Method for improving uniformity of ferrite substrate tantalum nitride film

Abstract

The application discloses a method for improving the uniformity of a ferrite substrate PANTAN film, wherein a loading layer is formed on the surface of the ferrite substrate by magnetron sputtering a tantalum target material, and then secondary sputtering is carried out by rotating the ferrite substrate plane by 180 degrees, and the sputtering time ratio of the front and back secondary sputtering is 2:3, so that the uniformity can reach more than 90%, thereby greatly improving the uniformity of the PANTAN film on the ferrite substrate. Compared with the prior art, the method can greatly improve the uniformity and film layer quality of the PANTAN film, and is simple to operate, low in cost, high in consistency and suitable for batch production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microwave device manufacturing, and particularly relates to a method for improving the uniformity of a tantalum nitride film on a ferrite substrate. BACKGROUND

[0002] With the development of microwave devices based on ferrite, the role of tantalum nitride is becoming increasingly important, especially in microwave isolators: microwave isolators can reduce the attenuation of microwave in forward propagation, and completely absorb microwave power in reverse transmission, so the isolator is generally used as an intermediate stage of an electronic system, as an isolator device to prevent signal crosstalk. Ferrite is a kind of metal oxide with ferrimagnetic properties. In terms of electrical properties, the resistivity of ferrite is much larger than that of elemental metal or alloy magnetic material, and it also has high dielectric properties. The magnetic properties of ferrite are also reflected in high magnetic permeability at high frequency. The excellent electromagnetic properties make ferrite a widely used non-metallic magnetic material in the high-frequency weak-current field, so ferrite has high adaptability with isolators.

[0003] Among them, a two-port isolator with ferrite as a substrate is generally a load connected to one port of a three-port circulator, thereby forming a two-port isolator. The thin film microwave load determines whether the signal isolation function of the isolator is qualified, so the thin film load resistor is required to have small resistance change in a long working time and to be able to be used normally in various complex environments. As a resistive film, tantalum nitride has high melting point, small resistance temperature coefficient and high stability, so the tantalum nitride film resistor has become the best choice for the thin film load of the microwave isolator due to its good physical and electrical properties.

[0004] Tantalum nitride film is usually formed by magnetron sputtering, and the uniformity of the film thickness formed by magnetron sputtering is an important indicator for testing the film forming quality. In the orthogonal electromagnetic field, the closed magnetic field binds the electrons to move in a spiral around the target surface, and in the process of movement, a large number of argon ions are ionized by continuously impacting the working gas argon. The argon ions are accelerated to bombard the target material under the action of the electric field, and the neutral target atoms (or molecules) are sputtered to deposit on the substrate to form a film. The argon ions are accelerated to bombard the target material under the action of the electric field, so the uniform bombardment depends largely on the uniformity of the electric field. The argon ions are derived from the working gas argon continuously impacted by the closed magnetic field bound electrons in the movement, which requires uniform magnetic field and uniform working gas argon. However, in the actual magnetron sputtering device, due to the non-uniformity of the magnetic field and the working gas argon and nitrogen, the uniformity of the tantalum nitride film layer can only reach 65%. SUMMARY

[0005] The technical problem solved by the present application is to provide a method for improving the uniformity of a thin film of tantalum nitride on a ferrite substrate, so as to solve the problem of poor uniformity of a tantalum nitride film prepared by magnetron sputtering, and ensure the functional stability of microwave devices such as isolators.

[0006] To solve the above problems, the present application provides a method for improving the uniformity of a thin film of tantalum nitride on a ferrite substrate, comprising the following steps:

[0007] S1, mounting the ferrite substrate on a plate rack in a process chamber;

[0008] S2, heating and vacuumizing the process chamber;

[0009] S3, introducing argon into the process chamber and performing plasma cleaning on the ferrite substrate;

[0010] S4, introducing argon into the process chamber and performing target burning operation on the target material;

[0011] S5, introducing argon and nitrogen to prepare the first tantalum nitride thin film on the ferrite substrate;

[0012] S6, after the ferrite substrate cools down, rotating the ferrite substrate by 180° based on the original plate rack installation plane and then mounting it on the plate rack again.

[0013] Further, the step S6 further comprises the following step:

[0014] S7, repeating steps S2-S4, then continuously introducing argon with a flow rate of 50 sccm and nitrogen with a flow rate of 5 sccm into the process chamber for 2-3 min, then turning on a pulse power source with a power of 400-450 W, and after the power output is stable, opening the target material shutter for the second time to perform sputtering, and preparing the second tantalum nitride thin film on the ferrite substrate.

[0015] Further, in the step S2, after heating and vacuumizing the process chamber, the temperature in the process chamber is maintained at 200±1℃, and the background vacuum degree is not higher than 2*E-3Pa.

[0016] Further, the step S3 specifically comprises:

[0017] First, introduce argon into the process chamber with a flow rate of 200-160 sccm;

[0018] Then control the power of the radio frequency power source to maintain 150 W, and perform plasma cleaning on the ferrite substrate for 2 min.

[0019] Further, the step S4 specifically comprises:

[0020] First, introduce argon into the process chamber with a flow rate of 20 sccm;

[0021] Then, the pulse power is turned on to keep 100-150 W, and the target material is subjected to a target burning operation.

[0022] Further, the step S5 specifically comprises:

[0023] First, argon gas with a flow rate of 20 sccm is introduced into the process chamber;

[0024] Then, the pulse power of 600-650 W is turned on, and the tantalum is sputtered on the surface of the ferrite substrate for 2 min to form a bottom tantalum layer.

[0025] After the bottom tantalum layer is sputtered on the ferrite substrate, argon gas and nitrogen gas are introduced, wherein the flow rate of the argon gas is 50 sccm, the flow rate of the nitrogen gas is 5 sccm, and the argon gas and the nitrogen gas are continuously introduced for 2-3 min.

[0026] Then, the pulse power of 400-450 W is turned on, and after the power output is stable, the target baffle is opened to perform the first sputtering, and the first tantalum nitride film is prepared on the ferrite substrate.

[0027] Further, the ratio of the first sputtering time to the second sputtering time is 2:3, and the isolation resistance with a square resistance value of 40±2.5 Ω / sq is formed.

[0028] Further, the first sputtering time is 14 min, and the second sputtering time is 21 min.

[0029] Compared with the prior art, the method can greatly improve the uniformity of the tantalum nitride film on the ferrite substrate, and the method can greatly improve the uniformity and the film quality of the tantalum nitride film, and the method is simple, low in cost, high in consistency, and suitable for batch production. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0031] Figure 1 The figure shows the uniformity of the tantalum nitride film on the ferrite substrate prepared by the process of the embodiment of the present application and the conventional process. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of the present application.

[0033] It should be understood that the terms "comprising" and "including" as used in the specification and the appended claims indicate the presence of the recited features, integers, steps, operations, elements, and / or components but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0034] It should also be understood that the terms used in the present application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the present application specification and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0035] It should be further understood that the term "and / or" as used in the present application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations thereof, and includes these combinations.

[0036] Embodiment one

[0037] The embodiment provides a method for improving uniformity of a tantalum nitride film on a ferrite substrate, comprising the following steps:

[0038] S1, mounting the ferrite substrate on a plate frame of a process chamber;

[0039] S2, heating and vacuumizing the process chamber;

[0040] The specific steps are as follows: after vacuumizing treatment, the background vacuum degree in the process chamber is 2*E-3Pa; after heating treatment, the temperature in the process chamber is 200 DEG C, so as to ensure that the bonding force of the subsequent tantalum nitride film on the ferrite substrate meets the standard.

[0041] S3, introducing argon into the process chamber, and performing plasma cleaning on the ferrite substrate;

[0042] The specific steps are as follows: argon with a flow rate of 160sccm is introduced into the process chamber, and the ferrite substrate is ion cleaned for 2min by turning on a 150W radio frequency power source, so as to ensure that the surface of the ferrite substrate is clean.

[0043] S4, introducing argon into the process chamber, and performing target burning operation on the target material;

[0044] In the case of closing the shutter, the argon gas with a flow rate of 20sccm is introduced into the process chamber, and the pulse power of 150W is turned on to perform target burning for 2-3min, so as to ensure that the surface of the target is not contaminated.

[0045] S5, argon and nitrogen are introduced to prepare the first tantalum nitride film on the ferrite substrate;

[0046] Specifically, the argon gas with a flow rate of 20sccm is introduced, and the pulse power of 650W is turned on. After the gas output and power output are stable, the shutter is opened to perform tantalum layer sputtering for 2min. The tantalum layer will serve as the primer layer of the tantalum nitride film, which increases the adhesion of the tantalum nitride to the ferrite.

[0047] Among them, after sputtering the tantalum layer, the argon gas with a flow rate of 50sccm and the nitrogen gas with a flow rate of 5sccm are introduced, and the pulse power of 450W is turned on. After the gas output and power output are stable, the shutter is opened to perform tantalum nitride film sputtering for 14min. This sputtering is the first tantalum nitride layer sputtering.

[0048] S6, after the ferrite substrate is cooled, the ferrite substrate is taken out and rotated by 180° based on the original plate rack mounting plane, and then mounted on the plate rack again.

[0049] After the chamber is naturally cooled to below 100℃, the vacuum is broken, the chamber is opened, the ferrite substrate is rotated by 180° in the plane, and then mounted on the plate rack in the chamber, so that the tantalum nitride layer will not change due to temperature change.

[0050] S7, repeat steps S2-S4, then introduce the argon gas with a flow rate of 50sccm and the nitrogen gas with a flow rate of 5sccm into the process chamber for 2-3min, then turn on the pulse power of 400-450W, and then open the shutter of the target to perform the second sputtering. The second tantalum nitride film is prepared on the ferrite substrate.

[0051] The specific steps are as follows: after vacuumizing, the background vacuum degree in the process chamber is 2*E-3Pa; after heating, the temperature in the process chamber is 200℃, so that the subsequent tantalum nitride film layer structure is consistent.

[0052] Then, the argon gas with a flow rate of 160sccm is introduced, and the radio frequency power of 150W is turned on to perform ion cleaning for 2min, so as to ensure that the surface of the substrate is clean.

[0053] In the case of closing the shutter, the argon gas with a flow rate of 20sccm is introduced, and the pulse power of 150W is turned on to perform target burning for 2-3min, so as to ensure that the surface of the target is not contaminated.

[0054] Then the flow rate of argon is 50sccm, the flow rate of nitrogen is 5sccm, and the pulse power of 450W is turned on. After the gas output and the power output are stable, the shutter is opened, and the tantalum nitride film sputtering is performed for 21min. This sputtering is the second tantalum nitride layer sputtering.

[0055] The ratio of the first sputtering time to the second sputtering time is 2:3. This ratio can ensure that the tantalum nitride film layer structure is stable, and the uniformity of the film is improved.

[0056] After the film layer is prepared, the sheet resistance of the film layer is tested by a four-probe sheet resistance meter. The sheet resistance of multiple test points of the film layer is tested, and the uniformity of the film layer is calculated using the following formula:

[0057] Film layer uniformity=(sheet resistance maximum-sheet resistance minimum) / 2*sheet resistance average

[0058] The ferrite 1 is selected for corresponding testing, and the test results are as follows:

[0059]

[0060]

[0061] According to the corresponding test results of example one, the sheet resistance value of the sputtered tantalum nitride film can be 40±2.5Ω / sq.

[0062] Example two

[0063] The embodiment provides a method for improving the uniformity of a tantalum nitride film on a ferrite substrate, comprising the following steps:

[0064] S1, mounting the ferrite substrate on the rack of the process chamber;

[0065] S2, heating and vacuumizing the process chamber;

[0066] The specific steps are: after vacuumizing, the base vacuum degree in the process chamber is 2*E-3Pa; after heating, the temperature in the process chamber is 200℃, so that the bonding force of the subsequent tantalum nitride film on the ferrite substrate meets the standard.

[0067] S3, introducing argon into the process chamber and performing plasma cleaning on the ferrite substrate;

[0068] The specific steps are: introducing argon into the process chamber at a flow rate of 160sccm, and turning on the radio frequency power of 150W to perform ion cleaning on the ferrite substrate for 2min, so that the surface of the ferrite substrate is clean.

[0069] S4, introducing argon into the process chamber and performing target burning operation on the target material;

[0070] In the case of closing the shutter, the argon gas with a flow rate of 20sccm is introduced into the process chamber, and the pulse power of 150W is turned on to perform target burning for 2-3min, so as to ensure that the surface of the target is not contaminated.

[0071] S5, argon and nitrogen are introduced to prepare the first tantalum nitride film on the ferrite substrate;

[0072] Specifically, the argon gas with a flow rate of 20sccm is introduced, and the pulse power of 650W is turned on. After the gas output and the power output are stable, the shutter is opened to perform tantalum layer sputtering for 2min. The tantalum layer will serve as the primer layer of the tantalum nitride film, which increases the adhesion of the tantalum nitride to the ferrite.

[0073] Among them, after sputtering the tantalum layer, the argon gas with a flow rate of 50sccm and the nitrogen gas with a flow rate of 5sccm are introduced, and the pulse power of 450W is turned on. After the gas output and the power output are stable, the shutter is opened to perform tantalum nitride film sputtering for 16min. This sputtering is the first tantalum nitride layer sputtering.

[0074] S6, after the ferrite substrate is cooled, the ferrite substrate is taken out and rotated by 180° based on the original plate rack installation plane, and then installed on the plate rack again.

[0075] After the chamber is naturally cooled to below 100℃, the vacuum is broken, the chamber is opened, the ferrite substrate is rotated by 180° in the plane, and then installed on the plate rack in the chamber, so that the tantalum nitride layer will not change due to temperature change.

[0076] S7, repeat steps S2-S4, then introduce the argon gas with a flow rate of 50sccm and the nitrogen gas with a flow rate of 5sccm into the process chamber for 2-3min, then turn on the pulse power of 400-450W, and then open the shutter of the target to perform the second sputtering. The second tantalum nitride film is prepared on the ferrite substrate.

[0077] The specific steps are as follows: after vacuumizing, the background vacuum degree in the process chamber is 2*E-3Pa; after heating, the temperature in the process chamber is 200℃, so as to ensure that the subsequent tantalum nitride film has consistent film layer structure.

[0078] Then, the argon gas with a flow rate of 160sccm is introduced, and the radio frequency power of 150W is turned on to perform ion cleaning for 2min, so as to ensure that the surface of the substrate is clean.

[0079] In the case of closing the shutter, the argon gas with a flow rate of 20sccm is introduced, and the pulse power of 150W is turned on to perform target burning for 2-3min, so as to ensure that the surface of the target is not contaminated.

[0080] Then the flow rate of argon is 50sccm, the flow rate of nitrogen is 5sccm, and the pulse power of 450W is turned on, and after the gas output and power output are stable, the shutter is opened, and the tantalum nitride film sputtering is carried out for 24min, and this sputtering is the second tantalum nitride layer sputtering.

[0081] The ratio of the first sputtering time to the second sputtering time is 2:3, which can ensure that the tantalum nitride film layer structure is stable, and the uniformity of the film is improved.

[0082] After the film layer is prepared, the square resistance of the film layer is tested by a four-probe square resistance meter, the square resistance of multiple test points of the film layer is tested, and the uniformity of the film layer is calculated by the following formula:

[0083] Film layer uniformity=(square resistance maximum-square resistance minimum) / 2* square resistance average

[0084] The ferrite 2 is selected for corresponding test, and the test results are as follows:

[0085]

[0086]

[0087] According to the test results of example two, the square resistance value of the sputtered tantalum nitride film can be 26.5±2.5Ω / sq.

[0088] The uniformity of the tantalum nitride film on the ferrite substrate prepared by the process of the present application is compared with the uniformity of the tantalum nitride film prepared by the conventional process, as shown in the following figure: Figure 1

[0089] The uniformity of the tantalum nitride film layer prepared by conventional magnetron sputtering is 65%, and the uniformity of the tantalum nitride film on the ferrite substrate prepared by the process of the present application can reach more than 90%, so the uniformity and quality of the tantalum nitride film are greatly improved.

[0090] The specific embodiments of the application are described in detail above, but they are only examples, and the present application is not limited to the specific embodiments described above. Any equivalent modification or substitution of the present application made by those skilled in the art is also within the scope of the present application, therefore, equivalent changes, modifications, improvements, etc. made without departing from the spirit and principle range of the present application should be covered within the scope of the present application.​

Claims

1. A method for improving the uniformity of a tantalum nitride film on a ferrite substrate, comprising: The method comprises the following steps: S1, mounting the ferrite substrate on a plate frame of a process chamber; S2, heating and vacuumizing the process chamber; S3, first introducing argon gas with a flow rate of 200-160sccm into the process chamber, then controlling the power of the radio frequency power supply to keep 150W, and performing plasma cleaning on the ferrite substrate for 2min; S4, first introducing argon gas with a flow rate of 20sccm into the process chamber, then turning on the power of the pulse power supply to keep 100-150W, and performing target burning operation on the target material; S5, first introducing argon gas with a flow rate of 20sccm into the process chamber, then turning on the pulse power supply with a power of 600-650W, and continuously sputtering tantalum on the surface of the ferrite substrate to deposit a bottom tantalum layer for 2min; after the bottom tantalum layer is formed on the ferrite substrate by sputtering, argon gas and nitrogen gas are introduced, wherein the flow rate of the argon gas is 50sccm, the flow rate of the nitrogen gas is 5sccm, the introduction lasts for 2-3min, then the pulse power supply with a power of 400-450W is turned on, the target material shutter is opened after the output of the power supply is stabilized, and the first sputtering is performed to prepare the first tantalum nitride film on the ferrite substrate; S6, after the ferrite substrate is cooled, the ferrite substrate is taken out, rotated by 180°, and then mounted on the plate frame again; S7, repeating steps S2-S4, then continuously introducing argon gas with a flow rate of 50sccm and nitrogen gas with a flow rate of 5sccm into the process chamber for 2-3min, then turning on the pulse power supply with a power of 400-450W, and performing the second sputtering after the output of the power supply is stabilized to prepare the second tantalum nitride film on the ferrite substrate.

2. The method of claim 1, wherein, In step S2, after the process chamber is heated and vacuumized, the temperature in the process chamber is kept at 200±1℃, and the background vacuum degree is not higher than 2*E-3Pa.

3. The method of claim 2, wherein, The ratio of the first sputtering time to the second sputtering time is 2:3, and the isolation resistance with a square resistance value of 40±2.5Ω / sq is formed.

4. The method of claim 3, wherein, The first sputtering time is 14min, and the second sputtering time is 21min.

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