JPS5952853A - Semiconductor device - Google Patents

Abstract

PURPOSE:To reduce thermal strain applied to the end section of a solder layer, and to prevent the deformation and thermal fatigue breakdown of each member by forming a notch section or a recessed section to at least one of the fringe sections of the surfaces of a semiconductor base body and an insulating member and the surface section of a metallic member opposite to the fringe sections. CONSTITUTION:A metallic support member 11 is formed by a copper plate, and the recessed section 28 of 3mm. width X 0.5mm. depth is formed to a section opposite to the fringe section of the insulating member 12 placed in the upper surface of the member 11. The insulating members 12 consisting of two alumina plates are bonded by the solder layers 29 while being conformed to the positions of the recessed sections 28 of the metallic support member 11, and metallic plates 13 are bonded on each insulating member 12 by the solder layers 30. Sections opposite to the solder layers 29, 30 of the insulating members 12 are metallized. The metallic plate 13 is formed by a copper plate in 2mm. thickness, and the notch section 31 of 3mm. width X 0.5mm. depth is formed to the fringe section of the lower surface of the plate 13 and the recessed sections 28 of 1.5mm. width X0.5mm. depth to sections opposite to the fringe sections of semiconductor base bodies 14, 15, 16 placed on the upper surface of the plate 13 by a press.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device, and more particularly to an insulated semiconductor device having a structure in which a semiconductor substrate is mounted on an insulating member via a metal plate.

In the past, most semiconductor devices were formed by placing a semiconductor substrate on a support member made of metal that also served as electrodes and heat conduction paths, but in recent years, the degree of freedom in circuit application of semiconductor devices has been improved. For this reason, or to improve the v-product ratio of an electric circuit, an insulated semiconductor device has been devised in which each semiconductor substrate or circuit is mounted on the same support member via an insulating member.

For example, an insulated triac has a bidirectional three-terminal thyristor base mounted on a ceramic plate, and this ceramic plate is enclosed in a metal package, and all electrodes of the triac are insulated from the package by the ceramic plate. It has a structure that is drawn out to the outside. Such isolated triacs can be used in circuits where the pair of main electrodes must be electrically isolated from the ground potential on the circuit, since the package can be fixed directly to the ground potential. The freedom of application is improved.

In addition, hybrid integrated circuit devices or semiconductor module devices (
A crystalline IC (hereinafter collectively referred to as a crystallized IC) is generally formed from a unified electric circuit made up of a plurality of semiconductor elements and the like. It may be necessary to electrically insulate at least a part of those circuits from metal members such as support members or heat dissipation parts.
Insulation is achieved by providing an organic or inorganic insulating layer between the C substrate and the substrate. The hybrid IC formed in this manner is also an insulated semiconductor device.

In the above-mentioned insulated semiconductor device, heat generated during operation of the semiconductor element is conducted from the semiconductor substrate to the support member via the adhesive layer and the insulating layer, and is mainly radiated from the support member to the air. That will happen. If this heat dissipation is not effective, problems such as unstable operation of the semiconductor device will occur, so it is necessary to have high heat dissipation performance. Furthermore, it must have high insulation properties in order to increase the circuit voltage or to improve reliability such as stability over time, moisture resistance, and heat resistance of the semiconductor device.

In particular, in semiconductor devices that generate a relatively large amount of heat and are required to have high withstand voltage and high reliability, it is necessary to use inorganic materials such as ceramics for the insulating layer to fully satisfy the above requirements. The material is PB-S without adhesive.
A gold layer solder such as n-based solder is applied.

Additionally, in general, in an insulated semiconductor device, the semiconductor substrate is not placed directly on the insulating layer, but rather as a conductive path connecting the semiconductor substrate to an external power source and a heat conduction path that effectively transfers heat generated in the semiconductor substrate to the insulating layer. Attached via metal plate. As this metal plate, a material such as copper, which has low resistance and high thermal conductivity, is generally used.

However, while the thermal expansion coefficient of copper is 18X10''/C, for example, the thermal expansion coefficients of silicon for the semiconductor substrate and alumina ceramic for the insulating layer are each 3.5X10'''6.
7C and 6.3 x 10-'/C, and since the difference in their thermal expansion coefficients is very large, the following problems may occur.

That is, the soldering process of the above-mentioned insulated semiconductor device usually involves laminating an insulating layer, a metal plate, and a semiconductor substrate through a solder layer, and then raising the temperature to a temperature higher than the melting point of the solder. Next, it is cooled to room temperature and bonded. During this cooling process, these members are fixed to each other near the solder freezing point temperature.

When this fixed state is further cooled to room temperature,
Since each member contracts according to its own coefficient of thermal expansion, thermal strain remains in the solder joint. If this thermal strain is small, it will be absorbed by the deformation of the solder layer of the component, but if the thermal strain is large, it will not be fully absorbed and shrinkage stress will act on the semiconductor substrate and insulating layer, deforming the semiconductor substrate. There is a risk that the electrical characteristics may be damaged, and furthermore, the semiconductor substrate or the alumina ceramic plate may be mechanically damaged.

In addition, each member of the insulated semiconductor device described above is repeatedly exposed to high temperatures (approximately 100 to 15
0C) and low temperature (ambient temperature). During each such heat cycle, each member is expanded and contracted, and as described above, distortion due to thermal stress is mainly applied to the solder layer due to the difference in the coefficient of thermal expansion of each member. Therefore, the solder layer is periodically compressed and stretched by this strain, and eventually becomes brittle and cracks due to thermal fatigue phenomenon, which may cause a decrease in the contact strength, electrical conductivity, and thermal conductivity of the solder layer. There was that. This phenomenon is particularly noticeable at the exposed end face portions of the solder layer.

The above-mentioned problem is caused by the difference in the coefficient of thermal expansion of each member, so the metal plate is made of a material whose coefficient of thermal expansion is relatively similar to that of the semiconductor substrate or insulating member (for example, molybdenum or tungsten). For example, it has been proposed to solve the problem by applying a metal plate made of an inexpensive material such as copper that has low resistance and good thermal conductivity.
A device in which a molybdenum piece is interposed between the semiconductor substrate and the semiconductor substrate is known. According to this, thermal stress acting on the semiconductor substrate due to the difference in thermal expansion between the semiconductor substrate and the copper plate can be alleviated, and deterioration of the semiconductor substrate can be prevented. but,
Since it is not possible to absorb thermal stress due to the difference in thermal expansion between an insulating member such as an alumina ceramic plate and a copper plate, soldering has no effect on preventing deformation over time or thermal fatigue caused by heat cycles. Moreover, it has the drawback that molybdenum pieces and solder layers, which have poor thermal conductivity, are extra interposed, and the transient heat dissipation effect of the semiconductor substrate is particularly deteriorated. From a point of view, this method has the drawback of increasing the number of parts and the number of wax parts, leading to an increase in cost.

An object of the present invention is to provide an insulated semiconductor device that can reduce thermal strain during manufacturing and operation, and prevent deformation and thermal fatigue damage of each member.

The present invention was developed in view of the phenomenon that thermal fatigue failure of a solder layer made of metal solder etc. occurs and grows from the peripheral edge of the solder layer. a peripheral edge of the surface of the base and the insulating member;
By forming a notch or a recess on at least one side of the surface of the metal member facing the peripheral edge so as to increase the thickness of the end of the solder layer, thermal strain applied to the end of the solder layer can be reduced. This aims to reduce deformation and thermal fatigue failure of each member.

Hereinafter, the present invention will be explained in more detail using illustrated embodiments.

FIG. 1 shows a 1.5 KVA of an embodiment to which the present invention is applied.
2 is a perspective view of a main part of the hybrid IC for class current control, and FIG. 2 shows a circuit configuration diagram of the embodiment shown in FIG. 1.

As shown in FIG. 1, a support member 1 made of a metal member
Two insulating members 12 made of alumina plates are fixed to the upper surface of the insulating member 1 by solder. On the insulating member 12, metal plates 13 having substantially the same shape are fixed to each other with metal solder. The circuit shown in FIG. 2 is formed on this metal plate 13, and Darlington-connected transistors 14
and 15, flywheel diodes 16 are directly brazed onto the metal plate 13, respectively. Further, a snubber chip capacitor 17 and a chip resistor 18 connected in series with the snubber chip capacitor 17 are mounted.

Wiring wires 19 or strips 20 are connected between each of the above circuit elements.
, are connected by a wiring metal piece 21 as shown in the circuit configuration diagram shown in FIG. The external terminal 22 is a metal plate 13
The external terminal 23 is connected directly to the top via the wiring metal piece 21.
The external terminals 24 are connected to each other via an insulating organic resin film 25 and a wiring metal piece 21 connected thereon. At the end of the metal plate 13 opposite to these external terminals, a terminal 27 connected to the driver circuit 26 is provided on the wiring metal piece 21 bonded onto the insulating organic resin film 25.

In this way, a plurality of semiconductor bodies (transistors 14.1
5 and a diode 16) are directly soldered onto the same metal plate 13 to form a hybrid IC. A cross-sectional view of the bonded portion between the metal plate 13, the insulating member 12, and the supporting member 11 of the embodiment formed in this way is shown in FIG.

In FIG. 3, the metal support member 11 has a thickness of 3.2 r
It is formed from a copper plate with a width of 61mm x a length of 105mm, and on the upper surface thereof, a width of 31III+ x a depth of 0 is provided on the part facing the peripheral edge of the insulating member 12 to be placed.
A concave portion 28 of 5 ran is formed.

Matching the position of the recess 28 of this metal support member 11,
Two alumina plate insulating members 12 are bonded to a lead-60% tin solder layer 29. The thickness of the center portion of the solder layer 29 is approximately 0.1 mm, and the thickness of the end portion where the recessed portion 28 is formed is approximately 0.6 t+m. The bonding surface of the insulating member 12 is subjected to a well-known metallization process to impart wettability to solder. The insulating member 12 has a width of 28 mm.
It is an alumina plate formed with a length of 33 m and a thickness of 0.6 mm.

A metal plate 13 is placed on each insulating member 12, and a solder layer 30 is placed on top of each insulating member 12.
It is glued well. This solder layer 30 has the same composition and the same thickness as the solder layer 29. Insulating member 1
The portion facing the solder layer 3o of No. 2 is subjected to metallization treatment as described above.

The metal plate 13 is formed from a copper plate with a thickness of 2 mm, and has a notch 31 with a width of 3 mm and a depth of 0.5 mm on the peripheral edge of its lower surface, and a semiconductor to be placed on the upper surface. Base 14, 15
．． 1.5 rtrm width in the part opposite to the peripheral edge of 16
Four portions 28 having an X depth of 0.5 mm are formed by pressing. On each metal plate 13 are semiconductor substrates 14 and 15.
．． 16 (area 8m x 8mm, thickness 0.25 rran
), but the thickness of the center part of the solder layer 32 is about 0.1 m, and the thickness of the end part where the four parts 28 are formed is about 0.6 m. Note that the composition of the solder layer 32 is the same as that of the solder layer 29.
It is the same as 30.

Because of this structure, the thickness of the solder layer end, which is the starting point for the occurrence of tab thermal fatigue, is formed sufficiently thick, so during the manufacture and operation of hybrid ICs, the solder layer end has a sufficient thickness. The thermal stress that occurs can be sufficiently alleviated,
This can effectively prevent the occurrence of thermal strain and thermal fatigue.

Therefore, in an insulated semiconductor device with a conventional structure, that is, a metal plate such as copper and a piece of molybdenum are bonded to an insulating member by solder, and a semiconductor substrate is bonded to the molybdenum piece by solder. However, according to this example, each member can be easily removed without impairing the heat dissipation effect. This has the effect of absorbing the thermal strain caused by the solder layer by the solder layer, and alleviating the thermal stress at the end of the solder M, thereby preventing thermal fatigue fracture.

In particular, the above-mentioned effect becomes remarkable in large-sized hybrid IC semiconductor devices. In other words, in large hybrid ICs, the amount of heat generated is high, and a large number of large-area semiconductor substrates are mounted, so the metal plate that functions as a heat diffusion plate must necessarily have a large area. Therefore, the influence of the difference in thermal expansion was an extremely large obstacle. Regarding this,
The heat cycle test shown in FIGS. 4 and 5 is -
55tl: '4-Jp1500 was used as one cycle, and the test was carried out under the conditions of 150 consecutive cycles.

In the figure, curve B shows the above-mentioned conventional hybrid IC. As shown in the figure, A is applied until the area Sr on the insulating part side (alumina plate) is approximately 500 mm''.

The failure rate F for both B was 0%. However, about 50
When it exceeds 0 mm2, the failure rate increases at an accelerating rate in B, while it is still 0% in A. In addition,
Here, for one reason; ++ means that cracks or partial peeling occurred in the raw solder layer.

Also, in Figure 4, 8! is less than 500m',
Although the above failure did not occur, when we measured the deformation of the metal support member, we found that the height of warpage in the longitudinal direction of this example was approximately 20 μm, while that of the conventional example was approximately 20 μm. It was also in the order of 0.33 to 1.5. This means that
It causes a gap between the metal support member and the frame or storage made of epoxy resin, etc., which impedes the sealing performance of the semiconductor device and, in turn, causes a problem in terms of moisture resistance. . However, since the deformation of the present embodiment is small, the above-mentioned risk does not occur at all.

The horizontal axis of FIG. 5 shows the area Ss of one semiconductor substrate, and the vertical axis shows the failure rate F2 of the hybrid IC. Heat cycle test conditions and symbols A and B attached to the curves in the figure
is the same as in FIG. However, the hybrid IC with the conventional structure used in the experiment does not include a molybdenum piece.

As shown in the diagram, A, B until the area S@ is about 25mm2
The failure rate F2 was 0% in both cases, but when it exceeded about 25H2, the failure rate increased rapidly in case B, whereas it was still at a level close to 0% in case A. The failure here refers to cracking or partial peeling of the solder layer between the semiconductor substrate and the metal plate (thermal diffusion plate).

In the above embodiment, each solder layer is 29° 30°.
320 Metal support member 11 as a means for absorbing thermal strain
A notch 31 and a four part 28 are provided in the metal plate 13. It is preferable to provide all of these thermal strain absorbing means from the standpoint of improving reliability, but from a design perspective, it is only necessary to provide the necessary thermal strain absorbing means depending on the conditions. Needless to say. For example, if the main focus is only on the reliability of the solders J@30 and 32, it is possible to omit the recess 28 of the metal support member 11, and in this case, the metal is thick enough to sufficiently reduce warpage. It is desirable to use it as a support member.

Further, the thermal strain absorbing means formed on the metal member of the metal support member 11 or the metal plate 13 can be formed by a sandblasting method, a cutting method, an etching method, in addition to the pressing method described in the above embodiment.
Although it may be provided by a polishing method or the like, a pressing method is most advantageous from the viewpoint of mass productivity. It goes without saying that this thermal strain absorbing means is not limited to a metal member, and the same effect can be obtained even if it is formed on the corresponding insulating member 12 or semiconductor substrate 14, 15, 16.

FIG. 6 shows a sectional view of the main parts of another practical example to which the present invention is applied.

In FIG. 6, the support member 34 is made of alumina ceramic, and a heat radiation fin 34a is provided on the lower surface of the support member 34.
A metal layer 35 made of four films, such as nickel or copper, is provided on the upper surface. The metal plate 13 is bonded to the upper surface of this metal layer 35 with solder 1-30. On the upper surface of this metal plate 13, there is a hybrid IC, similar to the embodiment shown in FIG.
Although circuits and the like are assembled, they are omitted in this figure to simplify the explanation. The support member 34 is an alumina plate with a width of 25 mm and a length of 30 mm, and the solder layer 30 is made of lead.
The metal plate 13 made of 5% tin-1.5% silver solder is a copper plate with a width of 22 m and a length of 27 m, and a notch 31 is formed in the metal plate 13 by pressing. Still solder layer 3
The thickness of the center portion of the 0.0 mm is 0.1 mm, and the thickness of the cutout portion 38 is between 0.6 mm.

With this structure, since the support member 34 also has the function of an insulating member, in addition to the effect of the embodiment shown in FIG. 3, the structure can be simplified.

Although the present invention has been described above based on two embodiments, the present invention is not limited to these embodiments, and includes, for example, the following embodiments.

First, the material of the metal plate is nickel, zinc, etc. instead of copper plate.
Metals with excellent electrical conductivity and thermal conductivity, such as aluminum, gold, silver, palladium, etc., or alloys containing these as main components can be used. In addition, the shapes of the four parts and notches formed in the metal plate etc. are shown in Figures 7(a) to (d) and 8, respectively.
Recesses 28 and cutouts 3 shown in figures (a) to (d)
It can be applied selectively from the 1st class.

As the inorganic insulating material, in addition to alumina, aluminum nitride (AtN), silicon nitride (Si3N4), beryllium oxide (Bed), silicon carbide (SiC), etc., or mixtures or sintered bodies containing these components can be used. It is.

In addition to the composition of lead-60% tin, for example, lead-60% tin can be used as the solder.
Those containing 5% tin or those containing silver, indium, etc. as a third component can be used. Its thickness is also 0.1
It is not limited to mm, and may be thicker or thinner. In general, thicker solder layers absorb thermal strain better, but since the thermal conductivity of the solder itself is not very high, hybrid IC
heat dissipation is reduced. As described above, according to the present invention, the occurrence of thermal strain can be suppressed, so that the thickness of the solder layer can be effectively reduced and the heat dissipation performance of the hybrid IC can be improved.

It goes without saying that the present invention can be applied to any semiconductor element (including those using semiconductors other than silicon) and circuits with respect to the type of semiconductor substrate placed on the metal plate or the circuit configuration.

As explained above, according to the present invention, it is possible to reduce thermal strain during manufacturing and operation, and there is an effect that deformation and thermal fatigue failure of each member can be prevented.

[Brief explanation of drawings]

FIG. 1 shows an insulated hybrid IC according to an embodiment of the present invention.
FIG. 2 is a circuit diagram of the embodiment shown in FIG. 1, FIG. 3 is a cross-sectional view of the main part of the embodiment shown in FIG. Fig. 6 is a sectional view of main parts of another embodiment of the present invention, Fig. 7 (a) to (d) and Fig. 8 (a) to (d). 2A and 2B are cross-sectional views showing modified examples of a recessed portion and a notched portion, respectively. 11... Supporting member, 12... Insulating member, 13...
Metal plate, 14.15.16...Semiconductor substrate, 28...
・Four parts, 31... Notch parts, 29, 30.32...
Solder layer, agent Patent attorney Akira Takahashi, USA, L) ・Yu,, 1 Chi 1st // 2nd Ward He, --'' ~ 26 $3 Eyes// Fig. 4 βz (QfX Print 2) Chi 5 Eye βS (Vinegar Kaya Otsu Figure 7th eye 8! 46th eye (α) sharpened. /3 (cl) 2mm and 31

Claims (1)

[Claims] 1. In a semiconductor device having a structure in which at least one of a semiconductor substrate and an inorganic insulating member is bonded to a metal member by a solder layer made of a metal solder, the periphery of the surface of the semiconductor substrate and the insulating member that faces the metal member. 1. A notch or a recess is formed in at least one of part 1 and the surface part of the metal member facing the peripheral part, so as to increase the thickness of the end part of the solder layer. Semiconductor equipment.