Laminate, electronic device, and method for manufacturing a laminate

Abstract

A multilayer body 20 according to the present disclosure is provided with a phononic crystal layer 21 and a metal layer 22. The phononic crystal layer 21 has a plurality of recessed parts 21h. The metal layer 22 is arranged on top of or above the phononic crystal layer 21. Metal atoms of the same kind as the metal atoms contained in the metal layer 22 are present within the recessed parts 21h.

Description

[Technical Field]

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

[0002] Materials having phononic crystals have been known conventionally.

[0003] For example, Patent Documents 1, 2, and 1 disclose a periodic structure composed of multiple through-holes. In this periodic structure, when the thin film is viewed in plan, the through-holes are arranged regularly with a period of the order of nanometers in the range of 1 nanometer (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 a unit cell.

[0004] Phononic crystals can reduce the thermal conductivity of thin films. These advantages of phononic crystals can be applied to a variety of uses. For example, Patent Document 3 discloses a thermal infrared sensor equipped with a thin-film phononic crystal. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] U.S. Patent Application Publication No. 2017 / 0047499 Specification [Patent Document 2] U.S. Patent Application Publication No. 2017 / 0069818 [Patent Document 3] Japanese Patent Publication No. 2017-223644 [Non-patent literature]

[0006] [Non-Patent Document 1] Nomura et al., "Impeded thermal transport is Si multiscale hierarchical architectures with phononic crystal nanostructures", Physical Review B 91, 205422 (2015)

Summary of the Invention

Problems to be Solved by the Invention

[0007] The above technology has room for reconsideration from the perspective of reducing the electrical resistance of a laminate provided with a phononic crystal.

[0008] Therefore, the present disclosure provides an advantageous technology from the perspective of reducing the electrical resistance of a laminate provided with a phononic crystal. [[ID=^15]]

Means for Solving the Problems

[0009] The present disclosure provides the following laminate. A laminate comprising: a phononic crystal layer having a plurality of recesses; and a metal layer disposed on or above the phononic crystal layer, where metal atoms of the same type as those contained in the metal layer are present inside the recesses.

Advantages of the Invention

[0010] The laminate of the present disclosure is advantageous from the perspective of reducing electrical resistance.

Brief Description of the Drawings

[0011] <……> [Figure 1] FIG. 1 is a plan view showing a phononic device according to Embodiment 1. [Figure 2] FIG. 2 is a cross-sectional view taken along the cutting line II-II of FIG. 1. [Figure 3]Figure 3 is a schematic cross-sectional view illustrating the diffusion of metal atoms from the metal layer to the phononic crystal layer. [Figure 4] Figure 4 is a schematic cross-sectional view illustrating the diffusion of metal atoms into a layer that does not contain a phononic crystal. [Figure 5] Figure 5 is a graph showing the Al concentrations in samples 1 and 2, obtained based on time-of-flight secondary ion mass spectrometry (TOF-SIMS). [Figure 6] Figure 6 is a graph showing the Al concentrations in samples 3 and 4, obtained based on TOF-SIMS. [Figure 7A] Figure 7A is a scanning electron microscope (SEM) image of a cross-section of sample 1. [Figure 7B] Figure 7B is an SEM image of a cross-section of another sample. [Figure 8] Figure 8 is a graph showing the relationship between the percentage of Al concentration at a predetermined depth of the phononic crystal layer relative to the Al concentration at the surface of the phononic crystal layer, and the depth from the surface of the phononic crystal layer, for samples 1 and 2. [Figure 9] Figure 9 is a graph showing the Al concentration and the second derivative of the Al concentration with respect to depth in Sample 1. [Modes for carrying out the invention]

[0012] (Knowledge that forms the basis of this disclosure) The thermal conductivity of a thin film can be reduced, for example, by making the thin film porous. The voids formed in the thin film due to porosity reduce its thermal conductivity. On the other hand, phononic crystals can reduce the thermal conductivity of the base material that makes up the thin film, and a further reduction in thermal conductivity can be expected compared to porosity. For this reason, for example, in electronic devices such as thermal infrared sensors, it is conceivable to use a layer having a phononic crystal and a metal layer stacked together.

[0013] On the other hand, the inventors' studies have shown that when a phononic crystal layer and a metal layer are laminated, the electrical resistance of the laminate tends to be high. To increase the value of the laminate, it is advantageous for the laminate to have low electrical resistance. Therefore, the inventors conceived the idea of ​​reducing the electrical resistance of the laminate by diffusing metal atoms in the metal layer toward the phononic crystal layer. Based on this idea, the inventors conducted repeated trials and errors and found that the electrical resistance of the laminate could be easily reduced by configuring the phononic crystal layer so that metal atoms are present at specific positions in the phononic crystal layer, and thus devised the laminate of this disclosure.

[0014] (Summary of one aspect of this disclosure) This disclosure provides the following laminates. It is a laminate, A phononic crystal layer having multiple recesses, The phononic crystal layer comprises a metal layer disposed on or above the phononic crystal layer, Here, Metal atoms of the same type as those contained in the metal layer are present inside the recess.

[0015] In the above-described laminate, the phononic crystal layer is configured as described above, which makes the laminate prone to having low electrical resistance.

[0016] (Embodiments of the present disclosure) The embodiments of this disclosure will be described below with reference to the drawings. The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions of components, connection configurations, process conditions, steps, and step order shown in the embodiments below are examples and are not intended to limit this disclosure. Furthermore, components in the embodiments below that are not described in the independent claim representing the highest-level concept will be described as optional components. The figures are schematic diagrams and are not necessarily strictly accurate representations.

[0017] (Embodiment 1) Figure 1 is a plan view showing a phononic device 1a of Embodiment 1, and Figure 2 is a cross-sectional view of the phononic device 1a with the line II-II in Figure 1 as the cutting line. As shown in Figures 1 and 2, the phononic device 1a comprises a laminate 20. The laminate 20 comprises a phononic crystal layer 21 and a metal layer 22. The phononic crystal layer 21 has a phononic crystal and, as shown in Figure 2, has a plurality of recesses 21h. The metal layer 22 is positioned above or above the phononic crystal layer 21. The metal layer 22 may be in direct contact with the phononic crystal layer 21, or another layer, such as a bonding layer, may exist between the metal layer 22 and the phononic crystal layer 21. In this specification, the expression "above or above" is for convenience and includes, for example, a state in which the metal layer 22 is located below the phononic crystal layer 21 in the direction of gravity.

[0018] Metal atoms of the same type as those contained in the metal layer 22 are present, for example, inside the recesses 21h. With such a configuration, the electrical resistance of the laminate 20 tends to be low. As a result, the phononic device 1a is more likely to exhibit the desired performance. For example, metal atoms of the same type as those contained in the metal layer 22 may be present inside some of the multiple recesses 21h located directly beneath the metal layer 22. With such a configuration, the electrical resistance of the laminate 20 tends to be lower more reliably.

[0019] At a specific location in the phononic crystal layer 21, the concentration of metal atoms of the same type as those contained in the metal layer 22 is, for example, 4 × 10⁻¹⁰ 21 atoms / cm 3The above is the case. The specific position is a position 10 nm away from the surface 21s of the phononic crystal layer 21 into the interior of the phononic crystal layer 21 in the thickness direction of the phononic crystal layer 21. In this case, the electrical resistance of the laminate 20 is more likely to be surely low. The concentration of metal atoms at a specific position in the phononic crystal layer 21 can be determined, for example, by performing TOF-SIMS while etching the laminate 20 by ion sputtering from the surface 22a of the metal layer 22 toward the phononic crystal layer 21 in the thickness direction of the metal layer 22.

[0020] The ions used for the above ion sputtering are not limited to specific ions as long as the laminate 20 can be etched. The ions are, for example, Cs + and so on. Also, the primary ions used in TOF-SIMS are not limited to specific ions as long as the concentration of metal atoms in the laminate 20 can be obtained. The primary ions are, for example, Bi3 + and so on.

[0021] The concentration of metal atoms of the same type as those contained in the metal layer 22 at a specific position in the phononic crystal layer 21 may be 5×10 21 atoms / cm 3 or more, may be 6×10 21 atoms / cm 3 or more, or may be 7×10 21 atoms / cm 3 or more. The concentration of the metal atoms at a specific position in the phononic crystal layer 21 is, for example, 5×10 22 atoms / cm 3 or less.

[0022] The concentration of metal atoms, for example, decreases stepwise as the distance from the surface 21s increases between the surface 21s and the above specific position in the thickness direction of the phononic crystal layer 21. If such a result is obtained by performing TOF-SIMS while etching the laminate 20, the electrical resistance of the laminate 20 is more likely to be surely low.

[0023] In the phononic crystal layer 21, metal atoms of the same type as those contained in the metal layer 22 The relationship between the concentration of the phononic crystal layer 21 and the depth from the surface 21s is limited to a specific relationship. It is not determined. The phononic crystal layer 21 is, for example, y≧100exp(-0.2326x) The following condition is satisfied in the range 0 ≤ x ≤ 24. In this condition, x is the phononic connection. The depth from the surface 21s of the phononic crystal layer 21 in the crystal layer 21 is measured in nanometers. to This is the numerical part when expressed in terms of y. y is determined by 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 and the depth x, in the range of 0 ≤ x ≤ 24, relative to the concentration of metal atoms on the surface 21s. When the phononic crystal layer 21 satisfies these conditions, the electrical resistance of the laminate 20 is more likely to be lower.

[0024] In the laminate 20, the average value Ca of the concentration of metal atoms in the intermediate portion 25 between the metal layer 22 and the phononic crystal layer 21 is not limited to a specific value. The average value Ca is, for example, 3.68 × 10⁻⁶. 22 atoms / cm 3 It is greater. In this case, the electrical resistance of the laminate 20 is more likely to be lower. The intermediate portion 25 exists, for example, at or near the boundary between the metal layer 22 and the phononic crystal layer 21, between a depth d1 corresponding to the value at which the second derivative of the concentration of metal atoms with respect to depth is minimized, and a depth d2 corresponding to the value at which the second derivative is maximized. The average value Ca is determined, for example, by dividing the integral of the concentration of metal atoms in the range from depth d1 to depth d2 by the absolute value of the difference between depth d1 and depth d2.

[0025] The average value of Ca is 3.69 × 10⁻⁶. 22 atoms / cm 3 It may be more than that, or 3.70 ×10 22 atoms / cm 3 The above values ​​may also be used. The average value Ca is, for example, 6.03 × 10⁻⁶. 22 atoms / cm3 The following applies:

[0026] In the laminate 20, the absolute value |d2-d1| is not limited to a specific value. The absolute value |d2-d1| is, for example, between 5 nm and 20 nm.

[0027] The material forming the phononic crystal layer 21 is not limited to a specific material. The material forming the phononic crystal layer 21 is, for example, 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 that is present in the most abundant amount by mass. The main component of the semiconductor material forming the phononic crystal layer 21 is, for example, Si. The semiconductor material forming the phononic crystal layer 21 may contain dopants such as B and P.

[0028] The metal atoms contained in the metal layer 22 are not limited to any particular type of metal atom. For example, these metal atoms may be aluminum (Al). With this configuration, the metal layer 22 readily absorbs infrared radiation. The metal atoms contained in the metal layer 22 may be iron, nickel, chromium, cobalt, magnesium, tin, or zinc. The material forming the metal layer 22 may be a single metal, an alloy, or a conductive metal compound.

[0029] As shown in Figure 2, in the phononic crystal layer 21, the multiple recesses 21h are arranged regularly. The phononic crystal in the phononic crystal layer 21 may be a single crystal or a polycrystalline material. When the phononic crystal is polycrystalline, in a plan 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, a polycrystalline phononic crystal is a composite of multiple phononic single crystals. In this case, in the multiple domains, the multiple recesses 21h are arranged regularly in different directions. The orientation of the unit cell is the same in each domain. In a plan view of the phononic crystal layer 21, the shapes of each domain may be the same or different. In a plan view of the phononic crystal layer 21, the sizes of each domain may be the same or different.

[0030] The ratio of the length of the recess 21h to the diameter of the recess 21h 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.

[0031] As shown in Figure 2, the recess 21h extends along the direction normal to the surface 21s of the phononic crystal layer 21. The recess 21h may extend parallel to the normal to the surface 21s, or it may extend parallel to a straight line that makes an angle of, for example, 10° or less with respect to the normal to the surface 21s. The surface 21s is the surface of the solid portion 21k of the phononic crystal layer 21.

[0032] The recess 21h penetrates the phononic crystal layer 21 in the thickness direction, forming a through hole. This makes it less likely for the physical properties of the phononic crystal layer 21 to vary in the thickness direction. 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.

[0033] An example of a method for manufacturing the laminate 20 is described below. The method for manufacturing the laminate 20 includes, for example, applying a voltage to a preliminary laminate 20p comprising a phononic crystal layer 21p and a metal layer 22p to generate 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 preliminary laminate 20p are configured similarly to the phononic crystal layer 21 and the metal layer 22, respectively. The phononic crystal layer 21p of the preliminary laminate 20p can be fabricated by forming a plurality of recesses in a thin film, for example, by methods such as electron beam lithography and block copolymer lithography. The thin film can be formed by methods such as vacuum deposition, ion plating, sputtering, and chemical vapor deposition (CVD). The metal layer 22p of the preliminary laminate 20p can be formed on the phononic crystal layer 21p thus formed by methods such as vacuum deposition, ion plating, sputtering, and CVD.

[0034] The above voltage is not limited to a specific value as long as the laminate 20 can be manufactured. The voltage is higher than the voltage required to drive the phononic device 1a. The voltage is, for example, a DC voltage, and the direction of the applied voltage may be reversed during the manufacturing of the laminate 20. Figure 3 is a schematic cross-sectional view showing the diffusion of metal atoms M from the metal layer 22p to the phononic crystal layer 21p upon application of such a voltage. As shown in Figure 3, the application of voltage causes the generation of Joule heat and an electric field that induces electromigration between the metal layer 22p and the phononic crystal layer 21p, resulting in the diffusion of metal atoms M. As a result, the metal atoms M diffuse into at least one selected from the group consisting of recesses 21h and solid parts 21k. The metal atoms M may diffuse only into recesses 21h, or only into solid parts 21k, or into both recesses 21h and solid parts 21k.

[0035] By applying a voltage, for example, as described above, the concentration of metal atoms M at a specific location in the phononic crystal layer 21 becomes 4 × 10⁻⁶ 21 atoms / cm 3As described above, metal atoms M are doped into the phononic crystal layer 21.

[0036] By applying a voltage, for example, the phononic crystal layer 21 can satisfy the condition y≧100exp(-0.2326x) in the range 0≦x≦24, as described above.

[0037] Upon application of voltage, the average value of the concentration of metal atoms Ca in the intermediate portion 25 between the metal layer 22 and the phononic crystal layer 21 is 3.68 × 10⁻⁶. 22 atoms / cm 3 It's okay for it to get bigger.

[0038] As shown in Figure 3, when a voltage is applied, metal atoms M diffuse along the length of the recess 21h, causing localized diffusion of metal atoms M. For example, the diffusion of metal atoms M occurs in a localized area directly beneath the metal layer 22p in the phononic crystal layer 21p. This reduces the electrical resistance in a desired area of ​​the phononic crystal layer 21. As a result, the electrical resistance of the laminate 20 tends to be lower. Figure 4 schematically shows the diffusion of metal atoms M when a voltage is applied to a preliminary laminate 20q in the same way as to the preliminary laminate 20p. The preliminary laminate 20q is constructed in the same way as the preliminary laminate 20p, except that the phononic crystal layer 21p is replaced with a layer 21q that does not have a phononic crystal. As shown in Figure 4, when a voltage is applied to the preliminary laminate 20q, the metal atoms M diffuse not only in a localized area of ​​the layer 21q directly beneath the metal layer 22p, but also over a wider area.

[0039] It is conceivable to promote the diffusion of metal atoms M from the metal layer 22p to the phononic crystal layer 21p by methods such as heat treatment of the pre-laminated structure 20p. However, in this case, the heat treatment may affect the entire phononic device 1a, including the laminate 20. On the other hand, with the above method, heat treatment is unnecessary, so it is possible to prevent the effects of the treatment for the diffusion of metal atoms M from affecting the entire phononic device 1a.

[0040] As shown in Figures 1 and 2, the phononic device 1a comprises a base substrate 11, a thin film 12, a low thermal conductivity layer 13, a first phononic crystal layer 21a, a second phononic crystal layer 21b, a high electrical resistance layer 23, and a metal layer 22. The first phononic crystal layer 21a and the second phononic crystal layer 21b are the phononic crystal layers 21 in the laminate 20. The phononic device 1a further comprises a first wiring 17a, a second wiring 17b, a first signal processing circuit 18a, and a second signal processing circuit 18b.

[0041] The thin film 12 is formed on a base substrate 11. The base substrate 11 is typically made of a semiconductor. The semiconductor is, for example, Si. As shown in Figure 1, the thin film 12 is formed to surround, for example, the first phononic crystal layer 21a, the second phononic crystal layer 21b, and the high electrical resistance layer 23. The basic composition of the thin film 12 is, for example, the same as that of the phononic crystal layer 21 and the high electrical resistance layer 23, and is typically made of a semiconductor. The thin film 12 is, for example, a Si film. The thin film 12 may be a single crystal material, a polycrystalline material, or an amorphous material. The first phononic crystal layer 21a and the second phononic crystal layer 21b contain, for example, a dopant such as B or P. Therefore, the electrical resistance of the first phononic crystal layer 21a and the second phononic crystal layer 21b is lower than the electrical resistance of the thin film 12 and the high electrical resistance layer 23. The high-resistance layer 23 is formed between the first phononic crystal layer 21a and the second phononic crystal layer 21b. The high-resistance layer 23 is not limited to a specific material, as long as it has a higher electrical resistance than the electrical resistances of the first phononic crystal layer 21a and the second phononic crystal layer 21b. For example, in the high-resistance 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 those metal atoms in the first phononic crystal layer 21a and the second phononic crystal layer 21b. The high-resistance layer 23 is, for example, an intrinsic semiconductor.

[0042] For example, the first phononic crystal layer 21a contains an n-type semiconductor, and the second phononic crystal layer 21b contains a p-type semiconductor. As shown in Figure 2, the high-resistance layer 23 is arranged, for example, between the first phononic crystal layer 21a and the second phononic crystal layer 21b, forming a coplanar plane with the first phononic crystal layer 21a and the second phononic crystal layer 21b. In addition, the metal layer 22 is arranged on the high-resistance layer 23, spanning the first phononic crystal layer 21a and the second phononic crystal layer 21b. Both the first phononic crystal layer 21a and the second phononic crystal layer 21b may contain an n-type semiconductor, or both the first phononic crystal layer 21a and the second phononic crystal layer 21b may contain a p-type semiconductor.

[0043] The low thermal conductivity layer 13 is formed on the base substrate 11. The thermal conductivity of the low thermal conductivity layer 13 at room temperature is, for example, 5 Wm². -1 K -1 The following applies: The low thermal conductivity layer 13 may be a layer formed of a solid material having low thermal conductivity such as SiO2, an air layer, or a vacuum layer. The low thermal conductivity layer 13 is formed, for example, below the first phononic crystal layer 21a, the second phononic crystal layer 21b, and the high electrical resistance layer 23. The low thermal conductivity layer 13 may also be formed below the thin film 12. In this specification, room temperature is defined as 20°C ± 15°C in accordance with Japanese Industrial Standard (JIS) Z 8703.

[0044] The first phononic crystal layer 21a and the second phononic crystal layer 21b are arranged, for example, on a low thermal conductivity layer 13. The metal layer 22 is arranged on the first phononic crystal layer 21a, the second phononic crystal layer 21b, and the high electrical resistance layer 23, and covers a portion of the phononic crystals of the first phononic crystal layer 21a and the second phononic crystal layer 21b. As a result, a connection portion 14a is formed between the metal layer 22 and the first phononic crystal layer 21a, and a connection portion 14b is formed between the metal layer 22 and the second phononic crystal layer 21b. One of the first phononic crystal layer 21a and the second phononic crystal layer 21b may be changed to a layer that does not have phononic crystals.

[0045] As shown in Figure 1, the first wiring 17a, the second wiring 17b, the first signal processing circuit 18a, and the second signal processing circuit 18b are arranged on the 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 as, for example, Al films. The first wiring 17a and the second wiring 17b are in contact with the first phononic crystal layer 21a and the second phononic crystal layer 21b, respectively. As a result, a connection portion 14c is formed between the first wiring 17a and the first phononic crystal layer 21a, and a connection portion 14d is formed between the second wiring 17b and the second phononic crystal layer 21b. Furthermore, electrical connections are ensured between the first wiring 17a and the first phononic crystal layer 21a, and between the second wiring 17b and the second phononic crystal layer 21b. The first signal processing circuit 18a and the second signal processing circuit 18b may each have a configuration similar to that of a known signal processing circuit capable of processing electrical signals.

[0046] As shown in Figure 1, for example, the widths, which are the lengths in the y-axis direction of the first phononic crystal layer 21a, the second phononic crystal layer 21b, the high electrical resistance layer 23, and the metal layer 22, are not limited to any specific value. These widths may be the same or different. The width of the low thermal conductivity layer 13 is greater than the widths of the first phononic crystal layer 21a, the second phononic crystal layer 21b, the high electrical resistance layer 23, and the metal layer 22.

[0047] The phononic device 1a functions, for example, as an infrared sensor.

[0048] The area of ​​the connection portions 14a and 14b between the phononic crystal layer 21 and the metal layer 22 is smaller than when the phononic crystal layer 21 is replaced with a layer that does not have phononic crystals, due to the presence of multiple recesses 21h in the phononic crystal layer 21. Therefore, the contact electrical resistance at the connection portions 14a and 14b tends to be high. However, in the laminate 20 of the phononic device 1a, as described above, the metal atoms M contained in the metal layer 22 are locally diffused into the phononic crystal layer 21, so the contact electrical resistance at the connection portions 14a and 14b is reduced.

[0049] The presence of multiple recesses 21h in the phononic crystal layer 21 is thought to increase the contact electrical resistance at the connection points 14c and 14d. For example, if the first wiring 17a and the second wiring 17b are metal layers, metal atoms contained in these metal layers can be locally diffused into the phononic crystal layer 21. This can reduce the contact electrical resistance at the connection points 14c and 14d. The composition of the material forming the metal layer 22 and the material forming the first wiring 17a and the second wiring 17b may be the same or different.

[0050] An example of a method for reducing contact electrical resistance at connection points 14a, 14b, 14c, and 14d will be described. The first signal processing circuit 18a and the second signal processing circuit 18b are configured to allow a DC voltage to be applied between them, for example. The first signal processing circuit 18a and the second signal processing circuit 18b are configured to allow a voltage higher than the voltage required to drive the phononic device 1a to be applied between them, for example. 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 is composed of the first signal processing circuit 18a, the first wiring 17a, connection point 14c, the first phononic crystal layer 21a, connection point 14a, metal layer 22, connection point 14b, the second phononic crystal layer 21b, connection point 14d, the second wiring 17b, and the second signal processing circuit 18b. As a result, in the portions corresponding to the connection parts 14a, 14b, 14c, and 14d, metal atoms contained in the metal layer 22, the first wiring 17a, and the second wiring 17b diffuse toward the phononic crystal layer 21 due to Joule heating and the electric field. Consequently, the contact electrical resistance at the connection parts 14a, 14b, 14c, and 14d is reduced.

[0051] As described above, the electrical resistance of the high-resistance layer 23 is higher than that of the first phononic crystal layer 21a and the second phononic crystal layer 21b. Therefore, even when a voltage is applied as described above, almost no current is generated in the high-resistance layer 23, and the metal atoms contained in the metal layer 22 hardly diffuse into the high-resistance layer 23. A thin film, such as a silicon oxide thin film or a silicon nitride thin film, may be formed between the high-resistance layer 23 and the metal layer 22.

[0052] The above voltage may be applied between the first wiring 17a and the second wiring 17b of circuit 30 using a separate power supply, without using the first signal processing circuit 18a and the second signal processing circuit 18b. 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, and the design constraints on the first signal processing circuit 18a and the second signal processing circuit 18b can be reduced.

[0053] As described above, an electronic device equipped with a laminate 20 such as a phononic device 1a can be provided. The electronic device equipped with the laminate 20 is not limited to the phononic device 1a. The electronic device equipped with the laminate 20 may be an electronic device other than the phononic device 1a. [Examples]

[0054] The laminate of this embodiment will be described in more detail below with reference to the examples. However, the laminate of this embodiment is not limited to the embodiments shown below.

[0055] (Sample 1) A silicon substrate having an SiO2 layer on one main surface was prepared. A 100 nm thick Si film was formed on the SiO2 layer of the silicon substrate by vapor deposition. The Si film was a pure silicon film free of impurities. Unnecessary portions of the Si film were selectively etched away so that a rectangular Si layer with both ends connected to the surrounding Si film remained. Next, multiple through-holes regularly arranged in the in-plane direction of the Si layer were formed in the Si layer by electron beam lithography or block copolymer lithography, thereby imparting a phononic crystal structure to the Si layer. The diameter of each through-hole was approximately 26 nm, and the distance between the centers of adjacent through-holes in the in-plane direction of the Si layer was approximately 38 nm. Next, doping was performed on the portion of the rectangular Si layer excluding the center. The portion of the Si layer touching one end of the center in the longitudinal direction was doped in the p-type, and the portion touching the other end of the center was doped in the n-type. As a result, the rectangular Si layer had p-type portions, undoped portions, and n-type portions in that order in the longitudinal direction. An Al layer was formed by vapor deposition to continuously cover the undoped area, a portion of the p-type region, and a portion of the n-type region of the Si layer. Next, a DC voltage of 70V was applied to both ends of the rectangular Si layer. The direction of the DC voltage was reversed midway through the application process. Sample 1 was prepared in this manner.

[0056] (Sample 2) Sample 2 was prepared in the same manner as Sample 1, except that a DC voltage was not applied to both ends of the rectangular Si layer.

[0057] (Sample 3) Sample 3 was prepared in the same manner as Sample 1, except that a phononic crystal structure was not imparted to the Si layer.

[0058] (Sample 4) Sample 4 was prepared in the same manner as Sample 2, except that a phononic crystal structure was not imparted to the Si layer.

[0059] TOF-SIMS was performed on samples 1, 2, 3, and 4 using the TOF.SIMS5 system manufactured by ION-TOF, focusing on the areas where the Al layer overlapped with the p-type or n-type regions. TOF-SIMS was carried out by etching the sample from the surface of the Al layer towards the p-type or n-type regions using ion sputtering. Cs was used for ion sputtering. + Using this method, the primary ion for TOF-SIMS is Bi3 + The following was used: The concentration of Al in the thickness direction of each sample was obtained from the TOF-SIMS results. The results for samples 1 and 2 are shown in Figure 5, and the results for samples 3 and 4 are shown in Figure 6. In addition, an SEM image of the cross section of sample 1 is shown in Figure 7A. An SEM image of another sample prepared in the same manner as sample 2 is shown in Figure 7B.

[0060] The electrical resistivity between the ends of the rectangular Si layers in samples 1, 2, and 4 was measured. This measurement was performed at room temperature. The results are shown in Table 1.

[0061] As shown in Figure 5, the graphs for samples 1 and 2, from a depth of 0 nm to a depth of 75 nm, which are the surface of the Al layer, are understood to correspond to the Al layer, and Al is approximately 6 × 10⁻⁶ 22 atoms / cm 3It was detected at a high concentration. The dashed line in Figure 5 indicates a depth of 75 nm. In the graphs for samples 1 and 2, the Al concentration decreases as the depth increases above 75 nm. The graphs for samples 1 and 2 at depths above 75 nm are understood to correspond to the Si layer containing the phononic crystal. Thus, the location of the boundary between the Al layer and the Si layer can be determined from the graphs for samples 1 and 2. In the graph for sample 2, the Al concentration at a position 10 nm away from the boundary between the Al layer and the Si layer into the Si layer is 4 × 10⁻⁶. 21 atoms / cm 3 It was less than . On the other hand, in the graph for sample 1, the Al concentration at a position 10 nm away from the boundary between the Al layer and the Si layer into the Si layer was 4 × 10 21 atoms / cm 3 The above results were approximately twice as high as in Sample 2. The dashed line in Figure 5 corresponds to a position 10 nm away from the boundary between the Al and Si layers, inside the Si layer. The dashed line in Figure 5 corresponds to 4 × 10 21 atoms / cm 3 This corresponds to the Al concentration. A comparison of the graph for Sample 1 and the graph for Sample 2 suggests that when voltage is applied, the Al contained in the Al layer diffuses into the Si layer which has a phononic crystal.

[0062] When the target of TOF-SIMS has a phononic crystal structure, considering the measurement principle of TOF-SIMS, it can be argued that the measurement sensitivity of TOF-SIMS may not necessarily be high due to the presence of through-holes in the phononic crystal structure.

[0063] As shown in Figure 6, the graphs for samples 3 and 4, from a depth of 0 nm to a depth of 80 nm, which are the surface of the Al layer, are understood to correspond to the Al layer, and Al is approximately 6 × 10⁻⁶ 22 atoms / cm 3It was detected at high concentrations. In the graphs for samples 3 and 4, the Al concentration decreases as the depth increases above 80 nm, and it is understood that the graphs for samples 3 and 4 at depths above 80 nm correspond to the Si layer. In the graph for sample 4, the Al concentration at a position 20 nm away from the boundary between the Al layer and the Si layer into the Si layer is approximately 3 × 10⁻⁶. 20 atoms / cm 3 The concentration was this low. On the other hand, in the graph for sample 3, the Al concentration at a position 20 nm away from the boundary between the Al layer and the Si layer into the Si film was 4 × 10 21 atoms / cm 3 The concentrations were as described above. A comparison of the graphs for Sample 3 and Sample 4 suggests that the Al contained in the Al layer diffuses into the Si layer upon voltage application. Since the Si layer in Samples 3 and 4 does not have a phononic crystal structure, it is thought that the measurement sensitivity of TOF-SIMS is high. It is understood that the Al concentration in the Si layer differs significantly between Samples 3 and 4. It is presumed that similar large differences in Al concentration also occur in Samples 1 and 2.

[0064] As shown in Figure 7A, in Sample 1, Al is present inside the through-pores of the Si layer containing the phononic crystal. It is presumed that the presence of Al inside these through-pores resulted in a smaller difference in Al concentration in the phononic crystal layers of Samples 1 and 2, as measured by TOF-SIMS, compared to the difference in Al concentration in the Si layers of Samples 3 and 4. On the other hand, the presence of Al inside these through-pores is thought to promote the diffusion of Al into the solid portion of the Si layer containing the phononic crystal. As shown in Figure 7B, in another sample prepared in the same manner as Sample 2, Al could not be visually confirmed inside the through-pores of the Si layer containing the phononic crystal.

[0065] As shown in Table 1, the electrical resistivity between the ends of the Si layer in Sample 2 was 24 mΩ·cm, while the electrical resistivity between the ends of the Si layer in Sample 1 was 5.4 mΩ·cm. Furthermore, the electrical resistivity between the ends of the Si layer in Sample 4 was 5.8 mΩ·cm. The electrical resistivity between the ends of the Si layer in Sample 1 was lower than that of the Si layer in Sample 4, which had a Si layer without a phononic crystal. This suggests that applying a voltage between the Si layer with a phononic crystal and the Al layer causes Al to diffuse from the Al layer, significantly reducing the contact electrical resistance between the Al layer and the Si layer.

[0066] [Table 1]

[0067] Figure 8 is a graph showing the relationship between the Al concentration ratio Cx / Cs (Al concentration to Al concentration Cs) and the depth from the surface of the Si layer containing the phononic crystal in samples 1 and 2. Al concentration Cs is the Al concentration at the surface of the Si layer containing the phononic crystal. Al concentration Cx is the Al concentration at a depth of x nanometers in the Si layer containing the phononic crystal. In Figure 8, the solid line approximation curve was determined by exponential approximation of the relationship between the ratio Cx / Cs and the depth x nanometers for sample 1 in the range 0 ≤ x ≤ 24. This approximation curve is expressed as y = 102.9313exp(-0.2214x). In Figure 8, the dashed line approximation curve was determined by exponential approximation of the relationship between the ratio Cx / Cs and the depth x nanometers for sample 2 in the range 0 ≤ x ≤ 24. This approximation curve is expressed as y = 85.4387exp(-0.2326x). According to Figure 8, the Si layer with a phononic crystal in Sample 1 satisfied 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 did not satisfy this condition.

[0068] Figure 9 is a graph showing the Al concentration and the second derivative of the Al concentration with respect to depth in Sample 1. In Figure 9, the solid line graph shows the Al concentration, and the dashed line graph shows the second derivative of the Al concentration with respect to depth. In Samples 1 and 2, the intermediate region between the Al layer and the Si layer containing the phononic crystal was defined as the portion between depths d1 and d2, based on the second derivative of the Al concentration with respect to depth. 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 that second derivative. The average value Ca of the Al concentration in the intermediate region was determined by dividing the integral value of the Al concentration between depths d1 and d2 by its absolute value |d2-d1|. The results are shown in Table 2.

[0069] [Table 2]

[0070] Although embodiments of the present disclosure have been described above, the present disclosure is not limited to such embodiments. For example, the metal film may be provided so as to cover the phononic crystal layer, such as in a configuration where the phononic crystal layer is provided on top of the metal film. Therefore, the depth direction of the recess in the phononic crystal layer is not limited to being perpendicular to the base substrate. Furthermore, the recess is not limited to being a through hole, and the shape of the hole is also not limited. [Industrial applicability]

[0071] The laminate of this disclosure is useful for various phononic devices, such as infrared sensors, having a connection portion where a phononic crystal layer and a metal layer are connected.

Claims

1. It is a laminate, A phononic crystal layer having multiple recesses, The interior of the recess contains a cavity. The phononic crystal layer comprises a metal layer disposed on or above the phononic crystal layer, A metal of the same type as the metal contained in the metal layer is present inside the recess. Laminated structure.

2. In the thickness direction of the phononic crystal layer, the concentration of the metal at a position 10 nm away from the surface of the phononic crystal layer to the interior of the phononic crystal layer is 4 × 10 21 atoms / cm 3 That's all. The laminate according to claim 1.

3. The phononic crystal layer satisfies the condition y≧100exp(-0.2326x) in the range 0≦x≦24. In the above conditions, x is the numerical part of the depth of the phononic crystal layer from the surface of the phononic crystal layer, expressed in nanometers. In the above conditions, y is determined by exponentially approximating the relationship between the percentage of the concentration of the metal at a depth of x nanometers in the phononic crystal layer and the depth, with respect to the concentration of the metal on the surface, in the range of 0 ≤ x ≤ 24. The laminate according to claim 1.

4. The average concentration of the metal in the intermediate portion between the metal layer and the phononic crystal layer is 3.68 × 10⁻¹⁴. 22 atoms / cm 3 Larger, The laminate according to claim 1.

5. The concentration of the metal decreases in steps with increasing distance from the surface of the phononic crystal layer in the thickness direction of the phononic crystal layer, between the surface and the position. The laminate according to claim 2.

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

7. The laminate according to any one of claims 1 to 6, wherein the ratio of the length of the recess in the thickness direction of the phononic crystal layer to the diameter of the recess is 3 or more.

8. The recess extends along the direction normal to the surface of the phononic crystal layer. The laminate according to any one of claims 1 to 7.

9. The aforementioned metal is aluminum. The laminate according to any one of claims 1 to 8.

10. Furthermore, it is equipped with a high electrical resistance layer, The phononic crystal layer comprises a first phononic crystal layer containing an n-type semiconductor and a second phononic crystal layer containing a p-type semiconductor. The high electrical resistance layer is arranged between the first phononic crystal layer and the second phononic crystal layer in the same plane as the first phononic crystal layer and the second phononic crystal layer. The metal layer is arranged on the high electrical resistance layer, spanning the first phononic crystal layer and the second phononic crystal layer. The laminate according to any one of claims 1 to 9.

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

12. A method for manufacturing a laminate, A pre-laminate comprising a phononic crystal layer having a plurality of recesses and a metal layer disposed above or above the phononic crystal layer, wherein a voltage is applied to generate a current between the phononic crystal layer and the metal layer, By applying the aforementioned voltage, metal atoms are diffused from the metal layer to at least one selected from the group consisting of the recess and the solid portion of the phononic crystal layer. A method for manufacturing laminates.

13. By applying the aforementioned voltage, 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 is increased to 4 × 10 21 atoms / cm 3 Adjust to the above. A method for manufacturing a laminate according to claim 12.

14. Upon application of the aforementioned voltage, the phononic crystal layer satisfies the condition y≧100exp(-0.2326x) in the range 0≦x≦24. In the above conditions, x is the numerical part of the depth of the phononic crystal layer from the surface of the phononic crystal layer, expressed in nanometers. In the above conditions, y is determined by exponentially approximating the relationship between the concentration of the metal atoms at a depth of x nanometers in the phononic crystal layer and the depth, with respect to the concentration of the metal atoms on the surface, in the range of 0 ≤ x ≤ 24. A method for manufacturing a laminate according to claim 12.

15. By applying the aforementioned voltage, the average concentration of the metal atoms in the intermediate portion between the metal layer and the phononic crystal layer is reduced to 3.68 × 10⁻¹⁰. 22 atoms / cm 3 Adjust to a larger value. A method for manufacturing a laminate according to claim 12.

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