering device.

[0018] Device and target preparation: Deposition device: A high-vacuum multifunctional magnetron sputtering system is used, which is equipped with a double-temperature-zone sample table and can realize heating and active water cooling.

[0019] Vacuum system: A molecular pump set is used to ensure that the system background vacuum can reach the high vacuum range.

[0020] Gas control system: A mass flow controller is provided to accurately control the flow rates of Ar, TMB, and methane gas.

[0021] Target: A Zr-V-Fe-Mn-Er alloy target (atomic ratio 70:20:6:2:2, purity 99.95%) with a size of Φ75mm × 3mm is installed. The distance between the target and the substrate is fixed at 70mm.

[0022] Plasma source: The plasma was excited using a 13.56 MHz radio frequency power supply.

[0023] Low-temperature deposition process steps Step 1: Create a high vacuum Transfer the sample stage, now loaded with the substrate, into the deposition chamber. Start the molecular pump assembly to evacuate the chamber to a background vacuum of ≤5.0 × 10⁻⁶. -5 Pa. This step is crucial for eliminating contamination of the membrane purity by residual gases such as water vapor and oxygen.

[0024] Step 2: Substrate Temperature Control and Stabilization The active water-cooling circulation system of the sample stage was activated to set and stabilize the substrate temperature at 180 degrees Celsius. Real-time temperature monitoring and feedback control were achieved via thermocouples attached to the back of the sample stage. Throughout the deposition process, temperature fluctuations were controlled within ±10°C.

[0025] Step 3: Introduce working gas and stabilize the gas pressure. High-purity argon gas is introduced into the chamber, and its flow rate is precisely controlled at 50 sccm using a mass flow controller. The working pressure in the chamber is stabilized at 0.5 Pa by adjusting the throttle valve.

[0026] Step 4: Pre-sputtering of target material With the substrate baffle closed, turn on the RF power supply and set the power to 150 W to pre-sputter the Zr-Ti-V target for 15 minutes. This process is used to clean the target surface, removing any possible oxides and contaminants to ensure the purity of the subsequently deposited film. After pre-sputtering, reduce the RF power to zero.

[0027] Step 5: First step deposition - High power / high partial pressure stage (10-20 minutes) Turn on the reaction gases: While maintaining the Ar gas flow rate, turn on the flow controllers for TMB and methane.

[0028] Deposition begins: The substrate baffle is opened, and timing begins deposition. Under these high-energy and high reactive gas partial pressure conditions, the sputtered metal atoms react fully with TMB and methane in the plasma, aiming to rapidly form high-density Zr-B / Ti-C nanoscale precipitates in the early stages of film growth, serving as "nuclei" or "pinning points" for subsequent amorphous matrix growth. This stage lasts for 10 minutes.

[0029] Step 6: Second deposition step - low power / low partial pressure stage (10-20 minutes) Continue deposition: After the parameter switch, continue deposition. Under this low energy and low reactive gas partial pressure condition, the metal atoms react with limited gas, mainly forming amorphous Zr-Ti-V matrix rich in solid solution B and C, and making the nano precipitates formed in the first step effectively embedded and pinned in the matrix, thus forming a stable nano composite structure.

[0030] Step 7: Deposition end and sample removal Immediately after the total deposition time is reached, turn off the RF power supply.

[0031] Turn off the mass flow controllers of TMB and methane in sequence.

[0032] Turn off the Ar gas flow controller.

[0033] Turn off the substrate shutter.

[0034] After the sample is cooled to below 80°C, fill the chamber with high-purity nitrogen to normal pressure, and remove the sample.

[0035] Definition of parameters: High power / high partial pressure parameter (Hi): RF power: 250 W TMB flow: 5% of Ar flow (2.5 sccm) Methane flow: 10% of Ar flow (5.0 sccm) Low power / low partial pressure parameter (Lo): RF power: 75 W TMB flow: 1% of Ar flow (0.5 sccm) Methane flow: 2% of Ar flow (1.0 sccm).

[0036] Example 1 1. First step (10 min): Deposition with Hi parameters.

[0037] 2. Second step (10 min): Immediately switch to Lo parameters for deposition.

[0038] Example 2 1. First step (10 min): Deposition with Hi parameters.

[0039] 2. Second step (20 min): Immediately switch to Lo parameters for deposition.

[0040] Example 3 1. First step (20 min): Deposition with Hi parameters.

[0041] 2. Second step (10 min): Switch to Lo parameter deposition immediately.

[0042] Comparative Example 1 1. First step (2 min): Use Hi parameter deposition.

[0043] 2. Second step (10 min): Switch to Lo parameter deposition immediately.

[0044] Comparative Example 2 Use Hi parameter deposition throughout for 10 minutes.

[0045] Comparative Example 3 Use Lo parameter deposition throughout for 10 minutes.

[0046] Comparative Example 4 1. First step (0 min): Use Lo parameter deposition.

[0047] 2. Second step (10 min): Switch to Hi parameter deposition immediately.

[0048] Comparative Example 5 Use compromise parameter deposition for 20 minutes: RF power: 162.5 W; TMB flow: 3% of Ar flow; Methane flow: 6% of Ar flow.

[0049] Comparative Example 6 Linearly ramp over 20 minutes: RF power: linearly ramp from 250 W to 75 W TMB flow: linearly ramp from 2.5 sccm to 0.5 sccm Methane flow: linearly ramp from 5.0 sccm to 1.0 sccm Comparative Example 7 1. First step (5 min): Hi parameter.

[0050] 2. Second step (5 min): Lo parameter.

[0051] 3. Third step (20 min): Hi parameter.

[0052] Comparative Example 8 Process as in Example 1, but with methane gas turned off throughout.

[0053] i.e. Hi (TMB only) 10 min -> Lo (TMB only) 10 min.

[0054] Performance test: Thermal stability analysis: Differential scanning calorimetry (DSC) test from 50°C to 600°C at a heating rate of 20°C / min to measure the crystallization onset temperature (Tx) and crystallization enthalpy (ΔHx).

[0055] Initial hydrogen uptake rate test: Using constant volume method, a certain amount of nitrogen gas was injected into a vacuum chamber containing fresh sample, and the pressure-time curve was recorded to calculate the initial hydrogen uptake rate (cm 3 ·s⁻ 1 ·cm⁻ 2 ).

[0056] Aging treatment: The sample was annealed at 350°C in an atmospheric environment for 30 minutes to simulate harsh long-term aging or process.

[0057] Post-aging performance test: After cooling, the initial hydrogen uptake rate (cm 3 ·s⁻ 1 ·cm⁻ 2 ) of hydrogen after aging was tested again.

[0058] The experimental results are shown in Table 1.

[0059] Table 1 From the comparison of the above experimental data, it can be seen that the Hi stage time is too short, and not enough stable nanodispersed phase is formed to pin the entire film. Although the remaining amorphous matrix itself has a high Tx, the overall structure is unstable, the energy storage is high (high ΔHx), and it crystallizes rapidly during the aging process, leading to a sharp decline in performance. High pressure and high power throughout promote the formation of a large amount of boride / carbide, excessive crystallization, resulting in insufficient amorphous active matrix, leading to extremely low initial activity. Although the remaining structure is relatively stable, its practical value is low due to the lack of active sites. In addition, when containing only boron, the Zr-B compounds formed may not be sufficient to effectively inhibit the crystallization of the amorphous matrix. The addition of carbon may form more complex and stable nanocomposite phases (such as Ti-C), which together with boron have a better pinning effect.

[0060] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalent features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A low temperature deposition method characterized by, The method comprises the following steps: providing a deposition chamber, and loading a substrate on a sample table, and sending the sample table into the deposition chamber; introducing a first reaction gas containing boron and a second reaction gas containing carbon into the deposition chamber; starting a RF plasma source for low temperature deposition, and by controlling the power of the RF plasma source, partial pressure of the trimethylborane gas, and partial pressure of the methane gas, the first reaction gas and the second reaction gas react with sputtered metal atoms or ions to co-deposit an amorphous alloy thin film on the substrate.

2. The low temperature deposition method of claim 1, wherein, The amorphous alloy thin film is composed of zirconium, vanadium, iron, manganese, erbium and metalloid elements, the metalloid elements include boron and carbon, and the atomic percentage content of the metalloid elements is 0.1% to 5%.

3. The low temperature deposition method of claim 1, wherein, The flow rate of the trimethylborane gas is 1% to 5% of the flow rate of the inert gas.

4. The low temperature deposition method of claim 1, wherein, The flow rate of the methane gas is 2% to 10% of the flow rate of the inert gas.

5. The low temperature deposition method of claim 1, wherein, During the low temperature deposition process, a low power of 50 W to 150 W and a low reaction gas partial pressure are used, so that the metalloid elements mainly exist in the form of solid solution.

6. The low temperature deposition method of claim 1, wherein, During the low temperature deposition process, a high power of 200 W to 300 W and a high reaction gas partial pressure are used, so as to promote the formation of nanoscale borides / carbonides.

7. The low temperature deposition method of claim 1, wherein, During the low temperature deposition process, first, a RF power of 200 W to 300 W and a high reaction gas partial pressure are used for deposition for 5-15 minutes, and then a RF power of 50 W to 100 W and a low reaction gas partial pressure are used for deposition for 5-15 minutes.

8. The low temperature deposition method of claim 1, wherein, The amorphous alloy thin film is prepared by a low temperature plasma enhanced chemical vapor deposition process at a substrate temperature of ≤200°C.

9. A passive vacuum maintenance thin film getter prepared by the low temperature deposition method according to any one of claims 1-8.

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