CN115395912A - Surface acoustic wave filter and method for manufacturing same - Google Patents

Surface acoustic wave filter and method for manufacturing same Download PDF

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Publication number
CN115395912A
CN115395912A CN202111256436.3A CN202111256436A CN115395912A CN 115395912 A CN115395912 A CN 115395912A CN 202111256436 A CN202111256436 A CN 202111256436A CN 115395912 A CN115395912 A CN 115395912A
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China
Prior art keywords
metal
layer
metal layer
acoustic wave
surface acoustic
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Pending
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CN202111256436.3A
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Chinese (zh)
Inventor
朱庆芳
林科闯
罗捷
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Quanzhou San'an Integrated Circuit Co ltd
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Xiamen Sanan Integrated Circuit Co Ltd
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Priority to CN202111256436.3A priority Critical patent/CN115395912A/en
Publication of CN115395912A publication Critical patent/CN115395912A/en
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    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03HIMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H3/00Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/08Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of resonators or networks using surface acoustic waves
    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03HIMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46Filters
    • H03H9/64Filters using surface acoustic waves

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

Abstract

The invention discloses a surface acoustic wave filter and a manufacturing method thereof.A light-tight metal layer is covered on a lithium tantalate or lithium niobate substrate at first, then IDT patterns are defined by utilizing a yellow light process, then metal is deposited, photoresist and the metal above the photoresist are removed by adopting a stripping process, and then the redundant light-tight metal layer is removed. When the light-tight metal layer is an adhesive layer, depositing metal through an evaporation process, and removing the adhesive layer by using an RIE (reactive ion etching) or ICP (inductively coupled plasma) process; when the opaque metal layer is used as the seed layer, the electroplating process is adopted to deposit metal, and then the wet etching process is utilized to remove the seed layer. The manufacturing process of the interdigital metal electrode can be completed. The invention can avoid the influence on the photoetching result caused by different light transmittance due to uneven blackening of the substrate, and can avoid the problems of metal residue and the like.

Description

Surface acoustic wave filter and method for manufacturing same
Technical Field
The invention relates to the field of filters, in particular to a surface acoustic wave filter and a manufacturing method thereof.
Background
The surface acoustic wave filter has the advantages of light weight, small volume, high reliability, good consistency, flexible design, capability of being manufactured by adopting a microelectronic processing technology, suitability for batch production and the like, and is widely applied to the fields of mobile communication, radio and television, nondestructive testing, identification and positioning, navigation, telemetering and the like. The working principle of the surface acoustic wave filter is that an electric signal is transmitted to interdigital metal electrodes (IDTs), the electric signal is converted into an acoustic wave signal through the piezoelectric effect of a piezoelectric substrate, then the acoustic wave is processed, and then the acoustic wave signal is converted into the electric signal through the IDTs to be transmitted in the next step, so that the surface acoustic wave filter is provided with the IDTs which are oppositely arranged and have crossed combs.
The interdigital metal electrode is used as a key part in the manufacturing process of the surface acoustic wave filter and is mainly manufactured by a lift-off process and a dry etching process, the two processes have advantages and disadvantages, and the lift-off process is easily influenced by the non-uniform light transmittance of a substrate to cause the stability of a Critical Dimension (CD). In the dry etching process, which is generally a conventional aluminum etching process, the yellow light resolution is reduced in the yellow light process due to the high reflectivity of aluminum.
Conventional substrate lithium tantalate (LiTaO) 3 ) Or lithium niobate (LitnbO) 3 ) The manufacturing process has a blackening step, which is a reduction method, can reduce the resistance value of the substrate, avoid electrostatic effect and reduce the fragment rate, but the derived problem is that the wafer is easy to generate uneven blackening, so that the light transmittance is different, and the problem of further influencing the photoetching process window of a lift-off process in the manufacturing process of the interdigital metal electrode (IDT) is solved.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a surface acoustic wave filter and a manufacturing method thereof.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
a method for manufacturing a surface acoustic wave filter is characterized by comprising the following steps:
1) Providing a piezoelectric material substrate;
2) Depositing an opaque metal layer on the substrate;
3) Coating photoresist on the light-tight metal layer, exposing and developing to define an IDT pattern;
4) Depositing metal, stripping the photoresist and the metal above the photoresist to form an IDT metal layer corresponding to the IDT pattern, and exposing the opaque metal layer below the photoresist;
5) And removing the exposed opaque metal layer.
In an optional embodiment, the opaque metal layer is an adhesion layer, the adhesion layer is Ti or TiW, and the adhesion layer is manufactured by a sputtering or evaporation process in the step 2.
In an alternative embodiment, in step 4, a metal is deposited on the photoresist defining the IDT pattern and the exposed region of the adhesion layer by using an evaporation process, and the metal is aluminum or an aluminum copper alloy.
In an alternative embodiment, in the step 5, the RIE or ICP process is used to remove the exposed adhesive layer, and a solvent cleaning is used to remove the etching products and expose the substrate.
In an alternative embodiment, SF is used in the RIE process 6 And He at a pressure of 200 to 500mTorr.
In an optional embodiment, the opaque metal layer is a seed layer, the seed layer is Ti/Cu or TiW/Au, and the seed layer is manufactured by a sputtering process in the step 2.
In an optional embodiment, in the step 4, a plating process is adopted to deposit metal on the photoresist defining the IDT pattern and the exposed area of the seed layer, and when the seed layer is Ti/Cu, the metal is Cu; when the seed layer is TiW/Au, the metal is Au.
In an optional embodiment, in the step 5, a wet etching process is adopted to remove the exposed seed layer, and a solvent is adopted to clean and remove an etching product and expose the substrate.
In an alternative embodiment, the opaque metal layer has a thickness of 10nm to 200nm.
The surface acoustic wave filter manufactured by the manufacturing method comprises a piezoelectric material substrate, and an opaque metal layer and an IDT metal layer which are arranged on the substrate in a laminated mode, wherein a plurality of grooves which are corresponding to IDT graphs and expose out of the substrate are formed in the opaque metal layer and the IDT metal layer.
Compared with the prior art, the invention has the following beneficial effects:
(1) Because the piezoelectric material substrate is an uneven light-transmitting material, the light-tight metal layer is coated on the substrate before the yellow light process is carried out, and the consistency of the light transmittance of the substrate can be ensured.
(2) The opaque metal layer is Ti/Cu or TiW/Au, which is beneficial to depositing the IDT metal layer on the substrate in various modes such as vapor deposition or electroplating, and the corresponding IDT metal layer is aluminum, aluminum copper alloy or Cu and gold, so that the adhesiveness between the IDT metal layer and the substrate can be further improved, and the stability of the device is improved.
(3) The stripping process is improved, so that the problem of a process window in a yellow light manufacturing process caused by uneven blackening of the substrate is avoided, the influence on a photoetching result is further reduced, metal residue is avoided, and the stability of the CD is improved.
Drawings
Fig. 1 is a process flow diagram of a first embodiment and a second embodiment of the present invention, wherein fig. 1a to 1f are schematic structural diagrams obtained in each step, respectively.
Detailed Description
The invention is further explained below with reference to the figures and the specific embodiments. The drawings are only schematic and can be easily understood, and the specific proportion can be adjusted according to design requirements. The definitions of the top and bottom relationships of the relative elements and the front and back sides of the figures described herein are understood by those skilled in the art to refer to the relative positions of the components and thus all of the components may be flipped to present the same components and still fall within the scope of the present disclosure.
The present invention will be described in detail with reference to a process flow chart of a method for manufacturing a surface acoustic wave filter of the present invention shown in fig. 1.
Example one
Referring to fig. 1a, a piezoelectric material substrate 1 is provided, the piezoelectric material substrate 1 may be, for example, lithium tantalate or a lithium tantalate wafer, and the thickness of the substrate 1 is 150 to 350um, for example, 200um.
Referring to fig. 1b, an opaque metal layer 2 is deposited on the substrate 1, the opaque metal layer 2 is an adhesion layer, and a sputtering or evaporation method is used to cover the substrate 1 with an adhesion layer made of Ti or TiW and having a thickness of 10-200 nm. For example, it may be 100nm.
Referring to fig. 1c, photoresist is coated on the adhesive layer, IDT patterns are defined through exposure and development, and the adhesive layer between the IDT patterns is exposed, wherein the electrode line width of the IDT patterns can be defined according to the actual product requirement, and ranges from 200nm to 500nm, for example, 250nm.
Referring to fig. 1d, aluminum or aluminum-copper alloy is deposited on the structure, and the aluminum or aluminum-copper alloy may be deposited by evaporation. Specifically, the aluminum-copper alloy may be an aluminum-copper alloy containing 0.5 to 5% of copper, and the thickness of aluminum or the aluminum-copper alloy may be 50 to 1000nm, for example, 500nm.
Referring to fig. 1e, the remaining photoresist and the metal Cu thereon are stripped using a stripping process to form an IDT metal layer 4 corresponding to the IDT pattern. The lift-off process uses a solvent such as NMP to remove excess photoresist and metal Cu and expose the adhesive layer in the area under the photoresist.
Referring to fig. 1f, the exposed adhesive layer is etched by RIE or ICP, etc., and the exposed adhesive layer is etched clean, leaving the adhesive layer under the IDT metal layer 4. Specifically, the bonding layer is etched by introducing SF into the plasma etcher in a low-directivity mode 6 And He at a pressure of 200 to 500mTorr. The etching product is then cleaned with a solvent such as EKC-830, and the pattern of the IDT metal layer 4 is finally obtained.
Example two
Referring to fig. 1a, a piezoelectric material substrate 1 is provided, the piezoelectric material substrate 1 may be, for example, lithium tantalate or a lithium tantalate wafer, and the thickness of the substrate 1 is 150 to 350um, for example, 200um.
Referring to fig. 1b, an opaque metal layer 2 is deposited on the substrate 1, the opaque metal layer 2 is a seed layer, and a sputtering method is used to cover the seed layer on the substrate 1, wherein the seed layer can be Ti/Cu or TiW/Au, and the thickness of the seed layer is 10-200 nm. For example, it may be 100nm.
Referring to fig. 1c, photoresist is coated on the seed layer, IDT patterns are defined by exposure and development, and the seed layer between the IDT patterns is exposed, and the electrode line width of the IDT patterns can be defined according to the actual product requirement, and can range from 200nm to 500nm, for example, 250nm.
Referring to fig. 1d, depositing metal on the above structure, and depositing metal in an electroplating manner, where the seed layer is Ti/Cu, and the metal is Cu; when the seed layer is TiW/Au, the metal is Au, and the thickness of the metal is 50-1000 nm, or 500nm.
Referring to fig. 1e, the remaining photoresist and the metal above it are stripped using a stripping process to form an IDT metal layer 4 corresponding to the IDT pattern. The stripping process adopts solvents such as DMSO (dimethyl sulfoxide) to remove redundant photoresist and metal, and exposes the seed layer in the area below the photoresist.
Referring to fig. 1f, the exposed seed layer is removed by wet etching, the exposed seed layer is etched clean, the seed layer below the IDT metal layer 4 is remained, and a solution adopted by the wet etching is CHEMLEADER Cu-128 and ti-890. Finally, the pattern of the IDT metal layer 4 is obtained.
The surface acoustic wave filter manufactured by the two manufacturing methods comprises a piezoelectric material substrate 1, and an opaque metal layer 2 and an IDT metal layer 3 which are arranged on the substrate 1 in a laminated mode, wherein a plurality of grooves corresponding to IDT graphs and exposing the substrate 1 are formed in the opaque metal layer 2 and the IDT metal layer 3. The opaque metal layer 2 may be an adhesive layer made of Ti or TiW, and the corresponding IDT metal layer 3 is aluminum or an aluminum-copper alloy. The opaque metal layer 2 can be made of a seed layer of Ti/Cu or TiW/Au, and when the seed layer is Ti/Cu, the IDT metal layer 3 is Cu; when the seed layer is TiW/Au, the IDT metal layer 3 is Au. The invention can select proper deposition mode and etching mode according to specific materials to manufacture the surface acoustic wave filter with good adhesiveness and high CD stability.
The embodiment of the application adopts the improved stripping process to manufacture the IDT metal layer, so that the problem of high light transmittance of the substrate or aluminum can be avoided. The process can avoid the problem of uneven light transmittance of the substrate, so that the common metal residue (metal doping) problem of the stripping process can be avoided, the special photoresist removing process of the aluminum etching process is not needed, the problem similar to aluminum corrosion (Al corrosion) can be avoided, the common local unevenness (microloading) problem of the aluminum etching can be avoided, and in addition, the high reflectivity of aluminum is avoided, so that the process window (process window) of yellow light can be improved.
The above embodiments are only used to further illustrate the surface acoustic wave filter and the manufacturing method thereof of the present invention, but the present invention is not limited to the embodiments, and any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention fall within the protection scope of the technical solution of the present invention.

Claims (10)

1. A method for manufacturing a surface acoustic wave filter is characterized by comprising the following steps:
1) Providing a piezoelectric material substrate;
2) Depositing an opaque metal layer on the substrate;
3) Coating photoresist on the light-tight metal layer, exposing and developing to define an IDT pattern;
4) Depositing metal, stripping the photoresist and the metal above the photoresist to form an IDT metal layer corresponding to the IDT pattern, and exposing the opaque metal layer below the photoresist;
5) And removing the exposed opaque metal layer.
2. A method for making a surface acoustic wave filter as claimed in claim 1, wherein said opaque metal layer is an adhesive layer, said adhesive layer is Ti or TiW, and said adhesive layer is made by a sputtering or evaporation process in said step 2.
3. A method for making a surface acoustic wave filter as set forth in claim 2, wherein a metal is deposited on the exposed areas of the photoresist defining the IDT pattern and the adhesive layer in said step 4 by an evaporation process, said metal being aluminum or an aluminum-copper alloy.
4. A method for manufacturing a surface acoustic wave filter as set forth in claim 2, wherein said step 5 is a step of removing said adhesive layer exposed by RIE or ICP, and a step of removing etching products by solvent cleaning and exposing said substrate.
5. A method for manufacturing a surface acoustic wave filter as set forth in claim 4, wherein SF is used in said RIE process 6 And He at a pressure of 200 to 500mTorr.
6. The method of manufacturing a surface acoustic wave filter as claimed in claim 1, wherein said opaque metal layer is a seed layer, said seed layer is Ti/Cu or TiW/Au, and said seed layer is manufactured by a sputtering process in said step 2.
7. The method of manufacturing a surface acoustic wave filter according to claim 5, wherein in said step 4, a metal is deposited on the exposed areas of the seed layer and the photoresist defining the IDT pattern by using an electroplating process, and when the seed layer is Ti/Cu, the metal is Cu; when the seed layer is TiW/Au, the metal is Au.
8. A method for manufacturing a surface acoustic wave filter as set forth in claim 5, wherein said step 5 is a wet etching process for removing the exposed seed layer, and a solvent cleaning process for removing the etching products and exposing the substrate.
9. A method for manufacturing a surface acoustic wave filter as claimed in any one of claims 1 to 8, wherein said opaque metal layer has a thickness of 10nm to 200nm.
10. A surface acoustic wave filter manufactured by the manufacturing method of any one of claims 1 to 9, comprising a piezoelectric material substrate, and an opaque metal layer and an IDT metal layer laminated on the substrate, wherein the opaque metal layer and the IDT metal layer have a plurality of grooves corresponding to the IDT pattern and exposing the substrate.
CN202111256436.3A 2021-10-27 2021-10-27 Surface acoustic wave filter and method for manufacturing same Pending CN115395912A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202111256436.3A CN115395912A (en) 2021-10-27 2021-10-27 Surface acoustic wave filter and method for manufacturing same

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202111256436.3A CN115395912A (en) 2021-10-27 2021-10-27 Surface acoustic wave filter and method for manufacturing same

Publications (1)

Publication Number Publication Date
CN115395912A true CN115395912A (en) 2022-11-25

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Family Applications (1)

Application Number Title Priority Date Filing Date
CN202111256436.3A Pending CN115395912A (en) 2021-10-27 2021-10-27 Surface acoustic wave filter and method for manufacturing same

Country Status (1)

Country Link
CN (1) CN115395912A (en)

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