Method for manufacturing a solid oxide fuel cell

Abstract

To provide a thin film type solid oxide fuel cell having a stress relaxation structure of a membrane edge.SOLUTION: A solid oxide fuel cell includes: a silicon substrate; an electrolyte film formed on a first surface of the silicon substrate; a first electrode formed on at least part of the first surface of the electrolyte film; a recess portion formed so as to expose, from a second surface of the silicon substrate that is an opposite surface of the first surface, part of the second surface that opposes the first electrode that is an opposite surface of the first surface of the electrolyte film; and a second electrode formed on the second surface on which at least the electrolyte membrane is exposed. The silicon substrate includes a porous portion formed by porosity at least in the vicinity of an edge of the recess portion.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a thin-film solid oxide fuel cell having a stress relaxation structure using porous silicon and a method for manufacturing the same.

Background Art

[0002] A solid oxide fuel cell (SOFC) is a type of high-efficiency energy conversion device that converts chemical energy into electrical energy, and is a fuel cell that uses a solid oxide film as an electrolyte.

[0003] As the electrolyte used in the electrolyte membrane of SOFC, YSZ (Yttria Stabilized Zirconia) is mainly used. A thin-film (Thinfilm) SOFC manufactured through a Micro-electro-mechanical System (MEMS) process has a membrane structure of backside etching that forms an electrolyte membrane and electrodes in a Free Standing manner on a silicon substrate (for example, see Patent Document 1).

[0004] That is, after forming an electrolyte thin film on a silicon substrate, after exposing the lower part of the electrolyte thin film through backside etching, electrodes are formed on the upper and lower sides of the electrolyte thin film so that reactive gases can reach both sides of the electrolyte.

[0005] In this way, the thin-film SOFC on the MEMS substrate has the advantage of minimizing ohmic loss due to ion conduction in the electrolyte by forming the membrane and electrodes with thin films and improving the operating performance at low temperatures. However, there is a disadvantage that stress concentrates near the edge during operation and the cells located in this vicinity are damaged (for example, see Patent Document 2).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] The present invention has been made in view of the above, and an object thereof is to provide a thin-film solid oxide fuel cell having a stress relaxation structure at the membrane edge.

[0008] Another object is to provide a method for manufacturing a thin-film solid oxide fuel cell having a stress relaxation structure at the membrane edge.

[0009] The problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those having ordinary knowledge in the technical field from the following description. MEANS FOR SOLVING THE PROBLEM

[0010] In at least one embodiment of the present invention, there is provided a solid oxide fuel cell including a silicon substrate, an electrolyte film formed on a first surface of the silicon substrate, a first electrode formed on at least a part of a first surface of the electrolyte film, a recess formed so that a part facing the first electrode on a second surface, which is the opposite surface of the first surface of the silicon substrate, is exposed from the second surface, and a second electrode formed on at least the exposed second surface of the electrolyte film, wherein the silicon substrate includes a porous portion formed porously at least near an edge of the recess.

[0011] In at least one embodiment of the present invention, a step of depositing a dielectric film on the first surface of a silicon substrate and on the second surface which is the opposite surface of the first surface, a step of removing the dielectric film deposited on the second surface by a predetermined pattern, a step of forming an electrolyte film on the first surface of the dielectric film deposited on the first surface, a step of etching the portion of the second surface where the dielectric film has been removed so as to form a recess portion where the dielectric film deposited on the first surface is exposed, a step of removing the dielectric film deposited on the first surface exposed through the recess portion and the dielectric film remaining on the second surface, a step of forming at least the vicinity of the edge of the recess portion of the silicon substrate to be porous, a step of forming a first electrode on at least a part of the first surface of the electrolyte film, and a step of forming a second electrode on the second surface which is the opposite surface of the first surface of the electrolyte film exposed by removing the dielectric film deposited on the first surface exposed through the recess portion are provided, and a method for manufacturing a solid oxide fuel cell is provided.

[0012] In at least one embodiment of the present invention, a solid oxide fuel cell is provided which includes a porous silicon substrate, an electrolyte film formed on the first surface of the porous silicon substrate, a first electrode formed on at least a part of the first surface of the electrolyte film, a recess portion formed such that a part of the second surface which is the opposite surface of the first surface of the porous silicon substrate and faces the first electrode on the second surface which is the opposite surface of the first surface of the electrolyte film is exposed, and a second electrode formed on at least the exposed second surface of the electrolyte film.

[0013] In at least one embodiment of the present invention, there are steps of depositing a dielectric film on each of a first surface of a single-crystal silicon substrate and a second surface which is the opposite surface of the first surface, removing the dielectric film deposited on the second surface by a predetermined pattern, forming an electrolyte film on a first surface of the dielectric film deposited on the first surface, etching a portion of the second surface where the dielectric film has been removed so as to form a recess portion where the dielectric film deposited on the first surface is exposed, removing the dielectric film deposited on the first surface exposed through the recess portion and the dielectric film remaining on the second surface, forming the silicon substrate to be porous, forming a first electrode on at least a part of a first surface of the electrolyte film, and forming a second electrode on a second surface which is the opposite surface of the first surface of the electrolyte film exposed by removing the dielectric film deposited on the first surface exposed through the recess portion, to provide a method for manufacturing a solid oxide fuel cell.

[0014] Even if each embodiment in this specification is described independently of each other, each embodiment can be combined with each other, and the embodiments by combination are also included in the scope of rights of the present invention.

[0015] The above summary is merely for explanation and is not intended to be limiting in any way. In addition to the above-described modes of explanation, embodiments, and features, additional modes, embodiments, and features should become clear by referring to the drawings and the detailed description.

Advantages of the Invention

[0016] According to at least one embodiment of the present invention, there is an effect that a thin-film solid oxide fuel cell having a stress relaxation structure at the membrane edge can be provided.

[0017] Furthermore, according to at least one embodiment of the present invention, there is an effect that a method for manufacturing a thin-film solid oxide fuel cell having a stress relaxation structure at the membrane edge can be provided.

[0018] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned should be clearly understood by those with ordinary knowledge in the technical field from the following description.

Brief Description of the Drawings

[0019]

Figure 1

Figures 2A - 2G

Embodiments for Carrying Out the Invention

[0020] Hereinafter, with reference to the accompanying drawings, a thin-film solid oxide fuel cell having a stress relaxation structure using porous silicon according to at least one embodiment of the present invention and a manufacturing method thereof will be described in detail.

[0021] FIG. 1 is a side sectional view of a thin-film solid oxide fuel cell 100 according to at least one embodiment of the present invention.

[0022] As shown in FIG. 1, a thin-film solid oxide fuel cell 100 according to at least one embodiment of the present invention includes a silicon substrate 110, an electrolyte film 120 formed on a first surface (the upper surface in the example shown in FIG. 1) of the silicon substrate 110, a first electrode 130 formed on at least a part of the first surface of the electrolyte film 120, a recess portion 140 formed so that a part facing the first electrode 130 on the second surface (the lower surface in the example shown in FIG. 1), which is the opposite surface of the first surface of the silicon substrate 110, is exposed from the second surface, which is the opposite surface of the first surface of the electrolyte film 120, and a second electrode 150 formed on the second surface of the electrolyte film 120 exposed at least through the recess portion 140.

[0023] The thin-film solid oxide fuel cell 100 according to at least one embodiment of the present invention is a thin-film SOFC based on a MEMS substrate, and has a structure in which a membrane and electrodes are formed of thin films to minimize ohmic loss due to ion conduction in the electrolyte and improve the operating performance at low temperatures.

[0024] In order to solve the problem that stress is concentrated near the edge of the membrane (near the edge of the recess 140 in the membrane) during operation and the cells located in this vicinity are damaged, the thin-film solid oxide fuel cell 100 according to at least one embodiment of the present invention includes a porous portion 160 formed in a porous manner near at least the edge of the recess 140 of the silicon substrate 110.

[0025] Thus, by forming the porous portion 160 formed in a porous manner near at least the edge of the recess 140 of the silicon substrate 110, the stress concentrated near the edge of the membrane (near the edge of the recess 140 in the membrane) can be dispersed.

[0026] FIG. 1 shows an example in which a porous portion 160 formed in a porous manner near the edge of the recess 140 of the silicon substrate 110 is formed to disperse the stress concentrated near the edge of the membrane (near the edge of the recess 140 in the membrane). However, it is also possible to make the entire silicon substrate 110 porous to disperse the stress concentrated near the edge of the membrane (near the edge of the recess 140 in the membrane).

[0027] Therefore, in at least one embodiment of the present invention, the thin-film solid oxide fuel cell 100 includes a porous silicon substrate 110, an electrolyte membrane 120 formed on the first surface of the porous silicon substrate 110, a first electrode 130 formed on at least a part of the first surface of the electrolyte membrane 120, a recess 140 formed so that a part facing the first electrode 130 from the second surface of the porous silicon substrate 110 to the second surface of the electrolyte membrane 120 is exposed, and a second electrode 150 formed on the second surface of the electrolyte membrane 120 exposed through at least the recess 140.

[0028] In at least one embodiment of the present invention, the electrolyte membrane 120 can be formed of an ion-conductive ceramic electrolyte membrane using MEMS processes, and the first electrode 130 and the second electrode 150 can be formed using a porous platinum material.

[0029] In at least one embodiment of the present invention, the electrolyte membrane 120 can be formed of a solid oxygen ion conductor such as yttria-stabilized zirconia (YSZ) or a proton conductor such as yttrium-doped BaZrO3 (BYZ).

[0030] Figures 2A to 2G are schematic diagrams for explaining the manufacturing process of the thin-film solid oxide fuel cell 100 according to at least one embodiment of the present invention.

[0031] As shown in Figure 2A, a dielectric film 111 and a dielectric film 112 are deposited on the first surface (the upper surface in the example shown in Figure 2A) and the second surface (the lower surface in the example shown in Figure 2A), which is the opposite surface of the first surface, of the silicon substrate 110 polished on both sides. Here, SiN can be used for the dielectric film 111 and the dielectric film 112.

[0032] Thereafter, as shown in Figure 2B, the dielectric film 112 deposited on the second surface is removed by a predetermined pattern. That is, after patterning the SiN dielectric film 112 through photolithography using a mask having a predetermined pattern on the dielectric film deposited on the second surface, the dielectric film 112 is removed along the pattern through etching using an appropriate etchant.

[0033] Thereafter, as shown in Figure 2C, an electrolyte membrane 120 is formed on the first surface of the dielectric film 111 deposited on the first surface. The step of removing the dielectric film 112 deposited on the second surface by a predetermined pattern and the step of forming the electrolyte membrane 120 on the first surface of the dielectric film 111 deposited on the first surface may be reversed.

[0034] Thereafter, as shown in FIG. 2D, the portion of the dielectric film 112 on the second surface where it has been removed is etched to form a recess portion 140 such that the dielectric film 111 deposited on the first surface is exposed. At this time, wet etching using a KOH solution can be performed to etch the silicon substrate 110 from below.

[0035] Thereafter, as shown in FIG. 2E, the dielectric film 111 deposited on the first surface exposed through the recess portion 140 and the dielectric film 112 remaining on the second surface are removed.

[0036] Thereafter, as shown in FIG. 2F, at least the vicinity of the edge of the recess portion 140 of the silicon substrate 110 is formed to be porous. At this time, for example, a method of forming porous silicon by immersing single-crystalline silicon in a hydrofluoric acid solution of a predetermined concentration and then performing anodic oxidation can be used.

[0037] Thereafter, as shown in FIG. 2G, a first electrode 130 is formed on at least a part of the first surface of the electrolyte film 120, and a second electrode 150 is formed on the second surface of the electrolyte film 120 exposed by removing the dielectric film 111 deposited on the first surface exposed through the recess portion 140.

[0038] The thin-film type solid oxide fuel cell 100 manufactured in this way is a thin-film type SOFC on a MEMS substrate. By forming the membrane and the electrodes as thin films, ohmic losses due to ion conduction in the electrolyte can be minimized, and it is possible to improve the operating performance at low temperatures.

[0039] In order to prevent stress from concentrating near the edge of the membrane (near the edge of the recess portion 140 in the membrane) during operation and damaging the cells located in this vicinity, by forming a porous portion 160 that is formed to be porous at least in the vicinity of the edge of the recess portion 140 of the silicon substrate 110, the stress concentrated near the edge of the membrane (near the edge of the recess portion 140 in the membrane) can be dispersed.

[0040] In at least one embodiment of the present invention, the electrolyte membrane 120 can be formed as an ion-conductive ceramic electrolyte membrane using MEMS processes, and the first electrode 130 and the second electrode 150 can be formed using a porous platinum material.

[0041] In at least one embodiment of the present invention, the electrolyte membrane 120 can be formed of a solid oxygen ion conductor such as yttria-stabilized zirconia (YSZ) or a proton conductor such as yttrium-doped BaZrO3 (BYZ).

[0042] Figures 2A to 2G show an example in which a porous portion 160 formed in a porous manner is formed near the edge of the recess 140 of the silicon substrate 110 to disperse the stress concentrated near the edge of the membrane (near the edge of the recess 140 in the membrane), but it is also possible to make the entire silicon substrate 110 porous to disperse the stress concentrated near the edge of the membrane (near the edge of the recess 140 in the membrane).

[0043] For example, a dielectric film 111 and a dielectric film 112 are deposited on the first surface and the second surface of a single-crystalline silicon substrate 110 polished on both sides, respectively. Here, SiN can be used for the dielectric film 111 and the dielectric film 112.

[0044] Thereafter, the dielectric film 112 deposited on the second surface is removed by a predetermined pattern. That is, after patterning the SiN dielectric film 112 through photolithography using a mask having a predetermined pattern on the dielectric film deposited on the second surface, the dielectric film 112 is removed along the pattern through etching using an appropriate etchant.

[0045] Thereafter, an electrolyte membrane 120 is formed on the first surface of the dielectric film 111 deposited on the first surface. The step of removing the dielectric film 112 deposited on the second surface by a predetermined pattern and the step of forming the electrolyte membrane 120 on the first surface of the dielectric film 111 deposited on the first surface may be reversed.

[0046] Thereafter, the portion of the dielectric film 112 on the second surface where it has been removed is etched to form a recess portion 140 such that the dielectric film 111 deposited on the first surface is exposed. At this time, wet etching using a KOH solution can be performed to etch the silicon substrate 110 from below.

[0047] Thereafter, the dielectric film 111 deposited on the first surface exposed through the recess portion 140 and the dielectric film 112 remaining on the second surface are removed.

[0048] Thereafter, the silicon substrate 110 is formed to be porous. At this time, for example, a method of forming porous silicon by immersing single-crystalline silicon in a hydrofluoric acid solution of a predetermined concentration and then performing anodic oxidation can be used.

[0049] Thereafter, a first electrode 130 is formed on at least a part of the first surface of the electrolyte film 120, and a second electrode 150 is formed on the second surface of the electrolyte film 120 exposed by removing the dielectric film 111 deposited on the first surface exposed through the recess portion 140.

[0050] The thin-film type solid oxide fuel cell 100 manufactured in this way is a thin-film type SOFC on a MEMS substrate. By forming the membrane and electrodes as thin films, ohmic losses due to ion conduction in the electrolyte can be minimized, and it is possible to improve the operating performance at low temperatures.

[0051] During operation, stress concentrates near the edge of the membrane (near the edge of the recess portion 140 in the membrane). In order to prevent the cells located in this vicinity from being damaged, by forming the silicon substrate 110 to be porous, the stress concentrated near the edge of the membrane (near the edge of the recess portion 140 in the membrane) can be dispersed.

[0052] In at least one embodiment of the present invention, the electrolyte film 120 can be formed as an ion-conductive ceramic electrolyte film using MEMS processes, and the first electrode 130 and the second electrode 150 can be formed using a porous platinum material.

[0053] In at least one embodiment of the present invention, the electrolyte membrane 120 can be formed of an individual oxygen ion conductor such as yttria-stabilized zirconia (YSZ) or a proton conductor such as yttrium-doped BaZrO3 (BYZ).

[0054] As described above, according to at least one embodiment of the present invention, it is possible to provide a thin-film solid oxide fuel cell having a stress relaxation structure at the membrane edge using porous silicon.

[0055] Furthermore, according to at least one embodiment of the present invention, it is possible to provide a method for manufacturing a thin-film solid oxide fuel cell having a stress relaxation structure at the membrane edge using porous silicon.

[0056] As described above, the present invention has been described using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. It is obvious to those skilled in the art that various changes or improvements can be made to the above embodiments. It is clear from the description of the claims that forms with such changes or improvements can also be included in the technical scope of the present invention.

Description of Reference Numerals

[0057] 100: Solid oxide fuel cell 110: Silicon substrate 111, 112: Dielectric film 120: Electrolyte membrane 130: First electrode 140: Recess portion 150: Second electrode 160: Porous portion

Claims

1. A step of depositing a dielectric film on the first surface of a silicon substrate and on the second surface which is the opposite surface of the first surface, respectively; A step of removing the dielectric film deposited on the second surface by a predetermined pattern; A step of forming an electrolyte film on the first surface of the dielectric film deposited on the first surface; A step of etching the portion of the second surface where the dielectric film has been removed to form a recess so that the dielectric film deposited on the first surface is exposed; A step of removing the dielectric film deposited on the first surface exposed through the recess and the dielectric film remaining on the second surface; A step of forming at least the vicinity of the edge of the recess of the silicon substrate to be porous; A step of forming a first electrode on at least a part of the first surface of the electrolyte film; A step of forming a second electrode on the second surface which is the opposite surface of the first surface of the electrolyte film exposed by removing the dielectric film deposited on the first surface exposed through the recess comprising A method for manufacturing a solid oxide fuel cell.

2. A step of depositing a dielectric film on the first surface of a single crystal silicon substrate and on the second surface which is the opposite surface of the first surface, respectively; A step of removing the dielectric film deposited on the second surface by a predetermined pattern; A step of forming an electrolyte film on the first surface of the dielectric film deposited on the first surface; A step of etching the portion of the second surface where the dielectric film has been removed to form a recess so that the dielectric film deposited on the first surface is exposed; A step of removing the dielectric film deposited on the first surface exposed through the recess and the dielectric film remaining on the second surface; A step of forming the silicon substrate to be porous; A step of forming a first electrode on at least a part of the first surface of the electrolyte film; A step of forming a second electrode on the second surface which is the opposite surface of the first surface of the electrolyte film exposed by removing the dielectric film deposited on the first surface exposed through the recess comprising A method for manufacturing a solid oxide fuel cell.

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