Method for manufacturing device used for measuring tunnel current, and device

Abstract

The present invention addresses the problem of providing: a method for manufacturing a device which is used for measuring a tunnel current and with which measurement sensitivity can be increased; and a device.　Provided is a method for manufacturing a device used for measuring a tunnel current, wherein said device comprises: a base material; and a first electrode and a second electrode formed on the base material and constituting a pair of measurement electrodes for measuring a tunnel current when a sample has passed.　The manufacturing method comprises: a first metal layer layering step in which a first metal layer, which is a metal layer for forming the first electrode and the second electrode and to which a metal layer for forming the first electrode and the second electrode is connected via a contact breaking point, is layered on a surface of the base material; and an electromigration step in which voltage is applied to the first metal layer so as to cross the contact breaking point, the first metal layer is broken at the contact breaking point utilizing contact breakage achieved by electromigration, and the first electrode and the second electrode having a first nano gap are formed. In the first metal layer that is layered in the first metal layer layering step, a metal layer portion for forming the first electrode includes a first portion connected to the contact breaking point, and a metal layer portion for forming the second electrode includes a second portion connected to the contact breaking point. The first portion and the second portion are each formed in a tapered shape having a width that becomes narrower in a direction toward the contact breaking point. The first portion and the second portion are formed asymmetrically centered on the contact breaking point, and the first portion is formed so as to be wider than the second portion. In the electromigration step, the voltage is applied so that the metal of the first portion moves to the second portion side.

Description

Method for manufacturing a device used to measure tunneling current and the device

[0001] The disclosure in this application relates to a method for fabricating a device and a device used to measure tunneling current.

[0002] A method for identifying the type of a sample, such as a biomolecule, by measuring a tunneling current when the sample passes through nanogap electrodes formed on a substrate is known (see Patent Document 1). Patent Document 1 describes fabricating a nanogap electrode by a mechanically controllable break junction (hereinafter, sometimes referred to as "MCBJ").

[0003] As another example of fabricating a nanogap electrode, Patent Document 2 describes fabricating a nanogap electrode by utilizing contact breakage due to electromigration (electro-migrated break junction, hereinafter sometimes referred to as "EBJ").

[0004] JP 2021-105522 A JP 2021-188910 A

[0005] As described above, the mechanical fracture joining method and the electromigration contact fracture method are known as methods for fabricating nanogap electrodes. However, when measuring a sample using a nanogap electrode (hereinafter, electrodes having a nanogap may be referred to as a "pair of measurement electrodes"), high measurement sensitivity is desirable. Therefore, there is a need for a method for fabricating a pair of measurement electrodes that can achieve high measurement sensitivity.

[0006] The inventors have conducted extensive research to improve the measurement sensitivity of a pair of measurement electrodes fabricated by EBJ, and have newly discovered the following: (1) when metal layers including a contact breakage point for forming a pair of measurement electrodes are laminated on the surface of a substrate, the metal layers are laminated so that they are asymmetrical around the contact breakage point, (2) electromigration is performed so that metal moves from the wider side to the narrower side of the asymmetric metal layer, causing contact breakage, and during electromigration, metal moves from the wider metal layer side to the narrower side, and (3) as a result, compared to when metal layers are laminated so that they are symmetrical around the contact breakage point, the pair of measurement electrodes after fabrication are more likely to be bilaterally symmetrical, thereby increasing measurement sensitivity.

[0007] An object of the disclosure in this application is to provide a method for manufacturing a device used for measuring tunneling current, which can increase measurement sensitivity, and the device.

[0008] The disclosure in this application relates to the following method for manufacturing a device used for measuring tunneling current and the device.

[0009] (1) A method for manufacturing a device used for measuring tunneling current, the device comprising: a substrate; and a first electrode and a second electrode formed on the substrate to form a pair of measurement electrodes for measuring a tunneling current when a sample passes through; the manufacturing method comprising: a first metal layer laminating step of laminating, on a surface of the substrate, a first metal layer for forming the first electrode and the second electrode, the first metal layer being a metal layer to which the metal layers for forming the first electrode and the second electrode are connected via a contact breakage point; and an electromigration step of applying a voltage to the first metal layer across the contact breakage point to break the first metal layer at the contact breakage point by utilizing contact breakage due to electromigration, thereby forming the first electrode and the second electrode having a first nanogap; in the first metal layer laminated in the first metal laminating step, a metal layer portion for forming the first electrode includes a first portion connected to the contact breakage point, and a metal layer portion for forming the second electrode includes a second portion connected to the contact breakage point; A manufacturing method in which the first portion and the second portion are each formed in a tapered shape that narrows in width toward the contact breakage location, the first portion and the second portion are formed asymmetrically around the contact breakage location, and the first portion is formed to be wider than the second portion, and in the electromigration process, a voltage is applied so that metal in the first portion migrates toward the second portion. (2) The manufacturing method according to (1) above, wherein the width of the contact breakage location is 0.05 μm to 10 μm. (3) The manufacturing method according to (1) above, wherein, when the length of the first portion is defined as X and the length of the second portion is defined as Y, X + Y is 0.1 μm to 10 μm. (4) The manufacturing method according to (1) above, wherein, when the taper angle of the first portion is defined as α and the taper angle of the second portion is defined as β, α / β is 1.1 to 3. (5) The manufacturing method according to (1) above, wherein in the first metal layer lamination step, at least two or more first metal layers are laminated, and the electromigration step is performed on each of the at least two or more laminated first metal layers.(6) The manufacturing method according to (1), comprising: a second metal layer laminating step of laminating a second metal layer by a mechanical fracture joining method to form a pair of measurement electrodes having a second nanogap; and a mechanical fracture joining step of fracturing the second metal layer by the mechanical fracture joining method to form a pair of measurement electrodes having a second nanogap. (7) The manufacturing method according to (6), wherein the mechanical fracture joining step is performed by bringing two jigs into contact with the substrate from above and pushing up the substrate between the two jigs from below with a push-up rod, wherein when a location on the substrate pushed up by the push-up rod is defined as a push-up fulcrum, the second metal layer is laminated at a location of the first metal layer and the second metal layer formed on the substrate closest to the push-up fulcrum, and the first metal layer is laminated at a location of the first metal layer and the second metal layer formed on the substrate farthest from the push-up fulcrum. (8) The manufacturing method according to (6) above, wherein the mechanical fracture bonding method implementation step is first performed on the second metal layer, and then the electromigration step is performed on the first metal layer. (9) The manufacturing method according to (7) or (8) above, wherein, when a location where the second metal layer is mechanically fractured is defined as a mechanical fracture location, and an imaginary line passing through the mechanical fracture location of the second metal layer laminated in a location closest to the push-up fulcrum is defined as a third imaginary line, the contact fracture location is not located on the third imaginary line. (10) The manufacturing method according to any one of (1) to (8) above, further including a flow path, wherein the contact fracture location and the mechanical fracture location are located in the flow path. (11) A device used for measuring tunneling current, comprising: a substrate; and a first electrode and a second electrode formed on the substrate, forming a pair of measurement electrodes for measuring a tunneling current when a sample passes through; wherein at least two or more measurement electrodes are formed, and the device comprises: at least one measurement electrode, the first electrode having a first tip width of 2 Å to 15 Å and the second electrode having a second tip width of 2 Å to 15 Å; and at least one measurement electrode, the first electrode having a first tip width of 0.05 μm to 0.2 μm and the second electrode having a second tip width of 0.05 μm to 0.2 μm.

[0010] When a device is fabricated using the manufacturing method disclosed in the present application, the pair of measurement electrodes after fabrication tends to be substantially symmetrical, thereby improving the measurement sensitivity of the device.

[0011] FIG. 1 is a diagram for explaining an outline of the device 1. FIG. 2 is a diagram for explaining an outline of fabrication of a first electrode 31 and a second electrode 32, which form a pair of measurement electrodes 3, by EBJ. FIG. 3 is a schematic diagram for explaining various embodiments in which the first metal layer 30 can be employed. FIG. 4 is a schematic diagram for explaining various embodiments in which the first metal layer 30 can be employed. FIG. 5 is a schematic diagram for explaining various embodiments in which the first metal layer 30 can be employed. FIG. 6 is a diagram for explaining an outline of a manufacturing method for the device 1a according to the second embodiment. FIG. 7 is a diagram for explaining an outline of forming the measurement electrodes by mechanical break joining (MCBJ). FIG. 8 is a diagram for explaining the relationship between the contact break point 33 and the nanogap G when forming the measurement electrodes 3 by EBJ. FIG. 9 is a diagram for explaining an outline of the vicinity of the nanogap G of the device 1a according to the second embodiment. FIG. 10 is a drawing substitute photograph, in which FIG. 10A is an SEM photograph of the vicinity of the tips of the first electrode and the second electrode of the fabricated device 1, and FIG. 10B is an SEM photograph further enlarged near the tips. FIG. 11 is a drawing substitute photograph and is an SEM photograph of the device fabricated in Comparative Example 1. FIG. 12 is a diagram showing an outline of a sample-presuming device. FIG. 13A is a graph showing the results of tunneling current measurement using device 1 fabricated in Example 1. FIG. 13B shows the results of tunneling current measurement using device 1 fabricated in Comparative Example 1. FIG. 14 is a drawing substitute photograph and is an enlarged photograph of device 1 fabricated in Example 2 and the vicinity of nanogap G. FIG. 15A is a diagram showing the outline of measuring a sample using device 1 fabricated in Example 2, FIG. 15B is a diagram showing the results of tunneling current measurement, and FIG. 15C is a histogram of conductance obtained by dividing the current value of FIG. 15B by voltage.

[0012] A method for manufacturing a device used for measuring tunneling current (hereinafter, sometimes simply referred to as "manufacturing method") and the device will be described in detail below with reference to the drawings.

[0013] In this specification, components having the same functions are denoted by the same or similar reference numerals, and repeated descriptions of the components denoted by the same or similar reference numerals may be omitted.

[0014] In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. Numerical values, numerical ranges, and qualitative expressions (e.g., expressions such as "same" and "approximately") should be interpreted as indicating numerical values, numerical ranges, and properties that include errors generally accepted in the technical field.

[0015] Furthermore, for ease of understanding, the position, size, range, etc. of each component shown in the drawings may not represent the actual position, size, range, etc. Therefore, the disclosure in this application is not necessarily limited to the position, size, range, etc. disclosed in the drawings.

[0016] (First Embodiment of Device Manufacturing Method) A method for manufacturing a device 1 according to a first embodiment (hereinafter, may be simply referred to as a "manufacturing method") will be described with reference to FIGS. 1 to 5. FIG. 1 is a diagram for explaining an outline of the device 1. FIG. 2 is a diagram for explaining an outline of fabrication of a first electrode 31 and a second electrode 32 that form a pair of measuring electrodes 3 by EBJ. FIGS. 3 to 5 are schematic diagrams for explaining various embodiments in which the first metal layer 30 can be employed.

[0017] As shown in FIG. 1 , a device 1 manufactured by the manufacturing method disclosed herein includes at least a substrate 2, a first electrode 31, and a second electrode 32. The first electrode 31 and the second electrode 32 are formed on the substrate 2 and form a pair of measurement electrodes 3 for measuring a tunneling current when a sample passes through them. In the example shown in FIG. 1 , a flow path 4 is optionally formed on the substrate 2. The flow path 4 shown in FIG. 1 includes a measurement flow path 41 in which the pair of measurement electrodes 3 are arranged and for measuring a tunneling current when a sample passes through a gap (nano-gap) G between the electrodes, a sample input flow path 42 for inputting a solution containing the sample, a first tapered flow path 43 connecting the measurement flow path 41 and the sample input flow path 42, a sample recovery flow path 44 for recovering the sample, and a second tapered flow path 45 connecting the measurement flow path 41 and the sample recovery flow path 44. The first electrode 31 and the second electrode 32 are stacked on the substrate 2, and a nano-gap G is formed between the first electrode 31 and the second electrode 32. In other words, since the first electrode 31 and the second electrode 32 have a certain thickness, they can be said to form a bank on the substrate 2. Therefore, since the portions on the substrate 2 other than the first electrode 31 and the second electrode 32 can also function as a flow channel, the formation of the flow channel 4 in the device 1 is not essential but is an optional additional feature.

[0018] There are no particular limitations on the material of the substrate 2 as long as it is a material commonly used in the field of semiconductor manufacturing technology, such as Si, SiOx, SiNx, Ge, Se, Te, GaAs, GaP, GaN, InSb, and InP.

[0019] There are no particular limitations on the material for forming the first electrode 31 and the second electrode 32 as long as it allows measurement of tunneling current. Examples include gold, platinum, silver, palladium, tungsten, and alloys of these metals.

[0020] The manufacturing method according to the first embodiment includes a first metal layer lamination step and an electromigration step. In the first metal layer lamination step, as shown in FIG. 2A , a first metal layer 30 is laminated on the surface of the base material 2. The first metal layer 30 is a metal layer for forming a first electrode 31 and a second electrode 32, and the metal layers for forming the first electrode 31 and the second electrode 32 are connected via a contact breakage point 33. The first metal layer 30 may be deposited on the substrate 2 by a known method such as electron beam lithography.

[0021] In the first metal layer 30, the metal layer portion for forming the first electrode 31 includes a first portion 31a connected to the contact breakage point 33, and the metal layer portion for forming the second electrode 32 includes a second portion 32a connected to the contact breakage point 33. The first portion 31a and the second portion 32a are each formed in a tapered shape that narrows toward the contact breakage point 33. The first portion 31a and the second portion 32a are also formed asymmetrically with respect to the contact breakage point 33. In the example shown in FIG. 2A , the first portion 31a and the second portion 32a are formed in a substantially equilateral triangular shape and are connected at the vertex. In the example shown in FIG. 2A , the width w1 of the first portion 32a is formed to be wider than the width w2 of the second portion 32a.

[0022] In this specification, "width (w1)" refers to the shortest imaginary line that passes through a point (Lp) at a distance (L1) from the contact breaking point 33 when the device 1 is viewed vertically and reaches two sides of the first portion 31a from the apex angle. Similarly, "width (w2)" refers to the shortest imaginary line that passes through a point (Lp) at a distance (L2) from the contact breaking point 33 and reaches two sides of the second portion 32a from the apex angle. L1 and L2 have the same length. In the example shown in FIG. 2A, L1 and L2 are perpendicular lines extending from the apex angle of an isosceles triangle to the base. In this specification, the end of the portion of the first metal layer 30 that forms the first electrode 31 (first electrode 31) opposite the contact breakage point 33 is defined as the "first end 31b," and the end of the portion of the first metal layer 30 that forms the second electrode 32 (second electrode 32) opposite the contact breakage point 33 is defined as the "second end 32b." In the fabricated device 1, the portions where the first electrode 31 and the second electrode 32 face each other across the nanogap G are defined as the first tip 31c and the second tip 32c, respectively. The widths of the first tip 31c and the second tip 32c (in the same direction as w1 and w2 in FIG. 2) are defined as the "width of the first tip 31c" and the "width of the second tip 32c," respectively.

[0023] In the electromigration (EBJ) process, a voltage is applied to the first metal layer 30 across the contact rupture point 33, and the first metal layer 30 is broken at the contact rupture point 33 by the EBJ. As shown in FIG. 2B , the first electrode 31 and the second electrode 32 having the first nanogap G are formed. In the EBJ process, a voltage is applied so that the metal around the first portion 31a migrates toward the second portion 32a. Therefore, the width w1 of the first portion 31a is narrowed by performing the EBJ process, but the width w2 of the second portion 32a is widened by the deposition of the migrated metal. This allows the difference between the width w1 of the first portion 31a and the width w2 of the second portion 32a to be reduced.

[0024] In conventional device fabrication using EBJ, there was no knowledge that metal migration occurs during the EBJ process. Therefore, before performing the EBJ process, the first metal layer 30 was stacked on the substrate 2 so as to be symmetrical about the contact breakage point 33. However, the inventors, through extensive research, discovered that stacking the first metal layer 30 so as to be symmetrical results in an asymmetrical shape of the portion where the first electrode 31 and the second electrode 32 of the device fabricated through the EBJ process, resulting in a decrease in the accuracy of measurement results. The manufacturing method disclosed in this application is characterized by taking into account the amount of metal migration during the EBJ process and increasing the amount of metal in the first portion 31a from which the metal flows out compared to the second portion 32a to which the metal migrates, in order to make the portion where the first electrode 31 and the second electrode 32 of the fabricated device 1 as symmetrical as possible. Furthermore, when fabricating a measurement electrode using MCBJ, metal migration does not occur. Therefore, stacking the first metal layer 30 so as to be asymmetrical is a unique feature of forming a measurement electrode using EBJ.

[0025] The location where EBJ breaks is where an electric field concentrates when a voltage is applied. Therefore, it is desirable to design contact breakage location 33 so that the electric field concentrates. In the example shown in FIG. 2A , contact breakage location 33 is the location where tapered first portion 31 and tapered second portion 32 intersect. As is clear from FIG. 2A , the angle at which the two tapers intersect may be less than 180 degrees, and may be 170 degrees or less, 160 degrees or less, 150 degrees or less, 140 degrees or less, or 130 degrees or less.

[0026] The voltage applied in the EBJ process may be adjusted appropriately depending on the size of the first metal layer 30, etc. Although not limited thereto, a voltage of 1 V to 100 V, preferably 1 to 30 V, may be applied. The voltage may be applied for approximately 1 minute to 10 minutes. In the example shown in FIG. 2A, the voltage may be applied so that the wider first portion 31a is ground (0 V) and the second portion 32a is biased (+V). In other words, the side on which the metal transferred by the EBJ process is deposited may be biased.

[0027] [Various configuration examples in which the first metal layer 30 can be employed] As described above, the first metal layer 30 is not particularly limited in shape, arrangement, etc., as long as it can be broken at the contact breaking point 33 by EBJ and the first electrode 31 and the second electrode 32 having the first nanogap G can be formed while the metal of the first portion 31 a is deposited on the second portion 32 a. Various embodiments in which the first metal layer 30 can be employed will be described in more detail below, although they are not limited thereto.

[0028] (Regarding the Shape of the First Portion 31a and the Second Portion 32a) In the example shown in FIG. 2A , the first portion 31a and the second portion 32a are substantially isosceles triangles. Alternatively, they may have shapes as shown in FIGS. 3A to 3C . In the example shown in FIG. 3A , the first portion 31a is formed in a curved shape that bulges outward from an isosceles triangle. Although not shown, if w1 > w2, the second portion 32a may be formed in a curved shape that bulges outward from an isosceles triangle. In the example shown in FIG. 3B , the second portion 32a is formed in a curved shape that concaves inward from an isosceles triangle. Although not shown, if w1 > w2, the first portion 31a may be formed in a curved shape that concaves inward from an isosceles triangle. In the example shown in FIG. 3C , the first portion 31a is formed in a non-isosceles triangle. Although not shown, if w1 > w2, the second portion 32a may be formed in a non-isosceles triangle. In the example shown in Figures 3A to 3C, the positions of w1 and w2 are equidistant from the contact breaking point 33, as in Figure 2A. Furthermore, in the example shown in Figure 3C, L1 and L2 are set on a first virtual line La that is parallel to the longitudinal direction of the first electrode 31 and the second electrode 32 and passes through the contact breaking point 33. Note that Figures 3A to 3C are merely examples and are not limited to the examples shown in Figures 3A to 3C. For example, both the first portion 31a and the second portion 32a may be curved to bulge outward from an isosceles triangle, curved to dent inward from an isosceles triangle, or non-isosceles triangular. Furthermore, the first portion 31a and the second portion 32a may be a combination selected from curved to bulge outward from an isosceles triangle, curved to dent inward from an isosceles triangle, and non-isosceles triangular. As described above, it is sufficient that the widths of the first portion 31 a and the second portion 32 a narrow toward the contact breaking point 33. Therefore, when the term "tapered" is used in this specification, the pieces forming the taper are not limited to "straight lines," but are a concept that includes "curved lines" and "combinations of curved lines and straight lines."

[0029] (Regarding the Size of the First Portion 31a and the Second Portion 32a) The sizes of the first portion 31a and the second portion 32a will be described with reference to FIG. 4 . First, the width (w) of the contact breakage point 33 will be described with reference to FIG. 4A . The width (w) of the contact breakage point 33 is not particularly limited as long as it can be broken by EBJ, but it may be, for example, 0.02 μm to 10 μm. If the width (w) of the contact breakage point 33 is 10 μm or greater, the electric field will not concentrate, increasing the possibility of breakage occurring at locations other than the contact breakage point 33, potentially reducing product yield. Furthermore, if the width (w) of the contact breakage point 33 is 0.02 μm or less, the first metal layer 30 will be more likely to crack due to physical impact or during fabrication, potentially reducing product yield. The width w is the length connecting the two points where the sides of the first portion 31a and the second portion 32a intersect and change angle. When a pair of measuring electrodes is fabricated using an MCBJ, a metal layer is laminated on a substrate so that the width is 0.05 μm to 0.2 μm, although this is not particularly limited.

[0030] Next, the relationship between the lengths of the first portion 31a and the second portion 32a will be described with reference to FIG. 4B . When the length of the first portion 31a is defined as X and the length of the second portion 32a as Y, X+Y may be 0.05 μm to 10 μm. If X+Y is shorter than 0.05 μm, the first metal layer 30 is more likely to crack due to physical impact or during fabrication, potentially reducing product yield. If X+Y is longer than 10 μm, the electric field is less likely to concentrate, increasing the likelihood of breakage occurring at locations other than the contact breakage point 33, potentially reducing product yield. In this specification, the length X of the first portion 31a refers to the length from the contact breakage point 33 to the end of the first portion 31a on the first end 31b side. The end of the first portion 31a refers to the second imaginary line Lb connecting the end points of the tapered portions of the first portion 31a. The length X of the first portion 31a means the length of the shortest line connecting the contact breaking point 33 and any point on the second virtual line Lb. In the example shown in Fig. 2B, the length X of the first portion 31a is the length of the perpendicular line from the contact breaking point 33, which is the apex angle of an isosceles triangle, to the base. The length Y of the second portion 32a may be defined in the same way as X.

[0031] Next, the taper angles of the first portion 31a and the second portion 32a will be described with reference to FIG. 4C . When the taper angle of the first portion 31a is defined as α and the taper angle of the second portion 32a as β, α / β may be 1.1 to 3. If α / β is less than 1.1, it becomes difficult to form symmetrical shapes between the first portion 31a of the first electrode 31 and the second portion 32a of the second electrode 32. Furthermore, if α / β is greater than 3, it becomes difficult to adjust the spacing of the nanogap G. Note that, when the first portion 31a and the second portion 32a include curves as shown in FIGS. 2A and 2B , the angle formed between the contact breakage point 33 and w1 may be defined as α, and the angle formed between the contact breakage point 33 and w2 may be defined as β.

[0032] (Example of Device 1 Including Flow Channel) When a flow channel is formed in the device 1, it may be produced by a known method, for example, as described in JP-A-2022-134830 etc. For example, the following method may be mentioned.

[0033] (1) An insulating layer is formed on the substrate 2 using an insulating material such as polyimide. (2) A metal layer for forming the first metal layer 30 is deposited on the insulating layer using electron beam lithography (EB lithography). (3) A deposition layer of SiO2 or the like is formed by chemical vapor deposition. A resist layer is laminated on the deposition tank by spin coating. (4) A pattern of the flow path 4, including the measurement flow path 41, is formed by electron beam lithography so as to overlap the first metal layer 30. (5) The flow path 4 is formed by dry etching. Then, the metal layer is cut at the contact breaking point 33 of the first metal layer 30 using EBJ, thereby forming a pair of measurement electrodes 3, the first electrode 31 and the second electrode 32. Note that the measurement flow path 41 may be etched down to below the measurement electrode 3, or the flow path below the measurement electrode 3 may be omitted. (6) If necessary, a cover member having holes formed therein for introducing sample liquid or inserting electrophoresis electrodes is attached.

[0034] The insulating layer 2b may be made of any material commonly used in the field of semiconductor manufacturing technology, including, for example, insulating polymers such as polyimide, polypropylene, polyvinyl chloride, polystyrene, high density polyethylene (HDPE), polyacetal (POM), and polyepoxy; insulating oxide semiconductor metals such as SiO2 and aluminum oxide; and the like.

[0035] Materials for forming the deposition layer include insulating polymers such as polyimide, polypropylene, polyvinyl chloride, polystyrene, high density polyethylene (HDPE), polyacetal (POM), and polyepoxy; insulating oxide semiconductor metals such as SiO2 and aluminum oxide; and the like.

[0036] There are no particular limitations on the photoresist used in electron beam lithography and the reagents used for development and etching, etc., as long as they are materials commonly used in the field of microfabrication technology. There are also no particular limitations on the equipment used in spin coaters and etching, etc., as long as they are materials commonly used in the field of microfabrication technology.

[0037] (Number of Measurement Electrodes 3) The number of measurement electrodes 3 is not limited to one, and a plurality (two or more locations) of measurement electrodes 3 may be formed on the substrate 2, such as two, three, four, five, six, seven, eight, nine, ten, or more. When two or more measurement electrodes 3 are formed, at least two first metal layers 30 may be stacked in the first metal layer stacking step, and the electromigration step may be performed on each of the two or more stacked first metal layers 30. When two or more measurement electrodes 3 are formed and a flow path 4 is formed, two or more measurement electrodes 3 may be formed in a single measurement flow path 41, or two or more measurement flow paths 41 may be formed and one measurement electrode 3 may be formed in one measurement flow path 41.

[0038] (Regarding the Shapes of the First Electrode 31 and the Second Electrode 32) In the example shown in FIGS. 2 to 4 , the width of the first electrode 31 is the same except for the first portion 31 a. In other words, in the first electrode 31, only the first portion 31 a has a changed width. Similarly, in the second electrode 32, only the second portion 32 a has a changed width. Alternatively, as shown in FIG. 5 , the first electrode 31 may have a first step portion 31 d between the portion on the first end 31 b side and the first portion 31 a, the first step portion 31 d being narrower than the portion on the first end 31 b side and wider than the first portion 31 a. Similarly, the second electrode 32 may have a second step portion 32 d between the portion on the second end 32 b side and the second portion 32 a, the second step portion 32 d being narrower than the portion on the second end 32 b side and wider than the second portion 32 a. 5, the number of first step portion 31d and second step portion 32d is one each, but a plurality of such portions may be formed, such as two, three, or four. Also, in the example shown in FIG. 5, the number of step portions of first electrode 31 and second electrode 32 is the same, but the numbers may be different. Forming step portions has the effect of mitigating heat generation caused by electrical resistance.

[0039] The various configuration examples described above in [Various configuration examples in which the first metal layer 30 can be employed] are typical configuration examples, and other configuration examples may be employed as long as they are within the scope of the technical concept disclosed in this specification. In addition, the exemplified configuration examples may be combined.

[0040] (Second Embodiment of Device Manufacturing Method) A manufacturing method for a device 1a according to a second embodiment will be described with reference to FIGS. 6 to 9 . FIG. 6 is a diagram for explaining an outline of a manufacturing method for a device 1a according to the second embodiment. FIG. 7 is a diagram for explaining an outline of forming a measurement electrode by mechanical break joining (MCBJ). FIG. 8 is a diagram for explaining the relationship between a contact break point 33 and the nanogap G when forming a measurement electrode 3 by EBJ. FIG. 9 is a diagram for explaining an outline of the vicinity of the nanogap G of a device 1a according to the second embodiment. The manufacturing method for a device 1a according to the second embodiment combines the formation of the measurement electrode 3 by EBJ and the formation of the measurement electrode 3a by mechanical break joining (MCBJ) to form one or more measurement electrodes 3 and one or more measurement electrodes 3a on a substrate 2. In the second embodiment, the formation of the measurement electrode 3 by EBJ is the same as in the first embodiment. Therefore, the device manufacturing method according to the second embodiment will be described mainly with reference to differences from the first embodiment, and repeated explanations of matters already explained in the first embodiment will be omitted. Therefore, it goes without saying that the matters already explained in the first embodiment can be adopted even if they are not explicitly explained in the device manufacturing method according to the second embodiment.

[0041] The manufacturing method according to the second embodiment includes a second metal layer 30a lamination process in which a second metal layer 30a is laminated by mechanical break joining (MCBJ) to form a pair of measurement electrodes 3a having a second nanogap G', and a mechanical break joining process implementation process in which the second metal layer 30a is broken by the mechanical break joining method to form a pair of measurement electrodes 3a having a second nanogap G'.

[0042] As shown in Figure 7, MCBJ is a method of forming a measurement electrode having a second nanogap G' by repeating the following steps: a) placing a jig 50 above a substrate 2 on which a second metal layer 30a has been laminated, and pushing up the substrate 2 between two jigs 50 from below with a push-up rod 51 (hereinafter, the location on the substrate 2 pushed up by the push-up rod 51 may be referred to as the "push-up fulcrum"); and b) eliminating the bending of the substrate by moving the push-up rod 51 downward.

[0043] The method of forming a measurement electrode using MCBJ is described, for example, in JP-T-2019-525766, Tsutsui, K., Shoji, M., Taniguchi, T. Kawai, Nano Lett., 345 (2008), and M. Tsutsui, M. Taniguchi, T. Kawai, Appl. Phys. Lett. 93, 163115 (2008) (hereinafter referred to as "Non-Patent Document 1"). The mechanical fracture joining method may be performed using the method described in these prior documents. The matters described in JP-T-2019-525766 and Non-Patent Document 1 are incorporated herein by reference.

[0044] When forming one or more measurement electrodes 3 and one or more measurement electrodes 3a on a substrate 2, MCBJ can be used to form them more efficiently than EBJ. As shown in FIGS. 6 and 7 , a push-up rod 51 is placed between two jigs 50. In this case, when the substrate 2 is pushed up and bent by the push-up rod 51, the substrate 2 is more likely to bend the closer it is to the push-up fulcrum. In other words, it is easier to form measurement electrodes 3a by MCBJ on metal layers closer to the push-up fulcrum, but it is more difficult to form measurement electrodes 3a on metal layers farther from the push-up fulcrum. Therefore, in the manufacturing method according to the second embodiment, of the first metal layer 30 and the second metal layer 30a formed on the substrate 2, the second metal layer 30a is stacked in a location closest to the push-up fulcrum, and the first metal layer 30 is stacked in a location farthest from the push-up fulcrum.

[0045] 6 shows an example in which, of the five metal layers, three metal layers closest to the thrust-up fulcrum are stacked as second metal layers 30a, and the two outer metal layers furthest from the thrust-up fulcrum are stacked as first metal layers 30, but this example is not limiting. As long as the second metal layer 30a is stacked as the metal layer closest to the thrust-up fulcrum and the metal layer furthest from the thrust-up fulcrum is stacked as the first metal layer 30, the other metal layers may be either the first metal layer 30 or the second metal layer 30a.

[0046] As described above, when forming the measurement electrode by EBJ, the metal from the first portion 31a migrates to the second portion 32a. Therefore, the first metal layer 30 is formed asymmetrically about the contact breakage point 33. On the other hand, when forming the measurement electrode by MCBJ, the metal does not migrate from the first portion to the second portion. Therefore, the second metal layer 30a may be formed symmetrically about the mechanical breakage point 33a, which is broken by MCBJ. The width of the mechanical breakage point 33a of the second metal layer 30a may be designed to be approximately 0.05 μm to 0.2 μm.

[0047] Next, the positional relationship between the contact breakage point 33 and the first nanogap G of the measurement electrode 3 formed by EBJ will be described with reference to Figure 8. As described above, in EBJ, the metal of the first portion 31a moves to the second portion 32a. Therefore, in EBJ, the center of the first nanogap G is not formed to be located at the same position as the contact breakage point 33, but as the metal moves, the center of the first nanogap G moves from the contact breakage point 33 toward the first end 31b of the first electrode 31.

[0048] Assume that the same sample passes through multiple measurement electrodes 3, 3a formed on the substrate 2. In this case, variations in the positions of the first nanogap G and the second nanogap G' in the sample flow direction may affect measurement accuracy. Therefore, when stacking the first metal layer 30 and the second metal layer 30a, it is preferable to adjust the positions of the contact breakage point 33 and the mechanical breakage point 33a so that the positions of the first nanogap G and the second nanogap G' in the fabricated device 1a are approximately linear.

[0049] The positional relationship between the contact breakage point 33 and the mechanical breakage point 33a will be described in more detail with reference to Figure 6. If a virtual line passing through the mechanical breakage point 33a of the second metal layer 30a stacked closest to the thrust fulcrum is defined as a third virtual line Lc, the contact breakage point 33 should not be positioned on the third virtual line Lc. In the example shown in Figure 6, three second metal layers 30a are stacked. Therefore, the third virtual line Lc may be defined as a line connecting the three mechanical breakage points 33a.

[0050] There may also be a case where one second metal layer 30a and two or more first metal layers 30 are laminated on the substrate 2. In that case, for example, an imaginary line that is parallel to a side of the substrate 2 (the upper or lower side in the example shown in FIG. 6 ) and passes through the mechanical breakage point 33a may be defined as the third imaginary line Lc. Alternatively, as shown in FIG. 6 , when a measurement flow path 41 is formed, an imaginary line that is parallel to the longitudinal direction of the measurement flow path 41 and passes through the mechanical breakage point 33a may be defined as the third imaginary line Lc.

[0051] 8, the first nanogap G is shifted from the contact breakage point 33 to the first electrode 31 side. Therefore, as shown in FIG. 6, the contact breakage point 33 of the first metal layer 30 may be positioned closer to the second end 32b than the third virtual line Lc.

[0052] Considering the measurement accuracy of the sample, the first nanogap G and the second nanogap G' after fabrication of the device 1a preferably fall within a predetermined range. While not limited to this, the distance between the first nanogap G and the second nanogap G' is preferably 0.1 nm or more and 1 nm or less. The distance between the first nanogap G and the second nanogap G' refers to the distance between the tip of the first electrode 31 and the tip of the second electrode 32. Furthermore, when the average width of the nanogaps of two or more measurement electrodes formed on the substrate 2 is taken as a reference value, the distance between each nanogap G is preferably within ±20%, ±19%, ±18%, ±17%, ±16%, ±15%, ±14%, ±13%, ±12%, ±11%, or ±10% of the reference value.

[0053] The distance of the first nanogap G formed by EBJ can be adjusted by the applied voltage, application time, etc. The distance of the second nanogap G' formed by MCBJ can be adjusted by the speed of the thrust rod, etc.

[0054] Next, referring to FIG. 9 , we will explain the difference between the measurement electrode 3 formed by EBJ and the measurement electrode 3a formed by MCBJ. In EBJ, metal migrates from the first portion 31a to the second portion 32a at the atomic level. Therefore, as shown in the examples described below, in the measurement electrode 3 formed by EBJ, the width of the first tip 31c of the first portion 31a (the distance between the "→" and "←" in FIG. 9 ) is a distance equivalent to several metal atoms (approximately 1 to 7 atoms), for example, approximately 2 Å to 15 Å. On the other hand, in the measurement electrode 3a formed by MCBJ, the laminated second metal layer 30a is mechanically determined, so metal atoms do not migrate from the first portion 31a' to the second portion 32a'. Therefore, no atomic-level protrusions are formed due to metal migration, and the width of first tip 31c' of first portion 31a' of measuring electrode 3' and the width of second tip 32c' of second portion 32a' (the distance between "→" and "←" in FIG. 9) are the same as the width (0.05 μm to 0.2 μm) of mechanically broken portion 33a of second metal layer 30a. In other words, the measuring electrode 3 formed by EBJ and the measuring electrode 3a formed by MCBJ are characterized by different widths of the portions where the pair of electrodes face each other.

[0055] Additionally, as described above, in the measurement electrode 3 formed by EBJ, the first metal layer breaks as the metal moves at the contact rupture location where the electric field is concentrated. Therefore, the first tip 31c and the second tip 32c can be said to be formed so that the pointed shapes on the order of Å face each other. Furthermore, because EBJ causes contact rupture at the location where the electric field is concentrated, only one location where the pointed shapes on the order of Å face each other is formed in the measurement electrode 3. On the other hand, the measurement electrode 3a formed by MCBJ does not have the characteristics of EBJ formation. In other words, it can be said that the electrode does not have a location where the pointed shapes on the order of Å face each other.

[0056] The following examples are provided to specifically explain the disclosure of the present application, but these examples are provided for reference of specific embodiments and are not intended to limit or restrict the scope of the disclosure of the present application.

[0057] [Device Fabrication by EBJ] Example 1 Device 1 was fabricated according to the following procedure. i: First Metal Layer Lamination Process (1) An insulating layer 2 was formed on a silicon substrate 2 using polyimide. (2) A first metal layer for forming a measurement electrode 3 on the insulating layer was deposited on the insulating layer using electron beam lithography and lift-off technology. ZEP520A was used as the resist, and gold was used as the material for the metal layer for forming the measurement electrode 3. (3) A deposition layer of SiO2 was formed by chemical vapor deposition. A resist layer was laminated on the deposition tank by spin coating. ZEP520A was used as the resist. (4) A pattern of a flow channel 4 including a measurement flow channel 41 was formed by electron beam lithography so as to overlap the metal layer for forming the measurement electrode 3. (5) The flow channel 4 was formed by dry etching. The first metal layer in Example 1 was designed as follows. The symbols are the same as those in Figure 4. Shape of the first and second portions: FIG. 5 α: 80 degrees, β: 45 degrees X: 1.25 μm, Y: 2.25 μm Lb: 2 μm w: 0.04 μm

[0058] ii: EBJ step Next, the EBJ step was carried out in the following manner: a: A DC voltage was applied at a starting voltage V ０ (1 V) by a delta voltage (50 mV) per minute. When the electrical conductivity (calculated from the circuit current) at the contact determination point 33 decreased by 10% or more, it was returned to the starting voltage. b: When the electrical conductivity became 20 times the quantum conductance or less, the DC current was increased by a delta voltage (20 mV) per minute from the starting voltage. When the electrical conductivity (calculated from the circuit current) at the contact determination point 33 decreased by 20% or more, it was returned to the starting voltage. c: If the electrical conductivity did not decrease even after exceeding 10 times the starting voltage in b, the starting voltage was returned, and the delta voltage per minute was increased by 20 mV to the previous b as a new delta voltage per minute, and b was performed again.

[0059] iii: Device Finishing A PDMS cover member with a sample insertion hole and an insertion hole for the electrophoresis electrodes was fabricated by electron beam lithography. The substrate 2 with the flow path 4 formed therein and the cover member were treated with ozone plasma and bonded together. Ag / AgCl was used for the electrophoresis electrodes, and they were inserted through the holes formed in the cover member.

[0060] Fig. 10A shows an SEM photograph of the vicinity of the tips of the first electrode and the second electrode of the fabricated device 1. Fig. 10B shows an enlarged SEM photograph of the vicinity of the tips. The distance of the first nanogap G of the fabricated device 1 was approximately 1.0 nm.

[0061] Comparative Example 1 A device was fabricated using the same procedure as in Example 1, except that a first metal layer in which the first and second portions were symmetrical (α and β in Example 1 were 35 degrees) was used instead of the first metal layer in which the first and second portions were asymmetrical in Example 1. Fig. 11 shows an SEM photograph of the device fabricated in Comparative Example 1. Note that, for experimental convenience, the arrangement of the first and second electrodes in the device of Comparative Example 1 shown in Fig. 11 is reversed left to right from the arrangement of the first and second electrodes in Example 1.

[0062] 10 and 11, the first portion 31a and the second portion 32a of the device fabricated in Example 1 were closer to symmetry than the first portion 31a and the second portion 32a of the device fabricated in Comparative Example 1. Therefore, it was confirmed that it is preferable to stack the first metal layer so as to be asymmetrical before performing the EBJ process.

[0063] [Sample Measurement] Next, using the devices prepared in Example 1 and Comparative Example 1, sample measurements were performed using the following procedure. <Preparation of Sample Measurement Apparatus> A schematic diagram of the sample measurement apparatus is shown in FIG. 12 . A battery was used as the electrophoresis power supply 6, and it was connected via leads to the first electrophoresis electrode 61 and the second electrophoresis electrode 62 of the prepared device 1. For the tunneling current detection unit 7, a method was used in which the current / voltage was amplified as an ammeter to measure the minute current value as a voltage to obtain the current value, and a National Instrument digital oscilloscope, which is an A / D converter, was used as the voltmeter. Furthermore, the current amplifier was improved in accuracy by incorporating a feedback resistor into a commercially available current amplifier. Furthermore, data from pre-measured samples was stored in the computer's memory. Furthermore, a program to enable the computer to function to analyze the samples was created and stored in the memory. In FIG. 12 , reference numeral 8 denotes the tunneling current measurement power supply, reference numeral 9 denotes an analysis unit, reference numeral 10 denotes a display unit, reference numeral 11 denotes a program memory, and reference numeral 12 denotes a control unit.

[0064] <Tunneling Current Measurement> (1) Deoxyguanosine monophosphate (dGMP; manufactured by Sigma-Aldrich) with a concentration of 1 μM was used as the sample. The sample was introduced into the sample introduction channel 42, and a solvent was introduced into the sample recovery channel 44. DC voltages of 600 mV and −600 mV were applied to the electrophoresis electrodes 61 and 62, respectively. A DC voltage of 100 mV was applied to the first electrode 31 and the second electrode 32. (2) During electrophoresis, the change in tunneling current was measured over time as the sample passed through the first nanogap between the first electrode 31 and the second electrode 32.

[0065] FIG. 13A shows the results of tunneling current measurements using Device 1 fabricated in Example 1. FIG. 13B shows the results of tunneling current measurements using Device 1 fabricated in Comparative Example 1. As is clear from FIGS. 13A and 13B , even though the samples and measurement conditions were the same, the device fabricated in Comparative Example 1 exhibited more double signals than the device fabricated in Example 1 ( FIG. 13B ). Note that a double signal refers to a signal that appears as if two peaks were present in a region that should be measured as a single peak, as shown in the elliptical area in FIG. 13B . From these results, we confirmed that when fabricating measurement electrode 3 using EBJ, the measurement sensitivity of device 1 after fabrication can be improved by making the first metal layer asymmetric before performing the EBJ process and applying a voltage such that the metal in first portion 31 moves to second portion 32, taking into account the metal migration caused by EBJ.

[0066] [Fabrication of Devices by MCBJ and EBJ] Example 2 i: Step of Laminating First and Second Metal Layers When performing electron beam lithography and lift-off technology in "i: Step of Laminating First Metal Layer" described in Example 1, one second metal layer was laminated on substrate 2, and first metal layers were laminated on both sides of the second metal layer. The second metal layers were laminated symmetrically around the mechanical fracture point.

[0067] ii: MCBJ process: A measurement electrode having a second nanogap G' was fabricated from the second metal layer by bending the substrate 2 using a known MCBJ. Note that the push-up fulcrum was positioned directly below the second metal layer, so the two first metal layers stacked far from the push-up fulcrum were not cut by the MCBJ.

[0068] iii: EBJ Step Using the same procedure as in "ii: EBJ step" in Example 1 above, a measuring electrode having a first nanogap G was fabricated from the first metal layer that was not cut by MCBJ.

[0069] Figure 14 shows a magnified photograph of the fabricated device 1 and the vicinity of the nanogap G. In Figure 14, #1 and #3 are measurement electrodes 3 fabricated by EBJ, and #2 is measurement electrode 3' fabricated by MCBJ. The distance of the first nanogap G of #1 was 0.645 nm, the distance of the second nanogap G' of #2 was 0.742 nm, and the distance of the first nanogap G of #3 was 0.876 nm. The width of the first tip of #1 was 6.45 Å, the width of the second tip was 7.42 Å, the width of the first tip of #2 was 0.1 μm, the width of the second tip was 0.1 μm, and the width of the first tip of #3 was 8.11 Å, the width of the second tip was 7.42 Å. Note that in each of the photographs on the right side of Figure 14, measurement electrodes were formed along the dotted lines corresponding to the numbers #1, #2, and #3.

[0070] [Measurement of Samples Using the Device Prepared in Example 2] <Preparation of Sample Measurement Apparatus> A sample measurement apparatus was prepared using the device prepared in Example 2 instead of the device prepared in Example 1, following the same procedure as in <Preparation of Sample Measurement Apparatus> in Example 1. Note that the device prepared in Example 2 has three measurement electrodes, but for sample measurement, measurement electrode #1 prepared by EBJ and measurement electrode #2 prepared by MCBJ were used. In addition, as shown in Fig. 15A, a DC voltage of 100 mV was applied to each of measurement electrodes #1 and #2.

[0071] <Tunneling Current Measurement> Deoxyguanosine monophosphate (dGMP; Sigma-Aldrich) was used as the sample at a concentration of 1 μM. The same sample was passed through measurement electrodes #1 and #2. Figure 15B shows the results of tunneling current measurement. Figure 15C shows a histogram of conductance obtained by dividing the current value in Figure 15B by voltage.

[0072] The tunneling current measured when a sample passes through the nanogap of the measurement electrode varies significantly depending on the nanogap width. Therefore, when fabricating multiple measurement electrodes on substrate 2, it is desirable to fabricate them so that the nanogap widths are identical. However, it is difficult to achieve exactly the same nanogap width, and it is believed that there is no problem with the measurement accuracy of the sample as long as the measurement results are within a range of several times. As shown in Figure 15C, the average histogram value of the sample measured with measurement electrode #1 was 149 pS, and the average histogram value of the sample measured with measurement electrode #2 was 83 pS, a difference of approximately 1.8 times. The device fabricated in Example 2 was confirmed to have satisfactory measurement accuracy despite the measurement electrodes being fabricated using different processes (MCBJ process and EBJ process).

[0073] As described above, it has been confirmed that by fabricating a device using the manufacturing method disclosed in the present application, high measurement accuracy can be obtained even when two or more measurement electrodes are fabricated on the substrate 2.

[0074] Fabricating a device using the manufacturing method disclosed in the present application can improve the measurement sensitivity of the device, and is therefore useful for the development of analytical equipment in the analytical instrument industry.

[0075] REFERENCE SIGNS LIST 1, 1a...device, 2...substrate, 3, 3a...measurement electrode, 30...first metal layer, 30a...second metal layer, 31...first electrode, 31a, 31a'...first portion, 31b...first end, 31c, 31c'...first tip, 31d...first step, 32...second electrode, 32a, 32a'...second portion, 32b...second end, 32c, 32c'...second tip, 32d...second step, 33...contact rupture point, 33a...mechanical rupture point, 4...flow path, 41...measurement flow path, 42...sample input flow path, 43...first tapered flow path, 44...sample recovery flow path, 45...second tapered flow path, 50...jig, 51...projection Lifting rod, 6, 6a, 6b... power supply for electrophoresis, 61... first electrode for electrophoresis, 62... second electrode for electrophoresis, 7... tunneling current detection unit, 8... power supply for measuring tunneling current, 9... analysis unit, 10... display unit, 11... program memory, 12... control unit, α... taper angle of first portion, β... taper angle of second portion, G... nanogap, L1, L2... distance from contact breakage point, Lp... points on L1, L2, La... first virtual line, Lb... second virtual line, Lc... third virtual line, X... length of first portion, Y... length of second portion, w... width of contact breakage point, w1... width of first portion, w2... width of second portion

Claims

1. A method for manufacturing a device used for measuring tunneling current, the device comprising: a substrate; and a first electrode and a second electrode formed on the substrate to form a pair of measurement electrodes for measuring a tunneling current when a sample passes through the substrate; the manufacturing method comprising: a first metal layer laminating step of laminating, on a surface of the substrate, a first metal layer for forming the first electrode and the second electrode, the first metal layer being connected to a metal layer for forming the first electrode and the second electrode via a contact breakage point; and an electromigration step of applying a voltage to the first metal layer so as to straddle the contact breakage point, breaking the first metal layer at the contact breakage point by utilizing contact breakage due to electromigration, thereby forming the first electrode and the second electrode having a first nanogap; in the first metal layer laminated in the first metal laminating step, a metal layer portion for forming the first electrode includes a first portion connected to the contact breakage point, and a metal layer portion for forming the second electrode includes a second portion connected to the contact breakage point, The manufacturing method, wherein the first portion and the second portion are each formed in a tapered shape narrowing in width toward the contact breakage location, the first portion and the second portion are formed asymmetrically around the contact breakage location, and the first portion is formed to be wider than the second portion, and in the electromigration process, a voltage is applied so that metal in the first portion migrates toward the second portion.

2. The manufacturing method according to claim 1, wherein the width of the contact breakage point is 0.02 μm to 10 μm.

3. The method according to claim 1, wherein when the length of the first portion is defined as X and the length of the second portion is defined as Y, X+Y is 0.1 μm to 10 μm.

4. The manufacturing method according to claim 1, wherein, when the taper angle of the first portion is defined as α and the taper angle of the second portion is defined as β, α / β is in the range of 1.1 to 3.

5. The manufacturing method according to claim 1, wherein in the first metal layer lamination step, at least two of the first metal layers are laminated, and the electromigration step is performed for each of the at least two laminated first metal layers.

6. The manufacturing method according to claim 1, comprising: a second metal layer laminating step of laminating a second metal layer by a mechanical break and joining method to form a pair of measuring electrodes having a second nanogap; and a mechanical break and joining method implementing step of breaking the second metal layer by the mechanical break and joining method to form a pair of measuring electrodes having a second nanogap.

7. The manufacturing method according to claim 6, wherein the mechanical fracture joining step is performed by bringing two jigs into contact with the substrate from above and pushing the substrate between the two jigs from below with a push-up rod, and when the location on the substrate pushed up by the push-up rod is defined as a push-up fulcrum, the second metal layer is laminated at a location of the first metal layer and the second metal layer formed on the substrate that is closest to the push-up fulcrum, and the first metal layer is laminated at a location of the first metal layer and the second metal layer formed on the substrate that is farthest from the push-up fulcrum.

8. The manufacturing method according to claim 6, wherein the mechanical fracture bonding method step is first performed on the second metal layer, and then the electromigration step is performed on the first metal layer.

9. A manufacturing method as described in claim 7 or 8, wherein when the location of mechanical breakage of the second metal layer is defined as a mechanical breakage location, and a virtual line passing through the mechanical breakage location of the second metal layer laminated at a location closest to the push-up fulcrum is defined as a third virtual line, the contact breakage location is not located on the third virtual line.

10. The manufacturing method according to any one of claims 1 to 8, further comprising a flow path, and the contact breaking point and the mechanical breaking point are disposed in the flow path.

11. A device used for measuring tunneling current, comprising: a substrate; and a first electrode and a second electrode formed on the substrate to form a pair of measuring electrodes for measuring the tunneling current when a sample passes through, wherein at least two measuring electrodes are formed, and the device comprises at least one measuring electrode, the first electrode having a first tip width of 2 Å to 15 Å and the second electrode having a second tip width of 2 Å to 15 Å, and at least one measuring electrode, the first electrode having a first tip width of 0.05 μm to 0.2 μm and the second electrode having a second tip width of 0.05 μm to 0.2 μm.

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