SAW filter copper interdigital electrode and PST structure manufacturing method and device

Abstract

The invention relates to the technical field of integrated circuit manufacturing, and particularly discloses a manufacturing method and device for a SAW filter copper interdigital electrode and a PST structure, and the method comprises the steps: sequentially carrying out the oxidation layer deposition, planarization, exposure development and dry etching on a substrate, and forming an IDT groove; forming a copper interdigital electrode in the IDT groove by adopting a chemical electroplating process; sequentially carrying out planarization and oxide layer deposition on the copper interdigital electrode, and sequentially carrying out exposure development and dry etching on areas at the two ends of the copper interdigital electrode to form a PST groove; and forming a PST structure in the PST groove by adopting a chemical electroplating process, and then flattening the PST structure. According to the invention, a chemical electroplating process is adopted, the copper interdigital electrode is formed in the IDT groove, and the PST structure is formed in the PST groove, so that the growth of the copper interdigital electrode and the PST structure is more uniform and free of holes, the generation of second harmonics is effectively inhibited, and the performance in a filter passband is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuit manufacturing, and in particular to a manufacturing method and device of a SAW filter copper interdigital electrode and a PST structure. Background Art

[0002] like Figure 1 As shown in the figure, the surface acoustic wave (SAW) filter makes input and output electrodes (Electrical Port) on the surface of the piezoelectric substrate (Piezoelectric substrate), applies an alternating voltage to the input end, and uses the piezoelectric effect to convert electrical energy into acoustic energy, namely, the interdigital transducer (IDT-Inter Digital Transducer). IDT has the advantages of low insertion loss, wide bandwidth and low cost, and is widely used in communication RF front-end modules.

[0003] In addition to propagating perpendicularly to the direction of the interdigital electrodes, the acoustic waves of the surface acoustic wave (SAW) filter also propagate in a direction parallel to the electrodes, causing transverse mode spurious in the frequency characteristics, causing disturbances in the passband, increasing device energy loss and reducing the Q value. In order to reduce the spurious effect, suppress the second harmonic, and improve the performance of the filter in the passband, it is usually practiced to thicken the areas at both ends of the interdigital electrodes (PST structure) or thicken them (hammerhead structure) to reduce the propagation speed of the end area. The top view and cross-sectional view of the interdigital electrode with PST structure are shown in the figure below. Figure 2 , Figure 3 shown.

[0004] The test shows that the admittance of the SAW filter with PST structure interdigital electrodes is significantly improved compared with the conventional SAW filter. The comparison results are as follows: Figure 4 shown.

[0005] However, the existing process for manufacturing interdigital electrodes with PST structures is prone to forming voids on the copper interdigital electrodes, affecting the overall device performance. At the same time, when manufacturing the PST structure, it is easy to cause over-etching, affecting the final PST structure, and thus failing to suppress the second harmonic and improve the performance within the filter passband.

[0006] Based on this technical background, the present invention proposes a method and device for manufacturing copper interdigital electrodes and a PST structure of a SAW filter. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention proposes a method and device for manufacturing copper interdigital electrodes and PST structures of SAW filters. The method adopts a chemical electroplating process to form copper interdigital electrodes in the IDT groove and a PST structure in the PST groove, thereby ensuring that the copper interdigital electrodes and the PST structure grow more uniformly and without voids, effectively suppressing the generation of second harmonics and improving the performance of the filter passband.

[0008] In order to achieve the above object, the present invention provides a first aspect of a method for manufacturing a SAW filter copper interdigital electrode and a PST structure, comprising:

[0009] The oxide layer is deposited, planarized, exposed and developed, and dry-etched in sequence on the substrate to form an IDT groove;

[0010] Using a chemical electroplating process to form a copper interdigital electrode in the IDT groove;

[0011] After the copper interdigital electrodes are planarized and oxide layers are deposited in sequence, exposure, development and dry etching are performed in sequence on the two end regions thereof to form PST grooves;

[0012] A chemical electroplating process is used to form a PST structure in the PST groove and then planarize the structure.

[0013] A second aspect of the present invention provides a device having a SAW filter copper interdigital electrode and a PST structure, comprising:

[0014] A substrate having an oxide layer covered on one surface;

[0015] A copper interdigital electrode, in an interdigital shape, is located in the oxide layer, and one side surface of the copper interdigital electrode is in contact with one side surface of the substrate;

[0016] The PST structure is arranged at both end regions of the copper interdigital electrode, and one surface of the PST structure contacts the other surface of the copper interdigital electrode, and the other surface of the PST structure is coplanar with the surface of the oxide layer.

[0017] The technical effects of the present invention include:

[0018] (1) The manufacturing method of the copper interdigital electrode and PST structure of the SAW filter proposed in the present invention adopts a chemical electroplating process to form a copper interdigital electrode in the IDT groove and a PST structure in the PST groove, thereby ensuring that the copper interdigital electrode and the PST structure grow more uniformly and without voids, effectively suppressing the generation of second harmonics and improving the performance of the filter in the passband.

[0019] (2) The manufacturing method of the copper interdigital electrode and PST structure of the SAW filter proposed in the present invention is to form the IDT groove and the PST groove, and then respectively perform metal tantalum sputtering to form respective copper diffusion barrier layers. At the same time, by setting the width of the PST groove to be smaller than the width of the IDT groove, it is ensured that the PST structure is completely placed on the copper interdigital electrode, thereby preventing the PST groove from being over-etched.

[0020] (3) The manufacturing method of the copper interdigital electrode and PST structure of the SAW filter proposed in the present invention further optimizes the performance of the SAW filter by flattening the surface of the oxide layer deposited on the substrate of the copper interdigital electrode and flattening the surface of the oxide layer deposited on the copper interdigital electrode after forming the PST structure.

[0021] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0023] Figure 1 The schematic diagram of the structure of the SAW filter in the manufacturing method of the copper interdigital electrodes and PST structure of the SAW filter proposed by the present invention.

[0024] Figure 2 It is a top view schematic diagram of the interdigital electrode with PST structure in the manufacturing method of the copper interdigital electrode and PST structure of the SAW filter proposed by the present invention.

[0025] Figure 3 It is a cross-sectional schematic diagram of the interdigital electrode with PST structure in the manufacturing method of the copper interdigital electrode and PST structure of the SAW filter proposed by the present invention.

[0026] Figure 4 It is a schematic diagram comparing the admittance of a conventional SAW filter and a SAW filter with interdigital electrodes having a PST structure in the method for manufacturing the copper interdigital electrodes and PST structure of the SAW filter proposed by the present invention.

[0027] Figure 5 The present invention is a schematic flow chart of the method for manufacturing the copper interdigital electrodes and PST structure of the SAW filter.

[0028] Figure 6 This is a schematic diagram of the oxide layer deposition process in a specific implementation of the method for manufacturing the copper interdigital electrodes and PST structure of the SAW filter proposed by the present invention.

[0029] Figure 7 This is a schematic diagram of the oxide layer flattening process in a specific implementation of the method for manufacturing the copper interdigital electrodes and PST structure of the SAW filter proposed by the present invention.

[0030] Figure 8 This is a schematic diagram of the exposure and development process of the oxide layer in a specific implementation of the method for manufacturing the copper interdigital electrode and PST structure of the SAW filter proposed by the present invention.

[0031] Fig. 9 This is a schematic diagram of the oxide layer dry etching process in a specific implementation of the method for manufacturing the copper interdigital electrodes and PST structure of the SAW filter proposed by the present invention.

[0032] Fig.10 This is a schematic diagram of a process of sputtering metal tantalum on an IDT groove in a specific implementation of a method for manufacturing a copper interdigital electrode and a PST structure of a SAW filter proposed by the present invention.

[0033] Fig.11 This is a schematic diagram of a process of forming copper interdigital electrodes in an IDT groove by using a chemical electroplating process in a specific embodiment of the method for manufacturing the copper interdigital electrodes and PST structure of a SAW filter proposed by the present invention.

[0034] Fig.12 This is a schematic diagram of the planarization process of the copper interdigital electrodes in a specific implementation of the method for manufacturing the copper interdigital electrodes and PST structure of the SAW filter proposed by the present invention.

[0035] Fig.13 This is a schematic diagram of a process of depositing an oxide layer on a copper interdigital electrode in a specific implementation of a method for manufacturing a copper interdigital electrode and a PST structure of a SAW filter proposed by the present invention.

[0036] Fig.14 This is a schematic top view of the exposure and development process of the oxide layer on the copper interdigital electrode in a specific implementation of the method for manufacturing the copper interdigital electrode and PST structure of the SAW filter proposed by the present invention.

[0037] Fig.15 This is a schematic diagram of a dry etching process of an oxide layer on a copper interdigital electrode in a specific implementation of a method for manufacturing a copper interdigital electrode and a PST structure of a SAW filter proposed by the present invention.

[0038] Fig.16 This is a schematic diagram of a process of sputtering metal tantalum on a PST groove in a specific implementation of a method for manufacturing a copper interdigital electrode and a PST structure of a SAW filter proposed by the present invention.

[0039] Fig.17A schematic diagram of a process of forming a PST structure in a PST groove by using a chemical electroplating process in a specific embodiment of the method for manufacturing the copper interdigital electrode and PST structure of a SAW filter proposed by the present invention.

[0040] Fig.18 This is a schematic diagram of a planarization process of a PST structure in another specific implementation of the method for manufacturing the copper interdigital electrode and PST structure of a SAW filter proposed by the present invention.

[0041] Fig.19 It is a cross-sectional schematic diagram of a specific implementation of a device with SAW filter copper interdigital electrodes and a PST structure proposed by the present invention.

[0042] Fig. 20 It is a top view schematic diagram of a specific implementation of a device with SAW filter copper interdigital electrodes and a PST structure proposed by the present invention.

[0043] Description of reference numerals:

[0044] LN-lithium niobate, SIN-silicon nitride, TC-oxide-thermal oxide layer, Oxide-oxide layer, LiNbO3substrate-lithium niobate substrate, PR-positive resist, Cu-metallic copper, Ta-metallic tantalum, M1-metal forming copper interdigital electrodes, M2-metal forming PST structure, PST-PST structure, IDT-copper interdigital electrodes. DETAILED DESCRIPTION

[0045] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0046] In the present invention, unless otherwise specified, the directional words used, such as "upper and lower", generally refer to the upper and lower parts of the device in normal use, and "inside and outside" refer to the outline of the device. In addition, the terms "first, second, third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first, second, third" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0047] The present invention provides a method for manufacturing a SAW filter copper interdigital electrode and a PST structure, such as Figure 1 As shown, including:

[0048] The IDT groove is formed by sequentially performing oxide layer deposition, planarization, exposure and development, and dry etching on the lithium niobate substrate;

[0049] A chemical plating process is used to form copper interdigital electrodes in the IDT groove;

[0050] After the copper interdigital electrodes are planarized and the oxide layer is deposited, exposure, development and dry etching are performed on the two end regions to form PST grooves;

[0051] The PST structure is formed in the PST groove by chemical plating process and then planarized.

[0052] In the present invention, a chemical electroplating process is used to form a copper interdigital electrode in the IDT groove and a PST structure in the PST groove, thereby ensuring that the copper interdigital electrode and the PST structure grow more uniformly and without voids, effectively suppressing the generation of second harmonics and improving the performance of the filter passband.

[0053] According to the present invention, after the IDT groove and the PST groove are formed, at least one of metal tantalum, titanium and titanium nitride is sputtered to form respective copper diffusion barrier layers.

[0054] According to the present invention, the width of the PST groove is smaller than the width of the IDT groove, which is used to ensure that the PST structure is completely placed on the copper interdigital electrodes and to prevent the PST groove from being over-etched.

[0055] In the present invention, after forming the IDT groove and the PST groove, metal tantalum sputtering is performed respectively to form respective copper diffusion barrier layers. At the same time, by setting the width of the PST groove smaller than the width of the IDT groove, it is ensured that the PST structure is completely placed on the copper interdigital electrode, thereby preventing the PST groove from being over-etched.

[0056] According to the present invention, the process used for planarization is chemical mechanical polishing.

[0057] According to the present invention, the planarization of the copper interdigital electrodes stops at the surface of the oxide layer deposited on the substrate.

[0058] Preferably, after forming the PST structure, planarization is performed to stop at the surface of the oxide layer deposited on the copper interdigital electrodes.

[0059] In the present invention, the performance of the SAW filter is further optimized by flattening the surface of the oxide layer deposited on the substrate by the copper interdigital electrodes and flattening the surface of the oxide layer deposited on the copper interdigital electrodes after forming the PST structure.

[0060] According to the present invention, the material of the substrate is lithium niobate or lithium tantalate;

[0061] The photoresist used for forming the PST groove exposure and development is a positive photoresist.

[0062] The present invention also provides a device having a SAW filter copper interdigital electrode and a PST structure, such as Figure 19-20 As shown, including:

[0063] A substrate having an oxide layer covered on one surface;

[0064] The copper interdigital electrode is in an interdigital shape and is located in the oxide layer, and one surface of the copper interdigital electrode contacts one surface of the substrate;

[0065] The PST structure is arranged at both end regions of the copper interdigital electrode, and one surface of the PST structure contacts the other surface of the copper interdigital electrode, and the other surface of the PST structure is coplanar with the surface of the oxide layer.

[0066] According to the present invention, both side surfaces of the copper interdigital electrode are in contact with one side surface of the substrate and one side surface of the PST structure respectively through the copper diffusion barrier layer.

[0067] According to the present invention, the wide end of a single finger of the copper interdigital electrode is larger than the width of a single PST structure.

[0068] The present invention will be described in more detail below through specific embodiments.

[0069] Example 1

[0070] like Figure 5 As shown, this embodiment provides a method for manufacturing a SAW filter copper interdigital electrode and a PST structure, comprising:

[0071] The IDT groove is formed by sequentially performing oxide layer deposition, planarization, exposure and development, and dry etching on the lithium niobate substrate. Figure 6-9 As shown;

[0072] After forming the IDT groove, metal tantalum is sputtered to form a copper diffusion barrier layer, such as Fig.10 As shown;

[0073] The copper interdigital electrodes are formed in the IDT groove by chemical plating process, such as Fig.11 As shown;

[0074] After the copper interdigital electrodes are planarized and the oxide layer is deposited, the two end regions are exposed, developed and dry-etched in turn to form a PST groove, such as Figure 12-15 As shown;

[0075] In this embodiment, after forming the PST groove, metal tantalum is sputtered to form a copper diffusion barrier layer. Fig.16 As shown;

[0076] The PST structure is formed in the PST groove by chemical plating process and then flattened. Figure 17-18 As shown;

[0077] In this embodiment, the width of the PST groove is smaller than the width of the IDT groove, which is used to ensure that the PST structure is completely placed on the copper interdigital electrode and to prevent the PST groove from being over-etched;

[0078] In this embodiment, the process used for planarization is chemical mechanical polishing;

[0079] In this embodiment, the copper interdigital electrodes are planarized to stop at the surface of the oxide layer deposited on the lithium niobate substrate;

[0080] In this embodiment, after forming the PST structure, planarization is performed to stop at the surface of the oxide layer deposited on the copper interdigital electrode;

[0081] In this embodiment, the photoresist used for exposure and development of forming the PST groove is a positive photoresist.

[0082] This embodiment provides a device having a SAW filter copper interdigital electrode and a PST structure, and its cross-sectional view and top view are respectively as shown in FIG. Fig.19 , Fig. 20 As shown ( Fig. 20 The vertical plane where the dark dashed line is located is the section), including:

[0083] A lithium niobate substrate having an oxide layer covered on one surface;

[0084] The copper interdigital electrode is in an interdigital shape and is located in the oxide layer, and one surface of the copper interdigital electrode contacts one surface of the lithium niobate substrate;

[0085] The PST structure is disposed at both end regions of the copper interdigital electrode, and one surface of the PST structure contacts the other surface of the copper interdigital electrode, and the other surface of the PST structure is coplanar with the surface of the oxide layer;

[0086] In this embodiment, both side surfaces of the copper interdigital electrode are in contact with one side surface of the lithium niobate substrate and one side surface of the PST structure respectively through the copper diffusion barrier layer;

[0087] In this embodiment, the wide end of a single interdigital finger of the copper interdigital electrode is larger than the width of a single PST structure.

[0088] In this embodiment, after the oxide layer Oxide is deposited on the substrate and planarized, an IDT groove is formed by exposure, development and dry etching, and then a chemical electroplating (ECP) process that is more uniform and void-free than the traditional physical vapor deposition (PVD) process is used to fill the metal copper electrode. After the copper is planarized, a PST groove is formed by photolithography and dry etching after an ILD deposition. Finally, the metal M2 forming the PST structure formed by chemical electroplating (ECP) and planarization is used as the PST metal layer; at the same time, a thin layer of metal tantalum Ta is deposited by a physical vapor deposition (PVD) process as a diffusion barrier layer for copper; the width of the PST groove is smaller than the width of the IDT groove, which can ensure that the PST metal layer can be completely placed on the copper interdigital electrode, and can also ensure that the etching of the oxide layer Oxide stops on the copper to prevent the oxide layer Oxide from being over-etched.

[0089] The manufacturing method of the copper interdigital electrode and PST structure of the SAW filter proposed in the embodiment of the present invention adopts a chemical electroplating process to form the copper interdigital electrode in the IDT groove and the PST structure in the PST groove, thereby ensuring that the copper interdigital electrode and the PST structure grow more uniformly and without voids, effectively suppressing the generation of second harmonics and improving the performance of the filter passband.

[0090] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for manufacturing a SAW filter copper interdigital electrode and a PST structure, characterized in that: include: The oxide layer is deposited, planarized, exposed and developed, and dry-etched in sequence on the substrate to form an IDT groove; Using a chemical electroplating process to form a copper interdigital electrode in the IDT groove; After the copper interdigital electrodes are planarized and oxide layers are deposited in sequence, exposure, development and dry etching are performed in sequence on the two end regions thereof to form PST grooves; A chemical electroplating process is used to form a PST structure in the PST groove and then planarize the structure.

2. The method according to claim 1, characterized in that After forming the IDT groove and the PST groove, at least one of metal tantalum, titanium, and titanium nitride is sputtered to form respective copper diffusion barrier layers.

3. The method according to claim 1, characterized in that The width of the PST groove is smaller than the width of the IDT groove, which is used to ensure that the PST structure is completely placed on the copper interdigital electrodes and to prevent the PST groove from being over-etched.

4. The method according to claim 1, characterized in that: The process used for planarization is chemical mechanical polishing.

5. The method according to claim 1, characterized in that The copper interdigital electrodes are planarized to stop at the surface of the oxide layer deposited on the substrate.

6. The method according to claim 1, characterized in that After forming the PST structure, planarization is performed to stop at the surface of the oxide layer deposited on the copper interdigital electrodes.

7. The method according to claim 1, characterized in that The material of the substrate is lithium niobate or lithium tantalate; The photoresist used for forming the PST groove exposure and development is a positive photoresist.

8. A device having a SAW filter copper interdigital electrode and a PST structure, characterized in that: include: A substrate having an oxide layer covered on one surface; A copper interdigital electrode, in an interdigital shape, is located in the oxide layer, and one side surface of the copper interdigital electrode is in contact with one side surface of the substrate; The PST structure is arranged at both end regions of the copper interdigital electrode, and one surface of the PST structure contacts the other surface of the copper interdigital electrode, and the other surface of the PST structure is coplanar with the surface of the oxide layer.

9. The device according to claim 8, characterized in that Both side surfaces of the copper interdigital electrode are in contact with one side surface of the substrate and one side surface of the PST structure respectively through a copper diffusion barrier layer.

10. The device according to claim 9, characterized in that The wide end of a single interdigital finger of the copper interdigital electrode is larger than the width of a single PST structure.

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