JPH02207589A - Oxide superconductor wiring board - Google Patents

Abstract

PURPOSE:To provide an oxide superconductor wiring board without causing operations of semiconductor and the like to be misoperated even under the existence of temporal deterioration of charcateristics thereof or of any breakdown thereof by integrally laminating an oxide superconductor layer and a stabilizing layer selected from Ag, Au, and Pt. CONSTITUTION:An oxide superconductor raw material metal compound (chiefly oxide) is weighed to a predetermined amount and mixed, a resulting mixture is calcined and ground to yield calcined powder, which is then blended with an organic solvent of an amount less than that of the calcined powder and molded under pressure into a sheet product. On the other hand, powder of Ag and Au or Pt is blended with an organic solvent and molded under pressure into a sheet product. Both sheet products are alternately laminated and dried, and thereafter compressed and united together. Thereafter, it is fired.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a wiring board made of an oxide superconductor used in semiconductor LSIs and the like.

(Conventional technology) Recent high Tc (critical temperature...temperature at which superconducting state occurs)
With the advent of superconductors, it has become possible to fully consider the application of superconductors to wiring boards for semiconductor LSIs. On the other hand, as a result of advances in miniaturization technology, the high-speed performance of semiconductor elements themselves has improved, resulting in a reduction in integrated line width, which increases wiring resistance and, in the case of wiring made of normally conducting metal, increases propagation delay time. has become a problem.

For that reason.

A superconductor with zero electrical resistance is highly expected to eliminate these problems. In proceeding with applied research, we focused on the following problems that need to be solved. In other words, the ambient temperature is the offset temperature (
When the current density exceeds the critical current density (Jc), the magnetic field in the atmosphere reaches the critical magnetic field (H
e) When the superconductor becomes larger, resistance is generated in the superconductor, causing a change in current, causing temporary disturbances in the operation of semiconductors, etc., and causing malfunctions of integrated circuits. As the line width of the wiring becomes smaller, the current density increases and the superconductor itself generates heat, destroying its superconducting properties.

(Purpose of the Invention) The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to compensate for the temporary deterioration or destruction of the characteristics of a superconductor (so-called quench), and to prevent the operation of semiconductors, etc. from being disrupted. It is an object of the present invention to provide a novel oxide superconductor wiring board that does not cause the above-mentioned problems.

(Means for Solving the Problems) An oxide superconductor wiring board of the present invention for achieving the above object includes an oxide superconductor layer and a stabilizing layer selected from Ag, Au, and Pt. The gist is that the material is laminated with two layers.

The oxide superconductor constituting the present invention includes Y-Ba-
A composite oxide represented by Cu-0 or Bi-8r-Ca-Cu-○ is preferably employed. In addition, the stabilizing layer laminated with this is a layer of a normal conducting metal and is selected from Ag, Au, and Pt, but Cu, which is a typical normal conducting metal, is dissolved in the superconducting layer and its composition varies. It cannot be used because it causes

The layer structure of the stabilizing layer and the superconductor layer may be one layer at a time, two layers at a time, or multiple layers at a time. It is selected as appropriate depending on the specifications of the target integrated circuit, etc.

Next, two desirable examples of the method of laminating the above-mentioned monolithic layer will be briefly described.

First method> Predetermined amounts of raw metal compounds (mainly oxides) for the oxide superconductor are weighed and mixed, this mixture is calcined and pulverized to obtain a calcined powder, and the calcined powder is mixed with an organic solvent. Knead to make a paste. On the other hand, powders of Ag, O, Ag, Au, or Pt are kneaded with an organic solvent to form a paste, and both pastes are printed on a substrate such as zirconia, dried, and then fired.

In this case, the thickness of the single layer of calcined powder paste layer can be selected as appropriate depending on the size of the target wiring board, required performance, etc., as long as its characteristics are expressed. The thickness of the single paste layer is preferably 1710 to 2 times the thickness of the single calcined powder paste layer. This is because if it is less than 1/10 times, the specific resistance at room temperature increases and the cooling effect cannot be sufficiently exerted, and if it exceeds twice, the critical current density (Jc) tends to decrease.

<Second method> A predetermined amount of raw metal compounds (mainly oxides) for the oxide superconductor is weighed and mixed, this mixture is calcined and pulverized to obtain a calcined powder, and the calcined powder is It is kneaded with a small amount of organic solvent and compression molded to form a sheet. On the other hand, Ag, O1A
Powder of g, Au or Pt is kneaded with the same organic solvent and compression molded to form a sheet. Both sheet-like materials are layered alternately, dried, compressed into a single piece, and then fired. In this case, the thickness of the superconductor powder molded sheet layer is not limited as described above, but the thickness of a single layer of the molded sheet layer of Ag, 0 powder, etc. is 0.1 to 2 times the thickness of the superconductor powder molded sheet layer. This is desirable because outside this range, the same tendency as above will occur.

(Function) The wiring board having the above structure is configured as a semiconductor module or the like by forming a wiring circuit as appropriate by, for example, a printing method or etching a thin film, mounting a semiconductor element or the like at a predetermined position, and then performing wire bonding. The semiconductor module and the like are then used while being maintained at a temperature below the Tc temperature of the superconductor. In this state of use, the electrical resistance of the superconductor layer becomes zero, so even if the semiconductor element itself has high-speed performance, the signal current propagates at a speed that is sufficient to accommodate the high-speed performance of the semiconductor element itself. For example, the ambient temperature temporarily becomes offset temperature (Tea) due to a decrease in refrigerant.
or more, when a current larger than the critical current density (Jc) flows, or when the magnetic field of the atmosphere becomes larger than the critical magnetic field (He).

Although the superconductor layer causes quenching, the stabilizing layer interposed within the layer performs the current propagation function instead. Although the propagation speed of the stabilizing layer is lower than that of the superconductor layer, it can sufficiently compensate for the temporary delay. also,
The heat dissipation effect of the stabilizing layer suppresses the heat generation of the superconductor layer itself due to an increase in current density, thereby preventing destruction of the superconducting properties. Therefore, even if the superconductor layer is temporarily quenched due to external factors or the current density increases,
Adverse effects on semiconductor elements and the like are avoided, eliminating concerns about malfunctions and the like.

(Example) Next, examples will be described.

(Example-1) (1) Y203 powder 30.26g, BaCO3 powder 10
After weighing and mixing 5.78 g and 17.34 g of CuO powder, they were calcined at 880°C for 5 hours, crushed in an agate mortar, further calcined at 920°C for 20 hours, and crushed to have an average particle size of 1.6 μm.
A calcined powder was obtained.

The obtained calcined powder was confirmed by X-ray diffraction to be a crystal having a composition formula of Y I B a 2 Cu 307-5.

(it) 20 to 35% by weight of ethyl cellulose as an organic solvent was added to the above calcined powder and mixed well to form a paste.

(ni) 15 to 25% by weight of ethyl cellulose as an organic solvent was added and mixed to AgzO powder to form a paste.

(iv) Two layers of the above Ag2O powder and calcined powder paste were alternately printed and laminated on a zirconia substrate.

The layer thickness of each layer is fixed at 80 μm for the calcined powder paste layer, 40 μm for the Ag, O powder paste layer, 160 μm, and 1
They were 65 μm, 8 μm, and 7.2 μm. These were designated as Examples 1-1.1-2.1-3.1-4 and 1-5, respectively.

(v) After thoroughly drying the laminate, it was fired in a resistance heating tubular furnace. The firing conditions were to raise the temperature from room temperature to 950°C at a rate of 50°C/hr while flowing oxygen gas, and after holding at the maximum temperature (950°C) for 5 hours.

It was cooled to 600°C at a rate of 50°C/hr, held for 5 hours, and then cooled to room temperature at a rate of 50°C/hr.

<Comparative Example> As a comparative example, a bulk body in which the superconductor calcined powder was fired as it was under the same conditions as above, and a bulk body in which only the above superconductor calcined powder paste (thickness, 80 μm) was fired under the same conditions were prepared. These were designated as Comparative Examples 1-1.1-2, respectively.

(Example-2) (i) Bi, O, powder 45.29g, 5rCO, powder 2
9.07g, CaC0, powder 9.80g, CuO powder 1
After weighing and mixing 5.84 g, calcined at 800°C for 5 hours,
The mixture was ground in an agate mortar and further calcined and crushed at 820°C for 20 hours to obtain calcined powder with an average particle size of 5 μm. The obtained powder was confirmed to be a crystal having a composition formula of Bi25r2Ca1Cu208 by X-ray diffraction.

(ii) In the same manner as in Example-1, the above calcined powder was made into a paste form (thickness, 80 μm), and the Ag2O powder was also made into a paste form (thickness, 40 μm), and two layers of these were alternately placed on a zirconia substrate. It was printed, dried and fired. For firing, the temperature was raised from room temperature to 840°C in the air at a rate of 50°C/hr, held at the maximum temperature (840°C) for 5 hours, and then cooled to room temperature at a rate of 50°C/hr. The sample thus obtained was designated as Example 2-1.

(it) The composition of the superconductor layer is Bi:Pb:Sr:Ca
:Cu=2:0.5:2:3:4 and prepared in the same manner as above to obtain a calcined powder, which was used to stack and fire in the same manner as above. For firing, the temperature was raised to 840°C in the air at a rate of 50°C/hr, and the maximum temperature (840°C
) for 200 hours, and then cooled to room temperature at a rate of 50"C/hr.

The sample thus obtained was designated as Example 2-2.

The calcined powder used at this time was determined by X-ray analysis to be 110
It was almost a single layer.

<Comparative Example> As a comparative example, only a calcined powder paste (thickness, 80 μm) corresponding to Example 2-1.2-2 was calcined under the same conditions. Comparative Example 2-1.2-
It was set as 2.

The composition of each fired sample obtained above was observed using a SEM (scanning electron microscope). In addition, this sample was crushed and subjected to XRD measurement. The resistance change with respect to temperature was investigated using the four-probe method, and the onset temperature (Tea) and offset temperature (Tce) were measured. Furthermore, the current density was measured in the following manner. That is, according to the four-terminal method, the sample is immersed in liquid nitrogen, and when the temperature has stabilized, a current is started to flow, and the value is gradually increased, and the current value when the voltage suddenly occurs and is 1 μV is taken as Ic, The value divided by the cross-sectional area was defined as the critical current density Jc. Furthermore, the specific resistance of each sample at room temperature was measured. These results are shown in Table 1.

(Left below) From the SEM and XMA results for Example 1-1.2.3.4.5 and Example 2-1.2, some silver diffused and existed between the grains of the superconductor. I found out that there is. They also had good wettability with the superconductor particles and were in a state of covering the superconductor particles.

Furthermore, from the XRD analysis results, it was observed that the superconductor and Ag peaks coexisted, and it was therefore inferred that Ag was not solidly dissolved or substituted in the superconductor layer.

In the measurement results of resistance change with respect to temperature, Comparative Example 1-1, which is an ordinary bulk body, and other comparative examples both have a resistance of 10'' to 101 orders of magnitude mΩ/d at room temperature, whereas Example 1-1.2, 3.4 and Example 2-1.2
are all 10<-3 >order mΩ/d at room temperature, which suggests that even if the superconducting layer is quenched, sufficient temporary compensation is possible. The reason why the specific resistance of Examples 1-5 was high is considered to be because the thickness of the Ag layer was so small that it could no longer exist as a layer due to its diffusion. There was no significant difference in either offset temperature or onset temperature.

The critical current density of Example 1-1.2.4.5 is the same as that of Comparative Example 1.
-1.2, and it is understood from the comparison between Example 1-1 and Comparative Example 1-2 that the increase is caused by laminating the Ag layer. Example 2-1.2
This tendency can also be seen in the comparison between Comparative Example 2-1.2 and Comparative Example 2-1.2. The reason why the critical current density of Example 1-3 is low is because of Ag.
This is thought to be because the layer was too thick and the edges of the sample were covered by the Ag layer.

(Example-3) (i) Same as Example-1, the composition formula is Y1Ba2C
A calcined powder of u3O7,9 was obtained.

(ii) To this calcined powder, 7% by weight of an acrylic copolymer was added as an organic solvent and mixed well.

(in) 7% by weight of an acrylic copolymer was added as an organic solvent to the AgzO powder and mixed well.

(~) The above-mentioned calcined powder mixture and Ag2O powder mixture were compression molded to form sheets with thicknesses of 80 μm and 40 μm. Two layers of each of the above-mentioned sheet-like materials were stacked alternately, and after being thoroughly dried, they were passed through a roll-shaped continuous compression molding machine and pressed together. The crimped product was cut into strips of 10 x 25 m, and heated in a resistance heating tubular furnace with oxygen gas flowing from room temperature to 50 m.
C) Raise the temperature at 25 °C/hr to C, and from 500 °C to 9
The temperature was raised to 80°C at a rate of 200°C/hr, held at the maximum temperature for 10 minutes, and then cooled to room temperature at a rate of 10°C/hr. The fired sample thus obtained was designated as Example 3-1.

(v) The thickness of the calcined powder mixture sheet is 5 μm; 4.
5 μm, thickness of Ag, O powder mixture sheet 5 μm, 4
．． The samples having a thickness of 5 μm were laminated in the same manner as above, subjected to continuous compression molding, and then fired to prepare four types of samples, which were designated as Examples 2, 3, 4, and 5, respectively.

For each of the above samples, the composition was observed by SEM, and the ground sample was subjected to XRD measurement.

In addition, in the same manner as above, resistance change with respect to temperature, onset temperature, and offset temperature were investigated, and critical current density was measured. Furthermore, the degree of orientation (f value) was calculated based on the surface X-ray diffraction peak based on the following formula.

f=(P-Po)/(1-Po) where P(oriented sample)=ΣI(OOQ)/(Σx(hku)+
Σ■(ooQ))
/ (Σx'(hku)+Σx'(oon)) These results are shown in Table 2.

(The following is a blank space) As with the samples of Example 3, it was found from the SEM and XMA results as above that some of the silver was diffused and present in the grain boundaries of the superconductor. They also had good wettability with the superconductor particles and were in a state of covering the superconductor particles. Furthermore, from the XRD analysis results, it was observed that the superconductor and Ag peaks coexisted, and it was therefore inferred that Ag was not solidly dissolved or substituted in the superconductor layer.

Furthermore, the specific resistances at room temperature are all low, which suggests that even if the superconducting layer is quenched, temporary compensation is sufficiently possible.

It is understood from the f value that all of them have highly oriented structures. It can be seen that the critical current density was extremely high except for Example 3-2.3, indicating that the samples had excellent superconducting properties. This is related to the above-mentioned orientation, and it is thought that the compressive action during sample preparation improved the orientation of the crystals, which caused the increase in current density, and can be ranked as a noteworthy effect of this example. I can do it. Example 3-2.3
The reason for the low critical current density is thought to be that the superconducting properties were not fully expressed due to the thin layer thickness of the superconducting layer.

In the above embodiment, an example was shown in which Ag was used as the stabilizing layer, but the inventor has confirmed that similar results can be obtained with Au and Pt. In this case, Au and Pt were used directly since they do not have oxides. Further, an oxide of Ag is more economically advantageous because it is chemically stable and cheaper, but the use of Ag as it is is not excluded.

(Effects of the Invention) As mentioned above, the superconductor wiring board of the present invention has a superconductor layer and a stabilizing layer made of a normal conductive metal laminated in a sintered unit, and the superconductor layer is Even if the current is temporarily quenched due to the above reasons, the current propagation function is maintained due to the stacking effect, and therefore, even when applied to semiconductor LSI wiring boards, etc., adverse effects on semiconductors are avoided and there is no fear of malfunction. Furthermore, even if the line width is forced to decrease due to higher integration, heat generation in the superconductor layer is suppressed by the cooling effect of the stabilizing layer, and the original characteristics of the superconductor layer are maintained.

The present invention, which has such remarkable effects, greatly contributes to opening up prospects for the practical application of superconductors, and its usefulness is extremely large.

-And more-

Claims (1)

[Claims] 1. An oxide superconductor wiring board formed by integrally laminating an oxide superconductor layer and a stabilizing layer selected from Ag, Au, and Pt.