JP2809799B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Regarding a semiconductor device, Pb-Sn is formed on a surface of an Au plating layer constituting a metallized layer of a cap and a surface of an Au plated layer constituting a metallized layer of a heat sink.
Provided is a semiconductor device capable of improving the sealing airtightness and the heat radiation effect of a heat radiating plate, and improving the reliability of a chip by sufficiently spreading a brazing material with almost no voids. The chip is connected face-down to the package, the seal pattern formed on the package and the metallized layer formed on the cap are adhered by a brazing material, and the metallized layer formed on the back of the chip and the cap In a semiconductor device in which the metallized layer formed on the heat sink and the metallized layer formed on the heat sink are bonded by a brazing material whose main component is Pb-Sn, the metallized layer formed on the cap and the heat sink is A nickel-plated layer having a thickness of 0.5 μm or more that has recrystallized dense crystal grains and a film formed on the nickel-plated layer It is configured to have a gold plating layer having a thickness of 0.2 μm or more and 1.0 μm or less.

[Industrial applications]

The present invention relates to a semiconductor device, in particular, a Pb-layer is formed on a surface of an Au plating layer constituting a metallized layer of a cap constituting a semiconductor device and a surface of an Au plating layer constituting a metallized layer of a heat sink.
The present invention relates to a semiconductor device capable of sufficiently spreading a Sn solder material.

In recent years, TAB (Tape Automated Bonding)
Accordingly, a semiconductor device in which an LSI chip is connected face down and the connected LSI chip is sealed with a Pb-Sn brazing material by a cap and a heat radiating plate attracts attention. Specifically, this semiconductor device has a metallized layer composed of a Ni plating layer / Au plating layer (2 to 3 μm layer) formed on a cap and a Ti layer / Mo layer / Ni layer (sputtering) formed on a heat sink. / N
Adhesion with a metallized layer consisting of an i-plated layer / Au-plated layer (2 to 3 μm thick) was performed using a Pb-Sn brazing material. However, when bonding the cap and the heat sink using the Pb-Sn brazing material, on the surface of the Au plating layer constituting the metallized layer of the cap and the surface of the Au plating layer constituting the metallized layer of the heat sink.
There was a problem that the Pb-Sn brazing material did not sufficiently wet and spread, and it was difficult to obtain sufficient sealing airtightness.

For this reason, it is possible to obtain sufficient sealing airtightness by sufficiently wetting and spreading the Pb-Sn brazing material on the Au plating layer surface constituting the metallized layer of the cap and the Au plating layer constituting the metallized layer of the heat sink. There is a demand for a semiconductor device that can be used.

[Conventional technology]

FIG. 7 is a diagram showing a configuration of a conventional semiconductor device. The semiconductor device in the illustrated example is “Nikkei Micro Devices 1989
June issue P51 Figure 2 ”.

In this figure, 31 is a package made of ceramics such as AlN, 32 is an external lead, 33 is a Ti layer / Mo layer / Ni layer / Cr layer / Cu layer / Ni layer (or more sputter) / Seal pattern consisting of Ni plating layer / Au plating layer, etc., 34
Is, for example, a conductor pattern made of the same material as the seal pattern 33, 35 is an insulator cover made of polyimide resin or the like, 36 is an adhesive layer made of Pb-Sn brazing material, 37 is, for example, a TAB in which Sn plating is formed on copper foil. Leads, 38 are bumps made of Au or the like, 39 is a cap made of Kovar alloy or the like, 40 is a Ni plating layer / Au plating layer (2-3 μm) formed on the surface of the cap 39.
m), 41 is an LSI chip, 42 is an LSI
Ti layer / Au layer formed on the back of chip 41 (sputtered above)
43 is a heat sink made of ceramics such as AlN, 44 is a Ti layer / Mo formed on the lower surface of the heat sink 43
Layer / Ni layer (more than sputtering) / Ni plating layer / Au plating layer (2-3
metallization layer consisting μm thick) or the like, 45 denotes a gap, inert gas such as N ₂ gas is filled.

In the conventional semiconductor device, the LSI chip 41 is connected face-down to the package 31 by TAB so that the patterning surface of the LSI element or the like faces the package 31 side, and the LSI chip 41 connected to the package 31 is connected to the cap 39 and the heat sink. The sealing with 43 has been performed by using a Pb-Sn brazing material to be the adhesive layer 36. Specifically, this sealing is performed by bonding the seal pattern 33 formed on the package 31 and the metallized layer 40 formed on the cap 39 with a Pb-Sn brazing material serving as an adhesive layer 36, and forming the seal pattern 33 on the back surface of the LSI chip 41. The metallized layer 42 formed on the cap 39 and the metallized layer 42 formed on the cap 39 and the metallized layer 44 formed on the heat sink 43 are bonded to each other.
It was performed by bonding with a Pb-Sn brazing material which became 36.

Since the sealing is performed in an atmosphere of an inert gas such as N ₂ gas, the gap 45 around the sealed LSI chip 41 is filled with an inert gas. Also, the metallized layer 44 of the heat sink 43
As, a Ti layer, a Mo layer,
After successively forming a Ni layer, Ni is further plated on the Ni layer.
A plating layer and an Au plating layer (2 to 3 μm thick) are sequentially formed, and as the metallized layer 40 of the cap 39,
Ni plating layer, Au plating layer (2-
(Thickness: 3 μm).

[Problems to be solved by the invention]

In the conventional semiconductor device described above, the metallized layer 40 formed of the Ni plating layer / Au plating layer formed on the cap 39 and the Ti layer / Mo layer / Ni layer (or more sputtered) / Ni
Pb for bonding with metallized layer 44 consisting of plating layer / Au plating layer
-It was performed by Sn brazing material. However, when the cap 39 and the heat radiating plate 43 are bonded using the Pb-Sn brazing material, the Au plating layer surface forming the metallized layer 40 of the cap 39 and the Au plating layer forming the metallized layer 44 of the heat radiating plate 43 are bonded. Pb
-As shown in Fig. 8, the Sn brazing material does not sufficiently wet and spread.
Metallized layer 40 of cap 39 and metallized layer of heat sink 43
There is a problem that a gap 51 is generated between the 44 and a void is generated between the Au plating layer forming the metallized layers 40 and 44 and the adhesive layer 36 made of the Pb-Sn brazing material, and it is difficult to obtain sufficient sealing airtightness. there were. In addition, there is a problem that the heat radiating plate 43 that radiates heat from the cap 39 via the adhesive layer 36 made of the Pb-Sn brazing material has a poor heat radiation effect. If the sealing airtightness is not sufficient, H ₂ O, O _{2 and the} like of the outside air enter the gap 45 through the adhesive layer 36 made of the Pb-Sn brazing material and corrode the LSI chip 41 and the like, or However, if the heat radiation effect of the heat radiating plate 43 deteriorates, there is a problem that the junction temperature of the LSI chip 41 in actual use is increased and the life is shortened.

It is considered that the reason why the Pb-Sn brazing material does not sufficiently wet and spread on the surface of the gold plating is as follows.

The Ni plating layer formed only by plating, which constitutes the metallized layers 40 and 44, is not a dense film, the surface state is rough due to unevenness, and residues such as oxides are likely to remain on the surface, A gold plating layer is formed with the residue remaining.
Then, upon heating, the residue diffuses out onto the Ni plating layer on the Au plating layer surface. For this reason, it is considered that the Pb-Sn brazing material is difficult to sufficiently wet and spread on the surface of the gold plating layer.

Therefore, the present invention provides an Au plating layer surface constituting the metallized layer of the cap and an Au plate constituting the metallized layer of the heat sink.
The Pb-Sn brazing material can be spread sufficiently on the surface of the plating layer with almost no voids to improve the sealing airtightness and the heat dissipation effect of the heat sink, thereby improving the reliability of the LSI chip. It is an object of the present invention to provide a semiconductor device capable of performing the following.

[Means for solving the problem]

In order to achieve the above object, in the semiconductor device according to the present invention, a chip is connected face-down to a package, a seal pattern formed on the package and a metallized layer formed on a cap are bonded by a brazing material, and In a semiconductor device in which a formed metallized layer and a metallized layer formed on the cap and a metallized layer formed on a heat sink are bonded by a brazing material whose main component is Pb-Sn, the cap and the heat sink The metallized layer formed on the substrate is recrystallized to have a dense crystal grain and has a thickness of 0.5 μm or more and a nickel plating layer having a thickness of 0.2 μm or more and 1.0 μm or less. And a plating layer.

As forming method for obtaining nickel plating layer having been recrystallized dense grain according to the present invention, a Ni plating layer obtained by plating H ₂ gas or a reducing gas and N ₂ such as CO gas A method of performing heat treatment in a mixed gas with a gas or an inert gas such as a CO ₂ gas may be used. In this case, the Ni plating layer is preferably not oxidized, and a reducing gas may be used as described above.

In the present invention, the lower limit of the thickness of the nickel plating layer is 0.5
When the thickness is smaller than 0.5 μm, when heat treatment is performed to obtain a nickel plating layer having recrystallized and dense crystal grains, Ni is used as a base layer (for example, a Mo layer formed by sputtering). This is because they are almost diffused into the inside, which is not preferable for practical use.

In the present invention, the lower limit of the thickness of the gold-plated layer is set to 0.2 μm, when it is stored for a long time and becomes thinner than 0.2 μm, A
u Oxygen and moisture in the air penetrate through gaps in the film of the plating layer to cause oxidative deterioration of the metal film, and Ni or the like diffuses into the gold plating layer, resulting in oxygen and moisture in the air. This is because it reacts with the like and is oxidized and deteriorated, which is not preferable for practical use. Further, the upper limit of the thickness of the gold plating layer was set to 1.0 μm, when the thickness is more than 1.0 μm, when heating and melting the Pb-Sn brazing material, the amount of Au to be melted increases, and as a Pb-Sn brazing material This is because the melting point increases, and it becomes difficult to spread wet, which is not preferable for practical use. As shown in FIG. 6, the gold plating layer of the present invention in which the thickness of the gold plating layer is 0.2 μm or more and 0.1 μm or less has an outflow occurrence rate and a pulling-in occurrence rate which are both higher than those of other thicknesses. This shows a good value, indicating that the solder flowability is good.

In the present invention, the preferred weight component ratio of the Pb-Sn brazing material is 83% by weight or more of Pb and 17% by weight or less of Sn. In this case, since the solidus line and the liquidus line are close to each other, the solidification can be terminated quickly, which is preferable.

Examples of the brazing material containing Pb-Sn as a main component according to the present invention include a brazing material consisting only of Pb-Sn and a brazing material consisting of Ag-containing Pb-Sn.

[Action]

In the present invention, as shown in FIG. 1, FIG. 3, and FIG.
The Ni plating layers 8a, 4d constituting the metallized layers 8, 4 formed on the cap 39 and the heat sink 43, respectively, are
m (0.5 μm or more), so that it is recrystallized to have dense crystal grains, so that the surface condition is almost uniform with less unevenness than the conventional Ni plating layer formed only by plating alone. . Then, the film thickness is, for example, 0.5 μm (from 0.2 to 1.
0 μm or less) Au plating layers 8b and 4e were formed, so that the residue on the Ni plating layers 8a and 4d hardly diffused and appeared on the Au plating layers 8b and 4e during heating. The Pb-Sn brazing material can be sufficiently spread on the surfaces of the Au plating layers 8b and 4e with almost no voids.

〔Example〕

 Hereinafter, the present invention will be described with reference to the drawings.

1 to 5 are diagrams for explaining an embodiment of a semiconductor device according to the present invention. FIG. 1 is a diagram showing a configuration of a semiconductor device of one embodiment, and FIG. FIG. 3 is a view for explaining a method of manufacturing a Sn brazing material, FIG. 3 is a view for explaining a method of manufacturing a metallized layer of a heat sink of one embodiment, and FIG. 4 is a method of manufacturing a cap and a metallized layer of a cap according to one embodiment. FIG. 5 is a diagram for explaining a method of manufacturing a semiconductor device according to one embodiment.

In these figures, the same reference numerals as those in FIG. 7 denote the same or corresponding parts, 1 is a Pb ingot, 2 is a Sn ingot, 3 is, for example, Pb: Sn = 90% by weight: 10% by weight Pb-Sn brazing material, 4 is a Ti layer 4a / Mo layer 4b / Ni layer 4c / N formed on the heat sink 43
Metallized layer consisting of i-plated layer 4d / Au-plated layer 4e, 5 is rope material such as Kovar alloy (may be 42Alloy), 6 is drawing die, 7 is cutting die, and 8 is Ni plating formed on cap 39 The metallized layer 9 composed of the layer 8a / Au plating layer 8b and the film carrier 9 composed of a polyimide tape or the like formed on the TAB lead 37 so that the TAB lead 37 does not vary.

First, a method for manufacturing a Pb-Sn brazing material to be the adhesive layer 36 will be described with reference to FIG.

First, the high-purity Pb ingot 1 and the high-purity Sn ingot 2 are melted at, for example, Pb: Sn = 90% by weight: 10% by weight, and then cooled and crystallized to form a mass of the Pb-Sn brazing material 3. . Next, the mass of the Pb-Sn brazing material 3 is squeezed out into a bar shape, rolled into a sheet having a desired film thickness, and then punched or cut to form a Pb-Sn material having a desired shape.
The brazing material 3 can be obtained.

Next, a method of manufacturing the metallized layer 4 of the heat sink 43 will be described with reference to FIG.

Here, AlN ceramics is used for the heat sink 43, which has a large thermal conductivity of about 150 w / mK, excellent heat dissipation effect, and a thermal expansion coefficient of about 4 ppm / K and about 3 ppm of Si. This is because the load on the LSI chip 41 due to thermal stress is very small because it is very close to / K.

First, the film thickness is, for example, 0.
After sequentially forming a 1 μm Ti layer 4a, a Mo layer 4b having a film heat of, for example, 2 μm, and a Ni layer 4c having a film heat of, for example, 1 μm, the Ti layer is formed of AlN.
In order to improve the adhesion between the Ti layer 4a and the heat radiating plate 43 by diffusing it into the heat radiating plate 43 made of, for example, heat treatment is performed at 930 ° C. in a mixed gas of H ₂ gas and N ₂ gas. Here, the Ti layer 4a is formed to obtain the adhesion between the heat radiating plate 43 made of AlN and the Mo layer 4b, and the Mo layer 4b is formed so that the thermal expansion coefficient is about 4 ppm.
The heat expansion coefficient of the metallized layer 4 as a whole is determined by
The reason for forming the Ni layer 4c is to obtain close contact with the Ni plating layer 4d. Next, after forming a Ni plating layer 4d having a thickness of, for example, 2 μm on the Ni layer 4c by plating, the Ni plating layer 4d is recrystallized to have dense crystal grains, for example, at 720 ° C. Heat treatment is performed in a mixed gas of _two gases and N ₂ gas. Next, an Au plating layer 4e having a thickness of, for example, 0.5 μm is formed on the Ni plating layer 4d by plating, whereby a Ti layer 4a / Mo layer 4b / Ni layer 4c (or more sputtering) / Ni plating layer 4d / Au plating layer is formed. A metallized layer 4 made of 4e can be obtained.

Next, a method of manufacturing the cap 39 and the metallized layer 8 of the cap 39 will be described with reference to FIG.

First, a plate-shaped hoop material 5 such as a Kovar alloy (42Alloy or the like) is formed into a desired shape by a drawing die 6 and cut by a cutting die 7 into a desired size to form a cap 39. Next, after the cap 39 is degreased and cleaned, the Ni plating layer 8a having a thickness of, for example, 2 μm is formed on the surface of the cap 39 by plating.
Is formed, a heat treatment is performed, for example, in a H ₂ gas atmosphere at 720 ° C. in order to recrystallize the Ni plating layer 8a to have dense crystal grains. The heat treatment temperature here is 550 ° C
It is preferably at least 800 ° C. Then, an Au plating layer 8b having a thickness of, for example, 0.5 μm is formed on the Ni plating layer 8a by plating, whereby the metallized layer 8 composed of the Ni plating layer 8a / Au plating layer 8b can be obtained.

Next, a method of manufacturing a semiconductor device will be described using the Pb-Sn brazing material 3 formed as described above, the heat sink 43 on which the metallized layer 4 is formed, and the cap 39 on which the metallized layer 8 is formed.

First, as shown in FIGS. 5A and 5B, a bump 38 made of Au or the like formed on an LSI chip 41 and a TAB lead 37 reinforced by a film carrier 9 are bonded by heating and pressing. . Note that a metallized layer 42 of a Ti layer / Ni layer / Ag layer (sputtered) or the like is formed on the back surface of the LSI chip 41.

Next, as shown in FIG. 5C, the TAB lead 37 is cut to a predetermined length. At this time, the film carrier 9 reinforced so that the TAB leads 37 do not vary is removed.

Next, as shown in FIGS. 5D and 5E, the LSI chip 41 is connected to the package 31 by heating and pressing face-down so that the patterning surface of the LSI element or the like faces the package 31 side. At this time, the TAB lead 37 of the LSI chip 41 and the conductor pattern 34 of the package 31 are connected. The package 31 here has a Ti layer / Mo layer / Ni layer / Cr layer / Cu layer / N
A seal pattern 33 composed of an i-layer (more than sputtering) / Ni layer / Au layer (more than plated), a conductor pattern 34 made of the same material as that of the seal pattern 33, and an insulator cover made of polyimide resin or the like 35 and external leads 3 with Au plating on the pins of, for example, Kovar alloy
2 are formed.

Next, as shown in FIG. 5 (f), a frame-shaped Pb-Sn brazing material, a frame-shaped cap 39, a pellet-shaped Pb-Sn brazing material, and a heat sink 43 are sequentially placed. The surface of the cap 39 is Ni
A metallized layer 8 composed of a plating layer 8a / Au plating layer 8b is formed, and a Ti layer 4a / Mo layer 4b / Ni layer 4 (or more sputtered) c / Ni plating layer 4d / Au plating layer on the lower surface of the heat sink 43. A metallized layer 4 of 4e is formed.

Then, by heating (for example, 300 ° C.) and pressurizing (for example, 100 g / cm ² ) in an N ₂ gas atmosphere, the seal pattern 33 formed on the package 31 and the metallized layer 8 formed on the cap 39 are bonded to each other. The metallized layer 42 formed on the back surface of the LSI chip 41, the metallized layer 8 formed on the surface of the cap 39, and the metallized layer 4 formed on the lower surface of the heat sink 43 are bonded together with the Pb-Sn brazing material 3 serving as 36. Pb
The semiconductor device as shown in FIG. 1 is completed by bonding with the Sn solder material 3.

That is, in the above-described embodiment, first, the Ni that constitutes the metallized layers 8 and 4 formed on the cap 39 and the heat sink 43, respectively, is used.
The thickness of the plating layers 8a and 4d is, for example, 2 μm (0.5 μm or more)
And has fine crystal grains. For this reason, the surface condition is almost uniform with almost no irregularities as compared with the case of the conventional Ni plating layer formed only by single plating. Then, the film thickness is, for example, 0.5 μm (0.2 μm or more and 1.0 μm or less) with little residue such as oxide remaining on the surface.
m or less) Au plating layers 8b and 4e can be formed. Therefore, at the time of heating, the Ni plating layers 8a, 4d
Since the residue above hardly diffuses and appears, Au
The Pb-Sn brazing material can be sufficiently wet-spread on the surfaces of the plating layers 8b and 4e with almost no voids. Therefore, the sealing airtightness and the heat radiation effect of the heat radiation plate 43 can be improved, and the reliability of the LSI chip can be improved.

In this embodiment, the case where the Ti layer 4a, the Mo layer 4b, and the Ni layer 4c formed by the sputtering method are used as the base layer constituting the metallized layer 4 formed on the heat sink 43 has been described. The invention is not limited to this,
For example, a case in which a metal paste such as W or Mo is applied and baked may be used as a base layer.

〔The invention's effect〕

According to the present invention, constituting the metallized layer of the cap
The Pb-Sn brazing material spreads sufficiently on the surface of the Au plating layer and the surface of the Au plating layer, which constitutes the metallization layer of the heat sink, so that almost no voids occur, improving the sealing airtightness and the heat dissipation effect of the heat sink. And the reliability of the LSI chip can be improved.

[Brief description of the drawings]

1 to 5 are diagrams for explaining an embodiment of a semiconductor device according to the present invention. FIG. 1 is a diagram showing a configuration of a semiconductor device of one embodiment. FIG. 2 is a diagram showing Pb of one embodiment. FIG. 3 is a view for explaining a method for manufacturing a Sn brazing material, FIG. 3 is a view for explaining a method for manufacturing a metallized layer of a heat sink according to one embodiment, and FIG. 4 is a method for manufacturing a cap and a metallized layer for a cap according to one embodiment. FIG. 5 is a diagram illustrating a method of manufacturing a semiconductor device according to one embodiment; FIG. 6 is a diagram illustrating the effect of the present invention; FIG. 7 is a diagram illustrating a configuration of a conventional semiconductor device; FIG. 8 is a diagram for explaining the problem of the conventional example. 3 ... Pb-Sn brazing material, 4 ... metallized layer, 4d ... Ni plated layer, 4e ... Au plated layer, 8 ... metallized layer, 8a ... Ni plated layer, 8b ... Au plated layer, 31 …… Package, 33 …… Seal pattern, 39 …… Cap, 41 …… LSI chip, 42 …… Metalized layer, 43 …… Heat sink.

Claims (2)

(57) [Claims] 1. A chip (41) is connected face-down to a package (31), and a seal pattern (33) formed on the package (31) and a metallization layer (8) formed on a cap (39). Are bonded by a brazing material (3, 36), and a metallized layer (4) formed on the back surface of the chip (41) is formed.
2) and a metallized layer (8) formed on the cap (39) and a metallized layer (4) formed on the heat sink (43)
And a metallized layer (4, 8) formed on the cap (39) and the heat radiating plate (43) in a semiconductor device in which is bonded by a brazing material (3, 36) whose main component is Pb-Sn. Is recrystallized and has dense crystal grains. Nickel plating layer (4d, 8a) with a thickness of 0.5 μm or more.
And the film thickness formed on the nickel plating layers (4d, 8a) is 0.
A semiconductor device comprising a gold plating layer (4e, 8b) having a thickness of 2 μm or more and 1.0 μm or less. 2. The semiconductor device according to claim 1, wherein the weight component ratio of the Pb-Sn brazing material (3, 36) is such that Pb is 83% by weight or more and Sn is 17% by weight or less.