WO2006126382A1

WO2006126382A1 - Piezoelectric device

Info

Publication number: WO2006126382A1
Application number: PCT/JP2006/309245
Authority: WO
Inventors: Hayami Kudo; Hajime Yamada
Original assignee: Murata Manufacturing Co., Ltd.
Priority date: 2005-05-24
Filing date: 2006-05-08
Publication date: 2006-11-30

Abstract

A piezoelectric device which can be efficiently manufactured. A cover substrate (20) is bonded along the periphery of an element substrate (12) whereupon a piezoelectric element is formed, and the piezoelectric element is sealed. The main plane of the cover substrate (20) is provided with an external terminal (26) having solder as the main component, and an outermost layer (25) made of resin to cover portions other than the external terminal (26). A first assembled substrate to be the element substrate (12) of a plurality of piezoelectric devices (10) and a second assembled substrate to be the cover substrate (20) of the piezoelectric devices (10) are bonded so that each element substrate (12) and each cover substrate (20) are bonded, and then the bonded assembled substrates are cut along a cutting line into independent piezoelectric devices (10). On the second assembled substrate before cutting, a resin layer to be an outermost layer (25) is formed on the plane opposite to the plane whereupon the first assembled substrate is to be bonded. On the resin layer, a cutting section having no resin is formed along the cutting line before the second assembled substrate is cut.

Description

Specification

Piezoelectric device

Technical field

TECHNICAL FIELD [0001] The present invention relates to a piezoelectric device, and more particularly, to a reduction in thickness of a piezoelectric device including a piezoelectric element using a piezoelectric film such as a resonator or a filter.

Background art

In recent years, in order to reduce the size of piezoelectric devices such as surface acoustic wave filters (SAW filters) and Balta surface acoustic wave filters (BAW filters), development of chip size packages (CSPs) that reduce the size of packages to the element chip size has been developed. It is advanced.

[0003] A plurality of CSP piezoelectric devices are simultaneously fabricated in a wafer state, and then cut into individual piezoelectric devices. When cutting, it is necessary to avoid various problems such as the occurrence of damage such as wafer cracks and deterioration of hermetic sealing.

[0004] For example, Patent Document 1 proposes making a cut into the sealing resin in order to reduce warpage caused by the shrinkage of the sealing resin formed on the wafer.

[0005] Also, in Patent Documents 2 and 3, a photosensitive resin is applied to a wafer and an opening or a groove is formed in the photosensitive resin to expose the wafer boundary. Cutting only along the boundary. Patent Document 2 discloses a configuration in which a wafer is bonded to seal an element portion, and an opening is provided in the resin between the wafers. Patent Document 3 discloses a configuration in which grooves are formed in the sealing resin in a configuration in which the wafer on which the element portion is formed is covered with the sealing resin.

Patent Document 1: Japanese Patent Laid-Open No. 2003-218144

Patent Document 2: Japanese Patent Application Laid-Open No. 2004-129222

Patent Document 3: Japanese Patent Laid-Open No. 2004-79928

Disclosure of the invention

Problems to be solved by the invention

[0006] In Patent Documents 1 to 3, a resin is formed so as to be in contact with a wafer on which an element is formed. As in Patent Document 1, the sealing resin is diced in all directions along the sealing resin thickness by dicing. If this is included, damage to the wafer is unavoidable, and the sealing performance at the interface between the wafer and the sealing resin decreases. In addition, since defects are likely to occur due to the influence of warpage after the formation of the grease, it is not possible to form solder external terminals in the next step. Or, the yield decreases.

[0007] If the substrate and the resin are cut at the same time, the blade is clogged by the resin and the work efficiency is lowered.

[0008] The present invention is intended to provide a piezoelectric device that can be efficiently produced in view of the strong situation.

Means for solving the problem

In order to solve the above-described problems, the present invention provides a piezoelectric device configured as follows.

[0010] The piezoelectric device includes: a) an element substrate on which a piezoelectric element is formed; b) a lid substrate that is bonded along the periphery of the element substrate and seals the piezoelectric element; and c) the lid substrate. An external terminal mainly composed of solder disposed on the main surface opposite to the element substrate; d) on the main surface opposite to the element substrate of the lid substrate; And an outermost layer made of a resin covering the portion other than the external terminals. A first assembly substrate that is the element substrate of a plurality of piezoelectric devices and a second assembly substrate that is the lid substrate of a plurality of piezoelectric devices are bonded to each other. After being bonded to each other, they are cut along a cutting line and separated into individual piezoelectric devices. The second aggregate substrate before being cut is formed with a resin layer as the outermost layer on the surface opposite to the surface to which the first aggregate substrate is bonded. Before the second aggregate substrate is cut, the resin layer should be free of grease along the cutting line! A ridge cut portion is formed.

[0011] According to the above configuration, since the notched portion is formed in the resin layer, it is possible to prevent the substrate from being warped by the resin layer. As a result, the influence of warpage can be reduced and the yield can be improved.

[0012] In addition, since the piezoelectric element is sealed by bonding the substrates, sealing reliability is higher than when sealing with a grease in contact with the substrates.

[0013] Further, since the notched portion is formed along the cutting line in the resin layer, The collective substrate can be cut immediately or barely touched. Therefore, the blade used for cutting can be prevented from being clogged by the resin layer, and the working efficiency can be improved.

[0014] Preferably, the resin layer forming the outermost layer is formed by applying a paste resin and then curing.

[0015] According to the above configuration, the outermost layer can be brought into close contact with the lid substrate even if the lid substrate has irregularities.

[0016] Preferably, the resin layer forming the outermost layer is formed by bonding a film material.

[0017] According to the above configuration, the stress acting on the lid substrate can be weakened and the warpage can be reduced as compared with the case where paste-like resin is used for the outermost layer. In addition, it is easy to make the thickness of the outermost layer uniform.

[0018] Preferably, the pasty resin is a photosensitive resin.

[0019] According to the configuration described above, it is possible to form a cut portion free of grease in the resin layer without damaging the substrate by using a photolithography technique.

[0020] Preferably, the film material is a photosensitive film.

[0021] According to the configuration described above, it is possible to form the notched portion without the resin in the resin layer without damaging the substrate by using the photolithography technique.

[0022] Preferably, the cut portion formed in the resin layer has a substantially lattice shape.

[0023] According to the above configuration, the vertical and horizontal warpage can be alleviated by the lattice-shaped cut portions.

[0024] Preferably, the cut portion formed in the resin layer generally follows the outer shape of the piezoelectric device.

[0025] According to the above configuration, warpage can be reduced by minimizing the interval between the notch portions so that the outer shape of the adjacent piezoelectric device is simultaneously formed from one notch portion.

[0026] Preferably, a width of the cut portion formed in the resin layer is equal to or larger than a width of a dicing blade used when cutting the second aggregate substrate. [0027] According to the above configuration, it is possible to cut the aggregate substrate from which the resin layer is hardly or completely touched from the cut portion of the resin layer.

[0028] Preferably, a through-hole penetrating the resin layer in the thickness direction is formed in the resin layer simultaneously with the formation of the cut portion.

[0029] According to the above configuration, the number of steps can be reduced, and in particular, the number of steps affected by warpage can be reduced.

The invention's effect

[0030] The piezoelectric device of the present invention can be produced efficiently.

Brief Description of Drawings

FIG. 1 is a cross-sectional view of a piezoelectric device. (Example)

FIG. 2 is an explanatory diagram of a manufacturing process. (Example)

FIG. 3 is a cross-sectional view of a cut portion. (Example)

FIG. 4 is a cross-sectional view of a cut portion. (Comparative example)

Explanation of symbols

10 Piezoelectric devices

12 Element substrate

14 Lower electrode film

15 Piezoelectric film

16 Upper electrode film

17 nodes,

18 Bonding layer

20 Lid substrate

21 Snoley Honore

25 outermost layer

26 Solder bump (external terminal)

30 collective board (second collective board)

32 Photosensitive resin (resin layer)

33 Notch 34 Opening (through hole)

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, examples of the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 is a cross-sectional view of the piezoelectric device 10. Piezoelectric device 10 is a BAW filter

. In the piezoelectric device 10, the element substrate 12 and the lid substrate 20 are bonded to each other.

On the element substrate 12, an insulating film 13, a lower electrode film 14, a piezoelectric film 15, and an upper electrode film 16 are formed. The insulating film 13 floats from the element substrate 12 through the gap 19. In this portion, a vibrating portion 11 in which a piezoelectric film 15 is sandwiched between electrode films 14 and 16 is formed, and the element substrate 12 force is also acoustically separated. A pad 17 is formed on the electrode films 14 and 16. Further, a bonding layer 18 is formed on the entire periphery along the periphery of the element substrate 12 outside the pad 17.

The lid substrate 20 has a pad 27 formed on the surface facing the element substrate 12 and joined to the pad 17 on the element substrate 12 side. In addition, a bonding layer 28 is formed on the entire periphery along the periphery of the lid substrate 20, and is bonded to the bonding layer 18 on the element substrate 12 side so as to seal the piezoelectric element formed on the element substrate 12. Yes. A through hole, that is, a through hole 21 is formed in the lid substrate 20. The through hole 21 is filled with a conductive material 22, and an external terminal connection electrode 23 is formed thereon.

[0037] On the lid substrate 20 and the external terminal connection electrode 23, an outermost layer 25 made of grease is formed to prevent solder erosion. The outermost layer 25 is provided with an opening 34 through which the external terminal connection electrode 23 is exposed, and an under bump metal 24 is disposed. A solder bump 26 is formed immediately above the under bump metal 24. The opening 34 may be formed immediately above the through hole 21 or may be formed at a position away from the through hole 21.

Next, the manufacturing process of the piezoelectric device 10 will be described with reference to FIGS. 1 and 2 to 4. The piezoelectric device 10 is manufactured in a state of a collective substrate in which portions corresponding to a plurality of piezoelectric devices 10 are two-dimensionally arranged in a grid, for example.

First, the insulating film 13, the lower electrode film 14, the piezoelectric film 15, and the upper electrode film 16 are formed on the first collective substrate that becomes the element substrate 12, and at least one vibrating portion 11 is formed. Then, the pad 17 and the bonding layer 18 are formed using the same conductive adhesive. For example, the element substrate 12 For example, a Si substrate having a thickness of 300 μm to 500 μm is used. For the piezoelectric film 15, for example, ZnO, A1 N, BaTiO, KNbO, PZT, or the like is used. For each electrode film 14, 15, for example, Al, Au,

3 3

Use metals such as Cu, Ir, Mo, Ni, Pd, Pt, Ta, and W. For the pad 17 and the bonding layer 18, for example, a material such as Cu, Au, Ni, Sn, or a laminate thereof is used.

On the other hand, the pad 27 and the bonding layer 28 are formed on the second collective substrate to be the lid substrate 20 by using the same conductive adhesive material. As the conductive adhesive, materials such as Cu, Au, Ni, Sn, etc., or a laminate thereof are used. The thickness of the lid substrate 20 is, for example, 300 m to 500 m. The lid substrate 20 preferably has the same material force as the element substrate 12. If the same material is used, the linear expansion coefficient will be the same, and even if there is a temperature change, excessive force will be applied to the joint parts such as the pads 17, 27 of the element substrate 12 and lid substrate 20 and the bonding layers 18, 28. This is because the piezoelectric device 10 that is resistant to thermal stress can be formed.

[0041] Next, the pads 17 and 27 and the bonding layers 18 and 28 of the element substrate 12 and the lid substrate 20 are aligned, and while heating and pressurizing the first collective substrate and the second collective substrate, Electrical bonding and sealing bonding are performed simultaneously.

[0042] Next, the surface side of the second collective substrate opposite to the first collective substrate is polished while the first collective substrate and the second collective substrate are joined. Thinning by polishing, polishing, RIE (reactive ion etching), wet etching, or a combination of these methods. For example, the lid substrate 20 having a thickness of 300 μm to 500 μm before bonding is thinned to 100 μm or less by grinding using a mortar billiform # 360, resin # 800, # 2000 or the like. When the lid substrate 20 thinned by grinding is further thinned, RIE or the like having a small mechanical load is used.

Next, through-holes 21 are formed in the portion immediately above the pads 27 of the second aggregate substrate by a method such as RIE, wet etching, or laser processing. When using RIE, resist, Al, SiO, AlO, etc. are formed on the surface of the second aggregate substrate as a processing mask, and RIE processing is performed.

2 2 3

For example, a through hole 21 having a diameter of 100 μm or less is formed.

Next, connection conductors 22 and 23 are formed in the portion of the through hole 21 formed in the second aggregate substrate. That is, the inside of the through hole 21 is filled with a conductive material 22 such as plating or conductive paste, and the external terminal connection electrode 23 is formed thereon. Minute through hole When 21 is filled, plating is desirable.

[0045] Instead of filling the through hole 21 with the conductive material 22, a metal film is formed on the side surface of the through hole 21 by using, for example, sputtering, vapor deposition, or plating. The external terminal connection electrode 23 may be formed in the vicinity of 21.

Next, as shown in FIG. 2 (a), a photosensitive resin for forming the outermost layer 25 on the surface 31 of the second aggregate substrate 30 on the side where the external terminal connection electrodes 23 are formed. Apply 32. As the photosensitive resin 32, photosensitive polyimide is applied by a spin coater. The photosensitive resin 32 may be one having high heat resistance such as photosensitive epoxy in addition to photosensitive polyimide. You can also attach a photosensitive film.

[0047] Next, exposure was performed with a photomask applied, and development was performed with an organic solvent or the like to form a notched portion 33 having no grease and an opening 34, as shown in FIG. 2 (b). To do. The notches 33 are generally formed in a lattice shape along cutting lines (dicing lines) for cutting the collective substrate 30 in order to separate the individual piezoelectric devices 10. The external terminal connection electrode 23 is exposed from the opening 34. The photosensitive resin 32 is formed so that the film thickness after curing is 2 m to 6 m.

[0048] Next, an electrode film made of Au, Ni, or the like, that is, an under bump metal 24, is formed in the opening 34 formed in the photosensitive resin 32 with substantially the same thickness as the photosensitive resin 32 by electroless contact. The

[0049] Next, the surface of the first collective substrate opposite to the second collective substrate is thinned by a method such as polishing ij, polishing, RIE, wet etching, or a combination of these methods. . For example, in the case of grinding, the element substrate 12 having a thickness of 300 μm to 500 μm is thinned to 100 μm or less by using a grinding wheel pyrifide # 360, resin # 800, # 2000 or the like. For further thinning, use RIE with a small mechanical load.

[0050] Next, a solder paste such as Su-Ag-Cu is printed directly on the under bump metal 24 formed on the second collective substrate through a metal mask, and a temperature at which the solder paste dissolves, for example, about 260 Heat at about ° C to fix the solder to the under bump metal 24, remove the flux with a flux cleaner, and form spherical solder bumps 26.

[0051] Finally, the collective substrate is cut into pieces by a method such as dicing, and the piezoelectric device 10 is completed. [0052] By manufacturing the piezoelectric device 10 as described above, it can be efficiently produced as in the following (1) to (3).

[0053] (1) When dicing the bonded assembly board (bonded wafer) and the solder wetting prevention material at the same time, blade clogging occurs. A) Sealing width becomes narrow due to occurrence of chipping. B) Decrease of blade selectivity due to simultaneous dicing of both bonded wafer and resin to prevent solder erosion, c) Bonded portion easily breaks due to wafer cracking, etc. Trouble occurs.

In the piezoelectric device 10, since the photosensitive resin 32 is used for the outermost layer 25, the cut portion 33 can be formed using a photolithography technique. For this reason, as shown in FIG. 3, it is possible to form the cut portions 33 in all the thickness directions. As shown in FIG. 4, blade clogging cannot be eliminated in the case of the notch 33x where the photosensitive resin 32 is not sufficiently removed. By removing all the photosensitive resin 32 on the dicing line for the thickness of the dicing blade in advance, the clogging of the blade can be eliminated and the above-mentioned problem in dicing can be solved. As a result, the yield is improved by 20% compared to the case where the bonded wafer is diced at the same time as the solder erosion prevention resin.

[0055] (2) As in Patent Document 1, in the case where a notched portion having no grease is formed in the sealing resin after the formation of the solder external terminals, the warp is not warped in the process after the formation of the sealing resin. to be influenced. That is, when one surface of the bonded wafer is polished to, for example, 100 m or less and the outermost layer resin is formed on the polished surface, the wafer is already warped by the polishing, and the outermost layer resin is formed to further warp. growing. Therefore, the wafer is easily broken and the influence of the warpage on the process after the outermost layer resin formation is increased. Also, when solder paste is applied by the printing method to form solder external terminals, problems such as a) poor suction during printing, b) misalignment of printing, and c) cracking of the wafer during printing occur.

In the piezoelectric device 10, the warp of the resin 32 serving as the outermost layer 25 is formed by forming the notch 33 simultaneously with the formation of the opening (via hole) 34 when forming the resin 32 serving as the outermost layer 25. It is possible to reduce the influence of warpage in the next process.

[0057] Piezoelectric device 10 is a wafer in which, for example, when outermost layer resin thickness is 2 to 6 μm and bonded wafer total thickness is 180 μm, notch 33 having no resin is formed in outermost layer resin. Warping The amount is about lmm. By forming the notch 33, the amount of warpage is reduced to about 20 m. If the solder external terminal is formed by the printing method without forming the notch in the outermost layer resin, the deviation of the solder external terminal diameter is about ± 30% due to the effect of warping, but by inserting the notch 33 Can be reduced to ± 5%. This is because the warp has a concave shape, so that a space is formed between the metal mask at the center of the wafer and the wafer, solder bleeding occurs at the center, and the amount of solder increases.

(3) Simplification of the process is realized by simultaneously forming the notch 33 into the outermost layer resin and the opening 34 for connecting the external terminal. In addition, when the photolithography technique is used as a method of forming the cut portion 33, the processing cost can be reduced by about 40% as compared with dicing.

Note that the piezoelectric device and the manufacturing method thereof according to the present invention are not limited to the above-described embodiments, and can be implemented with various modifications.

[0060] For example, the BAW filter may be acoustically separated from the substrate by an opening or an acoustic reflection layer provided in the substrate. Piezoelectric elements other than BAW filters, such as SAW (surface acoustic wave) filters, may be formed.

Claims

The scope of the claims

[1] an element substrate on which a piezoelectric element is formed;

A lid substrate that is bonded along the periphery of the element substrate and seals the piezoelectric element, and an external body mainly composed of solder disposed on a main surface of the lid substrate opposite to the element substrate. A terminal,

The main surface of the lid substrate opposite to the element substrate is provided with an outermost layer made of a resin covering a portion other than the external terminals,

The first collective substrate serving as the element substrate of a plurality of piezoelectric devices and the second collective substrate serving as the lid substrate of a plurality of piezoelectric devices are bonded to each other. Are cut along the cutting line and separated into individual piezoelectric devices,

The second aggregate substrate before being cut has a resin layer that is the outermost layer formed on the surface opposite to the surface to which the first aggregate substrate is bonded,

The piezoelectric device is characterized in that a cut portion having no grease is formed along the cutting line in the resin layer before the second aggregate substrate is cut.

[2] The piezoelectric device according to [1], wherein the resin layer forming the outermost layer is a paste resin applied and then cured.

[3] The piezoelectric device according to [1], wherein the resin layer forming the outermost layer is formed by bonding a film material.

4. The piezoelectric device according to claim 2, wherein the pasty resin is a photosensitive resin.

5. The piezoelectric device according to claim 3, wherein the film material is a photosensitive film.

[6] The cut portion formed in the resin layer has a substantially lattice shape.

The piezoelectric device according to claim 1.

7. The piezoelectric device according to claim 1, wherein the cut portion formed in the resin layer substantially follows the outer shape of the piezoelectric device.

[8] The width of the cut portion formed in the resin layer cuts the second aggregate substrate. The piezoelectric device according to claim 1, wherein the piezoelectric device has a width equal to or greater than a width of a dicing blade used sometimes.

2. The piezoelectric device according to claim 1, wherein a through-hole penetrating the resin layer in a thickness direction is formed in the resin layer simultaneously with the formation of the cut portion.