JPH02322A - Manufacture of superconducting device - Google Patents

Abstract

PURPOSE:To cool and form a superconducting device containing a semiconductor device not at a room temperature by selectively forming a mask on an oxide superconductive thin film, and eliminating the oxide superconductive thin film on the region where the mask is eliminated, by using active bromine. CONSTITUTION:Bodies 10-1, 10-2, in which thin oxide films of superconductive material are formed, are mounted on substrate holders 10'-1, 10'-2, and arranged in a plasma generating space 31 from a gate valve. The entirety of them is vacuumized by a turbo-molecular pump 26 and a rotary pump 14. Bromine is introduced in a plasma system generating region through a gas system 17. Microwave is applied from outside. In order to generate electron cyclotron resonance of a specified magnetic field by water cooling 28, 28' of magnets 15, 15', high density plasma is generated in the plasma generating space 31 by applying magnetic field from magnets 15, 15'. Active bromine ion reaches the surfaces of the bodies 10-1, 10-2, and the part which is not covered by a mask is etched.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for manufacturing a superconductor device using a ceramic superconducting material (also referred to as superconductivity, herein referred to as superconductivity). The present invention relates to a superconductor device, in particular, in order to form part or all of the interconnections of a semiconductor device with a superconducting material, superconducting electrodes and
By selectively removing unnecessary regions other than leads etc. by an etching method using active bromine, particularly preferably by a plasma etching method using bromine, the superconducting device can be removed for 70 minutes.
It is intended to operate at high speed at a temperature of ~100K, preferably 77K or higher.

[Conventional technology J Conventionally, superconducting materials are Nb-Ge based (e.g. Nb5Ge)
The use of metal materials such as wire rods was limited to superconducting magnets.

Furthermore, it has recently been known that ceramic materials can exhibit superconductivity. A method of forming a thin film of this ceramic material has been developed. However, although etching such a thin film with an acidic aqueous solution has been known, a vapor phase etching method has not been proposed.

This is because this oxide superconducting material cannot be plasma etched using fluorine-based gas using NF, CF4, etc., and the method of patterning this thin film using photolithography technology is also difficult. It is also completely unknown that it can be used as part of wiring.

"Conventional Problems" In recent years, semiconductor integrated circuits have become increasingly finer and are required to operate at higher speeds. Further, with miniaturization, problems have arisen in that reliability is lowered due to heat generated by semiconductor elements and operating speed of the heat generating portion is lowered.

Therefore, if a semiconductor device is operated at liquid nitrogen temperature, the mobility of electrons and holes in the device can be increased 3 to 4 times compared to that at room temperature, which in turn improves the frequency characteristics of the device. can.

In order to solve this problem, there have been attempts to make the lead wire of a superconductor device made of a superconducting ceramic material. However, such oxide ceramic superconducting materials
Hitherto, no means for performing plasma etching for microfabrication, particularly anisotropic etching, has been known.

"Means to Solve the Problem" In order to solve the problem, the present invention aims to solve the problem at extremely low temperatures (2
The present invention relates to a method for microfabrication of oxide superconducting ceramic materials exhibiting superconductivity at temperatures between 0 and 100°C, preferably above 77°C. For this reason, the present invention relates to a method for generating active bromine to etch away the oxide superconducting material in areas other than those having a masking effect. In particular, for example, compounds of copper and groups Ua and ma of the elements of the periodic table of oxide superconducting materials are removed by gasifying them as bromides of these elements. Therefore, in order to make active bromine, EC
Bromine or bromide gas was turned into plasma or photoexcited by a photoexcitation method using R (electron cyclotron resonance), RIE (reactive ion etching), or the like.

In the present invention, an oxide superconducting thin film is coated on a blocking film on a substrate (a film that does not react with oxide superconductors such as zirconium oxide or platinum even at 500 to 700°C).
．． It was formed with a thickness of 1 to 10 μm. The oxide superconducting material in unnecessary areas other than the areas that will become part of the electrodes, leads, etc. was removed by etching. A semiconductor, particularly preferably a heat-resistant semiconductor such as a single crystal silicon semiconductor substrate, is used as the substrate material, and a plurality of elements such as an insulated gate field effect transistor, a bipolar transistor, and a 5IT (static induction transistor) are formed on this semiconductor. ), resistor, and capacitor.

The present invention provides an insulating film having a blocking effect on these (typically zirconium oxide, YSZ (yttrium stabilized zircon), yttrium oxide, strontium titanate) or a conductive film for blocking the electrode part (typically A film whose main components are platinum, gold, silver, tungsten, and titanium is provided, and an oxide superconducting material with an electrical resistance of zero or close to zero is formed on this film. This is selectively etched and patterned using photolithography technology to function as a lead or the like. This etching is performed by anisotropic plasma etching using bromine. Furthermore, by performing thermal annealing at 500 to 1 ooo'c in an oxidizing atmosphere such as oxygen or active oxygen for a long time of 1 to 20 hours before or after the process, the ceramic material can be made to exhibit superconductivity at extremely low temperatures. Modify the crystal structure of. By repeating these steps one or more times, IJ
i or the interconnections in each layer are formed of a material with zero electrical resistance.

In the present invention, when performing plasma etching, the melting point (MP) and boiling point (BP) of these etched compounds were investigated. In particular, fluorine-based (F-based) halogen elements, which are often used in the manufacturing process of semiconductor integrated circuits.
and chlorine-based (Cl-based). Bromine (Br-based) has never been used in semiconductor integrated circuits, and it would be revolutionary if fine patterns could be created using gases such as bromine. These relationships are shown in the table below.

Br-based Cl-based F-based Y (yttrium) YBrz YCl3 YF3MP 9
04°C 680°C 1200°C or more BP 904°C
/2mm11g 1507°C 1500°C or more Sr
(Strontium) SrBrz 5rCI2 SrhMP
643°C873°C1190°CBP
? ? 2460°CBa (barium) BaBr, BaC12BaF.

MP 847°C963°C1280°CBP
? 1560°C2137°CCa
(Calcium) CaCI2 MP 765°C BP 810°C Cu (Copper) CaCI CaFz 772°C1360°C >1600″C2451°C CuBr2 CLICI2 CuFz498°
C498°C780°C 900°C993°C950°C CuBr CuCl CuF504
'C422°C2 1345°C1366°C? Bi (Bismuth) 1Brz BiBrz MP 218°C BP 453°C B1C1+ Bih 230°C Approx. 725°C 447°C? As is clear from this, oxide superconducting materials such as YBa
zCu,,O,,”'a+Ysrzcu306~a,Y
BaSrCu, 0. ,-e.

Regarding Big(SrCa)2CuzOa ~to etc., B
r compounds are elements for oxide superconducting materials such as Y (yttrium), Sr (strontium), Ba (barium), bismuth (Ca), and Cu (copper).
904°C (melting point of YBr3) or 76°C
It can be melted at temperatures higher than 5'C (melting point of CaBrz).

When using chlorine, 963°C (melting point of BaC1□)
Alternatively, it can be melted at 873°C (melting point of SrCLz) or higher.

However, F and the like can only be melted at temperatures as high as 1360°C (melting point of Ca) or higher. From these results, it can be seen that Br can be melted at the lowest temperature possible. Generally, the lower the melting temperature, the more likely it is to become a gas under reduced pressure or in a vacuum. Therefore, materials with a lower melting point react with the plasma of F, C1, and Br and easily cause the compound to fly off as a gas. Furthermore, I (iodine) is expensive and difficult to put into practical use.

In addition, in these F, CI, and Br, the reaction vessel is -
Since it is made of stainless steel, F and 8r do not react with them.

CI is also dangerous to handle as it emits a very strong pungent odor and reacts with the stainless steel reaction vessel.

Considering these things comprehensively, the Br system has great practical advantages in that it is inexpensive, can be done manually, is safe, and is easy to maintain the equipment.

``Operation'' Thus, by using the plasma etching method with bromine or bromides, it was possible to use oxide superconducting materials for some or all of the leads of a superconductor device.

When such a semiconductor device is operated at liquid nitrogen temperature, its electron or hole mobility can be improved three to four times. In addition, it becomes possible to make the electrical resistance of the leads and electrodes zero or equal to zero. R (resistance) in the CR time constant, which indicates a delay in frequency characteristics, can be made zero, and therefore extremely high-speed operation is possible.

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

``Example 1'' FIG. 1 shows a magnetic field microwave plasma etching apparatus used in the present invention.

In the figure, this device includes a plasma generation space (31) that can be maintained at atmospheric pressure or a reduced pressure state, and an auxiliary space (12).
, an electromagnet (15), (15') that generates a magnetic field and its power source (35), a microwave oscillator (14), a vacuum pump (26) constituting the exhaust system, and a rotary pump (24).

Pressure adjustment valve (19), substrate holder (10'-1)
, (10'-2).

Substrate (10-1), (10-2), film forming object (10), microwave introduction window (39), gas system (16)
, (17), water cooling system (28).

(28°).

First, objects (10-1), (10-2) on which a thin film of oxide superconducting material is formed on a substrate to be etched.
) are installed on the substrate holders (10''-1) and (10'-2), and the plasma generation space (31
).

In this example, the substrate is a MgO, 5rTi (h or YSZ substrate) having a (100) or (110) plane, or a YBa2Cu30. , ~
A substrate on which an oxide superconducting material having the structure No. 8 was formed to a thickness of 2 μm was used. This board holder (10'-1),
(101°-2) and the reaction system were made of stainless steel in order to avoid disturbing microwaves and electromagnetic waves as much as possible.

Reactive gases with bromine, such as Brz (MP-7,
3'C, BP 58.78°C) mixed liquid (32
) are mixed and sealed in the bubbler (33). In the case of a gas phase method, this liquid (32) may be bubbled with nitrogen (17) or the liquid may be brought under reduced pressure or less and discharged into the reaction space from (34).

In the etching process, the substrate is first formed into a holder, and then the entire structure is evacuated to a pressure below I.times.10-btorr using a turbo molecular pump (26) and a Rotagoo pump (14). Next, an etching gas (a gas that does not constitute a post-decomposition reaction body), for example, bromine (6), is added at 200 SC.
It is introduced into the plasma generation region (1) through the CM gas system (7), and the pressure is set to 0.003 torr. Microwave of 500MIIz or more from outside, for example 2.45Gt
Microwaves with a frequency of lz are applied at an intensity of 0.1 to I KW, for example 0.5 -. Magnet (15), (
15') and water-cooled (28).

A magnetic field (15) and (15') is applied to generate electron cyclotron resonance with a magnetic field of 875 gauss at (28°), and high-density plasma is generated in the plasma generation space (3).
Generated in 1). From this high-density plasma region, active bromine ions with high energy are released into the substrate holder (10"-1
).

Object (to-1) on (10'-2) or (10-2
), the portions of the surface without a mask such as a photomask were removed by etching at an etching speed of 0.1 = 1 um/min (room temperature), and the YBr3. BaBrz+
It is vaporized and removed as a compound such as CuBr. In this way, it was possible to selectively leave only certain parts of the mask and remove other parts by etching.

The substrate may be anisotropically etched at the (10-1) position, or anisotropically etched using a divergent magnetic field at the (10-2) position. It should be determined by the usage.

Further, in this example, the oxide superconducting material is YBa2Cu30.
.

~8 was used, but YSr, CuzOa ~s, YBas
rcu:+0b-a+B12(SrCa)3CuzOa
It was possible to carry out the same procedure even with materials of ~+o.

"Example 2" FIG. 2 shows an example of the manufacturing process of a superconducting semiconductor device of the present invention.

In FIG. 2(A), a silicon oxide insulating film (2-1) is formed on a silicon semiconductor substrate (1).

There is an IGFE in the semiconductor substrate (1) in Fig. 2 (A).
T (insulated gate type semiconductor device), active type elements such as bipolar transistors, or passive type elements such as resistors and capacitors are provided in advance. These active or passive elements are provided, and impurity regions for connection with contacts of these elements are provided on the semiconductor. An opening (8) is formed in a part of the insulating film over this impurity region. In the embodiment of the present invention, a silicon oxide film is deposited on the semiconductor as an insulating film.
It was formed to have a thickness of 3 μm. Electrode contacts are then etched onto this silicon oxide film at predetermined positions using a photo-etching method.
A hole (opening) was created. Furthermore, zirconium oxide, which is a blocking insulating film (2-2) for acid-base reactions, is applied to the upper surfaces of these by sputtering to a thickness of 0.1 to 2μ, for example 0.4μ.
It was formed to a thickness of μm. These multilayered insulating films (2) are provided with electrode contact portions (
8).

Furthermore, in FIG. 2(A), a blocking conductive film (9) is provided in the opening (8) to prevent an acid-base reaction between the oxide superconducting ceramic and the semiconductor.

In FIG. 2 (8), a thin film of material (3) that should exhibit superconductivity is formed on the upper surfaces of these materials. This thin film was formed by sputtering. Screen printing, vacuum evaporation, or vapor phase (CVD) methods may be used, or a magnetic vapor phase method using the same apparatus as shown in FIG. 1 may be used.

The formed oxide superconducting material is a compound consisting of oxides of elements Ua and ma in the periodic table and copper, and the chemical formula of the formed oxide superconducting material is generally (A+-xBx)yc
uzOw+x=0. l to Ly = 2 to 4, preferably 2.5 to 3.5. z = 1.0-4.0 preferably 1
．． 5-3.5. w = 4.0~10.0 preferably 6~
It is 8. A is a lanthanoid such as Y or yb, B
Ba, Sr, and Ca base lines are used as the base lines. For example x = 0
．． 67, y=3. z = 3, w = 6 ~ denoted by B (Y
Ba2) Cu306-B was used.

In sputtering, as an example, the substrate temperature is 450°C.
°C, argon atmosphere, frequency 50Hz, output 100W
I went there. In this case, the thickness of the ceramic material is 0.2
The thickness was ˜2 μm, for example 1 μm.

After this, annealing was performed at 700°C (10 hours) in oxygen. Then, zirconium oxide (2-2) became a blocking material and was able to prevent the reaction between this oxide superconducting ceramic (3) and the silicon oxide (2-1) previously prepared below it. Incidentally, Auger spectroscopy has revealed that in the absence of this zirconium oxide, silicon oxide and the superconducting ceramic thin film become integrated in about 20 minutes. After that, this thin film makes it easier to grow crystals (Tc onset 1-=93K (
We were able to create a superconducting thin film whose resistance began to drop at 93 and experimentally showed that the resistance was virtually zero at 83. Of course, it goes without saying that in the absence of this blocking thin film, there is no superconductivity at all.

Thereafter, this thin film was subjected to predetermined patterning using the photolithography technique shown in Example 1.

In this way, a photoresist coating was applied to form electrodes and leads (5) for mutual wiring including connections with the electrodes and input and output terminals of the element, and selective removal (etching) was performed.
Figure (C) was obtained.

For this selective etching, the anisotropic etching of the plasma ECR (electron spin resonance) method shown in Example 1 using bromine (Brz) gas was particularly effective.

It is effective to carry out this patterning after forming the above-mentioned superconducting thin film, and then to perform thermal annealing to selectively crystallize only the patterned interaction areas.

In this case, since the crystal grain size is small in the initial state, a finer interconnection pattern is possible.

In FIG. 2(D), multilayer wiring was then performed as necessary.

For this reason, the interlayer insulator (6) is made of PIG (polyimide resin).
After forming an opening, a second layer of leads (7) and (7') was produced. The second layer is made of oxide superconducting ceramic leads (7) and (7).
') was configured.

In this example, the oxide superconducting material (A +
-Jx) CuzO- was used, but YBaSrCu30.
The same method could be applied to materials such as ma and Biz(SrCa)+CuzO++"++.

"Effects" The present invention has made it possible for the first time to put into practical use a superconducting device including these semiconductor devices, which is formed not at room temperature but at cooling.

Until now, no gas phase etching method has been known for such oxide superconductors, and they are particularly sensitive to water, so countermeasures have been urgently needed. The method of the present invention uses bromine or bromine compound gas, which is easy to handle and does not cause chemical damage such as corrosion to the reaction vessel, without using F, CI, etc. that have been commonly used in semiconductor processes. It was discovered for the first time that oxide superconducting materials can be etched in vacuum or under reduced pressure. Thus 10μm-0,0
It has become possible to etch lines/spaces of 1 μm, particularly 1.0 μm.

In the present invention, in order to generate active bromine, it is effective to use a magnetic field plasma activation method, RIE (reactive ion etching), and a photoexcitation method using ultraviolet light such as 185 nm.

Furthermore, as the bromine or bromine compound used in the present invention, not only bromine (Brz) but also carbide bromine (CBra), l
lBr etc. may also be used. However, H generally reacts with oxygen, which constitutes oxide superconducting materials, and easily generates water.
Easy to deteriorate superconducting properties. This made it possible to perform fine patterning without deteriorating the superconducting material in which bromine gas remained.

Therefore, by developing the technical idea of the present invention,
By applying a metal mask such as gold or silver or an organic resin mask such as photoresist to the parts that will become leads and electrodes, and removing other unnecessary parts, it is possible to apply it to ultra-super LSIs such as 14M to IG bits. became.

In the present invention, the substrate on which the oxide superconducting material is formed is not a silicon semiconductor (it may also be a compound semiconductor such as GaAs).
A semiconductor thin film may be used by heteroepitaxially growing a compound semiconductor such as (1)-(3). This makes it possible to perform ultra-high-speed operation. However, it is necessary to lower the annealing temperature and take measures to prevent the semiconductor substrate from deteriorating during the annealing.

In the present invention, the superconducting material is a copper oxide superconducting material.

However, it is also effective to use other superconducting materials that can be formed into fine patterns.

In the present invention, the substrate used is a semiconductor material provided with active elements and a non-oxide material provided on its upper surface. However, the substrate may be formed by forming a ceramic material having approximately the same coefficient of thermal expansion, such as YSZ (yttrium stabilized zircon) or 5rTt03, on the upper surface of an alumina plate or the like. This makes it easier to manufacture because the coefficient of thermal expansion can be matched. On the other hand, however, when such materials are used, the active elements must be formed separately, which has the disadvantage that it is difficult to achieve ultra-high integration.

[Brief explanation of the drawing]

FIG. 1 shows an outline of the etching apparatus used in the present invention. FIG. 2 shows an embodiment of a superconducting device using the present invention. 21'

Claims (1)

[Claims] 1. A mask is selectively formed on the oxide superconducting thin film formed on the substrate, and the oxide superconducting thin film in the area where the mask is removed is removed using active bromine. A method for manufacturing a superconductor device characterized by the following. 2. In claim 1, a plurality of semiconductor elements are provided within a semiconductor substrate, a coating having a blocking effect is provided on the semiconductor substrate, an oxide superconducting material is formed on the coating, and a lead is provided. A method for producing a superconductor device, comprising removing the oxide superconducting material other than the region using active bromine. 3. A method for producing a superconductor device according to claim 1, wherein the active bromine is made by bringing bromine or a bromine compound gas into a plasma state or an excited state using plasma or ultraviolet light. 4. A method for producing a superconductor device according to claim 1, wherein the oxide superconducting material is a copper oxide containing elements of groups IIa and IIIa in the periodic table of elements.