JP3152768B2 - Multilayer wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board, and more particularly to a multilayer wiring board used for a circuit board or a package on which a superconducting element such as a Josephson element is mounted.

[0002]

2. Description of the Related Art Conventionally, in a multilayer wiring board used for a hybrid integrated circuit device, a package for accommodating a semiconductor element, or the like, its circuit wiring is formed by a thick film forming technique such as the Mo-Mn method.

[0003] This Mo-Mn method is generally used for tungsten,
Organic solvents for high melting point metal powders such as molybdenum and manganese,
A solvent is added and mixed, and a paste-shaped metal paste is printed and applied in a predetermined pattern on the outer surface of the green ceramic body by a screen printing method. This is a method of sintering and integrating a metal powder and a green ceramic body.

The ceramic body on which the circuit wiring is formed is usually an oxide ceramic such as an aluminum oxide sintered body or a mullite sintered body, or an aluminum nitride having an oxide film deposited on the surface. Non-oxide ceramics such as a porous sintered body and a silicon carbide sintered body are used.

However, when the circuit wiring is formed by using the Mo-Mn method, the circuit wiring is formed by screen-printing a metal paste. There was a disadvantage that it could not be done.

The circuit wiring is made of tungsten, molybdenum, or the like. The tungsten, molybdenum, or the like has a high electric resistance value, and cannot transmit electric signals at high speed. When the superconducting element is connected, there is a disadvantage that the original high-speed driving function of the superconducting element cannot be sufficiently exhibited.

Therefore, in order to solve the above-mentioned drawbacks, the circuit wiring is formed by using a thin film forming technique capable of miniaturization instead of the conventional thick film forming technique, and the circuit wiring is made of niobium which is a superconducting material. Have been used.

A multilayer wiring board using niobium for the circuit wiring is generally formed on an insulating substrate made of aluminum oxide sintered body or the like by employing a sputtering method, an ion plating method, or a photolithography technique. Are alternately laminated with an insulating film made of an organic polymer material such as a polyimide resin formed by a spin coating method, and the upper and lower circuit wires are electrically connected through through holes provided in the insulating film. It has the structure connected to.

[0009]

However, in this multilayer wiring board, the diameter of a through hole formed in an insulating film for electrically connecting circuit wirings located above and below is about 30 mm.
μm, the inner wall length of the cross section is as short as about 95 μm, and electric signals to and from superconducting elements such as Josephson elements are transmitted selectively through the surface of circuit wiring. The amount of allowable current becomes small, and as a result, a superconducting element such as a Josephson element is connected to a circuit wiring electrically connected through a through hole, and an electric signal is sent into and out of the superconducting element through the circuit wiring. In such a case, the transmission of the electric signal is greatly restricted in the through hole, and the electric signal cannot be transmitted to the upper and lower circuit wirings in a satisfactory manner.

[0010]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and an object of the present invention is to allow a superconducting element to sufficiently exhibit its original high-speed driving function without being limited by electric signals transmitted through circuit wiring. It is an object of the present invention to provide a multi-layer wiring board that can be used.

[0011]

According to the present invention, an insulating film made of a polymer material and a circuit wiring film are alternately laminated on an insulating substrate, and a through-hole in which circuit wiring films located above and below are provided in the insulating film. A multilayer wiring board electrically connected via a through hole, wherein the shape of the inner wall surface in the cross section of the through hole is a waveform, and the inner wall length of the cross section is 160 μm or more.

[0012]

According to the multilayer wiring board of the present invention, the shape of the inner wall surface in the cross section of the through hole provided in the insulating film is made into a waveform, the inner wall length of the cross section is made 160 μm or more, and the allowable current in the through hole is increased. Therefore, even if a superconducting element such as a Josephson element is connected to a circuit wiring electrically connected through a through hole, and an electric signal is put in and out of the superconducting element through the circuit wiring, the electric signal remains in the through hole. The transmission is not greatly restricted, and the electric signal can be transmitted favorably to the upper and lower circuit wirings.

[0013]

Next, the present invention will be described in detail with reference to examples. 1 and 2 show one embodiment of the multilayer wiring board of the present invention, wherein 1 is an insulating base made of an electrically insulating material, 2 is an insulating film, and 3 is a circuit wiring film.

The insulating substrate 1 is made of an oxide ceramic such as an aluminum oxide sintered body or a mullite sintered body, or an aluminum nitride sintered body having an oxide film on its surface.
It is made of a non-oxide ceramic such as a silicon carbide sintered body. For example, when it is made of an aluminum oxide sintered body, alumina (Al ₂ O ₃ ), silica (SiO ₂ ), calcia
(CaO), a suitable organic solvent to raw material powder such as magnesia (MgO), a solvent is added and mixed to form a slurry, and the ceramic green sheet is formed by employing a conventionally known doctor blade method or calendar roll method. Ceramic green sheet), and thereafter, the ceramic green sheet is subjected to an appropriate punching process, formed into a predetermined shape and fired at a high temperature (about 1600 ° C.), or an organic material suitable for a raw material powder such as alumina. The raw material powder is formed into a predetermined shape by a press forming machine while adding and mixing a solvent and a solvent, and then the formed body is sintered at a temperature of about 1600 ° C.

The insulating substrate 1 made of the above-mentioned oxide ceramic or non-oxide ceramic having an oxide film on the surface serves to support a multilayer wiring 4 composed of an insulating film 2 and a circuit wiring 3 which will be described later. On the surface, insulating films 2 and circuit wiring films 3 are alternately deposited and laminated.

Each insulating film 2 deposited on the surface of the insulating base 1 is made of a polymer material such as a polyimide resin.
A polymer solution composed of 50 mol% of 4,4 'diaminodiphenyl ether, 50 mol% of diaminodiphenylsulfone, and 3,3', 4,4'-biphenyltetracarboxylic dianhydride is applied to the upper surface of the insulating substrate 1 by spin coating. And then, 40
It is formed by applying heat at 0 ° C. to thermally crosslink the polymer solution.

The insulating films 2 serve to maintain electrical insulation between the circuit wiring films 3, and if the thickness is less than 2.0 μm, the reliability of the electrical insulation between the circuit wiring films 3 is reduced. When the thickness exceeds 30.0 μm, a large stress is generated inside the insulating film 2 when the insulating film 2 is formed, and the bonding strength between the insulating film 2 and the insulating substrate 1 and the circuit wiring film 3 is increased. May be reduced. Therefore, it is preferable that the insulating film 2 has a thickness of 2.0 to 30.0 μm.

Further, as shown in FIG.
A through-hole 5 having a substantially star-shaped cross section is formed on the inner wall surface, and the through-hole 5 serves to electrically connect the circuit wiring film 3 formed with the insulating film 2 interposed therebetween. Make

The through hole 5 provided in the insulating film 2 has corrugated irregularities on the inner wall surface, and has a cross-sectional inner wall length of 160.
μm or more, the allowable current amount in the through hole 5 becomes extremely large. As a result, a superconducting element such as a Josephson element is connected to the circuit wiring film 3 connected through the through hole 5, and the circuit wiring When an electric signal is transferred into and out of the superconducting element through the film 3, transmission of the electric signal through the through hole 5 is not greatly restricted, and the electric signal can be transmitted well to the circuit wiring films 3 located above and below. Becomes possible.

The through-hole 5 provided in the insulating film 2
When the inner wall length of the cross section is less than 160 μm, the permissible current amount in the through hole 5 becomes small, and the transmission of electric signals is restricted. Therefore, the through-hole 5 provided in the insulating film 2 is specified to have a cross-sectional inner wall length of 160 μm or more.

A through hole 5 provided in the insulating film 2
Is not limited to those having a substantially star-shaped cross section as long as corrugated irregularities are formed on its inner wall surface and the inner wall length of the cross section is 160 μm or more.

Further, the through holes 5 provided in each of the insulating films 2 are formed at predetermined positions and in predetermined shapes by employing the conventionally known photolithography technique.

On the other hand, a circuit wiring film 3 is formed in a predetermined pattern on the upper surface of each of the insulating films 2 formed on the surface of the insulating base 1, and the insulating film 2 is interposed therebetween. The upper and lower predetermined circuit wiring films 3 are electrically connected through through holes 5 provided in the insulating film 2.

A circuit wiring film 3 disposed between the insulating films 2
Is made of a superconducting material such as niobium, and the circuit wiring film 3 functions as a transmission path for transmitting an electric signal.

The circuit wiring film 3 is formed by coating niobium on the insulating film 2 by a sputtering method or an ion plating method and processing the niobium into a predetermined pattern by a photolithography technique. The circuit wiring film 3 formed by the sputtering method or the photolithography technique has a very small line width and thickness, and as a result,
The circuit wiring film 3 can be miniaturized, and the circuit wiring film 3 can be made denser.

If the thickness of the circuit wiring film 3 made of niobium is less than 1.0 μm, a very thin portion is formed in the circuit wiring film 3 due to the surface roughness of the insulating film 2, Normally, it becomes difficult to transmit an electrical signal to the wiring film 3. If the thickness exceeds 5.0 μm, there is a risk that the stress generated when the circuit wiring film 3 is formed may cause separation between the circuit wiring film 3 and the insulating film 2. There is. Therefore, it is preferable that the thickness of the circuit wiring film 3 made of niobium be in the range of 1.0 to 5.0 μm.

The niobium forming the circuit wiring film 3 is very easily oxidized, and once oxidized, the superconductivity is lost. Therefore, the surface of the niobium forming the circuit wiring film 3 is made of niobium nitride or the like. It is preferable that an antioxidant film is applied.

Thus, according to the multilayer wiring board of the present invention,
A superconducting element such as a Josephson element is electrically connected to the circuit wiring film 3 and an electric signal is sent into and out of the superconducting element through the circuit wiring film 3 to be used in a hybrid integrated circuit device or a semiconductor device storage package. It functions as a wiring board.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

[0030]

According to the multilayer wiring board of the present invention, the shape of the inner wall surface in the cross section of the through hole provided in the insulating film is made into a waveform, the inner wall length of the cross section is made 160 μm or more, and the allowable current amount in the through hole is increased. Therefore, even if a superconducting element such as a Josephson element is connected to the circuit wiring that is electrically connected through the through hole, and an electric signal is put in and out of the superconducting element through the circuit wiring, the electric signal is transmitted through the through hole. In this case, the transmission is not greatly limited, and the electric signal can be transmitted favorably to the upper and lower circuit wirings.

Further, since the circuit wiring film is formed of niobium, which is a superconducting material, the transmission speed of electric signals transmitted through the circuit wiring film can be made extremely high. When a superconducting element such as a Josephson element is connected, a signal is transmitted at high speed to the circuit wiring, so that the function of the superconducting element inherently capable of high-speed driving can be sufficiently exhibited.

Further, the circuit wiring film is formed by a thin film forming technique such as a sputtering method or an ion plating method, so that the circuit wiring film can be miniaturized and the circuit wiring film can have a high density.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a multilayer wiring board of the present invention.

FIG. 2 is a plan view for explaining through holes provided in an insulating film of the multilayer wiring board shown in FIG. 1;

[Explanation of symbols]

 1 ... Insulating substrate 2 ... Insulating film 3 ... Circuit wiring film 5 ... Through hole

Claims (1)

(57) [Claims] An insulating film made of a polymer material and a circuit wiring film are alternately laminated on an insulating substrate, and the circuit wiring films located above and below are electrically connected to each other through through holes provided in the insulating film. A multilayer wiring board comprising: a cross-sectional shape of an inner wall surface in a cross section of the through-hole; and a cross- sectional inner wall length of 160 μm or more.