JPS5877264A - Manufacture of josephson element and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain the stabilized barrier layer for the titled Josephson element by a method wherein, in the case of an element which was formed by superposing a superconductive alloy containing at least either of Nb and Pb, NbFx of 20-60Angstrom in thickness is provided as a barrier layer on the surface of the underlayer electrode of Nb through the intermediary of an extremely thin barrier layer. CONSTITUTION:An Nb electrode is formed on a Si substrate, an window is provided on an interlayer insulating film, and after a sputtering has been performed on the electrode surface in a decompressed Ar, an NbFx of 20-60Angstrom in thickness is formed while plasma of high frequency output of 10-50W is being discharged in the Freon gas pressure of 1X10<-1>Torr, and the temperature is maintained at 80-120 deg.C during the performance of above procedure. Lastly, the upper electrode of Pb-Bi (30wt%) is vapor-deposited. Thus, an extremely thin NbFx film can be formed while stably maintaining the fluorine growing speed by utilizing the activity of an F-ion and exposing the metal in the plasma discharge where the etchability of metal is considerably reduced. According to this constitution, an Nb tunnel junction type Josephson element can be obtained with excellent reproducibility and stabilized characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of Application of the Invention The present invention relates to a very thin tunnel barrier layer of a Tononel junction type Josephson device and a method for manufacturing the same.

(2) Compared to Pb-based Josephson devices, the conventional Nb' yarn Josephson junction device has the features of a higher ultra-11iL4 critical temperature Tc, a higher recrystallization temperature, no hillock formation, and resistance to thermal cycles. However, it is expected to be a reliable device due to its reliability. However, the Nb film is more active than the Pb film, with 0. C.O.
, N*, etc., it has the disadvantage that a dense and thin oxide film barrier layer with few defects cannot be obtained. For this reason, it has been difficult and rare to fabricate a Nb-based Josephson element with uniform characteristics with good reproducibility.

A typical example of Nb-based Josephson elements is Nb-Nb.
, o, pb elements, and the manufacturing method thereof is as follows. In other words, N is applied to a cleaned Si-filled plate or a sapphire i-plate in a high wall of 10'''orr or less.
About 3,000 4-year-old VCs will cover b.

- An electronic kA evaporator 7IlR is used to prepare the Nb film on the pattern. Finally, the Nb film is etched using a photoetching technique to form a desired Nb charge +fi. Next, the Nb'iiLmMmk5~0.5×10-”Tor
rK depressurized Ar'I! , Enki, Meri is Ar+0. rQ1~3X treated with sputter cleaning in atmosphere
02 atmosphere tfflk with reduced pressure to 10-"l'orr
The yterf plasma spreads, and 20 to 30 people attack and form a monumental tunnel. P for breaking
Bt is layered to form the upper @electric ring, and the tunnel-based type Nyosefunn system is placed in the base. ,
- The thickness of the tunnel is 2t8m thick, with 20 to 30 people in proportion to the RF voltage and 08 partial pressure%, or the Europeanization time. I fell in love with controlling it well and had trouble. For this reason, in the rice technology, it is necessary to use a feminine buttock.
I didn't have to dress it up.

(3) Purpose of the Invention The present invention was devised to solve the above-mentioned problems, and is intended to provide an NbFx tunnel barrier layer with stable characteristics and a method for manufacturing the same.

(4) General declaration of the invention, i.e., Freonga'-t kept under reduced pressure, (CF'
4 When plasma is discharged inside the plasma, the first-order V gas dissociates, producing pure F9 radicals.

CF4+e HCF, +F* +2eThe active IJL of this F skewer is solidified by the energy of plasma emission and 7 rheo/gas pressure. In general, freon plasma etching VC
It is well known that in the processing of materials such as resists, they are processed using simple chain acids with an activity level of hF.

The purpose of the uninvented Ml is to use Fo's confusion directly. The second purpose was to expose canned cormorants to plasma radiation that significantly degraded the etching properties of F*.
Etching 4 tables and fluoridation of the WM4 six mouths? ! A thin tunnel barrier of 20 to 60 people while eliminating the Sho NbF in an equilibrium state! The general conditions for producing a 20 to 60-layer thick Nb mass using the 6C method are as follows:
Freon gas pressure %IX 10-' ~ 5 X 10-''
TOrr% +%Jmiitl force 10~50W (0
,03~0.15W/crn"), stage ax8
The range is 0C to 120C. That is, the Freon gas pressure is 1
x 10-”bo N b F x over 10-”l’orr
The fabric speed increases, resulting in a film with many pinholes.

On the other hand, at pressures below 5X10-"l'orr, NbFx
The 5E genus of glands is not entangled. In addition, the pigeon wave output is lOW
(0,03W/cW1") or less, the generation of NbFxk cannot be introduced. If it becomes more than 50W (0,15W/ltn), the F umbrella's insulating condition becomes even worse, and the etching of Nb is repeated and the desired percentage is reached. The age of NbFx Rin is not recognized.Furthermore, the stage Atsura is also in order to attend the intense N01I''ll]L arrow is used to create the SFM record, and the taste is yoke to Akane, and the plasma is released. By controlling 80 to 120 CK, the activity level of F Monkey can be kept to a certain level, and agriculture can be generated in Female Ken.

(5), *Examples The following details will be continued with reference to non-inventions. 10-"l'
Mold to a thickness of about 3,000 Nbt in a tube of less than orr. Photoresist and water bathing
t to form the lower electrode by etching the desired pattern. In Riki', Hatoma Haenen 5iov is formed on the previous iNb11L and other songs. At this time, a lift-off process is used to provide a mouth portion so that a portion of the front mouth Nbxm is exposed. The hliiiKil out L7'h N
b 1tL Kossa 1111'! k 5 x 10°3'
I'orrKs Sputter cleaning in a pressurized argon atmosphere, followed by Vh tear x 10-” Torr
The exposed Nb′#L was discharged for 10 minutes in the Freon gas plasma generated at a high frequency output of 20 W.
NbFxt with a thickness of about 4 OA is taken as raw material.

Next, pb-Bi (30wt%) was applied to a photographic area of about 4,000 people to form an upper layer. The Nb-NbFx-PbHj ) tunnel bonded Josephson thread prepared by the method described above was immersed in He, and both '! I
When I used a wL accent on my L routine, Josephson Rin'If
- Flow Jc was served with 1 μ of 2000A10n”.Furthermore, the friend sea bream in the same web (60φ) of Jc was ±5%, and the dark vibration to sea urchin was ±10%, and the immersion was extremely good. Although not specifically mentioned in this article, after forming the tunnel #IIt wall J Zeng using the method described above, the Nb
, or Nb, si.

There is also a platform made of Nb, 8n, Nb, Ge, etc.

Jc and Jc's father, the sea bream, met with a Pb thread Sakakidai and a single roku.

(6) Summary As explained above, according to the main book@IJ, N'bhe tunnel-jointed Josephson confectionery can now be made easily. The i1p% property of the reeds is also extremely stable, and even when each person repeats the adult He temperature (4.2K) and the dark heat cycle M' 1000 times, the JcO fine #f plexus formation is ±2 It was observed that the tonnel barrier layer of 5NbFx could be torn down within 5%.

[Brief explanation of the drawing]

ml- shows the # view of the tunnel choreography type Josephson tunnel junction device. 1...Substrate, 2...Haki layer, 3...Lower'#L customization, 4...Ton 0 Inventor Junji Shigeta Hitachi, Ltd. Central Research 04''!$1 @ ;: : 47□, Engineering, 2.1゛ 21
,−

Claims (1)

[Scope of Claims] 1. Nb is used as a lower layer, a tunnel barrier layer is formed on the surface of the wire, and a superconducting alloy containing Nb, PB, or at least one of them is superconducting. s'lllL
Josephson element Z is characterized by using NbFx with a thickness of 20 to 60 mm for the tunnel barrier l- in a Josephson element with a tunnel junction as a pole. In addition to forming a tunnel barrier layer around the outer layer, the top 11L is made of super conductive metal containing Nb, Pb, or at least one of the metals.
In the production of other tunnel-connected Josephson devices, the 7 rheo/gas pressure is 1xlO"'-3X10-"T
orr, power output 10~50W (0,03~0.
After forming NbFx to a thickness of 20 to 160 nm on the Nb lower electrode in a plasma discharge of 15 W/crn, a super alloy containing Nb.pb or at least one of gold 17I4 was formed. 1. A method for manufacturing a Josephson type device characterized by having an upper ′-pole.