JP2007180492A - How to create a thin layer device - Google Patents

Abstract

A method for producing a thin layer device such as a superconducting element having excellent mechanical strength and useful for submillimeter wave band reception is provided.
A multilayer structure composed of NbN / MgO / NbN-SIS junction is formed on a temporary MgO substrate, SiO ₂ is formed as a substrate on the multilayer structure, and then the temporary MgO substrate is removed by etching. This creates a thin layer device. Since the superconducting element (thin layer device) produced by the method of the present invention has excellent performance and high mechanical strength, it can be easily introduced into a submillimeter wave waveguide.
[Selection] Figure 1

Description

The present invention relates to a method for producing a thin layer device, and more particularly to a method for producing a thin layer device such as a superconducting element having a SIS junction on a SiO ₂ substrate, and a superconducting element.

  In the fields of global environment measurement, radio astronomy, and next-generation wireless communication, the development of receivers and oscillators in the submillimeter wave band is desired, and one of them is research and development of superconducting devices such as Josephson junctions. . When a direct current is passed through a superconducting SIS (Superconductor-Insulator-Superconductor) junction, which is one of the Josephson junctions, a superconducting tunnel current flows between two superconducting electrodes up to a certain current value. A characteristic is that a voltage is generated between two superconducting electrodes. Moreover, the current-voltage characteristic of this junction has a very strong non-linear characteristic that cannot be achieved by a semiconductor device.

  At present, in the submillimeter wave band of 300 GHz or higher, the SIS electromagnetic wave receiver using the SIS junction as a mixer element has the lowest noise. For example, the SIS junction based on niobium (Nb) is already used for the pole up to the 725 GHz band. Low noise SIS electromagnetic wave receivers have been developed. However, at a frequency higher than 725 GHz, the performance of the SIS electromagnetic wave receiver rapidly deteriorates due to an increase in electrode loss accompanying the destruction of the superconducting electron pair in the Nb electrode.

  Accordingly, development of SIS electromagnetic wave receivers using niobium nitride (NbN) or the like having a large superconducting gap energy and extremely low loss characteristics up to 1.4 THz has been carried out. However, the ultra-low loss characteristics of NbN in the submillimeter wave band depend greatly on the crystallinity of the NbN thin film, and the technology for making a device while maintaining good crystallinity is introduced in the development of NbN submillimeter wave devices. is required. That is, it is necessary to configure the SIS junction using NbN only with a multilayer film such as NbN, MgO or the like obtained by epitaxial growth.

On the other hand, SiO ₂ having a low dielectric constant has been conventionally used as a substrate for the production of submillimeter wave receivers. However, there has been no report of NbN epitaxial growth using a SiO ₂ substrate, and MgO and the like are currently not available. Rock salt type single crystal substrates are frequently used. Actually, a technique for forming a SIS junction (hereinafter referred to as NbN / MgO / NbN-SIS junction) composed of an NbN layer / MgO layer / NbN layer on an MgO substrate is disclosed (Patent Document 1). In this publication, an NbN layer, a thin MgO layer, and an NbN layer are formed on each MgO substrate by heteroepitaxial growth.

The sub-millimeter wave waveguide mixer needs to be formed on a substrate that is sufficiently thinner than the wavelength in the waveguide. As a guide, the substrate thickness of the 1 THz waveguide mixer needs to be ¼ or less of the wavelength of the electromagnetic wave in the substrate, that is, approximately 40 μm or less for the SiO ₂ substrate and 27 μm or less for the MgO substrate. It is difficult to create a device with a substrate of this thickness while securing a sufficient area. Generally, a SIS junction is formed on a substrate of several hundred μm thickness, and finally the substrate is mechanically polished. The target substrate thickness is adjusted.

An NbN-based SIS mixer created on an MgO substrate by such a method has been introduced into a submillimeter wave waveguide mixer, and exhibits a certain performance (Non-patent Document 1).
JP 2001-352109 A Waveguide-type all-NBN SIS mixers on MgO substrates by Masanori Takeda et al., Advanced Research Center, National Institute of Information and Communications Technology

  However, since the MgO single crystal substrate is easily cleaved by cleavage or the like, and the mechanical strength is lowered by making the substrate thinner, it is substantially difficult to obtain an arbitrary substrate thickness with good reproducibility.

Therefore, the present invention can ensure an excellent mechanical strength and a sufficient thickness in which an epitaxial multilayer structure such as an NbN / MgO / NbN-SIS junction is disposed on a SiO ₂ substrate useful as a submillimeter wave band material. It aims at providing the manufacturing method of a thin layer device.

  Another object of the present invention is to provide a thin layer device obtained by the above production method, a SIS mixer comprising the thin layer device, and a HEB (Hot-electron Bolometer) electromagnetic wave receiver.

In order to solve the above-described problems, the NbN / MgO / NbN-SIS junction fabrication technique was examined in detail. As a result, MgO was used as a temporary substrate, and the NbN layer / MgO layer / NbN layer formed by epitaxial growth on the temporary substrate. (hereinafter, also referred to as an epitaxial NbN / MgO / NbN.) create the epitaxial NbN / MgO / NbN-SIS junction consisting, then as the substrate, the SiO ₂ having a thickness of 10μm was prepared by the epitaxial growth NbN / MgO / A thin layer in which the NbN / MgO / NbN-SIS junction is disposed on SiO ₂ having a thickness of several tens of μm by forming a film on the NbN-SIS junction and then removing the MgO temporary substrate with an acid or the like. The ability to create devices, and especially SiO ₂ substrates with excellent mechanical strength and effective as submillimeter wave band materials Using the thin layer device having the NbN / MgO / NbN-SIS junction disposed thereon, it has been found that a superconducting element, a mixer, and a HEB electromagnetic wave receiver comprising the thin layer device can be obtained. Was completed.

According to the present invention, SiO ₂ having a thickness of several tens of μm is formed as a substrate by a film forming method, and the MgO temporary substrate is removed by etching, so that no uniform polishing technique is required, and SiO ₂ having a relatively low dielectric constant. Therefore, compared to the case where MgO is used as the substrate, a sufficient substrate thickness can be secured, and a superconducting element excellent in mechanical strength can be manufactured. In addition, since a substrate such as SiO _{2 is formed by a} film forming method, excellent substrate thickness control is possible.
Examples of the thin layer device include superconducting elements such as SIS mixers and HEB electromagnetic wave receivers. In addition, a grounding conductor (ground) thin film can be produced by film formation and lithography at the time of producing a thin layer device, and reliable and satisfactory grounding can be achieved.

  The first of the present invention is a method for producing a thin-layer device, in which a multilayer structure formed by laminating thin films is formed on a temporary substrate, and then a substrate is formed on the multilayer structure.

  In the present invention, the temporary substrate is not particularly limited as long as it can form a multilayer structure and can be removed with an acid or the like. When the multilayer structure is composed of an epitaxially grown NbN layer, MgO layer, and NbN layer, an MgO single crystal substrate is preferable as a substrate suitable for epitaxial growth of the NbN layer.

  The multilayer structure is preferably a multilayer composed of thin films formed by epitaxial growth, and the configuration thereof can be appropriately selected according to the intended use of the resulting thin layer device. For example, when the thin layer device is a superconducting element, it is preferably a multilayer structure capable of forming a SIS junction. For example, an NbN layer obtained by epitaxial growth is used as a superconducting layer, and a single crystal MgO is used as an insulating layer. A multilayer structure composed of NbN layer / MgO layer / NbN layer as a layer can be used.

The substrate can be appropriately selected from SiO ₂ , MgO, Al ₂ O _{3 and the} like according to the intended use of the thin layer device to be obtained. Among these, SiO ₂ is suitable for use in a submillimeter wave receiver because of its low dielectric constant, and can be formed in the range of several tens of nanometers to several tens of micrometers. Moreover, since it can set thickly compared with the case where MgO is used as a substrate, the substrate strength at the time of element cutting can be sufficiently secured. MgO is advantageous in that it can be epitaxially grown and has high thermal conductivity, excellent lattice matching with NbN, and the like.

  Hereinafter, as an example of the thin layer device of the present invention, a method for manufacturing a thin layer device in which the multilayer structure is an NbN / MgO / NbN-SIS junction formed by epitaxial growth will be described.

FIG. 1 shows a superconducting element as an example of a preferred embodiment of a thin layer device obtained by the production method of the present invention. 30 is an epitaxial NbN layer, 40 is an epitaxial MgO layer which is an insulating layer, 50 is an epitaxial NbN layer, 60 is a SiO ₂ substrate, 80 is a wiring layer, and 85 is an NbN / MgO / NbN-SIS junction. The epitaxial NbN / MgO / NbN multilayer film forms an NbN / MgO / NbN-SIS junction, and a SiO ₂ substrate is laminated on this multilayer structure to form a superconducting element. In order to obtain a high-performance superconducting element as a thin layer device by the formation method of the present invention, an NbN layer (30), an MgO layer (by epitaxial growth) on a temporary substrate (not shown) provided below the NbN layer (30). 40), forming an epitaxial NbN / MgO / NbN-SIS junction obtained by laminating the NbN layer (50), forming a wiring layer (80) on the SIS junction and completing the SIS junction; Then, SiO ₂ is formed on the SIS junction to form a substrate (60), and then the temporary MgO substrate is removed by wet etching. Thereby, the epitaxial NbN / MgO / NbN-SIS junction is transferred to the SiO ₂ substrate.

  In addition, in order to prevent the SIS junction from being eroded by an etchant during wet etching for removing the temporary substrate, an etching protective layer is formed on the temporary substrate in advance, and then the etching protective layer is formed on the temporary protective substrate. The multilayer structure may be formed. Hereinafter, the manufacturing method of the present invention will be described with reference to the drawings.

  First, as shown in FIG. 2, an etching protective layer is formed on a temporary substrate (10) made of a single crystal such as MgO. As the etching protection layer, it is preferable to have etching resistance because it prevents erosion to the SIS junction during etching, and a multilayer structure needs to be formed on the etching protection layer. It is preferable to have characteristics suitable for forming a multilayer structure such as epitaxial growth. In the present invention, the etching protective layer may be a single layer or a multilayer of two or more layers as long as it has the above characteristics. In the present invention, it is desirable to use at least a non-acid soluble rock salt structure layer such as an NbN thin film as the etching protective layer. However, when a conductive material such as an NbN thin film is used as the non-acid-soluble rock salt structure layer, it becomes a problem in the circuit, so that it is finally necessary to remove it. Therefore, when a conductive material is used as the etching protective layer, it is preferable to form a dielectric layer made of a rock salt structure, such as an MgO thin film. Since the MgO thin film has high fluorine plasma resistance, after removing the temporary substrate (10) by etching, a non-acid soluble rock salt structure layer (21) such as NbN is removed by fluorine plasma. Can be protected.

  Therefore, in the present invention, a non-acid-soluble rock salt structure layer (21) such as NbN is first formed on the temporary substrate (10), and then a dielectric layer (23) made of the rock salt structure is formed thereon, Two layers of a rock salt structure layer (21) and a dielectric layer (23) are preferably used as an etching protective layer. In addition, examples of the non-acid soluble rock salt structure (21) include a TiN thin film. Formation of each layer constituting the etching protective layer is preferably epitaxial growth, and may be a method using high frequency sputtering or DC reactive sputtering, or a combination thereof. The thickness of the rock salt structure layer (21) is not particularly limited as long as it has a resistance capable of protecting the element from erosion by the etching agent, and is preferably 10 to 200 nm. The thickness of the dielectric layer (23) is not particularly limited, but is preferably 10 to 100 nm.

  Next, as shown in FIG. 3, an NbN layer (30) and an MgO layer (40) are formed on the etching protection layers (21, 23) in order to form an epitaxial NbN / MgO / NbN-SIS junction which is a multilayer structure. The NbN layer (50) is formed. First, an NbN layer (30) is formed on the etching protection layers (21, 23) by epitaxial growth, and then an MgO layer (40) is formed. The MgO layer (40) may be formed by epitaxial growth, and may be, for example, a method using high frequency sputtering or direct current reactive sputtering, or a combination thereof. Next, an NbN layer (50) is epitaxially grown on the MgO layer (40). In the present invention, these are preferably formed by epitaxial growth. The NbN layer (30), the MgO layer (40), and the NbN layer (50) are a lower electrode layer, a dielectric layer, and an upper electrode layer, respectively.

  In addition, since the NbN / MgO / NbN trilayer film, which is the multilayer structure, functions as an NbN / MgO / NbN-SIS junction, the MgO layer (40) serving as a dielectric layer needs to be an ultrathin film. is there. As a method for producing such an NbN / MgO / NbN-SIS junction, a conventionally known method can be applied.

  For example, as shown in FIG. 4, a photoresist layer (70) is applied on an NbN / MgO / NbN trilayer film and patterned by photolithography. The exposed portion of the three-layer film, that is, the NbN layer (50), MgO (40), and NbN (30) is removed by reactive etching using fluorine plasma or the like, and then the photoresist layer (70) is removed with a solvent. . Next, as shown in FIG. 5, a resist (75) is applied, and the resist other than the portion that becomes the SIS junction is removed by photolithography, and the exposed portion of the three-layer film, that is, the NbN layer (50) is fluorine plasma or the like. It is removed by the reactive etching used. Thereafter, an MgO layer (40) is formed around the SIS junction as an insulating layer. Next, the photoresist (75) is removed with a solvent, so that the MgO layer (40) formed on the SIS junction is also removed (referred to as a lift-off method). Next, in order to form a wiring layer (80), an NbN layer is formed on the entire surface by epitaxial growth. A resist is applied, the resist other than the portion that becomes the wiring layer is removed by photolithography, and the exposed NbN layer is removed by reactive etching using fluorine plasma or the like to form a wiring layer (80). As a result, as shown in FIG. 6, an NbN / MgO / NbN-SIS junction (85) as a multilayer structure is formed on the NbN layer (21) and MgO layer (23) as etching protective layers. .

Next, wet etching using phosphoric acid or the like as an etching solution is performed to remove the exposed MgO layer. As shown in FIG. 7, the MgO layer (40) on the outer periphery of the wiring layer (80) is removed with phosphoric acid (90) or the like. Thereby, the MgO layer (40) and a part of the MgO thin film (23) which is an etching protective layer are also removed. After the next SiO ₂ film is formed on the SIS junction by this process, the only MgO exposed to the etching agent is the temporary substrate (10). Note that the etching agent used for wet etching is not limited to phosphoric acid as long as unnecessary MgO can be removed, and other etching agents can be used.

Next, as shown in FIG. 8, a substrate (60) such as SiO ₂ is formed on the SIS junction (85). Thus, after the NbN / MgO / NbN-SIS junction as a multilayer structure (85) is preformed, SIS by forming a SiO ₂ substrate on the multilayer structure, the substantially SiO ₂ substrate Thin layer devices can be created in which the junctions are disposed. In the present invention, SiO ₂ as the substrate (60) can be formed by high-frequency sputtering or direct-current reactive sputtering, and the thickness can be appropriately selected according to the substrate dielectric constant and the intended frequency of use. Generally, in the case of 1 THz, it is 40 μm or less.

  Next, the MgO substrate as the temporary substrate (10) is removed by wet etching using an etching agent such as phosphoric acid (90) (see FIG. 9). Next, the NbN thin film used as the wet etching protective layer (21) is removed by a reactive etching apparatus. Finally, the MgO thin film (23) remaining in the lower part of the SIS junction is removed with phosphoric acid, whereby the superconducting element as the target thin layer device shown in FIG. 1 is manufactured.

According to the production method of the present invention, the SiO ₂ substrate is formed so as to enclose the NbN / MgO / NbN—SIS junction. The thickness of the SiO ₂ substrate is 40 μm or less due to its dielectric constant at a use frequency of 1 THz. According to the present invention, since a temporary substrate such as MgO is removed by etching, a uniform polishing technique is not necessary, and a SiO ₂ layer having a relatively low dielectric constant can be used as a substrate, so that a sufficient substrate thickness can be secured. A superconducting element having excellent mechanical strength can be produced. Further, since a substrate such as SiO _{2 is formed by a} film forming method, excellent substrate thickness control is possible.

In the case of producing a ground conductor, after forming a SiO ₂ film on the epitaxial NbN / MgO / NbN-SIS junction, a conductor thin film may be further formed and patterned.

  In fields where a receiver in the THz frequency range is required, such as global environment measurement, radio astronomy, and communications, the epitaxial NbN is the most excellent in the frequency range of 725 GHz to 1.4 THz, which is currently the gap frequency of niobium. Low loss material. A superconducting SIS electromagnetic wave receiver using epitaxial NbN has a possibility of becoming an excellent low noise electromagnetic wave receiver in this frequency band, and an HEB electromagnetic wave receiver is a number in which the SIS electromagnetic wave receiver is difficult to operate. It is a low noise electromagnetic wave receiver having excellent characteristics in the frequency range of THz.

The present invention is excellent in mechanical strength and low loss when actually used in such a region, and is applicable to all electromagnetic wave receivers for waveguides used in the field of earth environment measurement, radio astronomy, and next-generation wireless communication. This is an extremely effective technology. According to the present invention, an excellent epitaxial NbN / MgO / NbN-SIS electromagnetic wave detector or the like as a thin layer device can be configured on a SiO ₂ substrate effective as a submillimeter wave band material, and conventional substrate polishing can be performed. Technology can be eliminated. Specifically, it is applied to the creation of thin layer devices such as HEB and SIS electromagnetic wave receivers in the submillimeter wave band, various detectors such as X-ray detectors, infrared bolometers, terahertz detectors, and other semiconductor devices and superconductor devices. Is possible.

  EXAMPLES Next, although an Example is given and this invention is demonstrated concretely, these Examples do not restrict | limit this invention at all.

Example 1
As a thin layer device of the present invention, a thin layer device was prepared in which an epitaxial NbN / MgO / NbN-SIS junction was formed as a multilayer structure on a SiO ₂ substrate.

  First, an NbN thin film is epitaxially grown to a thickness of 100 nm on an MgO temporary substrate having a thickness of 300 μm, and then an epitaxial MgO thin film having a thickness of 20 nm is used as an etching protective layer on the NbN thin film by rf sputtering and DC reactive sputtering. Formed.

Further, an NbN epitaxially grown lower electrode layer having a thickness of 200 nm and an MgO layer having a thickness of about 0.7 nm are formed by rf sputtering on the MgO thin film serving as an etching protective layer, and then epitaxially grown to form a 200 nm thick layer. An NbN layer was formed as the upper electrode layer. Based on this, an epitaxial NbN / MgO / NbN-SIS junction was prepared, and then the MgO layer around the NbN / MgO / NbN-SIS junction was removed using a phosphoric acid solution as an etching agent. Next, a SiO ₂ substrate having a thickness of 20 μm was formed on the NbN / MgO / NbN—SIS junction, which is a multilayer structure, by high frequency sputtering. Next, the MgO temporary substrate is removed using phosphoric acid as an etching agent, the NbN thin layer as an etching protective layer is removed by reactive etching, and finally the MgO layer as an etching protective layer using phosphoric acid. Was removed.

Thus, the SiO ₂ on the substrate to form a thin layer device consisting of NbN / MgO / NbN-SIS junction as a multilayer structure.

Example 2
As a thin-layer device of the present invention, an 870 GHz band waveguide SIS mixer was prepared. A micrograph of the obtained waveguide SIS mixer is shown in FIG. Here, FIGS. 10A and 10B are diagrams in which a SIS mixer for a waveguide on a SiO ₂ substrate is cut with a dicing saw, and FIG. 10C is a SIS mixer from the side of the SiO ₂ substrate of about 20 μm. It is the figure observed through the part.

The warpage of the SiO ₂ substrate and the cross section of the obtained SIS mixer for waveguide were evaluated. The results are shown in FIG. As shown in FIG. 11A, the warpage of the substrate was evaluated in a region having a length of about 1 mm. As a result, it was confirmed that the central portion was raised by about 0.7 μm from the peripheral portion. This means that there is little stress in the substrate and it has excellent flatness.

FIG. 11B shows the result of measuring the SiO ₂ substrate thickness with a laser microscope. The substrate thickness was about 21 μm, which almost coincided with the substrate thickness of 20.2 μm expected from the deposition rate (error + 4%), and good substrate thickness controllability was obtained.

Moreover, the result of having evaluated the current-voltage characteristic of this SIS junction is shown in FIG. The non-linearity peculiar to the SIS junction and the accompanying hysteresis characteristics were confirmed. Since this junction has a high critical current density of Jc = 30 kA / cm ² , the nonlinearity is weak, but it is equivalent to the characteristic high gap voltage (rise of current near 5.3 mV) of the epitaxial SIS junction and 1.3 THz. Thus, a clear resonance step due to the junction structure that can be confirmed up to around 2.7 mV can be confirmed, indicating that an epitaxial SIS junction is formed on the SiO ₂ substrate.

FIG. 1 is a cross-sectional view showing a superconducting element as an example of a thin layer device obtained by the production method of the present invention. For example, NbN (30) can be 200 nm, MgO layer (40) can be 250 nm, NbN layer (50) can be 200 nm, SiO ₂ layer (60) can be 20 μm Wire NbN (80), 350 nm. FIG. 2 is an explanatory view showing one step of a method of manufacturing a superconducting element as an example of the thin layer device of the present invention, in which an etching protective layer is laminated on a temporary MgO substrate. For example, the NbN layer (21) on the MgO temporary substrate (10) can be 100 nm and the MgO layer (23) can be 20 nm. FIG. 3 is an explanatory view showing one step of a method of manufacturing a superconducting element as an example of a thin layer device of the present invention, and is a multilayer comprising an NbN layer, an MgO layer and an NbN layer on an MgO temporary substrate and an etching protective layer. It is a figure which shows the state by which the structure was laminated | stacked. The MgO layer (40) between the NbN layer (30) and the NbN layer (50) can be 0.7 nm. FIG. 4 is an explanatory view showing one step of a method of manufacturing a superconducting element as an example of the thin layer device of the present invention, and shows a state in which an NbN / NgO / NbN layer is patterned with a photoresist layer. FIG. 5 is an explanatory view showing one step of a method of manufacturing a superconducting element as an example of the thin layer device of the present invention, and is a view showing a state in which a SIS junction is formed. FIG. 6 is an explanatory view showing one step of a method of manufacturing a superconducting element as an example of the thin layer device of the present invention, in which a SIS junction is formed by forming and patterning a wiring layer on the upper part of the SIS junction. It is a figure which shows a state. FIG. 7 is an explanatory view showing one step of a method of manufacturing a superconducting element as an example of the thin layer device of the present invention, and showing a state in which the MgO layer exposed on the outer periphery of the wiring layer is removed. . FIG. 8 is an explanatory view showing one step of a method of manufacturing a superconducting element as an example of a thin layer device of the present invention, in which a substrate layer made of SiO ₂ is laminated on an NbN / MgO / NbN—SIS junction. FIG. FIG. 9 is an explanatory view showing one step of the method of manufacturing a superconducting element as an example of the thin layer device of the present invention, and shows a state where the MgO temporary substrate is removed by etching using phosphoric acid. FIG. 10 is a diagram showing a SIS mixer for a waveguide in which an epitaxial NbN / MgO / NbN—SIS junction is formed on a SiO ₂ substrate as an example of the thin layer device of the present invention. (A) and (b) is a view taken along the guiding SIS mixer for waveguide on SiO ₂ substrate with a dicing saw, is a diagram tried through the SiO ₂ substrate from the substrate rear side (c) is SIS mixer . 11A and 11B are diagrams showing evaluation of a SiO ₂ substrate of a superconducting element as an example of the thin layer device of the present invention, where FIG. 11A shows a warp and FIG. 11B shows a thickness of the substrate. FIG. 12 is a diagram showing current-voltage measurement of a superconducting element as an example of the thin layer device of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... MgO temporary substrate, 21 ... Etch protection layer (non-acid soluble rock salt structure layer), 23 ... Etch protection layer (dielectric layer), 30 ... NbN layer, 40 ... MgO layer, 50 ... NbN layer, 60 ... substrate, 70 ... photoresist layer, 75 ... photoresist, 80 ... wiring layer, 85 ... SIS junction, 90 ... phosphorus acid.

Claims (13)

  A method for producing a thin layer device, wherein a multilayer structure formed by laminating thin films is formed on a temporary substrate, and then a substrate is formed on the multilayer structure.   The method for producing a thin layer device according to claim 1, wherein an etching protective layer is formed on the temporary substrate, and then the multilayer structure is formed on the etching protective layer.   The method for producing a thin layer device according to claim 2, wherein the temporary substrate is removed by etching after the substrate is formed on the multilayer structure.   The etching protection layer includes a non-acid soluble rock salt structure layer formed on the temporary substrate and a dielectric layer made of the rock salt structure. After the substrate is formed on the multilayer structure, the temporary protection layer is formed. The method for producing a thin layer device according to claim 3, wherein the substrate is removed by wet etching, and then the non-acid soluble rock salt structure layer is removed by reactive etching.   The method for producing a thin layer device according to claim 4, wherein the dielectric layer made of the rock salt structure is removed by wet etching after the non-acid soluble rock salt structure layer is removed by reactive etching.   6. The method for producing a thin layer device according to claim 5, further comprising a step of forming a good ground conductor by forming and patterning a conductive material on the substrate after forming the substrate on the multilayer structure.   The method for producing a thin layer device according to claim 1, wherein the temporary substrate is a single crystal substrate.   The method for producing a thin layer device according to claim 1, wherein the temporary substrate is made of MgO.   The method for producing a thin layer device according to claim 1, wherein the multilayer structure is a multilayer formed by epitaxial growth.   The method for producing a thin layer device according to claim 9, wherein the multilayer structure is NbN layer / MgO layer / NbN layer. The method for producing a thin layer device according to claim 1, wherein the substrate is made of SiO ₂ .   A thin layer device produced by the method for producing a thin layer device according to claim 1.   A superconductive element, a SIS mixer or a HEB electromagnetic wave receiver comprising the thin layer device according to claim 12.

Images