JP2870993B2 - Manufacturing method of superconducting wiring - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method for manufacturing a superconducting wiring, which aims to form a wiring pattern having a fine line width made of an oxide superconductor having a high superconducting critical temperature, and to form a Bi-Pb-Sr After depositing a Ca-Cu-O-based oxide high-temperature superconductor component on a substrate to be processed to form a wiring pattern, the substrate is separated from the Bi-Pb-Sr-Ca-Cu-O-based oxide high-temperature superconductor. A superconducting wiring manufacturing method is configured such that a dummy pattern composed of a conductor component is placed in a baking furnace so as to be opposed to and close to the substrate, and the dummy pattern is fired while maintaining the temperature of the dummy pattern at least higher than the temperature of the wiring pattern. I do.

[Industrial applications]

The present invention relates to a method for manufacturing a wiring pattern having a fine line width and made of an oxide superconductor having a high superconducting critical temperature.

It has been known for a long time that superconducting phenomena are exhibited for several kinds of metals, alloys, intermetallic compounds, nitrides, oxides, etc., but the superconducting critical temperature (abbreviation T _c ) for metallic elements is
Less than 10K, and Nb ₃ Ge
23.5K was the best.

However, since Bednorz and Muller discovered high-temperature superconductivity in lanthanum-barium-copper-oxygen (La-Ba-Cu-O) -based oxide ceramics in 1986, oxide superconductors with high _Tc have been found in various places. Conducting research on the development of conductors and research on the practical application of devices using them.

That is, in an information processing apparatus, particularly in a computer that requires high speed, it is extremely effective to configure the circuit wiring of the substrate on which these electronic elements that operate efficiently at low temperatures with high-temperature superconductors.

[Conventional technology]

Various compositions of oxide-based high-temperature superconductors have been discovered so far.

That is, yttrium / barium / copper / oxygen (Y-
Ba-Cu-O) system and rare earth element containing Y-Ba-Cu-O
An oxide superconductor with a _Tc of about 90 K for the system was discovered.

Then, Bi-Sr-Ca-Cu-O system showing _Tc of 100K or more,
A Tl-Ba-Ca-Cu-O system showing a _Tc of 125K has been published.

Here, as a method of forming a conductor line made of an oxide superconductor on a substrate to be processed, such as magnesia or alumina, a thin film pattern made of an oxide superconductor is formed by mask evaporation or sputtering and then fired. There is a method of changing to a superconducting phase by crystallization.

In addition, there is a method in which a conductor paste is formed by using powder of a superconducting ceramic, which is screen-printed to form a fine pattern, which is then fired and crystallized to change into a superconducting phase.

The inventors have obtained a value of 100 K or more by a method of firing superconducting ceramics and paste of a bulk sample in a study of forming a conductor wiring by the latter method.

However, a closer examination revealed that the apparent value of _Tc depends on the wiring width.

That is, those T _c according to the wiring width is reduced is reducedゝ, although the line width of up to 1.0mm shows a more T _c 100K, the T _c at which a line width less than rapidly transitions to a low.

On the other hand, a circuit board on which electronic components are mounted in an information processing device or the like requires high-density mounting, and _Tc must be equal to or higher than the temperature of liquid nitrogen (77 K) up to a fine line width.

However, Bi-Pb-Sr-Ca -Cu- with more than 100 K of T _c phase
With respect to the O film, in the conventional baking method, the characteristics deteriorate as the wiring width becomes narrower, and this measure is required.

[Problems to be solved by the invention]

Screen printing of a conductive paste made using superconducting ceramics and firing it also requires a T of 100 K or more.
A superconductor wiring showing _c can be formed, but when the line width becomes about 1.0 mm or less, T _c drops sharply, and liquid nitrogen (N
Even at the temperature of ₂ ) (77 K), it does not show a superconducting state.

 Therefore, solving this problem is an issue.

[Means for solving the problem]

The above problem is solved by depositing a Bi-Pb-Sr-Ca-Cu-O-based oxide high-temperature superconductor component on a substrate to be processed to form a wiring pattern, and then forming the substrate on the Bi-Pb-Sr- It is placed in a firing furnace so as to be opposed to and close to a substrate on which a dummy pattern made of a Ca-Cu-O-based oxide high-temperature superconductor component is formed, and is fired while maintaining the temperature of the dummy pattern at least higher than the temperature of the wiring pattern. The problem can be solved by the manufacturing method of the superconducting wiring configured as described above.

[Action]

Oxide superconductor obtained by depositing and firing superconducting components
The inventors believe that the reason why _Tc rapidly shifts to the low temperature side as the wiring width decreases is due to a shift in the composition ratio due to evaporation of a component having a high vapor pressure, among components constituting the superconductor.

That is, Bi-Pb for which the inventors are conducting research for practical use
In the -Sr-Ca-Cu-O system, the component having a high vapor pressure and having a significant effect on the characteristics is PbO, and the relationship between temperature and vapor pressure is shown in Table 1.

The temperature at which it is crystallized by firing to become a superconducting phase is
Since the temperature is around 850 ° C., the vapor pressure of PbO is high, and in this process, evaporation easily occurs and a composition deviation occurs.

In addition, the reason why the composition deviation easily occurs as the line width decreases and the _Tc sharply decreases is that the exposed area per unit volume increases as the line width decreases, and therefore the evaporation amount of PbO is large. (4) It was thought that the partial pressure of PbO due to evaporation from the surroundings including itself was low, so that the evaporation of components was not suppressed.

Accordingly, the present invention provides a method for preventing evaporation of components, as shown in the principle diagram of FIG.
The substrate 4 on which the dummy pattern 3 is printed is disposed so as to face the substrate and is baked.

Here, it is necessary to make the wiring pattern 1 and the dummy pattern 3 as close as possible.

When baking is performed in this manner, the evaporation of PbO from the dummy pattern causes the PbO from the wiring pattern 1 to evaporate.
Since the evaporation of bO is suppressed, a fine wiring pattern having a high _Tc can be formed.

When firing the printed superconducting pattern, in order to grow crystal grains, bake for a short period of time so that the evaporation of PbO does not actively occur, and then return to the original state and fire Then, a superconducting wiring in which a gap is small in a crystal grain boundary and densification of a film is promoted can be formed.

The present invention can suppress evaporation of a component having a high vapor pressure, particularly PbO, by baking the dummy patterns in close proximity to each other, as well as for a wiring having a line width of 1 mm or less.
It is possible to form a superconductor line having a _Tc similar to that of the case of mm or more.

〔Example〕

Example 1: (Formation of wiring pattern and firing furnace) Raw powders of Bi ₂ O ₃ , PbO, SrCO ₃ , CaCO ₃ and CuO were prepared, and the molar ratio of Bi: Pb: Sr: Ca: Cu was 0.7: 0.3. : 1: 1: 1.8, and the mixed powder was fired at 845 ° C. for 150 hours to produce a superconducting ceramic.

This ceramic was roughly pulverized in a mortar and then sized using a ball mill.

Terpineol is added to this powder as a viscosity modifier,
After kneading with acetone as a solvent, the mixture was dried to remove acetone, mixed with benzene, dried and adjusted for viscosity to prepare a superconducting paste.

Using this paste, a plurality of magnesia (MgO) single crystal substrates with a thickness of 0.5 mm and a thickness of 0.5 mm are prepared, on which a conductor line with a line width of 0.5 mm and a length of 10 mm and a dummy with a 10 mm square are placed. The turns were screen printed separately and dried.

 Next, a firing furnace as shown in FIG. 3 was prepared.

That is, after alumina ceramic plates 8 and 9 having heat sources (heaters) 5 and 6 behind them are inserted into a quartz glass frame 7, the alumina plates 10 and 9 are placed on the ceramic plates 8 and 9 using MgO spacers 10. As shown in the figure, the substrates 2 and 4 were arranged facing each other.

By doing so, the distance between the wiring pattern 1 and the dummy pattern was kept at 0.5 mm.

Example 2: As described in Example 1, the line width was 0.5 mm, the thickness was 30 μm,
Two MgO substrates on which conductor lines each having a length of 10 mm were printed were mounted on the firing furnace shown in FIG. 3 and were opposed to each other with an interval of 0.5 mm, and the lower conductor lines were used as dummy patterns.

Then, as shown in FIG. 1, the heat sources 5 and 6 are energized in the atmosphere,
After heating both at 860 ° C. for 10 minutes, the temperature of the upper substrate 2 was lowered to 840 ° C., while the lower substrate 4 was baked at 850 ° C. for 6 hours to change the superconducting phase. Substrate 2
The temperature dependence of the resistivity was measured for the conductor lines of FIG.

Example 3: FIG. 3 with the MgO substrate printed with a conductor line having a line width of 0.5 mm, a thickness of 30 μm, and a length of 10 mm on the top, and the MgO substrate applied with a solid pattern of 10 mm square on the bottom. Was mounted in a firing furnace as shown in Fig. 4 and opposed to each other with an interval of 0.5 mm, and the lower conductor line was used as a dummy pattern.

Then, heat is applied to the heat sources 5 and 6 in the atmosphere, and both are heated to 860 ° C.
After heating for 10 minutes, reduce the temperature of both substrates 2 and 4 to 840 ° C,
In that state, it was baked for 6 hours to change to the superconducting phase, and the temperature dependence of the resistivity of the conductor line of the upper substrate 2 was measured.

Comparative Example 1: The firing shown in FIG. 3 with the MgO substrate on which a conductor line having a line width of 0.5 mm, a thickness of 30 μm, and a length of 10 mm was printed on the top and an MgO substrate without a pattern printed on the bottom. Attach to heat source 5 and 6 in the atmosphere at 0.5mm interval,
After heating at ℃ for 10 minutes, the temperature of both substrates 2 and 4 was lowered to 840 ° C, and then baked for 6 hours to change to a superconducting phase, and the temperature dependence of the resistivity of the conductor lines of the upper substrate 2 The properties were measured.

FIG. 2 shows the results of Examples 2 and 3 and Comparative Example 1. In Examples 2 and 3, _Tc was about 98 K and about 100 K, whereas Comparative Example 1 showed a phase transition.ゝ, the residual resistance is
It is as large as 12 mΩ · cm and is not in a superconducting state.

〔The invention's effect〕

As described above, by implementing the present invention, it is possible to minimize the composition deviation that occurs in firing performed to make a superconducting phase, and thereby even when forming a fine pattern with a line width of 0.5 mm or less. Superconducting wiring with a high _{Tc that} is the same as a line width of 1 mm or more can be made.

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a diagram showing the temperature dependence of the resistivity of the embodiment, and FIG. 3 is a sectional view of a firing furnace used for carrying out the present invention. In the figure, 1 is a wiring pattern, 2 and 4 are substrates, 3 is a dummy pattern, and 5 and 6 are heat sources.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Atsushi Tanaka 1015 Uedanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Nobuo Kamehara 1015 Kamikodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited ( 56) References JP-A-1-100825 (JP, A) JP-A-1-2399051 (JP, A) JP-A-1-294560 (JP, A) JP-A-2-38302 (JP, A) ) Surveyed fields (Int.Cl. ⁶ , DB name) H01L 39/00-39/02 H01L 39/22-39/24 H01L 39/06 H01B 12/00-12/16 H01B 13/00

Claims (2)

(57) [Claims] After a Bi-Pb-Sr-Ca-Cu-O-based oxide high-temperature superconductor component is deposited on a substrate to be processed to form a wiring pattern, the substrate is removed from the Bi-Pb-Sr- It is placed in a firing furnace so as to be opposed to and close to a substrate on which a dummy pattern made of a Ca-Cu-O-based oxide high-temperature superconductor component is formed, and is fired while maintaining the temperature of the dummy pattern at least higher than the temperature of the wiring pattern. A method for manufacturing a superconducting wiring, comprising: 2. A method for manufacturing a superconducting wiring according to claim 1, wherein the dummy pattern is a wiring pattern or a solid pattern.