JP3703807B2 - Semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device, a manufacturing method thereof, and a manufacturing apparatus.
[0002]
[Prior art]
In recent years, with the progress of semiconductor integrated circuits, semiconductor devices having a large number of terminals (for example, more than 300 terminals) have been put on the market. Along with this, improvement of technology for connecting terminals (electrodes) of semiconductor elements to terminals (electrodes) of a wiring board and reduction of costs are strongly desired.
[0003]
2. Description of the Related Art Advances have been made in a technique for collectively connecting electrodes of semiconductor elements to electrodes of a wiring board using metal bumps. That is, metal bumps such as solder bumps and gold bumps are attached to the electrodes of the semiconductor element, and when the semiconductor element is pressed face down toward the wiring board, the metal bumps are joined to the electrodes of the wiring board, and thus the electrodes of the semiconductor element Are connected to the electrodes of the wiring board.
[0004]
Since the conductor of an integrated circuit of a semiconductor device is made of aluminum, the electrode of the semiconductor device is generally made of aluminum. On the other hand, since the conductor of the wiring board is made of copper, the electrode of the wiring board is generally made of copper.
When using solder bumps, it is difficult to bond solder directly to aluminum, so a nickel layer and a titanium layer are added on the aluminum electrode of the semiconductor element, and the solder bump is bonded to the composite structure electrode of the semiconductor element. It is supposed to be. Then, when the semiconductor element is pressed against the wiring board while being heated, the solder bumps melt and spread on the electrodes of the wiring board, so that the solder bumps are well connected to the electrodes of the wiring board.
[0005]
When gold bumps are used, since gold is directly bonded to aluminum, it is not necessary to provide a nickel layer and a titanium layer on the aluminum electrodes of the semiconductor element as in the case of using solder bumps. However, the gold bump is attached to the electrode of the semiconductor element as a stud bump having a protrusion, and after leveling the surface of the stud bump and attaching a conductive adhesive to the surface of the gold bump, wiring while applying heat to the semiconductor element The gold bumps are pressed against the substrate and connected to the electrodes of the wiring substrate through the conductive adhesive. The conductive adhesive is a mixture of a thermosetting resin and a metal filler, and the conductive adhesive is thermoset. Thereafter, the semiconductor element and the wiring board are sealed with a fixing adhesive (insulating resin).
[0006]
[Problems to be solved by the invention]
As described above, when using solder bumps, it is necessary to add a nickel layer and a titanium layer on the aluminum electrode of the semiconductor element. Because special equipment is required, not all users of semiconductor devices can add nickel and titanium layers as desired. Therefore, when a semiconductor element to which a nickel layer and a titanium layer are not added is purchased, solder bumps may not be used.
[0007]
On the other hand, when a conductive adhesive is added to a gold bump formed as a stud bump, the leveled surface of the stud bump is not necessarily parallel to the surface of the wiring circuit, and it is sufficient to use a conductive adhesive. It cannot be said that electrical connection can be obtained, and the connection reliability is low. Further, the amount of materials used is increased, the manufacturing process is complicated, and heating must be continued until the resin is cured, resulting in poor productivity. Furthermore, in order to replace a semiconductor element when a semiconductor element defect or mounting defect occurs, it is necessary to remove the conductive adhesive from the electrode of the wiring board. However, since the conductive adhesive contains a thermosetting resin, it is difficult to remove the conductive adhesive once thermally cured. Therefore, it has been extremely difficult to repair semiconductor elements and wiring boards.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor device that can mount a semiconductor element on a wiring board face down, and that can improve the reliability of a connection portion and facilitate the replacement of the semiconductor element, and a manufacturing method and manufacturing apparatus thereof. Is to provide.
[0009]
[Means for Solving the Problems]
A semiconductor device according to the present invention includes a semiconductor element having an electrode, a gold bump element provided on the electrode of the semiconductor element, and a first metal attached around the gold bump element and protecting the gold bump element. And a metal bump comprising a second metal layer around the first metal layer, the melting point of the first metal layer being lower than the melting point of the gold bump element, and the second metal The melting point of the layer is characterized by being 20 ° C. or more lower than the melting point of the first metal layer.
Furthermore, a wiring board having electrodes is provided, and metal bumps attached to the electrodes of the semiconductor element are connected to the electrodes of the wiring board.
[0010]
The method of manufacturing a semiconductor device according to the present invention includes a step of attaching a gold bump element on an electrode of a semiconductor element, and immersing the semiconductor element in a bath in which an amalgam alloy in which a metal for protecting gold and mercury are mixed is melted. Forming an amalgam alloy layer on the gold bump element; heating the semiconductor element to evaporate mercury of the amalgam alloy; and forming a metal film on the gold bump element to protect gold; The solder element is melt transferred.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 are diagrams showing a semiconductor device of a reference example. In FIG. 1, the semiconductor device 10 includes a semiconductor element 12 having an electrode 14 and metal bumps 16 attached to the electrode 14.
The metal bump 16 includes a ball-shaped core 18 and a surface layer 20 covering the periphery of the core. The semiconductor element 12 is a bare chip constituting a semiconductor integrated circuit, and includes an integrated circuit (not shown) and a conductor 12a connected to the integrated circuit. The electrode 14 is connected to the conductor 12a. Although only one electrode 14 and one metal bump 16 are shown in FIG. 1, it goes without saying that a plurality of electrodes 14 and metal bumps 16 according to the number of terminals of the semiconductor element 12 are provided. The same applies to the subsequent embodiments.
[0012]
In FIG. 2, the semiconductor device 10 further includes a wiring substrate 22 having an electrode 24 in addition to the configuration of FIG. 1. The electrodes 24 of the wiring board 22 are connected to a circuit pattern (not shown) in the wiring board 22 and arranged in the same arrangement as the electrodes 14 of the semiconductor element 12. By pressing the semiconductor element 12 against the wiring substrate 22 while applying heat by face-down bonding, the metal bumps 16 attached to the electrodes 14 of the semiconductor element 12 are connected to the electrodes 24 of the wiring substrate 22. In this example, the metal bumps 16 are directly bonded to the electrodes 24 of the wiring board 22. Therefore, the semiconductor element 12 can be removed from the wiring board 22 for repair. Further, a fixing adhesive 26 is filled between the semiconductor element 12 and the wiring board 22. The fixing adhesive (insulating resin) 26 can be applied to the wiring board 22 in advance, or can be filled after the semiconductor element 12 is pressed against the wiring board 22.
[0013]
The electrode 14 of the semiconductor element 12 is made of aluminum, and the electrode 24 of the wiring board 22 is made of copper. In the example of FIGS. 1 and 2, the core 18 of the metal bump 16 is made of copper having a diameter of 100 μm, and the surface layer 20 is made of gold having a thickness of 10 μm.
FIG. 3 is a diagram showing a semiconductor device of a reference example. In this example, the semiconductor device 10 includes a semiconductor element 12 having an electrode 14, a gold bump element 62 provided on the electrode 14 of the semiconductor element 12, and a gold bump element 62 attached around the gold bump element 62. The metal bumps 16 are formed of the first metal layer 64 that protects 62.
[0014]
The first metal layer 64 is preferably made of solder having a property of suppressing the diffusion of gold. As described above, the solder is a brazing material made of a single metal or an alloy having a melting point of 400 ° C. or less. Suitable solders for suppressing gold diffusion include indium (In, melting point 280 ° C.), Au—Sn 20 percent alloy (melting point 280 ° C.), and the like.
[0015]
Alternatively, the first metal layer 64 can be a metal that becomes a barrier with poor reactivity with gold. Examples of metals having poor reactivity with gold include Bi, Ni, Zn, Cd, Cr, Ge, and Ga. Thus, by providing the first metal layer 64 around the gold bump element 62, the long-term stable action of the gold bump element 62 is ensured, and the reliability of the metal bump 16 is increased.
[0016]
FIG. 4 is a diagram showing a semiconductor device according to an embodiment of the present invention. In this embodiment, a second metal layer 66 is further provided around the first metal layer 64 of FIG. The first metal layer 64 protects the gold bump element 62, while the second metal layer 66 is made of solder that easily wets copper. Therefore, when the semiconductor element 12 is attached to the wiring board 22, the second metal layer 66 is reliably bonded by the copper electrode 24 of the wiring board 22.
[0017]
An example of the combination of the first metal layer 64 having the property of suppressing the diffusion of gold and the second metal layer 66 that easily wets copper is as shown in Example 1 below.
Example 1
Combination (a) (b) (c) (d)
First metal layer 64 In In Au-Sn 20% In
Second metal layer 66 In-Sn Sn-Bi-Ag 1% Same as on the left In-Ag
An example of a combination of the first metal layer 64 having a poor reactivity with gold and the second metal layer 66 that easily wets copper is as shown in Example 2 below.
Example 2
Combination (a) (b)
First metal layer 64 Bi Ni
Second metal layer 66 In-Sn Sn-Pb-In
In these examples, the melting point of In is 157 ° C, the melting point of Au-Sn 20% is 280 ° C, the melting point of In-Sn eutectic is 117 ° C, the melting point of Sn-Bi-Ag 1% is 139 ° C, Sn-Pb The melting point of -In is 162 ° C. The thickness of Bi and Ni is about 5000 angstroms. The melting point of Sn described in Example 3 is 232 ° C.
[0018]
Further, the first metal layer 64 and the second metal layer 66 can be formed by melt transfer. In this case, it is desirable that the melting point of the second metal layer 66 be 20 ° C. or more lower than the melting point of the first metal layer 64. If there is no temperature difference of 20 ° C. or more, when the second metal layer 66 is melt-transferred, the second metal layer 66 is melted in the melting tank of the first metal layer 64 and the second metal layer 66. This is because is not properly transferred onto the first metal layer 64. Example 3 satisfies such a condition.
Example 3
Combination (a) (b)
First metal layer 64 In Sn
Second metal layer 66 In-Sn Sn-Pb-In
Difference in melting point 40 ℃ 70 ℃
FIG. 5 shows another embodiment of the present invention. The semiconductor device 10 has a metal bump composed of a gold bump element 62, a first metal layer 70, and a second metal layer 74, as in the previous embodiment. This embodiment relates to a method for manufacturing such a semiconductor device.
[0019]
5A, a gold bump element 62 is attached on the electrode 14 of the semiconductor element 12, and the semiconductor element 12 is immersed in a bath 68 in which an amalgam alloy in which a metal for protecting gold and mercury are mixed is melted. An amalgam alloy layer is formed. Here, silver that is not highly reactive with gold is selected as the metal that protects gold. Silver is mixed with mercury to form an amalgam alloy (Hg + Ag).
[0020]
In FIG. 5B, the semiconductor element 12 is heated to evaporate mercury of the amalgam alloy (Hg + Ag), and as a result, an Ag metal film 70 that protects gold is formed on the gold bump element 62. In FIG. 5C, the semiconductor element 12 is immersed in a solder bath 72 in which solder has been melted. Therefore, as shown in FIG. 5D, the solder element 74 is melt-transferred onto the metal film 70. The semiconductor element 12 is attached to the wiring board 22 using the metal bumps formed in this way.
[0021]
【The invention's effect】
As described above, according to the present invention, a semiconductor device capable of mounting a semiconductor element on a wiring board face-down and improving the reliability of a connection part and facilitating replacement of the semiconductor element, and its A manufacturing method and a manufacturing apparatus can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing a semiconductor device of a reference example.
2 is a diagram showing a state in which the semiconductor element of FIG. 1 is attached to a circuit board.
FIG. 3 is a diagram illustrating a semiconductor device of a reference example.
FIG. 4 is a diagram showing a semiconductor device according to an embodiment of the present invention.
FIG. 5 is a diagram showing a semiconductor device according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Semiconductor device 12 ... Electrode 14 ... Semiconductor element 22 ... Wiring board 24 ... Electrode 26 ... Fixing adhesive 62 ... Gold bump element 64 ... 1st metal layer 66 ... 2nd metal layer 68 ... Amalgam alloy was fuse | melted Tank 70 ... first metal layer 74 ... second metal layer

Claims (4)

A semiconductor element having an electrode; a gold bump element provided on the electrode of the semiconductor element; a first metal layer attached around the gold bump element to protect the gold bump element; and A metal bump comprising a second metal layer around the metal layer, wherein the first metal layer is made of a metal that suppresses the diffusion of gold or has a poor reactivity with gold, and the second metal layer Is made of solder that easily wets copper, and the melting point of the first metal layer is lower than the melting point of the gold bump element, and the melting point of the second metal layer is 20 ° C. higher than the melting point of the first metal layer. A semiconductor device characterized by being low.   The semiconductor device according to claim 1, further comprising a wiring board having electrodes, wherein metal bumps attached to the electrodes of the semiconductor element are connected to the electrodes of the wiring board. In the metal bump, the first metal layer is made of indium, gold-tin, tin, bismuth, nickel, zinc, cadmium, chromium, germanium, gallium, or silver, and the second metal layer is indium-tin. 3. The semiconductor device according to claim 1, comprising: indium-silver, tin-bismuth-silver, tin-lead-indium. In the metal bump, the first metal layer is made of silver , a gold bump element is attached on the electrode of the semiconductor element, and the semiconductor element is immersed in a bath in which an amalgam alloy in which silver and mercury are mixed is melted. silver on the gold bump elements Te - forming a mercury amalgam alloy layer, and heating the semiconductor element silver - is obtained by forming a silver layer was evaporated mercury mercury amalgam alloy, and the second metal layer semiconductor equipment according to any one of claims 1 to 3, characterized in that formed by melt transfer the solder onto the first metal layer.

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