Stacked body, electronic device, and method for manufacturing stacked body

Abstract

The stacked body (20) disclosed herein comprises a phononic crystal layer (21) and a metal layer (22). The phononic crystal layer (21) has a plurality of recesses (21h). The metal layer (22) is disposed on or above the phononic crystal layer (21). The recesses (21h) contain metal atoms of the same type as the metal atoms contained in the metal layer (22).

Description

Technical Field

[0001] This disclosure relates to laminates, electronic devices, and methods for manufacturing laminates. Background Technology

[0002] Materials with phononic crystals are known in the past.

[0003] For example, Patent Document 1, Patent Document 2, and Non-Patent Document 1 disclose a periodic structure consisting of multiple through-holes. In this periodic structure, when viewed from above, the through-holes are arranged regularly in a nanometer-scale periodic pattern in a region ranging from 1 nm to 1000 nm. This periodic structure is a type of phononic crystal. This type of phononic crystal is a periodic structure in which the smallest unit constituting the arrangement of through-holes is taken as the unit lattice.

[0004] Phononic crystals can reduce the thermal conductivity of thin films. This advantage of phononic crystals can be applied to various applications. For example, Patent Document 3 discloses a thermal infrared sensor equipped with a thin-film phononic crystal.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: U.S. Patent Application Publication No. 2017 / 0047499

[0008] Patent Document 2: U.S. Patent Application Publication No. 2017 / 0069818

[0009] Patent Document 3: Japanese Patent Application Publication No. 2017-223644

[0010] Non-patent literature

[0011] Non-patent document 1: Nomura et al., "Impeded thermal transport is Si multiscalehierarchical architectures with phononic crystal nanostructures", PhysicalReview B 91, 205422 (2015) Summary of the Invention

[0012] The problem the invention aims to solve

[0013] The aforementioned technology, from the perspective of reducing the resistance of laminates containing phononic crystals, warrants further investigation.

[0014] Therefore, this disclosure provides an advantageous technique from the viewpoint of reducing the resistance of a laminate containing phononic crystals.

[0015] Technical solutions for solving the problem

[0016] This disclosure provides the following stack-up.

[0017] A layered body having:

[0018] A phonon crystal layer having multiple recesses; and

[0019] A metal layer disposed on or above the phononic crystal layer.

[0020] The recess contains metal atoms of the same kind as the metal atoms contained in the metal layer.

[0021] Invention Effects

[0022] The laminate disclosed herein is advantageous from the viewpoint of reducing resistance. Attached Figure Description

[0023] Figure 1 This is a top view showing the phonon device of Embodiment 1.

[0024] Figure 2 It is Figure 1 The sectional view of II-II as the section line.

[0025] Figure 3 It is a schematic cross-sectional view showing the diffusion of metal atoms from the metal layer to the phonon crystal layer.

[0026] Figure 4 It is a schematic cross-sectional view showing the diffusion of metal atoms into a layer of non-phonon crystal.

[0027] Figure 5 This is a graph showing the Al concentration in samples 1 and 2 obtained based on time-of-flight secondary ion mass spectrometry (TOF-SIMS).

[0028] Figure 6 This is a graph representing the Al concentration in samples 3 and 4 obtained based on TOF-SIMS.

[0029] Figure 7A This is a scanning electron microscope (SEM) image of a cross-section of sample 1.

[0030] Figure 7B This is an SEM image of a cross-section of another sample.

[0031] Figure 8It is a graph showing the relationship between the percentage of Al concentration at a predetermined depth of the phononic crystal layer in samples 1 and 2 relative to the Al concentration at the surface of the phononic crystal layer and the depth from the surface of the phononic crystal layer.

[0032] Figure 9 This is a graph representing the Al concentration and the second derivative of the Al concentration with respect to depth in sample 1. Detailed Implementation

[0033] (The insights that form the basis of this disclosure)

[0034] The thermal conductivity of a thin film can be reduced, for example, by making the film porous. The voids formed in the film accompanying the porousing process reduce its thermal conductivity. On the other hand, based on phononic crystals, the thermal conductivity of the substrate material constituting the thin film can be reduced, and a further reduction in thermal conductivity compared to porousing is expected. Therefore, for example, it is considered to use a layer having phononic crystals and a metal layer stacked together in electronic devices such as thermal infrared sensors.

[0035] On the other hand, according to the inventors' research, it is known that the resistance of the laminate tends to increase when a phononic crystal layer and a metal layer are stacked. To improve the value of the laminate, low resistance is advantageous. Therefore, the inventors derived the concept of reducing the resistance of the laminate by diffusing metal atoms from the metal layer into the phononic crystal layer. Based on this concept, the inventors repeatedly experimented and discovered that by constructing the phononic crystal layer in a manner that allows metal atoms to be present at specific positions within the phononic crystal layer, the resistance of the laminate is easily reduced, and thus the laminate of this disclosure is proposed.

[0036] (A summary of a technical solution involved in this disclosure)

[0037] This disclosure provides the following stack-up.

[0038] A layered body having:

[0039] A phonon crystal layer having multiple recesses; and

[0040] A metal layer disposed on or above the phononic crystal layer.

[0041] The recess contains metal atoms of the same kind as the metal atoms contained in the metal layer.

[0042] In the above-described laminate, the laminate is constructed by means of phononic crystal layers as described above, and the laminate tends to have low resistance.

[0043] (Implementation of this disclosure)

[0044] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Furthermore, the embodiments described below are general or specific examples. The numerical values, shapes, materials, constituent elements, arrangement positions of constituent elements, connection methods, process conditions, steps, and order of steps shown in the following embodiments are examples and are not intended to limit the present disclosure. Additionally, constituent elements in the following embodiments that are not described in the independent claims representing the highest-level concept are described as arbitrary constituent elements. Furthermore, the figures are schematic diagrams and are not necessarily strictly illustrated.

[0045] (Implementation Method 1)

[0046] Figure 1 This is a top view showing the phonon device 1a according to embodiment 1. Figure 2 It is Figure 1 The cross-sectional view of phonon device 1a with line II-II as the section line. For example... Figure 1 and Figure 2 As shown, the phonon device 1a includes a stack 20. The stack 20 includes a phonon crystal layer 21 and a metal layer 22. The phonon crystal layer 21 has a phonon crystal, such as... Figure 2 As shown, it has multiple recesses 21h. A metal layer 22 is disposed on or above the phononic crystal layer 21. The metal layer 22 may be in direct contact with the phononic crystal layer 21, or there may be other layers, such as a bonding layer, between the metal layer 22 and the phononic crystal layer 21. In this specification, the expression "on or above" is for ease of explanation; for example, the state in which the metal layer 22 is located below the phononic crystal layer 21 in the direction of gravity is also included in the meaning expressed by this expression.

[0047] Metal atoms of the same type as those contained in metal layer 22 may exist, for example, inside the recesses 21h. With this configuration, the resistance of the laminate 20 is easily reduced. As a result, the phonon device 1a can easily achieve the desired performance. For example, metal atoms of the same type as those contained in metal layer 22 may exist inside a portion of one of the plurality of recesses 21h located directly below metal layer 22. With this configuration, the resistance of the laminate 20 can be reduced more effectively.

[0048] At a specific location in the phonon crystal layer 21, the concentration of metal atoms of the same type as those contained in the metal layer 22 is, for example, 4 × 10⁻⁶. 21 atoms / cm 3The above describes a specific location located 10 nm away from the surface 21s of the phononic crystal layer 21 in the thickness direction of the phononic crystal layer 21. In this case, the resistance of the stack 20 can be more effectively reduced. The concentration of metal atoms at this specific location in the phononic crystal layer 21 can be determined, for example, by etching the stack 20 from the surface 22a of the metal layer 22 towards the phononic crystal layer 21 in the thickness direction of the metal layer 22 while performing TOF-SIMS.

[0049] The ions used in the ion sputtering described above are not limited to any specific ions, as long as they can etch the stack 20. For example, Cs+ ions are used. Similarly, the primary ions used in TOF-SIMS are not limited to any specific ions, as long as the concentration of metal atoms in the stack 20 can be achieved. For example, Bi3+ ions are used.

[0050] At a specific location in the phonon crystal layer 21, the concentration of metal atoms of the same type as those contained in the metal layer 22 can be 5 × 10⁻⁶. 21 atoms / cm 3 The above can also be 6×10 21 atoms / cm 3 The above can also be 7×10 21 atoms / cm 3 The concentration of this metal atom at a specific location in the phonon crystal layer 21 is, for example, 5 × 10⁻⁶. 22 atoms / cm 3 the following.

[0051] The concentration of metal atoms, for example, decreases in stages between the surface 21s in the thickness direction of the phononic crystal layer 21 and the aforementioned specific location, as the distance from the surface 21s increases. If this result is obtained by simultaneously etching the stack 20 and performing TOF-SIMS, the resistance of the stack 20 can be reduced more effectively.

[0052] In the phononic crystal layer 21, the relationship between the concentration of metal atoms of the same type as those contained in the metal layer 22 and the depth from the surface 21s of the phononic crystal layer 21 is not limited to a specific relationship. The phononic crystal layer 21, for example, satisfies the condition y ≥ 100exp(-0.2326x) in the range 0 ≤ x ≤ 24. In this condition, x represents the numerical part of the depth from the surface 21s of the phononic crystal layer 21 in nanometers. y is determined by an exponential approximation of the relationship between the percentage of the concentration of metal atoms at a depth of x nanometers in the phononic crystal layer 21 relative to the concentration of metal atoms at the surface 21s and the depth x in the range 0 ≤ x ≤ 24. When the phononic crystal layer 21 satisfies such a condition, the resistance of the laminate 20 can be more reliably reduced.

[0053] In the laminate 20, the average concentration Ca of metal atoms at the intermediate portion 25 between the metal layer 22 and the phonon crystal layer 21 is not limited to a specific value. For example, the average Ca is 3.68 × 10⁻⁶. 22 atoms / cm 3 Larger. In this case, the resistance of the stack 20 can be more effectively reduced. The intermediate portion 25, for example, exists at or near the boundary between the metal layer 22 and the phonon crystal layer 21, between depth d1, where the second derivative of the concentration of metal atoms with respect to depth is minimized, and depth d2, where the second derivative is maximized. The average value Ca is determined, for example, by dividing the integral value of the concentration of metal atoms in the range of depth d1 to depth d2 by the absolute value of the difference between depth d1 and depth d2.

[0054] The average value Ca can be 3.69 × 10 22 atoms / cm 3 The above can also be 3.70 atoms / cm 3 The above. The average value Ca is, for example, 6.03 × 10⁻⁶. 22 atoms / cm 3 the following.

[0055] In the laminate 20, the absolute value |d2-d1| is not limited to a specific value. For example, the absolute value |d2-d1| is greater than 5 nm and less than 20 nm.

[0056] The material forming the phononic crystal layer 21 is not limited to a specific material. For example, the material forming the phononic crystal layer 21 may be a semiconductor material. The main component of the semiconductor material is not limited to a specific component. In this specification, the main component means the component most abundant on a mass basis. The main component of the semiconductor material forming the phononic crystal layer 21 may be, for example, Si. The semiconductor material forming the phononic crystal layer 21 may contain dopants such as B and P.

[0057] The metal atoms contained in the metal layer 22 are not limited to a specific type of metal atom. For example, the metal atom could be aluminum (Al). Due to this configuration, the metal layer 22 readily absorbs infrared radiation. The metal atoms contained in the metal layer 22 can be iron, nickel, chromium, cobalt, magnesium, tin, or zinc. The material forming the metal layer 22 can be a metal monomer, an alloy, or a conductive metal compound.

[0058] like Figure 2 As shown, in the phononic crystal layer 21, multiple recesses 21h are regularly arranged. The phononic crystal in the phononic crystal layer 21 can be either a single crystal or a polycrystalline crystal. When the phononic crystal is polycrystalline, in the top view of the phononic crystal layer 21, the phononic crystal has multiple domains, and the phononic crystal in each domain is a single crystal. In other words, the polycrystalline phononic crystal is a composite of multiple phononic single crystals. In this case, in the multiple domains, the multiple recesses 21h are regularly arranged in different directions. In each domain, the orientation of the unit lattice is the same. In the top view of the phononic crystal layer 21, the shapes of each domain can be the same or different. In the top view of the phononic crystal layer 21, the sizes of each domain can be the same or different.

[0059] The ratio of the length of the recess 21h to its diameter is not limited to a specific value. The length of the recess 21h is the length of the recess 21h in the thickness direction of the phononic crystal layer 21. This ratio is, for example, 3 or more. This ratio may also be 4 or more. This ratio is, for example, 20 or less.

[0060] like Figure 2 As shown, the recess 21h extends along the normal direction of the surface 21s of the phononic crystal layer 21. The recess 21h can extend parallel to the normal of the surface 21s, or it can extend parallel to a straight line at an angle of, for example, less than 10° relative to the normal of the surface 21s. The surface 21s is the surface of the solid portion 21k of the phononic crystal layer 21.

[0061] The recess 21h, for example, penetrates the phononic crystal layer 21 in the thickness direction, forming a through hole. Therefore, for example, the physical properties of the phononic crystal layer 21 in the thickness direction are unlikely to be non-uniform. Alternatively, in the thickness direction of the phononic crystal layer 21, one end of the recess 21h may be open, and the other end of the recess 21h may be closed by the solid portion 21k of the phononic crystal layer 21.

[0062] An example of a method for manufacturing the laminate 20 will be described. The method for manufacturing the laminate 20 includes, for example, applying a voltage to a pre-laminated laminate 20p having a phononic crystal layer 21p and a metal layer 22p, thereby generating a current between the phononic crystal layer 21p and the metal layer 22p. The phononic crystal layer 21p and the metal layer 22p in the pre-laminated laminate 20p are configured similarly to the phononic crystal layer 21 and the metal layer 22, respectively. The phononic crystal layer 21p of the pre-laminated laminate 20p can be fabricated, for example, by forming multiple recesses in a thin film using methods such as electron beam lithography and block copolymer lithography. The thin film can be formed using methods such as vacuum evaporation, ion plating, sputtering, and chemical vapor deposition (CVD). The metal layer 22p of the pre-laminated laminate 20p can be formed on the thus formed phononic crystal layer 21p using methods such as vacuum evaporation, ion plating, sputtering, and CVD.

[0063] The voltage described above is not limited to a specific value, as long as it is sufficient to manufacture the laminate 20. This voltage is higher than the voltage required to drive the phonon device 1a. The voltage may be, for example, a DC voltage, or the direction of the applied voltage may be reversed during the manufacture of the laminate 20. Figure 3 This is a schematic cross-sectional view showing the diffusion of metal atoms M from metal layer 22p to phonon crystal layer 21p due to the application of such a voltage. Figure 3 As shown, by applying a voltage, Joule heating and an electric field inducing electromigration are generated between the metal layer 22p and the phonon crystal layer 21p, causing diffusion of metal atoms M. Consequently, metal atoms M diffuse to at least one selected from the recess 21h and the solid portion 21k. Metal atoms M may diffuse only to the recess 21h, only to the solid portion 21k, or both.

[0064] By applying a voltage, for example as described above, metal atoms M are doped into the phononic crystal layer 21 such that the concentration of metal atoms M at a specific location in the phononic crystal layer 21 becomes 4 × 10⁻⁶. 21 atoms / cm 3 above.

[0065] By applying a voltage, for example, the phonon crystal layer 21 can satisfy the condition y≥100exp(-0.2326x) in the range of 0≤x≤24 as described above.

[0066] Alternatively, by applying a voltage, the average concentration of metal atoms (Ca) at the intermediate portion 25 between metal layer 22 and phonon crystal layer 21 can be changed to 3.68 × 10⁻⁶. 22 atoms / cm 3 big.

[0067] like Figure 3 As shown, by applying a voltage, metal atoms M diffuse along the length direction of the recess 21h, causing localized diffusion of metal atoms M. For example, diffusion of metal atoms M occurs in a localized portion directly below the metal layer 22p in the phononic crystal layer 21p. This reduces the resistance at the desired portion of the phononic crystal layer 21. Consequently, the resistance of the laminate 20 is easily reduced. Figure 4 The diffusion of metal atoms M is schematically illustrated when a voltage is applied to pre-stack 20q in the same manner as to pre-stack 20p. Pre-stack 20q is constructed identically to pre-stack 20p, except that the phononic crystal layer 21p is replaced with a layer 21q without a phononic crystal. Figure 4 As shown, when a voltage is applied to the pre-stacked body 20q, metal atoms M diffuse not only to a local portion of the layer 21q directly below the metal layer 22p, but also diffuse over a wider area.

[0068] It is also considered to promote the diffusion of metal atoms M from metal layer 22p to phonon crystal layer 21p by means of heat treatment of the pre-stacked layer 20p. However, in this case, the effect of heat treatment would affect the entire phonon device 1a including the stacked layer 20. On the other hand, according to the above method, heat treatment is not required, and therefore, it is possible to prevent the effect of the treatment for the diffusion of metal atoms M from affecting the entire phonon device 1a.

[0069] like Figure 1 and 2 As shown, the phonon device 1a includes a substrate 11, a thin film 12, a low thermal conductivity layer 13, a first phonon crystal layer 21a, a second phonon crystal layer 21b, a high resistivity layer 23, and a metal layer 22. The first phonon crystal layer 21a and the second phonon crystal layer 21b are phonon crystal layers 21 in the laminate 20. The phonon device 1a also includes a first wiring 17a, a second wiring 17b, a first signal processing circuit 18a, and a second signal processing circuit 18b.

[0070] Thin film 12 is formed on substrate 11. Substrate 11 is typically made of semiconductor. Semiconductor, for example, is Si. Figure 1As shown, the thin film 12 is formed, for example, to surround the first phonon crystal layer 21a, the second phonon crystal layer 21b, and the high-resistivity layer 23. The basic composition of the thin film 12 is, for example, the same as that of the phonon crystal layer 21 and the high-resistivity layer 23, and is typically made of semiconductor. The thin film 12 is, for example, a Si film. The thin film 12 can be a single-crystal material, a polycrystalline material, or an amorphous material. The first phonon crystal layer 21a and the second phonon crystal layer 21b contain, for example, dopants such as B or P. Therefore, the resistance of the first phonon crystal layer 21a and the second phonon crystal layer 21b is lower than that of the thin film 12 and the high-resistivity layer 23. The high-resistivity layer 23 is formed between the first phonon crystal layer 21a and the second phonon crystal layer 21b. The high-resistivity layer 23 is not limited to a specific material as long as it has a resistance higher than that of the first phonon crystal layer 21a and the second phonon crystal layer 21b. For example, in the high-resistivity layer 23, the concentration of metal atoms of the same type as those contained in the metal layer 22 is lower than the concentration of such metal atoms in the first phonon crystal layer 21a and the second phonon crystal layer 21b. The high-resistivity layer 23 is, for example, an intrinsic semiconductor.

[0071] For example, the first phonon crystal layer 21a contains an n-type semiconductor, and the second phonon crystal layer 21b contains a p-type semiconductor. Figure 2 As shown, the high-resistivity layer 23 is configured, for example, between the first phonon crystal layer 21a and the second phonon crystal layer 21b, in a manner that forms a coplanar plane with both the first phonon crystal layer 21a and the second phonon crystal layer 21b. Furthermore, the metal layer 22 is disposed on the high-resistivity layer 23 across the first phonon crystal layer 21a and the second phonon crystal layer 21b. Either the first phonon crystal layer 21a or the second phonon crystal layer 21b may contain an n-type semiconductor, or both may contain a p-type semiconductor.

[0072] A low thermal conductivity layer 13 is formed on the substrate 11. The thermal conductivity of the low thermal conductivity layer 13 at room temperature is, for example, 5 W / m². -1 K -1 The low thermal conductivity layer 13 can be a layer formed of a solid material with low thermal conductivity, such as SiO2, or it can be an air layer or a vacuum layer. The low thermal conductivity layer 13 is formed, for example, below the first phonon crystal layer 21a, the second phonon crystal layer 21b, and the high resistivity layer 23. The low thermal conductivity layer 13 can also be formed below the thin film 12. In this specification, the room temperature is 20°C ± 15°C according to Japanese Industrial Standard (JIS) Z 8703.

[0073] The first phonon crystal layer 21a and the second phonon crystal layer 21b are disposed, for example, on the low thermal conductivity layer 13. A metal layer 22 is disposed on the first phonon crystal layer 21a, the second phonon crystal layer 21b, and the high resistivity layer 23, covering a portion of the phonon crystals in the first phonon crystal layer 21a and the second phonon crystal layer 21b. Thus, a connection portion 14a is formed between the metal layer 22 and the first phonon crystal layer 21a, and a connection portion 14b is formed between the metal layer 22 and the second phonon crystal layer 21b. Either the first phonon crystal layer 21a or the second phonon crystal layer 21b can also be replaced with a layer without phonon crystals.

[0074] like Figure 1 As shown, a first wiring 17a, a second wiring 17b, a first signal processing circuit 18a, and a second signal processing circuit 18b are disposed on a thin film 12. The first wiring 17a and the second wiring 17b are each made of a conductive, doped semiconductor or metal. The first wiring 17a and the second wiring 17b are formed, for example, as an Al film. The first wiring 17a and the second wiring 17b are in contact with the first phonon crystal layer 21a and the second phonon crystal layer 21b, respectively. Thus, a connection portion 14c is formed between the first wiring 17a and the first phonon crystal layer 21a, and a connection portion 14d is formed between the second wiring 17b and the second phonon crystal layer 21b. Furthermore, electrical connections between the first wiring 17a and the first phonon crystal layer 21a and between the second wiring 17b and the second phonon crystal layer 21b are ensured. The first signal processing circuit 18a and the second signal processing circuit 18b can each have the same configuration as well-known signal processing circuits capable of processing electrical signals.

[0075] like Figure 1 As shown, the width of the first phonon crystal layer 21a, the second phonon crystal layer 21b, the high-resistivity layer 23, and the metal layer 22 in the y-axis direction is not limited to a specific value. These widths can be the same or different. The width of the low thermal conductivity layer 13 is larger than the widths of the first phonon crystal layer 21a, the second phonon crystal layer 21b, the high-resistivity layer 23, and the metal layer 22.

[0076] Phononic device 1a functions, for example, as an infrared sensor.

[0077] The areas of the connection portions 14a and 14b between the phononic crystal layer 21 and the metal layer 22 are smaller than those in the case where the phononic crystal layer 21 is replaced by a layer without a phononic crystal, due to the presence of multiple recesses 21h in the phononic crystal layer 21. Therefore, the contact resistance at the connection portions 14a and 14b tends to be high. However, in the stack 20 of the phononic device 1a, as described above, the metal atoms M contained in the metal layer 22 locally diffuse into the phononic crystal layer 21, thus reducing the contact resistance at the connection portions 14a and 14b.

[0078] It is believed that due to the presence of multiple recesses 21h in the phononic crystal layer 21, the contact resistance at the connection portions 14c and 14d is also prone to increase. For example, when the first wiring 17a and the second wiring 17b are metal layers, the metal atoms contained in the metal layer can be locally diffused into the phononic crystal layer 21. This also reduces the contact resistance at the connection portions 14c and 14d. The composition of the material forming the metal layer 22 and the materials forming the first wiring 17a and the second wiring 17b can be the same or different.

[0079] An example of a method for reducing the contact resistance at connections 14a, 14b, 14c, and 14d will be described. The first signal processing circuit 18a and the second signal processing circuit 18b are configured, for example, to apply a DC voltage between them. The first signal processing circuit 18a and the second signal processing circuit 18b are configured, for example, to apply a voltage higher than that required to drive the phonon device 1a. This voltage is, for example, 50V or higher. When such a voltage is applied between the first signal processing circuit 18a and the second signal processing circuit 18b, a current is generated in the circuit 30. The circuit 30 consists of the first signal processing circuit 18a, the first wiring 17a, the connection 14c, the first phonon crystal layer 21a, the connection 14a, the metal layer 22, the connection 14b, the second phonon crystal layer 21b, the connection 14d, the second wiring 17b, and the second signal processing circuit 18b. Consequently, in the portions corresponding to the connections 14a, 14b, 14c, and 14d, due to Joule heating and the electric field, the metal atoms contained in the metal layer 22, the first wiring 17a, and the second wiring 17b diffuse toward the phononic crystal layer 21. As a result, the contact resistance at the connections 14a, 14b, 14c, and 14d can be reduced.

[0080] As described above, the resistance of the high-resistivity layer 23 is higher than that of the first phonon crystal layer 21a and the second phonon crystal layer 21b. Therefore, even when a voltage is applied as described above, almost no current is generated in the high-resistivity layer 23, and the metal atoms contained in the metal layer 22 hardly diffuse into the high-resistivity layer 23. Thin films such as silicon oxide thin films and silicon nitride thin films can also be formed between the high-resistivity layer 23 and the metal layer 22.

[0081] Alternatively, instead of using the first signal processing circuit 18a and the second signal processing circuit 18b, another power source can be used to apply the aforementioned voltage between the first wiring 17a and the second wiring 17b of circuit 30. In this case, it is not necessary to configure the first signal processing circuit 18a and the second signal processing circuit 18b to be able to apply a high voltage between them, which reduces the design limitations of the first signal processing circuit 18a and the second signal processing circuit 18b.

[0082] As described above, an electronic device including a phonon device 1a and the like, having a stacked body 20, can be provided. The electronic device having the stacked body 20 is not limited to the phonon device 1a. The electronic device having the stacked body 20 can also be an electronic device other than the phonon device 1a.

[0083] Example

[0084] Hereinafter, the laminate of this embodiment will be described in more detail with reference to the embodiments. However, the laminate of this embodiment is not limited to the technical solutions shown in the following embodiments.

[0085] (Sample 1)

[0086] A silicon substrate with a SiO2 layer on one side was prepared. A 100 nm thick Si film was deposited on the SiO2 layer of the silicon substrate using vapor deposition. The Si film was a film of silicon monomers free of impurities. Unwanted portions of the Si film were removed by selective etching, leaving a rectangular Si layer with both ends connected to the surrounding Si film. Next, multiple through-holes regularly arranged in the in-plane direction of the Si layer were formed by electron beam lithography or block copolymer lithography, giving the Si layer a phononic crystal structure. The diameter of each through-hole is approximately 26 nm, and the distance between the centers of adjacent through-holes in the in-plane direction of the Si layer is approximately 38 nm. Next, the rectangular Si layer, except for the central portion, was doped. The portion of the Si layer connected to the central end in the length direction was doped to p-type, and the portion connected to the other end of the central end was doped to n-type. Thus, the rectangular Si layer has p-type, undoped, and n-type portions in the order of p-type, undoped, and n-type portions in the length direction. An Al layer was formed by vapor deposition to continuously cover the undoped portion, a portion of the p-type region, and a portion of the n-type region of the Si layer. Next, a 70V DC voltage was applied to both ends of the rectangular Si layer. During the application of the DC voltage, the voltage direction was reversed midway. This process produced sample 1.

[0087] (Sample 2)

[0088] Sample 2 was fabricated in the same manner as Sample 1, except that no DC voltage was applied to the two ends of the rectangular Si layer.

[0089] (Sample 3)

[0090] Sample 3 was fabricated in the same manner as Sample 1, except that the Si layer was not given a phononic crystal structure.

[0091] (Sample 4)

[0092] Sample 4 was fabricated in the same manner as Sample 2, except that the Si layer was not given a phononic crystal structure.

[0093] Using the TOF-SIMS device TOF.SIMS5 manufactured by ION-TOF, TOF-SIMS was performed on the overlapping portions of the Al layer and the p-type or n-type regions in samples 1, 2, 3, and 4. TOF-SIMS was performed while etching the sample from the surface of the Al layer towards the p-type or n-type regions using ion sputtering. Cs+ was used in the ion sputtering, and Bi3+ was used for the primary ion in the TOF-SIMS. The Al concentration in the thickness direction of each sample was obtained based on the TOF-SIMS results. The results related to samples 1 and 2 are shown below. Figure 5 The results relating to samples 3 and 4 are expressed as follows: Figure 6 Additionally, SEM images of the cross-section of sample 1 are shown below. Figure 7A SEM images of another sample, prepared in the same manner as sample 2, are shown below. Figure 7B .

[0094] The resistivity between the two ends of the rectangular Si layers in samples 1, 2, and 4 was measured. The measurements were performed at room temperature. The results are shown in Table 1.

[0095] like Figure 5 As shown, the curves for samples 1 and 2, which are Al layers, with depths ranging from 0 nm to 75 nm, are interpreted as corresponding to the Al layers, with a depth of approximately 6 × 10⁻⁶. 22 atoms / cm 3 Al was detected at high concentrations. Figure 5 The dashed line in the graph represents a depth of 75 nm. In the graphs for samples 1 and 2, the Al concentration decreases with increasing depth above 75 nm. The graphs for samples 1 and 2 at depths above 75 nm are interpreted as corresponding to the Si layer with a phononic crystal. Thus, the location of the boundary between the Al and Si layers can be determined based on the graphs for samples 1 and 2. In the graph for sample 2, the Al concentration at a position 10 nm from the boundary between the Al and Si layers into the interior of the Si layer is less than 4 × 10⁻⁶. 21 atoms / cm 3On the other hand, in the curve for sample 1, the Al concentration at a position 10 nm away from the boundary between the Al and Si layers and into the interior of the Si layer is 4 × 10⁻⁶. 21 atoms / cm 3 The above is approximately twice that of sample 2. Figure 5 The double-dotted line in the figure corresponds to a position 10 nm away from the boundary between the Al and Si layers and into the interior of the Si layer. Figure 5 The dashed line in the middle and 4×10 21 atoms / cm 3 The Al concentration corresponds to the concentration of the sample. By comparing the curves for sample 1 and sample 2, it is suggested that, upon application of voltage, the Al contained in the Al layer diffuses into the Si layer with the phononic crystal.

[0096] When the target of TOF-SIMS has a phononic crystal structure, considering the measurement principle of TOF-SIMS, it is also believed that the measurement sensitivity of TOF-SIMS is not necessarily high due to the presence of through holes in the phononic crystal structure.

[0097] like Figure 6 As shown, the curves for samples 3 and 4, which are Al layers, with depths ranging from 0 nm to 80 nm, are interpreted as corresponding to the Al layers, with a depth of approximately 6 × 10⁻⁶. 22 atoms / cm 3 Al was detected at high concentrations. In the curves for samples 3 and 4, the Al concentration decreased with increasing depth above 80 nm; the curves for samples 3 and 4 at depths above 80 nm are interpreted as corresponding to the Si layer. In the curve for sample 4, the Al concentration at a position 20 nm from the boundary between the Al and Si layers into the interior of the Si layer is approximately 3 × 10⁻⁶. 20 atoms / cm 3 This is a low concentration. On the other hand, in the curve for sample 3, the Al concentration at a position 20 nm away from the boundary between the Al and Si layers and into the interior of the Si film is 4 × 10⁻⁶. 21 atoms / cm 3 The above concentrations, when compared with the graphs for sample 3 and sample 4, suggest that Al contained in the Al layer diffuses into the Si layer upon application of voltage. In samples 3 and 4, the Si layer lacks a phonon crystal structure; therefore, the TOF-SIMS measurement sensitivity is considered high. The significant difference in Al concentration within the Si layer in samples 3 and 4 is understood to be due to these differences. It is speculated that a similar significant difference in Al concentration also occurs in samples 1 and 2.

[0098] like Figure 7AAs shown, in sample 1, Al is present inside the through-holes of the Si layer containing the phononic crystal. It is also speculated that, due to the presence of Al inside these through-holes, the difference in Al concentration in the phononic crystal layers of samples 1 and 2, as measured by TOF-SIMS, becomes smaller than the difference in Al concentration in the Si layers of samples 3 and 4. On the other hand, it is believed that the presence of Al inside these through-holes can promote Al diffusion into the solid portion of the Si layer containing the phononic crystal. Figure 7B As shown, in other samples made in the same manner as sample 2, Al could not be visually confirmed inside the through-holes of the Si layer with phononic crystals.

[0099] As shown in Table 1, the resistivity between the two ends of the Si layer in sample 2 is 24 mΩ·cm, compared to 5.4 mΩ·cm in sample 1. Furthermore, the resistivity between the two ends of the Si layer in sample 4 is 5.8 mΩ·cm. The resistivity between the two ends of the Si layer in sample 1 is lower than that in sample 4, which has a Si layer without a phononic crystal. This suggests that by applying a voltage between the Si layer with a phononic crystal and the Al layer, Al diffuses from the Al layer, significantly reducing the contact resistance between the Al and Si layers.

[0100] [Table 1]

[0101]

[0102] Figure 8 This is a graph showing the relationship between the Al concentration Cx / Cs ratio (Cx / Cs) and the depth from the surface of the Si layer with the phononic crystal in samples 1 and 2. Al concentration Cs is the Al concentration at the surface of the Si layer with the phononic crystal. Al concentration Cx is the Al concentration at a depth of x nanometers in the Si layer with the phononic crystal. Figure 8 In the diagram, the approximate curve of the solid line is determined by an exponential approximation of the relationship between the ratio Cx / Cs and the depth x nanometers in sample 1 for 0 ≤ x ≤ 24. This approximate curve is represented as y = 102.9313exp(-0.2214x). Figure 8 In the diagram, the approximate curve represented by the dashed line is determined by an exponential approximation of the relationship between the ratio Cx / Cs and the depth x nanometers in sample 2 for the range 0 ≤ x ≤ 24. This approximate curve is expressed as y = 85.4387exp(-0.2326x). Figure 8 In Sample 1, the Si layer with a phononic crystal satisfies the condition y ≥ 100exp(-0.2326x) in the range 0 ≤ x ≤ 24. On the other hand, the Si layer with a phononic crystal in Sample 2 does not satisfy this condition.

[0103] Figure 9 This is a graph representing the Al concentration and the second derivative of the Al concentration with respect to depth in sample 1. Figure 9 In the graph, the solid line represents the Al concentration, and the dashed line represents the second derivative of the Al concentration with respect to depth. In samples 1 and 2, based on the second derivative of the Al concentration with respect to depth, the middle portion between the Al layer and the Si layer with the phononic crystal is defined as the region between depths d1 and d2. Depth d1 is the depth corresponding to the minimum value of the second derivative of the Al concentration with respect to depth, and depth d2 is the depth corresponding to the maximum value of this second derivative. The average Al concentration Ca in the middle portion is determined by dividing the integral value of the Al concentration between depths d1 and d2 by the absolute value |d2-d1|. The results are shown in Table 2.

[0104] [Table 2]

[0105]

[0106] The embodiments of this disclosure have been described above, but this disclosure is not limited to such embodiments. For example, a phononic crystal layer may be provided on top of a metal film, or a metal film may be provided to cover a phononic crystal layer. Therefore, the depth direction of the recess in the phononic crystal layer is not limited to being perpendicular to the substrate. Furthermore, the recess is not limited to being a through hole, and the shape of the hole is not limited.

[0107] Industrial availability

[0108] The stack disclosed herein is useful for various phononic devices, such as infrared sensors, which have a connection between a phononic crystal layer and a metal layer.

Claims

1. A laminate comprising: a phononic crystal layer having a plurality of recesses; and a metal layer disposed on or above the phononic crystal layer, wherein a metal atom of the same kind as a metal atom included in the metal layer is present inside the recess.

2. The laminate according to claim 1, wherein the phononic crystal layer has a thickness of 100 nm or more.

3. The laminate according to claim 1, wherein the phononic crystal layer satisfies a condition of y > 100exp(-0.2326x) in a range of 0 < x < 24, wherein x is a numerical portion when a depth from a surface of the phononic crystal layer is expressed in nanometers, and wherein y is determined by an exponential approximation of a relationship between a percentage of a concentration of the metal atom at x nanometers of the depth with respect to a concentration of the metal atom at the surface and the depth in a range of 0 < x < 24.

4. The laminate according to claim 1, wherein the metal atom is aluminum.

5. The laminate according to claim 2, wherein a concentration of the metal atom decreases stepwise with an increase in a distance from the surface between the surface and the position in a thickness direction of the phononic crystal layer. The concentration of the metal atoms at a position 10 nm away from the surface of the phononic crystal layer in the thickness direction of the phononic crystal layer toward the inside of the phononic crystal layer is 4 x 10 21 atoms / cm 3 or more.

6. The laminate according to any one of claims 1 to 5, wherein the plurality of recesses are regularly arranged.

7. The laminate according to any one of claims 1 to 5, wherein a ratio of a length of the recess in a thickness direction of the phononic crystal layer to a diameter of the recess is 3 or more.

8. The laminate according to any one of claims 1 to 5, wherein the recess extends along a normal direction of a surface of the phononic crystal layer.

9. The laminate according to any one of claims 1 to 5, wherein the metal atom is aluminum.

10. The laminate according to any one of claims 1 to 5, further comprising a high-resistance layer, wherein the phononic crystal layer has a first phononic crystal layer including an n-type semiconductor and a second phononic crystal layer including a p-type semiconductor, wherein the high-resistance layer is disposed between the first phononic crystal layer and the second phononic crystal layer in a manner of forming a same plane as the first phononic crystal layer and the second phononic crystal layer, and wherein the metal layer is disposed on the high-resistance layer across the first phononic crystal layer and the second phononic crystal layer. The average value of the concentration of the metal atoms at the intermediate portion between the metal layer and the phononic crystal layer is greater than 3.68 x 10 22 atoms / cm 3 Large.

11. An electronic device comprising the laminate according to any one of claims 1 to 10.

12. A method for manufacturing a laminate, comprising: applying a voltage to cause a current to flow between a phononic crystal layer having a plurality of recesses and a metal layer disposed on or above the phononic crystal layer in a preliminary laminate, and diffusing a metal atom from the metal layer to the recess by the application of the voltage.

13. The method for manufacturing a laminate according to claim 12, wherein the phononic crystal layer satisfies a condition of y > 100exp(-0.2326x) in a range of 0 < x < 24 by the application of the voltage, wherein x is a numerical portion when a depth from a surface of the phononic crystal layer is expressed in nanometers, and wherein y is determined by an exponential approximation of a relationship between a percentage of a concentration of the metal atom at x nanometers of the depth with respect to a concentration of the metal atom at the surface and the depth in a range of 0 < x < 24.

14. The method for manufacturing a laminate according to claim 12, wherein the metal atom is aluminum.

15. The method for manufacturing a laminate according to claim 12, wherein a concentration of the metal atom decreases stepwise with an increase in a distance from the surface between the surface and the position in a thickness direction of the phononic crystal layer. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ includes: ​ ​ ​ The concentration of the metal atoms at a position 10 nm away from the surface of the phonon crystal layer toward the inside of the phonon crystal layer in the thickness direction of the phonon crystal layer is adjusted to 4 x 10 21 atoms / cm 3 or more by the application of the voltage. ​ ​ In the condition, x is a numerical portion when a nanometer is used to represent a depth from a surface of the phononic crystal layer in the phononic crystal layer, In the condition, y is determined by an exponential approximation of a relationship between a percentage of a concentration of the metal atom at x nanometer depth of the phononic crystal layer with respect to a concentration of the metal atom at the surface and the depth in a range of 0≤x≤24.

15. The method of manufacturing a laminate according to claim 12, The average value of the concentration of the metal atoms at the intermediate portion between the metal layer and the phonon crystal layer is adjusted to a value larger than 3.68 x 10 22 atoms / cm 3 by the application of the voltage.

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