JP2008227433A - Mounting body and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mounting body improved in yield and productivity by preventing a crack of a mounting board. <P>SOLUTION: The mounting body has a through hole 30 having a side wall with a taper shape in which an opening cross section becomes larger gradually as it goes from the front face side to the rear face side. The mounting body includes at least a mounting board 10 in which at least its front face side is formed of glass; an electrode pad 11 for covering the through hole 30 on the front face side; a function element 20 connected to the electrode pad 11; and a through electrode conductor which is connected to the electrode pad 11 extending to the rear face through the side wall, and thinner than one half of the thickness of the mounting board. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a packaging technology for functional components, and more particularly to a mounting body using a glass substrate having a through electrode and a manufacturing method thereof.

  In recent years, electronic devices such as mobile phones have been reduced in size and functionality. In accordance with the miniaturization and high functionality of electronic devices, high-density, high-reliability mounting technology for functional components used in electronic devices has been developed. However, due to the miniaturization of electronic devices, there is a limit to further reduction in mounting design dimensions. In particular, the development of two-dimensional mounting technology is reaching its limits from the design dimensions. For this reason, there is an urgent need to develop a three-dimensional mounting technology and a chip size package (CSP).

  As one of the three-dimensional mounting technologies, a micro electro mechanical system (MEMS) technology, which is a three-dimensional microfabrication technology applying semiconductor manufacturing technology, has attracted attention. For example, research and development of packaging of functional components applying MEMS packaging technology for bonding a silicon (Si) substrate and a glass mounting substrate is underway.

  In order to perform wiring to a functional component sealed on the surface of the mounting substrate used for such three-dimensional mounting, a through electrode is provided on the mounting substrate. The cross-sectional shape of the through hole for the through electrode is an inverted mesa shape, a rectangular shape, or a tapered shape corresponding to the through hole processing technique. Usually, a through electrode is formed by embedding a metal such as copper (Cu) or nickel (Ni) in a processed through hole by an electrolytic plating method or the like (see, for example, Patent Document 1).

  In electrolytic plating, a thick metal film can be formed, and it is possible to ensure not only electrical connection but also high airtightness. However, the mounting substrate is damaged or thermally strained by the through hole processing. If a thick metal film is embedded in the through hole without removing damage or thermal strain, the mounting substrate is likely to crack. In addition, due to the difference in thermal expansion coefficient between the mounting substrate and the embedded metal, stress is applied to the mounting substrate, causing cracks. As a result, the yield of the through electrode forming process is reduced.

Also, the deposition rate of electrolytic plating is slow, and it takes a long time to embed a thick metal film in the through hole. Therefore, the productivity of the through electrode forming process is poor.
JP 2006-184184 A

  An object of the present invention is to provide a mounting body capable of preventing cracks in a mounting substrate and improving yield and productivity, and a manufacturing method thereof.

  According to the first aspect of the present invention, (a) a mounting substrate that includes a through hole from the front surface side to the back surface side, at least the front surface side is made of glass, and (b) an electrode pad that covers the through hole on the front surface side; (C) a functional element connected to the electrode pad; and (d) connected to the electrode pad, extending to the back surface through the side wall of the through hole, and more than half the opening width of the through hole on the back surface side. A mounting body including a thin through electrode wiring is provided.

  According to the second aspect of the present invention, (b) a step of forming a through hole from the front surface side to the back surface side in the mounting substrate made of glass at least on the front surface side, and (b) closing the through hole on the front surface side. And (c) connecting to the electrode pad, extending to the back surface through the side wall of the through hole, and opening the through hole on the back surface side A step of forming a through electrode wiring thinner than 1/2 of the above, (d) a step of connecting the functional element to the electrode pad, and (e) a recess for housing the functional element so as to seal the functional element on the surface And a step of forming a sealing substrate having a mounting substrate on the mounting substrate.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the mounting body which prevents the crack of a mounting board | substrate, and can improve a yield and productivity, and its manufacturing method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  As shown in FIGS. 1 to 3, the mounting body according to the embodiment of the present invention includes a mounting substrate 10, an electrode pad 11, a through electrode wiring 15, a functional element 20, and a sealing substrate 22. The mounting substrate 10 includes a through hole 30 having a tapered side wall whose opening width is wider on the back surface (second main surface) side facing the front surface than on the front surface (first main surface) side. In FIG. 3, the upper surface of the mounting substrate 10 shown in FIG. 3 is defined as the front surface, and the lower surface of the mounting substrate 10 is defined as the back surface, but if the topology is such that the sealing substrate 22 is disposed on the front surface side, It is arbitrary whether to define the surface as a surface. The functional element 20 is disposed on the electrode pad 11. The sealing substrate 22 seals the functional element 20 on the inner side of the sealing substrate 22 with the concave portion provided in the sealing substrate 22 on the surface of the mounting substrate 10 as a gap 32.

  The electrode pad 11 includes a first metal film 12 and a second metal film 14. The first metal film 12 is provided on the through hole 30 so as to close the opening of the through hole 30 on the surface side of the mounting substrate 10. The second metal film 14 is provided on the first metal film 12.

  The through electrode wiring 15 includes a first conductive film 16 and a second conductive film 18. The first conductive film 16 is electrically connected to the electrode pad 11 exposed in the through hole 30. The second conductive film 18 is provided on the first conductive film 16. The through electrode wiring 15 extends to the back surface of the mounting substrate 10 through the side wall of the through hole 30. Further, as shown in FIG. 3, in the cross section cut perpendicularly to the surface of the mounting substrate 10, the opposing end portions of the pair of through electrode wirings 15 are provided apart from each other on the back surface side of the mounting substrate 10. It is done.

  As the mounting substrate 10, a glass substrate such as alkali glass, a ceramic substrate at least on the surface side made of glass, or the like is used. For the first metal film 12, a metal foil such as an aluminum (Al) foil, a Ni foil, or a kovar foil is used. For the second metal film 14, a metal film such as gold (Au) or a laminated metal film such as titanium (Ti) -platinum (Pt) -Au is used.

  As the sealing substrate 22, a Si substrate or the like is used. As the functional element 20, a crystal resonance element, a thin film piezoelectric resonance element (FBAR), a surface acoustic wave (SAW) element, a gyroscope element, an acceleration sensor element, or the like is used.

  The diameter (opening width) Wa of the through hole 30 on the surface side of the mounting substrate 10 may be equal to or larger than the minimum diameter that can ensure a desired contact resistance with respect to the functional element 20. For example, the opening width Wa ranges from about 1 μm to about 100 μm, desirably from about 5 μm to about 50 μm. 1 and 2, the circular through hole 30 is shown, but if it is rectangular, the short side is defined as the opening width Wa, and the opening width Wa is about 1 μm to about 100 μm, preferably about 5 μm to about 50 μm. It may be in the range. In the case of an ellipse, the minor axis is defined as the opening width Wa, and the opening width Wa may be in the range of about 1 μm to about 100 μm, preferably about 5 μm to about 50 μm.

  When the opening width Wa is smaller than 1 μm, the contact resistance between the through electrode wiring 15 and the electrode pad 11 is increased. If the opening width Wa exceeds 100 μm, it becomes difficult to ensure airtightness by the first metal film 12. For example, when the functional element 20 is sealed in an inert gas, the opening width Wa is desirably about 50 μm or less. When the functional element 20 is sealed in a vacuum of about 0.1 Pa or less, further airtightness is required. Therefore, the opening width Wa is preferably about 20 μm or less.

  Further, the opening width Wb of the through hole 30 on the back surface side of the mounting substrate 10 is in the range of t1 / 2 to t1 with respect to the thickness t1 of the mounting substrate 10. In the case of the rectangular through hole 30, the short side is defined as the opening width Wb, and the opening width Wb may be in the range of t1 / 2 to t1 with respect to the thickness t1 of the mounting substrate 10. In the case of the elliptical through-hole 30, the minor axis may be defined as the opening width Wb, and the opening width Wb may be in the range of t1 / 2 to t1 with respect to the thickness t1 of the mounting substrate 10.

  For the first conductive film 16, a laminated film of titanium nitride (TiN) -Cu or the like is used. A metal such as Au is used for the second conductive film 18. The total thickness of the first and second conductive films 16, 18, that is, the thickness t 2 of the through electrode wiring 15 is selected to be thinner than ½ of the opening width Wb of the through hole 30 on the back surface side of the mounting substrate 10. . It is preferably thinner than １ ／ of the opening width Wb, more preferably thinner than ¼ of the opening width Wb. Practically, if the thickness t1 of the mounting substrate 10 is about 200 μm to about 1000 μm, the opening width Wb of the through hole 30 is about 100 μm to 1000 μm, and the thickness t2 of the through electrode wiring 15 is about 1 μm to about 100 μm. And it is sufficient.

  For example, in order to ensure airtightness with respect to the through hole, the through electrode is usually formed by embedding metal in the through hole by an electrolytic plating method or the like. When a glass substrate is used as the mounting substrate 10, the through hole is usually processed from the back surface side of the glass substrate by a sandblast method. Due to the processing characteristics of sandblasting, the opening width on the back side of the glass substrate is approximately the same as the thickness of the glass substrate. For this reason, when a thick glass substrate is used in consideration of workability, the through hole becomes large. Therefore, the thicker the glass substrate, the greater the stress on the side wall of the through hole due to the through electrode embedded by plating. As a result, the glass substrate is cracked and it is difficult to ensure airtightness.

  In the mounting body shown in FIGS. 1 to 3, the first conductive film 16 and the second conductive film 18 are deposited on the side wall of the through hole 30 to provide the through electrode wiring 15. As shown in FIG. 3, the through electrode wiring 15 is thinner than ½ of the opening width Wb of the through hole 30, so that the inside of the through hole 30 is not completely embedded and has a gap. For this reason, the stress resulting from the through electrode wiring 15 is also small. Therefore, even if a glass substrate is used as the mounting substrate 10, the mounting substrate 10 can be prevented from cracking. As a result, it is possible to improve the yield of the through electrode wiring 15 formation.

  Further, the opening of the through hole 30 on the surface side of the mounting substrate 10 is closed by the first metal film 12 bonded to the mounting substrate 10 by anodic bonding. Here, the “anodic bonding” is a method in which a glass material containing movable ions and a Si substrate or a metal foil are overlapped and bonded by applying a voltage using the Si substrate or the metal foil as an anode by heating at room temperature or heating. is there. Since the opening width Wb of the through hole 30 is as small as about 100 μm or less, the airtightness is ensured by the bonded first metal film 12. Further, the first conductive film 16 and the second conductive film 18 are deposited so as to reinforce the surface of the first metal film 12 exposed in the through hole 30. Therefore, the airtightness with respect to the through hole 30 can be further improved.

  For example, a Si substrate is used as the sealing substrate 22. When the Si substrate is used, the sealing substrate 22 can be bonded to the mounting substrate 10 which is a glass substrate by anodic bonding. Therefore, the functional element 20 can be held in the gap 32 with good airtightness.

  As described above, according to the mounting body illustrated in FIGS. 1 to 3, the mounting substrate 10 can be prevented from cracking, and the functional element 20 can be hermetically sealed. As a result, it is possible to improve the manufacturing yield of the mounted body.

  Next, the manufacturing method of the mounting body shown in FIGS. 1 to 3 will be described using the cross-sectional views shown in FIGS. Here, the cross section corresponding to the AA line shown in FIG. 1 is shown in the cross sectional view used for the description.

  (A) As shown in FIG. 4, a resist film 50 having an opening with a diameter of about 150 μm is formed on the back surface of the mounting substrate 10 such as a glass substrate (the lower surface of the mounting substrate 10 in FIG. 4) by photolithography or the like. Using the resist film 50 as a mask, a through-hole 30 having a tapered side wall having an opening width of about 150 μm on the back surface side and an opening width of about 10 μm on the front surface side is formed by sandblasting or the like. The taper angle θ is about 10 to 30 degrees, preferably about 15 to 25 degrees. Thereafter, the resist film 50 is removed with a stripping solution or the like.

  (B) As shown in FIG. 5, a first metal film 12 such as an Al foil is bonded to the surface of the mounting substrate 10 by anodic bonding or the like. The anodic bonding is performed, for example, in a vacuum while heating the mounting substrate 10 to about 300 ° C. to about 400 ° C. and applying a voltage of about 400V to 1000V to the first metal film 12.

(C) As shown in FIG. 6, for example, a TiN film and a Cu film are sequentially deposited from the back side of the mounting substrate 10 by sputtering, chemical vapor deposition (CVD), or the like to form the first conductive film 16. The TiN film is deposited with a thickness of about 10 nm to about 20 nm in order to improve adhesion to the mounting substrate 10. The Cu film is deposited with a thickness of about 200 nm to about 300 nm by CVD using ammonia (NH ₃ ) gas as a carrier gas.

  (D) As shown in FIG. 7, Ti, Pt, and Au are sequentially deposited on the first metal film 12 on the surface of the mounting substrate 10 by sputtering or the like. The region including the through hole 30 of each of the Au film and the first conductive film 16 deposited on the first metal film 12 by photolithography, electrolytic plating, or the like is selectively plated with Au to form the second metal film 14 and A second conductive film 18 is formed. Thereafter, the first metal film 12 and the first conductive film 16 are selectively removed by photolithography, etching or the like, and the electrode pad 11 and the through electrode wiring 15 are formed.

  (E) As shown in FIG. 8, the functional element 20 is mounted on the second metal film 14 with a conductive adhesive such as silver paste. Alternatively, gold bumps may be provided on the second metal film 14 and the functional element 20 may be mounted on the second metal film 14 by thermocompression bonding using ultrasonic waves.

  (F) As shown in FIG. 9, a sealing substrate 22 made of a Si substrate provided with a recess is bonded to the surface of the mounting substrate 10 by anodic bonding or the like in a vacuum. At the time of anodic bonding, the concave portion of the sealing substrate 22 is aligned with the position of the functional element 20. As a result, the functional element 20 is sealed inside the sealing substrate 22 with the recess provided in the sealing substrate 22 as the gap 32. In this way, the mounting body shown in FIGS. 1 to 3 is manufactured.

  In the mounting body manufacturing method described above, the first conductive film 16 and the second conductive film whose total thickness is thinner than ½ of the opening width on the back surface side of the through hole 30 on the side wall of the through hole 30 by CVD, plating, or the like. Through-electrode wiring 15 is formed by depositing 18. Since the through hole 30 is not embedded, the stress caused by the through electrode wiring 15 is also small. Therefore, even if a glass substrate is used as the mounting substrate 10, the mounting substrate 10 can be prevented from cracking. In addition, the time required for forming the through-electrode wiring 15 can be greatly reduced as compared with the embedded plating in the through-hole. As a result, it is possible to improve the yield and productivity of forming the through electrode wiring 15.

  Further, the opening of the through hole 30 on the surface side of the mounting substrate 10 is closed by the first metal film 12 bonded to the mounting substrate 10 by anodic bonding. Further, the sealing substrate 22 is bonded to the mounting substrate 10 by anodic bonding. Therefore, the functional element 20 can be sealed in the gap 32 with good airtightness.

  Thus, according to the manufacturing method according to the embodiment of the present invention, it is possible to prevent the mounting substrate 10 from cracking and to seal the functional element 20 with good airtightness. As a result, it is possible to improve the manufacturing yield and productivity of the mounted body.

  The sealing substrate 22 is anodically bonded to the mounting substrate 10 using a Si substrate. However, a glass substrate, a ceramic substrate, or the like may be used as the sealing substrate. In this case, a metal film such as Al may be provided in advance on the bonding surface of either the mounting substrate or the sealing substrate, and anodic bonding may be performed.

(Other embodiments)
Although the embodiments of the present invention have been described as described above, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the embodiment of the present invention, a through hole having a tapered side wall whose opening cross-sectional area gradually increases from the front surface side to the back surface side is used as the through hole 30. However, as the through hole 30, a through hole having an arbitrary shape in a cross section perpendicular to the surface of the mounting substrate 10 may be used.

  For example, as shown in FIG. 10, it may be a through hole 30a having a vertical side wall from the front surface side to the back surface side. Moreover, as shown in FIG. 11, it may be a through-hole 30b having an inversely tapered side wall whose opening cross-sectional area becomes narrower from the front side to the back side. The opening width Wa of the through-hole 30 on the surface side of the mounting substrate 10 is in the range of about 1 μm to about 100 μm, desirably about 5 μm to about 50 μm, both in the vertical shape and the reverse tapered shape.

  Further, the sealing substrate 22 is bonded to a glass substrate as the mounting substrate 10 by anodic bonding. However, a metal adhesive layer such as Au may be provided on the sealing substrate and may be crimped to the mounting substrate by thermocompression bonding. In this case, the sealing substrate is not limited to the Si substrate, and a semiconductor substrate other than Si, an insulating substrate such as ceramic, or the like may be used.

  Further, in the embodiment of the present invention, the functional element 20 has been described as being exemplified by being vacuum-sealed. However, the functional element 20 may be sealed with an inert gas or the like. In the case of sealing with an inert gas, the sealing substrate 22 may be bonded to the mounting substrate 10 by anodic bonding or thermocompression bonding in an inert gas. Further, a resin substrate, a permanent thick film resist, or the like may be used as the sealing substrate.

  As described above, the present invention naturally includes various embodiments that are not described herein. Accordingly, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

It is the upper surface schematic diagram which shows an example of the mounting body which concerns on embodiment of this invention. It is a bottom face schematic diagram showing an example of a mounting object concerning an embodiment of the invention. It is the schematic which shows the AA cross section of the mounting body shown in FIG. It is sectional drawing (the 1) which shows an example of the manufacturing method of the mounting body which concerns on embodiment of this invention. It is sectional drawing (the 2) which shows an example of the manufacturing method of the mounting body which concerns on embodiment of this invention. It is sectional drawing (the 3) which shows an example of the manufacturing method of the mounting body which concerns on embodiment of this invention. It is sectional drawing (the 4) which shows an example of the manufacturing method of the mounting body which concerns on embodiment of this invention. It is sectional drawing (the 5) which shows an example of the manufacturing method of the mounting body which concerns on embodiment of this invention. It is sectional drawing (the 6) which shows an example of the manufacturing method of the mounting body which concerns on embodiment of this invention. It is a cross-sectional schematic diagram which shows an example of the mounting body which concerns on other embodiment of this invention. It is a cross-sectional schematic diagram which shows the other example of the mounting body which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Mounting substrate 11 Electrode pad 12 Metal foil 14 1st metal film 15 Through electrode 16 Conductive film 18 2nd metal film 20 Functional element 22 Sealing substrate 30 Through-hole

Claims (7)

A through-hole provided with a through hole from the front side toward the back side, at least the front side being made of glass,
An electrode pad covering the through hole on the surface side;
A functional element connected to the electrode pad;
A through-electrode wiring connected to the electrode pad, extending to the back surface through a side wall of the through-hole, and thinner than ½ of the opening width of the through-hole on the back surface side; To implement.   The through electrode wiring extends symmetrically on opposite side walls of the through hole in a cross section cut perpendicularly to the surface, and extends in opposite directions on the back surface. The mounting body according to claim 1.   The mounting body according to claim 1, wherein the through-electrode wiring surrounds the opening of the through-hole on the back surface and covers the entire side wall.   The mounting body according to any one of claims 1 to 3, further comprising a sealing substrate having a recess for housing the functional element so as to seal the functional element on the surface.   The mounting body according to any one of claims 1 to 4, wherein the mounting substrate is a glass substrate. A step of forming a through hole from the front surface side toward the back surface side on the mounting substrate made of glass at least on the front surface side;
Forming an electrode pad by bonding a metal foil to the mounting substrate so as to close the through hole on the surface side;
Forming a through electrode wiring connected to the electrode pad, extending to the back surface through the side wall of the through hole, and thinner than ½ of the opening width of the through hole on the back surface side;
Connecting a functional element to the electrode pad;
Forming a sealing substrate having a recess for housing the functional element on the surface so as to seal the functional element on the surface.   The method for manufacturing a mounting body according to claim 6, wherein the metal foil is bonded to the mounting substrate by anodic bonding.

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