JPS6216551A - Manufacture of substrate for integrated circuit having good thermal conductivity - Google Patents

Abstract

PURPOSE:To form a heat pipe in a plate material for substrate by a method wherein a fine groove, both ends of which in the longitudinal direction are shut, is engraved and condensable fluid is inhaled in the fine groove. CONSTITUTION:A fine groove 2 is engraved in a plate material 1, and the fine groove 2 is shut with a cover plate 4 having a fine hole 3. The whole is heated up to the prescribed temperature, and is cooled with condensable liquid which should be encapsulated in the fine groove 2 as the operating fluid. Such an operation is repeatedly executed plural times. After the condensable fluid is injected in the fine groove 2, the condensable liquid is frozen and the fine hole 3 is sealed in a vacuum atmosphere. An epitaxial layer is formed on the surface of the substrate, and at the same time and oxide film is formed on the surface thereof. Many elements are formed by repeatedly performing photo etchings and diffusions to form the integrated circuit. The integrated circuit in such a way generates heat by conduction, but the condensable fluid 7 in the fine groove 2, which is the heat pipe evaporates with the heat, flows to the lower-temperature part, and radiates heat, thus condensing into liquid. As a result, the substrate is very efficiently cooled.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method of manufacturing a substrate used for an integrated circuit such as an IC, an LSI, or a hybrid IC.

As is well known in the art, this type of integrated circuit is one in which a circuit including a large number of elements such as transistors and diodes is formed on the surface of a silicon substrate by methods such as photoetching, diffusion, and vapor deposition. It has excellent advantages such as being small, highly reliable, and inexpensive. However, since integrated circuits are sealed in packages, their output is limited by heat generation. Therefore, in high-output XCs and hybrid ICs, heat dissipation is carried out by attaching heat dissipation fins to the package, or printed circuit boards are used to dissipate heat. Forced ventilation is used to promote cooling when installed in a

, Problems to be Solved by the Invention However, the conventional cooling means described above are intended to promote heat exchange with the outside in a sealed state of the package, but the heat source is located on the ceramic substrate. Since it is a formed circuit, efficient cooling cannot be achieved unless heat is actively transferred from the circuit to an external heat radiating part such as a heat radiating fin. Although this point has not been given much attention in the past, there is still room for improvement in achieving higher output and higher functionality of integrated circuits.

In view of the above-mentioned circumstances, this invention has high thermal conductivity, thus achieving high output and high l! The object of the present invention is to provide a method for manufacturing integrated circuit substrates that can be used to improve performance.

Means for Solving the Problems The present invention is a method of manufacturing a substrate having a heat pipe inside to promote heat transfer from a heat generation source to a heat dissipation portion to the outside. The board has both longitudinal ends closed [! 1 is engraved, and the N end of the am is covered with W! by a cover plate having micro holes. close,
Next, the plate material is heated to a predetermined temperature and '1
1 cooling operation in a condensable environment is repeated several times to draw the condensed t/a@ fluid into the 1 m groove and
The non-condensable gas in the cavity is replaced with condensable fluid vapor, and the condensable fluid roughly sucked into the tR11I is frozen and the micropores are sealed in a vacuum. This method is characterized by forming a heat pipe.

In other words, the heat pipe formed on the substrate for integrated circuits is
The width is narrow, on the order of several hundred micrometers, and as a result, a narrow groove is formed, and non-condensable gas is exhausted from the narrow groove.
In addition, a condensable fluid to be used as a working fluid is injected, and the F
It is necessary to seal the il groove, and therefore it is necessary to perform such an operation on a large number of ams at the same time. Therefore, in this invention, the existing non-condensable gas is exhausted by increasing the pressure inside the narrow groove covered with a perforated lid by heating the nail, and then cooling it in the condensable fluid that is to be used as the working fluid. By doing so, the pressure inside the sI1g is reduced and the condensable fluid is sucked through the micropores. Therefore, by repeating such operations of heating and cooling, a large amount of condensable fluid is gradually produced in the interior of the system, and the non-condensable gas is replaced by the vapor of the condensable fluid. After that, by sealing the micropores in a vacuum while the condensable fluid is frozen, the narrow grooves are sealed without causing the condensable fluid to scatter or the non-condensable gas to enter. It can be done.

Example The present invention will be described in detail below.

In the method of this invention, first, as shown in FIG. 1, I[lrf:i2 is engraved on a target board 1. Here, as the plate material 1, a single crystal silicon wafer is used for IC or SI, and a ceramic plate is used for hybrid IC.

Thin again? 112 is ultimately intended to be a heat pipe, and for example, it can be a V-groove with a width and depth of about 200μ■ and a length of about 10111+, in which case the grooves at the corners are Since it becomes even narrower, the corner part can act as a wick.The method for forming the narrow groove 2 in a silicon wafer is as follows.
First, an oxide layer is formed on the surface of a silicon wafer, and then a photoresist is applied to the surface of the oxide layer.
Expose to ultraviolet light using a photomask with a predetermined pattern, then remove the photoresist in the required areas with a solvent,
After that, the photoresist in the exposed area is removed using a solvent.

After forming a hole in a portion of the oxide layer in this way, a narrow groove 2 is etched using an anisotropic etching reagent that dissolves silicon. Here, the anisotropic etching reagent is a special liquid mixture that has different corrosion rates in different directions in the crystal void lattice.

The narrow groove 2 formed as described above is closed by a cover plate 4 having fine holes 3. As this cover plate 4, a medium-crystalline silicon plate, a suitable ceramic plate, or Pyrex glass can be used, and the fine holes 3 may be simply bored in the cover plate 4 as shown in FIG. As shown in Figure 3, the capillary tube (hair 111
In particular, when the capillary tube 5 is connected, the fine pores 3 can be easily sealed by melting the capillary tube 5. Furthermore, the adhesion of the cover plate 4 to the plate material 1 is performed using m-pole treatment 1! An appropriate method such as splashing can be adopted.

After the opening of the narrow groove 2 is closed by the cover plate 4, the entire body is heated to a predetermined concentration, and then a condensable fluid (for example, water, fluorocarbon, etc.) to be sealed in the narrow groove 2 as a working fluid is heated. , alcohol, etc.) and perform such operations l!
This heating operation and cooling operation, which are repeated several times, are described in 11.
This is an operation for exhausting existing non-condensable gas such as air inside the groove 12 and injecting condensable fluid into the narrow groove 2, and the pressure inside the groove 11a12 is increased by heating. Therefore, condensable fluid is drawn into the slot 892 because the non-condensable gas is first vented somewhat and then by cooling in the condensable fluid the internal pressure within the slot 2 is reduced. In addition, in the case of heating after the 2nth groove,
Since the condensable fluid evaporates within the narrow groove 2, the lI-condensable gas is further actively discharged. Therefore, by repeating the heating and cooling described above, a large number of U atoms are gradually formed within the narrow groove 2.
The condensable fluid is removed and the non-condensable gas is replaced by condensable fluid vapor. Incidentally, an electric heater, an infrared heater, etc. may be used as a heating means, whereas a cooling method is as follows: 2! Soaking is an effective method.

After injecting the condensable fluid into the narrow groove 2 as described above,
The condensable fluid is frozen and then the micropores 3 are sealed in a vacuum atmosphere. The fine holes 3 can be sealed by plugging them with a suitable material. For example, when the capillary tube 5 described above is attached, the heating plate 6 is pressed as shown in FIG. The capillary tube 5 may be melted and pushed into the fine hole 3 to form a plug. FIG. 5 shows the resulting state. Further, as a method for sealing, a method of forming III by sputtering or vapor deposition can also be used. Since such sealing work is carried out in a vacuum, there is no risk of non-condensable fluid such as air entering into 112, and since condensable fluid 7 is frozen, it is necessary to seal capillary tube 5 *a. Even if temporary heating is performed, it is possible to prevent the a-contractile fluid from evaporating and scattering.

Therefore, the narrow groove 2 encloses only the condensable fluid 7,
In addition, the width of the corner portion is narrow enough to generate capillary pressure, so that it is configured as a heat pipe.

The board with the above structure can be used as a monolithic IC or LSI.
In order to do this, an epitaxial layer is formed on one of the surfaces, and an oxide film is formed on that surface, and then photo-etching and diffusion are repeated by a conventional method to form a large number of elements. Also hybrid 1
In the case of G, a circuit is made by a printing method or vapor deposition Yasbuttering, etc., and then a chip is attached.

The integrated WA circuit created in this way generates heat when energized once. However, due to its heat, the heat pipe 1112
As the condensable fluid 7 inside evaporates, the vapor flows to the low temperature part of the narrow groove 2 and heats up, becoming liquefied, so the heat generated by energization is converted into SVA of the condensable fluid. transported to a cooler area. Therefore, since the amount of fluid transported as latent heat is extremely large,
In addition to providing a plurality of boards in succession to the extent that the strength of the board is not impaired, one board is connected to a heat dissipating part such as a heat dissipating fin attached to the package via an appropriate thermal connector. By tying it together, it can be cooled efficiently.

In addition, the above-mentioned fruit 1111r! In No. 4, the qAWIi had a triangular cross section, but in the present invention, the cross-sectional shape of the @groove may be any shape, as long as it has a narrow portion sufficient to generate capillary pressure.

Effects of the Invention As is clear from the above explanation, according to the method of the present invention, heating and cooling are performed by sI return, thereby making use of vacuum pressure. Ill as a fluid! ! Because sexual fluid is injected, even if the injection port is in a narrow place of several tens of micrometers,
The qfI injection process can be easily carried out without being affected by the viscosity of the target fluid or the capillary pressure at the P injection port.Also, the sealing of the microholes provided in the lid plate can be done using vacuum. Because the process is carried out inside the substrate and with the condensable fluid frozen, the micropores are sealed without the intrusion of non-condensable gases or the scattering of condensable fluid, and as a result, a high-performance heat vibrator can be placed inside the substrate. Overall, according to the method of the present invention, it is possible to obtain an integrated circuit substrate that has high thermal conductivity and can achieve high output or high performance.

[Brief explanation of the drawing]

Figure 1 is an enlarged perspective view of the narrow groove, Figure 2 is a cross-sectional view of the perforated 1IIi attached to the opening of the narrow groove, and Figure 3 is the state with the capillary tube installed and the perforated lid plate used. FIG. 4 is a schematic diagram for explaining an example of a method of sealing micropores, and FIG. 5 is a cross-sectional view of a state in which the narrow grooves are formed into a heat bath or r-p. 1...Plate material, 2...flI groove, 3...wll
l hole, 4...root, 7...condensable fluid.

Claims (1)

[Claims] A thin groove with both longitudinal ends closed is cut into a plate material for the substrate, and the open end of the narrow groove is sealed with a lid plate having micro holes, and then the plate material is heated to a predetermined temperature. The temperature operation and the cooling operation in the condensable fluid are repeated multiple times to suck the condensable fluid into the narrow groove and replace the non-condensable gas in the narrow groove with condensable fluid vapor. Furthermore, by sealing the micropores in a vacuum with the condensable fluid sucked into the microchannels frozen,
A method for producing an integrated circuit board with good thermal conductivity, characterized by forming a heat pipe in the plate material.