JP2003152007A - Bump forming method and mounting structure of semiconductor device - Google Patents

Abstract

(57) [Summary] [Problem] To be able to cope with the narrow pitch of electrode pads accompanying high density and high integration of LSIs and the like, and to use Pb-free to increase the height of the electrode pad to about the diameter in a short time. It is an object of the present invention to provide a bump forming method and a semiconductor device mounting structure capable of forming a bump having the same. The present invention provides a first film forming step of forming a thin film metal layer on a target surface in which electrode pads are arranged and the periphery of the electrode pads is covered with a protective film or an insulating film;
The thin film metal layer formed in the first film forming step is used as a conductive film, and a portion corresponding to the electrode pad on the thin film metal layer is electroplated with a Pb-free metal to form a metal pad portion. A second film forming step of forming a film, a removing step of removing at least a portion of the thin film metal layer formed in the first film forming step protruding from the metal pad portion, and after the removing step, Forming a spherical Pb-free metal pad bonded on the electrode pad by melting the metal pad portion formed in the film forming step (2). Is the way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can cope with a narrower pitch of electrode pads accompanying the higher density and higher integration of LSIs and the like, and moreover, by using Pb-free, electronic parts such as LSIs can be connected on a substrate. The present invention relates to a bump forming method and a mounting structure for a semiconductor device, which can form the bumps in a short time.

[0002]

2. Description of the Related Art As a conventional method for forming bumps on an LSI or the like, in the case of connection by solder, printing with a solder paste (prior art 1) and formation with solder balls (prior art 2) are the mainstream.

Further, as the prior art 3, as shown in P. 12 209-P. 210 is known. This prior art 3 is a bump forming method using a dip of 30 μm pitch.

As the prior art 4, Japanese Patent Laid-Open No. 10-
No. 50713 is known. In this conventional technique 5, a first solder having an area larger than that of the base electrode is formed on the base electrode formed at a predetermined position on the substrate by vapor deposition using a lift-off method which is a film forming technique. The protrusion is formed, then a second solder having a melting point lower than that of the first solder is formed on the upper side of the first solder by a dip soldering method, and then the first solder is formed. It is described that the first and second solders are heated at a temperature higher than the melting point of the solder, and the first and second solders are melted and agglomerated (sphericalized by surface tension) to form higher solder bumps. ing.

[0005]

By the way, LSI
With the higher density and higher integration of ICs, etc., the pitch of electrode pads of LSI etc. has become narrower than 0.1 mm, and
Pb-free bumps have been required for bumps.

As described above, in order to reduce the pitch, printing with the solder paste according to the prior art 1 has poor printability, and positioning with the solder balls according to the prior art 2 makes positioning of the balls difficult.

Therefore, when the prior art 3 which can cope with the narrow pitch is used, the bump height is low because the bumps are formed by dipping, and the COG (Chip on Glas) is reduced.
However, there is a problem that unconnection at the time of mounting connection is likely to occur because the connection is limited to a substrate with a small warpage and the bump volume variation is large.
Furthermore, even if mounting and connection to the board is possible, the distance between the LSI and the board after connection becomes short, and shear strain of the solder increases due to mismatch of the linear expansion coefficient between the LSI and the board. There is a possible problem that the property will decrease.

In order to solve this problem, when the prior art 4 is to be used, the second solder having a lower melting point than the first solder is used on the upper side of the first solder by the dip soldering method. As in the case of the prior art 3, since the bumps have a large volume variation in the bump volume, there is a problem that disconnection is likely to occur during mounting connection. Is not considered.

An object of the present invention is to solve the above problems.
Bumps that can cope with the narrowing of the pitch of the electrode pads accompanying the high density and high integration of LSI and the like, and that can use Pb-free to form bumps having a height about the diameter of the electrode pads in a short time It is to provide a forming method and a mounting structure of a semiconductor device.

[0010]

In order to achieve the above object, the present invention provides a thin metal layer for a target surface in which electrode pads are arranged and the periphery of the electrode pads is covered with a protective film or an insulating film. And a Pb-free portion on the thin-film metal layer corresponding to the electrode pad by using the thin-film metal layer formed in the first film-forming step as a conductive film. Second film forming step of electrolytically plating the above metal to form a metal pad section, and removing at least a portion protruding from the metal pad section in the thin film metal layer formed in the first film forming step And a metal pad for forming a spherical Pb-free metal pad bonded on the electrode pad by melting the metal pad portion formed in the second film forming step after the removing step. Having a forming step A bump forming method according to claim.

Further, the present invention is characterized in that, in the second film forming step of the bump forming method, the area or diameter of the metal pad portion is made larger than the area or diameter of the electrode pad. Further, the present invention is characterized in that, in the second film forming step of the bump forming method, the Pb-free metal is Sn or a Sn alloy. Further, the present invention is characterized in that, in the first film forming step of the bump forming method, the thin film metal layer contains Cu, Ag or Au as a main component. Further, the present invention is characterized in that, in the removing step of the bump forming method, the thin film metal layer around the electrode pad is also removed. Further, the present invention provides a first film forming step of forming a thin film metal layer on a surface where electrode pads are arranged and the periphery of the electrode pads is covered with a protective film or an insulating film, and the first film forming step. A resist film is formed on the thin-film metal layer formed in the film forming step by opening a portion corresponding to the electrode pad as a metal pad portion forming area having an area or diameter larger than the area or diameter of the electrode pad. And forming Sn or Sn in the metal pad portion forming area of the resist film formed in the resist film forming step by using the thin film metal layer formed in the first film forming step as a conductive film. A second film forming step of electrolytically plating a metal made of an alloy to form a metal pad portion, and removing at least the resist film, and at least the thin film metal layer formed in the first film forming step The removing step of removing a portion protruding from the metal pad portion, and the thin film metal layer left by melting the metal pad portion formed in the second film forming step after the removing step are described above. And a metal pad forming step of forming a spherical metal pad bonded on the electrode pad by dissolving it in the metal pad portion.

Further, the present invention is a mounting structure of a semiconductor device, characterized in that the semiconductor device having metal bumps formed by the bump forming method is mounted on a substrate. Further, according to the present invention, a semiconductor device having metal bumps formed by the bump forming method is mounted on an interposer, and is further mounted on a main board by using Pb-free solder. It is a structure.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a bump forming method according to the present invention will be described with reference to the drawings.

The present invention, as shown in FIGS. 1 (a) and 1 (b), has a thin film of about 0.1 to 0.5 μm on an electrode pad 4 provided on an electronic component such as an LSI chip (semiconductor device). A metal layer (Cu, Ag, Au, etc.) 2 is formed by electroless deposition, vapor deposition, or sputtering, and is formed on the metal layer 2 so as to have a diameter larger than that of the electrode pad 4 and has a thickness of about 20 to 50 μm. Pb-free metal bumps (Sn or S
Sn alloy such as n-Ag, Sn-Bi, Sn-Cu) 1 is electroplated, and unnecessary portions of the thin film metal layer 2 are removed by an etchant, and then the electroplated metal on the remaining thin film metal layer 6 is removed. The thin-film metal layer 6 is melted in the metal bump portion 1 by melting the bump 1, and the molten bump is subjected to a resin (SiO 2) on the electronic component by surface tension.
₍₂ , SiN, etc.) 3 so that the bump height is increased by making the bumps spherical by retreating from them, and forming bumps corresponding to Pb-free and narrow pitches. In this way, by using the thin film metal layer 2 as a current-carrying film, 20-50 μm
Pb-free metal bumps with a certain thickness (Sn or Sn alloys such as Sn-Ag, Sn-Bi, Sn-Cu)
1 can be electroplated in a short time. Moreover, the molten bump is made to recede from the resin (SiO ₂ , SiN, etc.) 3 on the electronic component due to the surface tension to make it spherical, so that the electrode pad can be formed. P with a height almost equal to the diameter of 4
The b-free metal bump 7 can be formed.

FIG. 2 shows a concrete first embodiment.
~ It demonstrates using FIG.

In the first embodiment, first, as shown in FIG.
As shown in FIG. 3, a substrate on which an electrode pad 4 of Al or the like is formed, and a protective film or an insulating film (a protective film of SiO ₂ , SiN or the like) 3a which is hard to be wet by Sn, Cu or the like is formed on a portion other than the electrode portion. (Electronic parts such as LSI chip) were prepared. At this time, the electrode pads 4 arranged on the electronic component are
The pitch was about 100 μm, the diameter was about 50 μm, and the pitch was narrow.

Next, as shown in FIG. 2B, a thin film C having a thickness of about 0.2 μm is formed on this substrate by electroless Cu plating.
After forming the u layer 2a, only the area for bump formation is C
A resist film 5 was formed so that u was exposed. The bump formation area where Cu is exposed is about 50 μm for the electrode diameter.
Approximately 7 to obtain a bump height of approximately 50 μm after melting
It was set to 0 μm. The Cu layer formed by electroless plating was used as the thin-film metal layer 2 having a thickness of about 0.1 to 0.5 μm because it can be bonded to the electrode pad 4 and S
It can be melted with bump metal 1a such as n.
It can be used as a current-carrying film when electrolytically plating the n-bump metal 1a, and can be used as a protective film or an insulating film (SiO ₂ , SiN).
This is because the adhesiveness to the protective film 3a, etc. is small. Therefore, as the thin-film metal layer 2, electroless Cu plating, electroless Ag plating, vapor deposition Cu, vapor deposition Ag, vapor deposition Au, sputtered Cu, sputtered Au, or the like can be used. In the case of sputtering, it is necessary to optimize the sputtering conditions and the like so that atoms do not adhere to the protective film or the insulating film 3a.

Next, as shown in FIG. 2C, Sn that is Pb-free is formed on the bump forming area by electrolytic Sn plating.
The bump portion 1a was formed. The bump thickness was about 30 μm. The plating solution used was a sulfuric acid-acid Sn plating bath. The liquid composition and electrolytic plating conditions are shown in FIG. Thus, P
By forming the b-free metal bump portion 1 by electrolytic plating, it is possible to form a film with a thickness of about 30 μm in a short time of about 60 minutes and with less volume variation than the dip method. Become. The material of the metal bump portion 1 is, in addition to Sn, Sn-A containing Sn as a main component.
It is possible to use Sn alloys such as g, Sn-Bi, or Sn-Cu. However, any material is deposited by electrolytic plating.

After that, as shown in FIG. 2D, the resist film 5 is stripped, and the exposed Cu (leached from the Sn bump portion 1a) after the resist stripping is performed using an ammonia-based etchant. It was removed to leave the thin film Cu layer 6a.

Next, as shown in FIG. 2E, the Sn bump portion (Sn electrolytic plating film forming portion) 1a on the thin film Cu layer 6a having a diameter larger than that of the electrode pad 4 formed as described above.
Is melted and the thin film Cu layer 2a is melted in the Sn bump portion 1a to recede and make the Sn bump portion 1a spherical due to the surface tension, so that the height variation on the electrode pad 4 is higher than that of the dip method. Metal bumps with a small amount (Mn bumps made of Sn mixed with Cu for the film thickness)
7a could be formed on the electrode pad 4. Moreover, the height of the metal bump 7a is about 50 μm, and the required bump height can be obtained.

Next, similarly, the electrode pad pitch is set to 50 μm.
m, 70 μm, 120 μm, 150 μm, and electrode pad diameters of 25 μm, 35 μm, 60 μm, and 75 μm (1/2 of the pad pitch).
In addition, the same solder resist 3a, electrolytic Sn plating bath, resist film 5, and etchant were used, and the formation process was performed in the same manner as the step shown in FIG. Electrolytic Sn plating film thickness (bump height before melting) is about 17 μm, about 23
μm, about 40 μm, about 50 μm. In addition, electrolysis S
The n plating time is about 34 minutes, about 46 minutes, about 80 minutes, and about 100 minutes, which is about 20 minutes per film thickness of about 10 μm, which is about 2 minutes as compared with the case where all the bumps 7a are electroplated.
The film could be formed at a ratio of / 3 in a relatively short time.
Further, by melting the Sn bump portion 1a on the thin film Cu layer 6a and melting the thin film Cu layer 2a in the Sn bump portion 1a, the height of the metal bump 7a after melting is:
The results shown in FIG. 4 were obtained. As described above, under any of the conditions, the height of the metal bumps (metal bumps made of Sn mixed with Cu) 7a having the diameter of the electrode pad can be obtained after the bump formation. In short, by using the thin film Cu layer 2a as an electrically conductive film, the Sn bump portion 1a is electroplated in a relatively short time, and then the Sn bump portion 1a is melted to obtain a spherical shape having a height about the diameter of the electrode pad. It is possible to form the Pb-free metal bumps 7a that have been turned into solid.

Next, a concrete second embodiment will be described with reference to FIG. The second embodiment differs from the first embodiment in that, as shown in FIG. 5D, Sb is Pb-free due to Sn electrolytic plating.
After forming the n-bump portion 1a, the resist 5 is peeled off, and the exposed thin film metal layer of Cu or the like after peeling off the resist and the thin film Cu layer 2a around the bump are removed using an ammonia-based etchant. This is to leave the thin film Cu layer 6a ′ having a diameter smaller than the diameter of the bump portion 1a. In this way, the thin film Cu layer under the periphery of the bump is also removed by using the ammonia-based etchant, so that the thin film CU
The layer 2a may be formed under the condition that the layer 2a has adhesiveness with the protective film or the insulating film 3a, such as sputtering. The thin-film Cu layer 2a may be the thin-film metal layer 2 described above, and the Sn bump portion 1a may be a metal bump made of Pb-free Sn or Sn alloy formed by electrolytic plating as described above. Part 1 can be used.

The other points of the second embodiment are the same as those of the first embodiment shown in FIG.

The Sn bump portion 1a on the thin-film Cu layer 6a 'having a diameter larger than the diameter of the electrode pad 4 thus formed and smaller than the diameter of the Sn bump portion 1 is melted, and the Sn pad portion 1a is formed on the electrode pad 4. The bump 7a was formed. The height of the bump 7a after formation was about 50 μm, and the required bump height could be obtained.

Next, mounting of electronic components such as LSI chips (semiconductor devices) having bumps formed by the bump forming method according to the present invention will be described with reference to FIG. That is, FIG.
As shown in (a) and (b), a thin film metal layer 6 of Cu or the like is provided on a large number of electrode pads 4 of Al or the like arranged on the LSI chip 10, and the thin film metal layer 6 of the electrode pads 4 is formed on the thin film metal layer 6. A square, polygonal, or circular metal bump portion 1 of Sn or the like having a diameter larger than the diameter (including the diameter inscribed) is formed by electrolytic plating.

Next, as shown in FIG. 6 (c), the metal bump portion 1 made of Sn or the like is melted and the thin film metal layer 6 made of Cu or the like is also melted and mixed to be spherical due to the surface tension to form P.
A b-free metal bump 7 of Sn or the like is formed.

Next, a metal bump 7 made of Pb-free Sn or the like is used.
By mounting the LSI chip 10 on which the interposer 11 is formed on the electrode pad 12 on the interposer 11 and heating the same, the LSI chip 10 and the interposer 11 are exposed to Pb.
The metal bumps 7 made of free Sn or the like are electrically connected in a state of being separated from each other. Then, an underfill 13 is filled between the LSI chip 10 and the interposer 11 and cured to form the underfill 13. Thus, the interposer 11 having the LSI chip 10 mounted thereon is also referred to as a semiconductor device according to the present invention. Further, another electronic component 20 having a Pb-free metal bump 7 of Sn or the like formed on the surface of the interposer 11 is placed on the electrode pad 12 on the surface of the interposer and is heated, whereby the other electronic component is added. 20 will be implemented.

As described above, the LSI chip 10 and other electronic components 2
On the electrode pad 14 on the back surface of the interposer 11 on which 0 is mounted, for example, the above-described Pb-free spherical metal bump 15 of Sn or the like may be formed. And
Interposer 11 having metal pad 14 formed on the back surface
Is placed on the electrode pad 16 on the main board 17 and is heated, so that the interposer 11 is connected to the main board 17 so that the metal bump 1 made of Pb-free Sn or the like.
5, they are electrically connected and mounted at a distance. The electronic chip mounting structure such as the LSI chip shown in FIG. 6 is mounted on the main board 17 via the interposer 11. However, the LSI chip (semiconductor device)
The bump forming method according to the present invention can be applied to a structure in which an electronic component such as is mounted on a substrate such as a main board.

As described above, according to the first and second embodiments, Pb is applied to the electrode pads with a narrow pitch.
By forming the free Sn or Sn alloy bumps by electrolytic plating, it is possible to form them thicker with less volume variation than in the dip method in a relatively short time. By melting the metal bump part above,
It becomes possible to form a spheroidized metal bump having a height approximately equal to the diameter of the electrode pad, and as a result, secure connection reliability between an electronic component such as an LSI chip and a substrate on which the electronic component is mounted. It becomes possible.

[0030]

According to the present invention, it is possible to shorten the time for depositing Sn or Sn alloy that can be made Pb-free and to form spherical bumps with less volume variation. There is an effect that it is possible to cope with a narrower pitch, and further, it is possible to secure connection reliability between an electronic component and a substrate on which the electronic component is mounted.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a basic configuration of a bump forming method according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a process from forming a thin metal layer on an electrode pad to forming bumps by melting in the first embodiment of the bump forming method according to the present invention.

FIG. 3 is a diagram showing the composition and working conditions of the electrolytic Sn plating bath used for bump formation in the first embodiment of the bump forming method according to the present invention.

FIG. 4 is a graph showing the height before and after melting of a bump formed by electrolytic Sn plating in the first embodiment of the bump forming method according to the present invention.

FIG. 5 is a schematic cross-sectional view showing a process from forming a thin metal layer on an electrode pad to forming bumps by melting in the second embodiment of the bump forming method according to the present invention.

FIG. 6 is a schematic cross-sectional view showing a mounting process of forming bumps on an LSI chip or an interposer and connecting them to a main board in forming bumps according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Metal bump part (electrolytic plating part), 1a ... Sn bump part (Sn electrolytic plating part), 2 ... Thin film metal layer, 2a ... Thin film Cu layer, 3 ... Protective film or insulating film, 4 ... Electrode pad, 5
... resist, 6 ... remaining thin film metal layer, 6a, 6a '...
Remaining thin film Cu layer, 7, 7a ... Spherical metal bump, 1
0 ... LSI chip (semiconductor device), 11 ... Interposer, 12 ... Electrode pad, 13 ... Underfill, 14 ...
Electrode pad, 15 ... Metal bump, 16 ... Electrode pad, 1
7 ... Main board.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kinhide Yamaguchi             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Inside the Hitachi, Ltd. production technology laboratory F-term (reference) 5E319 AA03 AB05 AC01 BB04 CC33                       CD26 GG15                 5E336 AA04 AA16 CC32 CC34 CC43                       CC55 DD12 EE03 GG05

Claims (9)

[Claims] 1. A first film forming step of forming a thin film metal layer on an object surface in which electrode pads are arranged and the periphery of the electrode pads is covered with a protective film or an insulating film, and the first film forming step. Second, a Pb-free metal is electrolytically plated on a portion of the thin-film metal layer corresponding to the electrode pad by using the thin-film metal layer formed in the film-forming step as a conductive film to form a metal pad portion. Film forming step, a removing step of removing at least a portion of the thin film metal layer formed in the first film forming step protruding from the metal pad portion, and the second film forming after the removing step. And a metal pad forming step of forming a spherical Pb-free metal pad bonded on the electrode pad by melting the metal pad portion formed in the step. 2. The bump forming method according to claim 1, wherein in the second film forming step, an area or a diameter of the metal pad portion is larger than an area or a diameter of the electrode pad. 3. The bump forming method according to claim 1, wherein Sn or Sn alloy is used as the Pb-free metal in the second film forming step. 4. The bump forming method according to claim 1, wherein the thin film metal layer contains Cu, Ag or Au as a main component in the first film forming step. 5. The bump forming method according to claim 1, wherein the thin film metal layer around the electrode pad is also removed in the removing step. 6. A first film forming step of forming a thin film metal layer on a surface of an array of electrode pads, the surface of which is covered with a protective film or an insulating film, and the first step. Using the thin film metal layer formed in the film process as an electrically conductive film, a metal corresponding to the electrode pad on the thin film metal layer is electrolytically plated with a metal composed of Sn or Sn alloy to reduce the area of the metal pad portion or A second film forming step of forming a metal pad portion having a diameter larger than the area or the diameter of the electrode pad, and at least from the metal pad portion in the thin film metal layer formed in the first film forming step. A removing step for removing the protruding portion, and a thin film metal layer left by melting the metal pad portion formed in the second film forming step after the removing step are dissolved in the metal pad portion. The electrode pack Bump forming method characterized by having a metal pad forming step of forming spheronized metal pad bonded to the upper. 7. A first film forming step of forming a thin film metal layer on a surface of an array of electrode pads, the surface of which is covered with a protective film or an insulating film, and the first step. A resist film in which a portion corresponding to the electrode pad is opened as a metal pad portion forming area having an area or diameter larger than the area or diameter of the electrode pad is formed on the thin film metal layer formed in the film process. By using the resist film forming step and the thin film metal layer formed in the first film forming step as a conductive film, Sn or Sn alloy is formed in the metal pad portion forming area of the resist film formed in the resist film forming step. A second film forming step of electrolytically plating a metal made of a metal to form a metal pad portion, and removing the resist film, and at least the front of the thin film metal layer formed in the first film forming step. A removing step of removing a portion protruding from the metal pad portion, and a thin film metal layer left by melting the metal pad portion formed in the second film forming step after the removing step are formed on the metal layer. And a metal pad forming step of forming a spherical metal pad bonded on the electrode pad by dissolving it in a pad portion. 8. A semiconductor device mounting structure comprising a semiconductor device having metal bumps formed by the bump forming method according to claim 1, 2 or 3 or 6 or 7 mounted on a substrate. . 9. A semiconductor device having metal bumps formed by the bump forming method according to claim 1, 2 or 3 or 6 or 7 is mounted on an interposer and further mounted on a main board using Pb-free solder. A mounting structure for a semiconductor device, which is configured.