Method and device for manufacturing SAW filter PST structure and interdigital electrode through metal tungsten

Abstract

The invention relates to the technical field of integrated circuit manufacturing, and particularly discloses a method and device for manufacturing a SAW filter PST structure and an interdigital electrode through metal tungsten, 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 interdigital groove; performing chemical vapor deposition on metal tungsten in the interdigital groove to form an interdigital electrode with a PST structure, and then performing planarization; the interdigital of each interdigital electrode with the PST structure comprises an IDT main body and a PST structure, the two ends of the IDT main body are provided with the PST structures, and the two ends of the IDT main body and the PST structures at the two ends jointly form an I shape. According to the method, the interdigital electrode with the PST structure is formed by chemical vapor deposition of metal tungsten in the interdigital groove and then is flattened, the line width uniformity and the roughness are better than those of a traditional negative photoresist stripping process, the method is more suitable for manufacturing denser interdigital electrodes, secondary harmonics are effectively restrained, and the performance in a filter passband is improved.

Description

Technical Field

[0001] The invention relates to the technical field of integrated circuit manufacturing, and in particular to a method and device for manufacturing a SAW filter PST structure and interdigital electrodes by using metal tungsten. Background Art

[0002] like Figure 1 As shown, 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, an interdigital transducer (IDT-Inter Digital Transducer). This device is cheaper than a bulk acoustic wave (BAW) filter and smaller in size than traditional cavity and ceramic filters.

[0003] A variety of metals with different electromechanical coupling coefficients and reflection coefficients can be used to make IDT electrodes. The inventors have found that metal tungsten has better step coverage and gap filling capabilities than aluminum and copper, and also has strong resistance to electromigration and corrosion. It is possible to consider using a covering tungsten plug to make IDT electrodes. The comparison of different IDT metals and electromechanical coupling coefficients is shown in Figure 2. Figure 2 As shown, the reflection coefficient comparison of different IDT metals and electrodes is Figure 3 shown.

[0004] 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 within 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 within 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 a PST structure are shown in the figure below. Figure 4 , Figure 5 shown.

[0005] 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.

[0006] However, the existing process for manufacturing interdigital electrodes with PST structure is prone to forming voids on the copper interdigital electrodes, affecting the overall device performance. At the same time, the traditional negative photoresist stripping process is prone to cause the risk of photolithography sol and wet-process tank metal contamination, affecting the final PST structure, and thus failing to suppress the second harmonic and improve the performance of the filter passband.

[0007] Based on this technical background, the present invention proposes a method and a device for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention proposes a method and device for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten. The method forms interdigital electrodes with a PST structure by chemical vapor deposition of metal tungsten in the interdigital grooves and then flattens them. The line width uniformity and roughness are better than those of the traditional negative photoresist stripping process, and the method is more suitable for making denser interdigital electrodes, effectively suppressing the second harmonic and improving the performance of the filter in the passband.

[0009] In order to achieve the above object, the first aspect of the present invention provides a method for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten, comprising:

[0010] Depositing an oxide layer, planarizing, exposing and developing, and dry etching are sequentially performed on the substrate to form interdigital grooves;

[0011] Chemically vapor depositing metal tungsten in the interdigital grooves to form interdigital electrodes with a PST structure and then planarizing the electrodes;

[0012] Each interdigital electrode with a PST structure includes an IDT body and a PST structure. The PST structure is disposed at both ends of the IDT body and forms an I-shape together with the PST structures at both ends.

[0013] The second aspect of the present invention provides a device for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten, comprising:

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

[0015] The interdigitated electrode with a PST structure is in an interdigitated shape and is formed by chemical vapor deposition of metal tungsten. The interdigitated electrodes of each interdigitated electrode with a PST structure include an IDT body and a PST structure. Both ends of the IDT body are provided with PST structures, and together with the PST structures at both ends, an I-shape is formed. The interdigitated electrode with a PST structure is located in the oxide layer, and one side surface thereof is in contact with one side surface of the substrate.

[0016] The technical effects of the present invention include:

[0017] (1) The method of using metal tungsten to manufacture the PST structure and interdigital electrodes of the SAW filter proposed in the present invention forms interdigital electrodes with a PST structure by chemical vapor deposition of metal tungsten in the interdigital grooves and then flattens them. The line width uniformity and roughness are better than those of the traditional negative photoresist stripping process, and the method is more suitable for making denser interdigital electrodes, effectively suppressing the second harmonic and improving the performance of the filter in the passband.

[0018] (2) The present invention proposes a method for manufacturing a SAW filter PST structure and an interdigitated electrode using metal tungsten. The silane reduction reaction of tungsten is used to ensure stable cohesion of tungsten and dense filling without voids and gaps. The hydrogen reduction reaction of tungsten is used to ensure that tungsten has better step coverage ability, and to prevent premature sealing of embolism caused by local excessive deposition of tungsten, thereby ultimately obtaining a dense tungsten plug.

[0019] (3) The method of using metal tungsten to manufacture the PST structure and interdigital electrodes of a SAW filter proposed in the present invention utilizes the reduction reaction in chemical vapor deposition to deposit metal tungsten, and the step coverage rate can reach 100%. By flattening the surface of the oxide layer deposited on the substrate while forming the interdigital electrodes with the PST structure, a dense metal tungsten interdigital electrode with the PST structure is formed. Compared with the traditional IDT stripping process, it can effectively avoid the risk of photolithography sol and wet-process groove metal contamination.

[0020] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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.

[0022] Figure 1 The schematic diagram of the structure of the SAW filter in the method of manufacturing the SAW filter PST structure and interdigital electrodes using metal tungsten proposed by the present invention.

[0023] Figure 2 This is a schematic diagram comparing the electromechanical coupling coefficients of different IDT metals in the method of manufacturing the SAW filter PST structure and interdigital electrodes using metal tungsten proposed by the present invention.

[0024] Figure 3 This is a schematic diagram comparing the reflection coefficients of different IDT metals and electrodes in the method of manufacturing the SAW filter PST structure and interdigital electrodes using metal tungsten proposed by the present invention.

[0025] Figure 4This is a schematic top view of the interdigital electrodes with PST structure in the method for manufacturing the PST structure and interdigital electrodes of a SAW filter using metal tungsten proposed by the present invention.

[0026] Figure 5 It is a cross-sectional schematic diagram of the interdigital electrode with PST structure in the method of manufacturing the PST structure and interdigital electrode of the SAW filter using metal tungsten proposed by the present invention.

[0027] Figure 6 It is a schematic diagram comparing the admittance of a conventional SAW filter and a SAW filter with interdigital electrodes of a PST structure in the method of manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten proposed by the present invention.

[0028] Figure 7 The figure is a flow chart of the method for manufacturing the SAW filter PST structure and interdigital electrodes by using metal tungsten proposed by the present invention.

[0029] Figure 8 This is a schematic diagram of the oxide layer deposition process in a specific implementation of the method for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten proposed by the present invention.

[0030] Fig. 9 This is a schematic diagram of the oxide layer flattening process in a specific implementation of the method for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten proposed by the present invention.

[0031] Fig.10 This is a schematic top view of the exposure and development process of the oxide layer in a specific implementation of the method for manufacturing the SAW filter PST structure and interdigital electrodes using metal tungsten proposed by the present invention.

[0032] Fig.11 This is a cross-sectional schematic diagram of the exposure and development process of the oxide layer in a specific implementation of the method for manufacturing the SAW filter PST structure and interdigital electrodes using metal tungsten proposed by the present invention.

[0033] Fig.12 This is a schematic diagram of the oxide layer dry etching process in a specific implementation of the method for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten proposed by the present invention.

[0034] Fig.13 This is a schematic diagram of a process of sputtering metal titanium on interdigital grooves in a specific implementation of a method for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten proposed by the present invention.

[0035] Fig.14This is a schematic diagram of a process of chemical vapor deposition of metal tungsten in interdigital grooves in a specific embodiment of the method for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten proposed by the present invention.

[0036] Fig.15 This is a schematic diagram of a planarization process of an interdigital electrode having a PST structure in a specific implementation of a method for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten proposed by the present invention.

[0037] Fig.16 This is a top view schematic diagram of a device for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten proposed by the present invention.

[0038] Description of reference numerals:

[0039] LN-lithium niobate, SIN-silicon nitride, TC-oxide-thermal oxide layer, Oxide-oxide layer, LiNbO3substrate-lithium niobate substrate, PR-positive photoresist, W-metal tungsten, Ti-metal titanium, PST-PST structure, IDT-IDT body. DETAILED DESCRIPTION

[0040] 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.

[0041] 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.

[0042] The present invention provides a method for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten. Figure 7 As shown, including:

[0043] Depositing an oxide layer, planarizing, exposing and developing, and dry etching are sequentially performed on the substrate to form interdigital grooves;

[0044] Chemical vapor deposition of metal tungsten in the interdigital grooves forms interdigital electrodes with a PST structure and then flattens the electrodes;

[0045] Each interdigital electrode with a PST structure includes an IDT body and a PST structure. The PST structure is disposed at both ends of the IDT body and forms an I-shape together with the PST structures at both ends.

[0046] In the present invention, by chemically vapor depositing metal tungsten in the interdigital grooves to form interdigital electrodes with a PST structure and then flattening them, the line width uniformity and roughness are better than those of the traditional negative photoresist stripping process, and it is more suitable for making denser interdigital electrodes, effectively suppressing the second harmonic and improving the performance of the filter passband.

[0047] According to the present invention, after the interdigital grooves are formed, at least one of metal titanium, tantalum and titanium nitride is further used for sputtering;

[0048] Titanium nitride formed by sputtering of titanium metal is used to assist adhesion and also serves as a barrier layer for tungsten metal.

[0049] According to the present invention, chemical vapor deposition of metal tungsten includes:

[0050] First, a thin layer of tungsten is formed as a nucleation layer by using a silane reduction reaction of tungsten, and then a tungsten body is deposited by using a hydrogen reduction reaction of tungsten;

[0051] The thickness of the thin layer of tungsten is 30-100 nm.

[0052] In the present invention, the silane reduction reaction of tungsten is used to ensure the stable cohesion of tungsten and to ensure dense filling without voids and gaps; the hydrogen reduction reaction of tungsten is used to ensure that tungsten has better step coverage ability, prevent embolism caused by local excessive deposition of tungsten body and premature sealing, and finally obtain a dense tungsten plug.

[0053] According to the present invention, the chemical equation for the silane reduction reaction of tungsten is:

[0054] 2WF6(gas)+3SiH4(gas)------->2W(solid)+3SiF4(gas)+6H2(gas);

[0055] The chemical equation for the hydrogen reduction reaction of tungsten is:

[0056] WF6(gas)+3H2(gas)------->W(solid)+6HF(gas).

[0057] According to the present invention, the silane reduction reaction of tungsten is used to ensure stable agglomeration of tungsten and to ensure dense filling without voids and gaps;

[0058] The hydrogen reduction reaction of tungsten is used to ensure that tungsten has better step coverage ability and prevent premature sealing of embolism caused by local excessive deposition of tungsten body.

[0059] Preferably, the process used for planarization is chemical mechanical polishing;

[0060] The interdigitated electrodes with the PST structure are formed to flatten the surface of the oxide layer deposited on the substrate;

[0061] The surface of the oxide layer deposited on the substrate is planarized and used as an auxiliary temperature compensation film layer to ensure that it has no effect on the uniformity of the subsequent temperature compensation film layer process.

[0062] According to the present invention, the material of the substrate is lithium niobate or lithium tantalate;

[0063] The photoresist used for forming the interdigitated grooves, exposing and developing is a positive photoresist.

[0064] In the present invention, metal tungsten is deposited by utilizing the reduction reaction in chemical vapor deposition, and the step coverage rate can reach 100%. By flattening the surface of the oxide layer deposited on the substrate while forming the interdigitated electrode with the PST structure, a dense metal tungsten interdigitated electrode with the PST structure is formed. Compared with the traditional IDT stripping process, the risk of photolithography sol and wet-process groove metal contamination can be effectively avoided.

[0065] The present invention provides a device for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten, comprising:

[0066] A substrate having an oxide layer covered on one surface;

[0067] The interdigitated electrode with a PST structure is in an interdigitated shape and is formed by chemical vapor deposition of metal tungsten. The interdigitated electrodes of each interdigitated electrode with a PST structure include an IDT body and a PST structure. Both ends of the IDT body are provided with PST structures, and together with the PST structures at both ends, an I-shape is formed. The interdigitated electrode with a PST structure is located in the oxide layer, and one side surface thereof is in contact with one side surface of the substrate.

[0068] According to the present invention, one side surface of the interdigital electrode having the PST structure contacts one side surface of the substrate through the metal tungsten barrier layer.

[0069] According to the present invention, chemical vapor deposition of metal tungsten first utilizes silane reduction reaction of tungsten to form a thin layer of tungsten as a nucleation layer, and then utilizes hydrogen reduction reaction of tungsten to deposit the tungsten body, so as to ensure that a dense tungsten plug is obtained.

[0070] The present invention will be described in more detail below through specific embodiments.

[0071] Example 1

[0072] like Figure 7 As shown, this embodiment provides a method for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten, including:

[0073] The oxide layer deposition, planarization, exposure and development, and dry etching are sequentially performed on the lithium niobate substrate to form interdigital grooves, such as Figure 8-12 As shown, Fig.10 This is a top view of the oxide layer exposure and development process. Fig.11 It is a cross-sectional view of the exposure and development process of the oxide layer;

[0074] In this embodiment, after the interdigital grooves are formed, titanium sputtering is also performed. Fig.13 As shown;

[0075] The interdigital electrodes with PST structure are formed by chemical vapor deposition of metal tungsten in the interdigital grooves and then planarized. Fig.14 and Fig.15 As shown;

[0076] Each interdigital electrode having a PST structure includes an IDT body and a PST structure. The PST structure is disposed at both ends of the IDT body and forms an I-shape together with the PST structures at both ends. Fig.10 As shown;

[0077] In this embodiment, titanium nitride formed by sputtering of metal titanium is used to assist adhesion and also serves as a barrier layer for metal tungsten;

[0078] In this embodiment, chemical vapor deposition of metal tungsten includes:

[0079] First, a thin layer of tungsten is formed as a nucleation layer by using a silane reduction reaction of tungsten, and then a tungsten body is deposited by using a hydrogen reduction reaction of tungsten;

[0080] The thickness of the thin layer of tungsten is 30-100nm;

[0081] In this embodiment, the chemical equation for the silane reduction reaction of tungsten is:

[0082] 2WF6(gas)+3SiH4(gas)------->2W(solid)+3SiF4(gas)+6H2(gas);

[0083] The chemical equation for the hydrogen reduction reaction of tungsten is:

[0084] WF6(gas)+3H2(gas)------->W(solid)+6HF(gas);

[0085] In this embodiment, the silane reduction reaction of tungsten is used to ensure stable agglomeration of tungsten and to ensure dense filling without voids and gaps;

[0086] The hydrogen reduction reaction of tungsten is used to ensure that tungsten has better step coverage ability and prevent premature sealing of embolism caused by local excessive deposition of tungsten body;

[0087] In this embodiment, the process used for planarization is chemical mechanical polishing;

[0088] The interdigitated electrode with the PST structure is formed to flatten the surface of the oxide layer deposited on the lithium niobate substrate;

[0089] The flattening stops at the surface of the oxide layer deposited on the lithium niobate substrate, which is used as an auxiliary temperature compensation film layer to ensure that there is no impact on the uniformity of the subsequent temperature compensation film layer process;

[0090] In this embodiment, the photoresist used for exposure and development of forming the interdigitated grooves is a positive photoresist.

[0091] The present invention provides a device for manufacturing a SAW filter PST structure and interdigital electrodes using metal tungsten, such as Fig.16 As shown, including:

[0092] A lithium niobate substrate having an oxide layer covered on one surface;

[0093] The interdigitated electrodes with a PST structure are interdigitated and formed by chemical vapor deposition of metal tungsten. Each interdigitated electrode with a PST structure includes an IDT body and a PST structure. Both ends of the IDT body are provided with PST structures, and together with the PST structures at both ends, they form an I-shaped structure. The interdigitated electrodes with a PST structure are located in the oxide layer, and one side surface of the interdigitated electrodes contacts one side surface of the lithium niobate substrate through a metal tungsten barrier layer.

[0094] In this embodiment, chemical vapor deposition of metal tungsten first utilizes a silane reduction reaction of tungsten to form a thin layer of tungsten as a nucleation layer, and then utilizes a hydrogen reduction reaction of tungsten to deposit a tungsten body, so as to ensure that a dense tungsten plug is obtained.

[0095] In this embodiment, after the oxide layer Oxide is deposited on the substrate and planarized, photolithography and dry etching are used to form interdigital grooves including an IDT body and a PST structure. The line width uniformity and roughness are better than those of the traditional negative photoresist stripping process, and it is more suitable for making denser interdigital electrodes. Chemical vapor deposition (CVD) reduction reaction is used to deposit metal tungsten with a step coverage of 100%. After the metal tungsten is planarized to the oxide layer Oxide, a dense interdigital electrode with a PST structure is formed. Compared with the traditional IDT stripping process, the risk of photolithography sol and wet-process groove metal contamination can be avoided. The retained oxide layer Oxide after the oxide layer Oxide is planarized can be used as a part of the temperature compensation film layer, because the prior planarization has no effect on the uniformity of the subsequent temperature compensation film layer process. In order to ensure that a dense tungsten plug is obtained, a combination of silane reduction reaction and hydrogen reduction reaction is used to deposit metal tungsten.

[0096] The method for manufacturing the PST structure and interdigital electrodes of a SAW filter using metal tungsten proposed in an embodiment of the present invention forms interdigital electrodes with a PST structure by chemical vapor deposition of metal tungsten in the interdigital grooves and then flattens them. The line width uniformity and roughness are better than those of the traditional negative photoresist stripping process, and the method is more suitable for making denser interdigital electrodes, effectively suppressing the second harmonic and improving the performance of the filter in the passband.

[0097] 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 PST structure and interdigital electrodes using metal tungsten, characterized in that: include: Depositing an oxide layer, planarizing, exposing and developing, and dry etching are sequentially performed on the substrate to form interdigital grooves; Chemically vapor depositing metal tungsten in the interdigital grooves to form interdigital electrodes with a PST structure and then planarizing the electrodes; Each interdigital electrode with a PST structure includes an IDT body and a PST structure. The PST structure is disposed at both ends of the IDT body and forms an I-shape together with the PST structures at both ends.

2. The method according to claim 1, characterized in that After the interdigital grooves are formed, at least one of metal titanium, tantalum and titanium nitride is also used for sputtering; The titanium nitride formed by sputtering the metal titanium is used to assist adhesion and also serves as a barrier layer for the metal tungsten.

3. The method according to claim 1, characterized in that Chemical vapor deposition of tungsten metal includes: First, a thin layer of tungsten is formed as a nucleation layer by using a silane reduction reaction of tungsten, and then a tungsten body is deposited by using a hydrogen reduction reaction of tungsten; The thickness of the thin layer of tungsten is 30-100 nm.

4. The method according to claim 3, characterized in that The chemical equation for the silane reduction reaction of tungsten is: 2WF6(gas)+3SiH4(gas)------->2W(solid)+3SiF4(gas)+6H2(gas); The chemical equation for the hydrogen reduction reaction of tungsten is: WF6(gas)+3H2(gas)------->W(solid)+6HF(gas).

5. The method according to claim 3, characterized in that: The silane reduction reaction of tungsten is used to ensure stable agglomeration of tungsten and dense filling without voids and gaps; The hydrogen reduction reaction of tungsten is used to ensure that tungsten has better step coverage ability and prevent premature sealing of embolism caused by local excessive deposition of tungsten body.

6. The method according to claim 1, characterized in that The process used for planarization is chemical mechanical polishing; After forming the interdigital electrode with the PST structure, the surface of the oxide layer deposited on the substrate is flattened; The planarization stops at the surface of the oxide layer deposited on the substrate and is used as an auxiliary temperature compensation film layer to ensure that there is no influence on the uniformity of the subsequent temperature compensation film layer process.

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 interdigitated grooves, exposing and developing is a positive photoresist.

8. A device using metal tungsten to manufacture a SAW filter PST structure and interdigital electrodes, characterized in that: include: A substrate having an oxide layer covered on one surface; The interdigitated electrode with a PST structure is in an interdigitated shape and is formed by chemical vapor deposition of metal tungsten. The interdigitated electrodes of each interdigitated electrode with a PST structure include an IDT body and a PST structure. Both ends of the IDT body are provided with PST structures, and together with the PST structures at both ends, an I-shape is formed. The interdigitated electrode with a PST structure is located in the oxide layer, and one side surface thereof is in contact with one side surface of the substrate.

9. The device according to claim 8, characterized in that One side surface of the interdigital electrode with the PST structure contacts one side surface of the substrate through a metal tungsten barrier layer.

10. The device according to claim 8, characterized in that The chemical vapor deposition of metal tungsten first uses a silane reduction reaction of tungsten to form a thin layer of tungsten as a nucleation layer, and then uses a hydrogen reduction reaction of tungsten to deposit the tungsten body to ensure that a dense tungsten plug is obtained.

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