JP5613580B2 - Substrate manufacturing method - Google Patents

Description

  The present invention relates to a substrate manufacturing method, and more particularly to a substrate manufacturing method in which a first substrate and a second substrate are bonded.

  2. Description of the Related Art Conventionally, a substrate bonding technique in which the same type or different types of thin substrates are bonded together has been used. This substrate bonding technique expands the manufacturing and design methods for electronic components and optical components. For this reason, it is possible to increase the functionality and cost of electronic components and optical components. As a structure using this substrate bonding technique, for example, a structure in which a glass wafer in which a cavity is dug for bonding of a micro electro mechanical systems (MEMS) device formed on a silicon (Si) substrate is bonded to the silicon substrate. In order to form an optical waveguide, a structure in which an InP (indium phosphide) substrate is bonded onto a silicon substrate has been proposed.

  In an electronic component and an optical component using such a substrate bonding technique, a technique using a resin adhesive is used as an inexpensive technique as the substrate bonding technique. However, the resin has low environmental resistance against heat, humidity and the like. Therefore, the resin causes deterioration of characteristics and poor reliability of electronic parts and optical parts. For this reason, a technique for directly bonding the surfaces of substrates without using a resin adhesive is required.

  As a direct bonding technique, there is a technique in which the surfaces of the substrates are made highly clean and highly smooth by chemical cleaning and polishing, the substrates are bonded to each other by atomic force, and finally heated to obtain a strong bond. This technique is called diffusion bonding. In this method, it is necessary to heat to near the melting point of the material in order to obtain a sufficient bonding strength. For example, a substrate bonded with silicon substrates is heated to 1000 ° C. or more. Thereafter, the substrate is pressurized and bonded. Here, in the case of dissimilar substrate bonding, if the thermal expansion coefficients are slightly different, there is a disadvantage that the bonded substrates are destroyed due to the difference in shrinkage between the bonded substrates when they are cooled to room temperature. The materials that can be applied are limited.

  Next, as a technique for realizing direct bonding at a low temperature, there is a technique in which a voltage is applied between substrates at the time of bonding and bonding is performed using an electrostatic force. This technique is called anodic bonding. In this anodic bonding, for example, a silicon substrate and a Pyrex (registered trademark) glass substrate can be firmly bonded at 400 ° C. However, in this anodic bonding, an insulating substrate having no ion conductivity cannot be bonded, so that applicable substrate materials are limited.

  As a method for realizing strong direct bonding by heating at several 100 ° C., there is a method of bonding the substrate surfaces by cleaning and activating them with plasma, ion beam or the like. This technique is called surface activated bonding. Various techniques have been proposed for this surface activated bonding.

  For example, in Japanese Patent Laid-Open No. 10-92702 (Patent Document 1), an argon (Ar) ion beam is irradiated in a vacuum to clean and activate the bonding surface of the silicon wafer, and the silicon wafer is bonded at room temperature in the vacuum as it is. Techniques to do this have been proposed. In this technique, since the silicon wafer is bonded in a vacuum, a contamination layer (contamination layer) formed in an air atmosphere does not adhere to the bonding surface of the silicon wafer. Therefore, a covalent bond can be formed by dangling bonds of surface atoms on the bonding surface. Therefore, strong bonding at room temperature may be possible.

In Japanese Patent Application Laid-Open No. 2004-54170 (Patent Document 2), a crystal surface is etched by an Ar ion beam for about several tens of nanometers to be cleaned, and then a slight load is applied to bring the crystal surface into close contact. There has been proposed a technique for joining by heating below (for example, 600 ° C. in the case of YVO ₄ (yttrium vanadate)). In this technique, bonding at a melting point or lower can improve optical characteristics because there is no distortion of the bonding surface.

  Japanese Unexamined Patent Application Publication No. 2009-226212 (Patent Document 3) proposes a technique of heating at about 200 ° C. after irradiating the surface of a plate-like member with plasma. In this technique, excessive moisture adsorbed by the substrate is desorbed, and generation of bubbles in the main bonding can be suppressed. This technique can enable bonding with less voids.

  Japanese Patent Application Laid-Open No. 2005-79353 (Patent Document 4) discloses a technique in which oxygen plasma is irradiated on the surface of a substrate to activate the surface to adsorb OH groups, and then a radical is irradiated with nitrogen plasma. Proposed. In this technique, the two-stage irradiation with oxygen plasma and nitrogen plasma can bond the substrates more firmly than when only oxygen plasma is irradiated.

JP-A-10-92702 JP 2004-54170 A JP 2009-226212 A JP 2005-79353 A

  In the technique disclosed in Japanese Patent Laid-Open No. 10-92702, there is a problem that a mechanism for transporting a silicon wafer in a vacuum increases the cost of the apparatus. Furthermore, since pumping to an ultra-high vacuum state is required for each silicon wafer or lot, there is a problem in that the manufacturing cost increases due to a decrease in throughput (processing capacity per unit time).

  Moreover, in the technique of said Unexamined-Japanese-Patent No. 2004-54170, since it does not fully activate on the crystal | crystallization surface only by the etching by Ar ion beam, the spontaneous joining force is weak. Therefore, when joining a large area, an unjoined part tends to remain. Also, the bonding strength is lowered. For this reason, there exists a problem that the joint strength required for post processes, such as dicing, cannot be obtained.

  Moreover, in the technique of said Unexamined-Japanese-Patent No. 2009-226212, since the excess water | moisture content will remove | deviate simultaneously with the heating before temporary joining, OH group will also detach | desorb, and it is after the joining defect by a lack of spontaneous joining force, this joining There is a problem that insufficient bonding strength occurs.

  In the technique disclosed in Japanese Patent Application Laid-Open No. 2005-79353, radical irradiation can be performed only with an apparatus having a special mechanism, so that the apparatus introduction cost becomes high. Therefore, there exists a problem that manufacturing cost becomes high.

  The present invention has been made in view of the above problems, and its purpose is to manufacture a substrate that can suppress the generation of voids, can improve the bonding strength, and can reduce the manufacturing cost. Is to provide a method.

The substrate manufacturing method of the present invention is a method of manufacturing a substrate in which a first substrate and a second substrate are bonded, and includes the following steps. A first substrate having one surface irradiated with a rare gas plasma and an oxygen plasma are irradiated, and a second substrate having one surface having higher hydrophilicity than one surface of the first substrate is prepared. One side of the first substrate and one side of the second substrate face each other and are bonded together in the atmosphere to be temporarily bonded. The first substrate and the second substrate in the temporarily bonded state are heated and bonded. The first substrate and the second substrate in the temporarily bonded state are pressurized. The step of heating and bonding includes a step of heating the first substrate and the second substrate in a pressurized state in a state where the pressure is returned to no pressure.

  According to the substrate manufacturing method of the present invention, the hydrophilicity of one surface of the second substrate is increased because oxygen plasma is irradiated. Therefore, since the OH group is sufficiently adsorbed on one surface of the second substrate, the spontaneous bonding force is improved. Thereby, joint strength can be improved.

  Further, since one surface of the second substrate has high hydrophilicity, many water molecules are adsorbed. If many water molecules are adsorbed, voids are likely to occur. Therefore, one surface of the first substrate is irradiated with rare gas plasma so that the surface is cleaned and adsorption of OH groups is less than that of the second substrate. Therefore, water molecule adsorption is less than that of the second substrate. Thereby, when the 1st substrate and the 2nd substrate are pasted together, the amount of moisture of a joined part can be controlled. For this reason, generation | occurrence | production of a void can be suppressed when the 1st board | substrate and 2nd board | substrate of the state joined temporarily are heated. The bonding strength can also be improved by suppressing the generation of voids.

  Further, even if one surface of the first substrate and one surface of the second substrate are bonded together in the atmosphere and temporarily bonded, the amount of moisture can be reduced, so that an apparatus for temporarily bonding in vacuum is not required. Become. Therefore, in the present invention, the cost of the apparatus can be reduced as compared with the case where temporary bonding is performed in a vacuum. Further, since no special apparatus other than the apparatus for irradiating the rare gas plasma and the oxygen plasma is necessary, the apparatus introduction cost can be reduced. Therefore, manufacturing cost can be reduced.

It is a figure which shows the manufacturing method of the board | substrate in Embodiment 1 of this invention. It is a figure which shows the manufacturing method of the board | substrate in Embodiment 2 of this invention. It is a figure which shows the manufacturing method of the board | substrate in Embodiment 3 of this invention. It is a figure which shows the manufacturing method of the board | substrate of the modification in Embodiment 3 of this invention. It is a figure which shows the manufacturing method of the board | substrate in Embodiment 4 of this invention. It is a figure which shows the manufacturing method of the board | substrate in Embodiment 5 of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
First, a method for manufacturing a substrate according to the first embodiment of the present invention will be described.

  First, referring to FIG. 1, a substrate 10 is manufactured by bonding a first substrate 1 and a second substrate 2. The first substrate 1 is, for example, a Pyrex (registered trademark) glass substrate. In this case, the first substrate 1 is set to have a diameter of 4 inches and a thickness of 0.3 mm, for example. The second substrate 2 is, for example, a silicon substrate. In this case, the first substrate 1 is set, for example, to a diameter of 4 inches (10.16 cm), a thickness of 0.3 mm, a conductivity type p-type, and a resistivity of 1 to 10 Ωcm.

  The one surface 1a of the first substrate 1 is irradiated with rare gas plasma. One surface 1a of the first substrate 1 is irradiated with argon (Ar) plasma at a pressure of 10 Pa and an RF power of 100 W for 30 seconds by, for example, a parallel plate type plasma irradiation apparatus. In this way, the one surface 1a of the first substrate 1 is subjected to Ar plasma treatment. Thereby, the effect of surface cleaning can be obtained on the one surface 1a of the first substrate 1.

One surface 2a of the second substrate 2 is irradiated with oxygen plasma. One surface 2a of the second substrate 2 is irradiated with oxygen (O ₂ ) plasma having a pressure of 10 Pa and an RF (radio wave) power of 100 W for 30 seconds by, for example, a parallel plate type plasma irradiation apparatus. In this way, the O ₂ plasma treatment is performed on the one surface 2 a of the second substrate 2. As a result, the surface cleaning effect and high hydrophilicity can be obtained on the one surface 2a of the second substrate 2. Therefore, OH groups are sufficiently adsorbed on the one surface 2 a of the second substrate 2.

  The first substrate 1 having the one surface 1a irradiated with the rare gas plasma and the second substrate 2 having the one surface 2a irradiated with the oxygen plasma are prepared (step S1).

  Next, the first surface 1a of the first substrate 1 which is the plasma irradiation surface and the one surface 2a of the second substrate 2 face each other, and the first substrate 1 and the second substrate 2 are bonded together in the atmosphere. Temporary joining is performed (step S2). When the first substrate 1 and the second substrate 2 are bonded together, the first substrate 1 and the second substrate 2 are overlapped with each other, and the first substrate 1 and the second substrate 2 are overlapped with each other. The surface spreads and the one surface 1a of the first substrate 1 and the one surface 2a of the second substrate 2 are in close contact with each other.

  In addition, when the Pyrex (registered trademark) glass substrate is used for the second substrate 2, the appearance of the contact surface spreading is confirmed by the disappearance of the interference fringes visible from the Pyrex (registered trademark) glass substrate side.

  Further, in this temporary bonding, the spontaneous bonding force is reduced if the OH groups are not sufficiently adsorbed. In this case, since the undulation of the first substrate 1 and the second substrate 2 cannot be followed, the area of temporary bonding does not increase.

  Next, the first substrate 1 and the second substrate 2 in the temporarily bonded state are heated and bonded (step 3). The heat treatment is performed for about 8 hours at 300 ° C. in nitrogen or an air atmosphere using, for example, an annealing furnace. Thereby, the 1st board | substrate 1 and the 2nd board | substrate 2 shift to the covalent bond of Si-O-Si from the ionic bond by OH group. Thus, the 1st board | substrate 1 and the 2nd board | substrate 2 will be in this joining state.

  Since the bonding between the first substrate 1 and the second substrate 2 is strengthened by heating, the unbonded portion is reduced. That is, the bonding surface between the first substrate 1 and the second substrate 2 is widened. Further, the unbonded portion is reduced by the activation of the surfaces of the one surface 1a of the first substrate 1 and the one surface 2a of the second substrate 2 or the relaxation of the residual stress of the first substrate 1 and the second substrate 2 by heating. .

  Here, when a Pyrex (registered trademark) glass substrate is used for the first substrate 1 and a silicon substrate is used for the second substrate 2, the bonding strength, depending on the specifications such as the electrical characteristics, the outer shape, and the component composition, There is almost no difference in the void generation rate. However, since the surface roughness greatly affects the success or failure of bonding, the RMS (root mean square roughness) is required to be 1 nm or less.

  On the other hand, the bonding strength and void generation rate differ depending on the plasma conditions. As the plasma conditions, the smaller the power and the shorter the irradiation time, the smaller the surface roughness, and the less the ion implantation into the surface, the better the bonding strength and void generation rate. However, since it is necessary to obtain a sufficient surface cleaning effect by plasma irradiation, at least RF power and irradiation time are required so that organic substances are removed by 1 nm or more.

  The higher the heat treatment temperature, the higher the bonding strength. For example, when heated at 300 ° C., the bonding strength is 10 MPa, but when heated at 500 ° C., a bonding strength of about 30 MPa is obtained. However, if the temperature is too high, substrate cracking and surface roughness are caused. Therefore, it is preferable to keep the heating temperature at about half of the melting point.

Note that in this embodiment, all the steps may be performed without pressure.
Next, the effect of the embodiment of the present invention will be described in comparison with a comparative example.

Referring to FIG. 1 and Table 1, in Comparative Examples 1 to 3, Invention Example 1 and Invention Example 2, the Pyrex (registered trademark) glass substrate described above is used as the first substrate 1, respectively. The aforementioned silicon (Si) substrate is used as the substrate 2. In comparative example 1, both substrates are irradiated with Ar plasma for 30 seconds. In Comparative Example 2, both substrates are irradiated with O ₂ plasma for 30 seconds. In Comparative Example 3, both substrates are irradiated with O ₂ plasma for 5 seconds. On the other hand, in Example 1 of the present invention, the Pyrex (registered trademark) glass substrate is irradiated with Ar plasma for 30 seconds, and the Si substrate is irradiated with O ₂ plasma for 30 seconds. In Invention Example 2, the Pyrex (registered trademark) glass substrate is irradiated with Ar plasma for 5 seconds, and the Si substrate is irradiated with O ₂ plasma for 5 seconds.

The non-bonding region of Comparative Example 1 is 35%, the non-bonding region of Comparative Example 2 is 17%, and the non-bonding region of Comparative Example 3 is 11%. On the other hand, the non-joining area | region of this invention example 1 is 7%, and the non-joining area | region of this invention example 2 is 5%. In this way, in surface activated bonding, one substrate is irradiated with Ar plasma, and the other substrate is irradiated with O ₂ plasma, thereby suppressing generation of voids (bubbles) during heating, thereby suppressing non-bonded regions. can do. In addition, the non-joining area | region of this invention example 1 and this invention example 2 originates in a board | substrate dirt, respectively.

When both substrates are irradiated with Ar plasma as in Comparative Example 1, the effect of surface cleaning is obtained, but the hydrophilicity does not increase. For this reason, spontaneous bonding force becomes small. As a result, the surface does not adhere to each other, so that a large number of non-bonded regions remain. On the other hand, when both substrates are irradiated with O ₂ plasma as in Comparative Example 2 and Comparative Example 3, the effect of surface cleaning and high hydrophilicity can be obtained, but the adsorption of water molecules on the surface increases. Therefore, voids (bubbles) are generated due to evaporation of water molecules during the subsequent heating of the main bonding. For this reason, many non-joining regions remain.

  On the other hand, according to the manufacturing method of the substrate 10 of the present embodiment, the hydrophilicity of the one surface 2a of the second substrate 2 is increased because the oxygen plasma is irradiated. Therefore, since the OH group is sufficiently adsorbed on the one surface 2a of the second substrate 2, the spontaneous bonding force is improved. Thereby, joint strength can be improved.

  Further, since the hydrophilicity is high on the one surface 2a of the second substrate 2, a lot of water molecules are adsorbed. If many water molecules are adsorbed, voids are likely to occur. Therefore, the one surface 1a of the first substrate 1 is irradiated with rare gas plasma, so that the surface is cleaned and the adsorption of OH groups is less than that of the second substrate. Therefore, the adsorption of water molecules is less than that of the second substrate 2. Thereby, when the 1st board | substrate 1 and the 2nd board | substrate 2 are bonded together, the moisture content of a junction part can be suppressed. For this reason, when the 1st board | substrate 1 and the 2nd board | substrate 2 of the state joined temporarily are heated, generation | occurrence | production of a void can be suppressed. The bonding strength can also be improved by suppressing the generation of voids.

  In addition, when the first substrate 1 and the second substrate 2 are bonded together in the atmosphere and temporarily bonded, the water molecules adsorbed on the one surface 2a of the second substrate 2 are on one surface of the first substrate 1. 1a becomes a hydrophilic group. Therefore, the amount of water molecules adsorbed on the one surface 2a of the second substrate 2 is reduced. For this reason, generation | occurrence | production of a void can be suppressed at the time of a heating.

  Moreover, even if the one surface 1a of the first substrate 1 and the one surface 2a of the second substrate 2 are pasted together and temporarily joined in the air, the amount of moisture can be reduced, so that the temporary joining in a vacuum can be performed. A device becomes unnecessary. Therefore, in this embodiment, the cost of the apparatus can be reduced as compared with the case where temporary bonding is performed in a vacuum. Further, since no special apparatus other than the apparatus for irradiating the rare gas plasma and the oxygen plasma is necessary, the apparatus introduction cost can be reduced. Therefore, manufacturing cost can be reduced.

  In addition, in a package of a MEMS sensor in which a Pyrex (registered trademark) glass substrate and a silicon substrate are bonded, generation of voids (bubbles) can be suppressed in a heating process after temporary bonding. Thereby, the voiceless joining can be realized. By suppressing the generation of voids, a package of a MEMS device or the like can be manufactured with a high yield. For this reason, productivity can be improved.

(Embodiment 2)
In the second embodiment of the present invention, krypton plasma or xenon plasma is used in addition to the argon plasma used in the first embodiment. Since the other configuration and the manufacturing method of the present embodiment are the same as those of the first embodiment described above, the same elements are denoted by the same reference numerals and description thereof is not repeated.

  Referring to FIG. 2, one surface 1a of first substrate 1 is irradiated with krypton (Kr) plasma or xenon (Xe) plasma. In this way, the Kr or Xe plasma treatment is performed on the one surface 1a of the first substrate 1.

  According to the method for manufacturing the substrate 10 of the present embodiment, the rare gas plasma is any of argon plasma, krypton plasma, or xenon plasma. Thereby, the effect of surface cleaning can be obtained on the one surface 1a of the first substrate 1.

  In addition, when argon plasma is used, there are a large number of irradiated ions buried between lattices of silicon crystals. When krypton plasma or xenon plasma is used, since krypton atoms and xenon atoms are larger than argon atoms, krypton or xenon suppresses the irradiation ions from being buried between the lattices of the silicon crystal. Therefore, with krypton and xenon, the irradiated ions are difficult to be taken in deeper positions on the substrate surface. Thereby, generation | occurrence | production of the void (bubble) by degassing by a heating process can be made harder to occur.

(Embodiment 3)
The third embodiment of the present invention is different from the first embodiment in that the first substrate and the second substrate are pressurized after the temporary bonding.

  With reference to FIG. 3, in the present embodiment, first substrate 1 and second substrate 2 in a temporarily bonded state are heated in a pressurized state (step S3). The pressure of pressurization is set to 10 MPa, for example.

  According to the method for manufacturing the substrate 10 of the present embodiment, the step of heating and bonding the first substrate 1 and the second substrate 2 includes the first substrate 1 and the second substrate in a temporarily bonded state. A step of heating the substrate 2 in a pressurized state is included. The bonding strength can be further improved by heating the first substrate 1 and the second substrate 2 in a pressurized state. Further, when the first substrate 1 and the second substrate 2 are pressed, regions that have not been bonded at the time of temporary bonding due to particles and substrate warpage can be bonded.

  Further, if the first substrate 1 and the second substrate 2 are heated in a pressurized state, the substrate may be cracked. Therefore, the first substrate 1 and the second substrate 2 are not heated. The pressure may be returned to no pressure.

  Referring to FIG. 4, in the modification of the present embodiment, first substrate 1 and second substrate 2 in a temporarily bonded state are pressurized (step S4). Next, the pressurized first substrate 1 and second substrate are returned to no pressure. The first substrate 1 and the second substrate are heated in a non-pressurized state (step S3).

  According to the method for manufacturing the substrate 10 of the modification of the present embodiment, the method further includes the step of pressurizing the first substrate 1 and the second substrate 2 in the temporarily bonded state. The step of heating and joining includes a step of heating the first substrate 1 and the second substrate 2 in a pressurized state in a state where the pressure is returned to no pressure. When the first substrate 1 and the second substrate 2 in the temporarily bonded state are pressurized, the bonding strength can be further improved. By heating the first substrate 1 and the second substrate 2 in a state where the first substrate 1 and the second substrate 2 are returned to no pressure, the possibility of substrate cracking can be reduced. Further, when the first substrate 1 and the second substrate 2 are pressed, regions that have not been bonded at the time of temporary bonding due to particles and substrate warpage can be bonded.

(Embodiment 4)
In Embodiment 4 of the present invention, a semiconductor crystal or an oxide material is used as a material for the first substrate and the second substrate.

  In this embodiment mode, the material of the first substrate and the second substrate may be an oxide material or a semiconductor crystal. That is, at least one of the first substrate and the second substrate may include a semiconductor crystal. As the semiconductor crystal, for example, silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), or the like can be applied. Further, at least one of the first substrate 1 and the second substrate 2 may include an oxide material. As the oxide material, for example, quartz can be applied.

With reference to FIG. 5, as an example of the present embodiment, a case where a quartz substrate 3 as a first substrate and a GaAs substrate 4 as a second substrate are bonded will be described. Ar plasma is irradiated to one surface 3a of the quartz substrate 3, and O ₂ plasma is irradiated to one surface 4a of the GaAs substrate 4 (step S1). Next, the one surface 3a of the quartz substrate 3 and the one surface 4a of the GaAs substrate 4 are bonded together in the atmosphere and temporarily joined (step S2). Thereafter, the quartz substrate 3 and the GaAs substrate 4 in the temporarily bonded state are heated and bonded (step S3). Thereby, for example, a highly efficient light emitting element can be manufactured. This light-emitting element can be manufactured with high yield because there are few voids at the bonding interface.

It is not necessary to change the plasma irradiation conditions depending on the substrate material. On the other hand, the surface roughness is 1 nm or less in RMS (root mean square roughness) regardless of the substrate material. Note that bonding is possible even if the GaAs substrate 4 is irradiated with Ar plasma and the quartz substrate 3 is irradiated with O ₂ plasma. However, when the non-oxide material is irradiated with O ₂ plasma, the bonding strength is improved and the void generation rate is reduced, so that the GaAs substrate 4 is irradiated with O ₂ plasma and the quartz substrate 3 is irradiated with Ar plasma. Is preferred.

  According to the method for manufacturing substrate 10 of the present embodiment, at least one of the first substrate and the second substrate may include a semiconductor crystal. Therefore, in a MEMS sensor package in which at least one of the first substrate and the second substrate 2 includes a semiconductor crystal, generation of voids (bubbles) can be suppressed in the heating process after temporary bonding.

  According to the method for manufacturing the substrate 10 of the present embodiment, at least one of the first substrate and the second substrate may include an oxide material. For this reason, in the MEMS sensor package in which at least one of the first substrate and the second substrate includes an oxide material such as a glass substrate, generation of voids (bubbles) is suppressed in a heating process after temporary bonding. Can do.

  In addition, in a light emitting element or the like in which the quartz substrate 3 and the GaAs substrate 4 are bonded, generation of voids (bubbles) can be suppressed in the heating process after temporary bonding. This light-emitting element can be manufactured with high yield because there are few voids at the bonding interface.

(Embodiment 5)
In Embodiment 5 of the present invention, an optical crystal is used as a material for the first substrate and the second substrate.

In this embodiment mode, an optical crystal is used as a material for the first substrate and the second substrate. That is, at least one of the first substrate and the second substrate may contain an optical crystal. As the optical crystal, for example, YAG (yttrium / aluminum / garnet), Nd: YAG (neodymium / yttrium / aluminum / garnet), YVO ₄ (yttrium / vanadate), ZnS (zinc sulfide), or the like can be applied.

  With reference to FIG. 6, a case where a YAG substrate 5 as a first substrate and an Nd: YAG substrate 6 as a second substrate are bonded as an example of the present embodiment will be described. In the present embodiment, a description will be given of a substrate 10 that is stacked such that an Nd: YAG substrate is sandwiched between one YAG substrate 5 and another YAG substrate 7.

First, one surface 5a of one YAG substrate 5 is irradiated with Ar plasma, and one surface 6a of the Nd: YAG substrate 6 is irradiated with O ₂ plasma (step S1). Next, the one surface 5a of one YAG substrate 5 and the one surface 6a of the Nd: YAG substrate 6 are pasted and temporarily joined. Subsequently, O ₂ plasma is irradiated to the other surface 6b of the Nd: YAG substrate 6, and Ar plasma is irradiated to one surface 7a of the other YAG substrate 7 (step S10).

  Next, the one surface 7a of the other YAG substrate 7 and the other surface 6b of the Nd: YAG substrate 6 are pasted and temporarily joined (step S20). Thereafter, the YAG substrate 5, the Nd: YAG substrate, and the other YAG substrate 7 that are temporarily bonded are heated and bonded (step S3). In this way, the substrate 10 laminated so that the Nd: YAG substrate is sandwiched between the one YAG substrate 5 and the other YAG substrate 7 is manufactured. Thereby, for example, a laser element in which an Nd-added YAG crystal is sandwiched between non-added YAG crystals can be manufactured. This laser element can be manufactured with a high yield because there are few voids at the bonding interface.

  According to the method for manufacturing the substrate 10 of the present embodiment, at least one of the first substrate and the second substrate may include an optical crystal. For this reason, in a laser element or the like in which at least one of the first substrate and the second substrate 2 includes an optical crystal, generation of voids (bubbles) can be suppressed in the heating process after temporary bonding. This laser element can be manufactured with a high yield because there are few voids at the bonding interface.

Each of the above embodiments can be combined as appropriate.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 1st substrate, 2nd substrate, 3 quartz substrate, 4 GaAs substrate, 5 YAG substrate, 6 Nd: YAG substrate, 7 other YAG substrate, 10 substrate.

Claims (5)

A method of manufacturing a substrate in which a first substrate and a second substrate are bonded,
Preparing the first substrate having one surface irradiated with rare gas plasma and the second substrate having one surface irradiated with oxygen plasma and having higher hydrophilicity than one surface of the first substrate; When,
Bonding the first and second substrates together in the atmosphere and temporarily bonding the one surface of the first substrate and the one surface of the second substrate facing each other;
Heating and bonding the first substrate and the second substrate in the temporarily bonded state ;
Pressing the first substrate and the second substrate in the temporarily bonded state,
The step of heating and bonding includes a step of heating the first substrate and the second substrate in a pressurized state in a state where the pressure is returned to no pressure .   The method of manufacturing a substrate according to claim 1, wherein the rare gas plasma is any one of argon plasma, krypton plasma, and xenon plasma. The first is one at least a substrate and the second substrate comprises a semiconductor crystal, a manufacturing method of a substrate according to claim 1 or 2. The first is one at least a substrate and the second substrate comprises an oxide material, method for manufacturing a substrate according to claim 1 or 2. The first is one at least a substrate and said second substrate includes an optical crystal, manufacturing method of a substrate according to claim 1 or 2.

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