Discharge cell, ozone gas generator, and method for manufacturing discharge cell

Abstract

A discharge cell (24) for generating ozone gas by silent discharge comprises: a pair of electrodes (31) facing each other; at least one dielectric (32) formed between the pair of electrodes (31) facing each other; and discharge gaps (G) which are formed between the electrodes (31) and the dielectric (32) or between a pair of dielectrics (32), and through which oxygen gas passes. The at least one dielectric (32) comprises: recesses (43) constituting the discharge gaps (G); and ribs (42) facing the electrode (31) or another dielectric (32). The dielectric (32) and the ribs (42) are composed of aluminum oxide of the same quality and are integrally formed.

Description

Discharge cell, ozone gas generator, and method for manufacturing discharge cell

[0001] The present invention relates to a discharge cell, an ozone gas generator, and a method for manufacturing a discharge cell.

[0002] Ozone gas generators that generate ozone gas using oxygen gas as a raw material are widely used in semiconductor manufacturing processes and the like.

[0003] Patent Document 1 discloses an ozone gas generator including a silent discharge type discharge cell. In the discharge cell, dielectrics are respectively laminated on the inner sides of a pair of electrodes connected to a power source. When a voltage is applied to the pair of electrodes from the power source, silent discharge occurs in the discharge gap between the dielectrics, thereby generating ozone gas.

[0004] The discharge gap is formed between dielectrics arranged to face each other with a constant interval by interposing a rib therebetween. The ribs are formed, for example, by screen printing.

[0005] Japanese Patent Laid-Open No. 2011-051865

[0006] When screen printing is used to form ribs in a discharge cell, the accuracy of flatness (height variation at different locations) is insufficient. Therefore, in screen printing, ribs are formed higher than the required height, and then lapping (flattening by polishing) is performed to obtain the target height. However, the requirement for lapping increases the number of manufacturing steps.

[0007] An object of the present disclosure is to provide a discharge cell that can ensure flatness and simplify manufacturing steps, and a method for manufacturing the same.

[0008] The discharge cell of the present disclosure is a discharge cell that generates ozone gas by silent discharge, comprising: a pair of opposing electrodes; a pair of dielectrics formed between the pair of opposing electrodes; and a discharge gap formed between the pair of dielectrics through which oxygen gas passes. Each of the pair of dielectrics includes a recess that constitutes the discharge gap, and a rib facing the other dielectric. The dielectric and the rib are made of the same aluminum oxide and are integrally formed, and the top surfaces of the ribs of the respective dielectrics are adhered to each other via an adhesive layer.

[0009] The ozone gas generator of this disclosure comprises the above-mentioned discharge cell and an oxygen supply source that supplies oxygen with a purity of 99.9% or higher to the discharge cell.

[0010] The present disclosure is a method for manufacturing a discharge cell that generates ozone gas by silent discharge, comprising the steps of: forming a mask having an opening on one surface of a dielectric; peelably bonding the surface of the other surface of the dielectric to a support substrate; forming recesses in the openings of the mask in the dielectric and forming ribs in the portion covered by the mask by blasting; peeling the dielectric with the ribs formed on it from the support substrate; and, after peeling the dielectric from the support substrate, forming a film containing a metal oxide on the dielectric in the recesses, wherein the thickness of the dielectric is 0.9 mm or less.

[0011] The present disclosure is a method for manufacturing a discharge cell that generates ozone gas by silent discharge, comprising the steps of: forming a mask having an opening on one surface of a dielectric; forming a metal electrode layer on the other surface of the dielectric; fixing the dielectric to an electrostatic chuck via the metal electrode layer, and forming recesses in the opening of the mask in the dielectric and forming ribs in the portion covered by the mask by blasting, wherein the thickness of the dielectric is 0.9 mm or less.

[0012] According to the discharge cell and its manufacturing method disclosed herein, recesses and ribs are formed in the dielectric by blasting or etching, eliminating the need for lapping, ensuring accuracy, and simplifying the manufacturing process.

[0013] Figure 1 is a schematic diagram illustrating the ozone gas generator of the present disclosure. Figure 2 is a schematic cross-sectional view showing the ozone gas generation unit of the present disclosure, particularly its discharge cell. Figure 3 is a cross-sectional view corresponding to line III-III in Figure 2. Figure 4 is a cross-sectional view corresponding to line IV-IV in Figure 3. Figure 5 is a diagram illustrating a first method of manufacturing the discharge cell of the present disclosure. Figure 6 is a diagram illustrating a first method of manufacturing the discharge cell, following Figure 5. Figure 7 is a diagram illustrating a second method of manufacturing the discharge cell of the present disclosure. Figure 8 is a diagram illustrating a first modified discharge cell. Figure 9 is a diagram illustrating a second modified discharge cell.

[0014] The embodiments will be described below with reference to the drawings. The following description is illustrative and not limiting. Furthermore, modifications can be made as appropriate within the scope of achieving the desired effect.

[0015] (Ozone Gas Generator) Figure 1 is a schematic diagram showing the ozone gas generator (20) of the present disclosure. The ozone gas generator (20) comprises a raw material gas supply unit (21), an ozone gas generation unit (22), and an ozone gas extraction unit (23).

[0016] The raw material gas supply unit (21) is supplied with raw material gas. A supply pipe (not shown) is connected to the raw material gas supply unit (21). The raw material gas supply unit 21 is connected to a raw material gas supply source such as a gas cylinder via the supply pipe. High-purity oxygen gas (99.9% or higher) is used as the raw material gas.

[0017] The ozone gas generation unit (22) is supplied with raw material gas from the raw material gas supply unit (21). In the ozone gas generation unit (22), ozone gas is generated from oxygen gas by silent discharge. Details of the ozone gas generation unit (22) will be described later.

[0018] The ozone gas extraction unit (23) supplies the ozone gas generated in the ozone gas generation unit (22) to the outside. Extraction piping (not shown) is connected to the ozone gas extraction unit (23). The ozone gas extracted from the extraction piping is dissolved in, for example, pure water to produce ozonated water. This ozonated water is used, for example, to clean silicon wafers in semiconductor manufacturing equipment.

[0019] (Details of the ozone gas generation unit) Figures 2 to 4 show the ozone gas generation unit (22). Figure 3 corresponds to line III-III in Figure 2, and Figure 2 corresponds to line II-II in Figure 3. Also, Figure 4 corresponds to line IV-IV in Figure 3. However, all are schematic diagrams, and the dimensions, ratios, etc. do not necessarily correspond, nor do they necessarily reflect the actual dimensions.

[0020] As shown in Figure 2, the ozone gas generation unit (22) comprises a silent discharge type discharge cell (24) and a power supply (25) connected to the discharge cell (24). The discharge cell (24) has a high-pressure side electrode unit (30A) and a low-pressure side electrode unit (30B). Since the configuration of the high-pressure side electrode unit (30A) and the low-pressure side electrode unit (30B) is basically the same, they are sometimes collectively referred to as the electrode unit (30). The discharge cell (24) comprises at least one pair of such opposing electrode units (30).

[0021] A discharge gap (G) through which oxygen gas flows is formed between the high-pressure side electrode unit (30A) and the low-pressure side electrode unit (30B). The high-pressure side electrode unit (30A) is the electrode unit on the high-pressure side, and the low-pressure side electrode unit (30B) is the electrode unit on the ground side (low-pressure side).

[0022] The power supply (25) is composed of a high-frequency high-voltage power supply. The high-voltage side electrode unit (30A) has a high-voltage side electrode (31A), a high-voltage side dielectric (32A), and a high-voltage side functional film (33A), which are stacked sequentially in the thickness direction. The low-voltage side electrode unit (30B) has a low-voltage side electrode (31B), a low-voltage side dielectric (32B), and a low-voltage side functional film (33B), which are stacked sequentially in the thickness direction.

[0023] The high-voltage side electrode (31A) and the low-voltage side electrode (31B) are electrically connected to the power supply (25). The high-voltage side electrode (31A) and the low-voltage side electrode (31B) are formed in the shape of a plate or a film. The high-voltage side electrode (31A) and the low-voltage side electrode (31B) are positioned opposite each other with a discharge gap (G) in between.

[0024] The high-pressure side dielectric (32A) is formed on the discharge gap (G) side surface (lower surface in Figure 2) of the high-pressure side electrode (31A). The low-pressure side dielectric (32B) is formed on the discharge gap (G) side surface (upper surface in Figure 2) of the low-pressure side electrode (31B). The high-pressure side dielectric (32A) and the low-pressure side dielectric (32B) are formed in a plate shape. The high-pressure side dielectric (32A) and the low-pressure side dielectric (32B) are made of an insulating material such as alumina. The high-pressure side dielectric (32A) may cover the high-pressure side electrode (31A). Similarly, the low-pressure side dielectric (32B) may cover the low-pressure side electrode (31B).

[0025] Furthermore, since the configurations of the high-pressure side dielectric (32A) and the low-pressure side dielectric (32B) are basically the same, they are sometimes collectively referred to as dielectric (32). Similarly, the high-pressure side electrode (31A) and the low-pressure side electrode (31B) are sometimes collectively referred to as electrode (31).

[0026] The dielectric (32) is formed in the shape of a rectangular plate. The dielectric (32) may be obtained by firing high-purity alumina. The thickness of the dielectric (32) is preferably 0.05 to 0.9 mm.

[0027] As shown in Figure 4, the dielectric (32) has ribs (42) that protrude toward the discharge gap (G). The ribs (42) are formed from the dielectric (32) with a plurality of recesses (43) formed in the dielectric (32), and the portion of the dielectric (32) remaining between the recesses (43). The plurality of ribs (42) are arranged parallel to each other along the longitudinal direction of the inlet (51) and outlet (52), which will be described later, so as to be at equal intervals from each other (see Figure 3). In addition, a rectangular frame portion (41) is formed along the outer edge of the dielectric (32) by leaving the dielectric (32) in the same way as the ribs (42).

[0028] The two opposing dielectrics (32) are configured such that the top surfaces of their respective ribs (42) and the top surfaces of their frame portions (41) face each other via an adhesive layer (63).

[0029] The height of the ribs (42) is preferably 50 μm or less. Furthermore, the spacing of the discharge gaps (G) is preferably 20 μm or more and 100 μm or less.

[0030] A pair of opposing side edges of the dielectric (32) (the upper and lower side edges in Figure 3) each have an opening (an inlet (51) and an outlet (52)). The lower opening in Figure 3 is the inlet (51), and the upper opening in Figure 3 is the outlet (52). The inlet (51) and outlet (52) extend along the side edges of the dielectric (32) and penetrate the dielectric (32) in the thickness direction. The inlet (51) communicates with the raw material gas supply unit (21). The outlet (52) communicates with the ozone gas extraction unit (23).

[0031] Cooling passages (45) for cooling the ozone gas generation unit (22) are formed in the other pair of side edges of the dielectric (32) (the left and right side edges in Figure 3). The cooling passages (45) penetrate the dielectric (32) in the thickness direction, and the ozone gas generation unit (22) is cooled by the flow of a coolant through them.

[0032] The recesses (43) formed in the high-pressure dielectric (32A) and the low-pressure dielectric (32B), respectively, face each other to form a discharge gap (G). The discharge gap (G) communicates with the inlet (51) and outlet (52). Therefore, oxygen gas flows in the discharge gap (G) in the direction of the white arrow in Figure 3. The spacing of the discharge gap (G) is preferably 20 μm or more and 100 μm or less.

[0033] A high-pressure side functional film (33A) is formed on the discharge gap (G) side surface of the high-pressure side dielectric (32A) (the lower surface in Figures 2 and 4), more specifically on the bottom surface of the recess (43). Similarly, a low-pressure side functional film (33B) is formed on the discharge gap (G) side surface of the low-pressure side dielectric (32B) (the upper surface in Figures 2 and 4), more specifically on the bottom surface of the recess (43). Therefore, the discharge gap (G) is more precisely formed between the functional films (33). Since the configuration of the high-pressure side functional film (33A) and the low-pressure side functional film (33B) is basically the same, they are sometimes collectively referred to as the functional film (33). The functional film (33) is formed in the form of a plate or a film.

[0034] In the recess (43), the arithmetic mean roughness Ra of the surface of the dielectric (32) is preferably 0.3 μm or more and 0.4 μm or less. When the surface of the dielectric (32) has an Ra within this range, the adhesion of the functional film (33) formed on the surface improves. This makes it possible to suppress the peeling of the functional film from the dielectric during ozone gas generation and its subsequent inclusion in the ozone gas as particles.

[0035] Oxygen gas flows into the discharge void (G) upstream (for example, the left side in Figure 2). When a high-frequency AC voltage is applied from the power source (25) to the high-pressure electrode (31A) and the low-pressure electrode (31B), silent discharge occurs in the discharge void (G). The large number of electrons excited by the discharge generate oxygen radicals such as oxygen atoms, which in turn generate ozone gas. The ozone gas generated in the discharge void (G) flows out downstream (for example, the right side in Figure 3).

[0036] (Method for manufacturing a discharge cell) (First manufacturing method) Next, a method for manufacturing the discharge cell (24) of the present disclosure will be described. Figures 5 and 6 illustrate a first method for manufacturing one electrode unit (30) in the discharge cell (24), and show steps A to F individually. These figures are cross-sectional views showing the area crossing the rib (42) in the electrode unit (30).

[0037] In the method of this embodiment, a recess (43) is formed on one surface of the dielectric (32) using etching, blasting, or the like, and the remaining portion is made into a rib (42). In order to generate a high concentration of ozone gas, it is desirable to form ribs of low height to reduce the height of the discharge void (G). In a method of applying material to the dielectric (32) by screen printing and then lapping, it is difficult to form ribs of low height while ensuring the flatness of the top surface, so it is desirable to use etching or blasting as in this embodiment.

[0038] First, the outer shape of the discharge cell (24) and through-holes corresponding to the cooling passage (45), inlet (51), and outlet (52) are cut out from the dielectric sheet. As shown in step A, a mask (62) is formed on one side of the cut-out dielectric (32), with an opening (62A) in which a recess (43) is formed. Furthermore, one side of the dielectric (32) is removably bonded to the support substrate (61) for processing. This is done using a removable adhesive, wax, etc. (the adhesive, etc., is not shown in Figure 5).

[0039] Next, in step B, etching or blasting is performed on the dielectric (32) using the mask (62). As a result, recesses (43) are formed in the open (62A) portion not covered by the mask (62), and ribs (42) are formed in the portion covered by the mask (62).

[0040] From the viewpoint of improving the cooling efficiency of the discharge cell (24) and increasing the amount of ozone gas produced relative to the volume of the discharge cell (24), it is desirable to reduce the thickness of the dielectric (32), and in the recessed portion (43), it may be 0.9 mm or less. In addition, it is preferable that the height of the rib (42) be 50 μm or less.

[0041] If a dielectric (32) of this thickness is blast-processed on its own, there is a high possibility that the dielectric (32) will be damaged. In contrast, in this embodiment, by processing the dielectric (32) while it is bonded to a support substrate (61), damage to the dielectric (32) can be suppressed. The support substrate (61) can be made of a ceramic such as alumina, and it is preferable that its thickness is 5 mm or more.

[0042] Furthermore, because the height of the discharge gap (G) is small, a high degree of flatness is required for the bottom surface of the recess (43). From the viewpoint of achieving this, it is preferable to fix the dielectric (32) to the support substrate (61) and perform blast processing or the like.

[0043] Here, for the surface of the dielectric (32) serving as the bottom surface of the recess (43), the arithmetic average roughness Ra is set to be not less than 0.3 µm and not more than 0.4 µm. This can be achieved by setting conditions such as those for blasting.

[0044] Next, as shown in step C, the dielectric (32) is peeled from the support substrate (61), and the mask (62) is removed.

[0045] Next, as shown in step D of FIG. 6, a functional film (33) is formed on the surface of the dielectric (32) in the recess (43). The functional film (33) may be formed by forming a material film containing a metal oxide in the recess (43) by, for example, screen printing, and firing the material film.

[0046] The surface of the dielectric (32) at the portion where the functional film (33) is formed has an arithmetic average roughness Ra of not less than 0.3 µm and not more than 0.4 µm as described above. This improves the adhesion of the functional film (33) to the surface of the dielectric (32), suppresses peeling and the like, and allows the functional film (33) to be stably formed.

[0047] Next, as shown in step E, an electrode (31) is formed on the other surface of the dielectric (32) opposite to the side where the ribs (42), the functional film (33) and the like are provided. The electrode (31) may be formed by forming a material film containing a metal by, for example, screen printing, and firing the material film. After that, an adhesive layer (63) is formed on the electrode (31). The adhesive layer (63) may be formed by forming a material film containing a glass component by, for example, screen printing, and firing the material film.

[0048] Furthermore, in step E, an on-rib adhesive layer (64) is formed on the top surface (42A) of the rib (42). The on-rib adhesive layer (64) may also be formed by forming a material film containing a glass component by, for example, screen printing, and firing the material film.

[0049] Note that the on-rib adhesive layer (64) may be formed before the electrode (31), may be formed after the formation of the electrode (31) and before the formation of the adhesive layer (63), or may be formed after the formation of the adhesive layer (63).

[0050] Next, in step F, two laminates shown in E of Figure 6 are prepared, and the top surfaces (42A) of the ribs (42) are bonded together with the rib adhesive layer (64) in between. This forms the discharge cell (24) shown in Figures 2 and 4. Note that the rib adhesive layer (64) may be formed on only one of the top surfaces (42A).

[0051] When ribs are formed on the dielectric (32) as a separate component by screen printing or the like, the material of the ribs contains a large amount of glass. The adhesive layer (64) on the ribs also contains a large amount of glass. As a result, when the adhesive layer (64) on the ribs is softened by heating to perform bonding, the screen-printed ribs also soften at the same time, which may impair the accuracy of the height of the discharge gap (G).

[0052] In contrast, in this embodiment, the rib (42) is integrally formed from the same material as the dielectric (32), so it does not soften even at temperatures in which the adhesive layer (64) on the rib softens. This makes it possible to improve the accuracy of the height of the discharge gap (G) in step F.

[0053] In F, members (65) are also bonded to the surface opposite to the discharge gap (G) by an adhesive layer (63). Members (65) are, for example, alumina substrates in which a refrigerant flow path is formed.

[0054] According to the manufacturing method described above, a rib (42) integrated with the dielectric (32) can be formed by blasting or etching to create a recess (43). It is possible to obtain a rib (42) with the desired level of precision, and it is not necessary to lap the top surface (42A) of the rib (42). Therefore, the manufacturing process of the discharge cell (24) can be simplified. Furthermore, even when using a dielectric (32) with a thin thickness (for example, 0.9 mm or less), damage to the dielectric (32) can be suppressed by processing the dielectric (32) while it is bonded to the support substrate (61).

[0055] (Second manufacturing method) Next, a second manufacturing method for the discharge cell (24) will be described. Figure 7 is a diagram illustrating the second manufacturing method, showing steps G to I.

[0056] In the second manufacturing method, instead of bonding the dielectric (32) to the support substrate (61), the recess (43) is formed with the dielectric (32) fixed to the electrostatic chuck (66). For this purpose, in step G of Figure 7, an electrode (31) is formed on one surface of the dielectric (32) (the surface opposite to the surface on which the rib (42) is formed). The electrode (31) may be formed by screen printing and firing, as in the first manufacturing method.

[0057] Next, in step H, the dielectric (32) is fixed to the electrostatic chuck (66) via the electrode (31). Also, a mask (62) having an opening (62A) is formed on the surface of the dielectric (32) opposite to the electrode (31).

[0058] Next, in step I, etching or blasting is performed on the dielectric (32) using the mask (62). As a result, recesses (43) are formed in the openings (62A) that are not covered by the mask (62), and ribs (42) are formed in the parts covered by the mask (62).

[0059] By performing blasting or etching while the dielectric (32) is fixed to the electrostatic chuck (66), damage to the dielectric (32) can be suppressed, similar to the first manufacturing method.

[0060] Next, the mask (62) is removed, and a functional film (33) is formed on the surface of the dielectric (32) in the recess (43). This can be done in the same manner as described for step D in Figure 6 in the first manufacturing method. In addition, an adhesive layer (63) is formed on the electrode (31), and a rib-top adhesive layer (64) is formed on the top surface (42A) of the rib (42). These can be done in the same manner as described for step E in Figure 6.

[0061] Furthermore, the discharge cell (24) is formed in the same manner as in step F in Figure 6.

[0062] In the above method, the recesses (43) and ribs (42) are formed by blasting or etching, eliminating the need for lapping and simplifying the manufacturing process of the discharge cell (24). Furthermore, since the dielectric (32) is fixed to the electrostatic chuck (66) during blasting or etching, damage to the dielectric (32) can be suppressed.

[0063] (First Modification) Figure 8 is a schematic diagram of the discharge cell (24A) of the first modification. Figure 8 is a cross-sectional view showing the area crossing the two ribs (42) in the electrode unit (30), similar to Figures 5 and 6.

[0064] The first modified discharge cell (24A) comprises a high-pressure side electrode unit (30A) and a low-pressure side electrode unit (30C). The high-pressure side electrode unit (30A) has the same configuration as the high-pressure side electrode unit (30A) in Figures 2 and 4. In contrast, the low-pressure side electrode unit (30C) is the same as the low-pressure side electrode unit (30B) in Figures 2 and 4 in that it has an electrode (31), a dielectric (32), and a functional film (33), but it does not have a recess (43) and ribs (42), and the functional film (33) is formed on the flat surface of the dielectric (32). The top surface (42A) of the rib (42) in the high-pressure side electrode unit (30A) is bonded to the dielectric (32) in the low-pressure side electrode unit (30C) via a rib-top adhesive layer (64). The functional film (33) in the low-pressure side electrode unit (30C) has an opening where the rib (42) is bonded. As a result, a discharge gap (G) is formed in the recess (43) of the high-voltage side electrode unit (30A).

[0065] In this example, ribs (42) are formed only on the high-pressure side electrode unit (30A), but conversely, ribs (42) may be formed only on the low-pressure side electrode unit. In this case, recesses (43) and ribs (42) only need to be formed on the dielectric (32) of the high-pressure side electrode unit (30A), thus simplifying the manufacturing process of the discharge cell (24A).

[0066] (Second Modification) Figure 9 is a schematic diagram of the discharge cell (24B) of the first modification. Figure 9 is a cross-sectional view showing the area across the two ribs (42) in the electrode unit (30), similar to Figures 5 and 6.

[0067] The second modified discharge cell (24B) comprises a high-pressure side electrode unit (30A) and a low-pressure side electrode unit (30D). The high-pressure side electrode unit (30A) has the same configuration as the high-pressure side electrode unit (30A) in Figures 2 and 4. In contrast, the low-pressure side electrode unit (30D) does not have a dielectric or functional film, and consists only of an electrode (31). The top surface (42A) of the rib (42) in the high-pressure side electrode unit (30A) is bonded to the electrode (31) of the low-pressure side electrode unit (30D) via a rib-top adhesive layer (64). As a result, a discharge void (G) is formed in the recess (43) of the high-pressure side electrode unit (30A). In this modified example, it is desirable that the rib-top adhesive layer (64) be a room-temperature curing type.

[0068] A discharge cell that generates ozone gas by silent discharge may have a configuration like this.

[0069] Each embodiment described above may be modified in form or detail without departing from the spirit of the claims. Furthermore, the contents of each embodiment may be combined and substituted as appropriate, as long as they do not impair the functions covered by this disclosure.

[0070] According to this disclosure, the manufacturing process can be simplified, making it useful as a discharge cell and a method for manufacturing the same.

[0071] 20 Ozone gas generator 21 Raw material gas supply unit 24 Discharge cell 24A Discharge cell 24B Discharge cell 31 Electrode 32 Dielectric 33 Functional film 41 Frame 42 Rib 42A Top surface 43 Recess 45 Cooling passage 51 Inlet 52 Outlet 61 Support substrate 62 Mask 62A Opening 66 Electrostatic chuck G Discharge gap

Claims

1. A discharge cell for generating ozone gas by silent discharge, comprising: a pair of opposing electrodes; a pair of dielectrics formed between the pair of opposing electrodes; and a discharge void formed between the pair of dielectrics through which oxygen gas passes; each of the pair of dielectrics comprising a recess constituting the discharge void and a rib facing the other dielectric; the dielectrics and the ribs being made of the same aluminum oxide and integrally formed; and the top surfaces of the ribs in each dielectric being bonded together via an adhesive layer.

2. The discharge cell according to claim 1, characterized in that a film containing a metal oxide is formed on the dielectric in at least the recess.

3. The discharge cell according to claim 1, characterized in that the height of the ribs formed on at least one of the dielectrics is 50 μm or less.

4. The discharge cell according to claim 1, characterized in that the arithmetic mean roughness Ra of the surface of the recess is 0.3 μm or more and 0.4 μm or less.

5. The discharge cell according to claim 1, characterized in that the thickness of the dielectric is 0.9 mm or less.

6. An ozone gas generator comprising a discharge cell according to claim 1 and an oxygen supply source that supplies oxygen with a purity of 99.9% or higher to the discharge cell.

7. A method for manufacturing a discharge cell that generates ozone gas by silent discharge, comprising the steps of: forming a mask having an opening on one surface of a dielectric; peelably bonding the surface of the other surface of the dielectric to a support substrate; forming a recess in the opening of the mask in the dielectric and forming ribs in the portion covered by the mask by blasting; peeling the dielectric on which the ribs are formed from the support substrate; and, after peeling the dielectric from the support substrate, forming a film containing a metal oxide on the dielectric in the recess, wherein the thickness of the dielectric is 0.9 mm or less.

8. A method for manufacturing a discharge cell that generates ozone gas by silent discharge, comprising the steps of: forming a mask having an opening on one surface of a dielectric; forming a metal electrode layer on the other surface of the dielectric; fixing the dielectric to an electrostatic chuck via the metal electrode layer, and forming recesses in the opening of the mask and ribs in the portion covered by the mask of the dielectric by blasting, wherein the thickness of the dielectric is 0.9 mm or less.

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