Method for improving resistance performance of diamond-based tantalum nitride film

Abstract

The invention provides a method for improving the performance of a diamond-based tantalum nitride film resistor, and relates to the field of resistor manufacturing. Comprising the following steps that a diamond substrate is placed on a sample table of a magnetron sputtering chamber, and the sputtering chamber is sealed and vacuumized; argon is introduced to carry out pre-sputtering on the diamond substrate under a certain power; the sample table is started to rotate, argon is introduced, the Ta target sputtering power is adjusted for sputtering, and a Ta transition layer is prepared on the surface of the diamond substrate; filling nitrogen, co-sputtering the Ta target and the rare earth target, and preparing a TaN rare earth doped film on the surface of the Ta transition layer of the diamond substrate; and the obtained TaN rare earth doped thin film is annealed. The tantalum nitride thin film is doped with rare earth elements, so that the microstructure of the thin film is changed, and a relatively low resistance temperature coefficient is kept while relatively high resistivity is obtained. The further integration of high-resistance devices is realized, and the skin effect and parasitic capacitance in a radio frequency system are weakened.

Description

Technical Field

[0001] The invention relates to the field of resistor manufacturing, and in particular to a method for improving the performance of diamond-based tantalum nitride thin film resistors. Background Art

[0002] Tantalum nitride thin film resistors, with their high stability and precision, are widely used in RF systems as microwave matching loads. As crucial power-consuming components within circuits, they shoulder the crucial mission of maintaining circuit stability and protection. By cleverly using resistors as dummy loads, they dissipate potentially harmful power through heat generation, preventing damage to other critical components. This design not only ensures stable system operation but also extends the lifespan of electronic components.

[0003] At present, the main preparation process of tantalum nitride thin film is achieved by sputtering, that is, reactive magnetron sputtering is performed using a pure Ta target in a nitrogen and argon atmosphere. The electrical properties of the film depend largely on the preparation process. For example, changing the nitrogen and argon ratio during coating can significantly change the composition of the deposited tantalum nitride, forming a nitrogen-poor phase or a nitrogen-rich phase. Among them, the nitrogen-poor phase usually has a lower resistance value, while the nitrogen-rich phase usually has a higher resistance value and resistance temperature coefficient. The resistivity of tantalum nitride film deposited by magnetron sputtering is usually the nitrogen-poor phase, with a resistivity of about 500 μΩ·cm. Although the nitrogen-rich phase has a higher resistivity (above 1000 μΩ·cm), the resistance temperature coefficient will change to a greater absolute value, which is not suitable for thin film resistors that require high stability.

[0004] For example, patent publication number CN117637270A describes a method for controlling the crystal phase of tantalum nitride films to produce high-resistivity films. Patents publication numbers CN103971874A, CN104361967A, CN109637766A, and CN104789928A all mention treating the prepared tantalum nitride films to obtain high-resistivity films. However, the methods described in these patents are all post-plating treatments, resulting in relatively complex process flows.

[0005] Patent CN115632048A uses a Ta transition layer method to reduce the TCR value of the diamond-based tantalum nitride film. The present invention further adds rare earth element doping on this basis to further reduce the TCR value while also obtaining a higher resistivity value, thereby broadening the resistance range of the resistor device. Summary of the Invention

[0006] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a method for improving the resistance performance of diamond-based tantalum nitride thin films, so as to increase the resistivity of the tantalum nitride thin films while maintaining a low resistance temperature coefficient.

[0007] The present invention provides a method for improving the performance of diamond-based tantalum nitride thin film resistors, comprising the following steps:

[0008] S1. Provide a CVD diamond substrate.

[0009] S2. Place the diamond substrate on the sample stage of the magnetron sputtering chamber, seal the sputtering chamber and evacuate it.

[0010] S3. Pre-sputtering: introducing argon gas at a certain power to pre-sputter the diamond substrate.

[0011] S4. Sputtering Ta transition layer: Start the rotation of the sample stage, introduce argon gas, adjust the sputtering power of the Ta target for sputtering, and prepare a Ta transition layer on the surface of the diamond substrate.

[0012] S5. Co-sputtering doped film: nitrogen is filled in, and Ta target and rare earth target are co-sputtered to prepare TaN rare earth doped film on the surface of Ta transition layer of diamond substrate.

[0013] S6. Annealing: Annealing the TaN rare earth doped film obtained in step S5 to obtain stable electrical properties.

[0014] Preferably, in step S1, the CVD diamond substrate is ground and polished to a roughness of ≤1.0 nm.

[0015] Preferably, in step S1, the substrate is ultrasonically cleaned in acetone, anhydrous ethanol and deionized water for 10-15 minutes respectively, and then blown dry with a nitrogen gun.

[0016] Preferably, in step S2, the sputtering chamber is evacuated to a vacuum of ≥3.0×10 -4 Pa, and heating the diamond substrate to 250-350°C, preferably 300°C.

[0017] Preferably, in step S3, the parameters for pre-sputtering are: argon flow rate of 50-150 sccm, preferably 100 sccm, RF power of 50-150 W, preferably 100 W, and pre-sputtering time of 5-15 minutes, preferably 10 minutes. The purpose of pre-sputtering is to remove contaminants and oxygen or nitrogen adsorption layers on the target surface.

[0018] Preferably, in step S4, the Ta target sputtering power is 200-300 W, preferably 250 W, the bias voltage is 50-100 V, preferably 70 V, the argon flow rate is 50-100 sccm, preferably 100 sccm, the sputtering time is 10-30 s, and the Ta transition layer thickness is 8-15 nm.

[0019] Preferably, in step S5, the rare earth target material is selected from at least one of pure lanthanum, neodymium and scandium. In the present application, the rare earth palladium and Ta are co-sputtered with different powers, aiming to obtain the best doping ratio. Too high or too low ratio of rare earth elements will lead to the deterioration of TCR value.

[0020] Preferably, in step S5, the sputtering power of the Ta target is 200-300 W, preferably 250 W, the sputtering power of the rare earth target is 50-200 W, preferably 150 W, the bias voltage is 50-100 V, preferably 70 V, and the co-sputtering time is 3-8 min.

[0021] Preferably, in step S5, the rotation speed of the sample table is 5-10 r / min, preferably 6 r / min, the sputtering pressure is 0.5-1.0 Pa, preferably 0.4 Pa, and the nitrogen partial pressure is 2%-5%, preferably 3%.

[0022] Preferably, in step S6, the temperature of the sample table is 500-600℃, preferably 550℃, and the holding time is 1-3 hours, preferably 2 hours.

[0023] The present application also provides a rare earth doped diamond-based tantalum nitride film prepared by the method.

[0024] Compared with the prior art, the present application has the following advantages:

[0025] The present application dopes the tantalum nitride film with rare earth elements, which changes the microstructure of the film through the action of the doping elements. It can be proved that the tantalum nitride film doped with rare earth elements has a higher resistivity while maintaining a lower temperature coefficient of resistance. The resistivity is improved by an order of magnitude compared with the existing undoped tantalum nitride film, reaching 1.8 mΩ·cm; the absolute value of the temperature coefficient of resistance is less than 15 ppm / K, realizing the further integration of high resistance devices and weakening the skin effect and parasitic capacitance in the radio frequency system. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in 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 only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0027] Figure 1 The left graph is the electrical performance of the tantalum nitride film of Comparative Example 1, and the right graph is the electrical performance of the doped film of Example 3;

[0028] Figure 2 The XRD pattern of the plated film of Comparative Example 1 and Example 3;

[0029] Figure 3 The EDS energy spectrum surface scan of Ta and Sc element distribution on the surface of the doped film in Example 3. DETAILED DESCRIPTION

[0030] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0031] An embodiment of the present invention provides a method for improving the performance of a diamond-based tantalum nitride thin film resistor, comprising the following steps:

[0032] S1. First, clean the CVD diamond substrate that has been polished and machined with crack grooves by ultrasonic cleaning with acetone, anhydrous ethanol, and deionized water for 15 minutes each. After taking it out, blow it dry with nitrogen and set aside;

[0033] S2. Place the diamond substrate on the sample stage of the sputtering chamber, evacuate the chamber and heat to 300°C, so that the vacuum degree is not less than 3.0×10 -4 Pa;

[0034] S3, fill with 100 sccm of argon, close the baffle for pre-sputtering, set the pre-sputtering power of the two targets to 100 W, set the bias voltage to 200 V and maintain it for 10 minutes, so that the target and sample surfaces are plasma cleaned, which is conducive to obtaining high-quality films;

[0035] S4. Set the nitrogen flow rate to 2.7 sccm, the argon flow rate to 87.3 sccm, the sample stage speed to 6 r / min, and open the baffle. Set the Ta target and rare earth element target powers to 250 W and 150 W, respectively, and the bias voltage to -70 V. Maintain the working pressure at 0.42 Pa and start co-sputtering for 5 minutes. The ionized argon gas bombards the target at high speed. The target atoms react with the nitrogen gas during flight and reach the substrate, thereby forming a doped tantalum nitride film.

[0036] S5, stop the introduction of nitrogen and argon and maintain vacuum, set the temperature to 550° C., and keep the temperature for 2 hours to anneal the doped tantalum nitride film;

[0037] S6. Continue to plate a TiW adhesion layer and a gold electrode layer on the surface of the plated doped tantalum nitride film to form an ohmic contact between the tantalum nitride and the gold, apply photoresist to the gold layer and expose it, and use a mixed solution of potassium iodide and iodine, and a mixed solution of hydrofluoric acid and hydrogen peroxide to etch the gold and TiW, respectively, so that the film forms a microwave-loaded resistor electrode shape.

[0038] Example 1

[0039] (1) The diamond substrate was ultrasonically cleaned using a tertiary solvent (acetone → ethanol → deionized water), dried with nitrogen spray, and then loaded into a magnetron sputtering device.

[0040] (2) Evacuate to the background pressure ≤3×10 -4 Pa, heat up to the set temperature of 300℃ and keep it stable.

[0041] (3) 100 sccm of argon gas was introduced to form a pre-sputtering environment, and the dual targets (Ta / RE) were simultaneously pre-sputtered at 100 W and a 200 V substrate bias was applied for 10 minutes to remove surface contaminants.

[0042] (4) The total flow rate of the argon / nitrogen mixture was 90 sccm (ratio 32.3:1), the substrate stage rotated at a constant speed of 6 rpm, the main sputtering power was configured (Ta target 250 W, rare earth target 50 W), and magnetron co-sputtering coating was performed for 5 minutes at a working pressure of 0.42 Pa.

[0043] (5) After turning off the gas source, maintain vacuum and anneal at 550°C for 2 hours, then cool to room temperature, and transfer the coated substrate to the electrode processing area.

[0044] (6) Continuously plating the TiW bonding layer and the Au conductive layer, patterning the photoresist, and then wet etching the metal layer in steps to finally form a resistor electrode structure that meets the design specifications.

[0045] Example 2

[0046] The method of Example 1 is referred to, except that: (iv) the sputtering power of the rare earth target is 100W.

[0047] Example 3

[0048] The method of Example 1 is referred to, except that: (iv) the sputtering power of the rare earth target is 150W.

[0049] Example 4

[0050] The method of Example 1 is referred to, except that: (iv) the sputtering power of the rare earth target is 200W.

[0051] Comparative Example 1

[0052] (1) The polished CVD diamond was pickled to remove inorganic residues, and then ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15 minutes respectively. After being taken out, it was blown dry with nitrogen and set aside.

[0053] (2) Place the substrate in a vacuum chamber, heat it to 300°C for 2 hours, and evacuate it to 3.0×10 -4 Below Pa.

[0054] (3) Pre-sputtering of the tantalum target: The tantalum target is sputtered using radio frequency (100 W, argon 100 sccm, 0.42 Pa, 10 min) to remove oxides on the target surface.

[0055] (4) Set the nitrogen / argon flow ratio to 2.7 sccm:87.3 sccm, the tantalum target power to 250 W, the bias voltage to -70 V, and the total sputtering time to 6 minutes. The working pressure was stabilized at 0.42 Pa, and the substrate temperature was maintained at 300°C.

[0056] (5) After sputtering, anneal the film at 550°C for 2 hours in vacuum with a cooling rate of 5°C / min to eliminate internal stress in the film.

[0057] (VI) Wet etching is used in combination with mask technology to form a microwave resistor pattern to improve pattern accuracy. Compared with Example 1, Comparative Example 1 is not doped with rare earth elements.

[0058] The performance of the films obtained in the above examples and comparative examples was tested, and the results were as follows:

[0059] Figure 1 The left figure shows the electrical properties of tantalum nitride films from Comparative Example 1, with a resistivity of 364.95 μΩ·cm and a TCR value of -357.66 ppm / K. The right figure shows the electrical properties of the doped film from Example 3, with a resistivity of 18.8 mΩ·cm and a TCR value of -10.98 ppm / K.

[0060] Figure 2 Figure 3 is the XRD spectrum of the coated films of Comparative Example 1 and Example 3, wherein the peak position of the doped film of Example 3 is shifted toward the low angle of the crystal corresponding to the doped element compared with the peak position of the undoped film of Comparative Example 1. Since TaN crystal has a smaller lattice parameter than ScN crystal, the low angle shift proves the transformation of the thin film crystal from TaN to ScN after doping.

[0061] Figure 3 The EDS spectrum of the doped film surface in Example 3 is used to scan the distribution of Ta and Sc elements. It can be seen that Ta and Sc elements are relatively evenly distributed on the film surface, proving that Sc element is stably doped into the TaN film.

[0062] Table 1 compares the electrical properties of the films produced in Examples 1-4 and Comparative Example 1. It can be seen that Example 3 has the best electrical properties. From Comparative Example 1 and Examples 1 to 4, it can be observed that with the increase in the rare earth element doping content, the resistivity shows a trend of gradual increase. This is because the rare earth doping elements act as scattering centers to reduce the mean free path of carriers; and the TCR value has the lowest value at the preferred power of 150W, which indicates that the rare earth doping elements and the TaN film have a good fit at this power. At this time, the TaN with a negative TCR value and the Sc metal with a positive TCR value neutralize each other, and the overall TCR value tends to 0. This situation can be verified in Example 4 at a higher doping power: too many doping elements cause the TCR to shift significantly toward positive values, and the overall TCR is larger than that of Example 3, seriously deviating from the ideal value of 0.

[0063] Table 1

[0064]

[0065] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for improving the performance of diamond-based tantalum nitride thin film resistors, characterized in that: The following steps are involved: S1. Providing a CVD diamond substrate; S2. Place the diamond substrate on the sample stage of the magnetron sputtering chamber, seal the sputtering chamber and evacuate it; S3, performing pre-sputtering: introducing argon gas at a certain power to pre-sputter the diamond substrate; S4. Sputtering Ta transition layer: Start the sample stage rotation, introduce argon gas, adjust the Ta target sputtering power to perform sputtering, and prepare a Ta transition layer on the surface of the diamond substrate; S5. Co-sputtering doped film: nitrogen is filled in, and Ta target and rare earth target are co-sputtered to prepare TaN rare earth doped film on the surface of Ta transition layer of diamond substrate; S6. Annealing: Annealing the TaN rare earth doped thin film obtained in step S5.

2. The method for improving the performance of diamond-based tantalum nitride thin film resistor according to claim 1, characterized in that: In step S1, the CVD diamond substrate is ground and polished to a roughness of ≤1.0 nm.

3. The method for improving the performance of diamond-based tantalum nitride thin film resistor according to claim 1, characterized in that: In step S2, the sputtering chamber is evacuated to a vacuum of ≥3.0×10 -4 Pa, and heating the diamond substrate to 250-350°C.

4. The method for improving the performance of diamond-based tantalum nitride thin film resistor according to claim 1, characterized in that: In step S3 , the parameters for pre-sputtering are: argon gas flow rate of 50-150 sccm, RF power of 50-150 W, and pre-sputtering time of 5-15 min.

5. The method for improving the performance of diamond-based tantalum nitride thin film resistor according to claim 1, characterized in that: In step S4, the Ta target sputtering power is 200-300 W, the bias voltage is 50-100 V, the argon gas flow rate is 50-100 sccm, the sputtering time is 10-30 s, and the thickness of the Ta transition layer is 8-15 nm.

6. The method for improving the performance of diamond-based tantalum nitride thin film resistor according to claim 1, characterized in that: In step S5 , the rare earth target material is selected from at least one of pure lanthanum, neodymium, and scandium.

7. The method for improving the performance of diamond-based tantalum nitride thin film resistor according to claim 1, characterized in that: In step S5, the sputtering power of the Ta target is 200-300 W, preferably 250 W, the sputtering power of the rare earth target is 50-200 W, preferably 150 W, the bias voltage is 50-100 V, and the total sputtering time is 3-8 min.

8. The method for improving the performance of diamond-based tantalum nitride thin film resistor according to claim 1, characterized in that: In step S5 , the sample stage rotation speed is 5-10 r / min, the sputtering gas pressure is 0.5-1.0 Pa, and the nitrogen partial pressure is 2%-5%.

9. The method for improving the performance of diamond-based tantalum nitride thin film resistor according to claim 1, characterized in that: In step S6, the sample stage temperature is 500-600° C., and the holding time is 1-3 hours.

10. A rare earth-doped diamond-based tantalum nitride thin film prepared by the method according to any one of claims 1 to 9.

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