JP2008260639A - Method of bonding base material to be bonded, and method of manufacturing thin quartz substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of bonding substrates capable of directly bonding the substrates each other by decreasing generation of stresses such as a processing stress and a residual stress caused by different coefficients of linear expansion or different thicknesses between a quartz substrate and a base material containing silicone dioxide, and capable of securing flatness of a directly bonded substrate to make it thin, and a method of manufacturing a thin quartz substrate using the same. <P>SOLUTION: Stable siloxane bonds are formed between the quartz substrate 10 and the base material 20 containing silicone dioxide by wetting a smooth surface of the quartz substrate 10 and a smooth surface of the base material 20 containing silicon dioxide with a liquid containing hydrofluoric acid, and heating from a low temperature and holding without abruptly heating under the condition that the smooth surfaces are pressed each other so that the quartz substrate 10 is directly bonded with the base material 20. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for bonding a bonding substrate made of a silicon dioxide-containing substrate and a method for producing a thin quartz substrate using the same.

  Conventionally, as a method for thinning a silicon dioxide-containing substrate, a method for producing a thin substrate by polishing is often used. A thin substrate thinned by polishing processing has difficulty in ensuring flatness, and warpage occurs due to processing stress due to polishing processing. For this reason, plasma processing is performed on the surfaces of the two substrates, a bonded base material in which the surfaces are directly bonded to each other at a high temperature is created, and one substrate of the bonded base material is polished, thereby thin substrate Has been proposed (see, for example, Patent Document 1).

JP-A-2006-276313 (pages 3 to 5, FIGS. 1 to 2)

  In the manufacturing method of Patent Document 1, since the substrates are formed by directly bonding the substrates at a high temperature of 300 ° C. or higher, the thicknesses or linear expansion coefficients of the substrates are different. Residual stress occurs in the bonded substrate during the shrinkage that occurs. There is a problem that defects such as generation of warpage, breakage, or peeling of a bonded substrate occur due to generation of residual stress. Moreover, when thinning the board | substrate of the bonding apparatus in which curvature generate | occur | produced by grinding process, it is difficult to ensure flatness. Furthermore, a processing stress is also generated in a thin substrate obtained by thinning a bonded base material in which a residual stress is generated by polishing. For this reason, there exists a problem that the thin board | substrate which the residual stress and the processing stress generate | occur | produced will generate | occur | produce defects, such as damage of the board | substrate which bonded or the bonded board | substrate by the influence of stress.

  The present invention has been made paying attention to such conventional problems, and its purpose is to reduce the generation of residual stress and to directly bond the substrates to each other, and to generate processing stress on the directly bonded base materials. An object of the present invention is to provide a method for bonding substrates and a method for manufacturing a thin crystal substrate using the same, which can ensure flatness and reduce the thickness.

  In order to solve the above problems, in the bonding method of the bonding substrate of the present invention, the smooth surface of the quartz substrate and the smooth surface of the silicon dioxide-containing substrate are wetted with a hydrofluoric acid-containing liquid, and the smooth surfaces of each other Including a substrate pressing step for pressing the surfaces together to form a bonding substrate, a low temperature holding step for holding the bonding substrate at a low temperature, and a temperature rising holding step for raising the temperature from the low temperature and holding it at a high temperature. This is the gist.

  According to this, after the smooth surface of the quartz substrate and the smooth surface of the silicon dioxide-containing base material are wetted with the hydrofluoric acid-containing liquid, the smooth surfaces are pressed against each other so that the The acid-containing liquid can be uniformly diffused, and excess hydrofluoric acid-containing liquid is excluded from the surface. Therefore, the uniform diffusion of the hydrofluoric acid-containing liquid makes the siloxane bond generated between the surfaces uniform within the surface. In addition, since the temperature is maintained from a low temperature without abrupt heating and maintained at a high temperature, the reaction between the quartz substrate and the silicon dioxide-containing base material is stably accelerated, and a siloxane bond can be formed more completely. it can. The high temperature holding after the temperature rise can reduce the residual stress. Therefore, in the present invention, there is provided a bonding substrate bonding method capable of suppressing occurrence of defects such as warpage, breakage, or peeling due to residual stress, and capable of performing direct bonding with a uniform and stable siloxane bond. be able to.

  In the method for producing a thin quartz substrate of the present invention, the smooth surface of the quartz substrate and the smooth surface of the silicon dioxide-containing substrate are wetted with a hydrofluoric acid-containing solution, and the smooth surfaces are pressed against each other and bonded to each other. A substrate pressing step, a low temperature holding step for holding the bonding base material at a low temperature, a temperature rising holding step for raising the temperature from the low temperature and holding it at a high temperature, and thinning the quartz substrate of the bonding base material And a thin processing step for forming a thin quartz substrate.

  According to this, since it is possible to thin the bonded base material that does not have a defect such as warpage due to residual stress at the time of bonding, a thin quartz substrate that does not have a defect such as a decrease in flatness at the time of polishing is formed. It is possible to provide a method of manufacturing a thin quartz substrate that can be used.

  In the present invention, the thin processing step preferably includes a wet etching process.

  According to this, when the bonded base material is processed to be thin by wet etching, it is difficult for processing stress to occur as in the conventional polishing process. Accordingly, it is possible to suppress the occurrence of defects such as warpage due to processing stress, reduction in flatness, breakage, or peeling between the quartz substrate directly bonded to the silicon dioxide-containing base material on the thin quartz substrate.

  In the present invention, it is preferable to use a hydrofluoric acid-containing liquid in the thin processing step.

  According to this, thin processing with a high etch rate can be performed with the hydrofluoric acid-containing liquid. Therefore, it is possible to provide a method for manufacturing a thin crystal substrate capable of forming a thin crystal substrate by only a wet etching process using a hydrofluoric acid-containing liquid without adding a polishing process or the like that easily generates a processing stress.

  In the present invention, in the method for producing a thin quartz substrate, the silicon dioxide-containing substrate is preferably quartz.

  According to this, since the silicon dioxide-containing base material is the same material as the quartz substrate, the bonded base material in which the silicon dioxide-containing base material and the quartz substrate are directly joined can be processed thinner than both sides. Become. For this reason, it is possible to provide a method for manufacturing a thin crystal substrate capable of forming a thin crystal substrate composed of one or more crystal substrates by repeatedly performing direct bonding and thin processing. Further, when a corrosion-resistant film such as gold is provided on one side, only one side can be thinned. Also in this case, it is possible to provide a method for manufacturing a thin crystal substrate capable of forming a thin crystal substrate composed of one or more crystal substrates by repeatedly performing direct bonding and thin processing.

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

  FIG. 1 is a schematic side view showing a thin quartz substrate 1. FIG. 2 is a schematic side view showing the bonding substrate 21.

The thin quartz substrate 1 shown in FIG. 1 is formed by etching the processed surface 13 of the bonding base material 21 shown in FIG. Or it forms by etching both the process surface 13 and the process surface 23 of the bonding base material 21. FIG.
The bonding substrate 21 is formed by directly bonding the quartz substrate 10 and the silicon dioxide-containing substrate 20.

The quartz substrate 10 is formed by cutting out from a quartz crystal at an axial angle having a desired birefringence. The quartz substrate 10 has a processed surface 13 and a bonding surface 12 (see FIG. 3A) formed to face the processed surface 13. And the bonding surface 12 and the process surface 13 are mirror-finished.
The silicon dioxide containing base material 20 has the processed surface 23 and the bonding surface 22 (refer FIG. 3 (A)) formed facing the processed surface 23. FIG. And the bonding surface 22 and the process surface 23 are mirror-finished. The silicon dioxide-containing substrate 20 is a silicon wafer on which a bonding surface 22 made of silicon dioxide is formed, or quartz or quartz.
In the present embodiment, the quartz substrate 10 is formed in 30 mm × 30 mm and a thickness of 0.1 mm to 1.0 mm. The PV (Peak-Valley) value of the bonding surface 12 and the processed surface 13 is within 6 μm, and the thickness variation of the quartz substrate 10 is within 1 μm. The thickness of the quartz substrate 10 whose etched surface 13 has been etched is 0.15 μm. The silicon dioxide containing base material 20 is formed in 30 mm x 30 mm and thickness 0.1mm-1.3mm. The PV value of the bonding surface 22 and the processed surface 23 is within 2 μm.

The method for manufacturing a thin quartz substrate according to this embodiment includes a cleaning process, a substrate pressing process, a low temperature holding process, a temperature rising holding process, and a thin processing process. FIG. 3 is a schematic diagram illustrating an example of the substrate pressing step.
Below, the manufacturing method of a thin crystal substrate is demonstrated with reference to FIG.

First, in the cleaning process, the quartz substrate 10 and the silicon dioxide-containing base material 20 are wet-cleaned. Here, the foreign substance is removed from at least the bonding surface 12 and the bonding surface 22 by immersing the quartz substrate 10 and the silicon dioxide-containing base material 20 in a cleaning solution made of, for example, sulfuric acid and hydrogen peroxide solution for 2 minutes. To do. Moreover, the stain | pollution | contamination which consists of an inorganic substance etc. which are adhering to the bonding surface 12 and the bonding surface 22 at least is removed by using organic solvents, such as acetone.
Thereafter, the quartz substrate 10 and the silicon dioxide-containing base material 20 are cleaned using pure water. For example, as a method of cleaning using pure water, there is a method of immersing the quartz substrate 10 and the silicon dioxide-containing base material 20 in pure water for 30 minutes. Further, there is a method of applying pure water to the quartz substrate 10 and the silicon dioxide-containing base material 20 for 30 minutes. In the dipping method, the quartz substrate 10 and the silicon dioxide-containing base material 20 may be swung in pure water. Then, after washing, a drying process is performed. As a drying process, the natural drying process etc. which are dried by heat processing or air drying are mentioned as an example.

  In the substrate pressing step, as shown in FIG. 3A, the bonding surface 12 of the quartz substrate 10 and the bonding surface 22 of the silicon dioxide-containing base material 20 are opposed to each other so that the quartz substrate 10 and the silicon dioxide-containing substrate The material 20 is arranged facing each other.

  Then, as shown in FIG. 3B, the hydrofluoric acid layer is wetted with a hydrofluoric acid-containing liquid between the smooth surface of the quartz substrate 10 and the smooth surface of the silicon dioxide-containing base material 20 that are arranged facing each other. 30 is formed. For example, a method of forming the hydrofluoric acid layer 30 includes a method of dropping or injecting a hydrofluoric acid-containing liquid between the bonding surface 12 and the bonding surface 22. Moreover, the hydrofluoric acid containing liquid is dripped or apply | coated to the bonding surface 12 or the bonding surface 22, and the hydrofluoric acid containing liquid is pressed down by the bonding surface 12 and the bonding surface 22, and the hydrofluoric acid layer 30 is formed. There is. In the method of forming the hydrofluoric acid layer 30 by pressing in this manner, the hydrofluoric acid-containing liquid may be dropped or applied to both the bonding surface 12 and the bonding surface 22. Here, the quantity of the hydrofluoric acid containing liquid which forms the hydrofluoric acid layer 30 is suitably determined by the density | concentration of a hydrofluoric acid containing liquid, the component contained in a hydrofluoric acid containing liquid, the area of the bonding surface 12 or the bonding surface 22, etc. can do. The amount of the hydrofluoric acid-containing liquid in the hydrofluoric acid layer 30 can be adjusted by swinging off a spinner or the like.

As shown in FIG. 3C, a pressure of about 50 gf / cm ² is applied to the ^two parallel flat plates indicated by the two-dot chain line in the direction indicated by the arrow. This pressure is transmitted to the quartz substrate 10 and the silicon dioxide-containing base material 20 to press the quartz substrate 10 and the silicon dioxide-containing base material 20 together. Thereby, hydrofluoric acid contained in the hydrofluoric acid-containing liquid of the hydrofluoric acid layer 30 diffuses uniformly on the bonding surface 12 and the bonding surface 22, and silanol groups are bonded to the bonding surface 12 and the bonding surface 22. It is formed sufficiently and uniformly. Thus, the bonding base material 21 which consists of the quartz crystal substrate 10 and the silicon dioxide containing base material 20 is obtained. Here, the pressure applied in the direction indicated by the arrow can be appropriately determined depending on the material of the quartz substrate 10 and the silicon dioxide-containing base material 20, the concentration of the hydrofluoric acid-containing liquid, the components contained in the hydrofluoric acid-containing liquid, and the like. After applying pressure, the hydrofluoric acid-containing liquid unnecessary for bonding is discharged out of the bonding surface 12 and the bonding surface 22.

  The hydrofluoric acid-containing liquid used in the substrate pressing step is a commercially available hydrofluoric acid stock solution (50%), dilute hydrofluoric acid obtained by diluting a hydrofluoric acid stock solution (50%) with water to a concentration of 1%, for example, or hydrofluoric acid. And buffered hydrofluoric acid which is a mixed solution of ammonium fluoride and hydrofluoric acid. When a hydrofluoric acid stock solution (50%) or buffered hydrofluoric acid is used, a large amount of silicic acid or ammonium silicofluoride is generated, so that the direct bonding strength between the quartz substrate 10 and the silicon dioxide-containing substrate 20 is increased. May be reduced. However, since the pH is higher than that of hydrofluoric acid, buffered hydrofluoric acid is preferable from the viewpoint of safety. In terms of ensuring the bonding strength, it is preferable to use dilute hydrofluoric acid. In particular, it is more preferable to use dilute hydrofluoric acid having a concentration of 0.5% to 10%. In the substrate pressing process of this embodiment, dilute hydrofluoric acid with a concentration of 0.5%, dilute hydrofluoric acid with a concentration of 3%, or dilute hydrofluoric acid with a concentration of 10% is used.

A low temperature holding step is performed on the bonding base material 21 composed of the crystal substrate 10 and the silicon dioxide-containing base material 20. In addition, since the pressure is weighted and hold | maintained at the bonding base material 21, peeling of the bonding surface 12 and the bonding surface 22 or a position shift does not generate | occur | produce. Also in the low temperature holding process and the temperature rising holding process which will be described later, pressure is applied to the bonding base material 21 to hold it.
In the low temperature holding step, the bonded base material 21 is held at a low temperature of 10 ° C. or more and 30 ° C. or less within 15 hours or more and 36 hours or less. Thereby, silanol groups are sufficiently formed on the bonding surface 12 of the quartz substrate 10 and the bonding surface 22 of the silicon dioxide-containing base material 20.
By holding at a low temperature of 10 ° C. or higher and 30 ° C. or lower for 15 hours or longer, hydrofluoric acid contained in the hydrofluoric acid-containing liquid of the hydrofluoric acid layer 30 diffuses the bonding surface 12 and the bonding surface 22 and pastes. Silanol groups are sufficiently formed on the bonding surface 12 and the bonding surface 22. By holding a low temperature of 10 ° C. or higher and 30 ° C. or lower within 36 hours, water contained in the hydrofluoric acid-containing liquid of the hydrofluoric acid layer 30 is exposed from between the quartz substrate 10 and the silicon dioxide-containing base material 20. This prevents excessive volatilization from the surface of the hydrofluoric acid layer 30 and suppresses dehydration condensation between silanol groups. Furthermore, the volatile silicon tetrafluoride produced | generated in reaction with the silicon dioxide of the bonding surface 12 and the bonding surface 22 and hydrofluoric acid contained in a hydrofluoric acid containing liquid can be removed. Silicon tetrafluoride reacts with water to produce by-products silicic acid and hydrogen silicofluoride, and reacts with hydrofluoric acid to produce by-product hydrogen silicofluoride. Therefore, by reducing the amount of silicon tetrafluoride, the chemical reaction between silicon tetrafluoride, hydrofluoric acid and water in the hydrofluoric acid-containing liquid is suppressed, and the production of by-products is reduced. . From this, it is possible to form a silanol group uniformly on the bonding surface 12 and the bonding surface 22 and obtain sufficient bonding strength.
The low-temperature holding time in the low-temperature holding step can be appropriately determined according to the materials of the quartz substrate 10 and the silicon dioxide-containing base material 20, the concentration and contents of the hydrofluoric acid-containing liquid, or the like. Moreover, you may control the volatilization rate of a hydrofluoric acid containing liquid by adjusting humidity.

After the low temperature holding step, the temperature rising holding step is performed on the bonding base material 21 composed of the quartz substrate 10 and the silicon dioxide-containing base material 20. In addition, it is preferable that the pressure is applied to the bonding base material 21.
In the temperature raising bonding step, the quartz substrate 10, the silicon dioxide-containing base material 20, and the hydrofluoric acid layer 30 are heated from a low temperature of 10 ° C. to 30 ° C. to 45 ° C. to 200 ° C. and held. The temperature rising rate is set to 2 ° C./5 minutes, for example. And the temperature is raised and held for 6 hours or more and 36 hours or less. Thereby, as shown in FIG. 2, the bonding base material 21 with which the crystal substrate 10 and the silicon dioxide containing base material 20 were directly joined is formed.

  By raising the temperature from a low temperature of 10 ° C. to 30 ° C. over a period of 6 hours at a rate of temperature increase of 2 ° C./5 minutes and holding at 45 ° C. The temperature of the acid layer 30 is increased uniformly. Thereby, water contained in the hydrofluoric acid-containing liquid of the hydrofluoric acid layer 30 is gradually volatilized, and dehydration condensation occurs uniformly between the silanol groups formed on the bonding surface 12 and the bonding surface 22. Further, by volatilizing silicon tetrafluoride and water as by-products generated in the low temperature holding step, chemical reaction between silicon tetrafluoride and water, and fluorine in the liquid containing silicon tetrafluoride and hydrofluoric acid are obtained. In order to suppress the chemical reaction with hydrofluoric acid and reduce the production of by-products, dehydration condensation occurs uniformly between the silanol groups formed on the bonding surface 12 and the bonding surface 22. Thereby, a stable siloxane bond is uniformly formed, and a bonded base material 21 in which the quartz crystal substrate 10 and the silicon dioxide-containing base material 20 are directly and uniformly bonded by the siloxane bond is formed. And if it is within 36 hours, a siloxane bond will fully be formed between the bonding surface 12 and the bonding surface 22, and the bonding base material 21 can be obtained. If it is 200 degrees C or less, the residual stress which generate | occur | produces that a linear expansion coefficient or thickness differs will be suppressed, and the crystal | crystallization board | substrate 10 or the silicon dioxide containing base material 20 or the bonding base material 21 will be warped or damaged by a residual stress. Suppresses the occurrence of defects. In addition, the temperature increase rate in the temperature increase holding step and the time for holding the temperature increased can be appropriately determined depending on the material of the quartz substrate 10 and the silicon dioxide-containing base material 20, the concentration and contents of the hydrofluoric acid-containing liquid, and the like. . Moreover, you may control the volatilization rate of a hydrofluoric acid containing liquid by adjusting humidity.

In the thin processing step, at least one of the processed surface 13 and the processed surface 23 is subjected to a wet etching process by immersing the bonded base material 21 in an etching solution, and the bonded base material 21 is processed into a thin shape. Thereby, the thin quartz substrate 1 shown in FIG. 1 is obtained. Here, when the processed surface 23 is not subjected to wet etching, a chromium adhesion layer and a gold corrosion-resistant film are sequentially formed on the processed surface 23 to cover the processed surface 23. After the wet etching process, the chromium adhesion layer and the gold corrosion resistant film formed on the processed surface 23 are removed.
Etching solution is hydrofluoric acid stock solution (50%), hydrofluoric acid stock solution (50%) diluted with water to a concentration of 25%, for example, or a solution of ammonium fluoride and hydrofluoric acid. A hydrofluoric acid-containing liquid such as a buffered hydrofluoric acid liquid that is a mixed liquid can be used. In order to prevent problems such as the product produced differs depending on the materials of the quartz substrate 10 and the silicon dioxide-containing base material 20 that are directly bonded and precipitates on the processing surface in the etching solution, sulfuric acid, hydrochloric acid, phosphoric acid It is possible to mix acids such as nitric acid, acetic acid, succinic acid and / or surfactants. In addition, it is preferable to control the etching rate while keeping the temperature of the etching solution constant. Furthermore, a method of ensuring in-plane uniformity by a method of swinging the bonding substrate 21 in the etching solution or circulating the etching solution is also preferable. In the thin processing step of this embodiment, a buffered hydrofluoric acid solution is used. After the wet etching process, the thickness of the quartz substrate 10 forming the thin quartz substrate 1 is 15 μm.

In the thin processing step, the bonding substrate 21 is disposed on the surface plate, and the bonding substrate 21 is polished. Thereby, the thin crystal substrate 1 in which at least one of the processed surface 13 and the processed surface 23 is processed to be thin is obtained. The thickness of the quartz substrate 10 after polishing is 15 μm.
Alternatively, the quartz substrate 10 after wet etching is polished to obtain the thin quartz substrate 1 shown in FIG. Thereby, etch pits or cloudiness generated on at least one of the processed surface 13 and the processed surface 23 is removed by wet etching. After wet etching and polishing, the thickness of the quartz substrate 10 forming the thin quartz substrate 1 is 15 μm.

Examples 1 to 8 of this embodiment will be described below.
Example 1

Example 1 of the present invention will be described below.
The silicon dioxide-containing substrate 20 is quartz. The thickness of the quartz substrate 10 is 0.1 mm, and the thickness of the silicon dioxide-containing base material 20 is 1.3 mm.
The manufacturing method of Example 1 uses 3% dilute hydrofluoric acid as the hydrofluoric acid-containing liquid in the substrate pressing step. And the manufacturing method of Example 1 includes a substrate pressing step, a low temperature holding step, a temperature rising holding step, and a thin processing step.

  The substrate pressing process is performed in the order of FIGS. 3A, 3B, and 3C, and the hydrofluoric acid layer 30 made of 3% dilute hydrofluoric acid is formed by the quartz substrate 10 and the silicon dioxide-containing base material 20. Press down.

  In the low temperature holding step, the quartz substrate 10, the silicon dioxide-containing base material 20, and the hydrofluoric acid layer 30 are kept at a low temperature of 10 ° C. while the hydrofluoric acid layer 30 is pressed by the quartz substrate 10 and the silicon dioxide-containing base material 20. For 24 hours.

  In the temperature rising and holding step, the quartz substrate 10, the silicon dioxide-containing base material 20 and the hydrofluoric acid layer 30 are heated from a low temperature of 10 ° C. to 60 ° C. at a temperature rising rate of 2 ° C./5 minutes to 60 ° C. Hold. The time for raising the temperature and holding it is 24 hours. Thereby, as shown in FIG. 2, the bonding base material 21 with which the crystal substrate 10 and the silicon dioxide containing base material 20 were directly joined is formed.

In the thin processing step, wet etching treatment is performed on the processed surface 13 and the processed surface 23 of the bonding base material 21 using buffered hydrofluoric acid, which is a mixed solution of ammonium fluoride and hydrofluoric acid, as an etching solution. Apply. Thereby, the bonding base material 21 is processed into a thin shape, and the thin crystal substrate 1 shown in FIG. 1 is obtained. Here, the thickness of the quartz substrate 10 forming the thin quartz substrate 1 is 15 μm. In addition, the quartz substrate 10 is a part of the bonding substrate 21 after the substrate pressing step, and in the description of the present application, the thickness of the quartz substrate 10 means the thickness of the quartz substrate 10 portion of the bonding substrate 21 for convenience. To do.
(Example 2)

The second embodiment of the present invention will be described below.
The materials and thicknesses of the quartz substrate 10 and the silicon dioxide-containing substrate 20 are the same as those in the first embodiment.
In the manufacturing method of Example 2, a wet etching process is performed using a hydrofluoric acid solution diluted to a concentration of 25% as an etchant in a thin processing step. Thereafter, polishing is performed. Since the substrate pressing step, the low temperature holding step, and the temperature rising holding step are performed according to the same procedures and conditions as in the first embodiment, description thereof is omitted.

  In the thin processing step, a wet etching process is performed on the processed surface 13 and the processed surface 23 of the bonding substrate 21 using a hydrofluoric acid solution diluted to a concentration of 25% as an etching solution.

The quartz substrate 10 after the wet etching process is polished to obtain a thin quartz substrate 1 shown in FIG. Here, the thickness of the quartz substrate 10 forming the thin quartz substrate 1 is 15 μm.
(Example 3)

Example 3 of the present invention will be described below.
The thin processing step is characterized in that a chromium adhesion layer and a gold corrosion-resistant film are sequentially formed on the silicon dioxide-containing base material 20 and only the processed surface 13 of the quartz substrate 10 is subjected to wet etching. The material and thickness of the quartz substrate 10 constituting the thin quartz substrate 1 and the material of the silicon dioxide-containing substrate 20 are the same as those in the first embodiment. Since the substrate pressing step, the low temperature holding step, and the temperature rising holding step are performed according to the same procedures and conditions as in the first embodiment, description thereof is omitted.

In the thin processing step, on the processed surface 23 of the bonding substrate 21, a chromium adhesion layer and a gold corrosion-resistant film are sequentially formed, and the processed surface 13 of the bonding substrate 21 is covered with the processed surface 23. And wet etching treatment. After the wet etching process, the chromium adhesion layer and the gold corrosion resistant film are removed. Thereby, the bonding base material 21 is processed into a thin shape, and the thin crystal substrate 1 shown in FIG. 1 is obtained. Here, the thickness of the quartz substrate 10 forming the thin quartz substrate 1 is 15 μm.
Example 4

The fourth embodiment of the present invention will be described below.
The materials and thicknesses of the quartz substrate 10 and the silicon dioxide-containing substrate 20 are the same as those in the first embodiment.
The production method of Example 4 is characterized in that the low temperature holding step is performed at 30 ° C. for 15 hours, and the temperature rising holding step is performed at 200 ° C. for 6 hours. The substrate pressing process and the thinning process are performed according to the same procedures and conditions as those in the first embodiment, and thus description thereof is omitted.

  In the low temperature holding step, the quartz substrate 10, the silicon dioxide-containing base material 20, and the hydrofluoric acid layer 30 are kept at a low temperature of 30 ° C. while the hydrofluoric acid layer 30 is pressed by the quartz substrate 10 and the silicon dioxide-containing base material 20. And hold for 15 hours.

  In the temperature rising and holding step, the quartz substrate 10, the silicon dioxide-containing base material 20, and the hydrofluoric acid layer 30 are heated from a low temperature of 30 ° C. to 200 ° C. at a temperature rising rate of 2 ° C./5 minutes to 200 ° C. Hold. The time for raising the temperature and holding it is 6 hours. Thereby, as shown in FIG. 2, the bonding base material 21 with which the crystal substrate 10 and the silicon dioxide containing base material 20 were directly joined is formed.

By carrying out the thinning process in the same manner as in Example 1, the bonding substrate 21 is thinned to obtain the thin quartz substrate 1 shown in FIG. Here, the thickness of the quartz substrate 10 forming the thin quartz substrate 1 is 15 μm.
(Example 5)

The fifth embodiment of the present invention will be described below.
The materials and thicknesses of the quartz substrate 10 and the silicon dioxide-containing substrate 20 are the same as those in the first embodiment.
The manufacturing method of Example 5 is characterized in that the temperature rising and holding step is performed at 45 ° C. for 36 hours. The substrate pressing step, the low temperature holding step, and the thinning step are performed according to the same procedures and conditions as those in the first embodiment, and thus description thereof is omitted.

  In the temperature rising and holding step, the quartz substrate 10, the silicon dioxide-containing base material 20, and the hydrofluoric acid layer 30 are heated from a low temperature of 10 ° C. to 45 ° C. at a temperature rising rate of 2 ° C./5 minutes to 45 ° C. Hold. The time for raising the temperature and holding it is 36 hours. Thereby, as shown in FIG. 2, the bonding base material 21 with which the crystal substrate 10 and the silicon dioxide containing base material 20 were directly joined is formed.

By carrying out the thinning process in the same manner as in Example 1, the bonding substrate 21 is thinned to obtain the thin quartz substrate 1 shown in FIG. Here, the thickness of the quartz substrate 10 forming the thin quartz substrate 1 is 15 μm.
(Example 6)

The sixth embodiment of the present invention will be described below.
Unlike Example 1, the material and thickness of the silicon dioxide-containing substrate 20 are characterized in that the material is quartz and the thickness is 0.1 mm. The manufacturing method of Example 7 is characterized in that the hydrofluoric acid-containing liquid used in the substrate pressing step is 10% dilute hydrofluoric acid.
The material and thickness of the quartz substrate 10 constituting the thin quartz substrate 1 are the same as those in the first embodiment. Moreover, since the low temperature holding process, the temperature rising holding process, and the thinning process are performed according to the same procedures and conditions as in the first embodiment, the description thereof is omitted.

By carrying out the thinning process in the same manner as in Example 1, the bonding substrate 21 is thinned to obtain the thin quartz substrate 1 shown in FIG. Here, the thickness of the quartz substrate 10 forming the thin quartz substrate 1 is 15 μm.
(Example 7)

The seventh embodiment of the present invention will be described below.
Unlike Example 1, the material and thickness of the silicon dioxide-containing base material 20 are characterized in that a silicon oxide film is formed at least on the bonding surface 22.
In the manufacturing method of Example 7, the hydrofluoric acid-containing liquid used in the substrate pressing step is 0.5% dilute hydrofluoric acid, and the wet etching process is performed on the processed surface 13 of the bonding substrate 21 in the thin processing step. There is a special feature. Since the substrate pressing step, the low temperature holding step, and the temperature rising holding step are performed according to the same procedures and conditions as in the first embodiment, description thereof is omitted.

In the thin processing step, on the processed surface 23 of the bonding substrate 21, a chromium adhesion layer and a gold corrosion-resistant film are sequentially formed, and the processed surface 13 of the bonding substrate 21 is covered with the processed surface 23. And wet etching treatment. After the wet etching process, the chromium adhesion layer and the gold corrosion resistant film are removed. Thereby, the bonding base material 21 is processed into a thin shape, and the thin crystal substrate 1 shown in FIG. 1 is obtained. Here, the thickness of the quartz substrate 10 forming the thin quartz substrate 1 is 15 μm.
(Example 8)

The eighth embodiment of the present invention will be described below.
The manufacturing method of Example 8 is characterized in that only polishing is performed in the thin processing step.
The thicknesses of the quartz substrate 10 and the silicon dioxide-containing base material 20 are the same as those in the first embodiment. The hydrofluoric acid-containing liquid used in the substrate pressing step is 3% hydrofluoric acid as in Example 1. Since the low temperature holding step and the temperature rising holding step are performed according to the same procedure and conditions as in Example 1, the description thereof is omitted.

  In the thin processing step, single-side polishing is performed on the processed surface 13 of the bonding substrate 21. Thereby, the bonding base material 21 is processed into a thin shape, and the thin crystal substrate 1 shown in FIG. 1 is obtained. Here, the thickness of the quartz substrate 10 forming the thin quartz substrate 1 is 15 μm.

Hereinafter, Comparative Examples 1 to 4 will be described.
(Comparative Example 1)

In Comparative Example 1, the material and thickness of the quartz substrate 10 and the silicon dioxide-containing base material 20 are the same as those in Example 1.
The manufacturing method of Comparative Example 1 is that in the manufacturing method of the thin crystal substrate according to Example 1, the thin crystal substrate 1 is manufactured by directly joining by a wet process using a hydrofluoric acid-containing liquid. The thin crystal substrate 1 is manufactured by subjecting the bonding surface 12 and the bonding surface 22 of the silicon dioxide-containing base material 20 to plasma treatment, and directly bonding the bonding surface 12 and the bonding surface 22 at a high temperature. carry out.
(Comparative Example 2)

In Comparative Example 2, the material of the silicon dioxide-containing substrate 20 is quartz. The thickness of the silicon dioxide-containing substrate 20 and the material and thickness of the quartz substrate 10 are the same as in Comparative Example 1.
Since the manufacturing method of Comparative Example 2 is performed according to the same procedure and conditions as Comparative Example 1, description thereof is omitted. By carrying out similarly to Example 1 in a thin processing process, the bonding base material 21 with which the crystal substrate 10 and the silicon dioxide containing base material 20 were directly joined is processed into a thin shape, and the thin crystal substrate 1 shown in FIG. Get. Here, the thickness of the quartz substrate 10 forming the thin quartz substrate 1 is 15 μm.
(Comparative Example 3)

In Comparative Example 3, the material and thickness of the quartz substrate 10 and the silicon dioxide-containing base material 20 are the same as those in Example 1.
In the production method of Comparative Example 3, the low temperature holding step is performed at 5 ° C. for 2 hours, and the temperature rising holding step is performed at 30 ° C. for 5 hours. The substrate pressing process and the thinning process are performed according to the same procedures and conditions as those in the first embodiment, and thus description thereof is omitted.
(Comparative Example 4)

In Comparative Example 4, the material and thickness of the quartz substrate 10 and the silicon dioxide-containing base material 20 are the same as those in Example 1.
In the manufacturing method of Comparative Example 4, the low temperature holding step and the temperature rising holding step are performed as one step, and the process is performed at 100 ° C. for 15 hours. The substrate pressing process and the thinning process are performed according to the same procedures and conditions as those in the first embodiment, and thus description thereof is omitted.
In the thin processing step, single-side polishing is performed on the processed surface 13 of the bonding substrate 21. Thereby, the bonding base material 21 is processed into a thin shape, and the thin crystal substrate 1 shown in FIG. 1 is obtained. Here, the thickness of the quartz substrate 10 forming the thin quartz substrate 1 is 15 μm.

Here, evaluation shown below was performed about the bonding base material 21 of the above-mentioned Examples 1-8 and Comparative Examples 1-4 and the thin quartz substrate 1 which processed this thinly. The evaluation items were three items: the warping condition of the bonding base material 21, the appearance of the thin quartz substrate 1, and the thickness variation condition.
Hereinafter, an evaluation method for each evaluation item will be described.

(1) Warpage condition evaluation method.
The shape of the processed surface 13 of the quartz substrate 10 that forms the bonded base material 21 is measured using a surface shape measuring instrument (Form Talysurf), and a value obtained by subtracting the minimum value from the maximum value of the measured value is shown.

(2) Appearance evaluation method.
Appearance evaluation was visually observed under a fluorescent lamp. Appearance quality evaluation was divided into the following two stages and evaluated.
○: No cracks, breakage, or direct bonding peeling was confirmed, and an excellent appearance was obtained.
X: Crack, breakage, or peeling of direct bonding was confirmed, and the appearance was poor.

(3) Thickness variation evaluation method.
The thickness of the quartz substrate 10 that forms the thin quartz substrate 1 is measured at nine locations using an optical thickness measuring instrument, and a value obtained by subtracting the minimum value from the maximum value of the measured value is shown. In addition, in the above-described (2) appearance evaluation method, the thin quartz substrate 1 evaluated as having a poor appearance was not subjected to a thickness variation evaluation, and measurement was impossible.
The results of the above evaluation are shown in Table 1.

  Compared to the bonding base material 21 of Comparative Examples 2 to 4, the bonding base material 21 of Examples 1 to 9 is excellent because the warping condition of the bonding base material 21 is small, and the thinness of Comparative Examples 1 to 4. Compared to the processed thin crystal substrate 1, the thin processed thin crystal substrate 1 of Examples 1 to 7 and 9 is excellent in both appearance and thickness variation of the crystal substrate 10 forming the thin crystal substrate 1. Can be confirmed. Since the thin quartz substrate 1 of Example 8 is made of a silicon wafer, the thickness variation of the quartz substrate 10 forming the thin quartz substrate 1 cannot be measured using an optical thickness meter.

  Therefore, according to the present embodiment, the smooth surface of the quartz substrate 10 and the smooth surface of the silicon dioxide-containing base material 20 are wetted with the hydrofluoric acid-containing liquid, and the smooth surfaces are pressed against each other rapidly. Therefore, a stable siloxane bond can be uniformly formed between the quartz crystal substrate 10 and the silicon dioxide-containing base material 20. Thereby, the crystal substrate 10 and the silicon dioxide-containing base material 20 are directly bonded to each other by reducing the generation of residual stress caused by the difference in the linear expansion coefficient or thickness between the quartz substrate 10 and the silicon dioxide-containing base material 20. Therefore, it is possible to provide a method for bonding substrates. Therefore, warpage due to residual stress occurs in the directly bonded crystal substrate 10 and the silicon dioxide-containing base material 20, breakage, or peeling between the directly bonded crystal substrate 10 and the silicon dioxide-containing base material 20. It is possible to suppress the occurrence of defects.

  Moreover, in this embodiment, since the bonding base material 21 which does not have malfunctions, such as generation | occurrence | production of the curvature by a residual stress, is thin-processed, it becomes possible to form the thin quartz substrate 1 without malfunctions, such as a flatness fall. A method for manufacturing a thin quartz substrate can be provided.

  Moreover, in this embodiment, since the bonding base material 21 is thinly processed by wet etching processing that does not generate processing stress, the thin quartz substrate 1 can be processed without causing warpage due to processing stress.

  In this embodiment, thin processing with a high etch rate can be performed with a hydrofluoric acid-containing liquid. Therefore, it is possible to form the thin quartz substrate 1 by thinly processing the bonding base material 21 only by the wet etching process using the hydrofluoric acid-containing liquid without adding a polishing process or the like that easily generates a processing stress. A method for manufacturing a quartz substrate can be provided.

Moreover, in this embodiment, since the silicon dioxide containing base material 20 is the same material as the quartz substrate 10, the quartz substrates 10 can be directly joined and processed thinly. For this reason, it is possible to provide a method of manufacturing a thin crystal substrate capable of forming a multilayer thin crystal substrate composed of two or more crystal substrates 10 by repeatedly performing direct bonding and thin processing.
Furthermore, in this embodiment, a corrosion resistant film is provided on the silicon dioxide-containing base material 20, and one or more multilayer thin crystal substrates are formed by repeatedly performing thin processing and direct bonding on the processed surface 13 of the crystal substrate 10. It is possible to provide a method of manufacturing a thin quartz substrate that can be used.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the above-described embodiment, it has been described that the wet etching process in the thin processing step is performed on either the processed surface 13 or the processed surface 23 of the bonded substrate 21, but the contact is made in contact with the processed surface 13 and the processed surface 23. A wet etching process may also be performed on the side surface on which the composite substrate 21 is formed.

1 is a schematic side view showing a thin quartz substrate according to an embodiment of the present invention. The schematic side view which shows the bonding base material concerning embodiment of this invention. Schematic which shows an example of the board | substrate pressing process concerning embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Thin quartz substrate, 10 ... Quartz substrate, 12 ... Bonding surface, 13 ... Processing surface, 20 ... Substrate containing silicon dioxide, 21 ... Bonding substrate, 22 ... Bonding surface, 23 ... Processing surface, 30 ... Hydrofluoric acid layer.

Claims (5)

A substrate pressing step in which a smooth surface of a quartz substrate and a smooth surface of a silicon dioxide-containing substrate are wetted with a hydrofluoric acid-containing liquid, and the smooth surfaces are pressed together to form a bonded substrate;
A low temperature holding step for holding the bonding substrate at a low temperature;
A method for bonding a bonding substrate, comprising: a temperature rising and holding step in which the temperature is raised from the low temperature and held at a high temperature. A substrate pressing step in which the smooth surface of the quartz substrate and the smooth surface of the silicon dioxide-containing substrate are wetted with a hydrofluoric acid-containing liquid, and the smooth surfaces are pressed together to form a bonded substrate;
A low temperature holding step for holding the bonding substrate at a low temperature;
A temperature raising and holding step of raising the temperature from the low temperature and holding it at a high temperature;
A thin crystal substrate manufacturing method comprising: forming a thin crystal substrate by thin processing the crystal substrate of the bonding base material. In the manufacturing method of the thin crystal substrate of Claim 2,
The method for manufacturing a thin crystal substrate, wherein the thin processing step includes a wet etching process. In the manufacturing method of the thin crystal substrate of Claim 3,
In the thin processing step, a hydrofluoric acid-containing liquid is used. In the manufacturing method of the thin crystal substrate as described in any one of Claims 2-4,
The method for producing a thin quartz substrate, wherein the silicon dioxide-containing substrate is quartz.

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