JP5967610B2 - Photon detector using superconducting tunnel junction. - Google Patents

Description

  The present invention relates to a photon detector using a superconducting tunnel junction, in which a lower electrode made of a superconductor, a tunnel barrier made of an insulator, and an upper electrode made of a superconductor are laminated on a substrate. It is.

  Conventionally, a semiconductor detector has been mainly used as a photon detector. However, the semiconductor detector cannot be further improved in performance due to the inherent properties of the semiconductor material. On the other hand, a photon detector using a superconducting tunnel junction (hereinafter referred to as STJ (= Superconducting Tunnel Junction)) is excellent in energy resolution for discriminating photons having close energy and high-speed photon observation. Therefore, it is extremely promising as a next-generation photon detector.

  FIG. 1A is a schematic diagram of an STJ element 1 constituting a photon detector using an STJ. The STJ element 1 is formed by sandwiching an insulator 4 between superconductors 2 and 3. When the STJ element 1 is operated, the STJ element 1 is cooled and the excitation current due to heat is reduced. In addition, a bias voltage is applied between the superconductors 2 and 3. Here, a DC Josephson current flows through STJ. The graph shown in FIG. 5B shows the current-voltage characteristics of the STJ element 1. In the graph, the horizontal axis represents voltage, and the vertical axis represents current. In the graph, the DC Josephson current represented by the characteristic B flows when the voltage is zero. In addition, a characteristic A unique to STJ that does not increase linearly with increasing voltage and that is extremely nonlinear appears. When the STJ element 1 is operated, a magnetic field is applied to the insulator 4, and the DC Josephson current is suppressed by applying this magnetic field.

  As shown in the energy band diagram of FIG. 3C, the Cooper pair 5 responsible for superconductivity in the STJ element 1 is in the ground state under the operating conditions of the STJ element 1 described above. When a photon is incident on the STJ element 1 as shown by a thick arrow in FIG. 5A and energy of a pair breakdown energy of 2Δ or more is given to the Cooper pair 5, the Cooper pair 5 is collapsed to be a quasiparticle in an excited state. 6 The quasiparticle 6 passes through the STJ formed in the insulator 4 and forms a tunnel current. The tunnel current is represented by a current-voltage characteristic C indicated by a dotted line in FIG. 5B, and a difference from the characteristic A is amplified by an amplifier (AMP) 7 and measured. By this measurement, the number and energy of photons incident on the STJ element 1 are grasped.

  The breakdown energy 2Δ is several eV in the semiconductor detector, whereas it is several meV in the photon detector using the STJ, and the Cooper pair 5 becomes the quasiparticle 6 with much smaller energy. Therefore, the photon detector using STJ exhibits excellent energy resolution.

  FIG. 2 is a cross-sectional perspective view of a conventional photon detector 11 using an STJ. As such a photon detector, there is one disclosed in Non-Patent Document 1.

The photon detector 11 is configured by forming an STJ element 12 on a substrate 13. The STJ element 12 is formed by laminating a lower electrode 14 made of a superconductor, a layer 15 including a tunnel barrier made of an insulator, and an upper electrode 16 made of a superconductor on a substrate 13. Here, Nb is used for the superconductors of the lower electrode 14 and the upper electrode 16, and the thicknesses are 200 nm and 150 nm, respectively. The AlO _x layer 15b constituting the tunnel barrier which is an insulator is formed to a thickness of several nm by oxidizing the surface of the Al layer 15a. The Al layer 15a and the Al layer 15c are trap layers for amplifying secondary electrons generated by the incidence of photons, and may not be formed.

An interlayer insulating film 17 made of SiO ₂ is formed to a thickness of 350 nm on the surface of the substrate on which the STJ element 12 is formed, and an upper electrode wiring layer 18 made of Nb is 650 nm on the upper right side of the interlayer insulating film 17. It is formed in the thickness. The upper electrode wiring layer 18 is connected to the upper electrode 16 through a contact hole 19. Although not shown, a lower electrode wiring layer made of Nb is formed on the upper left side of the interlayer insulating film 17, and is connected to the lower electrode 14 through a contact hole in the same manner as the upper electrode wiring layer 18. It is connected.

  FIGS. 3A to 3H and FIGS. 4I to 4K are cross-sectional views showing a process for manufacturing the conventional photon detector 11 as described above using the lift-off method. In FIGS. 3 and 4, the same or corresponding parts as those in FIG.

In producing the photon detector 11, first, a lift-off photoresist 21 is formed on the substrate 13 (see FIG. 3A). Next, on the substrate 13 and the photoresist 21, the Nb layer 22 that becomes the lower electrode 14, the Al—AlO _x or Al—AlO _x / Al layer 23 that becomes the layer 15 including the tunnel barrier, and the Nb layer that becomes the upper electrode 16 24 are stacked (see FIG. 4B). Next, the photoresist 21 is lifted off to form the lower electrode 14 (see FIG. 5C). Subsequently, a photoresist 25 for processing the upper electrode is formed (see FIG. 4D), and the tunnel barrier 15 and the upper electrode 16 are formed by etching using the photoresist 25 as a mask (see FIG. 5E).

  Next, a photoresist 26 for forming a contact hole is formed (see (f) in the figure), and then an interlayer insulating film 17 is laminated (see (g) in the same figure). Thereafter, the photoresist 26 is lifted off to form a contact hole 19 (see FIG. 11H). Next, a photoresist 27 for forming a wiring layer is formed (see FIG. 4I), and a wiring layer 28 is deposited (see FIG. 4J). Thereafter, the photoresist 27 is lifted off to form the upper electrode wiring layer 18 and the lower electrode wiring layer 20 (see FIG. 10 (k)), thereby completing the production of the photon detector 11.

  Further, in order to select the type of photons incident on the upper electrode 16 of the STJ element 12, the interlayer insulating film 17a immediately above the upper electrode 16 may be removed, and an absorption layer may be formed in the removed portion. With this absorption layer, desired photons incident on the photon detector 11 are captured and incident on the upper electrode 16, so that it is possible to efficiently detect the desired photons. Although the case where the photon detector 11 is manufactured by the lift-off method has been described here, the photon detector 11 can be similarly manufactured by the etching method.

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL.13, NO.2, JUNE 2003, pp.119-122

  Since the photon detector 11 using the conventional STJ requires many processes for production as described above, it is difficult to reduce the production cost and the production yield is low. Further, the formation of the contact hole 19 in the interlayer insulating film 17 by the etching method and the deposition of the wiring layer 28 on the interlayer insulating film 17 adversely affects the STJ element 12, and the characteristics as the photon detector 11 are deteriorated. It is possible. Further, since various layers are projected and stacked on the substrate 13 to form the photon detector 11, another element is further stacked three-dimensionally on the photon detector 11 to increase the degree of circuit integration. Was difficult. Further, by forming an absorption layer on the upper electrode 16 of the STJ element 12, it becomes possible to select photons to be detected. However, the interlayer insulating film 17a immediately above the upper electrode 16 is removed, and the removed portion absorbs the photons. More formation processes were required to form the layer, which was troublesome.

The present invention has been made to solve such problems,
In a photon detector using an STJ in which a lower electrode made of a superconductor, a tunnel barrier made of an insulator, and an upper electrode made of a superconductor are stacked on a substrate,
An STJ element composed of a lower electrode, a tunnel barrier, and an upper electrode is formed by being embedded in a hole formed in a recess in the surface of the substrate, and the difference in height between the surface of the upper electrode and the surface of the substrate is It is characterized by being set within the thickness range .

  In a conventional photon detector using an STJ, the upper electrode is at a height separated from the substrate surface by the thickness of the lower electrode and the tunnel barrier, and an STJ element is used to form a wiring layer in contact with the upper electrode. A contact hole for exposing the covering interlayer insulating film and the upper electrode was required. However, according to this configuration, the STJ element is formed by being embedded in a hole formed in the surface of the substrate so that the height of the upper electrode from the substrate surface is equal to the thickness of the lower electrode and the tunnel barrier. It can be lowered. Therefore, a wiring layer in contact with the upper electrode can be formed on the substrate surface without forming an interlayer insulating film and a contact hole. Therefore, the conventional manufacturing process for forming the interlayer insulating film and the contact hole and the apparatus for manufacturing the interlayer insulating film are not required, and the manufacturing process and the manufacturing apparatus of the photon detector using the STJ are greatly simplified. . As a result, the manufacturing yield is improved and the manufacturing cost is reduced. In addition, since an interlayer insulating film is not manufactured, the STJ element is not adversely affected by the conventional formation of contact holes in the interlayer insulating film and the deposition of wiring layers on the interlayer insulating film, and the photon detector can be used as a photon detector. There is no deterioration of the characteristics. In addition, since the STJ element can be formed without protruding on the substrate, another element can be three-dimensionally stacked on the photon detector composed of the STJ element and easily mounted three-dimensionally. I can do it. For this reason, it is possible to easily increase the degree of circuit integration, and it is also possible to easily array photon detectors using STJ.

  Further, the present invention is characterized in that the surface of the upper electrode and the surface of the substrate are formed flush or substantially flush.

  According to this configuration, since the surface of the upper electrode of the STJ element and the surface of the substrate have the same or substantially the same height, no step is generated between the STJ element and the substrate surface. Therefore, various layers to be stacked on the STJ element can be formed flat, and other elements can be more easily formed three-dimensionally on the STJ element.

  Further, according to the present invention, a part of the lower electrode is formed to be exposed in the hole, and a wiring layer for wiring the lower electrode is formed on the surface side of the substrate in contact with a part of the lower electrode exposed to the hole. The wiring layer for wiring the upper electrode is formed on the surface side of the substrate in contact with the surface of the upper electrode.

  According to this configuration, the wiring layer for wiring the lower electrode and the wiring layer for wiring the upper electrode are both formed on the surface side of the substrate without forming the interlayer insulating film. For this reason, the photon detector using STJ suitable for the single-sided mounting of a board | substrate is provided.

  Further, according to the present invention, a through hole leading from the back surface of the substrate to the lower electrode is formed, and a wiring layer for wiring the lower electrode is formed on the back surface side of the substrate in contact with the lower electrode through the through hole. A wiring layer to be wired is formed on the surface side of the substrate in contact with the surface of the upper electrode.

  According to this configuration, the wiring layer for wiring the lower electrode is in contact with the lower electrode through the through hole formed on the back surface of the substrate, and the wiring layer for wiring the upper electrode on the back surface side of the substrate is the upper electrode. It is formed without forming an interlayer insulating film on the surface side of the substrate in contact with the surface of the substrate. Therefore, only the wiring layer for wiring the upper electrode is formed on the surface side of the substrate, and the STJ element is exposed on the substrate surface as much as it is covered by the wiring layer for wiring the lower electrode. For this reason, a photon detector using an STJ having an increased photon detection area and high photon detection sensitivity is provided.

  Further, the present invention is characterized in that an absorption layer made of a material and a thickness corresponding to the type of photon to be detected is formed on the surface of the substrate on which the STJ element is formed.

  According to this configuration, the absorption layer of various materials and various thicknesses can be formed without requiring a manufacturing process of forming an absorption layer by removing the interlayer insulating film immediately above the upper electrode as in the prior art. It can be easily formed on the STJ element. Accordingly, by forming absorption layers of various materials and various thicknesses on the STJ element, the types of photons to be detected can be easily changed in various ways. Therefore, a photon detector using an STJ that can measure photons in a wide energy band with high detection efficiency is easily provided.

  According to the present invention, as described above, the photon detector manufacturing process using the STJ is greatly simplified, the manufacturing yield is improved, and the manufacturing cost is reduced. Further, the STJ element is not adversely affected in the manufacturing process, and the characteristics as a photon detector are not deteriorated. In addition, other elements can be three-dimensionally stacked on the photon detector and can be easily mounted three-dimensionally, so that the degree of circuit integration can be easily increased, and an array of photon detectors using STJ is provided. Can be easily performed.

(A) is a schematic diagram of the STJ element which comprises the photon detector using STJ, (b) is a graph showing the current voltage characteristic of an STJ element, (c) is an energy band figure of STJ. It is a cross-sectional perspective view of the conventional photon detector using STJ. (A)-(h) is sectional drawing which shows the process of producing the conventional photon detector using STJ using the lift-off method. (I)-(k) is sectional drawing which shows the preparation process of the photon detector performed following the process shown in FIG. It is sectional drawing of the photon detector using STJ by one embodiment of this invention. FIG. 6 is a cross-sectional view showing a process for manufacturing the photon detector according to the embodiment shown in FIG. 5 using a lift-off method. FIG. 7 is a plan view simulating a photomicrograph of a photon detector produced according to the process shown in FIG. 6. It is a graph which shows the current-voltage characteristic of the STJ element measured in order to evaluate the photon detector produced according to the process shown in FIG. It is sectional drawing of the photon detector using STJ by the modification of one Embodiment which forms the wiring layer for lower electrodes in the back surface side of a board | substrate. (A) is sectional drawing of the board | substrate which arrayed the photon detector shown in FIG. 9, (b) is the top view.

  Next, an embodiment of a photon detector using an STJ according to the present invention will be described.

  FIG. 5 is a sectional view of the photon detector 31 using the STJ according to the present embodiment.

The photon detector 31 is configured by forming an STJ element 32 on a substrate 33. The STJ element 32 is formed by laminating a lower electrode 34 made of a superconductor, a layer 35 including a tunnel barrier made of an insulator, and an upper electrode 36 made of a superconductor on a substrate 33. Also in this embodiment, Nb is used for the superconductors of the lower electrode 34 and the upper electrode 36, and the thicknesses are 200 nm and 150 nm, respectively. The layer 35 including the tunnel barrier is formed as an Al—AlO _x layer by oxidizing the surface of the Al layer and forming an AlO _x layer constituting the tunnel barrier as an insulator on the surface of the Al layer. . Here, the thickness of the AlO _x layer is set to several nm. Note that an Al layer may be further formed on the AlO _x layer to constitute a trap layer that amplifies secondary electrons generated by the incidence of photons.

  In the photon detector 31 according to the present embodiment, the STJ element 32 is formed by being embedded in a hole 33 a formed in a rectangular shape on the surface of the substrate 33. The surface of the upper electrode 36 constituting the STJ element 32 and the surface of the substrate 33 are formed flush with each other. Further, a part of the lower electrode 34 is formed to be exposed in the hole 33a. On the upper left surface of the substrate 33, a lower electrode wiring layer 38 made of Nb for wiring the lower electrode 34 is formed in a thickness of 650 nm in contact with a part of the lower electrode 34 exposed in the hole 33a. Yes. On the upper right surface of the substrate 33, an upper electrode wiring layer 37 made of Nb for wiring the upper electrode 36 is formed in contact with the surface of the upper electrode 36 to a thickness of 650 nm.

  FIGS. 6A to 6H are cross-sectional views showing a process for manufacturing the photon detector 31 using the STJ according to the present embodiment using the lift-off method. In the figure, the same parts as those in FIG.

In producing the photon detector 31, first, a lift-off photoresist 41 is formed on the substrate 33, and a hole 33a is formed in the substrate 33 by etching using the photoresist 41 as a mask (FIG. 6A). reference). Next, on the substrate 33 and the photoresist 41, an Nb layer 42 to be the lower electrode 34, an Al—AlO _x layer 43 to be the layer 35 including a tunnel barrier, and an Nb layer 44 to be the upper electrode 36 are stacked (same as above). (Refer figure (b)). Next, the photoresist 41 is lifted off to form the lower electrode 34 (see FIG. 5C). Subsequently, a photoresist 45 for processing the upper electrode is formed (see FIG. 4D), and a layer 35 including a tunnel barrier and the upper electrode 36 are formed by etching using the photoresist 45 as a mask (FIG. 5E). reference).

  Next, a photoresist 46 for forming a wiring layer is formed (see (f) in the figure), and a wiring layer 47 is deposited (see (g) in the same figure). Thereafter, the photoresist 46 is lifted off to form the upper electrode wiring layer 37 and the lower electrode wiring layer 38 (see FIG. 11H), and the photon detector 31 is completed.

  Note that in the above manufacturing process, a sputtering method was used for depositing a thin film, and a photolithography technique and reactive ion etching (RIE) were used for processing. Although the case where the photon detector 31 is manufactured by the lift-off method is described here, the photon detector 31 can be similarly manufactured by an etching method without using the lift-off method.

  FIG. 7 is a plan view simulating a photomicrograph of the photon detector 31 produced according to the above process. In the figure, the same or corresponding parts as in FIG.

  As shown in the figure, a part of the lower electrode 34 is exposed in a hole 33 a formed in the substrate 33. An upper electrode wiring layer 37 is formed in contact with the surface of the upper electrode 36, and a lower electrode wiring layer 38 is formed in contact with a part of the lower electrode 34 exposed in the hole 33a. The area of the hole 33a, that is, the area of the STJ element 32 is 50 μm × 50 μm. Further, as a result of observing a step between the surface of the upper electrode 36 and the surface of the substrate 33 with a stylus step meter at the end of the STJ element 32, it was confirmed that the surface was flat. That is, it was confirmed that the surface of the upper electrode 36 and the surface of the substrate 33 are flush with each other.

  In order to evaluate the produced photon detector 31, the current-voltage characteristics of the STJ element 32 were measured at a liquid helium temperature (4.2K).

  FIG. 8 is a graph showing the measurement results. In the graph, the horizontal axis represents voltage, and the vertical axis represents current. As shown in the graph, a strong non-linearity with respect to an increase in voltage appears in the current rising characteristic at the initial stage of voltage application. That is, STJ-specific characteristics appear in the measured current-voltage characteristics, and the effectiveness of the manufacturing method of the photon detector 31 can be confirmed.

  In the photon detector 11 shown in FIGS. 2 and 4 (k) using the conventional STJ, the upper electrode 16 has a height separated from the surface of the substrate 13 by the thickness of the lower electrode 14 and the layer 15 including the tunnel barrier. In order to form the wiring layer 18 in contact with the upper electrode 16, the interlayer insulating film 17 covering the STJ element 12 and the contact hole 19 exposing the upper electrode 16 are required. However, according to the photon detector 31 using the STJ according to the present embodiment, the STJ element 32 is embedded in the hole 33a formed in the surface of the substrate 33 so that the substrate of the upper electrode 36 is formed. The height from the surface can be reduced by more than the thickness of the layer 35 including the lower electrode 34 and the tunnel barrier. Therefore, the wiring layer 37 that contacts the upper electrode 36 can be formed on the substrate surface without forming the interlayer insulating film and the contact hole. For this reason, the conventional manufacturing process for forming the interlayer insulating film 17 and the contact hole 19 and the apparatus for manufacturing the interlayer insulating film become unnecessary, and the manufacturing process and the manufacturing apparatus of the photon detector 31 using STJ are greatly simplified. It becomes. As a result, the manufacturing yield is improved and the manufacturing cost is reduced.

  Further, since the interlayer insulating film is not manufactured, the STJ element 32 is not adversely affected by the conventional formation of the contact hole 19 in the interlayer insulating film 17 and the deposition of the wiring layer 28 on the interlayer insulating film 17. The characteristics as a photon detector do not deteriorate. As a result, the yield of detector characteristics is greatly improved. Further, since the STJ element 32 can be formed without projecting on the substrate 33, another element such as a superconducting element is three-dimensionally stacked on the photon detector 31 composed of the STJ element 32. Thus, various superconducting elements can be easily mounted three-dimensionally. For this reason, it is possible to easily increase the degree of integration of superconducting integrated circuits and the like, and it is possible to easily array the photon detectors 31 using STJ.

  In the photon detector 31 using the STJ according to the present embodiment, the surface of the upper electrode 36 of the STJ element 32 and the surface of the substrate 33 are at the same height. No step is generated between the two. Therefore, various layers to be stacked on the STJ element 32 can be formed flat, and other elements can be more easily formed three-dimensionally on the STJ element 32. The surface of the upper electrode 36 of the STJ element 32 and the surface of the substrate 33 are not the same, and the same effects can be obtained even when they are almost the same height.

  Even if the surface of the upper electrode 36 is formed higher than the surface of the substrate 33 up to the thickness of the upper electrode 36 or lower than the surface of the substrate 33, the interlayer insulating film and the contact hole are formed. Without forming, the wiring layer 37 in contact with the upper electrode 36 can be formed on the substrate surface. For this reason, although flatness falls, the effect similar to this Embodiment is show | played by such a structure.

  In the photon detector 31 using the STJ according to the present embodiment, the wiring layer 38 for wiring the lower electrode 34 and the wiring layer 37 for wiring the upper electrode 36 are both formed on the substrate 33 without forming an interlayer insulating film. It is formed on the surface side. For this reason, the photon detector 31 using STJ suitable for the single-sided mounting of the substrate 33 is provided.

  In the above embodiment, as described above, the case where both the lower electrode wiring layer 38 and the upper electrode wiring layer 37 are formed on the surface side of the substrate 33 has been described. However, the lower electrode wiring layer 38 is described. 9 may be formed on the back surface side of the substrate 33 as shown in the sectional view of FIG. In the figure, the same or corresponding parts as in FIG.

  In the photon detector 51 using the STJ according to this modification, the lower electrode 34a, the layer 35 including the tunnel barrier, and the upper electrode 36 are formed in the same area, and a gap is formed in a hole 33b formed in a rectangular shape in the substrate 33. The STJ element 32a is embedded and formed. A through-hole 52 that communicates with the lower electrode 34 a is formed in a cylindrical shape on the back surface of the substrate 33. The through hole 52 is filled with a conductive material, or the conductive material is plated on the inner periphery of the cylinder, thereby forming a through electrode (not shown). In addition, a wiring substrate 53 is prepared separately from the substrate 33, and a wiring layer 38 a for wiring the lower electrode 34 a is formed on the surface of the wiring substrate 53. The wiring substrate 53 is bonded to the back surface of the substrate 33 so that the end portion of the wiring layer 38 a is in contact with the through electrode formed in the through hole 52. Therefore, the lower electrode wiring layer 38 a formed on the surface of the wiring substrate 53 comes into contact with the lower electrode 34 a through the through hole 52 and is formed on the back surface side of the substrate 33.

  Similar to the photon detector 31 shown in FIG. 5, the wiring layer 37 for wiring the upper electrode 36 is formed on the surface side of the substrate 33 in contact with the surface of the upper electrode 36. In this modification, an absorption layer 54 made of a material and a thickness corresponding to the type of photon to be detected is formed on the surface of the substrate 33 on which the STJ element 32a is formed. Here, the case where the absorption layer 54 is made of an insulating material and is formed in contact with the wiring layer 37 is illustrated, but when the absorption layer 54 is made of a conductive material such as metal, the wiring layer 37 is illustrated. However, the absorption layer 54 may be substituted for the wiring layer 37 and the upper electrode 36 may be wired by the absorption layer 54.

  According to this modification, as described above, the wiring layer 38a for wiring the lower electrode 34a contacts the lower electrode 34a through the through hole 52 formed on the back surface of the substrate 33, and is on the back surface side of the substrate 33. The wiring layer 37 for wiring the upper electrode 36 is formed without forming an interlayer insulating film on the surface side of the substrate 33 in contact with the surface of the upper electrode 36. Accordingly, only the wiring layer 37 for wiring the upper electrode 36 is formed on the surface side of the substrate 33, and the STJ element 32a is covered with the wiring layer 38 for wiring the lower electrode 34 as shown in FIG. Many are exposed on the surface of the substrate 33. For this reason, the photon detector 51 using the STJ having an increased photon detection area and high photon detection sensitivity is provided.

  Further, according to the present modification, the conventional process for removing the interlayer insulating film 17a (see FIG. 4K) immediately above the upper electrode 16 and forming the absorption layer is not required as in the prior art. The absorbing layer 54 having various materials and various thicknesses can be easily formed on the STJ element 32a. Therefore, by forming the absorption layer 54 of various materials and various thicknesses on the STJ element 32a, the types of photons to be detected can be easily changed. Therefore, the photon detector 51 using the STJ that can measure photons in a wide energy band with high detection efficiency is easily provided.

  FIG. 10A is a sectional view of the substrate 33 on which the photon detectors 51 shown in FIG. 9 are arrayed, and FIG. 10B is a plan view thereof. In the figure, the same parts as those in FIG.

  On the back surface of the substrate 33, a wiring substrate 53 in which a lower electrode wiring layer 38a is formed in a predetermined pattern is bonded, and each lower electrode 34a is wired by the wiring layer 38a. Each upper electrode 36 is connected and wired by an upper electrode wiring layer 37.

  By arraying the photon detectors 51 in this way, the photon detection area becomes large and the photon detection efficiency becomes extremely high. Further, since the position of the incident photon can be detected by each STJ element 32a, it can be applied to imaging (imaging).

  In the photon detector 31 shown in FIG. 5, as in the photon detector 51 shown in FIGS. 9 and 10, by forming the absorption layer 54 of various materials and various thicknesses on the substrate 33, Various types of photons to be detected can be easily changed.

In the embodiment and the modification described above, the case where the superconductor forming the lower electrodes 34, 34a and the upper electrode 36 is Nb and the insulator forming the tunnel barrier is made of AlO _x has been described. The material of the conductor or the insulator is not limited to this. For example, Ta, Al, etc. may be used as the superconductor, and MgO, AlN, etc. may be used as the insulator. Even when these materials are used, the same effects as those of the above-described embodiments and modifications can be obtained. The

  Since the photon detectors 31 and 51 using the STJ according to the present embodiment have excellent energy resolution as described above, how the atoms are arranged in the crystal by analyzing the X-ray diffraction result. It can be used for X-ray diffraction (XRD: X-Ray Diffraction) for composition analysis. In other words, when the crystal is irradiated with X-rays, the X-rays are diffracted only in the direction satisfying Bragg's law. Photon detectors 31 and 51 are used to detect a pattern reflecting the crystal structure resulting from this diffraction. be able to.

  It can also be used in an energy dispersive X-ray spectroscopy (Energy Dispersive X-ray Spectroscopy) apparatus. That is, the characteristic X-rays or fluorescent X-rays generated when the object is irradiated with primary rays such as electron beams and X-rays are detected by the photon detectors 31 and 51, and the elements constituting the object from the energy and intensity thereof And the concentration can be examined. Therefore, for example, impurities contained in a thin film can be specified in a semiconductor manufacturing factory, and element screening can be performed. By feeding back the screening result to the semiconductor manufacturing line, the productivity and reliability of semiconductor manufacturing can be improved.

  It can also be used to observe the energy spectrum of light and cosmic rays flying from unknown celestial bodies, and to be used for X-ray photography in the medical field, and can be used in a wide range of fields such as engineering, science, and medicine.

DESCRIPTION OF SYMBOLS 31, 51 ... Photon detector 32, 32a ... STJ (superconducting tunnel junction) element 33 ... Substrate 33a, 33b ... Hole 34, 34a ... Lower electrode 35 ... Layer including tunnel barrier 36 ... Upper electrode 37 ... Upper electrode wiring Layer 38, 38a ... Lower electrode wiring layer 52 ... Through hole 53 ... Wiring substrate 54 ... Absorption layer

Claims (5)

In a photon detector using a superconducting tunnel junction in which a lower electrode made of a superconductor, a tunnel barrier made of an insulator, and an upper electrode made of a superconductor are stacked on a substrate,
A superconducting tunnel junction element composed of the lower electrode, the tunnel barrier, and the upper electrode is formed by being embedded in a hole formed in a recess in the surface of the substrate, and the surface of the upper electrode and the substrate A photon detector using a superconducting tunnel junction, wherein the height difference from the surface is set within a range corresponding to the thickness of the upper electrode .   2. The photon detector using a superconducting tunnel junction according to claim 1, wherein a surface of the upper electrode and a surface of the substrate are formed to be flush or substantially flush.   A part of the lower electrode is exposed in the hole, and a wiring layer for wiring the lower electrode is formed on the surface side of the substrate in contact with a part of the lower electrode exposed in the hole, The superconducting tunnel junction according to claim 1 or 2, wherein a wiring layer for wiring the upper electrode is formed on a surface side of the substrate in contact with the surface of the upper electrode. Photon detector.   A through hole leading from the back surface of the substrate to the lower electrode is formed, and a wiring layer for wiring the lower electrode is formed on the back surface side of the substrate in contact with the lower electrode through the through hole, and the upper electrode 3. A photon detector using a superconducting tunnel junction according to claim 1, wherein a wiring layer for wiring is formed on the surface side of the substrate in contact with the surface of the upper electrode. .   The absorption layer which consists of material and thickness according to the kind of photon made into a detection object is formed in the surface of the said board | substrate with which the said superconducting tunnel junction element was formed. A photon detector using the superconducting tunnel junction according to any one of the above.

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