JP2005259961A - Pressure welding semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure welding semiconductor device capable of balancing the pressurization stress distribution of the whole pressurization contact surface of a semiconductor chip, by easing the concentration of the pressurization stress in the end of the pressurization contact surface of the semiconductor chip in the pressure welding semiconductor device. <P>SOLUTION: A rigidity reduction means for reducing the rigidity of the edge lower than the rigidity of the center is provided, near the edge of one intermediate pressurizing member, which intervenes between a main electrode and a semiconductor chip. Consequently, the stress concentration in the edge of the medium pressurizing member of the pressurization contact surface of a semiconductor chip is eased, so that balancing of the whole distribution is attained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pressure contact type semiconductor device having a pressure contact structure suitable for a large capacity power semiconductor device such as an IGBT, a power MOSFET, or a thyristor.

  As a press-contact type semiconductor device, one having a configuration as shown in FIG.

  The semiconductor device shown in FIG. 11 is an example of a multi-chip type pressure contact type semiconductor device in which a plurality of semiconductor chips 5 are juxtaposed. In this figure, reference numerals 1 and 2 are arranged in common on both sides of the plurality of semiconductor chips 5, respectively. The emitter-side copper electrode and the collector-side copper electrode 3 are arranged so that the convex pressing posts 11 provided on the emitter-side copper electrode 1 corresponding to the respective semiconductor chips 5 are positioned to face the respective semiconductor chips 5. Similarly, the emitter side guide 4 for positioning the emitter side copper electrode is arranged so that the convex pressing post 21 provided on the collector side copper electrode 2 faces the semiconductor chip 5. The collector-side guides 6 and 7 for positioning 2 are molybdenum or copper disposed between the pressing posts of both copper electrodes and the semiconductor chip 5, respectively. Emitter side intermediate pressure member made of tungsten, and the like, and the collector-side intermediate pressure member. These members are housed in an outer container formed of an insulating material (not shown), and the inside thereof is filled with an inert gas such as nitrogen and sealed. At this time, the two copper electrodes 1 and 2 are exposed to the outside in order to make a connection with the outside, and a cooling body (not shown) is joined to the outside of each of the copper electrodes 1 and 2, and the pressure is applied from the outside of these cooling bodies to Each member is brought into pressure contact with each other to be electrically and thermally connected.

  In the semiconductor device having such a pressure-contact structure, the pressure stress on the pressure-contact surface of the semiconductor chip is generally concentrated near the edge of the semiconductor chip as shown by the characteristic line B in FIG. It shows such a distribution. This is because the pressurizing stress is concentrated on the edge of the intermediate pressurizing member that transmits the pressurizing force to the semiconductor chip. For this reason, if it is going to raise the pressurization stress of the center part of a semiconductor chip, the pressurization stress of an edge part will increase by that much, and stress will concentrate more excessively near the edge part of a semiconductor chip. .

  Such an imbalance in the pressure stress distribution of the semiconductor chip leads to an imbalance in the current distribution and the temperature distribution in the semiconductor chip, and the risk of the semiconductor chip being damaged during use due to the combined action of these imbalances. Garage.

  In order to balance such an unbalanced stress distribution on the pressure contact surface of the semiconductor chip, conventionally, as shown in Patent Document 2, intermediate pressure members are joined to both the front and back surfaces of the semiconductor chip via a brazing alloy. It has been proposed. However, even in such a structure, since the thermal expansion coefficient of the semiconductor chip and the intermediate pressure member are different, thermal stress is generated between the two due to heating in the joining process or thermal cycle during use, and the semiconductor chip is damaged. There are things to do.

  In order to prevent damage to the semiconductor chip due to such thermal stress, it is necessary to reduce the thickness of the intermediate pressure member, but this intermediate pressure member disperses external pressure due to its rigidity. Therefore, when the thickness is reduced, the rigidity is reduced and the distribution of the applied pressure becomes unbalanced. As a result, pressure stress is concentrated on a part of the semiconductor chip, from which the semiconductor chip is concentrated. May cause damage.

Moreover, in patent document 1, the convex press post provided in the surface which contact | connects the intermediate pressure member of an emitter side electrode (1st electrode) and a collector side electrode (2nd electrode) via an intermediate pressure member By pressure-contacting the semiconductor chip, the thermal expansion balance between both electrodes and the semiconductor chip is balanced to reduce the stress in the lateral direction of the semiconductor chip. However, this post-structured electrode not only has a complicated shape and increases the processing cost, especially when the number of semiconductor chips arranged in parallel increases, but usually the size of the emitter-side intermediate pressure member is larger than that of the collector-side intermediate pressure member. Since the edge portion is small and comes inside the edge of the collector-side intermediate pressure member, there is a problem that stress concentration occurs at the edge of the emitter-side intermediate pressure member, which cannot be eliminated.
JP 2002-110876 A JP-A-8-167625

  The present invention reduces the concentration of pressure stress at the edge of the pressure surface of the semiconductor chip with a simple structure in order to prevent the risk of damage due to pressure stress or thermal stress in the semiconductor chip in the conventional device described above. An object of the present invention is to provide a pressure contact type semiconductor device capable of balancing the pressure stress distribution of the entire pressure contact surface of the semiconductor chip.

  In order to solve the above-described problems, the present invention provides one or more semiconductor chips each having a first main electrode and a second main electrode on a first main surface and a second main surface facing each other; A first intermediate pressure member that contacts and pressurizes one main electrode, a first main pressure electrode that contacts and pressurizes the first intermediate pressure member, and a second main electrode. A second intermediate pressure member that pressurizes the second intermediate pressure member, and a second main pressure electrode that contacts and pressurizes the second intermediate pressure member, and sequentially superimposes the first and second main pressure electrodes. In the press contact type semiconductor device in which the respective members are pressed against each other by applying external pressure between them, means for reducing the rigidity in the vicinity of the edge of one member of the two intermediate pressing members Is formed.

  In the above invention, the means for reducing the rigidity in the vicinity of the end edge portion can be constituted by a notch in which the vicinity of the edge of the first intermediate pressure member is partially cut out in a step shape. 2).

  Further, the means for reducing the rigidity in the vicinity of the end edge portion can be constituted by a notch in which the vicinity of the end edge portion of the first intermediate pressure member is partially cut out in a groove shape. .

  In the inventions of the above-mentioned claims, it is preferable to cut off the corners of the intermediate pressure member having a stepped notch and a convex cross-sectional shape in an arcuate shape (invention 4).

  In the invention of each of the above claims, a convex pressing post can be formed on a surface of the main pressing electrode that contacts the intermediate pressing member.

  According to the present invention, since the means for reducing the rigidity in the vicinity of the edge portion of the intermediate pressure member that contacts the first main electrode of the semiconductor chip is lower than the rigidity of the central portion, the edge of the intermediate pressure member is provided. The pressure stress concentrated near the edge of the pressure member applied to the semiconductor chip via this pressure member is reduced, and the pressure stress on the semiconductor chip is reduced. By being distributed and balanced over the entire surface, the risk of breakage of the semiconductor chip can be reduced.

  Embodiments of the present invention will now be described with reference to the drawings.

  FIG. 1 shows a first embodiment of the present invention.

  In FIG. 1, reference numerals 1 and 2 denote an emitter-side copper electrode (first electrode) and a collector-side copper electrode (second electrode) that are commonly arranged on both sides of a plurality of semiconductor chips 5, respectively. The emitter-side guides 4 are similarly collector-side guides made of an insulating material, 5 is a semiconductor chip constituting an IGBT or a power MOSFET, and 6 is positioned with respect to each semiconductor chip 5 by the emitter-side guides. An emitter-side intermediate pressure member 7 made of a high-rigidity material such as molybdenum or tungsten, which is in contact with the emitter electrode (first main electrode) surface, is similarly applied to each semiconductor chip 5 by the collector-side guide 4. High rigidity such as molybdenum or tungsten that is positioned and in contact with the collector electrode (second main electrode) surface The collector-side intermediate pressurizing member 8 made of a material is an emitter-side intermediate pressurizing member 6 and a collector-side intermediate member which are in contact with the emitter-side copper electrode 1 and the collector-side copper electrode 2 by the semiconductor chip 5 and the emitter-side and collector-side guides, respectively. It is a chip unit guide that includes the pressure member 7 and positions the chip unit. These members are housed in an outer container formed of an insulating material (not shown), and the inside thereof is filled with an inert gas such as nitrogen and sealed. At this time, the two copper electrodes 1 and 2 are exposed to the outside in order to make a connection with the outside, a cooling body (not shown) is brought into contact with the outside thereof, and the pressure is applied from the outside of these cooling bodies to Each member is brought into pressure contact with each other to make an electrical and thermal connection. The collector-side intermediate pressure member 7 may be fixedly bonded to the collector electrode surface of the semiconductor chip 5 using a braze alloy or the like instead of being pressed.

  In such a configuration, as shown in detail in FIG. 2, the emitter-side intermediate pressurizing member 6 is provided with a notch 6b that is partially cut out in a stepped manner over the entire periphery, as shown in detail in FIG. The thickness in the vicinity is thinner than the thickness of the central portion 6a.

  By setting the intermediate pressure member 6 to such a shape, the rigidity of the edge portion of the member is lowered as compared with the rigidity of the thick central portion. For this reason, the applied pressure applied from the emitter-side copper electrode 1 to the intermediate pressurizing member 6 is reduced in concentration on the end edge and dispersed in the central portion.

  A specific description will be given. The intermediate pressure member 6 in FIG. 2 is made of tungsten, which is a highly rigid material, and the dimensions of each part are selected as follows.

Long side 6W: 17.3 mm
Short side 6D: 14.4 mm
Thickness 6T: 3.0mm
Notch 6b width W: 2.1 mm
Notch 6b height D: 2.0 mm
The result of simulating the distribution of the pressing stress on the pressing contact surface of the semiconductor chip 5 when the semiconductor chip 5 is pressed at a predetermined pressure through such an intermediate pressing member 6 is the result of the simulation of the conventional apparatus. FIG. 3 shows the distribution of pressure stress. The characteristic line A in FIG. 3 shows the pressure stress distribution in the direction of the long side 6W of the pressure contact surface of the semiconductor chip in the embodiment of the present invention, and the characteristic line B shows the same pressure stress distribution in the conventional apparatus. Yes.

  For comparison, a conventional intermediate pressure member having the same outer shape as the intermediate pressure member of the embodiment of the present invention and having the notch 6b eliminated is used for comparison. Of course, the same components are used for the components other than the intermediate pressure member such as a semiconductor chip.

  The horizontal axis in FIG. 3 indicates the distance (mm) in the long side direction from the central axis of the semiconductor chip 5, and the vertical axis indicates the stress received by the pressure contact surface of the semiconductor chip as a unit. Accordingly, W1 on the horizontal axis is the position of the inner end of the notch 6b, W2 is the position of the outer end on the long side of the intermediate pressure member 6, and W3 is the position of the outer end on the long side of the semiconductor chip. Further, P1 represents the peak value of the pressing stress on the pressing contact surface of the semiconductor chip 5 according to the embodiment of the present invention, and P2 represents the peak value of the pressing stress on the pressing contact surface of the semiconductor chip in the conventional device. .

  As shown by the characteristic line B, the pressure stress distribution on the pressure contact surface of the semiconductor chip of the conventional pressure contact type semiconductor device has a high peak value P2 (about 130) at W2, which is the position of the outer end of the intermediate pressure member. According to the present invention, the pressure stress distribution of the semiconductor chip shows a peak at the outer end position W2 of the intermediate pressure member 6 as indicated by the characteristic line A. It can be seen that the peak value P1 (about 105) is reduced by more than 20% from the peak value P2 of the conventional device, and the decrease in the stress distribution inside the intermediate pressurizing member is also a slow change and balanced.

  As described above, according to the present invention, since the concentration of the pressing stress on the pressing contact surface of the semiconductor chip near the end edge of the intermediate pressing member is relaxed and the distribution is balanced, the semiconductor chip in use The risk of breakage is reduced and the reliability can be improved.

  In the first embodiment, as shown in FIG. 4, when the intermediate pressure member 6 is cut into the corners of the right-angled corners R to form an arc shape or the like, Since the concentration of the pressing force at the inner peripheral edge of the notch 6b is further relaxed, the peak of the pressing stress on the pressing contact surface of the semiconductor chip that is in pressure contact therewith can be further reduced, and the distribution can be further balanced. it can.

  Furthermore, in this embodiment, as shown in FIG. 5 and FIG. 6, convex pressing posts 11 or 21 are provided on at least one contact surface of the copper electrodes 1 and 2 that are in contact with the intermediate pressure members 6 and 7, It can be set as the structure which pressurizes an intermediate pressure member with this press post. When the intermediate pressure member is pressurized by the pressure post in this way, the central portion of the intermediate pressure member is pressurized, so that the concentration of applied pressure near the edge of the intermediate pressure member is further increased. As a result, the pressure stress distribution on the pressure contact surface of the semiconductor chip 5 can be further balanced, coupled with the concentration relaxation action of the applied pressure by the intermediate pressure member 6.

  7 and 8 show a second embodiment of the present invention.

  As is apparent from FIG. 7, the second embodiment also includes an IGBT and a power via an emitter-side intermediate pressure member 6 and a collector-side intermediate pressure member 7 between the emitter-side copper electrode 1 and the collector-side copper electrode 2, respectively. A semiconductor chip 5 constituting a MOSFET or the like is sandwiched, and each member is pressed and contacted by external pressure. Reference numerals 3, 4 and 8 are guides for positioning each member. The emitter-side intermediate pressurizing member 6 in the second embodiment is provided with a notch 6c cut out in the shape of a circumferential groove, instead of the stepped notch 6b in the first embodiment, in the vicinity of the edge. ing. Here, as shown in FIG. 8, the intermediate pressure member 6 is formed in a square shape in plan view, and the notch 6c is formed in a square shape similar to the planar outer shape of this member.

  A convex pressing post 11 is formed on the contact surface of the copper electrode 1 with the intermediate pressing member 6, and the pressing post 11 contacts the inner central portion 6 a of the notch 6 c of the intermediate pressing member 6. I try to press it.

  When the groove-shaped notch 6c is provided in the intermediate pressure member 6 in this way, the thickness of the intermediate pressure member 6 is reduced at this portion and the rigidity is lowered, and the groove-shaped notch 6c is used to reduce the rigidity. Function as. As described above, when the groove-shaped notch 6c is provided as a means for reducing the rigidity inside the edge portion of the intermediate pressure member 6, the applied pressure received at the central portion 6a of the intermediate pressure member 6 is groove-shaped. In the notch 6c, the rigidity is weakened by deformation accompanying the reduction, and the pressure applied to the conductor chip 5 at the outer edge is reduced.

  Therefore, also in the second embodiment, the groove-shaped notch 6c provided in the vicinity of the end edge portion of the intermediate pressure member 6 has a stepped cut near the end edge portion of the intermediate pressure member 6 of the first embodiment. When pressure is applied with a predetermined pressure from the outside of the copper electrodes 1 and 2 by acting to reduce the rigidity similar to that of the notch 6b, the pressure stress distribution on the pressure contact surface of the semiconductor chip 5 is an example. 3 in FIG. 3 shows the same tendency as the stress distribution indicated by the characteristic line A, the peak value of stress at the edge of the intermediate pressure member 6 is reduced, and the distribution is balanced as a whole.

  In the second embodiment, when the cross section of the copper electrode 1 pressing post 11 is formed in a circular shape, the groove-shaped notch 6c provided in the intermediate pressure member 6 is pressed as shown in FIG. 9 and FIG. It may be circular or oval surrounding the post 11. In particular, when the plane of the intermediate pressure member 6 is a rectangle, depending on the ratio of the length and width of the intermediate pressure member 6, an end on the long side and the short side of the intermediate pressure member is formed by forming an ellipse that is long on the short side. Even if the edge pressure cannot be equalized, the difference can be reduced.

According to the present invention, one or more semiconductor chips each having a first main electrode and a second main electrode on the first main surface and the second main surface facing each other, and in contact with the first main electrode, A first intermediate pressure member that pressurizes, a first main pressure electrode that contacts and pressurizes the first intermediate pressure member, and a second intermediate pressurizer that contacts and pressurizes the second main electrode A pressure member and a second main pressure electrode that pressurizes the second intermediate pressure member in contact with the second intermediate pressure member are sequentially overlapped, and external pressure is applied between the first and second main pressure electrodes. In the press-contact type semiconductor device in which the members are brought into pressure contact with each other, the stress concentration on the pressure contact surface of the semiconductor chip can be achieved by simply providing a means for reducing the rigidity at the edge of the intermediate pressure member. Can be relaxed and the distribution can be balanced. Is beneficial can improve reliability can reduce the damage accident of-flops.
In the above embodiment, an example of a multi-chip type semiconductor device in which a plurality of semiconductor chips are juxtaposed is shown. However, the present invention can also be applied to a single-chip type semiconductor device having one semiconductor chip. it can.

1 is a longitudinal sectional view showing a pressure contact type semiconductor device according to a first embodiment of the present invention. It is a perspective view of the intermediate pressure member used in the first embodiment of the present invention. It is explanatory drawing of the stress distribution of the press contact surface of the semiconductor chip in a press contact type semiconductor device. It is a front view which shows the modification of the intermediate pressure member used in 1st Example of this invention. It is a longitudinal cross-sectional view which shows the modification of 1st Example of this invention. It is a longitudinal cross-sectional view which shows the other modification of the 1st Example of this invention. It is a longitudinal cross-sectional view which shows the pressurization contact type semiconductor device by 2nd Example of this invention. It is a perspective view of the intermediate | middle pressurization member used in 2nd Example of this invention. It is a top view which shows the modification of the intermediate pressure member used in 2nd Example of this invention. It is a top view which shows the other modification of the intermediate | middle pressurization member used in 2nd Example of this invention. It is a longitudinal cross-sectional view which shows the conventional pressurization contact type semiconductor device.

Explanation of symbols

1 Emitter-side copper electrode (first main electrode)
2 Collector-side copper electrode (second main electrode)
5 Semiconductor chip 6 Emitter-side intermediate pressure member 7 Collector-side intermediate pressure member

Claims (5)

  One or more semiconductor chips each having a first main electrode and a second main electrode on the first main surface and the second main surface that face each other, and a first pressure that contacts and pressurizes the first main electrode An intermediate pressure member, a first main pressure electrode that contacts and pressurizes the first intermediate pressure member, a second intermediate pressure member that contacts and pressurizes the second main electrode, A second main pressure electrode that pressurizes the second intermediate pressure member in contact with the second intermediate pressure member is sequentially superposed, and external pressure is applied between the first and second main pressure electrodes to In the press contact type semiconductor device in which the members are brought into pressure contact with each other, the pressure contact type semiconductor device is characterized in that the at least one intermediate pressurizing member is formed with means for reducing the rigidity in the vicinity of the edge portion thereof.   The means for reducing the rigidity in the vicinity of the end edge portion of the intermediate pressure member is constituted by a notch in which the vicinity of the end edge portion of the intermediate pressure member is partially cut out in a step shape. The pressure contact type semiconductor device according to 1.   The means for reducing the rigidity in the vicinity of the edge of the intermediate pressure member is constituted by a notch in which the vicinity of the edge of the intermediate pressure member is partially cut out in a groove shape. The pressure contact type semiconductor device according to claim 1.   4. The press-contact type semiconductor device according to claim 1, wherein corners of a right-angled corner of the intermediate pressure member are cut off. 5. The press contact type semiconductor device according to claim 1, wherein a convex pressing post is formed on a surface of the main pressing electrode that contacts the intermediate pressing member.

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