JPS6376464A - Thin film cooling apparatus - Google Patents

Abstract

PURPOSE:To manufacture a miniaturized and highly efficient thin film cooling apparatus suitable for cooling down a fine objective device to be cooled down by a method wherein the metallic thin film in high Seebeck coefficient takes the shape bent zigzag to diminish the projecting length in the lateral direction from the junction part on the exothermic side. CONSTITUTION:Conductive electrodes 11 comprising a metal in low Seebeck coefficient are junctioned at both ends in the long direction of a metallic thin film 12 formed of a metal in high Seebeck coefficient on a substrate 10 while both electrodes 11 are supplied with direct current to cool down a device to be cooled down arranged at a junction part 15 on the endothermic side by means of making one junction part 16 haet generating while the other junction part 15 endothermic. The metallic thin film 12 in such a device is bent zigzag at specified interval in the long direction to diminish the projecting length zigzag in the lateral direction as approaching from the junction part 16 on the exothermic side to the junction part 15 on the endothermic side. For example, the conductive electrodes 11 comprising Cu and the metallic film 12 comprising Bi taking said shape are formed on a sapphire substrate 10 furthermore an Al2O3 film 13 is formed to provide the device 14 to be cooled down thereon.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a thin film made of a metal with a relatively large Seebeck coefficient, which generates heat, absorbs heat, and absorbs heat due to the Peltier effect, so that the heat-absorbing side joint of the thin film is produced. 1: This invention relates to a thin film cooling device that efficiently cools a minute object to be cooled, such as an IC (semiconductor integrated circuit) device.

[Conventional technology]

Conventionally, as a Peltier element that generates heat and absorbs heat using the Peltier effect of a thermoelectric material, there is a bulk type 4111 as described in "Semiconductor Engineering" by Takahashi, Houka Publishing, 19751, line F-8, p. 225. There is.

As stated in the above literature, the conventional Peltier element is a bulk type, and the thermoelectric material that produces the Peltier effect is
V-VI group compound semiconductors such as Bi2Te3 (bismuth telluride) or Bi25t)3 (bismuth antimonide) have been used.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not give consideration to the realization of a microcooling element intended for cooling microscopic objects such as IC devices and thin-film magnetic heads. That is, in the prior art, V-VI group compound semiconductors such as B12Te3 and Bi25bs are used as thermoelectric materials, and when attempting to reduce the thickness of the Vertier element, there are problems as described below.

1) Since compound semiconductors are multi-component systems, compositional fluctuations occur during thinning, making composition control difficult.

2) In a thin film state, it is difficult to obtain desired performance because the crystallinity is inferior to that in a bulk state.

3) To deal with this, it is possible to use metal as the material for the Peltier element and form it into a thin film, but if it is used in the form of a strip-shaped metal thin film, the thermal conductivity is high, There is little heat dissipation effect to the outside, and cooling efficiency is poor.

It is known that the performance of IC devices, thin-film magnetic heads, etc. improves by lowering the environmental temperature. It is requested. IC devices and the like are currently becoming more miniaturized and are progressing towards ultra-small systems. If a conventional bulk-type Bertier element is used for such an object to be cooled, the cooling system will become a large building, going against the trend toward a super-small system.

An object of the present invention is to solve the above-mentioned problems in the prior art, and to provide a thin film cooling device that is suitable for cooling minute objects, has a small structure, and is highly efficient. .

[Means for solving problems]

The above purpose is achieved by using a metal with a relatively large Seebeck coefficient as a material that causes the Peltier effect, forming it into a thin film, and making the shape of this metal thin film easy to dissipate heat, especially on the heat generating side. , achieved.

More specifically, in the present invention, conductive electrodes made of a metal with a smaller Seebeck coefficient are connected to both longitudinal ends of a metal thin film formed of a metal with a larger Seebeck coefficient on a substrate, and a direct current is applied between the two electrodes. The structure is configured to cause heat generation in one joint part and absorption of heat in the other joint part by flowing water to cool a minute object to be cooled disposed at the heat absorption side joint part,
The shape of the metal thin film is bent in a zigzag manner at regular intervals in the longitudinal direction, and the protruding length of the zigzag folds in the lateral direction gradually increases from the heat-generating side joint to the heat-absorbing side joint. This problem is attempted to be solved by shortening the length.

The operating principle of the Beltier element will be explained using FIG. FIG. 3 is a cross-sectional view of a conventional Vertier element, in which 31 and 31 are conductive electrodes made of metal, 32 are thermoelectric materials that produce the Peltier effect, for example, n-type or p-type semiconductors, 33 and 34 is the junction between the conductive electrode and the thermoelectric material. Further, the arrow 1 indicates the direction in which the direct current flows. When the thermoelectric material 32 is a P-type semiconductor, the joint 33 is on the heat absorption side and the joint 34 is on the heat generation side. The heat absorption tQ at the heat-absorbing side joint is equal to the amount of heat generated at the heat-generating side joint.

The limit temperature of the cold part in the Beltier element is the amount of heat absorbed Q,
It is determined by the relationship between the amount of heat propagated by heat conduction from the heat-generating side joint and the Joule heat generated by the element itself, and these relationships are generally evaluated by the figure of merit Z. Performance index 2
is defined by the formula +11.

2=α/(K・ρ) ・Old...(11Here, α
is the Seebeck coefficient, K is the thermal conductivity, and ρ is the specific resistance.

Table 1 shows d1ρ and Z of main materials for Peltier elements.

As shown in Table 1, the figure of merit 2 of semiconductor materials is one to two orders of magnitude higher than that of metal materials.

The reasons for this are that metal materials (1) have a smaller Seebeck coefficient α and (2) have a larger thermal conductivity k.

In particular, regarding thermal conductivity, metal materials are about an order of magnitude higher than semiconductor materials. Therefore, by reducing the thermal conductivity evenly and sparingly, a significant improvement in the figure of merit can be expected, and it is expected that a Vertier element with a cooling capacity comparable to that of semiconductor materials can be realized using metal thin films. . Furthermore, when forming an ε bimetallic thin film on a substrate,
It is a well-known fact that there is no problem of compositional fluctuation mentioned above and that a thin film with better crystallinity than semiconductor materials can be formed.

[Effect]

The main points of the present invention are a structure in which a metal thin film formed on a substrate is used as a Vertier element, and the shape of this metal thin film is optimized to improve heat dissipation efficiency in the path from a high temperature part to a low temperature part. The point is to increase the cooling effect of In order to improve heat dissipation efficiency, the basic concept of the shape configuration of the metal thin film adopted in the present invention is shown in Fig. 4 (a) and (b).
Explain using. In FIG. 4, 41 is a thin film conductive electrode made of a metal material with a smaller Seebeck coefficient, such as Cu (copper), and 42 is a metal material with a larger Seebeck coefficient, such as Cu (copper), which generates heat and heat absorption due to the Peltier effect. Metal thin film formed of Bi (bismuth), 4
5 and 44 are joint portions between the conductive electrode 41 and the metal thin film 42, respectively. When a current 1 is passed in the direction of the arrow by a DC power source, in the case of a combination of Bi and Cu, the joint 43 becomes the heat absorbing side and the joint 44 becomes the heat generating side. ! In the temperature distribution shown in Figure J4 (b), the horizontal axis indicates the position on A7A' in Figure (a), and the vertical axis indicates the temperature. The dashed line temperature is room temperature,
The upper part is high temperature and the lower part is low temperature. The joint portion 44 on the heat generating side has the highest temperature, and the joint portion 43 on the heat absorbing side has the lowest temperature. The temperature distribution along the way is a distribution that decreases linearly as shown in the figure. In reality, heat inflow from the outside, heat generated by the Joule heat of the metal thin film 42 itself, etc. are involved, and the temperature distribution becomes even more complicated.

In the Bertier element, these heat generation and heat absorption are intricately related, and the current 1 flowing through the element is related to the temperature ΔT between the heat-generating side joint 44 and the heat-absorbing side joint 43. Therefore, in order to lower the temperature of the heat-absorbing joint 43, it is first necessary to lower the temperature of the heat-generating joint 44 and the metal thin film 42 in its vicinity as much as possible to keep it close to room temperature.

For this reason, in the present invention, in the path from the heat generating side joint 44 to the heat absorbing side joint 43, the shape of the metal thin film is bent in the vicinity of the heat generating side joint with a large lateral protrusion length. By creating a structure in which the lateral protrusion length of the folds decreases as it approaches the joint on the heat absorption side, the heat dissipation efficiency on the heat generation side is improved, and conversely, on the heat absorption side, the structure is such that it does not dissipate much heat. .

〔Example〕

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

(Example 1) FIG. 1 shows a first example of the present invention, in which (a) is a plan view and (b) is a sectional view taken along line A-A'. In Figure 1, 10 is 8-sided sapphire used as a substrate, 11 is C
12 is a metal thin film (thickness: 4 μm) made of B1, and 15 is At20.0 for electrical insulation. (aluminum oxide) film (thickness: 1
μm), 14 is the device to be cooled, 15 is the heat absorption side junction,
16 is a heat generating side joint portion. The B1 film and the Cu film were formed by vacuum evaporation, and the At203 film was formed by Brehner magnetron sputtering considering that the melting point of the B1 film was 271°C. Further, patterning of each part was performed using a normal photoetching technique.

As shown in FIG. 1 (11), the B1 film is patterned in a zigzag shape, and furthermore, the length of the zigzag shape's protrusion in the lateral direction is from the heat-generating side joint 16 to the heat-absorbing side joint 15. As it gets closer, it becomes smaller, and this prevents heat from flowing from the heat-generating side joint 16 to the heat-absorbing side joint 15, and also prevents the heat from flowing into the heat-absorbing side joint 15 due to the heat generated by the electrical resistance of the metal thin film 12 itself. It can also be stopped.

At the heat-generating side joint 16 and its vicinity, it is necessary to dissipate the heat generated by the Berté effect and the heat generated by the electrical resistance of the metal thin film 12 itself. On the other hand, the heat absorption side joint part 15
Since it is cooled by the endothermic action due to the Peltier effect, heat inflow from the outside and heat inflow from the heat generating side joint portion 16 occur, causing a decrease in cooling efficiency. Therefore, in order to improve the heat dissipation efficiency near the heat-generating side joint 16, the metal thin film 12 is made into a larger serpentine shape, and as it approaches the heat-absorbing side joint 15, the serpentine fold becomes smaller. It is straight to eliminate heat inflow.

By adopting the structure of this embodiment, the temperature of the low-temperature part is lower than that when the metal thin film 12 is formed into a linear uniform pattern.
Improved by 0℃.

(Example 2) Figures 2 (a) and (b) show 1!42 examples of the present invention.
Explain using. (a) is a plan view, (b) is its A
-A' cross-sectional view is shown. The difference between this embodiment and the first embodiment is that at least the lower surface of a portion of the zigzag pattern portion near the heat generating side joint portion 16 is provided with an electric insulating layer interposed therebetween.
It is provided with a heat dissipation thin film 17 made of a material with good thermal conductivity. As the electrical insulating layer, the same At205 film 13 used on the lower surface g of the cooled device 14 can be used. As the heat dissipation thin film 17, a Cu film can be used.

As described in the first embodiment, it is effective for the cooling device to further enhance the heat dissipation effect in the vicinity of the heat-generating side joint 16, and to insulate the vicinity of the heat-absorbing side joint 15 as much as possible. Therefore,
In this embodiment, an At20s film 13 is provided on the lower surface side of the zigzag pattern on the side nearer to the heat generating side joint 16 from approximately midway between the heat generating side joint 16 and the heat absorbing side joint 15. A thin film 17 is then formed. Adopting a Cu film as the heat dissipation thin film 17 is convenient because the heat dissipation thin film 17 can be formed at the same time when the conductive electrode 11 is formed of Cu.

By adopting the configuration of this example, an improvement effect of 15° C. in the temperature of the low-temperature portion was observed as compared to the first example.

As described above, in the embodiments of the present invention, B1 is used as the constituent material of the metal thin film that causes the Peltier effect, and Cu is used as the constituent material of the conductive electrode.
Although the present invention has been described as using Bi as a constituent material,
Needless to say, it is effective for materials other than ' and Cu.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to provide a thin film Peltier element using a metal material, and the cooling device has a microstructure compared to a cooling device using a conventional bulk type Peltier element. In particular, it is possible to provide a cooling device with high cooling efficiency for cooling minute objects such as IC devices.

[Brief explanation of the drawing]

! Figure J1 is an embodiment of the present invention, (a) is a plan view, (b)
) is an A-A' sectional view of the same, FIG. 2 is a diagram of another embodiment of the present invention, (a) is a plan view, (b) is an A-A' sectional view, and FIG. 3 is a conventional bulk type. Cross-sectional view of a Peltier element, ′!
Figures i & 4 are explanatory diagrams of the principle of the thin film Peltier element in the present invention, (a) is a configuration diagram, and (k,) is a temperature distribution diagram. Explanation of symbols> 10... Substrate (sapphire) 11... Conductive electrode (
Cu ) 12-=-metal thin film (Bi) 15-A
t205 film 14... Cooled device 15...
Heat-absorbing side joint 16... Heat-generating side joint 17...
・Thin film for heat dissipation 1 Diagram 16・・Issuing bond item (Agai! 12 Diagram (α)

Claims (1)

[Claims] 1. Conductive electrodes made of a metal with a smaller Seebeck coefficient are bonded to both longitudinal ends of a thin metal film made of a metal with a larger Seebeck coefficient on a substrate, and a direct current is passed between the two electrodes. This device cools a device to be cooled placed at the heat-absorbing joint by causing heat to be generated at one joint and heat absorption at the other joint, and the shape of the metal thin film is folded at regular intervals in the longitudinal direction. What is claimed is: 1. A thin film cooling device characterized in that the thin film cooling device is bent in a shape, and the protruding length of the zigzag folds in the lateral direction is gradually shortened from the heat generating side joint portion to the heat absorbing side joint portion. 2. A patent claim characterized in that the metal thin film is a metal thin film that is provided with a heat dissipating thin film made of a thermally conductive material on at least a portion of the lower surface near the heat-generating side joint with an electrical insulating layer interposed therebetween. The thin film cooling device according to item 1.