JP2559212B2 - Substrate for integrated circuit with good thermal conductivity - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate used in integrated circuits such as ICs, LSIs and hybrid ICs.

As is well known in the prior art, this type of integrated circuit is a small-sized and reliable circuit in which a large number of elements such as transistors and diodes are formed on a silicon substrate by methods such as photoetching diffusion and vapor deposition. It has high advantages such as high cost and low cost. However, since the integrated circuit is sealed in the package, output is restricted by heat generation. Therefore, in high-power ICs and hybrid ICs, heat dissipation fins are attached to the package to actively diffuse heat, or printed circuit boards are used. It is practiced to perform forced ventilation in the state where it is attached to and to promote cooling.

However, the above-mentioned conventional means for cooling is for facilitating heat transfer with the outside in the sealed state of the package, but the heat source is formed on the ceramic substrate. Since the circuit is a circuit, efficient cooling cannot be achieved unless the heat is actively transferred from the circuit to the heat radiation part to the outside such as the heat radiation fins. This point has not been particularly considered in the past, and there is still room for improvement in order to increase the output of the integrated circuit.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a substrate for an integrated circuit, which is excellent in thermal conductivity and therefore can achieve high output.

Means for Solving the Problems The present invention is, as a substrate for forming a semiconductor element integrated circuit, designed to promote heat transfer from a heat generating portion to a heat radiating portion of the substrate itself, and specifically, ,
By engraving a groove of a predetermined depth on the plate-shaped material for the substrate and sealing the open end of the groove with the lid plate,
A cavity is formed in the substrate in a predetermined length along the surface direction, and a plurality of narrow cuts sufficient to generate capillary pressure are formed on the inner wall surface of the groove along the longitudinal direction. It is characterized in that it is formed and only the condensable fluid that carries out heat transport by evaporating and condensing and circulating is enclosed in the cavity.

Since the substrate directly forms a circuit on it,
Although substantially integrated with the heat source, the substrate of this invention
The hollow part becomes a heat pipe, the condensable fluid receives heat to evaporate and evaporates, and the evaporation flows to the low temperature part and then radiates heat to condense and liquefy, so the condensable fluid undergoes a phase change (state change). The heat transfer is carried out as latent heat due to (1) and the amount of heat is extremely large, so that the thermal conductivity of the entire substrate becomes good. In particular, in the present invention, since the condensable fluid in the liquid phase is circulated by the capillary pressure generated in the narrow cut portion, the width of the cavity itself is not particularly limited, and therefore, the width of the cavity is widened and the condensable fluid By increasing the amount, the heat transport amount by the condensable fluid increases, and as a result, the heat generated from the circuit is effectively carried to the heat radiating portion, and the temperature rise of the circuit is prevented.

EXAMPLES Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a partial cross-sectional perspective view showing an embodiment of the present invention, in which a plate-shaped material 1 such as a single crystal silicon plate has a thickness of about several hundred μm, and the plate-shaped material 1 has a rectangular cross section. A groove 2 having a predetermined length is formed from the surface side, and the upper opening end thereof is sealed by a cover plate 3 such as a silicon plate or Pyrex glass. As a result, inside the plate-shaped material 1,
A cavity 4 having a predetermined length along the surface direction is formed. In the inner wall surface of the cavity portion 4, for example, on the lower surface in FIG. 1, thin cut portions 5 each having a width of several μm, which is sufficient to generate capillary pressure, are provided along the longitudinal direction with a plurality of slits 5. Further, the hollow portion 4 is filled with a condensable fluid 6 such as water or alcohol in a state where a non-condensable gas such as air is exhausted.

The size of the cavity 4 is, for example, 200 μm in width.
m, the length is set to about 10 mm, and the width of the cut 5 is
It is set to about 30 μm.

Here, an example of a method for manufacturing the above substrate will be briefly described. First, a single crystal silicon plate (silicon wafer) is prepared, an oxide layer is formed on the surface thereof, and then a photocurable resin (photoresist) is applied. Then, it is exposed to ultraviolet rays using a photomask having a predetermined pattern, and then the resin of the necessary portion is removed with a solvent, the oxide layer of that portion is removed, and then the resin of the other portion is removed with the solvent. After making a hole in a part of the oxide layer in this way, a fine groove is formed by an anisotropic etching reagent that dissolves silicon. Here, the anisotropic etching reagent is a mixed solution of acids having different corrosion rates in different directions in the void lattice of the crystal,
A publicly known one conventionally used in a semiconductor manufacturing process or the like may be used. Then, after removing the oxide layer from the surface of the silicon wafer, a lid plate such as a silicon thin plate is attached to the opening of the narrow groove by an appropriate method such as anodizing adhesion method, and the narrow groove is sealed to form a hollow portion. When performing such joining, it goes without saying that the non-condensable gas is exhausted and the condensable fluid is enclosed.

When actually manufacturing an integrated circuit such as a monolithic IC or LSI using the substrate having the above-described structure, an assembly of semiconductor elements is formed on a predetermined portion of the substrate itself. That is, an epitaxial layer is formed on either surface of the substrate, and an oxide film is formed on the surface of the epitaxial layer.
Then, photoetching and diffusion are repeated by a usual method to form a large number of elements. In the case of a hybrid IC, a circuit is made by a printing method, vapor deposition or sputtering, and then a chip is attached.

The integrated circuit produced in this manner generates heat when energized, and the heat causes the condensable fluid 6 in the cavity 4 to evaporate, and the vapor flows to the low temperature portion in the cavity 4 to radiate heat. Since it is condensed and liquefied, the heat generated by the energization is transported to the low temperature portion as the latent heat of the condensable fluid. The condensable fluid that has radiated heat to be condensed and liquefied is recirculated by the capillary pressure generated in the cut portion 5, and as a result, the condensable fluid circulates while evaporating and condensing, and continuously transfers heat. In other words, as a heat pipe formed inside the substrate, it absorbs heat at a particularly high heat portion of the substrate on which the integrated circuit is formed, and a low temperature portion such as an end portion of the substrate on which the integrated circuit is not formed functions as a heat radiation portion. Become. Here, since the amount of transport of the fluid as latent heat is extremely large, a plurality of the hollow portions 4 are continuously provided so as not to impair the strength of the substrate, and heat is conducted to a heat radiation member such as a heat radiation fin attached to the package. By connecting the above-mentioned heat radiating portion such as the substrate end portion through an appropriate thermal connector made of highly resistant copper or the like, it is possible to cool very efficiently.

FIG. 2 is a partial cross-sectional perspective view showing another embodiment of the present invention. In the substrate shown here, the cavity portion 4 has a trapezoidal cross-section to generate capillary pressure in the corner portions on the left and right sides of the bottom surface. The cut portion 5 is provided. Therefore, even in such a configuration, since the condensable fluid 6 condensed and liquefied by radiating heat flows back through the cut portion 5, the condensable fluid 6 in the liquid phase can be surely maintained even if the width of the cavity 4 is widened. Since the amount of the condensable fluid 6 can be increased as the inner volume of the cavity 4 is increased, the heat transport capacity is increased and the heat conductivity of the substrate is excellent. can do.

It should be noted that the cavity portion 4 having the cut portion 5 as shown in FIG.
In forming the cavity 4 having the
After forming the groove 2 having a rectangular cross section in the same manner as shown in the figure,
The lower portions of both side surfaces of the groove 2 may be melted and removed by laser processing, or the groove 2 having a trapezoidal cross section may be formed by laser processing from the beginning.

EFFECTS OF THE INVENTION As is apparent from the above description, in the present invention, a plurality of thin cutouts are provided in a part of the inner wall surface of the cavity, and the cutouts generate a capillary pressure. Even if the width of the part is widened, the condensable fluid in the liquid phase can be reliably recirculated. Therefore, by increasing the amount of the condensable fluid by widening the cavity, the heat transfer amount in the cavity can be increased. Further, it is possible to enhance the thermal conductivity of the entire substrate and further increase the output of the circuit.

[Brief description of drawings]

1 and 2 are enlarged perspective views, each showing a partial cross section, showing an embodiment of the present invention. 1 ... Plate-shaped material, 4 ... Hollow part, 5 ... Notched part, 6 ...
… Condensable fluid.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Masuko 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Cable Co., Ltd. (72) Masahiko Ito 1-1-5, Kiba, Koto-ku, Tokyo Fujikura Electric Cable Co., Ltd. (56) References Actually open 59-71072 (JP, U) Actually open 60-2841 (JP, U) Actually open 56-26977 (JP, U)

Claims (1)

(57) [Claims] 1. A plate-shaped material for a substrate is engraved with a groove having a predetermined depth, and an opening end of the groove is sealed by a cover plate, so that a predetermined amount is formed inside the substrate along its surface direction. A cavity is formed along the length of the groove, and a plurality of thin notches sufficient to generate capillary pressure are formed along the inner wall surface of the groove along the longitudinal direction. A substrate for an integrated circuit having good thermal conductivity, in which only a condensable fluid that carries out heat transport by condensing and circulating is enclosed.