CN112564661A

CN112564661A - Method for improving interface bonding strength of surface acoustic wave filter film layer

Info

Publication number: CN112564661A
Application number: CN202011412000.4A
Authority: CN
Inventors: 翁志坤; 许欣; 宋晓辉
Original assignee: Guangdong Guangnaixin Technology Co ltd
Current assignee: Guangdong Guangnaixin Technology Co ltd
Priority date: 2020-12-03
Filing date: 2020-12-03
Publication date: 2021-03-26

Abstract

The invention discloses a method for improving the interface bonding strength of a surface acoustic wave filter film layer. Specifically, the invention describes a method for improving the interface bonding strength of a surface acoustic wave filter membrane layer, which comprises the following steps: performing laser micro-hole treatment on the surface of a piezoelectric material substrate to form a series of blind holes on the surface of the piezoelectric material substrate; and plating metal electrodes on the surface of the piezoelectric material substrate subjected to laser micro-hole treatment.

Description

Method for improving interface bonding strength of surface acoustic wave filter film layer

Technical Field

The technical scheme of the invention can be used for preparing the filter of wireless communication equipment such as mobile phones, base stations and the like, and further can be used for the application of independent and integrated modules of radio frequency transceiving front ends of mobile phones, wireless base stations and the like. In particular, the invention relates to a method for improving the interface bonding strength of a surface acoustic wave filter membrane layer.

Background

Surface acoustic wave filters (SAW), bulk acoustic wave filters (BAW) and thin film bulk acoustic wave Filters (FBAR) are three major mainstream technologies in the field of current filters. Among them, the SAW filter is mainly used for low frequency band and middle frequency band, and the requirement for power durability of the SAW filter is higher and higher.

A general technical solution for fabricating an interdigital transducer (IDT) electrode of a SAW filter is: in LiNbO₃Or LiTaO₃A Ti metal film is evaporated on the surface of the wafer to be used as a priming layer, and a Cu or Al metal film is further plated on the Ti metal film, so that a metal electrode with certain resistivity can be obtained. However, in the IDT electrode of the SAW filter applied to surface acoustic waves of several tens of GHZ, the IDT electrode thin film may be detached due to stress by the alternating repetitive stress of the high-frequency acoustic waves. Particularly, for the interface between the nonmetal and the metal film layer between the piezoelectric material substrate and the metal underlayer (such as Ti metal film) of the IDT electrode, the interface bonding strength is insufficient, so that the film is easy to fall off, and the electrode is easy to fail. Therefore, it is desirable to improve the film interface bonding strength as compared to conventional IDT electrodes.

In the conventional technique for improving the interfacial bonding strength of the film layer, a bonding layer is generally formed on the piezoelectric material substrate (between the piezoelectric material substrate and the supporting substrate) to form a bonded body between the piezoelectric material substrate and the supporting substrate, thereby enhancing the interfacial bonding strength of the film layer. For example, the bonding layer and the support substrate are irradiated with a neutral beam to activate the surfaces of the bonding layer and the support substrate, thereby roughening the bonding interface and increasing the bonding strength between the bonding layer and the piezoelectric substrate and between the bonding layer and the support substrate, thereby forming a bonded body of the piezoelectric material substrate and the electrode. However, this method has limited improvement in interfacial bond strength of the film layer; a special bonding layer needs to be manufactured on the piezoelectric substrate, so that the manufacturing process is complicated; in addition, the increased non-metallic layer also adversely affects the conductivity of the overall electrode.

Further, similarly, in the fabrication of a temperature compensation type surface acoustic wave filter (TC-SAW), it is necessary to plate a SiO layer on the surface of a surface layer metal film (such as a Cu or Al metal film) of a metal electrode₂And the temperature compensation layer is used for forming an IDT electrode structure with certain temperature compensation characteristics. Thus, nonmetallic SiO may also occur in the case of high-frequency sound waves₂Interface between temperature compensation layer and metal electrode surface layer metal film (non-metal as described above)Interface with metal film) and the film falls off.

Disclosure of Invention

The invention provides a method for improving the interface bonding strength of a surface acoustic wave filter membrane layer, which comprises the following steps: performing laser micro-hole treatment on the surface of a piezoelectric material substrate to form a series of blind holes on the surface of the piezoelectric material substrate; and plating metal electrodes on the surface of the piezoelectric material substrate subjected to laser micro-hole treatment. Further, the depth and the aperture of a series of blind holes formed in the surface of the piezoelectric material substrate are determined based on the thickness of the underlying metal film of the metal electrode.

In another aspect, the method of the present invention further comprises: performing the laser micro-hole treatment on the surface of the surface layer metal film of the metal electrode to form a series of blind holes on the surface of the surface layer metal film; and plating a temperature compensation layer on the surface of the surface layer metal film subjected to laser micro-hole treatment. Further, the depth and the aperture of a series of blind holes formed on the surface of the surface layer metal film are determined based on the thickness of the temperature compensation layer.

As an example, the series of blind holes formed are spindle shaped. As an example, the depth of the series of blind holes is in the range of 100-200 nm. As an example, the hole pitch of the series of blind holes is in the range of 300-500 nm. As an example, the laser for the laser microporation treatment has a wavelength of 193nm and a laser pulse width of 10^-12s, laser single pulse energy of 0.1-0.5J/cm²。

According to the invention, the laser micropore treatment is carried out on the surface of the piezoelectric material substrate, and a series of blind holes are formed on the surface of the piezoelectric material substrate, so that the metal film can be effectively pinned on the surface of the piezoelectric material substrate during subsequent metal film plating. Therefore, the invention can maintain good interface strength and high power durability between the piezoelectric material substrate and the metal electrode under the condition of ensuring that the structural components of the IDT electrode in the SAW are not changed.

In addition, for TC-SAW IDT electrode surface layer metal film and SiO₂Film layer boundary between temperature compensation layersSurface, similarly performing laser micro-hole treatment on the surface of the surface layer metal film to form a series of blind holes on the surface of the surface layer metal film, thereby enabling the subsequent SiO plating₂Film formation of the SiO₂The film can be effectively pinned on the surface of the surface metal film. Therefore, the invention can ensure good interface strength and high power durability between the metal electrode and the temperature compensation layer in the TC-SAW filter.

Drawings

To provide a more complete understanding of the present invention and the features and advantages thereof, reference is made to the following description, taken in conjunction with the accompanying drawings, wherein like or corresponding reference numerals designate like or corresponding parts, in which:

FIG. 1 illustrates a process for enhancing SAW filter film layer interface bond strength in accordance with an embodiment of the present invention;

FIG. 2 illustrates another process for enhancing SAW filter film layer interface bond strength in accordance with embodiments of the present invention;

FIG. 3 illustrates a schematic diagram of a laser microporation process according to an embodiment of the present invention.

Detailed Description

The invention provides a method for improving the interface bonding strength of a film layer of an SAW filter. In particular, the technical scheme described in the text can enhance the bonding strength of the film layer interface between the SAW filter piezoelectric material substrate and the metal electrode and between the metal electrode and the SiO2 temperature compensation layer.

Referring now to fig. 1, fig. 1 schematically illustrates a process for enhancing film layer interfacial bond strength between a SAW filter piezoelectric material substrate and a metal electrode, in accordance with an embodiment of the present invention. As shown in fig. 1, the process specifically includes: performing laser micro-hole treatment on the surface of a piezoelectric material substrate 102 to form a series of uniformly distributed and dense blind holes 104 with a certain shape on the surface of the piezoelectric material substrate, namely step A1; then, plating metal electrodes on the surface of the piezoelectric material substrate subjected to laser micro-hole treatment, specifically: a metal film 106 (for example, a Ti metal film) is embedded as a primer layer on the surface of the piezoelectric material substrate subjected to the laser micro-porous treatment, step a2, and then a Cu or Al metal film 108 is plated on the primer metal film 106, step A3, thereby obtaining a metal electrode having a certain resistivity. Further, in order to effectively pin the underlying metal film 106 on the surface of the piezoelectric material substrate 102 when plating the metal electrode, the depth, the hole pitch and the hole diameter of the series of blind holes 104 formed on the surface of the piezoelectric material substrate 102 may be determined according to the thickness of the plated underlying metal film 106; the morphology of the series of blind vias 104 formed is selected according to the actual pinning effect on the underlying metal film 106. By way of non-limiting example, the series of blind holes 104 formed may be designed as specially configured blind holes having an opening diameter smaller than the intermediate waist diameter, for example, preferably, as spindle-shaped blind holes. As a non-limiting example, the depth of the series of blind holes 104 formed may be designed to be in the range of 100 to 200nm, and the hole pitch may be designed to be in the range of 300 to 500 nm.

For the TC-SAW filter, after the metal electrode is plated on the surface of the piezoelectric material substrate, that is, after step a3 in fig. 1 is completed, it is necessary to plate SiO on the surface of the surface layer metal film 108 (such as Cu or Al film)₂A temperature compensation layer. Aiming at the surface metal film and SiO₂And (3) similarly carrying out laser micro-hole treatment on the surface of the surface layer metal film at the film layer interface between the temperature compensation layers, and forming a series of blind holes on the surface of the surface layer metal film. Turning specifically to fig. 2, another process for enhancing film layer interfacial bond strength between a metal electrode and a temperature compensation layer according to an embodiment of the present invention is shown. As shown in fig. 2, the process specifically includes: performing laser micro-hole treatment on the surface of the metal electrode surface layer metal film 108 to form a series of uniformly distributed and dense blind holes 204 with a certain shape on the surface of the surface layer metal film, namely step B1; subsequently, SiO₂The film 206 is embedded in the surface of the laser microvoided top metal film, step B2. Similarly, further, to make SiO plating₂Temperature compensation layer of SiO₂The film 206 is capable of being effectively pinned to the surface of the top metal film 108 of the metal electrode, which may be in accordance with the SiO deposited₂Thickness of film 206, surface of metal film 108 determined on surface layerThe depth, spacing and aperture of the series of blind holes 204 formed by the face; according to the actual pair of SiO₂The pinning effect of the film 206 selects the morphology of the series of blind holes 204 formed. By way of non-limiting example, the series of blind holes 104 formed may be designed as specially configured blind holes having an opening diameter smaller than the diameter of the intermediate waist, for example, preferably, as spindle-shaped blind holes. As a non-limiting example, the depth of the series of blind holes 204 formed may be designed to be in the range of 100 to 200nm, and the hole pitch may be designed to be in the range of 300 to 500 nm.

Turning now to fig. 3, a schematic diagram of laser micro-via processing of a SAW filter film layer surface is illustrated, in accordance with an embodiment of the present invention. As shown in fig. 3, a surface of a SAW filter film layer 304 (i.e., for example, the surface of the piezoelectric material substrate 102 in fig. 1 or the surface of the metal electrode surface layer metal film 108 in fig. 2) is irradiated with, for example, an ultraviolet excimer picosecond laser emission laser beam 302 with a vibrating mirror. During the interaction of the laser spot with the surface of the film 304, the material at the surface of the film 304 melts (as shown at 306 in fig. 3) and then vaporizes (as shown at 308 in fig. 3), and the resulting material vapor causes a surface pressure (as shown at 310 in fig. 3) on the surface of the film 304 that acts on the non-vaporized molten material, which back pressure can expel the melted material (as shown at 312 in fig. 3). When the melted material is removed, the unmelted material at the bottom of the blind hole formed continues to interact with the laser. And so on, thereby enabling the blind hole depth to be continuously increased. Thus, by controlling parameters such as the power, frequency, energy of a single laser pulse, and time of drilling action of laser drilling used for laser micro-drilling, the depth, aperture, hole pitch, and morphology of a series of blind holes to be formed can be controlled. As a non-limiting example, the laser used for laser microvoiding was 193nm wavelength with a pulse width of 10^-12s, single pulse energy 0.1-0.5J/cm²。

Claims

1. A method for improving interfacial bond strength of a membrane layer of a surface acoustic wave filter, the method comprising:

performing laser micro-hole treatment on the surface of a piezoelectric material substrate to form a series of blind holes on the surface of the piezoelectric material substrate; and

and plating metal electrodes on the surface of the piezoelectric material substrate subjected to laser micro-porous treatment.

2. The method of claim 1, wherein the depth and aperture of the series of blind holes formed in the surface of the piezoelectric material substrate are determined based on the thickness of an underlying metal film of the metal electrode.

3. The method of claim 1, the method further comprising:

performing the laser micro-hole treatment on the surface of the surface layer metal film of the metal electrode to form a series of blind holes on the surface of the surface layer metal film; and

and plating a temperature compensation layer on the surface of the surface layer metal film subjected to laser micro-porous treatment.

4. The method of claim 3, wherein the depth and aperture of the series of blind holes formed in the surface of the top metal film are determined based on the thickness of the temperature compensation layer.

5. The method of any one of claims 1-4, wherein the series of blind holes formed are spindle shaped.

6. The method of any one of claims 1-4, wherein the series of blind holes formed have a depth in the range of 100-200 nm.

7. The method of any one of claims 1-4, wherein the series of blind holes formed have a hole pitch in the range of 300-500 nm.

8. The method of any of claims 1-4, wherein the laser microporation is performed using a laser wavelength of 193nm and a laser pulse width of 10^-12s, laser single pulse energy of 0.1-0.5J/cm²。