Semiconductor device, manufacturing method of semiconductor device, solar cell, and manufacturing method of solar cell

Abstract

To provide a semiconductor device and a solar battery, each having a bonding structure that reliability of the semiconductor device and the solar battery is improved, and provide a manufacturing method of them.SOLUTION: A semiconductor device or a solar battery, comprises: a first semiconductor element SB1 that contains a silicon layer, and includes a first bonding surface; a second semiconductor element SB2 that includes a second bonding surface opposite to the first bonding surface; and a plurality of conductive nano particles 23 that is positioned between the first bonding surface and the second bonding surface, and electrically connects the first semiconductor element SB1 and the second semiconductor element SB2. The plurality of conductive nano particles 23 is the semiconductor device or the solar battery, which is entered into the silicon layer. Also, the first semiconductor element SB1 and the second semiconductor element SB2 are prepared, the plurality of conductive nano particles 23 is arranged onto the first bonding surface of the first semiconductor element SB1, and the plurality of conductive nano particles 23 is entered into the silicon layer. After that, the first and second bonding surfaces are opposite via the plurality of conductive nano particles 23, and are pressed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device and a manufacturing method thereof, and also to a solar cell and a manufacturing method thereof, and relates to a technique that is effective when applied to a bonding layer used to stack a plurality of solar cell units, for example. [Background technology]

[0002] Known semiconductor devices include a multi-junction solar cell, which is a solar cell that can achieve high performance by stacking multiple cells. For example, a multi-junction solar cell with a high-efficiency GaAs-based solar cell as the top cell (light-receiving side) and a low-cost Si-based solar cell as the bottom cell (non-light-receiving side) is expected to realize a highly efficient and low-cost solar cell. Manufacturing methods for such solar cells include stacking the top cell and the bottom cell using crystal growth technology and mechanical stacking using bonding technology (mechanical stacking method).

[0003] For example, one mechanical stacking method is a bonding technology (hereinafter referred to as smart stack technology) in which conductive nanoparticles such as Pd are arranged on the bonding interface and the top cell and bottom cell are bonded through these nanoparticles (Patent Document 1, Non-Patent Document 1).Furthermore, with regard to this smart stack technology, surface treatment of the bonding surfaces is also being investigated (Non-Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5875124 [Non-patent literature]

[0005] [Non-Patent Document 1] H. Mizuno, et al., Japanese Journal of Applied Physics 55, 025001 (2016) [Non-patent document 2] K. Makita, et al.,35th European Photovoltaic Solar Energy Conference and Exhibition,(2018), p20-22. [Non-patent document 3] K. Makita, et al., Progress in Photovoltaics, Research and Applications, 28, (2020), p16-24. Summary of the Invention [Problem to be solved by the invention]

[0006] In the smart stack technology described in the above literature, the top cell and the bottom cell are electrically connected using conductive nanoparticles. However, the junction structure is important because it determines the battery performance and the quality of the semiconductor device, and ultimately affects the reliability of the semiconductor device and solar cell. An object of the present invention is to provide a semiconductor device or solar cell having a junction structure that improves the reliability of the semiconductor device or solar cell, and a method for manufacturing the same. [Means for solving the problem]

[0007] To solve the above problems, the inventors conducted extensive research and discovered that by allowing conductive nanoparticles that electrically connect the first semiconductor element and the second semiconductor element to penetrate into the silicon layer of the first semiconductor element, the electrical connection between the first semiconductor element and the second semiconductor element is improved and a stable bonding structure is formed. This in turn leads to improved battery performance and semiconductor device quality. Specifically, the following configuration was adopted. (1) In one embodiment, the semiconductor device includes a silicon layer, a first semiconductor element having a first bonding surface, a second semiconductor element having a second bonding surface opposite the first bonding surface, and a plurality of conductive nanoparticles located between the first bonding surface and the second bonding surface and electrically connecting the first semiconductor element and the second semiconductor element, the plurality of conductive nanoparticles being embedded in the silicon layer. (2) In one embodiment, a solar cell is a solar cell including the semiconductor device described in (1), wherein the silicon layer of the first semiconductor element includes a semiconductor material of crystalline silicon or amorphous silicon, and the second semiconductor element includes one or more semiconductor materials selected from the group consisting of GaAs, AlGaAs, InGaP, InGaAsP, AlGaInP, InGaAs, chalcogenide-based, perovskite-based, and organic-based.

[0008] (3) In one embodiment, a method for manufacturing a semiconductor device includes: (a) preparing a first semiconductor element including a silicon layer and having a first bonding surface; (b) preparing a second semiconductor element having a second bonding surface; (c) arranging a plurality of conductive nanoparticles on the first bonding surface; (d) after step (c), inserting the plurality of conductive nanoparticles into the silicon layer; and (e) after step (d), pressing the second bonding surface against the first bonding surface via the plurality of conductive nanoparticles. (4) In one embodiment, a method for manufacturing a solar cell includes the method for manufacturing a semiconductor device according to (3), and uses a semiconductor material of crystalline silicon or amorphous silicon as the silicon layer of the first semiconductor element, and uses one or more semiconductor materials selected from GaAs, AlGaAs, InGaP, InGaAsP, AlGaInP, InGaAs, chalcogenide-based, perovskite-based, and organic-based materials as the second semiconductor element. [Effects of the Invention]

[0009] According to one embodiment, it is possible to provide a semiconductor device or a solar cell having a junction structure that improves the reliability of the semiconductor device or the solar cell, and a method for manufacturing the same. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating the configuration of a semiconductor device (multi-junction solar cell) according to an embodiment of the present invention. [Figure 2] 1A to 1C are schematic diagrams illustrating a method for manufacturing a multi-junction solar cell. [Figure 3] FIG. 1 is a diagram illustrating the principle of the metal-assisted chemical etching (MACE) method. [Figure 4] FIG. 1 is a diagram showing the configuration of a multi-junction solar cell according to another embodiment 1 (example). [Figure 5] FIG. 10 is a diagram showing the configuration of a multi-junction solar cell according to another embodiment 2. [Figure 6] FIG. 10 is a diagram showing the configuration of a multi-junction solar cell according to another embodiment 3. [Figure 7] FIG. 10 is a diagram illustrating the configuration of another example of a multi-junction solar cell. [Figure 8] FIG. 10 is a diagram illustrating the configuration of another example of a multi-junction solar cell. [Figure 9] FIG. 1 is a diagram showing the relationship between voltage and current density of a multi-junction solar cell. [Figure 10] 1 is an atomic force microscope (AFM) photograph of a Si surface after MACE treatment of a multi-junction solar cell (Example). [Figure 11] 1A and 1B are atomic force microscope images of the Si surface of a multi-junction solar cell without MACE treatment (A) and with BHF treatment (B) (comparative example). [Figure 12] Photographs of each multi-junction solar cell (samples A to C). [Figure 13] These are photographs of each multi-junction solar cell (samples A to C) after nitrogen blowing. [Figure 14] FIG. 1 shows a TEM image of Sample A and the results of analysis by energy dispersive X-ray spectroscopy (TEM-EDX) (Example). [Figure 15]FIG. 10 shows a TEM image of Sample B and the results of analysis by energy dispersive X-ray spectroscopy (TEM-EDX) (Comparative Example). DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts. In this specification, when a numerical range is indicated, the upper and lower limits are included.

[0012] (Embodiment 1) The technical concept of this embodiment can be widely applied to semiconductor devices in which first and second semiconductor elements made of different semiconductor materials are electrically connected and stacked. Below, this technical concept will be explained using a solar cell as an example. FIG. 1 shows a structural diagram of a semiconductor device (multi-junction solar cell) according to this embodiment. In FIG. 1, multi-junction solar cell 1 includes a bottom cell solar cell element SB1 and a top cell solar cell element SB2. Here, solar cell element SB1 is made of a silicon cell. Meanwhile, solar cell element SB2 is made of a GaAs cell. A multi-junction solar cell is a solar cell that combines cells with different properties. It is composed of a transparent upper "top cell" that receives direct sunlight and a lower "bottom cell." By combining different materials, it is possible to utilize light of a wide wavelength range, thereby improving conversion efficiency. Note that throughout this specification, solar cell elements may be simply referred to as cells.

[0013] The solar cell element SB1 of the bottom cell has a p-type silicon substrate 13 on which a p-type electrode 11 is formed, and an n-type silicon layer 15 formed on the p-type substrate 13. The solar cell element SB2 of the top cell has a p-type GaAs layer 17 that functions as a light absorption layer, an n-type GaAs layer 19 formed on the p-type GaAs layer 17, and an n-type electrode 21 formed on the n-type GaAs layer 19. As shown in FIG. 1, the solar cell element SB1 and the solar cell element SB2 are bonded together by a plurality of conductive nanoparticles 23. This allows the solar cell element SB1 and the solar cell element SB2 to be mechanically bonded and electrically connected. For example, nanoparticles made of palladium (Pd) can be used as the conductive nanoparticles 23.

[0014] In such a multi-junction solar cell 1, when sunlight including visible light and infrared light is irradiated from above the solar cell element SB2, the sunlight irradiates the n-type GaAs layer 19, which is a component of the solar cell element SB2, and enters the n-type GaAs layer 19 and the p-type GaAs layer 17 located below the n-type GaAs layer 19. Since the n-type GaAs layer 19 and the p-type GaAs layer 17 have a band gap of 1.42 eV, sunlight with an optical energy of 1.42 eV or more is absorbed. Specifically, electrons in the valence band of the GaAs layer (n-type GaAs layer 19 and p-type GaAs layer 17) receive optical energy from the sunlight and are excited to the conduction band. This accumulates electrons in the conduction band and generates holes in the valence band. In this way, when sunlight irradiates the solar cell element SB2, the sunlight with an optical energy of 1.42 eV or more excites electrons in the conduction band of the GaAs layer and generates holes in the valence band of the GaAs layer. The conduction band of the n-type GaAs layer 19, which constitutes one side of the pn junction, is at a position with lower electronic energy than the conduction band of the p-type GaAs layer 17, which constitutes the other side of the pn junction. As a result, electrons excited to the conduction band move to the n-type GaAs layer 19 and are accumulated in the n-type GaAs layer 19. Meanwhile, holes present in the valence band move to the p-type GaAs layer 17 and are accumulated in the p-type GaAs layer 17. As a result, an electromotive force (V1) is generated between the p-type GaAs layer 17 and the n-type GaAs layer 19.

[0015] On the other hand, sunlight with an optical energy less than 1.42 eV is not absorbed by the GaAs layer and passes through the GaAs layer. As a result, in FIG. 1, sunlight with an optical energy less than 1.42 eV is incident on solar cell element SB1, which is disposed below solar cell element SB2. At this time, because n-type silicon layer 15 and p-type silicon substrate 13 have a band gap of 1.12 eV, sunlight with an optical energy less than 1.42 eV and equal to or greater than 1.12 eV is absorbed. Specifically, electrons in the valence band of the silicon layer (n-type silicon layer 15 and p-type silicon substrate 13) receive optical energy supplied from sunlight and are excited to the conduction band. As a result, electrons are accumulated in the conduction band and holes are generated in the valence band. In this way, when solar cell element SB1 is irradiated with sunlight, electrons are excited in the conduction band of the silicon layer by light having an optical energy of less than 1.42 eV and equal to or greater than 1.12 eV, and holes are generated in the valence band of the silicon layer. As a result, holes are accumulated in p-type silicon substrate 13, while electrons present in the conduction band are accumulated in n-type silicon layer 15. As a result, an electromotive force (V2) is generated between p-type silicon substrate 13 and n-type silicon layer 15.

[0016] Here, solar cell element SB1 and solar cell element SB2 are connected in series by a plurality of conductive nanoparticles 23. In other words, solar cell element SB1 and solar cell element SB2 are connected in series. As a result, an electromotive force consisting of electromotive forces (V1) and (V2) is generated in multi-junction solar cell 1 consisting of solar cell element SB1 and solar cell element SB2 connected in series. Then, for example, when a load is connected between n-type electrode 21 and p-type electrode 11, electrons flow from n-type electrode 21 through the load to p-type electrode 11. In other words, current flows from p-type electrode 11 through the load to n-type electrode 21. In this way, the load can be driven by operating multi-junction solar cell 1.

[0017] Furthermore, the multi-junction solar cell 1 can absorb both high-energy light contained in sunlight and low-energy light and convert them into electrical energy, thereby improving photoelectric conversion efficiency. In other words, the multi-junction solar cell 1 is excellent in that it can improve the efficiency of sunlight utilization by utilizing low-energy light that cannot be utilized by a single solar cell.

[0018] Next, the features of the multi-junction solar cell 1 of this embodiment will be described. This multi-junction solar cell 1 is characterized by a junction structure in which conductive nanoparticles 23 that join solar cell elements SB1 and SB2 penetrate into the silicon layer, in this example, n-type silicon layer 15. This provides the effects of both improved conductivity and mechanical bonding strength at the junction between solar cell elements SB1 and SB2. The structure of the multi-junction solar cell is described in detail below.

[0019] (Solar cell element SB1) Solar cell element SB1 has a p-type silicon substrate 13 on which a p-type electrode 11 is formed and an n-type silicon layer 15 formed on the p-type silicon substrate 13, and is also called a silicon cell. The p-type electrode 11 is made of, for example, a silver film or an aluminum film. The bottom cell is preferably made of inexpensive silicon (silicon cell) that absorbs light in the long wavelength range. Examples include single crystal silicon, polycrystalline silicon, microcrystalline silicon, and amorphous silicon. Solar cell element SB1 has a band gap of, for example, 1.12 eV, and absorbs sunlight with an optical energy of 1.12 eV or more.

[0020] The solar cell element SB1 is fabricated by the following method. First, a p-type silicon substrate 13 is prepared. Then, after cleaning the surface of the p-type silicon substrate 13, an n-type silicon layer 15 is formed on one side of the p-type silicon substrate 13 by, for example, thermal diffusion or ion implantation. At this time, an oxidized region 25 (SiO2) of about 1 nm to 20 nm is formed on the entire surface or part of the n-type silicon layer 15 by high-temperature treatment during thermal diffusion, or by annealing heat treatment to activate the implanted dopant material in the case of ion implantation. Finally, a p-type electrode 11 is formed by, for example, sputtering, to form the layer structure shown in FIG. 1.

[0021] (Solar cell element SB2) Solar cell element SB2 has a p-type GaAs layer 17, an n-type GaAs layer 19 formed on the p-type GaAs layer 17, and an n-type electrode 21 formed on the n-type GaAs layer 19. The n-type electrode 21 is formed of an alloy film such as AuGeNi / Au or TiAu / Au. The top cell may be a highly efficient GaAs cell that absorbs light in the short wavelength range, or a CIGS (Cu, In, Ga, Se) layer (CIGS-based cell) or an InGaP layer (InGaP-based cell). In solar cell element SB2, for example, the GaAs cell has a band gap of 1.42 eV, and sunlight with an optical energy of 1.42 eV or more is absorbed.

[0022] The solar cell element SB2 is fabricated by the following method. First, a stacked structure of the solar cell element SB2, including a p-type GaAs layer 17 and an n-type GaAs layer 19, is formed on a GaAs substrate (not shown) whose surface has been cleaned using a conventional process. The stacked structure can be formed using a crystal growth method such as metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). Then, an n-type electrode 21 is formed on the n-type GaAs layer 19 by electron beam evaporation. Note that the n-type electrode 21 can also be formed by other methods, such as direct current magnetron sputtering, resistance heating evaporation, screen printing, or electrodeposition. The n-type electrode 21 is patterned in a grid shape to ensure a light-transmitting area. Then, the solar cell element SB2 is separated from the GaAs substrate using epitaxial lift-off (ELO). This completes the stacked structure of the solar cell element SB2. In this way, an interface that will become a bonding surface is formed in the solar cell element SB2, and since this is a surface that has been separated from the GaAs substrate by the ELO method, flatness suitable for bonding with the conductive nanoparticles 23 is ensured. The solar cell element SB1 and the solar cell element SB2 can be fabricated by any known method, not limited to the above method. In addition, it does not matter which of the solar cell element SB1 and the solar cell element SB2 is fabricated first.

[0023] (Conductive Nanoparticles 23) The conductive nanoparticles 23 electrically connect the solar cell element SB1 and the solar cell element SB2. The conductive nanoparticles 23 penetrate into the n-type silicon layer 15 on the solar cell element SB1 side and are stably held there. Examples of the conductive nanoparticles 23 include, in addition to palladium, metal nanoparticles such as gold, silver, platinum, nickel, aluminum, indium, zinc, and copper, as well as indium oxide and zinc oxide. The size of the conductive nanoparticles 23 is preferably 10-500 nm in diameter, more preferably 10-100 nm, in consideration of good conductivity and suppression of light absorption and scattering by the nanoparticles. The spacing between the conductive nanoparticles 23 can be between two and ten times the average diameter of the conductive nanoparticles 23. This ensures conductivity through the plurality of conductive nanoparticles 23 and also ensures sufficient light transmittance at the joints.

[0024] The shape of the conductive nanoparticles 23 need only ensure conductivity, and may be, for example, not limited to a spherical shape but also a columnar shape such as a square pillar or a cylinder, a thin wire shape, a fiber shape, an irregular shape, etc. The shape of the conductive nanoparticles 23 can be controlled, for example, by adjusting the composition of the block copolymer described below. In the multi-junction solar cell 1 of this embodiment, the conductive nanoparticles 23 penetrate into the n-type silicon layer 15 on the solar cell element SB1 side, thereby improving the electrical connection between the solar cell element SB1 and the solar cell element SB2 and enabling a stable junction structure with excellent junction strength. Therefore, this embodiment makes it possible to provide a solar cell that combines both junction strength and good cell characteristics.

[0025] (Method of joining solar cell element SB1 and solar cell element SB2) The method for joining solar cell element SB1 and solar cell element SB2 is described below with reference to Figures 2 and 3. First, a microarray pattern of conductive nanoparticles 23 is prepared using a block copolymer according to the standard smart stack technique. The pattern is then treated with a chloride solution to precipitate the conductive nanoparticles 23, and then treated with argon plasma to form the conductive nanoparticle 23 array as shown in Figure 2(B). An example is shown below. A thin film (not shown) made of a block copolymer is formed on the surface (surface of the n-type silicon layer 15) of the solar cell element SB1, which is one of the objects to be joined. Specifically, a block copolymer made of polystyrene, which is a hydrophobic portion, and poly-2-vinylpyridine, which is a hydrophilic portion, dissolved in an organic solvent such as toluene or orthoxylene is applied to the surface of the n-type silicon layer 15 using a spin coating method or a dip coating method. As a result, poly-2-vinylpyridine blocks are patterned on the surface of the n-type silicon layer 15 due to phase separation of the block copolymer. In other words, hydrophilic domain regions are formed on the surface of the n-type silicon layer 15. Next, the solar cell element SB1 is immersed in an aqueous solution in which a metal ion salt, typically Na2PdCl4, is dissolved. As a result, metal ions (Pd 2+ ) can be incorporated into the pattern consisting of poly-2-vinylpyridine blocks. 2+ ) is selectively deposited in the hydrophilic domain region described above. After thorough rinsing, the solar cell element SB1 is subjected to a block copolymer removal process and metal ion reduction process, for example, using argon plasma. As a result, a regular array of conductive nanoparticles 23 can be formed while maintaining the pattern (Figure 2(B)). The shape of the conductive nanoparticles 23 can be controlled by changing the polymerization degree of the block copolymer. For example, when the polymerization degree is set to polystyrene:poly-2-vinylpyridine = 133,000:132,000, the diameter of the conductive nanoparticles is 50 nm. However, when the poly-2-vinylpyridine is reduced to polystyrene:poly-2-vinylpyridine = 135,000:53,000, the diameter of the conductive nanoparticles can be controlled to a small size of 25 nm.

[0026] Next, the entire solar cell element SB1 is immersed in an etching solution (e.g., a hydrogen peroxide (H2O2) / hydrogen fluoride (HF) solution). This selectively erodes (or etches) only the areas where the conductive nanoparticles 23 are in contact. As shown in Figure 2(C), the conductive nanoparticles 23 sink, penetrate the oxidized region 25, and penetrate into the n-type silicon layer 15. Instead of immersion, the etching solution can be dripped or applied to the surface of the solar cell element SB1. This technique is called metal-assisted chemical etching (MACE), and its principle is shown in Figure 3. Note that Figure 3 is a schematic diagram simply for explaining the principle. As shown in equations (1) and (2), electrons produced by the oxidation reaction of silicon (Si) and holes produced by the decomposition of hydrogen peroxide react through the conductive metal nanoparticles 23, promoting the oxidation reaction and forming the etched region 27. Then, as shown in equation (3), silicon dioxide reacts with hydrogen fluoride to form SiF6, an etching residue, which is then removed. H2O2+2H + →2H2O+2h + (1) Si+2H2O → SiO2+4H + +4e - (2) SiO2+2HF2 - +2HF → SiF6 2- +2H2O (3)

[0027] Thereafter, the other solar cell element SB2 to be joined is placed on the solar cell element SB1 on which the conductive nanoparticles 23 are arranged, and then subjected to an appropriate pressure treatment (for example, 5 N / cm 2 ) to bond the solar cell element SB1 and the solar cell element SB2 (FIG. 2(D)). In this way, the conductive nanoparticles 23 realize bonding between the solar cell element SB1 and the solar cell element SB2.

[0028] When using conventional smart stack technology to fabricate multi-junction solar cells consisting of silicon cells and GaAs cells, the presence of oxidized regions on the surface of the silicon cells increases the junction resistance, particularly between the cells, which affects the solar cell characteristics, as shown in Non-Patent Documents 2-3. However, according to this embodiment, the conductive nanoparticles 23 penetrate through the oxidized region 25 and penetrate into the underlying low-resistance n-type silicon layer 15, and are therefore not affected by the oxidized region 25, thereby improving the junction resistance between cells. In particular, according to the MACE method, only the region in contact with the conductive nanoparticles 23 is selectively eroded, making it possible to easily cause the conductive nanoparticles 23 to penetrate into the n-type silicon layer 15. As a result, a stable junction structure with excellent junction strength is formed due to the so-called anchor effect of the conductive nanoparticles 23. This can improve the reliability of semiconductor devices and solar cells.

[0029] Furthermore, in the MACE method (also known as MACE processing), the sinking height of the conductive nanoparticles 23 can be adjusted by controlling the etching solution treatment time (immersion time), solution volume, etching solution composition (e.g., the molar ratio of H2O2 to HF), and etching solution concentration. For example, extending the treatment time or increasing the concentration of the H2O2 / HF solution increases the extent (depth) of the etched region 27. While the oxidized region 25 is partially etched using the H2O2 / HF solution alone, the MACE effect selectively and rapidly etched regions directly beneath conductive nanoparticles such as Pd. The conductive nanoparticles 23 then completely penetrate the oxidized region 25. It is desirable for the conductive nanoparticles 23 to be positioned at a depth of 5 nm or more within the n-type silicon layer 15.

[0030] In smart stack technology, the height of the conductive nanoparticles determines the presence of air or adhesive at the junction interface. Here, the low refractive index of air and adhesive causes optical loss due to light reflection at the junction interface. However, by embedding the conductive nanoparticles 23 deep into the silicon cell, the effective thickness of the air and adhesive can be reduced, thereby reducing optical loss. For example, if the distance H between the solar cell elements SB1 and SB2 (see Figure 1, also referred to as the junction gap) is 20 nm or less, preferably 10 nm or less, the optical reflection loss can be reduced to 10% or less. This distance H corresponds to the exposed height of the conductive nanoparticles 23, and controlling this exposed height can reduce optical loss. The distance H can also be effectively controlled by changing the shape, size, and density of the conductive nanoparticles 23. Furthermore, the deeper the conductive nanoparticles 23 are sunk, the more stably they are held in the silicon layer. Therefore, it is preferable to control the distance H so that the conductive nanoparticles 23 are sunk by more than half of their total height. Furthermore, it is better for the interval H to be as close to 0 (zero) as possible, and it is also possible to set it to 0 (zero).

[0031] (Embodiment 2) Figure 4 shows a configuration diagram of a semiconductor device (multi-junction solar cell) according to another embodiment. While the multi-junction solar cell 1 shown in Figure 1 is a solar cell configured with two junctions—a silicon cell and a GaAs cell—the junction structure can also be applied to solar cells with three or more junctions. The multi-junction solar cell 3 in Figure 4 includes a bottom cell solar cell element SB3, a middle cell solar cell element SB4, and a top cell solar cell element SB5. Solar cell element SB3 is configured with a silicon cell, solar cell element SB4 is configured with a GaAs cell, and solar cell element SB5 is configured with an InGaP cell. Specifically, solar cell element SB4 and solar cell element SB5 are two-junction elements of InGaP and GaAs. Solar cell element SB3 is a so-called TOPCon (Tunnel Oxide Passivated Contact) silicon cell, which is a silicon cell characterized by high efficiency and reduced current loss, with a silicon layer (amorphous or polycrystalline silicon) formed as a contact layer with a thin oxide layer interposed between them.

[0032] Solar cell element SB3 has a p-type silicon layer (amorphous or polycrystalline silicon) 30 on which a p-type electrode 31 made of, for example, an aluminum film or a silver film is formed, an SiOx tunnel layer 32 formed on the p-type silicon layer 30, a p-type silicon substrate 33 serving as a light absorption layer, and an n-type silicon layer (amorphous or polycrystalline silicon) 35 formed on the p-type silicon substrate 33. Also, as in the multijunction solar cell 1 (FIG. 1), an oxidized region 25 of about 10 nm is formed on the entire surface or part of the surface of the n-type silicon layer 35. Solar cell element SB3 is configured in this manner.

[0033] The solar cell element SB3 is fabricated by the following method: a thin-film tunnel layer (SiOx tunnel layer 32) made of SiOx oxide film is formed on both sides of a p-type silicon substrate 33 whose surface has been cleaned, then conductive polycrystalline or amorphous silicon layers (p-type silicon layer 30, n-type silicon layer 35) are formed on both sides, and finally a silver or aluminum film is formed on the back surface as a p-type electrode 31.

[0034] The solar cell element SB4 has a p-type GaAs layer 37 that functions as a contact layer, a p-type GaAs layer 39 that functions as a light absorption layer formed on the p-type GaAs layer, and an n-type GaAs layer 41 that is formed on the p-type GaAs layer 39. In this way, the solar cell element SB4 is configured.

[0035] Solar cell element SB5 also has a p-type InGaP layer 43 that functions as a light absorption layer, an n-type InGaP layer 45 formed on the p-type InGaP layer 43, and an n-type electrode (e.g., an AuGeNi / Au or Ti / Au alloy electrode) 47 formed on the n-type InGaP layer 45. Thus, solar cell element SB5 is configured. Here, solar cell element SB4 and solar cell element SB5 are formed on a single semiconductor chip, and solar cell element SB4 and solar cell element SB5 are joined and electrically connected in series by a tunnel layer 49 formed on the semiconductor chip. For example, the tunnel layer is made of a degenerated semiconductor layer sandwiched between the n-type GaAs layer 41 of solar cell element SB4 and the p-type InGaP layer 43 of solar cell element SB5. This electrically connects the n-type GaAs layer 41 of solar cell element SB4 and the p-type InGaP layer 43 of solar cell element SB5.

[0036] The solar cell elements SB4 and SB5 are fabricated using a standard process: after epitaxial growth on a GaAs substrate whose surface has been cleaned, the stacked structure of the solar cell elements SB4 and SB5 is separated from the GaAs substrate by the ELO method.

[0037] On the other hand, the solar cell element SB3 cannot be formed simultaneously by crystal growth because its crystal structure is fundamentally different from that of the solar cell elements SB4 and SB5. For this reason, the solar cell element SB3 is formed on a semiconductor substrate separate from the semiconductor substrate on which the solar cell elements SB4 and SB5 are formed.

[0038] 2, an array of conductive nanoparticles 23 is formed on solar cell element SB3, and then only the contacting portions of the conductive nanoparticles 23 are selectively eroded. The semiconductor chip on which solar cell element SB3 is formed and the semiconductor chip on which solar cell elements SB4 and SB5 are formed are then superimposed and subjected to a pressure treatment. As a result, solar cell elements SB3, SB4, and SB5 are mechanically bonded and electrically connected by the conductive nanoparticles 23. Here, solar cell elements SB3, SB4, and SB5 have different bandgaps, and as described in embodiment 1, an electromotive force is generated in each solar cell element, and the sum of the electromotive forces is generated in the multi-junction solar cell 3 as a whole. This embodiment can also achieve the same effects as embodiment 1.

[0039] (Embodiment 3) FIG. 5 shows a structural diagram of a semiconductor device (multi-junction solar cell) according to another embodiment. Multi-junction solar cell 5 includes a bottom cell solar cell element SB1, a middle cell solar cell element SB4, and a top cell solar cell element SB5. Solar cell element SB1 is a silicon cell, solar cell element SB4 is a GaAs cell, and solar cell element SB5 is an InGaP cell. Specifically, solar cell element SB1 has the same configuration as solar cell element SB1 of multi-junction solar cell 1 in FIG. 1, and solar cell elements SB4 and SB5 have the same configurations as solar cell elements SB4 and SB5 of multi-junction solar cell 3 in FIG. 4, and therefore a description thereof will be omitted. The fabrication of solar cell element SB1, solar cell element SB4, and solar cell element SB5, the arrangement of conductive nanoparticles 23 on solar cell element SB1 and the erosion of the contact portions of the conductive nanoparticles 23, and the bonding of solar cell element SB1 with solar cell element SB4 and solar cell element SB5 are performed in the same manner as in the above-described embodiment. This also applies to the following embodiments. This embodiment can also achieve the same effects as embodiment 1 and the like. Here, the solar cell element SB1 is what is called back surface field (BSF) type silicon, and is a silicon cell that can achieve high efficiency by making the side of the p-type silicon substrate 13 closer to the p-type electrode 11 a highly concentrated p-type layer, thereby reducing electron loss near the electrode.

[0040] (Embodiment 4) 6 shows a configuration diagram of a semiconductor device (multi-junction solar cell) according to another embodiment. Multi-junction solar cell 7 has a bottom cell solar cell element SB6, a middle cell solar cell element SB4, and a top cell solar cell element SB5, with solar cell element SB6 being a silicon cell, solar cell element SB4 being a GaAs cell, and solar cell element SB5 being an InGaP cell.

[0041] Solar cell element SB6 has a p-type amorphous silicon layer 53 on which a p-type electrode 51 made of, for example, an aluminum film or a silver film is formed, an i-type amorphous silicon layer 55 formed on the p-type amorphous silicon layer 53, an n-type silicon substrate 57 serving as a light absorption layer formed on the i-type amorphous silicon layer 55, the i-type amorphous silicon layer 55 formed on the n-type silicon substrate 57, and an n-type amorphous silicon layer 61 formed on the i-type amorphous silicon layer 55. Also, similar to the multijunction solar cell 1 (FIG. 1), an oxidized region 25 is formed on the entire or part of the surface of the n-type amorphous silicon layer 61. Solar cell element SB6 is configured in this manner.

[0042] Solar cell element SB6 is fabricated by the following method: i-type amorphous silicon layers 55 are formed on both sides of n-type silicon substrate 57 whose surface has been cleaned, then conductive amorphous silicon layers (p-type amorphous silicon layer 53, n-type amorphous silicon layer 61) are formed on both sides, and finally a silver or aluminum film is formed on the back surface as p-type electrode 51.

[0043] Solar cell element SB4 and solar cell element SB5 have the same configuration as solar cell element SB4 and solar cell element SB5 of multi-junction solar cells 3 and 5 in Figures 4 and 5, and therefore a description thereof will be omitted. This embodiment can also achieve the same effects as embodiment 1, etc. Solar cell element SB6 is what is called a heterojunction type (HIT: Heterojunction with Intrinsic Thin-layer) silicon cell or heterojunction junction type (HJT: Hetero Junction Technology) silicon cell, and is a silicon cell in which current loss is reduced and high efficiency is achieved by forming p-type amorphous silicon layer 53 and n-type amorphous silicon layer 61, which are cell contact layers, via i-type amorphous silicon layer 55, etc. The constituent materials of the solar cell elements that will become the top and middle cells are not limited to GaAs, InGaP, etc., but may also be AlGaAs, InGaAsP, AlInGaP, InGaAs, chalcogenides (Cu(In,Ga)Se2(CIGS)), perovskite, organic materials, etc. The silicon cells that will become the bottom cells also have a wide variety of structures, but they all have in common that an oxidized region is formed in the top silicon layer that forms the junction surface, and it is clear that this technology can be applied. [Example]

[0044] The multi-junction solar cell 3 shown in FIG. 4 was fabricated by the method described below. First, the solar cell element SB3 was produced by the following method. The surface of the p-type silicon substrate 33 was treated with a dilute hydrofluoric acid etchant, and then a thin SiOx tunnel layer 32 was formed on both sides using a chemical oxidation method to a thickness of approximately 1 nm. Here, the oxide film was formed by immersing the p-type silicon substrate 33 in a concentrated nitric acid solution, but oxidation can also be achieved using a CVD method or other method. Next, a p-type silicon layer (amorphous) 30 and an n-type silicon (amorphous) layer 35 were formed to a thickness of 100 nm using a chemical vapor deposition (CVD) method, and then annealed at 800°C to polycrystallize the amorphous layer. Finally, an aluminum film to become the p-type electrode 31 was formed to a thickness of approximately 500 nm using a sputtering method. The solar cell element SB3 was processed to a diameter of 4 inches and a thickness of 300 μm, and finally cut to a size of approximately 1 cm square to form a bottom cell. Next, solar cell elements SB4 and SB5 were fabricated as follows. A p-type GaAs substrate, the surface of which had been cleaned with an ethanol solution, was used to sequentially form a p-type GaAs layer 37, a p-type GaAs layer 39, an n-type GaAs layer 41, a tunnel layer 49, a p-type InGaP layer 43, and an n-type InGaP layer 45, with a release layer interposed between them, using molecular beam epitaxy (MBE) in a Riber Compact 21 solid source MBE system at a growth temperature of 550°C. Subsequently, an n-type electrode 47 made of AuGeNi / Au was formed using an electron beam evaporation system (Sanyu Electronics SVC-700LEB / 4G, deposition rate: 2–4 Å / s). The release layer, a 50 nm AlAs layer, was used to separate the layers from the substrate during the ELO process. The solar cell elements SB4 and SB5 were processed to a diameter of 2 inches and a thickness of approximately 350 μm (the GaAs substrate was approximately 340 μm), and were finally cut into 4 mm squares for use as top cells. The cut top cells were then immersed in an HF solution (solution concentration 20 mass%) for 12 hours and peeled from the GaAs substrate to obtain elements consisting of solar cells SB4 and SB5. The total thickness of the peeled solar cell elements SB4 and SB5 was approximately 4 μm.

[0045] Next, an array of conductive nanoparticles 23 was formed on solar cell element SB3 using the following method. Pd nanoparticles as conductive nanoparticles 23 were aligned on solar cell element SB3 by forming a thin film of polystyrene-poly-2-vinylpyridine as a block copolymer and using this as a template. Specifically, a 0.5 wt% ortho-xylene solution of polystyrene-poly-2-vinylpyridine (polystyrene molecular weight: 133,000 g / mol, poly-2-vinylpyridine molecular weight: 132,000 g / mol) with a total molecular weight of 265,000 g / mol was spin-coated onto solar cell element SB3 to form a thin film. Next, solar cell element SB3 was immersed in a 1 mM Na2PdCl4 aqueous solution for 2 minutes. After rinsing with water, solar cell element SB3 was subjected to argon plasma treatment (using a Diener plasma device (Femto) at 50 W for 2 minutes) to align Pd nanoparticles with an average size (diameter) of 50 nm that were not covered with organic molecules. The average spacing between palladium nanoparticles in this arrangement was 100 nm.

[0046] Next, solar cell element SB3 was subjected to MACE treatment, which selectively eroded only the areas where the Pd nanoparticles were in contact, causing the Pd nanoparticles to sink (see Figure 2(C)). This treatment was performed by immersing solar cell element SB3 with the Pd nanoparticles in an etchant (25°C) using an HO / HF solution (30 mass% HO solution and 50 mass% HF solution, with a solution ratio of HO:HF:HO = 1:1:10) for 1 minute. After that, the entire solar cell element SB3 was washed with water to remove the etchant. Next, the solar cell element SB4 and the solar cell element SB5 were stacked on the solar cell element SB3 on which the Pd nanoparticles were arranged, and then a weight (5 N / cm 2 ) was carried out at room temperature for about 2 hours to bond the solar cell elements SB3, SB4 and SB5 together. This solar cell was designated as Sample A.

[0047] For comparison, multi-junction solar cell 8 shown in FIG. 7 and multi-junction solar cell 9 shown in FIG. 8 were also fabricated. Multi-junction solar cell 8 (FIG. 7) was fabricated by forming an array of conductive nanoparticles 23 (Pd nanoparticles) (see FIG. 2(B)), and then stacking solar cell element SB4 and solar cell element SB5 on solar cell element SB3 on which conductive nanoparticles 23 had been arranged, without performing the MACE treatment (FIG. 2(C)). Then, pressure treatment (5 N / cm 2 ) to join solar cell element SB3, solar cell element SB4, and solar cell element SB5 together. Other conditions were the same as those used in the method for producing multi-junction solar cell 3. This solar cell was designated sample B.

[0048] Multi-junction solar cell 9 (Fig. 8) was fabricated by the following method. As mentioned above, the presence of oxidized regions on the surface of silicon cells increases the junction resistance between cells, affecting the solar cell characteristics. Multi-junction solar cell 9 was fabricated by removing the oxidized regions. First, solar cell element SB3, solar cell element SB4, and solar cell element SB5 were fabricated using the same method as for multijunction solar cell 3. Next, before forming the array of conductive nanoparticles 23 (Pd nanoparticles), the oxidized region 25 formed on the surface of solar cell element SB3 was partially or completely removed using a buffered HF solution (a mixture of hydrofluoric acid and ammonium fluoride, also referred to as a BHF solution) (solar cell element SB7). Specifically, solar cell element SB3 was immersed in a BHF solution (BHF63, manufactured by Daikin Industries, Ltd.) at 25°C for 1 minute (BHF treatment).

[0049] After that, the solar cell was washed with water, and an arrangement of conductive nanoparticles 23 was formed in the same manner as in the case of the multi-junction solar cell 3 (see FIG. 2(B)). Then, without carrying out the MACE treatment, the solar cell element SB4 and the solar cell element SB5 were stacked on the solar cell element SB7 on which the conductive nanoparticles 23 were arranged, and then pressure treatment (5 N / cm 2 ) was performed to join the solar cell elements SB7, SB4, and SB5 together. This solar cell was designated as sample C.

[0050] The current-voltage characteristics (IV curve) of the solar cell sample AC fabricated by the above method are shown in Figure 9. This measurement was performed using an IV simulator (Model 38A042Y, manufactured by Bunkoukeiki Co., Ltd.) and irradiating the solar cell with simulated sunlight at an AM (air mass) of 1.5G. In addition, the short-circuit current density (Jsc), open-circuit voltage (V), fill factor (%), and power generation efficiency (%) of Sample AC were extracted from the current-voltage characteristics in FIG. 9 and are shown in Table 1. [Table 1]

[0051] The solar cells of Sample A and Sample C showed good cell performance. In particular, the solar cell of Sample A showed excellent cell characteristics in all items. Although the solar cell of Sample C has undergone BHF treatment, it is thought that some oxidized regions remain, which may have deteriorated its characteristics. On the other hand, in the solar cell of Sample A, the Pd nanoparticles penetrate the oxidized regions due to the MACE treatment and penetrate into the n-type silicon layer 35, resulting in good conductivity. In this way, the solar cell of Sample A, in particular, was free from the influence of the oxidized regions, resulting in a sufficiently low junction resistance and a high power generation efficiency of over 30%. The short-circuit current was also 1 mA / cm compared to the other samples. 2 The increase was due to the MACE method reducing the exposed height of the Pd nanoparticles, and the distance (H) between solar cell element SB3 and solar cell element SB4 becoming 10 nm or less, which reduced the reflection loss at the junction interface. This is thought to have increased the photocurrent of solar cell element SB3 in sample A, improving the current matching level as a multi-junction cell. On the other hand, in the solar cell of sample B, the resistance of the junction increased due to the influence of the oxidized region 25, resulting in an S-shaped curve.

[0052] Figure 10 shows atomic force microscope (AFM) images of the Si surface of sample A after MACE treatment. Figure 10(A) is an observation from the top, and Figure 10(B) is a three-dimensional view from the oblique direction. Figure 11(A) shows an AFM image (left) and an optical microscope image (right) of the Si surface of sample B after Pd nanoparticle arrangement, and Figure 11(B) shows an AFM image (left) and an optical microscope image (right) of the Si surface of sample C after Pd nanoparticle arrangement. Atomic force microscope observations were performed using a microscope (Shimadzu Corporation, SPM9600).

[0053] In the solar cell of Sample A (Figure 10), the arrangement of the conductive nanoparticles 23 (Pd nanoparticles) was clear, and although some Pd nanoparticle precipitation was observed due to the MACE treatment (part X), there was no significant abnormal precipitation. In contrast, in the solar cell of Sample C (Figure 11(B)), the BHF treatment caused irregularities and surface defects in the silicon layer, which hindered the uniform arrangement of the conductive nanoparticles 23 (Pd nanoparticles). In particular, the surface defects induced abnormal precipitation of Pd nanoparticles exceeding 100 nm in height (part Y). Here, since the MACE method (Sample A) performs the treatment after the arrangement of the conductive nanoparticles 23, ideally, the areas without the conductive nanoparticles 23 are not eroded, and only the areas directly below the conductive nanoparticles 23 are uniformly eroded and sink. Therefore, the overall smoothness of the conductive nanoparticles 23 is maintained, and the degree of irregularity is smaller than in the case of BHF treatment (Sample C). In the solar cell of sample B (FIG. 11(A)), no surface treatment such as BHF treatment or MACE treatment was performed, and therefore the arrangement of the conductive nanoparticles 23 (Pd nanoparticles) was uniform.

[0054] Next, the solar cells of sample AC were subjected to external observation and nitrogen blow observation from the viewpoint of comparing the bonding strength and stability. First, the external observation was performed using a stereo microscope. The nitrogen blow observation was performed using the following method. That is, a thin-tipped glass pipe (diameter 1 mm) was prepared and nitrogen gas (pressure 5 kg / cm ) was blown into it. 2) was sprayed onto the joint of each sample from a glass tube for approximately 5 seconds. Table 2 shows the evaluation results of the solar cell of Sample AC. Note that the solar cell performance in Table 2 was judged based on the results in Table 1. [Table 2]

[0055] Figures 12(A)-(C) show photographs (top view) of the solar cells of Samples A and C. No particular abnormalities were observed in the solar cells of Sample A (Figure 12(A)) and Sample B (Figure 12(B)). However, in the solar cell of Sample C, as shown in Figure 12(C), there were visible voids and air intrusions in the non-bonded areas. Furthermore, as shown in Figure 13, observations using nitrogen blowing revealed no particular abnormalities in the solar cells of Sample A (Figure 13(A)) and Sample B (Figure 13(B)). However, the solar cell of Sample C (Figure 13(C)) suffered damage such as scattering and peeling. Because cell bonding is achieved by Pd nanoparticles, uniform nanoparticle height improves bonding strength. However, in Sample C, abnormal precipitation of Pd nanoparticles occurred, as shown in Figure 11(B), which is thought to have reduced bonding strength.

[0056] Figure 14 shows a TEM (transmission electron microscope) image (A) of sample A and the results of analysis by energy dispersive X-ray spectroscopy (B), and Figure 15 shows a TEM image (A) of sample B and the results of analysis by energy dispersive X-ray spectroscopy (B). The TEM image was measured using a transmission electron microscope (Hitachi High-Technologies Corporation, H-9500, accelerating voltage 200 kV). The energy dispersive X-ray spectroscopy was measured using an electron microscope (JEOL Ltd., JEM-ARM200F, accelerating voltage 200 kV). As shown in Figure 14, when Pd nanoparticles are observed under magnification with a TEM, they form a domain structure in which Pd nanoparticles of a few nm in size aggregate. In the solar cell of Sample A, it can be seen that the Pd nanoparticles that make up the domains have penetrated (10 nm or more) into the n-type silicon layer (polycrystalline) below the junction gap (8 nm). Note that the oxidized regions where no surrounding Pd nanoparticles exist are directly etched by the HF:H2O2 solution during the MACE process, but are thought to remain as a thin film microscopically.

[0057] Furthermore, in the energy-dispersive X-ray spectroscopy data for Sample A, Pd signals were observed even in the n-type silicon layer (polycrystalline), confirming the penetration of Pd nanoparticles. In contrast, in the solar cell for Sample B, an oxidized region approximately 10 nm thick was present on the silicon cell surface, and Pd nanoparticles were observed only in the junction gap without penetrating the n-type silicon layer (polycrystalline). Unlike Sample A, the Pd signal from the energy-dispersive X-ray spectroscopy was also observed only in the junction gap. Although not shown, in Sample C, the oxidized region was removed by BHF treatment, but Pd nanoparticles were observed only in the junction gap. In Sample A, the Pd nanoparticles penetrated into the n-type silicon layer (polycrystalline), reducing the junction resistance by not being affected by the oxidized region. Furthermore, the so-called anchor effect formed a junction structure with excellent junction strength. In Sample B, the oxidized region on the surface of the silicon semiconductor increased junction resistance and degraded cell performance. In sample C, the oxidized regions on the silicon surface were removed by BHF treatment, but the abnormal precipitation of Pd due to the surface defects described above caused a deterioration in bonding strength. Therefore, according to this example, it is possible to easily provide a highly efficient multi-junction solar cell with a junction structure that has excellent bonding strength and cell performance, thereby improving the reliability of the solar cell.

[0058] In the above-described embodiment, the conductive nanoparticles 23 are sunk into the silicon layer without removing the oxidized region, but it is also possible to add a step of removing the oxidized region and then perform a step of sinking the conductive nanoparticles 23. In other words, the presence or absence of an oxidized region is not particularly limited, and as long as the conductive nanoparticles 23 are embedded in the silicon layer, the same effects as those of the above-described embodiment can be achieved.

[0059] In addition, in the above-described embodiment, a multi-junction solar cell is given as an example of a semiconductor device, but the present invention can also be applied to, for example, an optical integrated device or a silicon photonics device in which a Si semiconductor element and multiple semiconductor elements are junctioned in series. [Explanation of symbols]

[0060] 1, 3, 5, 7, 8, 9 multijunction solar cells 11 p-type electrode 13 p-type silicon substrate 15 n-type silicon layer 17 p-type GaAs layer 19 n-type GaAs layer 21 n-type electrode 23 Conductive nanoparticles 25 Oxidation Region 27 Etching area 30 p-type silicon layer 31 p-type electrode 32 SiOx tunnel layer 33 p-type silicon substrate 35 n-type silicon layer 37 p-type GaAs layer 39 p-type GaAs layer 41 n-type GaAs layer 43 p-type InGaP layer 45 n-type InGaP layer 47 n-type electrode 49 Tunnel Layer 51 p-type electrode 53 p-type amorphous silicon layer 55 i-type amorphous silicon layer 57 n-type silicon substrate 61 n-type amorphous silicon layer

Claims

1. a first semiconductor element including a silicon layer and having a first bonding surface; a second semiconductor element having a second bonding surface opposite to the first bonding surface; a plurality of conductive nanoparticles located between the first bonding surface and the second bonding surface, electrically connecting the first semiconductor element and the second semiconductor element; A semiconductor device, wherein the silicon layer has the same number of eroded portions where the surface is eroded as the conductive nanoparticles, and each conductive nanoparticle penetrates into each eroded portion in the silicon layer.

2. 2. The semiconductor device according to claim 1, wherein each of said plurality of conductive nanoparticles contains any one of palladium, gold, silver, platinum, nickel, aluminum, indium, indium oxide, zinc, zinc oxide, and copper.

3. 2. The semiconductor device according to claim 1, wherein the exposed height of said plurality of conductive nanoparticles is 20 nm or less, and the height of said nanoparticles penetrating into each eroded portion in said silicon layer is 5 nm or more.

4. 4. A solar cell comprising the semiconductor device according to claim 1, wherein the silicon layer of the first semiconductor element includes a semiconductor material of crystalline silicon or amorphous silicon, and the second semiconductor element includes one or more semiconductor materials selected from the group consisting of GaAs, AlGaAs, InGaP, AlGaInP, InGaAsP, InGaAs, chalcogenide-based, perovskite-based, and organic-based.

5. (a) providing a first semiconductor element including a silicon layer and having a first bonding surface; (b) providing a second semiconductor element having a second bonding surface; (c) disposing a plurality of conductive nanoparticles on the first bonding surface; (d) after step (c), embedding a plurality of conductive nanoparticles into the silicon layer; (e) after the step (d), pressing the second bonding surface against the first bonding surface with the plurality of conductive nanoparticles interposed therebetween; Equipped with In the step (d), the conductive nanoparticles are embedded in the silicon layer by a metal-assisted chemical etching method.

6. The method for manufacturing a semiconductor device according to claim 5, wherein the plurality of conductive nanoparticles are particles of any one of palladium, gold, silver, platinum, nickel, aluminum, indium, indium oxide, zinc, zinc oxide, and copper.

7. The method for manufacturing a semiconductor device according to claim 5 , wherein the exposed height of the plurality of conductive nanoparticles is 20 nm or less, and the height of the nanoparticles embedded in the silicon layer is 5 nm or more.

8. A method for manufacturing a solar cell, comprising the method for manufacturing a semiconductor device according to any one of claims 5 to 7, A method for manufacturing a solar cell, wherein a semiconductor material of crystalline silicon or amorphous silicon is used as the silicon layer of the first semiconductor element, and one or more semiconductor materials selected from the group consisting of GaAs, AlGaAs, InGaP, AlGaInP, InGaAsP, InGaAs, chalcogenide-based, perovskite-based, and organic-based semiconductor materials are used as the second semiconductor element.

Images