JPH07321412A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the quality of a soldered part from being changed due to heat generated when an element is operated by a method wherein a barrier metal layer which does not cause a fusion reaction with both a contact metal and a bonding metal at a soldering temperature by indium solder is inserted between a contact metal layer and a bonding metal layer. CONSTITUTION:Since the uppermost layer of an electrode 6, for substrate connection, which is formed on a semiconductor element 1 is covered with a bonding metal layer 5 which is easily fused with In solder, an oxide film is excluded to the periphery due to surface tension, and a good connection can be performed. In addition, a barrier metal layer 4 which does not cause a fusion reaction with both a contact metal and a bonding metal at a soldering temperature is interposed between a contact metal layer 3 such as gold or the like at the lowermost layer of the electrode 6 for substrate connection and the bonding metal layer 5 at the uppermost layer. As a result, the contact metal is not fused into the In solder due to a temperature rise by heat generated in an operation, it is possible to prevent the plasticity of In from being degraded and the resistance of the In from being increased, and the relaibility of a semiconductor device is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a structure of a II-VI group compound semiconductor laser or the like in which a semiconductor element is soldered and connected to a mounting substrate using indium solder.

In a semiconductor element such as a II-VI compound semiconductor laser, which is liable to deteriorate in characteristics under high temperature conditions, the semiconductor element is mounted on a mounting substrate made of a heat radiator with solder having thermal conductivity, etc. Although the heat generated in the element is dissipated in the semiconductor element to suppress the temperature rise of the semiconductor element, when the semiconductor element is mounted on the radiator substrate by soldering, it has a structure with good heat dissipation and the active layer of the element is A soft material that does not cause distortion and a low resistance connection that does not generate heat are required.

[0003]

2. Description of the Related Art For example, in the case of a ZnSe (zinc selenium) -based compound semiconductor which is a material for a II-VI group compound semiconductor laser which is a blue laser, the crystal growth temperature is 250.
It has a low temperature of ℃, and increases the resistance when heated to 300 ℃ or more, and because the crystal is softer than the III-V group compound semiconductor, it is likely to be distorted after connection. The material that can be used is about 156 ℃
It has a low melting point and is limited to soft indium (In).

In the conventional semiconductor laser, in order to dissipate heat from the element, the electrode (contact metal layer) of the laser element is directly formed on the radiator substrate (heat sink) at a temperature of about 200 ° C. using the In solder. It was formed in a structure that was connected by soldering.

[0005]

However, In is a metal which is very easily oxidized, and an oxide film is immediately formed on the surface in the atmosphere. Once this oxide film is formed, at a soldering temperature of about 200 ° C., only In melts and the oxide film on the surface remains unmelted. Gold (A) which is often used as an electrode (contact metal layer)
Since it is sandwiched between the metal layer such as u) and the In solder, the wettability between the electrode and the In solder is impaired, resulting in poor connection and increased resistance. Further, in order to avoid this connection failure, high temperature heating of about 400 ° C. is required to dissolve the oxide film into In, and this cannot be performed because the device performance is deteriorated.

Therefore, in order to avoid the above problem, a bonding metal layer which is easy to fuse with In solder such as In or tin (Sn) is formed in advance on the uppermost part of the entire surface of the electrode composed of the contact metal layer of the laser element. You need to do it. With this configuration, when the bonding metal layer and the In solder are fused, the In oxide film is pushed out to the outer surface of the soldered portion, and good solder connection with good wettability can be achieved.

However, here, II-VI such as ZnSe system is used.
In group III compound semiconductor lasers, the contact material on the active layer side is usually Au, Au / Pd (palladium), A
The following problems arise due to the use of Au-based contact metals such as u / Pt (platinum) / Pd.

That is, Au contained in the contact metal
And In used for solder easily react with each other at a low temperature, and particularly when the temperature rises when the laser is energized
Au melts into the solder and hardens the soldered part to give strain to the active layer, or increases the resistance of the soldered part, causing deterioration in the characteristics of the laser with time and its reliability. It is a problem that damages.

Therefore, in the present invention, the electrode of the semiconductor element is In
An object of the present invention is to provide a structure of an electrode for connecting a substrate of a semiconductor element in a semiconductor device which is soldered on a mounting substrate using solder and which prevents deterioration of an element soldering portion due to heat generation during operation of the semiconductor element. .

[0010]

To solve the above-mentioned problems, a semiconductor device in which a semiconductor element is soldered and connected to a mounting board using indium solder is used. The electrode for use has a contact metal layer for ohmic connection to the semiconductor element in the lowermost layer and a bonding metal layer made of a metal that easily fuses with indium solder in the uppermost layer, and the contact metal layer and the bonding metal layer. The semiconductor device according to the present invention has a structure in which a barrier metal layer that does not cause a fusion reaction with either the contact metal or the bonding metal at the soldering temperature with the indium solder is inserted between the two.

[0011]

FIG. 1 is a perspective view for explaining the principle of the present invention.
Reference numeral 1 is a semiconductor element (chip), 2 is a mounting substrate (for example, a radiator), 3 is a contact metal layer made of gold or gold alloy, 4 is a barrier metal layer, and 5 is a bonding metal layer made of In, Sn or the like. , 6 is a substrate connecting electrode, and 7 is I
n solder is shown.

As shown in FIG. 1A, a semiconductor element (chip) 1 used in the construction of a semiconductor device according to the present invention has a contact metal layer 3 which is ohmic-connected to the semiconductor element 1.
In the lowermost layer directly contacting the semiconductor element, and In in the uppermost layer.
It has a bonding metal layer 5 made of, for example, In, Sn or the like which is easily fused with solder, and the contact metal layer 3 and the bonding metal layer are provided between the contact metal layer 3 and the bonding metal layer 5 at a soldering temperature. 5 is provided with a substrate connecting electrode 6 in which a barrier metal layer 4 that does not cause a fusion reaction is inserted.

Then, as shown in FIG. 1 (b), the semiconductor element 1 is mounted on a mounting substrate 2 composed of a heat radiator or the like with the In solder 7 being in contact with the substrate connecting electrode 6 through the In solder 7. Then, the temperature is raised to melt the In solder 7 (in this case, I
n solder 7 and bonding metal layer 5 are integrated),
As shown in FIG. 1 (c), it has a structure in which a semiconductor element 1 is soldered and connected onto a mounting substrate 2. Here, after the mounting substrate 2 having the In solder 7 mounted thereon is heated to melt the In solder 7, the device 1 is mounted on the molten In solder 7 to bond the bonding metal layer 5 of the device 1.
It may be soldered by melting and integrating with the melted In solder 7.

In the present invention, since the uppermost layer of the substrate connecting electrode 6 provided on the semiconductor element 1 is covered with the bonding metal layer 5 which easily fuses with the In solder, even if the surface and the surface of the In solder 7 are oxidized. Even if a film is formed, the oxide film is eliminated to the periphery by surface tension when the In solder 7 and the bonding metal layer 5 are fused.
Good electrical and mechanical connections are made.

Further, between the lowermost contact metal layer 3 made of gold or gold alloy of the substrate connecting electrode 6 and the uppermost bonding metal layer 5 at the soldering temperature, either contact metal or bonding metal is used. In addition, since the barrier metal layer 4 that does not cause a fusion reaction is interposed, the contact metal does not melt into the In solder due to the temperature rise during heat generation during soldering or during operation after completion of the device. Deterioration of plasticity (hardening) and increase of resistance are prevented, and reliability of the semiconductor device mounted on the mounting substrate is improved by the In solder.

[0016]

EXAMPLES The present invention will be specifically described below with reference to an example of a ZnSe based semiconductor laser using a gold based contact metal with reference to the perspective schematic view of FIG. 2 and the manufacturing process sectional view of FIG. To do.

The laser element 11 used in the ZnSe semiconductor laser according to the present invention is, as shown in FIG. 2 (a), an n-type zinc-sulfur-selenium substrate on an n ⁺ -type gallium arsenide (GaAs) substrate 11a as usual. (ZnSSe) clad layer
11b, an n-type ZnSe light guide layer 11c, a cadmium zinc selenium (CdZnSe) active layer 11d, a p-type ZnSe light guide layer 11e, a p-type ZnSSe cladding layer 11f, and a striped p-type ZnSe contact layer 11g are sequentially stacked,
The step portions on both sides of the striped p-type ZnSe contact layer 11g are evenly filled with an insulating layer 18 such as polyimide, and the striped p-type ZnSe contact layer 11g near the active layer 11d and the step portions on both sides thereof are filled. On the insulating layer 18, for example, Au, which is ohmic-connected to the p-type ZnSe contact layer 11g and extends to the insulating layers 18 on both sides,
An Au-based contact metal layer 13 having a thickness of about 3000 Å such as Au / Pd or Au / Pt / Pd, and a barrier nickel (N) having a thickness of about 500 Å or more laminated thereon.
i) Layer 14 and further laminated thereon, for example 3 μm thick
A substrate connecting electrode 16 according to the present invention is formed of a bonding In layer 15 to a certain extent, and a conventional n electrode 19 of an In layer is formed on the lower surface of the GaAs substrate 11a.

In the ZnSe based semiconductor laser according to the present invention, as shown in FIG. 2B, a thickness of 3 μm having a plane shape substantially equal to that of the laser element 11 is provided at a predetermined position on the heat sink 12. About In Solder 17
Is placed in advance, the heat sink 12 is heated to a soldering temperature of about 200 ° C. to melt the In solder 17, and then the laser element 11 is mounted on the heat sink 12 so that the entire surface of the substrate connecting electrode 16 is It is mounted so as to be in contact with the In solder 17, and as shown in FIG. 2C, the bonding metal layer 15 made of In, which is the uppermost layer of the substrate connecting electrode 16 of the laser element 11, and the In solder 17 are mounted. The laser element 11 and the heat sink 12 are connected by fusion and integration.

In the ZnSe based semiconductor laser of the above embodiment, the uppermost layer of the substrate connecting electrode 16 of the laser element 11 is I.
It is formed of a bonding In layer 14 that easily fuses with the n solder 17, and the In solder 17 and the bonding In layer 14 are fused and integrated during soldering. At that time, the bonding In layer 14 and the In solder The oxide film formed on the surface of 17 is removed to the periphery by surface tension,
Good electrical and mechanical connections are made.

Further, between the lowermost gold-based contact metal layer 13 which is in direct contact with the element of the substrate connecting electrode 16 and the uppermost bonding In layer 14, a barrier Ni layer which does not fuse with any metal is provided. Since 14 is interposed, a contact metal layer is formed in the In solder 17 during the above soldering.
The 13 gold-based metals do not melt, and the plasticity of the soldered part is kept sufficiently soft. Therefore, the active layer 11d of the laser element 11 is not distorted by soldering, and the stress caused by the difference in the thermal expansion coefficient between the laser element 11 and the heat sink 12 due to the heat generation of the laser element 11 during the laser operation also causes the plasticity. Sufficiently absorbed by the soldering portion of the active layer 11d, the active layer 11d is not stressed and distorted during operation.

As described above, Zn according to the above embodiment
In the Se-based semiconductor laser, the active layer is not distorted due to the temperature rise during solder connection of the laser element to the heat sink and during operation, and the electrical connection between the laser element and the heat sink and the heat generated thereby Since the conductive connection is sufficiently maintained, deterioration of characteristics over time is prevented and reliability is improved.

Hereinafter, the present invention will be described in more detail with reference to the process cross-sectional views of FIGS. 3A and 3B regarding the method of manufacturing the above ZnSe based semiconductor laser. See FIG. 3 (a). An n-type ZnSSe cladding layer is formed on the n ⁺ -type GaAs substrate 11a by, for example, molecular beam epitaxial (MBE) growth method.
11b, n-type ZnSe light guide layer 11c, CdZnSe active layer 11d, p-type ZnSe light guide layer 11e, p-type ZnSSe
A clad layer 11f and a p-type ZnSe contact layer 11g are sequentially grown.

Next, referring to FIG. 3B, the p-type ZnSe contact layer 11g is patterned into a stripe pattern having a predetermined width. Ordinary photolithography is used for patterning, and wet etching using a bromine (Br) -based etchant is mainly used for etching.

Next, an insulating film 18 made of, for example, CVD-SiO ₂ is deposited on the upper surface of the laminated substrate to a thickness that completely fills the p-type ZnSe contact layer 11g patterned in the stripe shape.

Next, as shown in FIG. 3C, a groove for selectively exposing the upper surface of the p-type ZnSe contact layer 11g is formed in the insulating film 18 by, for example, a dry etching method, and then Au, Au is formed on the laminated substrate. / P
d, Au / Pt / Pd, etc., with a thickness of about 3000Å, a gold-based contact metal layer 13, and a thickness of about 500Å, a Ni layer for barrier.
14 and a bonding In layer 15 having a thickness of about 3 μm are sequentially formed by vapor deposition means. Here, the substrate mounting electrode 16 which is the p electrode of the laser element is completed.

Next, as shown in FIG. 3D, an n electrode 19 made of In and having a thickness of about 3 μm is formed on the back surface of the n ⁺ type GaAs substrate 11a by vapor deposition means.

Next, referring to FIG. 3 (e), the above-mentioned laminated substrate is diced into chips to obtain Zn.
The Se-based laser element 11 is formed.

On the other hand, the In solder 17 having a thickness of about 3 μm is previously formed on the heat sink 12 at the position where the laser element is mounted.

3 (g), the heat sink 12 is heated to a temperature not lower than the melting point of In (156 ° C.) and not higher than the crystal growth temperature by MBE (250 ° C.), for example, 200 ° C., and the In solder 17 is melted. After confirming that the completed ZnS
The e-type laser element 11 is aligned and mounted so that the substrate connecting electrode 16 is in contact with the In solder 17.

Referring to FIG. 3 (h), the bonding In layer 15 of the substrate connecting electrode 16 is melted and integrated with the In solder 17, and then cooled to cause the laser element 11 to be placed on the heat sink 12 so that the In solder 17 is formed. The ZnSe based semiconductor laser according to the present invention connected by the above is completed.

In the above connection, molten In solder 17
Since the bonding In layer 15 and the bonding In layer 15 are integrated and connected to each other, the In solder 17 and the bonding In layer 15 are formed.
The oxide film formed on the surface of the is removed at the periphery due to surface tension during fusion, and the fused connection portion has a good connection structure with no oxide film interposed. Therefore, a sufficiently low connection resistance can be obtained.

Further, between the lowermost Au-based contact metal layer 13 of the substrate connecting electrode 16 provided on the laser element 11 and the uppermost bonding In layer 15, a fusion reaction occurs with any metal at the soldering temperature. N for barrier that does not cause
Since the i layer 14 is interposed, the Au-based contact metal dissolves in the In solder 17 at the time of the soldering, and the In solder 17 is hardened (the plasticity is lost).
There is no such thing. The same applies to the temperature rise due to heat generation during laser operation.

In the above embodiments, the In layer is used as the bonding metal layer formed on the uppermost layer of the substrate connecting electrode of the semiconductor element (laser element) according to the present invention. This bonding metal layer is fused with In solder. The metal is not limited to In as long as it is an easy metal, and Sn or the like may be used. Further, as the barrier metal, other than Ni shown in the examples,
Refractory metals such as manganese (Mn) and chromium (Cr) are used.

[0034]

As described above, according to the present invention, in a semiconductor device such as a semiconductor laser in which a semiconductor element such as a laser element is connected to a mounting substrate such as a heat sink using In solder, the above-mentioned connection is sufficiently performed. It can be performed with a very low connection resistance and while maintaining the soft plasticity of the In solder.

Therefore, the stress caused by the difference in the coefficient of thermal expansion between the semiconductor element such as the laser element and the mounting substrate during the temperature rise due to soldering and the temperature rise due to the element operation is absorbed by the soft plasticity of the In solder, Strain is not applied to the active layer of the semiconductor element. Therefore, according to the present invention, the characteristic deterioration due to the crystal strain of the active layer is prevented, and the electrical connection with the mounting substrate is formed sufficiently low, so that the semiconductor substrate such as the semiconductor laser is mounted on the mounting substrate such as the heat sink. The reliability of a semiconductor device such as a semiconductor laser in which elements are connected using In solder is improved.

[Brief description of drawings]

FIG. 1 is a perspective view for explaining the principle of the present invention.

FIG. 2 is a schematic perspective view of an embodiment of the present invention.

FIG. 3 is a sectional view of a manufacturing process according to an embodiment of the present invention.

[Explanation of symbols]

1 Semiconductor Element 2 Mounting Substrate 3 Contact Metal Layer 4 Barrier Metal Layer 5 Bonding Metal Layer 6 Substrate Connecting Electrode 7 In Solder 11 ZnSe Semiconductor Laser Element 11a n ⁺ Type GaAs Substrate 11b n Type ZnSSe Clad Layer 11c n Type ZnSe Optical Guide Layer 11d CdZnSe active layer 11e p-type ZnSe optical guide layer 11f p-type ZnSSe clad layer 11g p-type ZnSe contact layer 12 heat sink 13 Au-based contact metal layer 14 Ni layer for barrier 15 In layer for bonding 16 substrate connection electrode 17 In solder 18 Insulation layer 19 n-electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akito Kuramata 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Kazuhiko Horino 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (5)

[Claims] 1. An indium solder (7) for a semiconductor element (1)
In a semiconductor device formed by soldering connection on a mounting substrate (2) using, the substrate connecting electrode (6) of the semiconductor element (1) used for the soldering connection has the semiconductor element ( Contact metal layer for ohmic connection to (1) (3)
And a bonding metal layer (5) made of a metal that is easy to fuse with the indium solder (7) and has between the contact metal layer (3) and the bonding metal layer (5). A semiconductor device having a structure in which a barrier metal layer (4) that does not cause a fusion reaction with either the contact metal or the bonding metal at the soldering temperature according to (7) is inserted. 2. The semiconductor device according to claim 1, wherein the bonding metal layer is made of indium or tin. 3. The semiconductor device according to claim 1, wherein the barrier layer is made of nickel or manganese. 4. The semiconductor device according to claim 1, wherein the contact metal layer is made of a conductive material containing gold. 5. The semiconductor device according to claim 1, wherein the semiconductor element is a II-VI group compound semiconductor laser element.