JP4096492B2 - Flat semiconductor device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flat semiconductor device such as a flat insulated gate bipolar transistor having a structure in which a plurality of semiconductor chips are pressed together.
[0002]
[Prior art]
FIG. 6 is a cross-sectional view of a main part of a conventional flat semiconductor device. A flat semiconductor device that uses a plurality of semiconductor chips 1 (for example, an IGBT chip and a freewheel diode chip) in a pressure-contact state at once, such as a flat structure insulated gate bipolar transistor (hereinafter referred to as an IGBT). The semiconductor chip 61 is sandwiched between two opposing pressure contact electrode plates 76 and 67 and the heat buffer plates 62 and 63 are stacked on both upper and lower surfaces thereof, which is disclosed in JP-A-8-88240. Has been.
[0003]
The heat buffer plates 62 and 63 stacked on both surfaces of the semiconductor chip 61 are made of a Mo plate having a thickness of 1 to 3 mm with good heat conduction, and dissipate heat generated in the semiconductor chip 61 from the upper and lower surfaces of the semiconductor chip 61. It has a function and enables so-called double-sided cooling. In the above-mentioned JP-A-8-88240, when the semiconductor chip 61 and the heat buffer plates 62 and 63 are subjected to thickness variations or one-side pressurization, variations occur in the pressure to be pressed. Then, it becomes difficult to obtain good electrical contact between the semiconductor chip 61, the heat buffer plates 61 and 63, and the pressure contact electrode plates 66 and 67. In order to solve this problem, the thickness correction plates 64 and 65 made of a soft metal sheet of Ag foil are interposed between the pressure contact electrode plates 66 and 67 and the thermal buffer plates 62 and 63, so that the semiconductor chip 61 and the thermal buffer plate 62 are interposed. 63, and the press contact electrode plates 66 and 67 ensure good electrical contact.
[0004]
[Problems to be solved by the invention]
However, there are problems with these technologies. Since the semiconductor chip 61 and the heat buffer plates 62 and 63 are incorporated between the pressure contact electrode plates 66 and 67 in a state of being separated from each other, there is a possibility of causing a positional deviation except in a pressurized state. In order to prevent this, Japanese Patent Laid-Open No. 8-88240 has a structure in which the semiconductor chip 61 and the heat buffer plates 62 and 63 are housed and held in the positioning frame 65. In this case, the positional deviation is hardly generated, but since the semiconductor chip 61 and the heat buffer plates 62 and 63 are not closely fixed, it is not sufficient as a positional deviation prevention measure.
[0005]
In addition, in order to correct the variation in the thickness of the constituent members such as the semiconductor chip 61, when the pressure is once applied, the Ag foil of the thickness correction plates 64 and 65 is reduced, and then the pressure is applied again, if there is this misalignment, It becomes difficult to adjust the thickness after repressurization.
The object of the present invention is to solve the above-mentioned problems, and after assembling the components such as the semiconductor chip and the heat buffer plate between the press contact electrodes, not only during pressurization but also during pressure removal, It is an object of the present invention to provide a flat semiconductor device and a method for manufacturing the same, in which the thickness of the constituent member can be adjusted stably without causing a positional shift of the incorporated constituent member.
[0006]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, a plurality of semiconductor chips arranged on the same plane, a thermal buffer plate provided on each of the principal surfaces of each of the semiconductor chips, and two press-contacts sandwiching them. in the flat type semiconductor device including an electrode plate, between the heat buffer plate and the semiconductor chip sandwiched first thickness adjusting plate formed of graphite sheet, respectively, the heat of the semiconductor chip by pressure and heat The buffer plate is configured to be in close contact with each other via the first thickness adjusting plate .
[0007]
Further, it is preferable that before Symbol semiconductor chip and the heat buffer plate is configured to be positioned with respect to each other by said first thickness adjusting plate.
The first thickness adjusting plate has a recess in a contact surface between the semiconductor chip and the thermal buffer plate, and an outer periphery of the semiconductor chip and the thermal buffer plate is positioned by an inner periphery of the recess. Good.
[0008]
Also, between the heat buffer plate and the pressure-contact electrode plates, write sandwiching second thickness adjusting plate formed of graphite sheet, respectively, the second thickness and the pressure-contacting electrode plate and the heat buffer plate by heating and pressurizing It is good to set it as the structure mutually stuck through the adjustment board .
Also,
The first thickness adjusting plate is larger than the semiconductor chip and the thermal buffer plate, and an outer peripheral portion of the first thickness adjusting plate that does not contact the semiconductor chip and the thermal buffer plate has a convex shape, and the second thickness. adjusting plate is greater Ri by the heat buffer plate, the outer peripheral portion of the second thickness adjusting plate not in contact with the heat buffer plate, it may become convex shape.
[0009]
The manufacturing method includes the step of cutting the expanded graphite sheet containing water to a predetermined size, between the semiconductor chip and the heat buffer plate, and the cut expanded graphite sheet was sandwiched respectively write no step And a step of pressurizing and heating them to bring the semiconductor chip and the thermal buffer plate into close contact with each other via the graphite sheet , and the step of sandwiching includes the step of pressing the thermal buffer plate and the press contact The cut expanded graphite sheet is sandwiched between the electrode plates, and the step of adhering is performed by heating and pressurizing the graphite sheet between the thermal buffer plate and the pressure contact electrode plate. The manufacturing method includes a step of closely contacting each other .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view of an essential part of a flat semiconductor device according to a first embodiment of the present invention. Heat buffer plates 2 and 3 are stacked on top and bottom of a semiconductor chip 1 such as an IGBT chip or a free wheel diode chip via thickness adjusting plates 6 and 7, respectively, and a pressure contact plate 4 and an emitter electrode plate which are collector electrode plates. It is sandwiched between some pressure contact plates 5.
[0011]
When the thickness adjustment plates 6 and 7 (synonymous with the thickness correction plate of the prior art) vary in the thickness of the semiconductor chip 1 and the heat buffer plates 2 and 3, the thickness adjustment plates 6 and 7 are adjusted to adjust the thickness of the pressure contact electrode plates 4 and 5. It is provided so that a uniform pressing force is applied to a plurality of semiconductor chips 1 arranged therebetween. The thickness adjusting plates 6 and 7 are made of graphite sheets (thickness 0.1 mm to 0.3 mm).
[0012]
A method for producing the graphite sheet will be described. When natural graphite is acid-treated with concentrated sulfuric acid, sulfuric acid is absorbed between layered carbon layers. By rapidly heating this in a furnace at a high temperature of 1000 ° C. or higher, the absorbed sulfuric acid is evaporated and separated, and at that time, the graphite expands to obtain expanded graphite. By rolling the expanded graphite, the thickness is compressed to 1/10 to 1/100 to obtain a graphite sheet having a thickness of 0.5 mm to 3 mm. This is further compressed into a graphite sheet having a thickness of 0.2 mm to 2 mm.
[0013]
Next, a thickness adjusting plate obtained by cutting the graphite sheet into a size corresponding to the size of the chip is immersed in water to impregnate water. The thickness adjusting plate containing water is sandwiched between the thermal buffer plates 2 and 3 and the semiconductor chip 1 (IGBT chip and FRD chip), and these are further sandwiched between the press contact electrode plates 4 and 5. Further, a pressurizing force of 10 N to 41 N is applied between the pressure contact electrode plates 4 and 5 at a temperature of 100 ° C. to 200 ° C. per semiconductor chip. By this pressure heating, the water contained in the thickness adjusting plates 6 and 7 evaporates and the thickness adjusting plates 6 and 7 are compressed. At this time, the thickness variation of the semiconductor chip 1, the heat buffer plates 2 and 3 The variation in thickness is adjusted by the compression amount of the thickness adjusting plates 6 and 7. Through the above steps, the semiconductor chip 1 and the heat buffer plates 2 and 3 are adjusted in thickness variation by the thickness adjusting plates 6 and 7 sandwiched therebetween, and the thickness adjusting plate 6 formed from a graphite sheet. , 7 will be in close contact.
[0014]
This close contact is in close contact even when the flat semiconductor device is not pressurized, and is not separated by normal vibration such as transportation. Therefore, the completed flat semiconductor device does not require the positioning guide 65 that is indispensable in Japanese Patent Laid-Open No. 8-88240.
FIG. 2 is a cross-sectional view of an essential part of a flat semiconductor device according to the second embodiment of the present invention. In addition to the thickness adjusting plates 17 and 18 between the semiconductor chip 1 and the heat buffer plates 12 and 13, thickness adjusting plates 19 and 20 are also provided between the heat buffer plates 12 and 13 and the two press contact electrode plates 4 and 5. Thickness adjustment plates 19 and 20 are also inserted between the thermal buffer plates 12 and 13 and the pressure contact electrode plates 4 and 5 to adjust the thickness even when the semiconductor chip 1 and the thermal buffer plates 12 and 13 have large thickness variations. Can do.
[0015]
FIG. 3 is a sectional view showing the principal part of a flat semiconductor device according to a third embodiment of the present invention. The difference from FIG. 2 is that the thickness adjusting plates 29 and 30 sandwiched between the thermal buffer plates 22 and 23 and the pressure contact electrode plates 4 and 5 are in close contact with the thermal buffer plates 22 and 23 individually. In this case, the same effect as in FIG. 2 can be expected. In the figure, reference numerals 27 and 28 denote thickness adjusting plates, which correspond to 17 and 18 in FIG.
[0016]
FIG. 4 is a sectional view showing the principal part of a flat semiconductor device according to the fourth embodiment of the present invention. The semiconductor chip 1 and the heat buffer plates 32 and 33 and the thickness adjusting plates 37, 38, 39 and 40 which are in contact with the pressure contact electrode plates 4 and 5 are positioned so that the semiconductor chip 1 and the heat buffer plates 32 and 33 are positioned from the side. The end portions A of the thickness adjusting plates 32 and 33 have a convex shape. In order to make this end portion into a convex shape, the thickness adjusting plate is sandwiched between the semiconductor chip 1, the heat buffer plates 32 and 33, and the pressure contact electrode plates 4 and 5, and then pressurized and heated as compared with the case of FIG. 2. Increase the applied pressure. This applied pressure is, for example, 5N to 10N. As described above, by forming the end A of the thickness adjusting plates 37, 38, 39, and 40 into a convex shape, even when a strong impact is applied to the flat semiconductor device, the semiconductor chip 1 and the heat buffer plates 32 and 33 are provided. Can be reliably prevented.
[0017]
Further, by using the graphite sheet as the thickness adjusting plates 37, 38, 39, and 40 in this way, the positioning frame 65 required in FIG. 6 is not necessary, and the manufacturing cost can be reduced.
FIG. 5 is a sectional view showing the principal part of a flat semiconductor device according to a fifth embodiment of the present invention. The difference from FIG. 4 is that the thickness adjusting plate 49 in close contact with the pressure contact electrode plate 4 is one. In this case, the same effect as in FIG. 4 can be expected. In the figure, reference numerals 47, 48 and 50 denote thickness adjusting plates which correspond to 37, 38 and 40 in FIG.
[0018]
【The invention's effect】
According to this invention, by using the thickness adjusting plate formed of the expanded graphite sheet between the semiconductor chip and the thermal buffer plate sandwiched between the pressure contact electrode plates and constituting the flat semiconductor device, the semiconductor chip and the thermal buffer plate The thickness variation can be easily adjusted, and the semiconductor chip and the heat buffer plate can be brought into close contact with each other. Since the semiconductor chip and the heat buffer plate are integrated by this close contact, the semiconductor chip and the heat buffer plate do not separate even when the pressure is removed, and the thickness does not shift. The adjustment function can be obtained stably. Furthermore, by disposing the thickness adjusting plate between the heat buffer plate and the press contact electrode plate, the semiconductor chip, the heat buffer plate and the press contact electrode plate are brought into close contact, and the thickness adjusting function can be obtained more stably. it can. In addition, by making the end portion of the thickness adjusting plate a convex portion, the positioning of the semiconductor chip and the heat buffer plate can be facilitated, and even when there is a strong impact, displacement can be prevented. Further, a positioning frame for fixing the positions of the semiconductor chip and the heat buffer plate is not required, and the manufacturing cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of main parts of a flat semiconductor device according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of main parts of a flat semiconductor device according to a second embodiment of the invention. FIG. 4 is a fragmentary cross-sectional view of a flat semiconductor device according to a third embodiment. FIG. 4 is a fragmentary cross-sectional view of a flat semiconductor device according to a fourth embodiment of the invention. FIG. 6 is a cross-sectional view of a main part of a conventional flat semiconductor device.
1 Semiconductor chip 2, 3, 12, 13, 22, 23 Thermal buffer plate 32, 33, 42, 43 Thermal buffer plate 4, 5 Press-contact electrode plate 6, 7, 16, 17, 19, 20 Thickness adjusting plates 27, 28 , 29, 30, 37, 38, 39, 40 Thickness adjusting plates 47, 48, 49, 50 Thickness adjusting plate A End

Claims (7)

A flat semiconductor comprising a plurality of semiconductor chips arranged on the same plane, a thermal buffer plate provided on each principal surface of each of the semiconductor chips, and two press-contact electrode plates sandwiching them. In the apparatus, a first thickness adjusting plate formed of a graphite sheet is sandwiched between the semiconductor chip and the thermal buffer plate, and the semiconductor chip and the thermal buffer plate are bonded to each other by pressure heating. flat type semiconductor device which is characterized in that is in close contact with each other through a. The flat semiconductor device according to claim 1, wherein the semiconductor chip and the heat buffer plate are positioned with respect to each other by the first thickness adjusting plate. The first thickness adjusting plate has a recess in a contact surface between the semiconductor chip and the heat buffer plate, and an outer periphery of the semiconductor chip and the heat buffer plate is positioned by an inner periphery of the recess. The flat semiconductor device according to claim 1. Between the pressure contact electrode plate and the heat buffer plate, the second thickness adjusting plate formed of graphite sheet respectively narrowing seen today the pressure electrode plate and a second thickness adjusting and the heat buffer plate by heating and pressurizing 2. The flat semiconductor device according to claim 1, wherein the flat semiconductor devices are in close contact with each other via a plate . The first thickness adjusting plate is larger than the semiconductor chip and the thermal buffer plate, and an outer peripheral portion of the first thickness adjusting plate that does not contact the semiconductor chip and the thermal buffer plate has a convex shape, and the second thickness. adjusting plate is greater Ri by the heat buffer plate, the flat type semiconductor device according to claim 4, the outer peripheral portion of the second thickness adjusting plate not in contact with the heat buffer plate, characterized in that the convex shape . A flat semiconductor comprising a plurality of semiconductor chips arranged on the same plane, a thermal buffer plate provided on each principal surface of each of the semiconductor chips, and two press-contact electrode plates sandwiching them. In the device manufacturing method,
A step of cutting the expanded graphite sheet containing water to a predetermined size, wherein between the semiconductor chip and the heat buffer plate, the cutting and the respective scissors write No step expanded graphite sheet was, these pressure heating And a step of bringing the semiconductor chip and the thermal buffer plate into close contact with each other via the graphite sheet . The sandwiching step includes sandwiching the cut expanded graphite sheet between the thermal buffer plate and the pressure contact electrode plate,
  The flat mold according to claim 6, wherein the closely contacting step is a step of closely contacting the thermal buffer plate and the press-contact electrode plate through the graphite sheet by the heating and pressing. A method for manufacturing a semiconductor device.

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