JPS6043883A - Tunnel type josephson element integrated circuit - Google Patents

Abstract

PURPOSE:To prevent the deterioration of the superconducting characteristics of a Nb or Nb compound electrode, and to form an inter-layer insulating layer and a protective layer having high reliability by using a metallic fluoride as an inter- layer insulating layer substance and a protective layer substance for a circuit chip. CONSTITUTION:A metallic fluoride, such as LiF, NaF, KF, BeF2, MgF2, CaF2, SrF2, BaF2, YF3, ZrF4, HfF4, AlF3, TlF3, PbF2, SbF3, BiF3, LaF3, CeF3, NdF3, etc. is used as inter-layer insulating layers 8 and a protective layer 9. When the metallic fluoride is used as the inter-layer insulating layers 8, the superconducting characteristics of a Nb or Nb compound electrode are improved, the characteristics of a Josephson junction element are not deteriorated, and the margin of circuit operation can be ensured. When the metallic fluoride is used as the protective layer 9 for a circuit chip, a substance, which is not corroded by tartaric acid, dimethylamine hydrochloride, etc. as components in used flux, can be selected when a solder bump is formed because of flip chip bonding, and a function as the protective layer for a circuit is not lost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a tunnel type Josephson element integrated circuit, specifically, a base electrode VrCNb or a Nb compound, a counter electrode with Nb
The present invention relates to a substance constituting a stable and high-quality interlayer insulating layer and a protective layer of a circuit chip in a circuit configuration using a tunnel type Josephson junction using Pb, Nb compound, or Pb alloy.

(Prior Art) A circuit using a Josephson junction basically consists of the following. In Figure 1, 1 is the substrate (Si or sapphire), 2 is the Fi ground plane (Nb or Nb compound), 3 is the base electrode (Pb alloy, Nb or Nb compound), and 4 is the tunnel barrier (oxidation of the base electrode). 5 (tll counterelectrode Pb alloy or Nl) or Nb compound), 6 is the control line (1) b alloy or Nb), 7 is the resistance element ('AuIn
2 and AuA4). The wires must be electrically insulated from each other except in limited areas that are necessary for the circuit, and when attempting to integrate the circuit by performing multilayer wiring, it is necessary to It is essential to place eight interlayer insulating layers. 1.Joseph software circuits are normally operated at extremely low temperatures (4, JK), but when raised to room temperature, moisture in the atmosphere freezes on the circuit chip, and when using PB gold alloy electrodes, control lines, or resistors Vc, moisture It is necessary to place a protective layer 9 on the top layer to prevent its deterioration due to. This protective layer is also indispensable for insulation and protection of the circuit when the tip and chip are bonded to the solder bump (norib chip bonding). Conventionally, 5102 or SiO has been used for the interlayer insulating layer and the protective layer, but there are the following problems when using 5102 or SiO for the interlayer insulating layer and the protective layer. When used in 5i02 for the interlayer insulating layer and protective layer,
The 5102 film is usually formed using a 2-pole RF sputter, but when the 8102 film is formed on a PB gold alloy using a 24-pole RF sputter, the characteristics of the PB gold alloy may be affected due to a rise in the temperature of the substrate or the incidence of antistatic particles such as Ar on the substrate. deteriorates. Also Nb
Alternatively, if a 5i02 film is formed using a two-pole RF sputter on a Nb compound film, the Nb film or Nb compound film will not deteriorate due to an increase in the substrate temperature, but the Nb film or Nb compound film will be The superconducting properties (superconducting critical temperature, riIi flux penetration) of the Nb compound deteriorate.

To prevent these problems, K can be used to form a 5i02 film using RF magnetron sputtering. However, since the patterning of the sputtered film of 5io2 depends on etching, some of the Nb or Nb compound or PB gold alloy may be roughened or deteriorated by etching rfA (F radicals and F ions). As a result, the circuit cannot be configured, or the circuit operation may become abnormal. To prevent these problems, add 5102 or sio to the interlayer insulating layer or protective layer.
A lift-off stencil can be created and patterned using the evaporated film. However, the following problems still exist when using 5i02 or sio steamed films. 5i02 or S
When a Nb or Nb compound electrode is formed on i011a, the initially deposited Nb or Nb of the Nb compound reacts with oxygen, which is an element constituting sioX, and exhibits weak metallic propertiesT N
bOx (NbO, Nb0tfi t)h 9 Nb
+7) Since the superconducting properties (critical temperature, magnetic flux penetration) of the initial deposited layer deteriorate, the base electrode Nb film or Nb compound film must be sufficiently thick (>300 m
05. ), which is disadvantageous for V multilayer wiring. If Nb or a Nb compound is selected as the counter electrode, the characteristics of the Josephson junction element will be poor due to the deterioration of the superconductivity of the initial deposited layer, making it impossible to maintain a margin for circuit operation. Furthermore, 5i02 or SiO film is applied to protect the circuit chip.
When used as a protective layer, when bonding solder bang chips and naps together (Noritsubu chip bonding), the ERI 5i02 or SIO film is attacked by tartaric acid or dimenalamine hydrochloride, which are components of the solder flux, and functions as a protective layer. may be lost.

As described above, 5i02 or SiO has the drawback that it interferes with the construction and operation of the circuit when used as an interlayer insulating layer material and a protective layer material in a Josephson junction circuit.

(Object of the invention) Base electrode is Nb or Nb compound, counter electrode 1l-1iP
B alloy or composed of Nb or Nb compounds
In a circuit using a Nell-type Josephson junction element, even if 5in2 or SiO is used as the interlayer insulating layer material between the electrodes or other metals, and as the protective layer material for the circuit tip, the circuit will not be completed. It may cause problems in configuration and operation.

The present invention has been proposed to improve these drawbacks.

(Structure of the Invention) The present invention provides a tunnel type Josenson junction element integrated circuit V in which the base electrode is made of Nb or a Nb compound superconductor, and the counter electrode is made of Nb or a 1dNb compound superconductor or a pb gold alloy. The gist of the invention is a tunnel-type Josephson multilayer integrated circuit characterized in that interlayer insulating layers between metal films including electrodes, resistive elements, and control lines, and circuit top protection are made of metal fluoride. .

Therefore, in the present invention, the following solidified LiF is used.

NaF, KF, BeF2. MgF2r CaF
2+ SrF2. BaF2+YF3, ZrF4
, HfR, AI-F3, TAF3, PbRr
5bFx +BiF3. LaF, , CeF,q
, NdF, If: Use a material above 1 μm as the interlayer insulating layer material and the circuit step D protective layer material. From Vc, it is possible to construct a circuit by patterning with a lift-off stencil. When used in an interlayer insulating layer, even if a reaction occurs between the initial deposited layer of Nb or a Nb compound and fluoride, the fluoride of Nb, NbF, is a sublimable gas at room temperature, so it will not exceed the Nb or Nb compound electrode. Substances exhibiting weak metallic properties that deteriorate conductive properties are not generated, and some of these fluorides have excellent acid resistance, so tartaric acid, tumenalamine hydrochloride, etc. are not eroded by Vζ, the main component of solder flux. The material can be selected and a highly reliable protective layer can be formed, and its purpose is to form a high quality protective layer with two interlayer insulating layers.

The base electrode is made of Nb or a Nb compound, and the counter electrode is made of a PB alloy or a Nb or Nb compound.
Conventionally, 5i02 or SiO has been used as the material for the interlayer insulating layer between electrodes or metal films and the material for the protective layer of the circuit chip.

When using 8102 as an interlayer insulating layer or a protective layer, sputtering VCJl: In the case of two-pole RF sputtering, vC is used for X radiation of power-saving particles to the substrate, due to deterioration of the metal thin film, and Even in the case of magnetron sputtering, which can prevent the incidence of power-saving particles, the patterning method has to be etched, so a part of the electrode or metal film is exposed to the 5JO2 etching process and is etched or deteriorated. There is a problem that the circuit cannot be configured or the circuit operation becomes abnormal.

In order to solve all of these problems, even if a 5i02 or SiO vaporized N film is used as the interlayer R layer or the protective layer and patterning is performed using a lift-off stencil, the following problem remains. One is that when an Nb electrode is formed on a 5i02 or Sio film, Nb, which is an element constituting the initially deposited Nb or Nb compound, is
b is 5i02 or sio w Nb0z (NbO, N
lower oxides other than Nb* 0* such as b0t) and Nb
or the superconducting properties (critical temperature,
The base electrode Nb film or N
9. The compound film b must be sufficiently thick (>3,000 thick) to ensure good superconducting properties on the surface.9. Tomorrow, it will be disadvantageous for multilayer wiring. If Nb or a Nb compound is selected as the counter electrode, the superconducting properties of the initially deposited layer deteriorate, resulting in poor Josephson junction device characteristics, making it impossible to maintain a margin for circuit operation. 2. When VCS10 or SiO film is used as a protective layer of a circuit chip, when bonding the chip to the backing nap of the solder bang (flip chip bonding), use VC such as tartaric acid or dimenalamine hydrochloride, which is the main component of the flux for soldering. , C5ift or SiO film may be attacked and the function as a protective layer may be lost.

As described above, by using a KT base electrode of Nb or a Nb compound and a Josephson junction element using a pb alloy or 1-tNb or a Nb compound for the counter electrode, the lζ circuit is configured.
Interlayer insulation layer material and protective layer material for circuit nap K510
2 or SjO may cause problems in circuit configuration and operation.
Eating was a problem.

Therefore, the entire circuit configuration including buttering is facilitated, the deterioration of the gold dust film is prevented and a margin for circuit operation is ensured, and the interlayer insulating layer material and retaining layer material are not attacked by the solder flux V. Use fluoride to coat the lift-off stencil. The following fluorides LjF, NaF, KF, BeF
t + MgFt, CaF2rSrFt + Ba
Fz l YFs, zrF'4. f(fF, ,
AtF', , TbF3゜PbF2t F3bFs
r BIFJ r LaF3, CeF3, N
The interlayer insulating layer 2 is made of one or more substances selected from dFj.
The following advantages arise when used in a textured protective layer. One is that even if a Nb or Nl) compound electrode is formed on the layer used for the interlayer insulating layer, even if a reaction occurs between the initial deposited layer of Nb or Nb compound and the fluoride, the Nb fluoride Since NbF is a sublimable gas at room temperature, a substance exhibiting weak metallic properties that deteriorates the superconductivity and characteristics of Nb or Nb compound electrodes is not produced at t'1. The superconductivity of the Nb or Nb compound electrode can be improved, the characteristics of the Josephson junction element will not deteriorate, and the circuit operation margin can be secured.
This is advantageous for multilayer wiring because there is no problem even if the thickness of the Nb or Nb compound film is 220005L or less. The advantage of the second band is that when used as a protective layer for circuit chips, it is a material that is not attacked by salt, dimethylamine salt, etc., which are components of the flux used when forming solder bumps for flip-step bonding. The key is to not lose the function of the circuit as a robust layer. Fluoride like this? f: Used in interlayer insulating layer JJM, JNAE and protective layer F2 and Josephson junction element circuit structure are advantageous for operation.

(Example 1) 2 inch J 81 substrate with thermal oxide film (5i02 film thickness ~
100OA) and Nb film '599.9 for the ground plane.
Using a 9-inch Nb target (150 rymφ, thickness 5"1) in Ar gas of 2 x 10" torr by DC magnetron sputtering at a substrate temperature of 300 °C.
It was formed to a thickness of 1000^ at a deposition rate of 0^/min. This thin film was coated with a resist, exposed to light, developed, and etched to form a pattern for the ground plane. Next, we fabricated a window-type tunnel-type Josephson junction device using these substrates. 1 - that is, 1 thickness 2500 ^ on the ground plane
After forming an interlayer insulating layer of TtFa by a lift-off method using a resist stencil and vapor deposition, an N for base electrode is formed.
Form b film by DC magnetron sputtering method 2
00OA, substrate temperature 250°C) resist coating, exposure, development, etching, and l: repatterning. When the dielectric breakdown voltage of the TtF3 film was examined by applying a current voltage between the ground plane and the base electrode, it was found to be more than IOOV, confirming good insulation. Next, 3000 to T Earth Dragon Gokujo.
After forming an interlayer insulating layer made of ZrF4 by vapor deposition and lift-off method, cleaning the surface of the base electrode that will become the bonding part and forming a tunnel barrier, a Nb film for the counter electrode is formed by DC magnetron sputtering method. a5oo
i, substrate temperature at room temperature) resist coating, exposure, 1i image, 'batterning rek from Etsunan yvc. or Pb
-'29 wt, % Bi counter electrode lift-off method J
, was formed. The properties of these Josephson junctions are IJ
” RNN = 1.8mV.

1.9mV IJ @R8G = 32 mV,
50. mV (IJ is the maximum Josephson current, RN
It was confirmed that there was no deterioration of the counter electrode due to the material selected as the interlayer insulating layer material.

(Example 2) In actual Ma example 1, the ground plane (Nb), insulating layer (TtFa), base electrode ([b), insulating layer (ZrF+) + counter electrode (N
After forming an insulating layer composed of ZrF and a control line of pb-In=Au using the five substrates on which b) was formed, respectively ZrF4r)lfF4r TtFa + PbR+
A 6000 A security layer drawn with LaF3 was formed by a lift-off method. These protective layers do not peel off even when subjected to thermal cycle between liquid helium temperature and room temperature, which invades water resistance, and are coated with tartaric acid or dimenalamine, which is a component of solder flux for flip-step bonding. It was not affected by hydrochloride.

(Example 3) Example 1-11 Using five substrates on which Nb ground planes were formed, AtF3 (45 mol, '$) was placed on the ground planes.
-250 composed of PbF2 (55mol.%)
0 person's insulation layer f +) foot-off method ll? : More formed. Next, a layer for the base electrode composed of Nb was formed by the kDc magnetron sputtering method at a deposition rate of 400^/min (2000 people, substrate temperature 250°C), resist coated, and exposed.

I used Eliva tanning for development and etching. The ground plane and base electrode are well insulated, and the breakdown voltage is 17
It was 0V. Next, using these substrates, fL
ZrF* (60) GdFs (6) -BaF,
(34 mol, %) l ZrF4(62) -L
aF′5(4) −BaF″′;(,30) −A7F
3 (4mol.%), AtFa(40)-BaF
2(25) -CaF2(25)YF3(10mol
．． %).

HfF+(57) YFs(5)-BaF2(30)-
AtF3 (,8rno1.%).

ZrF'4(b5)-BaFz (35 mol,
%) resist stencil r
c, J: Is it possible to form a joint using the lift-off method? After cleaning and forming a tunnel barrier, a thin film for the counter electrode composed of Nb"c was formed by magnetron sputtering. 3500 A, substrate temperature at room temperature) resist coating, *light, development, etching VC, C9 patterning L-7j Table 1 shows the dielectric breakdown voltage between the two Josephson junctions and the same electrode and the ground plane through these five types of insulators. It was confirmed that good insulation properties were obtained when this material was selected as the material for the interlayer insulating layer, and there was no deterioration of the counter electrode.

Similarly, the lift-off method was applied to Pb-29wt% [
A 3i counter electrode was bonded. Its properties are shown in Table 2.

(Example 4) In Example 3, the Nb counter electrode ζ was made of ZrF4 (60
) GdFa (6) BaF2 (34mo1.%
), ZrF4(62)-LaFs(4)-BaFz
(30) 7AtFa (4mol.%).

AtFs (40) -BaR(25) -CaF2(
25)-YFs (10mol.%).

HfF4 (57)-YFa(5)-BaFt(30)
-AtFa (8mol.%).

ZrF4 (65) -BaF', (35 mol,
%), htFs(45)-PbFt(55mo
1. %) was formed to a thickness of j) 6000λ by a lift-off method using a resist stencil. These protective layers are highly water resistant and contain 1M liquid helium.
It did not peel off even when subjected to thermal cycles between the surface and room temperature, and was not attacked by tartaric acid or dimethylamine hydrochloride, which are the primary components of solder flux.

(Example 5) Yojijmff'! Four substrates with Nb ground plane patterns formed using It were used as base electrodes: NbN, N
b.A.A.

It is composed of Nb5sn and Nb5Ge, and the counter electrodes are each 1NbN + Nb5AL T Nb5Snr.
N1) A tunnel-type Josephson contact composed of 3Ge was fabricated. 250OA PbF2k was used as the insulating layer between the Nb ground plane and the underlying electrode, and F-patterned into a foot-off stencil.Nb All dielectric breakdown voltages between the ground plane and the underlying electrode were 100 V or higher.

In addition, the insulating layer between the base electrode and the counter electrode has a
ZrF4 (65) -BaR (35 mol, %
) was buttered using a lint-off stencil. ZrF between Nb ground plane and counter electrode, (65)
-BaFt (35) The breakdown voltage for all boundaries is 15
It was 0 V or more. The base electrode and counter electrode are made of NbN (
l-jNb target in Ar 1N atmosphere,
Also N'b, At.

Nb3Sn and Nb3Ge have 75 and 25 atoms.
c) Formed by DC magnetron sputtering using percentO public gold target 15, resist coated,
exposure.

I used patterning on the image and etching. Table 3 shows the characteristics of these Josephson junctions.

NbN by using fluoride as an insulating layer from 29.
It was confirmed that there was no deterioration of the Nb, i, Nb, snr Nb3Ge electrode.

Table 3 (Effects of the Invention) As mentioned above, according to the present invention, the base electrode is Nb or Nb
The counter electrode is composed of Nb or Nb compound or p
b In a circuit using a tunnel type Josephson junction composed of a gold alloy, LiF, NaF, KF I BeF2
1 MgF2 + Cal”21 SrF21BaF2
．． YF3, ZrF4, HfF4 r AtF
s, TtF3, PbF2.

bbFs + B'l! 3 r LaFs + CeF
By using one or more substances selected from s + NdFs in the interlayer insulating layer, deterioration of the superconducting properties of the Nb or Nb compound electrode can be prevented, and by using it in the protective layer, it can prevent the solder flux from eroding. This has the advantage that it is possible to select materials that are not used as a material, and it is possible to form highly reliable interlayer insulating layers and protective layers.

[Brief explanation of the drawing]

FIG. 1 shows a conceptual cross-sectional view of a circuit using a Johnsonson junction element. l・・・・・・Si substrate 2・・・・・・・・・Nb ground plane 3・・・・・・Base electrode 4・・・・・・Tony Lebaria 5...
...Counter electrode 6...Control line 7...Resistance element 8...Interlayer insulating layer 9... ...Protective layer patent applicant Nippon Telegraph and Telephone Public Corporation

Claims (2)

[Claims] (1) In a tunnel type Josephson junction cumulative integrated circuit in which the base electrode is made of Nb or a Nb compound superconductor and the counter electrode is made of Nb or a Nb compound superconductor or a Pb alloy, between the electrodes, between the electrodes and the resistive element, A tunnel-type Joffson element integrated circuit characterized in that an interlayer insulating layer including a control line between all films, and a circuit chip protection are made of metal fluoride. (2) Metal fluoride is LiF, NaF, KF,
BeF2, [IgF2゜CaRI 5rF21 B
aF2 + YF3 r ZrF4 + HfF4 +
AZF3 +TtF3+ Pbl”2 + 5bFi
r BIF3r LaF3+ CeF3+ NdFs
2. The tunnel type Josephson transducer integrated circuit according to claim 1, characterized in that the tunnel type Josephson transducer integrated circuit comprises one or more types of.