JP2506885B2 - Semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device capable of efficiently removing heat generated from a semiconductor element or an integrated circuit chip, and more particularly to maintaining electrical insulation between the semiconductor element or the integrated circuit. And a semiconductor device suitable for maintaining high cooling performance.

[Prior Art] In recent years, semiconductor devices tend to be more and more integrated on a large scale in order to meet the demand for high-speed operation of large-scale electronic computers. Further, in order to reduce the signal delay in the electric wiring connecting between the highly integrated circuit chips as much as possible, various methods have been developed for mounting a large number of integrated circuit chips in a micropackage and shortening the wiring length. ing.

However, with such large-scale integration of semiconductor elements and improvement in packaging density, the heat generation amount and heat generation density from the integrated circuit chip naturally increase, and a cooling structure for removing these heats becomes necessary. ing. Further, this cooling structure is also required to have a function of absorbing various displacements during manufacturing and use such as warpage of the substrate, displacement during connection of semiconductor chips, deformation during assembly of the cooling structure, and thermal deformation of the cooling structure.

Conventionally, especially regarding the cooling structure of large computer systems,
A cooling device as shown in FIG. 3 has been proposed. A large-scale integrated circuit (hereinafter abbreviated as LSI) chip 1 is a multi-layer wiring substrate 2 (hereinafter abbreviated as a substrate) including a number of conductive layers and insulating layers.
It is flip-chip connected by solder 3 and electrically connected to a large number of pins 4 provided on the back surface of the substrate 2 through the conductive layer in the substrate 2. Further, a housing 5 is mounted on the substrate 2 so as to cover many LSI chips 1. A large number of cylinders 6 are formed in the housing 5, and a piston 7 as a heat conducting member for guiding heat from the back surface of the LSI chip 1 and a spring 8 for applying a pressing force to the piston 7 are inserted in the cylinder 6. There is. The enclosed space 9 surrounded by the substrate 2 and the housing 5 is filled with helium gas. The heat generated from the LSI chip 1 is generated by the piston 7
Is transmitted to the piston 7 through the helium gas layer that is present at the contact portion between the spherical tip of the and the back surface of the LSI chip 1, and is further transmitted from the piston 7 to the helium gas layer that is present in the gap between the piston 7 and the cylinder 6. Guided to the housing 5. Then, finally, it is removed by the cooler 10 provided in the upper part of the housing 5 through which cold water or cooling air flows.

However, such a conventional technique has the following problems. The thermal conductivity of helium gas is the largest in the gas, but it is much smaller than that of a metal body such as the piston 7 or the cylinder 6. Therefore, in order to keep the thermal resistance of the helium layer small, it is necessary to reduce the gap between the piston 7 and the cylinder 6. Therefore, the piston 7 or the cylinder 6 is required to have a high processing accuracy, and if the processing accuracy is low, the movement of the piston 7 may be hindered or the temperature of the LSI chip 1 may greatly vary.

In order to remedy the above drawbacks, a cooling structure such as that shown in FIG. 4 is disclosed in US Pat. No. 4,263,965. The cooling structure shown in FIG. 4 is different from the cooling structure shown in FIG.
Many parallel grooves 1 in the housing 11 facing the LSI chip 1
2 is provided, and each thin rectangular heat conduction plate 1 is provided in each parallel groove 12.
A leaf spring 14 that applies a pressing force to the heat conducting plate 3 and the heat conducting plate 13 is inserted. The cooling structure of FIG. 4 has a larger heat transfer area for heat exchange between the heat conducting plate 13 and the side walls of the parallel grooves 12 than the cooling structure of FIG. 3, and the contact between the heat conducting plate 13 and the LSI chip 1 is large. The state is improved to surface contact corresponding to the width of the heat conduction plate 13.

However, the cooling structure of FIG. 4 also has the following problems. That is, since a large number of heat conducting plates 13 are separated and independent of each other and are inserted into the parallel grooves 12, heat exchange between the respective heat conducting plates 13 is hardly performed. However, since the integrated circuit of the LSI chip 1 is composed of a large number of electric circuits, it is extremely rare that heat is generated uniformly. The heat generation distribution in the LSI chip 1 also changes with time. Therefore, for example, when heat is generated only at the edge of the LSI chip 1, only the heat conducting plate 13 near the heat generating portion can take away the heat, and the heat conducting plate 13 far away from the heat conducting plate 13.
Only the heat transmitted through the LSI chip 1 can be carried away. That is, even if a large number of heat conduction plates 13 are arranged on the LSI chip 1, heat transfer between the heat conduction plates 13 is hardly performed, so that the heat transport efficiency of all the heat conduction plates is reduced. In addition, the installation area of the heat conduction plate 13 is the LSI chip 1
There is a limit to the improvement of the cooling property because it is limited by the width of.

As a method for solving the above problems, Japanese Patent Laid-Open No.
-126853 discloses a cooling structure as shown in FIG. In the cooling structure shown in FIG. 5, a plurality of first fins 18 are integrally provided on a heat conducting member 17 having a bottom area larger than the surface area of the semiconductor chip 1, that is, the heat radiation area. A plurality of second fins 16 provided on the inner surface side of the
The heat conducting member 17 and the housing 15 are fitted together, and a spring 20 interposed between the heat conducting member 17 and the housing 15 presses the bottom surface of the heat conducting member 17 against the surface of the semiconductor chip 1. The spring 20 is inserted into the gap 23 of the fin 16,
The hole 21 provided in the housing 15 and the hole 22 provided in the center of the base of the heat conducting member 17 are fixed. housing
A closed space 24 surrounded by 15 and the substrate 2 is filled with a gas having a good thermal conductivity, such as helium gas or hydrogen gas. Therefore, the heat generated in the LSI chip 1 is L
The helium gas is once transferred to the base part of the heat conducting member 17 which is in full contact with the SI chip 1, is diffused uniformly in the base, is then transferred to each fin 18 of the heat conducting member 17, and is a helium gas in each minute gap 19. It travels from the layers to the fins 16 of the housing 15 and is eventually carried away by the cooler mounted on top of the housing 15. Since the fins 18 of the heat conducting member 17 are formed integrally with the base, the LSI chip 1
Even if the internal heat generation distribution is not uniform, the generated heat can be diffused uniformly in the base. Therefore, the heat transfer efficiency of each fin 18 of the heat conducting member 17 can be maximized.

[Problems to be Solved by the Invention] In any case of FIG. 3, FIG. 4 or FIG. 5 as described above, it is essential that the materials of the heat conducting member and the housing have high heat conductivity. In general, a metal such as copper or aluminum is used.
However, since the back surface of the LSI chip 1 is electrically conductive unless special electrical insulation processing is performed, pressing a heat-conducting member made of copper or aluminum on the back surface causes
There is a problem that LSI chips are short-circuited to each other. In JP-A-60-126853, there is disclosed a method in which the material of the heat conducting member or the housing is a SiC material having high electrical insulation and high heat conductivity. There are problems in terms of cost and processing cost due to the difficulty of processing SiC.

An object of the present invention is to inexpensively provide a semiconductor device which ensures electrical insulation between semiconductor elements or integrated circuit chips and has high cooling performance.

[Means for Solving the Problem] The present invention provides a plurality of semiconductor chips mounted on a circuit board, a housing made of a heat conductive metal facing the semiconductor chips, and heat generated from each semiconductor chip. A plurality of heat conductive members made of heat conductive metal, each of which is arranged between the surface of each semiconductor chip and the housing so as to be in contact with the surface of the semiconductor chip for transmitting to the housing; In a semiconductor device having an elastic member that presses against, a thin electrically insulating layer is formed on at least one of contact surfaces of the heat conducting member and the housing.

[Operation] In the above-described structure of the present invention, the thin electric insulation layer provides almost no heat resistance with respect to heat transfer from each heat conduction member to the housing, and the electric insulation between them is sufficiently achieved. . Therefore, it is possible to prevent the chips from electrically short-circuiting each other while ensuring the cooling effect on the semiconductor chips.

[Example] The heat conducting member and the housing in the present invention are
It is made of a metal material having good thermal conductivity and good workability, such as copper or aluminum. Further, as a method of relatively easily forming the thin electric insulation layer on the surface of the fine fin as described above, plasma spraying, CVD, nitridation or oxidation treatment of the metal surface using glow discharge, or the thermal treatment The fin of the conductive member or the fin of the housing may be made of aluminum and the surface thereof may be anodized in an electrolytic solution.

The electrical insulating layer formed on the surface of these fins generally has a lower thermal conductivity than the metal forming the fins. Therefore, in order to suppress the increase in thermal resistance due to the provision of the electrical insulation layer as small as possible, it is desirable to make the thickness of the electrical insulation layer as thin as possible within a range in which necessary electrical insulation can be secured. For example, using a heat conducting member of aluminum,
When a usual anodic oxide film is provided on the surface, the film thickness is 0.1 to 10 μm, preferably 0.1 to 5 μm or less. When a non-porous type hard film is formed, the withstand voltage of the film is high so that the film pressure can be further reduced, and it is desirable that the film pressure is 1 to 3000 Å, preferably 1 to 300 Å.

Further, in order to reduce the thermal resistance as much as possible, it is desirable to form a thin electrically insulating layer only on the surface of the fin of the heat conducting member excluding the surface in contact with the semiconductor chip. When an electrically insulating layer is also formed on the surface of the heat conducting member that contacts the semiconductor chip, the thermal resistance of the insulating layer is added in series between the semiconductor chip and the heat conducting member metal when viewed thermally, While the influence of the thermal resistance of this portion cannot be ignored, when the electrical insulating layer is formed only on the surface of the fin, the thermal resistance of the insulating layer is different from the number of fins between the heat conducting member and the housing. Accordingly, since it is added in parallel, the influence on the overall thermal resistance is small and can be almost ignored. Similarly, the same effect can be obtained when the electrically insulating layer is formed only on the surface of the fin provided on the inner surface of the housing. In the present invention, the fin of the heat conducting member or
It suffices that the electric insulating layer is formed only on the portions of the housing fins that may come into contact with each other, and the optimum method can be selected in consideration of workability, cost, etc. of forming the electric insulating layer.

Further, the thermal resistance can be further reduced by reducing the surface roughness of the back surface of the semiconductor chip and the bottom surface of the base of the heat conducting member that is in contact with the back surface.

In this way, it is possible to secure electrical insulation between LSI chips by using inexpensive and easily processed metal for the heat conducting member and housing of the semiconductor device and without increasing thermal resistance.

An embodiment of the present invention will be described in detail below with reference to FIGS. 1 and 2. In these figures, a large number of plate-shaped fins 16 are provided in parallel with each other on the inner surface of the housing 15 made of a metal having good heat conductivity such as copper or aluminum. A large number of plate-shaped fins 18 having the same pitch as the fins 16 are integrally provided on the base of a heat conducting member 17 made of aluminum having a larger area than the heat transfer area on the back surface of the LSI chip 1. ing. As shown in FIG. 2, on the surface of the fin 18, a hard coating (for example, Al
₂ O ₃ film) 25 is formed. This hard film 25 has a pH
Was adjusted to 8 and anodized in a 3% ammonium tartar powder solution at room temperature and a voltage of about 100Å. The withstand voltage of this oxide film is about 1000V,
It was found that the withstand voltage of about 100V required for insulation between chips was sufficiently satisfied. The base surface of the heat conducting member 17 has a surface roughness of about 0.1 μm.

The fins 16 of the housing 15 and the fins 18 on the base of the heat conducting member 17 are fitted to each other with a minute gap 19 therebetween. The base of the heat conducting member 17 is pressed against the LSI chip 1 by a spring 20 having a soft spring constant so as not to affect the solder balls 3 for connecting the LSI chip 1,
It is in surface contact with the back surface of the SI chip 1. Spring 20
The hole 21 inserted in the gap 23 of the fin 16 and provided in the housing 15 and the hole 22 provided in the center of the base of the heat conducting member 17
It is fixed at and. The closed space 24 surrounded by the housing 15 and the substrate 2 is filled with helium gas having a good thermal conductivity. It should be noted that only the minute gap 19 may be filled with a highly heat-conductive liquid such as heat-conducting grease.

Since the present embodiment is configured as described above, the heat generated in the LSI chip 1 is once transferred to the base of the aluminum heat conductive member 17 which is in full contact with the LSI chip 1, and is uniformly diffused in the base. Then, each fin of the heat conducting member 17 is
18 and then to the fins 16 of the housing 15 through the insulating layer 25 formed on both sides of each fin 18 and the helium gas layer existing in the minute gaps 19, and finally attached to the upper part of the housing 15. It is carried away by the cooling liquid flowing to the cooler 26.

The total thermal resistance of the semiconductor device configured according to this example is almost the same as that when the insulating layer 25 is not formed on the surface of the fin 18, and the electrical insulation between the LSI chips is sufficiently maintained. Do you get it.

Next, another embodiment of the present invention will be described. The heat conducting member 17 made of aluminum provided with the fins 18 in the above embodiment.
Is placed on a table with the base surface in contact with the LSI chip facing downward, and surface nitrogen treatment is performed in nitrogen plasma to form aluminum aluminum (AlN) as the electric insulating film 25 only on the surface of the fin 18.
About 100Å layers of Using this, a cooling structure similar to the above-described example was constructed. Also in this case, it was found that the thermal resistance was almost the same as that when the insulating layer was not formed on the surface of the fin 18, and the electrical insulation between the LSI chips was sufficiently maintained.

Further, FIG. 6 shows an embodiment in which the electric insulating film 25 is formed on the inner surface of the housing including the fins 16.

[Advantages of the Invention] According to the present invention, the heat conduction member and the housing of the semiconductor device can be made of a metal which is inexpensive and easy to process, and the total thermal resistance is hardly increased. Since electrical insulation between them can be secured, a semiconductor device having high cooling performance can be realized at low cost.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a semiconductor device of the present invention, FIG. 2 is a perspective view showing a partial cross section of a heat conducting member in FIG. 1, and FIGS. 3 and 4 are conventional semiconductors. FIG. 5 is a vertical cross-sectional view of a cooling device for a chip, FIG. 5 is a partial cross-sectional perspective view of a conventional cooling device for a semiconductor chip, and FIG. 6 is a vertical cross-sectional view showing another embodiment of the semiconductor device of the present invention. Is. 1 ... LSI chip, 2 ... substrate 3 ... solder bump, 4 ... pin 5,11,15 ... housing 6 ... cylinder, 7 ... piston 8,20 ... spring, 9,24 ... hermetically sealed Space 10,26 …… Cooler, 12 …… Groove 13 …… Heat conduction plate, 14 …… Flat spring 16,18 …… Fin, 17 …… Heat conduction member 19 …… Small gap, 21,22 …… Hole 25: Electrical insulation layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadahiko Miyoshi 4026 Kujimachi, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi Ltd. In-house (72) Inventor Fumiyuki Kobayashi 1 Horiyamashita, Hadano City, Kanagawa Prefecture Hitachi, Ltd. Kanagawa Plant

Claims (3)

(57) [Claims] 1. A plurality of semiconductor chips mounted on a circuit board, a housing made of a heat conductive metal facing the semiconductor chips, and each semiconductor for transmitting heat generated from each semiconductor chip to the housing. A plurality of heat conductive metal heat conductive members, which are respectively arranged between the surface of the chip and the housing so as to contact them, and an elastic member for pressing the heat conductive members against the surface of the semiconductor chip. In the semiconductor device, a thin electric insulating layer is formed on at least one of the contact surfaces of the heat conducting member and the housing. 2. The heat conductive member comprises a base that is in contact with the surface of each semiconductor chip and has a bottom area larger than the surface, and a plurality of fins that are integrally formed on the base. Patent for forming a thin electrically insulating layer on at least one of the surface of the fin of the heat conducting member or the surface of the fin of the housing The semiconductor device according to claim 1. 3. The semiconductor according to claim 1, wherein the heat conducting member or the housing is made of aluminum, and an anodic oxide film or a nitride film is formed as the electrically insulating layer. apparatus.