JPH06132576A - Manufacture of superconducting element - Google Patents

Abstract

PURPOSE:To inhibit a resistance film from being peeled during a process of forming an element and after the element is formed by a method wherein the resistance film is formed not on the surface of a layer insulating film but in the interlayer insulating film in such a way that it is fitted in the insulating film. CONSTITUTION:A layer insulator film 11 is formed on a silicon substrate 10 and a pattern formation resist layer 12 to decide a resistance film pattern is formed on the film 11 in a thickness of about 15000Angstrom . Then, the substrate 10 provided with the film 11 and the layer 12 is put in a reactive ion etching device and the film 11 is dug down to a depth of 400Angstrom . Then, the sample is moved to a deposition device and a Pd film 13 is formed in a thickness of 400Angstrom . Lastly, the layer 12 is lifted-off, whereby the resistance film 13 having a desired pattern is obtained in a state that it is buried in the film 11. Moreover, a second layer insulator film 14 is formed thereon in the same thickness as that of the film 11 and a contact hole and a superconducting film are formed.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a superconducting quantum interference device (SQUID) for an ultrasensitive magnetic measurement system, low power consumption,
In superconducting elements such as superconducting digital circuit elements used to construct ultra-high speed computers, it is required to eliminate hysteresis of superconducting characteristics and to suppress electrical vibration of resonant circuits. The present invention relates to an improved method of forming a resistance film.

[0002]

2. Description of the Related Art Conventionally, a resistance film used for canceling the hysteresis of a superconducting device of this type has been formed on the surface of an interlayer insulating film such as SiO by a vapor deposition-lift-off process. In general, however, peeling of the resistance film occurs later in the manufacturing process, which is a major obstacle to increasing the yield of the device. SQ as an example of conventional technology
Figure 2 shows an example of forming a resistive film on a UID. In FIG. 2, (a) is the SiO 2 interlayer insulating film 2 formed on the Si wafer 1.
It shows a state in which a resist is applied on the photomask and the pattern of the photomask is developed to form the patterned resist layer 3. In the step shown in (b), after the resistance film 4 made of Pd is formed by vapor deposition, they are immersed in an organic solvent such as acetone and the resist layer 3 is peeled off (this step is called lift-off). In the pattern of the resist layer 3 described above, the resistance film 4 is formed only on the interlayer insulating film 2 as shown in (c). Another interlayer insulating film 5 is formed thereon as shown in (d), and the process is repeated in the same manner to continue the device integration process.

FIG. 3 shows an example of forming a resistance film by the sputtering method. As shown in FIG.
A Mo film 7 is formed on the entire surface of the interlayer insulating film 6 made of O by sputtering.
And a resist mask 8 is formed by a photolithography process. After that, as shown in FIG. 3B, a resist mask portion other than the pattern is removed by using a reactive ion etching device. (c) Next, as shown in FIG. 3 (c), the resist pattern portion is stripped in a solvent such as acetone to obtain a resistive film 7 having a predetermined pattern.
Further, as shown in FIG. 3D, the device integration process is continued while forming a new interlayer insulating film 9.

[0004]

By the way, when a resistance film is formed by the conventional vapor deposition-lift-off method as shown in FIG. 2, the adhesive force of the resistance film formed by vapor deposition to the interlayer insulating film such as SiO 2 is Since the resistance film is not sufficient, peeling of the resistance film occurs along with the progress of processes such as wiring, junction formation, and interlayer insulating film formation performed after the formation of the resistance film, and the yield of the superconducting element obtained as a result of these processes is remarkable. There are problems such as deterioration and deterioration of reliability of the device. One of the reasons why the resistance film formed by the vapor deposition method is easily peeled off during the process is that the energy of particles incident on the substrate is lower in the vapor deposition method than in the sputtering method as shown in FIG. Therefore, the adhesion of the film to the substrate is generally weak. In addition, a thin resist or the like remains on the surface of the pattern-forming resist layer 3 formed as shown in FIG. 2 (a) on the non-resisted surface (that is, the surface on which the resistive film pattern is formed), and it is attached. It has also been pointed out that it is further weakening sex. In order to overcome the latter problem, oxygen gas was introduced into the vapor deposition apparatus before the vapor deposition step shown in FIG. 2B, and a high frequency bias of 13.56 MHz was applied to the wafer 1 to ash it with oxygen plasma. The existing resist is burned with oxygen plasma) to remove the resist remaining at the interface where the film is formed. In this method, the patterned resist layer itself is also scraped, so the film is formed. It is not easy to find conditions that clean the surface and yet minimize damage to the patterned resist layer. Although it is widely practiced to use an inert gas such as argon instead of oxygen, physical damage to the underlying film and the patterned resist layer is unavoidable even with this method.

On the other hand, as shown in FIG. 3, an attempt is made to use a sputtered film of Mo or the like, which has a strong adhesive force, as a resistance film instead of a vapor-deposited film which is easily peeled off, but the sputtered film is generally lifted off. As a result, a pattern cannot be formed, and an etching process using a reactive ion etching apparatus, which is far more complicated than the lift-off method, is required. Moreover, in the etching of the Mo film, which is often used as a resistance film in the sputtering method, it cannot be shared with the etching device for Nb film or SiO 2 film that is most often used in the formation of superconducting elements. There is a need to. That is, if it is attempted to etch Nb with the same etching device after etching Mo, it is known that the subsequent steps become extremely difficult because the etching rate of Nb becomes extremely small. The film etching process requires an etching device separate from the device used for etching the Nb superconducting film and the SiO 2 interlayer insulating film, which are the main parts of the superconducting device. This not only increases the cost of the superconducting device manufacturing equipment, but also increases the number of steps and parameters that must be controlled for the purpose of producing a high-performance superconducting device. If this is seen, the yield and reliability of the device will be reduced.

The present invention solves the above-mentioned problems of the conventional technique and vapor-deposits a resistance film having sufficient adhesive force without introducing a new etching apparatus and complicating the process. Formed by lift-off method, SQUI with high yield
It is an object of the present invention to provide a method for forming a superconducting device capable of producing a superconducting device such as D.

[0007]

In order to achieve the above object, a method of manufacturing a superconducting device according to the present invention is designed such that when a thin film is integrated on a substrate to form a resistance film, an insulator is first formed on the substrate. A film is formed, a resist layer having a predetermined pattern is formed on the insulating film, and the insulating film portion defined by the resist layer is etched to a depth approximately equal to the thickness of the resistance layer to be formed. The resist film is lifted off after the resistance film is deposited on the etched insulation film to form a resistance film having a predetermined pattern in the insulation film. Preferably, the resistive film having a predetermined pattern may be repeatedly formed in each insulating film formed in multiple layers.

[0008]

According to the method of the present invention, the resistance film is not vapor-deposited immediately after the formation of the patterning resist layer, and the interlayer insulating film is removed by an etching apparatus to a thickness of about the same as the resistance film to be formed. By forming the resistance film in the portion where the resistance film is formed, the resistance film is embedded in the interlayer insulation film, that is, formed so as to fit into the interlayer insulation film, not on the surface thereof. Adhesion will be dramatically increased. Further, in this case, since the interlayer insulating film such as SiO 2 is etched, the conventional Nb superconducting film and
The etching apparatus used for processing the SiO 2 interlayer insulating film can be used without any problem, and it is not necessary to introduce a new etching apparatus. Further, the photolithography process for forming the resist pattern can be performed in the same manner as the conventional one.

[0009]

Embodiment An embodiment of the present invention will be described below with reference to FIG. Note that steps (a), (c), (d), and (e) in FIG. 1 are the steps (a), (b), (c), and (d) in FIG. 2 showing the conventional method, respectively.
Is basically the same process. Step (a) An interlayer insulating film 11 made of SiO 2 is formed to a thickness of 4000 angstroms on a 2-inch silicon substrate 10, and a pattern forming resist layer 12 for determining a resistance film pattern is formed on the interlayer insulating film 11. Formed to a thickness of 15000 angstroms. Step (b) The silicon substrate 10 provided with the inter-layer insulator film 11 and the patterned resist layer 12 in the step (a) is put into a reactive ion etching apparatus, and the pressure in the etching chamber is set to 2.67 Pa by CF ₄ gas. Then, with a high-frequency plasma of 13.56 MHz, the power input is 100 W / 250 mmφ, and it is dug down to 400 Å. The etching rate at this time is 5
It was Angstrom / sec. Step (c) In this way, the etching treatment or the sample was transferred to the vapor deposition apparatus, the pressure was evacuated to the order of 10 ⁻⁵ Pa, and the Pd film 13 was deposited to a thickness of 400 Å by electron beam vapor deposition. Step (d) Finally, the sample is soaked in acetone and the patterned resist layer 12 is lifted off, whereby the resistance film 13 having a desired pattern is obtained in a state of being embedded in the interlayer insulating film 11. Step (e) Further, a second interlayer insulating film 14 is formed thereon to a thickness of about the same as the first interlayer insulating film 11, and a contact hole is formed and a superconducting film is formed. ． ． And so on, the process was continued. The resistance film having a desired pattern thus obtained has a sidewall portion of the resistance film 13 also held by the interlayer insulating film 11 as compared with the conventional one as shown in FIG. Was significantly improved, and no resistive film was peeled off during the process when this method was applied in the SQUID manufacturing process. Moreover, there is an advantage that planarization, which is important in producing a laminated element, (that is, the height of the base is made uniform before a new layer is laminated) is performed at the same time. Also step (b)
Since the pattern formation resist layer 12 is dug down in, it is possible to completely remove the resist even if it is left in the area other than the pattern part in the step (a), and improve the adhesion to the base. Become. In the actual fabrication of the SQUID, although not shown in the drawings, superconducting film patterns are formed in the lower and upper layers of the interlayer insulating film 11, respectively.

Although Pd is used as the resistance film in the above embodiment, any material may be used as long as it is a normal conductor that can be formed by the vapor deposition method. As a result, in the case of the conventional sputter etching method as shown in FIG. 3, it cannot be used unless an etching gas is selected according to the resistance film and an appropriate etching condition is selected. It is recognized that the range of application for resistive film materials becomes much wider and effective. In addition, the interlayer insulating film is not limited to SiO ₂ , but if it is an insulator such as SiO ₂ or MgO that is generally used in the production of superconducting elements, it can be processed by a conventional etching device without newly introducing an etching device. It is also possible to easily use the above materials. Further, Nb is most widely used as a superconductor, but it is not necessary to limit it to Nb in the method of the present invention, and the type of substrate used is not limited to the Si wafer.

[0011]

As described above, in the method for manufacturing a superconducting element of the present invention, the resistance film is formed not by being fitted on the surface of the interlayer insulating film but by being fitted therein. While taking advantage of the wide range of materials that can be selected, which is a feature of the evaporation-lift-off method that has been used, and that it is simple in equipment and process, it has excellent adhesion that is not inferior to that of the sputter etching method, and at the same time planarizes It becomes possible to effectively and easily form a resistance film having the feature that

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing various steps of a method according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a method of forming a resistance film by a conventional vapor deposition-liftoff method.

FIG. 3 is a schematic sectional view showing a method of forming a resistance film by a conventional sputter-etching method.

[Explanation of symbols]

 10: Silicon substrate 11: Interlayer insulating film 12: Pattern forming resist layer 13: Pd film (resistive film) 14: Second interlayer insulating film

Claims (2)

[Claims] 1. A method of manufacturing a superconducting device comprising a resistive film formed by integrating thin films on a substrate, wherein an insulating film is formed on the substrate, and a predetermined pattern is formed on the insulating film. Pattern forming resist layer is formed, the insulating film portion defined by the resist layer is etched to a depth approximately equal to the thickness of the resistive layer to be formed, and the resistive film is formed on the etched insulating film. A method for manufacturing a superconducting device, characterized in that the resist layer is lifted off after vapor deposition to form a resistance film having a predetermined pattern in an insulator film. 2. The method for manufacturing a superconducting device according to claim 1, wherein a resistance film having a predetermined pattern is repeatedly formed in multiple layers within an insulating film.