JP2018006451A - Bonding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of bonding members together more firmly.SOLUTION: A bonded body 10 is obtained by a step of forming a layer 6 of metaboric acid by supplying a starting material composed of particulate boric acid, to at least a part of the bonding side face of a first member 2 heated to a first temperature of 180-280°C, a step of producing a molten material containing boron oxide, by heating the first member 2 where the layer of metaboric acid was formed to a second temperature of 500-700°C, a step of pressure-bonding a second member 4 of bonding object onto the molten material containing boron oxide, and a step of bonding the first member 2 and second member 4 via the layer 6 of metaboric acid, by solidifying the molten material containing boron oxide.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a joining method, and more particularly to a joining method between members made of an inorganic solid material.

  As an etching apparatus in manufacturing a semiconductor integrated device such as an LSI, a dry etching apparatus using plasma is used. In this apparatus, when a wafer to be etched is placed on the cathode of the planar electrode and an etching gas is introduced into the apparatus, a high frequency voltage is applied between the counter electrode (anode) and the cathode by a high frequency oscillator. Etching gas plasma is generated between the electrodes. Etching is performed by positive ions, which are active gases in the plasma, entering the wafer surface.

  Inside the dry etching apparatus, if metal parts are used, metal contamination occurs, so silicon parts are used. Typical silicon parts include a doughnut-shaped focus ring surrounding a wafer to be etched, a ground ring surrounding a lower electrode, an upper electrode plate, and protective members above and below the etching chamber (Patent Literature). 1). Of these, the focus ring or the like needs to have a larger diameter than the wafer to be etched. The current mainstream for 300 mm wafers is expensive because it is made from a silicon crystal ingot having a diameter of 320 mm or more.

JP 2002-190466 A

  If a silicon part such as a focus ring can be manufactured by joining a plurality of silicon members instead of a single part, various advantages such as reduction in manufacturing cost can be expected. Even in the case of non-silicon parts, the same effect can be expected if a plurality of members can be joined and manufactured.

  When the members are joined together, a problem may occur at the joining location, and there is an increasing demand for a method for joining a member such as a silicon member to a member to be joined.

  Then, an object of this invention is to provide the method which can join members more firmly.

  In the joining method according to the present invention, a starting material composed of particulate boric acid is supplied to at least a part of the joining side surface of the first member heated to a first temperature of 180 to 280 ° C. A step of forming a layer, a step of heating the first member on which the metaboric acid layer is formed to a second temperature of 500 to 700 ° C. to generate a melt containing boron oxide, and the oxidation A step of pressure-bonding a second member to be bonded onto a melt containing boron, and solidifying the melt containing boron oxide, thereby allowing the first member and the second member to pass through a layer of boron oxide. And the step of joining.

  According to the present invention, since the first member and the second member to be joined are joined via the boron oxide layer, both can be joined more firmly. And since what is used for joining is the layer of boron oxide obtained from boric acid, there is no fear of metal contamination.

  Since the boron oxide layer is formed by heating boric acid as a starting material at a predetermined 180 to 280 ° C. to obtain metaboric acid, and then heating the metaboric acid to 500 to 700 ° C., it is uniformly thin. It can be a layer. Such a boron oxide layer improves the adhesion between the first member and the second member.

  Since boron oxide is formed at a temperature of 700 ° C. or lower, even when at least one of the first member and the second member is made of silicon, cracking occurs in the silicon member due to the difference in thermal expansion coefficient between boron oxide and silicon. Does not occur.

It is the schematic which shows the conjugate | zygote joined by the method of this embodiment, FIG. 1A is a front view, FIG. 1B is a X arrow directional view in FIG. 1A. It is a perspective view which shows the 1st member used for this embodiment. It is a top view explaining the joining side of a modification. It is the schematic which shows the cyclic | annular member produced in the Example, FIG. 4A is a top view, FIG. 4B is a cross-sectional view. It is the schematic explaining the state before cutting out a 1st member. It is the schematic explaining the 1st member mounted on the hotplate. FIG. 7A is a side view for explaining Example 1, FIG. 7A is a side view of a joined body obtained by the first joining, and FIG. 7B is a side view of a joined body obtained by the second joining. FIG. 8A is a side view for explaining Example 2; FIG. 8A is a side view of a joined body obtained by the first joining, and FIG. 8B is a side view of the joined body obtained by the second joining.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1. Overall Configuration As shown in FIGS. 1A and 1B, in the present embodiment, a first member 2 made of a semiconductor material (silicon) and a second member 4 to be joined as an inorganic solid material are combined with boron oxide (B ₂ O ₃ ) To form a joined body 10. As shown in FIG. 1B, in the direction of the arrow X, the first member 2 and the second member 4 may be arranged so as to be shifted by a half (L / 2) of the length L of the first member 2. In this case, a region that is half of one surface (bonding side surface) of the first member 2 is a bonding region 3 a that is bonded to the second member 4.

  As the first member 2, for example, an arc-shaped plate as shown in FIG. 2 can be used. The illustrated first member 12 is an arc-shaped plate-like member corresponding to 1/6 of the circumference. The thickness t0 of the first member 12 is, for example, about 2 to 20 mm, and the width w0 of the first member 12 is, for example, about 30 to 60 mm. The first member 12 can be dimensioned to be an annular member having an outer diameter of about 300 to 600 mm and an inner diameter of about 280 to 580 mm by arranging six end surfaces together. As shown in FIG. 2, a half region of one surface (joining side surface) 13 of the first member 12 is a joining region 13 a, and a half of the joining side surface of the second member (not shown) is joined to the joining region 13. The

  The second member 14 can be a silicon member similar to the first member 12. As the second member 14, six arc-shaped plates having the same size as the first member 12 are used and bonded to the bonding region 13 a of the first member 12 as described above, thereby being twice the first member 12. An annular member having a thickness is obtained.

In the bonding method of the present embodiment, first, particulate boric acid (B (OH) _{3 is} applied to at least a part of the bonding side surface 13 of the first member 12 heated to the first temperature (180 to 280 ° C.). The starting material consisting of The first member 12 can be heated by a heating means using a general electric resistance heater. Since the temperature of the joining side surface 13 is 180 to 280 ° C., the dehydration reaction of boric acid occurs on the joining side surface 13. Water is desorbed from boric acid in about 10 to 60 seconds, and metaboric acid (HBO ₂ ) rich in fluidity is produced during that time.

  When the temperature of the first member 12 is too low, metaboric acid cannot be obtained by removing water from boric acid. On the other hand, if the temperature of the first member 12 is too high, water is rapidly desorbed from boric acid. As a result, boric acid supplied to the joining side surface 13 of the first member 12 is scattered or solidified metaboric acid is immediately generated. If the first temperature is 180 to 280 ° C., metaboric acid can be obtained without any inconvenience. The first temperature is preferably 200 to 240 ° C.

  As a starting material made of particulate boric acid, a granular commercial product having a diameter of 0.1 to 2 mm can be used as it is. A metaboric acid layer as described later is formed by supplying a starting material made of boric acid having a diameter of 0.1 to 2 mm to the joining side surface 13 of the first member 12 heated to the first temperature. Can do. It is preferable to supply boric acid little by little to a part of the joining side surface 13 of the first member 12.

  A metaboric acid layer can be obtained by extending the metaboric acid generated by removing water from boric acid with a spatula. As described above, boric acid as a starting material is supplied to the joining side surface 13 of the first member 12 little by little, and the resulting metaboric acid is extended each time, thereby forming a uniform metaboric acid layer in the joining region 13a. be able to. By using a spatula obtained by cutting a silicon wafer, it is possible to avoid contamination of the metaboric acid layer with impurities.

  The thickness of the metaboric acid layer is preferably 1 mm or less, and more preferably 0.1 to 0.5 mm. The smaller the thickness of the metaboric acid layer, the lower the generation of bubbles due to the dehydration reaction when heated in a later step. The thickness of the metaboric acid layer can be adjusted by controlling the amount of boric acid as a starting material to be supplied.

The first member 12 in which the metaboric acid layer is formed in the bonding region 13a is heated to raise the temperature to the second temperature (500 to 700 ° C.). As a result, water is further desorbed from metaboric acid, and a melt containing boron oxide (B ₂ O ₃ ) is obtained. If the second temperature is too high, the first member 12 may be cracked due to the difference in thermal expansion coefficient between boron oxide and silicon when cooled in a later step. When the second temperature is 500 to 700 ° C., a melt containing boron oxide can be obtained without such a problem. The second temperature is preferably 550 to 600 ° C.

  The second member 14 to be joined is pressure-bonded onto the melt containing boron oxide generated in the joining region 13a of the first member 12. The pressure at the time of pressure bonding is not particularly limited, and can be set as appropriate. When the width w0 of the first member 12 is about 30 mm, the first member 12 and the second member 14 can be joined by pressing by hand with a heat insulating material interposed therebetween.

  By solidifying the boron oxide melt, the first member 12 and the second member 14 are joined by the layer of boron oxide. The melt can be solidified, for example, by leaving it at room temperature.

2. Action and Effect According to the method of the present embodiment, when the first member 12 made of silicon and the second member 14 to be joined are joined, first, the first temperature heated to a first temperature (180 to 280 ° C.) is used. Since water is desorbed from boric acid as a starting material to form metaboric acid at the joining side surface 13 of one member 12, a layer of metaboric acid is formed uniformly. Next, the metaboric acid layer is heated to a second temperature (500 to 700 ° C.), so that water is further desorbed from the metaboric acid to form a melt containing boron oxide.

  The first member 12 and the second member 14 are bonded to each other through the boron oxide layer by pressing the second member 14 onto the melt containing boron oxide and solidifying the melt containing boron oxide. . Since the boron oxide layer is uniformly formed in the bonding region 13a on the bonding side surface 13 of the first member 12, the first member 12 and the second member 14 are firmly bonded with high adhesion. Since a layer of boron oxide obtained using boric acid as a starting material is used for bonding, there is no risk of metal contamination.

  Since the boron oxide that joins the first member 12 and the second part 14 material is formed by heating at 700 ° C. or less, the first member 12 is cracked due to the difference in thermal expansion coefficient between boron oxide and silicon. There is nothing.

3. The present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the gist of the present invention.

  The first member 12 is not limited to an arc-shaped plate, and an annular plate can also be used. Depending on the end use of the component manufactured using the method of the present invention, a disk-shaped plate or a rectangular plate can be used as the first member 12.

  The shape of the second member 14 to be joined can be appropriately selected according to the shape of the first member 12. The second member 14 does not necessarily have the same shape as the first member 12. For example, when an annular plate is used as the first member 12, a corresponding arc-shaped plate can be used as the second member 14.

  For heating the first member 12, any means capable of heating to the first temperature (180 to 280 ° C.) or higher can be used. The 1st member 12 may be heated using the lamp which can move a heating location easily. Examples of the lamp include a halogen lamp and a xenon lamp.

  The first member 12 and the second member 14 may be formed of a non-silicon semiconductor material such as SiC, for example. Furthermore, the first member 12 and the second member 14 can be formed of an inorganic solid material such as a glass material or a ceramic material. An example of the glass material is quartz glass, and an example of the ceramic material is alumina. The material of the first member 12 and the material of the second member 14 may be the same or different.

  The metaboric acid layer may be subjected to a treatment for removing at least a part of the surface thereof before being heated to the second temperature (500 to 700 ° C.). The treatment here can be performed by polishing. For example, the metaboric acid layer is cooled to about room temperature (25 ° C.) and solidified, and then dry polishing is performed using a sandpaper made of SiC. The metaboric acid layer does not necessarily need to be cooled to room temperature, and may be cooled to such an extent that sandpaper or the like can be polished without scorching.

  By dry polishing the cooled layer of metaboric acid, the thickness can be reduced to 1 mm or less without causing peeling. If the layer after polishing has a thickness of 0.05 mm or more, the bonding between the first member 12 and the second member 14 is ensured. Since the surface of the metaboric acid layer is flattened by polishing, the adhesion between the first member 12 and the second member 14 can be further enhanced.

  When at least one of the first member 12 and the second member 14 is made of silicon, the metaboric acid layer is not the entire area of the bonding side surface 13 of the first member 12 but the outer edge of the bonding side surface 13 as shown in FIG. You may form in frame shape along. In FIG. 3, a frame-like metaboric acid layer 15 is formed on the joining side surface 13 along the outer edge with a height of about 0.2 mm. The width w1 of the frame-shaped metaboric acid layer 15 may be 5 to 10 mm. A metal foil 17 that forms a eutectic with silicon is disposed in a region inside the frame-shaped metaboric acid layer 15. Examples of the metal that forms a eutectic with silicon include Al, Ga, Ge, and Sn.

  Before placing the metal foil 17 that forms a eutectic with silicon in the inner region, the frame-like metaboric acid layer may be cooled to polish the surface and reduce the thickness as described above. .

  After forming the frame-like metaboric acid layer 15 on the joining side surface 13 of the first member 12 and disposing the metal foil 17, the second member 14 is placed in the same manner as described above, and the eutectic temperature is 700 ° C. or higher. Heat to: When the metal forms a eutectic with silicon by heating, the first member 12 and the second member 14 can be joined more firmly. Since the eutectic formed here is surrounded by a frame-shaped boron oxide layer, there is little possibility that the metal diffuses and becomes a contamination source.

4). Example (Example 1)
An annular member 22 as shown in FIGS. 4A and 4B is produced using six first members 12a and six second members 14b. The first member 12a and the second member 14a are 1/6 arc-shaped plates made of silicon having the same shape and size. The first member 12a and the second member 14a are formed in a two-layered upper and lower layers by being alternately shifted by 30 degrees and arranged in six pieces.

  As shown in FIG. 5, two 1/6 arc-shaped plates as the first member 12a were cut out from the silicon ingot 20 for solar cells in a thickness of 5 mm. The diameter d0 of the silicon ingot 20 for solar cells is 215 mm. The width w0 of the cut out first member 12a is 30 mm. A 1/6 arc plate cut out in the same shape and thickness is also used as the second member 14a.

  The 1st member 12a and the 2nd member 14a were joined with the following methods using the hotplate provided with a 170-mm square top plate. As shown in FIG. 6, the first member 12a was placed on the hot plate 30 so that the bonding region 13a is at the center. The surface temperature of the first member 12a was measured with a contact thermometer, and the output of the hot plate was adjusted to 220 ° C. (first temperature).

  As shown in FIG. 6, half of one surface (bonding side surface) of the first member 12a becomes a bonding region 13a bonded to the second member 14a (not shown). A total of about 10 g of boric acid was supplied to the bonding region 13a. The used boric acid is a granular commercial product (manufactured by Kanto Chemical Co., Ltd., product number: 0432-80), and the diameter is about 0.1 to 2 mm.

  Boric acid was supplied by dropping about 0.5 g onto a part of one surface of the heated first member 12a, and boric acid was changed to metaboric acid by a dehydration reaction. The resulting metaboric acid was extended with a silicon spatula each time. By repeating these operations 20 times, a layer of metaboric acid was formed over the entire bonding region 13a. The thickness of the metaboric acid layer was 0.3 mm at the thin portion and 0.7 mm at the thick portion.

  After that, when the temperature of the hot plate was raised and the temperature of the first member 12a was raised to 530 ° C. (second temperature), the metaboric acid layer melted, but it was difficult to further extend this layer. It is presumed that when the temperature of the first member 12a was raised to 530 ° C., water was desorbed from metaboric acid and changed to boron oxide. A melt containing boron oxide was provided in the entire joining region 13a of the first member 12a.

  By placing the second member 14a on the melt containing boron oxide, applying pressure by hand with a heat insulating cloth sandwiched from above, and further solidifying the melt, the joined body 10a as shown in FIG. Obtained. In the direction of the arrow Y from the upper surface, the joined body 10a has a quarter arc shape. In the joined body 10a, the first member 12a and the second member 14a are joined together by a layer 16 of boron oxide. The pressure applied here is estimated to be about 4000 Pa.

  Next, the front and back of the joined body 10 a were reversed and moved so that the unjoined portion of the second member 14 a became the center of the hot plate 30. The first member 12a was joined to the second member 14a by supplying boric acid and heating by the same method as described above, and a joined body 10b as shown in FIG. 7B was obtained. In the direction of the arrow Y from the upper surface, the joined body 10a has a 1/3 arc shape.

  Similarly, the annular member 22 shown in FIG. 4A was obtained by joining the six first members 12a and the six second members 14a at a total of 12 locations. The annular member 22 had an outer diameter (d1) of 390 mm, an inner diameter (d2) of 330 mm, and a thickness (t) of 10 mm. The annular member 22 thus obtained can be used as a focus ring disposed inside the dry etching apparatus.

  In the annular member 22, the lower layer composed of the six silicon first members 12 a and the upper layer composed of the six second members 14 a are more firmly bonded via the boron oxide layer 16. Since the first member 12a and the second member 14a are bonded to the boron oxide layer 16 that does not contain a metal such as sodium, even if the annular member 22 is used as a focus ring, metal contamination is caused. The risk of this is very small.

  In the present example, a member having a predetermined shape was cut out from a silicon ingot for solar cells having a diameter of 215 mm and joined to produce an annular member 22 having an outer diameter of 390 mm.

  Incidentally, in order to obtain an annular member having an outer diameter of 390 mm as an integral member, a silicon ingot having an outer diameter of 390 mm or more is required. While such a large silicon ingot is very expensive, a silicon ingot for solar cells having a diameter of 215 mm is inexpensive and is produced on a standard basis. By using the method of the present embodiment, it becomes possible to greatly reduce the manufacturing cost of the annular member having an outer diameter of 390 mm.

(Example 2)
Using the same 1st member and 2nd member as Example 1, the same cyclic | annular member was produced by the same method. However, in this example, a hot plate provided with a 250 mm square top plate was used, and the metaboric acid layer was dry-polished before heating to the second temperature.

  Six first members were placed on a hot plate, and the entire first member was heated so that the surface became 220 ° C. (first temperature). A metaboric acid layer was formed in the same manner as in Example 1 using 20 g of boric acid over the entire area of the bonded side surface of the heated first member. The first member on which the metaboric acid layer was formed was removed from the hot plate and naturally cooled at room temperature (25 ° C.).

  The cooled metaboric acid layer was polished with a sandpaper # 500 made of SiC to a thickness of 0.2 mm.

  Two first members with the metaboric acid layer polished were put together on the hot plate with their end faces aligned, and the surface temperature was raised to 530 ° C. (second temperature). Thereby, the melt containing boron oxide was provided in the entire region of the joining side surface of the first member. On the melt containing boron oxide, one second member was disposed so as to extend over the two first members.

  As in the case of Example 1, a joined body 100a as shown in FIG. 8A was obtained by applying pressure by hand across the heat insulating cloth from above the second member and further solidifying the melt. In the joined body 100a, the second member 14a is joined to the two first members 12a via the boron oxide layer 16. In the direction of the arrow Y from the upper surface, the joined body 100a has a 1/3 arc shape.

  The obtained 1/3 arc-shaped plate was shifted on a table installed at the same height as the top plate of the hot plate, and the third first member was placed on the hot plate. In the same manner as described above, the temperature of the first member was raised and the second member of the second sheet was joined, so that a joined body 100b as shown in FIG. 8B was obtained. In the joined body 100b, two second members 14b are joined on the three first members 12a via a layer 16 of boron oxide. In the direction of the arrow Y from the upper surface, the joined body 100b has a half arc shape.

  By repeating this operation, an annular member similar to that shown in FIG. 4A was obtained. The annular member had an outer diameter (d1) of 390 mm, an inner diameter (d2) of 330 mm, and a thickness (t) of 10 mm.

  As in the case of Example 1, also in the annular member obtained in Example 2, the lower layer made of six silicon first members and the upper layer made of six second members are boron oxide layers. It is joined more firmly through. The possibility of metal contamination is extremely small as in the case of Example 1.

  In the annular member manufactured in Example 1, a gap of about 0.5 mm was generated between the first member 12a and the second member 14a. In Example 2, the gap was reduced to 0.2 mm. I was able to.

(Example 3)
Using the same 1st member and 2nd member as Example 2, the same cyclic | annular member was produced by the same method. However, in this example, the metaboric acid layer was formed in a frame shape along the outer edge of the joining side surface of the first member, and Sn foil was disposed in the inner region.

  Six first members were placed on a hot plate, and the entire first member was heated so that the surface became 220 ° C. (first temperature). On the joining side surface of the first member, a layer of metaboric acid having a width of 10 mm was formed in a frame shape along the outer edge using 2 g of boric acid. A groove having a width of 10 mm was formed inside the frame-shaped metaboric acid layer.

  The first member on which the frame-shaped metaboric acid layer was formed was cooled in the same manner as in Example 2 and then dry-polished to a thickness of 0.2 mm. An Sn foil rolled to 0.2 mm was spread over the inner region of the frame-shaped metaboric acid layer.

  A frame-shaped metaboric acid layer having a width of 10 mm and a height of 0.2 mm is formed along the outer edge on the joining side surfaces of the six first members, and Sn foil is disposed in the inner region. The six first members were placed in a circle on a rotating table, and six second members were stacked on the frame-shaped metaboric acid layer. The boundary between the two adjacent second members is shifted by 30 degrees with respect to the boundary between the two adjacent first members.

  From the upper side of the second member, a 5 kw xenon lamp whose irradiation area was adjusted to 70 mmφ was irradiated. At this time, the output of the lamp was adjusted so that the center surface temperature of the irradiation region was 650 ° C., and the whole was scanned by lamp irradiation by rotating the table. The scan rate was about 10 ° C./min.

  After scanning, an annular member similar to that shown in FIG. 4A was obtained by cooling to room temperature. The annular member had an outer diameter (d1) of 390 mm, an inner diameter (d2) of 330 mm, and a thickness (t) of 10 mm.

  As in the case of Examples 1 and 2, in the annular member obtained in Example 3, the lower layer made of six silicon first members and the upper layer made of six second members were boron oxide. It is joined more firmly through this layer. The possibility of metal contamination is extremely small as in the case of Examples 1 and 2.

  In particular, in this embodiment, since the eutectic of silicon and Sn is formed in the inner region of the boron oxide layer, the first member and the second member are bonded more firmly.

Example 4
The annular member produced in Example 3 is used as the first member, and the second member is joined to the annular member to produce an annular member having a larger thickness.

  As the second member, six arc-shaped SiC plates having a thickness of 1 mm obtained by the CVD method were prepared. Dimensions other than the thickness of the SiC arc-shaped plate are the same as those of the 1/6 arc-shaped plate cut out from the silicon ingot for solar cells in Example 1.

  Using the same hot plate as Example 2 and the stand installed at the same height as the top plate, the first member and the second member were joined by the following method. The first member was placed so that the bonding region was at the center of the hot plate, and heated so that the bonding side surface was 220 ° C. (first temperature).

  A metaboric acid layer was formed on the joining side surface of the first member by the same method as in Example 1. In forming the metaboric acid layer, 120 g of boric acid was supplied to the joining side surface of the first member, and the first member was rotated little by little. Thereafter, the hot plate was heated to raise the temperature of the first member to 530 ° C. (second temperature) to obtain a melt containing boron oxide. A second member was pressure-bonded onto the melt containing boron oxide by the same method as in Example 1.

  The first member was rotated so that the next joining region would be the center of the hot plate, and then the second second member was joined in the same manner as described above. The same operation was repeated, and the remaining four second members were similarly joined to the first member.

  Thereafter, when the hot plate was turned off and naturally cooled to room temperature, an annular member similar to that shown in FIG. 4A was obtained. The annular member had an outer diameter (d1) of 390 mm, an inner diameter (d2) of 330 mm, and a thickness (t) of 11 mm.

  As in the case of Examples 1 to 3, also in the annular member obtained in Example 4, the lower layer made of the first member made of silicon and the upper layer made of the six second members formed the boron oxide layer. It is joined more firmly through. The possibility of metal contamination is extremely small as in the case of Examples 1-3.

  Even when a non-silicon member such as SiC was used as the second member, it was confirmed that the second member could be firmly joined to the first member as in the case of the silicon member.

10 joined body 12 first member 14 second member 16 layer of boron oxide

Claims (6)

Supplying a starting material composed of particulate boric acid to at least a part of the joining side surface of the first member heated to a first temperature of 180 to 280 ° C. to form a metaboric acid layer;
Heating the first member on which the metaboric acid layer is formed to a second temperature of 500 to 700 ° C. to generate a melt containing boron oxide;
Crimping the second member to be bonded onto the melt containing boron oxide;
A bonding method comprising: solidifying the boron oxide-containing melt to bond the first member and the second member through a layer of boron oxide.   The joining method according to claim 1, wherein at least one of the first member and the second member is made of silicon.   The metaboric acid layer is formed by detaching water from the boric acid on the joining side surface of the first member heated to the first temperature to change it to metaboric acid, and extending the metaboric acid. The bonding method according to claim 1, wherein the bonding method is formed. Before producing the melt containing boron oxide,
The joining method according to claim 1, further comprising a step of solidifying the metaboric acid layer and removing at least a part of a surface of the solidified metaboric acid layer. The metaboric acid layer is formed in a frame shape along an outer edge of the joining side surface of the first member,
Inside the frame-shaped metaboric acid layer, a metal foil that forms a eutectic with silicon is disposed,
The joining method according to claim 2, wherein the second temperature is equal to or higher than a eutectic temperature of the metal. 6. The bonding method according to claim 5, wherein the metal that forms a eutectic with silicon is selected from Al, Ga, Ge, and Sn.

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