A magnetron sputtering method for preparing high bonding force aluminum oxide / silicon nitride / metal composite film

Abstract

This invention provides a magnetron sputtering method for preparing a highly bonded alumina / silicon nitride / metal composite thin film, belonging to the field of thin film material preparation technology. The magnetron sputtering method includes the following steps: Step 1, pretreating an alumina substrate to obtain a pretreated alumina substrate; Step 2, using a silicon target as the target material, preparing a silicon nitride layer on the surface of the pretreated alumina substrate by magnetron sputtering; Step 3, after forming the silicon nitride layer on the surface of the alumina substrate, directly switching the power supply to DC sputtering to prepare the metal layer: using a metal element as the target material, preparing the metal layer on the surface of the silicon nitride layer by DC sputtering. The method provided by this invention achieves strong interfacial bonding between the silicon nitride layer and the alumina substrate, and between the metal layer and the silicon nitride layer, improving the stability of the thin film structure and meeting the application requirements of high-performance devices.

Description

Technical Field

[0001] This invention relates to the field of thin film material preparation technology, and in particular to a magnetron sputtering method for preparing a high-adhesion alumina / silicon nitride / metal composite thin film. Background Technology

[0002] Alumina substrates are widely used in semiconductor devices, electronic packaging, and sensors due to their excellent high-temperature resistance, insulation, mechanical strength, and chemical stability. To impart specific functions to alumina substrates (such as surface passivation and conductive connections), a silicon nitride layer and a metal layer are often prepared on their surface: the silicon nitride layer provides insulation, corrosion resistance, and passivation protection, while the metal layer is used to realize functions such as electrical signal transmission and electrode lead-out.

[0003] Currently, the main methods for preparing silicon nitride and metal layers on alumina substrates include chemical vapor deposition (CVD) and physical vapor deposition (PVD). Among them, the silicon nitride layer prepared by CVD has a high density, but it has problems such as high processing temperature (usually exceeding 800℃), poor substrate compatibility, and easy generation of thermal stress at the substrate-film interface, which leads to a decrease in adhesion. Furthermore, after the subsequent metal layer is deposited, the metal and silicon nitride layers are prone to forming a weak bonding interface due to the large difference in interface energy and poor element diffusion.

[0004] Magnetron sputtering, as a type of PVD method, has advantages such as low process temperature, uniform film composition, easy control of deposition rate, and good compatibility with substrates, and has been gradually applied in the field of thin film preparation. However, the traditional magnetron sputtering process still faces the following technical bottlenecks when preparing silicon nitride and metal layers on alumina substrates: the presence of hydroxyl groups and adsorbed impurities on the alumina substrate surface, and the large lattice mismatch between silicon nitride and alumina, resulting in weak interfacial adhesion between the silicon nitride layer and the alumina substrate; silicon nitride is a covalent compound with low surface energy, resulting in poor spreadability of metal atoms on its surface and easy formation of island growth, which leads to insufficient adhesion between the metal layer and the silicon nitride layer; existing process parameters lack systematic optimization, and there is a lack of correlation design between process steps, resulting in unstable interface quality.

[0005] Therefore, developing a preparation method that simultaneously improves the bonding force between the silicon nitride layer and the alumina substrate, and between the metal layer and the silicon nitride layer by optimizing the magnetron sputtering process has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of existing technologies where the silicon nitride layer on an alumina substrate has weak adhesion to the substrate, and the metal layer on the silicon nitride layer. It provides a magnetron sputtering method for preparing alumina / silicon nitride / metal composite thin films with high adhesion. The method provided by this invention achieves strong interfacial bonding between the silicon nitride layer and the alumina substrate, and between the metal layer and the silicon nitride layer, improving the stability of the thin film structure and meeting the application requirements of high-performance devices.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a magnetron sputtering method for preparing a high-adhesion alumina / silicon nitride / metal composite thin film, comprising the following steps: Step 1: Pre-treat the alumina substrate to obtain the pre-treated alumina substrate; Step 2: Using a silicon target as the target material, a silicon nitride layer is prepared on the surface of the pretreated alumina substrate by magnetron sputtering; Step 3: After forming a silicon nitride layer on the surface of the alumina substrate, the power supply is directly switched to DC sputtering to prepare the metal layer: using a metal element as the target, the metal layer is prepared on the surface of the silicon nitride layer by DC sputtering.

[0008] In a preferred embodiment of the present invention, the pretreatment is as follows: the alumina substrate is ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water, dried with nitrogen after ultrasonic cleaning, and finally dried by baking.

[0009] In a preferred embodiment of the present invention, after the alumina substrate pretreatment is completed, the method further includes fixing the pretreated alumina substrate on a stage and then evacuating the vacuum, wherein the magnetron sputtering system cavity reaches 10°C during vacuuming. -3 ~10 -4 Pa.

[0010] In a preferred embodiment of the present invention, in step 2, the temperature of the alumina substrate during magnetron sputtering is 200°C to 400°C.

[0011] More preferably, in step 2, the temperature of the alumina substrate during magnetron sputtering is 200℃, 250℃, 300℃, 350℃, or 400℃.

[0012] In a preferred embodiment of the present invention, in step 2, during magnetron sputtering, the working gas in the magnetron sputtering system cavity is nitrogen and argon with a flow ratio of 1:3 to 1:5; the reaction pressure during magnetron sputtering is 0.8 to 3 Pa.

[0013] More preferably, in step 2, the reaction pressure during magnetron sputtering is 0.8 Pa, 1.0 Pa, 1.5 Pa, 2.0 Pa, 2.5 Pa, or 3 Pa.

[0014] In a preferred embodiment of the present invention, in step 2, the radio frequency power during magnetron sputtering is 100~300W, and the sputtering deposition time is 90~120min.

[0015] More preferably, in step 2, the radio frequency power during magnetron sputtering is 100W, 150W, 200W, 250W, or 300W.

[0016] More preferably, in step 2, the sputtering deposition time is 90 min, 100 min, 110 min, or 120 min.

[0017] In a preferred embodiment of the present invention, in step 3, the metallic element is copper.

[0018] In a preferred embodiment of the present invention, in step 3, the temperature of the substrate is 100°C to 200°C during DC sputtering.

[0019] More preferably, in step 3, during DC sputtering, the temperature of the substrate is 100℃, 120℃, 140℃, 160℃, 180℃, or 200℃.

[0020] In a preferred embodiment of the present invention, in step 3, during DC sputtering, the working gas is argon, and the argon gas flow rate is 15 sccm to 20 sccm; the reaction pressure during DC sputtering is 1 to 2.5 Pa.

[0021] More preferably, in step 3, the reaction pressure during DC sputtering is 1 Pa, 1.4 Pa, 1.8 Pa, 2.2 Pa, or 2.5 Pa.

[0022] In a preferred embodiment of the present invention, in step 3, the DC power during DC sputtering is 55~150W, and the sputtering deposition time is 20~40min.

[0023] More preferably, in step 3, the DC power during DC sputtering is 55W, 60W, 70W, 80W, 90W, 100W, 110W, 120W, 130W, 140W, or 150W.

[0024] More preferably, in step 3, the sputtering deposition time is 20 min, 25 min, 30 min, 35 min, or 40 min.

[0025] After sputtering, metal atoms spread and diffuse on the surface of the silicon nitride layer, forming a continuous and dense metal layer.

[0026] The present invention has excellent process compatibility. It adopts magnetron sputtering technology throughout the process, and the process temperature is controlled between 100 and 400°C to avoid the impact of high temperature on substrate performance. The process is continuous and suitable for industrial production.

[0027] The present invention discloses the following technical effects: This invention achieves excellent interfacial bonding between the silicon nitride layer and the alumina substrate, and between the metal layer and the silicon nitride layer, through specific pretreatment steps combined with specific magnetron sputtering and DC sputtering parameter settings and a continuous vacuum deposition process. Cross-cut adhesion testing showed no significant film detachment, indicating good interfacial bonding. SEM observation revealed a continuous and dense film layer, and EDS analysis confirmed uniform distribution of interfacial elements with no obvious diffusion barriers. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The image is a scanning electron microscope (SEM) image of the cross-section of the thin film prepared in Example 1 of the present invention.

[0030] Figure 2 This is a SEM image of the thin film surface prepared in Example 1 of the present invention.

[0031] Figure 3 This is a line scan image of the cross-sectional energy dispersive spectroscopy (EDS) of the thin film prepared in Example 1 of the present invention.

[0032] Figure 4 This is a SEM image of the cross-section of the thin film prepared in Comparative Example 1 of the present invention.

[0033] Figure 5 This is a SEM image of the cross-section of the thin film prepared in Comparative Example 2 of this invention. Detailed Implementation

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0036] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0037] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0038] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0039] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0040] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0041] Example 1 Step 1: Pretreatment of alumina substrate: Select an alumina substrate, first immerse it in acetone for ultrasonic cleaning for 8 minutes, then immerse it in anhydrous ethanol for ultrasonic cleaning for 8 minutes, then replace it with deionized water for ultrasonic cleaning for 10 minutes, remove it and blow it dry with nitrogen gas, and dry it at a constant temperature of 60℃ to complete the pretreatment of the alumina substrate.

[0042] Step 2: Fabrication of silicon nitride layer by magnetron sputtering: The alumina substrate is fixed on a temperature-adjustable stage, and a vacuum is drawn to bring the pressure in the magnetron sputtering system cavity to 1×10⁻⁶. -3Pa, set the substrate heating temperature to 200℃, introduce nitrogen and argon into the sputtering chamber with a nitrogen to argon volume ratio of 1:3, control the working pressure in the sputtering chamber to 1.5Pa, set the RF power to 150W, set the deposition time to 90min, and use a high-purity silicon target with a purity ≥99.99% to obtain a silicon nitride thin film.

[0043] Step 3: After sputtering the silicon nitride thin film, switch the power supply to DC sputtering to prepare the copper metal layer: a copper (99.99%) target is selected, DC sputtering is used, and the background vacuum is 1×10⁻⁶. -3 A copper metal layer was prepared by sputtering at a substrate temperature of 100℃, an argon flow rate of 15 sccm, a working pressure of 2.0 Pa, a DC power of 55 W, and a deposition time of 25 min.

[0044] Figure 1 The image shown is a scanning electron microscope (SEM) image of the cross-section of the thin film prepared in Example 1 of the present invention. It shows that the interface between the alumina substrate, the silicon nitride layer and the copper metal layer is tightly bonded and the film is continuous and dense.

[0045] Figure 2 The image shown is a SEM image of the thin film surface prepared in Example 1 of this invention, which shows that the copper metal layer has a smooth surface and uniform grains.

[0046] Figure 3 The image shows the energy dispersive spectroscopy (EDS) line scan of the thin film prepared in Example 1 of this invention, which displays the distribution of Al, Si, N and Cu elements at the interface. The transition of each element is smooth and there are no obvious abrupt changes, indicating that the interface diffusion is good.

[0047] Example 2 Step 1: Pretreatment of alumina substrate: Select an alumina substrate, first immerse it in acetone for ultrasonic cleaning for 8 minutes, then immerse it in anhydrous ethanol for ultrasonic cleaning for 8 minutes, then replace it with deionized water for ultrasonic cleaning for 10 minutes, remove it and blow it dry with nitrogen gas, and dry it at a constant temperature of 60℃ to complete the pretreatment of the alumina substrate.

[0048] Step 2: Fabrication of silicon nitride layer by magnetron sputtering: The alumina substrate is fixed on a temperature-adjustable stage, and a vacuum is drawn to achieve a pressure of 7 × 10⁻⁶ in the magnetron sputtering system cavity. -4 Pa, set the substrate heating temperature to 300℃, introduce nitrogen and argon into the sputtering chamber with a nitrogen to argon volume ratio of 1:4, control the working pressure in the sputtering chamber to 2.0Pa, set the RF power to 200W, set the deposition time to 100min, and use a high-purity silicon target with a purity ≥99.99% to obtain a silicon nitride thin film.

[0049] Step 3: After sputtering the silicon nitride thin film, switch the power supply to DC sputtering to prepare the copper metal layer: a copper (99.99%) target is selected, DC sputtering is used, and the background vacuum is 1×10⁻⁶. -3 A copper metal layer was prepared by sputtering at a substrate temperature of 150℃, an argon flow rate of 18 sccm, a working pressure of 2.0 Pa, a DC power of 80 W, and a deposition time of 35 min.

[0050] Example 3 Step 1: Pretreatment of alumina substrate: Select an alumina substrate, first immerse it in acetone for ultrasonic cleaning for 8 minutes, then immerse it in anhydrous ethanol for ultrasonic cleaning for 8 minutes, then replace it with deionized water for ultrasonic cleaning for 10 minutes, remove it and blow it dry with nitrogen gas, and dry it at a constant temperature of 60℃ to complete the pretreatment of the alumina substrate.

[0051] Step 2: Preparation of silicon nitride layer by magnetron sputtering: The alumina substrate is fixed on a temperature-adjustable stage, and a vacuum is drawn to achieve a pressure of 5 × 10⁻⁶ ppm in the magnetron sputtering system cavity. -4 Pa, set the substrate heating temperature to 400℃, introduce nitrogen and argon into the sputtering chamber with a nitrogen to argon volume ratio of 1:5, control the working gas pressure in the sputtering chamber to 2.5Pa, set the RF power to 250W, set the deposition time to 120min, use a high-purity silicon target with a purity ≥99.99%, and obtain a silicon nitride thin film.

[0052] Step 3: After sputtering the silicon nitride thin film, switch the power supply to DC sputtering to prepare the copper metal layer: a copper (99.99%) target is selected, DC sputtering is used, and the background vacuum is 1×10⁻⁶. -3 A copper metal layer was prepared by sputtering at a substrate temperature of 200℃, an argon flow rate of 20 sccm, a working pressure of 2.5 Pa, a DC power of 150 W, and a deposition time of 40 min.

[0053] Comparative Example 1 Traditional process for preparing composite thin films Step 1: Pretreatment of alumina substrate: Select an alumina substrate and wipe it with alcohol only to complete the pretreatment of the alumina substrate.

[0054] Step 2: Fabrication of silicon nitride layer by magnetron sputtering: The alumina substrate is fixed on a temperature-adjustable stage, and a vacuum is drawn to bring the pressure in the magnetron sputtering system cavity to 1×10⁻⁶. -3Pa, set the substrate heating temperature to 150℃ (below the range of this invention), introduce nitrogen and argon into the sputtering chamber, the volume ratio of nitrogen to argon is 1:2 (deviating from the ratio of this invention), control the working gas pressure in the sputtering chamber to 0.5Pa (below the range of this invention), set the RF power to 350W (above the range of this invention), set the deposition time to 60min, use a high-purity silicon target with a purity ≥99.99%, and obtain a silicon nitride thin film.

[0055] Step 3: After sputtering the silicon nitride thin film, switch the power supply to DC sputtering to prepare the copper metal layer: a copper (99.99%) target is selected, DC sputtering is used, and the background vacuum is 1×10⁻⁶. -3 Pa, substrate temperature during sputtering 80℃ (lower than the scope of this invention), argon flow rate 20 sccm, working pressure 1.0 Pa, DC power 200 W, deposition time 15 min, to prepare a copper metal layer.

[0056] SEM observation of the obtained samples ( Figure 4 The results show that there are obvious gaps between the silicon nitride layer and the substrate, and the copper layer is island-shaped with poor continuity.

[0057] Comparative Example 2 Low-temperature process for preparing composite thin films Step 1: Pretreatment of alumina substrate: Select an alumina substrate, first immerse it in acetone for ultrasonic cleaning for 8 minutes, then immerse it in anhydrous ethanol for ultrasonic cleaning for 8 minutes, then replace it with deionized water for ultrasonic cleaning for 10 minutes, remove it and blow it dry with nitrogen gas, and dry it at a constant temperature of 60℃ to complete the pretreatment of the alumina substrate.

[0058] Step 2: Fabrication of silicon nitride layer by magnetron sputtering: The alumina substrate is fixed on a temperature-adjustable stage, and a vacuum is drawn to bring the pressure in the magnetron sputtering system cavity to 1×10⁻⁶. -3 Pa, set the substrate heating temperature to 100℃ (lower than the lower limit of 200℃ of this invention), introduce nitrogen and argon into the sputtering chamber with a nitrogen to argon volume ratio of 1:3, control the working gas pressure in the sputtering chamber to 1.5Pa, set the RF power to 150W, set the deposition time to 90min, use a high-purity silicon target with a purity ≥99.99%, and obtain a silicon nitride thin film.

[0059] Step 3: After sputtering the silicon nitride thin film, switch the power supply to DC sputtering to prepare the copper metal layer: a copper (99.99%) target is selected, DC sputtering is used, and the background vacuum is 1×10⁻⁶. -3 Pa, the substrate temperature during sputtering was room temperature (unheated, 100°C lower than the lower limit of this invention), the argon flow rate was 20 sccm, the working pressure was 2.0 Pa, the DC power was 55 W, and the deposition time was 25 min, thus a copper metal layer was prepared.

[0060] The obtained sample underwent a cross-cut adhesion test, and the film showed a small amount of mesh edge peeling, resulting in an ISO rating of 2. Cross-section observation was performed using SEM. Figure 5 As can be seen, the silicon nitride layer has a relatively loose structure and microscopic gaps exist at the interface with the alumina substrate, indicating that the atomic migration ability is insufficient under low temperature conditions, and a densely bonded interface cannot be formed.

[0061] Comparative Example 3 Vacuum breaking process for preparing composite thin films Similar to Example 1, the only difference is that after sputtering the silicon nitride film, the substrate is removed from the vacuum and exposed to air for 30 minutes, and then the vacuum is re-evacuated and DC sputtered to prepare the copper metal layer.

[0062] The critical load of the obtained sample by scratch method was 10.8 N, which was about 42% lower than that of Example 1, demonstrating the key role of continuous vacuum deposition in the bonding strength.

[0063] The process conditions and performance test results of the thin films obtained in Examples 1-3 and Comparative Examples 1-3 are summarized in Table 1.

[0064] Table 1

[0065] As can be seen from Table 1, only under the specific silicon nitride layer deposition conditions and metal layer deposition conditions of this invention can a thin film with continuous and dense interface, no defects, tight bonding, and uniform film layer be obtained.

[0066] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-adhesion alumina / silicon nitride / metal composite thin film by magnetron sputtering, characterized in that, Includes the following steps: Step 1: Pre-treat the alumina substrate to obtain the pre-treated alumina substrate; Step 2: Using a silicon target as the target material, a silicon nitride layer is prepared on the surface of the pretreated alumina substrate by magnetron sputtering; Step 3: After forming a silicon nitride layer on the surface of the alumina substrate, the power supply is directly switched to DC sputtering to prepare the metal layer: using a metal element as the target, the metal layer is prepared on the surface of the silicon nitride layer by DC sputtering.

2. The magnetron sputtering preparation method of the high-adhesion alumina / silicon nitride / metal composite thin film according to claim 1, characterized in that, The pretreatment is as follows: the alumina substrate is ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water, dried with nitrogen after ultrasonic cleaning, and finally dried by baking.

3. The magnetron sputtering preparation method of the high-adhesion alumina / silicon nitride / metal composite thin film according to claim 1, characterized in that, In step 2, the temperature of the alumina substrate during magnetron sputtering is 200℃~400℃.

4. The magnetron sputtering method for preparing a high-adhesion alumina / silicon nitride / metal composite thin film according to claim 1, characterized in that, In step 2, during magnetron sputtering, the working gas in the magnetron sputtering system cavity is nitrogen and argon with a flow ratio of 1:3 to 1:5; the reaction pressure during magnetron sputtering is 0.8 to 3 Pa.

5. The magnetron sputtering preparation method of the high-adhesion alumina / silicon nitride / metal composite thin film according to claim 1, characterized in that, In step 2, the radio frequency power during magnetron sputtering is 100~300W, and the sputtering deposition time is 90~120min.

6. The magnetron sputtering preparation method of the high-adhesion alumina / silicon nitride / metal composite thin film according to claim 1, characterized in that, In step 3, the metallic element is copper.

7. The magnetron sputtering preparation method of the high-adhesion alumina / silicon nitride / metal composite thin film according to claim 1, characterized in that, In step 3, the temperature of the substrate is 100℃~200℃ during DC sputtering.

8. The magnetron sputtering method for preparing a high-adhesion alumina / silicon nitride / metal composite thin film according to claim 1, characterized in that, In step 3, during DC sputtering, the working gas is argon, and the argon gas flow rate is 15 sccm to 20 sccm; the reaction pressure during DC sputtering is 1 to 2.5 Pa.

9. The magnetron sputtering method for preparing a high-adhesion alumina / silicon nitride / metal composite thin film according to claim 1, characterized in that, In step 3, the DC power during DC sputtering is 55~150W, and the sputtering deposition time is 20~40min.

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