JP2000091362A - Pressure contact type semiconductor device and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide a pressure contact type semiconductor device capable of reducing pressure contact force and contact thermal resistance. SOLUTION: Electrodes 6a and 6c are provided on both main surfaces of a semiconductor substrate 5.
, Heat buffer plates 2a and 2c provided on both surfaces of the semiconductor device, and post electrodes 3a and 3c provided outside the heat buffer plate. In a press-contact type semiconductor device for pressurizing, a heat buffer plate and a post electrode are joined and integrated, and one surface side of the post electrode to be joined to the heat buffer plate is connected to a plurality of joint surfaces 3d by lattice grooves 4a and 4c. It is characterized by being divided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure contact type semiconductor device, and more particularly to a pressure contact type semiconductor device having reduced pressure contact force and contact thermal resistance.

[0002]

2. Description of the Related Art The structure of a conventional pressure contact type semiconductor device is shown in FIG.
As shown in FIG. 3, the electrodes 6a, 6c
And a thermal buffer plate 2 which is located above and below the semiconductor element 1 and is made of molybdenum or tungsten.
a, 2c, and post electrodes 3a, 3c located outside the respective thermal buffer plates 2a, 2c. These members are cylindrical containers 8 made of insulating material.
The cylindrical container 8 is housed in a metal flange 9.
The post electrodes 3a and 3c are joined via the electrodes a and 9c, and the inside thereof is sealed with an inert gas. On the other hand, a water-cooled heat sink (not shown) for removing heat generated from the semiconductor element 1 is provided outside each of the post electrodes 3a and 3c.
Each member is brought into contact by pressing 0.

A semiconductor device generates heat due to a large current flowing during operation, but the heat-resistant temperature of the semiconductor element 1 is at most 150.
Since the temperature is on the order of degrees Celsius, it is a technically important task to remove heat from the heat sinks located above and below the semiconductor element 1 and to suppress the temperature rise of the semiconductor element 1. In particular, the amount of heat generated tends to increase with the increase in size and capacity of semiconductor elements, and it can be said that cooling of semiconductor elements is extremely important for practical use of large-size and large-capacity semiconductor devices in the future.

On the other hand, a pressure contact type semiconductor device has a laminated structure as shown in FIG. 11, and a contact thermal resistance always exists at a contact portion of each member. It is known that this contact thermal resistance depends on the pressure contact force, and tends to decrease as the pressure contact force increases. Therefore, the above-mentioned press contact type semiconductor device generally needs to be pressurized from above and below with a press contact force of 50 kgf / cm ² or more, and a large pressurizing mechanism for that purpose is indispensable.

[0005] Further, even when pressure is applied with a large pressing force as described above, the contact thermal resistance does not become zero, and a large-sized cooling unit for cooling the semiconductor device is indispensable.

[0006]

Several methods have been proposed for reducing the pressing force and the contact thermal resistance of such a semiconductor device. For example, in JP-A-5-304179, stress is made uniform by processing concentric grooves in a thermal buffer plate in contact with a semiconductor element. In general, the pressure contact stress is high at the end of the pressure contact surface and low at the center, and consequently, to apply the stress (about 50 kgf / cm ² ) necessary to reduce the contact thermal resistance at the center, It is necessary to apply an excessive pressing force as the stress increases in the part. However, by alleviating the stress concentration at the end by such a method, the pressure can be reduced by making the pressure uniform. However, the reduced pressing force is at most about 10 to 15%, and the contact thermal resistance cannot be reduced at all.

In Japanese Patent Application Laid-Open No. 8-167625, a thermal buffer plate is bonded to the front and back surfaces of a semiconductor element to reduce the pressure contact force and the contact thermal resistance. In this method, the contact thermal resistance between the semiconductor element and the thermal buffer plate becomes almost zero, which is effective for reducing the thermal resistance of the semiconductor device. However, since the thermal expansion coefficient differs between the thermal buffer plate and the semiconductor element,
There is a high possibility that a brittle semiconductor element is broken due to heat stress generated by heating at the time of joining the thermal buffer plate and the semiconductor element or a thermal cycle during use. In order to reduce the thermal stress acting on such a semiconductor element, it is effective to decrease the bonding temperature and to reduce the thickness of the thermal buffer plate. However, there is a limit to the lowering of the joining temperature, and it is actually necessary to reduce the thickness of the thermal buffer plate to cope with it. As a result, in the past, the externally applied pressing force acting on the semiconductor substrate could be made uniform by the high-rigidity thermal buffer plate, but the rigidity was reduced due to the thinner thermal buffer plate, and A uniform pressing force acts on the semiconductor substrate, and there is a high possibility that the semiconductor element is damaged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and maintains high reliability of a semiconductor device by maintaining uniformity of temperature distribution and pressure distribution of a semiconductor substrate, and reduces contact thermal resistance and pressure contact force. An object of the present invention is to provide a pressure contact semiconductor device and a method for manufacturing the same, which have been significantly reduced.

[0009]

According to a first aspect of the present invention, there is provided a semiconductor device having electrodes provided on both main surfaces of a semiconductor substrate, heat buffer plates provided on both surfaces of the semiconductor device, and In a press-contact type semiconductor device having a provided post electrode and pressurizing from above and below via the post electrode, the heat buffer plate and the post electrode are joined and integrated, and the post electrode is joined to the heat buffer plate. Is divided into a plurality of joining surfaces by lattice-shaped grooves.

As a result, the thermal stress and bending generated in the joined body can be reduced, and the pressing force for reducing the contact thermal resistance can be reduced.

According to a second aspect of the present invention, in the first aspect of the present invention, the lattice-shaped groove formed on the joint surface side of the post electrode with the thermal buffer plate does not penetrate the other surface of the post electrode.
Further, it is characterized in that it is formed at a position symmetrical with respect to the center line of the post electrode.

As a result, the deformation and stress generated in the joined body integrated with the joining are made uniform.

[0013] The invention of claim 3 is claim 1 or claim 2.
In the invention, the length of one side of one joining surface divided by a lattice-like groove formed on one surface side of the post electrode joined to the thermal buffer plate is 30 mm or less.

Thus, the post electrode and the thermal buffer member can be joined and integrated in a good condition with a small peeling area.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, a width of the corner of the joint surface divided by the lattice-shaped groove of the post electrode is 0.
A chamfer of 2 mm or more, preferably 0.5 mm or more is formed.

Thus, the stress concentration at the end of the joining surface can be reduced and a good joining state can be obtained without significantly reducing the heat conduction area from the heat buffer plate to the post electrode.

According to a fifth aspect of the present invention, in the invention according to any one of the first to third aspects, the post electrode is formed in a lattice-like groove formed on the joint surface side of the post electrode with the thermal buffer plate. Subtracting the depth of the lattice-shaped groove from the thickness of
The remaining thickness of the post electrode is 5 mm or less.

Thus, unnecessary deformation due to a small external force at the time of joining or assembling can be reduced while improving the adhesion to the semiconductor element or the heat sink at the time of press contact.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the width of the lattice-shaped groove formed on one surface side of the post electrode that is joined to the thermal buffer plate has a width of 0.1 mm.
It is not less than 5 mm.

Accordingly, cracks and peeling are less likely to occur, and it is possible to prevent the brazing filler metal from filling the grooves during the joining, thereby reducing the effect of relaxing the thermal stress.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects, a ratio of a thickness of the thermal buffer plate to a thickness of the post electrode is 0.05 or more. Features.

As a result, a joined body having a small amount of deflection can be obtained.

According to an eighth aspect of the present invention, in the invention according to any one of the first to seventh aspects, in the joined body of the thermal buffer plate and the post electrode, the surface roughness of the thermal buffer plate side in contact with the semiconductor element is reduced. The surface roughness of the post electrode in contact with the heat sink is 6 μm or less.

[0024] This makes it possible to greatly reduce the contact thermal resistance in combination with joining and integrating the heat buffer plate and the post electrode.

According to a ninth aspect of the present invention, in the invention according to any one of the first to eighth aspects, the material of the post electrode is copper, aluminum, or an alloy containing these metals as a main component, and The plate is made of tungsten, molybdenum, or an alloy containing these metals as a main component.

Thus, the post electrode can relieve the thermal stress and strain generated at the time of bonding and integration with the thermal buffer plate, and the thermal buffer plate can uniformly transmit external pressure to the semiconductor element. Becomes

According to a tenth aspect of the present invention, in the invention according to any one of the first to ninth aspects, an intermediate portion between the post electrode and the thermal buffer plate is provided at a joint between the post electrode and the thermal buffer plate. A material having a coefficient of thermal expansion is inserted.

As a result, it is possible to suppress the occurrence of cracking and peeling due to thermal fatigue at the bonding interface between the post electrode and the thermal buffer plate.

According to an eleventh aspect of the present invention, in the invention of the tenth aspect, an intermediate thermal expansion coefficient between the post electrode and the thermal buffer plate, which is inserted into a joint between the post electrode and the thermal buffer plate. Is divided according to one surface to be joined to the heat buffer plate separated by the lattice-shaped grooves formed in the post electrode.

As a result, the occurrence of cracking or peeling due to thermal fatigue at the joint interface between the post electrode and the heat buffer plate is significantly reduced as compared with the case where the material inserted into the joint between the post electrode and the heat buffer plate is not divided. Can be reduced.

According to a twelfth aspect of the present invention, there is provided a semiconductor device having electrodes provided on both main surfaces of a semiconductor substrate, heat buffer plates provided on both surfaces of the semiconductor device, and a post electrode provided outside the heat buffer plate. In a method of manufacturing a pressure-contact type semiconductor device in which pressure is applied from above and below via a post electrode, a step of joining and integrating the post electrode and the heat buffer plate to form a joined body; And a step of applying.

Thus, the pressing force for obtaining a predetermined contact thermal resistance value can be reduced.

According to a thirteenth aspect of the present invention, in the twelfth aspect of the present invention, the joined body is provided with a bend in which the heat buffer plate side is concave.

Thus, the pressing force for obtaining a predetermined contact thermal resistance value can be further reduced.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 shows the structure of a press contact type semiconductor device according to the present invention. The pressure-contact type semiconductor device comprises a semiconductor element 1 having electrodes 6a, 6c provided on both main surfaces of a semiconductor substrate 5, and thermal buffer plates 2a, 2c located above and below the electrodes 6a, 6c and made of molybdenum or tungsten.
And the post electrodes 3a, 3c located outside the heat buffer plates 2a, 2c, respectively, are joined to each other by joining such as brazing.

These members are housed in a cylindrical container 8 made of an insulating material. The cylindrical container 8 is joined to the post electrodes 3a and 3c via metal flanges 9a and 9c, and the inside thereof is formed. Sealed with inert gas.

On the other hand, a water-cooled heat sink (not shown) for removing heat generated from the semiconductor element 1 is provided outside the joined bodies 7a and 7c of the heat buffer plates 2a and 2c and the post electrodes 3a and 3c. The members are brought into contact by pressing the semiconductor device 10 from outside the heat sink by an external pressing mechanism (not shown).

Heat buffer plates 2a, 2 of post electrodes 3a, 3c
On the one surface side to be joined with c, grid-shaped grooves 4a and 4c are formed in the thickness direction of the post electrodes 3a and 3c as shown in FIGS. Multiple joint surfaces 3
d is formed in a divided manner, so that when the heat buffer plates 3a, 3c and the post electrodes 2a, 2c are joined by the lattice-shaped grooves 4a, 4c, or when a heat cycle is applied during use, a joined body is formed. Thermal stress and deflection generated in 7a and 7c are reduced.

The grid-like grooves 4a, 4c formed in the post electrodes 3a, 3c are desirably symmetrical with respect to the center line of the post electrodes 3a, 3c in order to equalize deformation and stress due to bonding. From the viewpoint, the shape of the grooves 4a and 4c is suitably a lattice shape as shown in FIG. In addition,
As shown in FIG. 1, the post electrodes 3a and 3c
The lattice-shaped grooves 4a, 4c reach the other surface, which is the outer surface of the post electrodes 3a, 3c, in order to be joined to the insulating container 8 via the holes 9a, 9c and to make the inside of the semiconductor device 10 hermetically sealed. It is necessary not to.

FIG. 3 illustrates the effect of the present invention by simulating the structure of the semiconductor device according to the present invention shown in FIG.
m, a diameter of 90 m above and below the semiconductor element 1 having a thickness of about 1 mm.
m, molybdenum heat buffer plates 2a, 2c having a thickness of about 2 mm
And the joined bodies 7a and 7c in which pure copper post electrodes 3a and 3c each having a diameter of 80 mm and a thickness of about 20 mm are laminated, and the contact heat of the semiconductor device 10 when pressed from outside with a pressure of 50 kgf / cm ^2. The result of measuring the resistance is shown. In the figure, as a comparative example, the conventional structure shown in FIG. 11 is simulated, and molybdenum thermal buffer plates 2a and 2c having a diameter of 90 mm and a thickness of about 2 mm are provided.
The results of measuring the contact thermal resistance of the semiconductor device in the case where the post electrodes 3a and 3c made of pure copper having a thickness of 0 mm are stacked in a non-joined state, and the pressure contact is similarly applied from outside with a pressure of 50 kgf / cm ² are also shown.

As can be seen from the drawing, the thermal buffer plates 2a, 2
c and the post electrodes 3a and 3c are integrated,
It can be seen that the contact thermal resistance of the semiconductor device 10 can be reduced to 1/3 or less of the related art.

FIG. 4 shows the structure of the semiconductor device according to the present invention and the structure of the conventional semiconductor device required to obtain the same contact thermal resistance as the conventional structure, as in the case of measuring the contact thermal resistance of FIG. The result of measuring the pressing force is shown. FIG.
According to the results of the above, the thermal buffer plates 2a and 2c and the post electrodes 3 that require the largest pressing force to reduce the contact thermal resistance
It can be seen that the pressure contact force can be reduced to about の of the conventional structure by joining and integrating the contact surfaces with a and 3c.

(Second Embodiment) Table 1 below shows a grid-like structure on one surface side of the post electrodes 3a, 3c joined to the thermal buffer plates 2a, 2c according to the present invention shown in FIGS. Groove 4
a. 4C shows the state of occurrence of cracks when forming 4c and joining with the thermal buffer plates 2a and 2c.

In the same experiment, the post electrode had a diameter of 80 m.
m, pure copper with a thickness of 20 mm, diameter of 90 mm for the heat buffer plate,
Using molybdenum having a thickness of 2 mm, the length of one side (hereinafter referred to as a grid) of one surface of the one surface to be bonded to the heat buffer plate divided into a plurality of bonding surfaces by a grid-shaped groove formed in the post electrode. A bonding test was carried out by changing the size (D) in FIG. 2B from 5 mm to 100 mm (no processing of grooves on the lattice).

The brazing filler metal used for joining and unifying is an active metal brazing filler metal to which a trace amount of titanium is added, and a normal silver brazing filler metal.
C. and carried out. Since the melting point of the active metal brazing material is slightly higher than that of the silver brazing material, the joining temperature is slightly higher. Further, in Table 1, the joints were inspected by ultrasonic waves, and described in four stages as shown in Table 1 based on the area of the peeled region.

[0046]

[Table 1]

From the results shown in Table 1, in the test pieces joined without processing the lattice-like grooves, the evaluation was “×” at all the bonding temperatures for all the joining materials. This is mainly because the thermal expansion difference between the post electrode and the thermal buffer plate is large, so that stress concentration occurs near the outer peripheral portion, and cracks generated from the outer peripheral portion propagate inside along the joint interface.

On the other hand, when a lattice-shaped groove is formed on one surface of the post electrode to be joined to the thermal buffer plate according to the present invention, the peeled area tends to be reduced as compared with the above-mentioned conventional method. It can be seen that when silver brazing is used as the bonding material, a generally good bonding state can be obtained by setting the lattice size to 30 mm or less. Therefore, it is understood that the size of the grid to be processed into the post electrode needs to be set to 30 mm or less. In addition, the active metal brazing material generates a larger thermal stress than the silver brazing material due to the high joining temperature, and a relatively high peeling area still occurs when the lattice size is 30 mm. A good bonding condition is obtained. Since the active metal brazing material can provide higher bonding strength than the silver brazing material, when using the active metal brazing material, it can be said that it is preferable to set the lattice size to be processed into the post electrode to 20 mm or less.

As described in (Third Embodiment) (Second Embodiment), according to the present invention, a lattice-shaped groove is formed on one surface of a post electrode to be joined to a heat buffer plate. It was clarified that splitting of one surface of the post electrode into a plurality of bonding surfaces can prevent cracking and peeling of the bonding surfaces. However, the test pieces (evaluation: Δ) joined at 850 ° C. using the active metal brazing material with the lattice size shown in Table 1 set to 20 mm were cut, and the occurrence of cracks was investigated in detail.
Cracks (peeling) occur at the ends of the joint between the post electrode and the thermal buffer plate, which are separated by lattice-shaped grooves. Even if one surface is divided into small joint surfaces, the end of each joint is Was found to cause stress concentration.

Therefore, as shown in FIG. 2C, a chamfered portion 3e is formed at a corner of the post electrode to be joined to the thermal buffer plate.
Was formed, and a bonding test was performed by changing the width (w in FIG. 2C). The lattice size was 20 mm, which was a result shown in Table 1 and a relatively good bonding state was obtained.

Table 2 below shows the results of the joining test in which the width (w) of the chamfered portion 3e was changed. In the table, “the value of the chamfer width is 0” indicates the result when no chamfer is performed. From the results, it can be seen that, under any of the joining conditions, as the width of the chamfer is increased, the stress concentration is alleviated, and a good joining state is obtained. However, if the width of the chamfer is increased, the heat conduction area from the thermal buffer plate to the post electrode is reduced, and the possibility of causing overheating of the semiconductor element is increased. Therefore, excessive chamfer width is not preferable. From the results in Table 2, it is considered that the chamfer width is 0.2 mm or more is appropriate, and it can be said that 0.5 mm or more is preferable for a semiconductor device having a low thermal load.

[0052]

[Table 2]

(Fourth Embodiment) According to the present invention shown in FIG. 1, the purpose of forming a grid-like groove in a post electrode is as follows.
In addition to relaxing the thermal stress at the joint to prevent cracking and peeling, it also reduces the rigidity of the post electrode to reduce the deformation (deflection) of the joined body that integrates the post electrode and the thermal buffer plate. It is to control. The rigidity of the post electrode is determined by subtracting the depth of the grid-like groove (t _{2 in} FIG. 2C) from the thickness of the post electrode (t in FIG. 2C) and the remaining thickness (FIG. 2C).
It is greatly affected by t ₁ ) in (c). Therefore, the diameter 80
mm, 20 mm thick pure copper post electrode and 90 mm diameter
A bonding test was performed using a molybdenum heat buffer plate having a thickness of 2 mm and a thickness of 2 mm, a grid size formed on the post electrode of 20 mm, and changing the depth of the groove. The joining material was an active metal brazing material, and the joining temperature was 850 ° C.

FIG. 5 shows the remaining thickness of the post electrode (FIG. 2).
The result of measuring the amount of deflection of the joined body of the post electrode and the heat buffer plate when bonding to the heat buffer plate while changing t ₁ ) in (c) is shown. The results show that the rigidity of the post electrode decreases and the amount of deflection tends to decrease as the remaining thickness decreases. Further, by reducing the remaining thickness and reducing the rigidity of the joined body in this way, there is an advantage that the joined body can obtain good surface contact with the semiconductor element or the heat sink even with a low pressing force. .

However, when the thickness of the remaining portion is small, the groove processing becomes difficult, and the possibility of easy deformation due to a small external force at the time of joining or assembling increases, so that excessive reduction of the remaining portion thickness is not preferable. From the results shown in FIG. 5 and the adhesion to the semiconductor element and the heat sink at the time of pressing, the remaining thickness is 5 mm or less, preferably 2 mm or less.

(Fifth Embodiment) The following Table 3 shows that the diameter is 8
0mm, 20mm thick pure copper post electrode and 9mm diameter
The results of a bonding test performed using a Mo thermal buffer plate having a thickness of 0 mm and a thickness of 2 mm, the grid size formed on the post electrode 1 being 20 mm, and changing the groove width (d in FIG. 2B) are shown. .

From the results, it can be seen that if the width of the groove is small, cracks and peeling are likely to occur. As a result of cutting investigation of the joint specimen, it was found that if the width of the groove was small, the molten brazing material filled the inside of the groove by capillary action, and the effect of the groove to reduce the thermal stress at the time of joining was reduced.

The filling of the groove with such a brazing material varies depending on the wettability, surface tension, joining temperature, etc. of the brazing material used. From the results of this experiment, the groove width was 0.5 mm or more.
It is understood that preferably 1 mm or more is required. Note that as the width of the groove increases, the heat conduction area from the thermal buffer plate to the post electrode decreases, and the possibility of causing overheating of the semiconductor element increases. Therefore, it is not preferable to increase the width of the groove excessively.

[0059]

[Table 3]

(Sixth Embodiment) FIG. 6 shows the relationship between the thickness of the heat buffer plate and the amount of deflection of the post electrode assembly of the heat buffer plate. In the figure, a molybdenum heat buffer plate having a diameter of 90 mm, a diameter of 80 mm, a thickness of 20 mm, and a grid size of 2 are also used.
After bonding at 850 ° C. using an active metal brazing material under the conditions of 0 mm and the remaining thickness of the post electrode of 5 mm, the amount of deflection generated in the bonded body of the heat buffer plate and the post electrode when cooled to room temperature was determined. It is. From the figure, it is understood that the amount of deflection generated in the joined body decreases as the thickness of the thermal buffer plate increases.

Molybdenum and tungsten, which are considered to be suitable as heat buffer plates, have poor machinability, and when the amount of deflection is large, the machining allowance for increasing the parallelism of the joined body increases. From the results of FIG. 6, the deflection ratio tends to gradually saturate when the thickness ratio between the heat buffer plate and the post electrode is 0.05 or more. Therefore, the thickness ratio between the heat buffer plate and the post electrode is It is considered that 0.05 or more, preferably 0.1 or more is necessary.

(Seventh Embodiment) FIG. 7 shows a structure of the pressure contact type semiconductor device of the present invention shown in FIG.
A diameter of 90 mm and a thickness of 2 above and below a 00 mm semiconductor element.
mm molybdenum heat buffer plate, diameter 80 mm, thickness 2
The results of measuring the contact thermal resistance value when a joined body integrally joined to a 0 mm copper post electrode is placed and pressed at 50 kgf / cm ² from above and below are shown. The depth of the groove was set so that the length of one side of the grid size was 20 mm and the remaining thickness of the post electrode was 5 mm on the joining surface of the copper post electrode with the heat buffer plate, and the heat contact with the semiconductor element was made. The measurement was performed while changing the surface roughness of the buffer plate and the surface roughness of the post electrode in contact with the water-cooled heat sink.

As shown in FIG. 3, the contact thermal resistance can be reduced to about 1/3 of that of the prior art only by joining and integrating the heat buffer plate and the post electrode according to the present invention. Meanwhile, as the surface roughness of the contact surface is reduced, the contact thermal resistance of the semiconductor device can be further reduced. By making the surface roughness of the contact surface 0.5 μm, the contact thermal resistance of the semiconductor device can be reduced to 1/6 or less. It can be seen that it can be reduced.

(Eighth Embodiment) FIG. 8 shows the results of measuring the thermal resistance and the elastic modulus of a typical metal material, which were carried out to select the materials to be used for the heat buffer plate and the post electrode. In order to suppress heat generation from the heat buffer plate and the post electrode, it is appropriate to form them with a material having a small electric resistance, and to reduce the heat of the semiconductor element with a heat sink. Small materials are preferred. From such a viewpoint, stainless steel (SUS), nickel (Ni), or the like is not suitable as a material used for the heat buffer plate or the post electrode, and copper (Cu) and aluminum (A1) as shown in FIG. , Silver (Ag), gold (Au), molybdenum (Mo), and tungsten (W) are suitable.

As described above, it is important for the thermal buffer plate to have a large elastic coefficient in order to uniformly transmit external pressure to the semiconductor element. FIG. 8 shows that copper, aluminum, silver, and gold are not suitable as materials satisfying such requirements, and tungsten and molybdenum are suitable.

On the other hand, as the post electrode material, a material having a small elastic coefficient is preferable in order to reduce thermal stress and strain generated at the time of bonding with the thermal buffer plate. From such a viewpoint, tungsten and molybdenum are conversely used. It is not suitable, and it can be said that steel, aluminum, silver, and gold are suitable.
Among them, copper and aluminum are considered optimal from the viewpoint of cost.

(Ninth Embodiment) According to the present invention shown in FIG. 1, by forming a grid-like groove in the post electrode, the amount of cracking, peeling and bending of the joined body between the post electrode and the heat buffer plate is increased. However, since the post electrode and the thermal buffer plate have significantly different coefficients of thermal expansion, a large residual stress is generated. When a semiconductor device is used, a thermal load is repeatedly applied. Therefore, it is expected that cracks and peeling will occur due to thermal fatigue at a bonding interface between the post electrode and the thermal buffer plate due to a thermal cycle.

FIG. 9 shows a case where copper is selected as a typical post electrode material and molybdenum is selected as a thermal buffer material, and when a 1 mm thick plate having a different coefficient of thermal expansion is inserted between the two, Shows the result of calculating the thermal stress generated in the above by elastic analysis. The vertical axis of the figure indicates the thermal stress when the post electrode is directly joined to the thermal buffer plate as 1, and the ratio of the thermal stress value when a plate having a different coefficient of thermal expansion is inserted.
The calculation results show that the thermal stress generated in the post electrode decreases as the plate closer to the post electrode has a coefficient of thermal expansion.

Therefore, a molybdenum heat buffer plate having a diameter of 90 mm and a thickness of 2 mm and a copper post electrode having a diameter of 80 mm and a thickness of 20 mm were used, and the grid size of the post electrode was 20 m.
m, when a groove having a remaining thickness of 5 mm was machined and joined together (Example I in Table 4), the diameter was 80 mm, the thickness was 1 mm, and the coefficient of thermal expansion was about 11 × 10 −6 / ° C. When the copper / tungsten alloy plate is inserted and joined (Example of Table 4)
II) and a case where the same material having the same size as the lattice and having a size of 20 mm × 20 mm and a thickness of 1 mm is inserted into the joint between the post electrode and the heat buffer plate corresponding to each joint surface and joined (Table 4). The three types of specimens of Example III) were manufactured, and heat
Table 4 shows the results of the cycle test. In addition, the heat cycle test was repeated between -50 ° C and 150 ° C, and the cracking and peeling state was evaluated by ultrasonic waves every fixed cycle.

From the results in Table 4, it was confirmed that fine cracks were generated at the bonding interface after 1 × 103 cycles in Examples I and II. No peeling was detected, and it was confirmed that the thermal fatigue characteristics of the joint were improved by the insertion of the intermediate thermal expansion material.

[0071]

[Table 4]

(Tenth Embodiment) As shown in FIGS. 5 and 6, even when a post-like electrode is formed with a lattice-like groove according to the present invention and bonded to a thermal buffer plate, the coefficient of thermal expansion of both of them is increased. Due to the difference, a slight bending occurs in the joined body between the post electrode and the heat buffer plate. At the time of use, in order to reduce the contact thermal resistance on the contact surface, the joined body of the post electrode and the thermal buffer plate needs to be parallel and smooth, and a correspondingly large pressing load is required.

Thus, a molybdenum heat buffer plate having a diameter of 90 mm and a thickness of 2 mm and a copper post electrode having a diameter of 80 mm and a thickness of 20 mm were used, and the grid size of the post electrode was 20 m.
m, a groove having a remaining thickness of 5 mm was machined to prepare a test body in which the post electrode and the heat buffer plate were joined. At this stage, the joint between the post electrode and the heat buffer plate is bent by about 0.6 mm, and the post electrode has a larger coefficient of thermal expansion than the heat buffer plate. The electrode side has a concave shape.

In the embodiment I, the contact thermal resistance when the semiconductor device is assembled as it is and pressurized with the same pressing force (50 kgf / cm ² ) as that of the conventional semiconductor device shown in FIG. The pressing force required to obtain the same contact thermal resistance as that of the semiconductor device having the conventional structure was measured.

In Example II, the joined body of the post electrode and the heat buffer plate is pressed from above and below, and the upper and lower surfaces of the joined body are made parallel and smooth with the pressurized bear. The elastically deformed portion springs back, and a deflection of about 0.2 mm remains.

Further, in Example III, the joined body of the post electrode and the heat buffer plate was pressed against the spherical seat, and after the pressure was released, a deflection of about 0.1 mm was forcibly applied to the heat buffer plate side. That is, a concave deformation was given to the heat buffer plate side.

FIG. 10 shows the measurement results of the contact thermal resistance and the pressing force of Example I, Example II and Example III. In the same figure, based on the contact thermal resistance value and the pressure contact force in the case of Example I,
The contact thermal resistance and the pressing force of Examples II and III are expressed as ratios to the values of Example I.

From the results shown in FIG. 10, the contact thermal resistance value of Example II is almost the same as that of Example I, but the pressure contact force is about 75% of that of Example I. It was confirmed that the pressing force could be reduced by deforming. In Example III, the contact thermal resistance was about 85% of that in Example I.
%, The pressure contact force shows a value of about 60% of Example I,
It can be seen that the pressing force can be further reduced by forcibly imparting deflection to the heat buffer plate side to the joined body of the post electrode and the heat buffer plate. This is because deformation can be uniformized by deforming on the spherical seat, and the post electrode expands due to temperature rise during use, so that the deflection of the joined body between the post electrode and the thermal buffer plate becomes almost zero during use. It is.

[0079]

According to the present invention, it is possible to manufacture a semiconductor device having extremely low contact thermal resistance, and it is possible to greatly reduce the size and cost of the cooling unit.
Further, the semiconductor element can be cooled uniformly, and the external pressure can be uniformly applied to the semiconductor element, so that a highly reliable semiconductor device can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic structural view of a press-contact type semiconductor device according to an embodiment of the present invention.

FIGS. 2A to 2D are schematic views of the shape of a groove formed on the surface of a post electrode used in the press-contact type semiconductor device.

FIG. 3 is a graph comparing the contact thermal resistance between the semiconductor device of the present invention and a semiconductor device having a conventional structure.

FIG. 4 is a graph comparing the pressure contact force between a semiconductor device of the present invention and a semiconductor device having a conventional structure.

FIG. 5 is a graph showing the relationship between the amount of deflection and the remaining thickness.

FIG. 6 is a graph showing the effect of the thickness of the heat buffer plate on the amount of deflection of the joined body of the post electrode and the heat buffer plate.

FIG. 7 is a graph showing the effect of surface roughness on the contact thermal resistance of a semiconductor device of the present invention and a conventional structure.

FIG. 8 is a graph comparing a thermal resistance value and an elastic coefficient of a post electrode and a thermal buffer plate candidate material.

FIG. 9 is a graph showing a relationship between a coefficient of thermal expansion and a thermal stress.

FIG. 10 is a graph showing changes in thermal resistance and pressure force due to pressure molding.

FIG. 11 is a schematic structural view of a conventional pressure contact type semiconductor device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Semiconductor element 2a, 2c ... Thermal buffer plate 3a, 3c ... Post electrode 4 ... Groove 5 ... Semiconductor substrate 6a, 6c ... Electrode 7a, 7c ... Joint body 8 ... Green container 9a, 9c ... Metal flange 10 ... Semiconductor apparatus

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Ishiwatari 2-4-4 Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Inside the Toshiba Keihin Works (72) Inventor Takao Inukai 2--4, Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Address Toshiba Corporation Keihin Plant (72) Inventor Akinori Nagata 2-4-4 Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Toshiba Corporation Keihin Plant (72) Inventor Atsushi Yamamoto 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Corporation Inside the Fuchu Plant (72) Inventor Takashi Kusano 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Corporation Fuchu Plant F-term (reference) 5F005 BA02 GA01 GA02 5F047 JA02 JA08 JA12 JA13 JA14

Claims (13)

[Claims] 1. A semiconductor device having electrodes provided on both main surfaces of a semiconductor substrate, heat buffer plates provided on both surfaces of the semiconductor device,
In a pressure contact type semiconductor device having a post electrode provided outside the heat buffer plate and pressurizing the post electrode from above and below via the post electrode, the heat buffer plate and the post electrode are joined and integrated, and the heat buffer of the post electrode is reduced. A semiconductor device wherein one surface side to be joined to a plate is divided into a plurality of joining surfaces by lattice-shaped grooves. 2. A lattice-shaped groove formed on the joint surface side of the post electrode with the thermal buffer plate does not penetrate the other surface of the post electrode, and is symmetrical with respect to the center line of the post electrode. 2. The semiconductor device according to claim 1, wherein the semiconductor device is formed at a position. 3. The post electrode, wherein one side of one joining surface divided by a lattice-like groove formed on one surface side to be joined to the thermal buffer plate has a side length of 30 mm or less. The semiconductor device according to claim 1. 4. A width of 0.2 mm or more at a corner of a joint surface divided by a lattice-like groove of the post electrode.
4. The semiconductor device according to claim 1, wherein a chamfer of at least 0.5 mm is formed. 5. A post electrode having a lattice shape formed by subtracting the depth of the lattice-like groove from the thickness of the post electrode with respect to the lattice-like groove formed on the joint surface side of the post electrode with the thermal buffer plate. 4. The semiconductor device according to claim 1, wherein the remaining thickness is 5 mm or less. 6. The post-electrode according to claim 1, wherein the width of the lattice-shaped groove formed on one surface of the post electrode joined to the heat buffer plate is 0.5 mm or more. Semiconductor device. 7. The semiconductor device according to claim 1, wherein a ratio of a thickness of said thermal buffer plate to a thickness of said post electrode is 0.05 or more. 8. In the joined body of the heat buffer plate and the post electrode, the surface roughness of the heat buffer plate contacting the semiconductor element and the surface roughness of the post electrode contacting the heat sink are 6 or less.
The semiconductor device according to any one of claims 1 to 7, wherein the thickness is not more than μm. 9. The material of the post electrode is copper, aluminum, or an alloy containing these metals as a main component,
9. The semiconductor device according to claim 1, wherein a material of the thermal buffer plate is tungsten, molybdenum, or an alloy containing these metals as a main component. 10. A material having a thermal expansion coefficient intermediate between that of the post electrode and that of the thermal buffer plate is inserted into the joint between the post electrode and the thermal buffer plate.
10. The semiconductor device according to any one of items 1 to 9. 11. A material having a coefficient of thermal expansion intermediate between that of the post electrode and the thermal buffer plate, which is inserted into a joint between the post electrode and the thermal buffer plate, has a lattice shape formed on the post electrode. 2. The semiconductor device according to claim 1, wherein the partition is divided along one surface to be joined to the heat buffer plate divided by the groove.
0. The semiconductor device according to item 0. 12. A post electrode comprising: a semiconductor element having electrodes provided on both main surfaces of a semiconductor substrate; heat buffer plates provided on both surfaces of the semiconductor element; and a post electrode provided outside the heat buffer plate. In the method for manufacturing a pressure-contact type semiconductor device in which pressure is applied from above and below through a step, a step of joining and integrating the post electrode and the heat buffer plate to form a joined body, and a step of applying pressure to the joined body to impart deflection. A method for manufacturing a semiconductor device, comprising: 13. The method of manufacturing a semiconductor device according to claim 12, wherein the joined body is provided with a bend in which a heat buffer plate side is concave.