JP5628530B2 - Support substrate for bonded substrate and manufacturing method thereof - Google Patents

Description

  The present invention relates to a support substrate for a bonded substrate and a manufacturing method thereof.

  Conventionally, single crystal wafers made of single crystals have been widely used as substrates for semiconductor devices such as next-generation LED devices, power devices, and high-frequency devices (see, for example, Patent Document 1). This single crystal wafer has excellent characteristics, but has a problem that the manufacturing method is complicated and expensive. In recent years, the single crystal wafer is configured by bonding a thin film single crystal wafer and a supporting substrate. Bonded substrates have been developed. For example, a silicon carbide sintered body formed by hot pressing is used for the support substrate.

JP 2005-8472 A

  However, since the silicon carbide sintered body formed by the hot press has a recess formed on the surface and a cavity connected to the surface is formed inside, the surface of the silicon carbide sintered body is polished to some extent. However, the recesses and cavities do not disappear and a smooth surface cannot be obtained. Therefore, even if this silicon carbide sintered body is used as a support substrate and the surface of the silicon carbide sintered body is bonded to the single crystal wafer, there is a gap between the surface of the silicon carbide sintered body and the single crystal wafer. As a result, the bonding strength between the two may not be sufficient.

  As a method for bonding the single crystal wafer and the support substrate, there is a method of bonding without using an adhesive. Specific examples include a heat and pressure bonding method, a surface activated bonding method by irradiating the bonded surface with an ion beam, and a bonding method via a hydrophilic group by a hydrophilic treatment. In such a bonding method that does not use an adhesive material, it is necessary to bring the bonding surfaces close to the atomic size level (1 nm) in order to use the attractive force between atoms.

  Accordingly, an object of the present invention is to provide a support substrate for a bonded substrate and a method for manufacturing the same, in which the bonding surface of the support substrate constituting the bonded substrate has high smoothness and the bonding strength with the single crystal wafer is improved. It is in.

In order to solve the above-described problems, the present invention has the following features. A method for manufacturing a support substrate according to the present invention is a method for manufacturing a support substrate to be bonded to a single crystal wafer made of a single crystal , and is a porous silicon carbide having a density of 2.3 to 3.0 g / cm ^3. A step of impregnating a plurality of voids in the sintered body with molten silicon, a step of cooling and solidifying the molten silicon, and a surface of the silicon carbide sintered body by chemical mechanical polishing, an arithmetic average roughness of 1 nm or less And a step of forming a bonding surface with the single crystal wafer .
In addition, the support substrate according to the present invention includes a silicon carbide sintered body having a plurality of communicating voids and silicon filled in the voids, and has a smooth bonding surface bonded to the single crystal wafer. It is a board | substrate, manufactured by the manufacturing method of the support substrate of the said Claim 1, the density of a silicon carbide sintered compact is 2.3-3.0 g / cm < ³ > , and it affixes on the said single crystal wafer. The gist is that the arithmetic average roughness of the joined surfaces to be combined is 1 nm or less.

  According to the present invention, the support substrate includes a silicon carbide sintered body having a plurality of communicating voids and silicon filled in the voids, and the bonding surface of the support substrate bonded to the single crystal wafer is smooth. is there. Since the voids of the silicon carbide sintered body are filled with silicon and have no gaps, the bonding surface with the single crystal wafer can be formed on a smooth surface without voids such as irregularities and cavities. . Therefore, since the bonding surface of the support substrate of the present invention is smoother than a support substrate made of a normal silicon carbide sintered body, the bonding strength between the silicon carbide sintered body and the single crystal wafer can be increased. it can.

  According to the bonded substrate support substrate of the present invention, the smoothness of the bonding surface with the single crystal wafer is improved, so that the bonding strength between the single crystal wafer and the support substrate can be increased.

It is a perspective view which shows the bonding board | substrate which concerns on embodiment of this invention. It is a perspective view which shows the support substrate of FIG. It is sectional drawing which shows the manufacturing process of the support substrate which concerns on embodiment of this invention, (a) is sectional drawing of the silicon carbide sintered compact before a process, (b) is silicon carbide baking which made the space | gap impregnated with molten Si. FIG. 4C is a cross-sectional view of a support substrate having a bonded surface formed by polishing the surface.

  Hereinafter, the details of the bonded substrate support substrate according to the embodiments of the present invention will be described with reference to the drawings. Specifically, (1) the overall configuration of the bonded substrate, (2) the manufacturing process of the bonded substrate support substrate, and (3) the operational effects will be described. It should be noted that the drawings are schematic, and the thicknesses and ratios of the material layers are different from actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Also included in the drawings are portions having different dimensional relationships and ratios.

(1) Overall Configuration of Bonded Substrate First, the overall configuration of the bonded substrate 1 will be described with reference to FIGS. FIG. 1 is a perspective view of a bonded substrate 1 according to an embodiment of the present invention, and FIG. 2 is a perspective view showing a support substrate 3 of FIG. As shown in FIG. 1, the bonded substrate 1 according to the present embodiment is formed in a substantially disk shape, and a support substrate 3 disposed on the lower side and a single crystal bonded to the upper surface of the support substrate 3. And a wafer 5.

  The single crystal wafer 5 is a single crystal wafer made of a single crystal. Specifically, it is made of a single crystal such as Si, SiC, GaN, or AlN. The single crystal wafer 5 is manufactured separately from the support substrate 3 and then bonded to the support substrate 5 with an adhesive or the like, whereby the bonded substrate 1 is formed.

  As shown in FIG. 2, the support substrate 3 is formed in a disk shape. The support substrate 3 includes a bonding surface 6 with the single crystal wafer 5 formed on the upper surface side, a back surface 9 positioned on the opposite side of the bonding surface 6, and a side surface 11 connecting the bonding surface 6 and the back surface 9. The side surface 11 is a side surface of the support substrate 3. In addition, the support substrate 3 includes a silicon carbide sintered body 21 having a plurality of communicating voids 23 and cavities 25, and silicon 27 filled in the voids. The bonding surface 6 is a surface bonded to the single crystal wafer 5 by an adhesive or the like, and is formed on the smooth surfaces 31 and 33 (see FIG. 3) having an arithmetic average roughness Ra of 1 nm or less by polishing. The required thickness and strength can be ensured by pasting the single crystal wafer 5 and the support substrate 3 together.

(2) Manufacturing Process of Bonded Substrate Support Substrate 3 Next, a manufacturing process of the bonded substrate support substrate 3 will be described with reference to FIG. FIG. 3 is a cross-sectional view showing a manufacturing process of a support substrate according to an embodiment of the present invention, where (a) is a cross-sectional view of a silicon carbide sintered body before processing, and (b) is an impregnation of molten Si into voids. FIG. 3C is a cross-sectional view of a silicon carbide sintered body, and FIG.

(2-1) Structure of Silicon Carbide Sintered Body As shown in FIG. 3A, the silicon carbide sintered body 21 has a number of voids (pores) such as recesses 23 on the surface 7 and cavities 25 inside. The surface 7 becomes the bonding surface 6 shown in FIG. 2 through a polishing process described later. Since the surface 7 itself is not polished, fine irregularities are formed. The cavity 25 is connected to the surface 7 at another part (not shown). Thus, the silicon carbide sintered body 21 is formed into a porous body having a plurality of voids. The silicon carbide sintered body 21 is manufactured using a hot press or the like.

(2-2) Manufacturing Process As shown in FIG. 3 (b), first, a silicon carbide sintered body 21 is produced with high-purity SiC powder, and the silicon carbide sintered body 21 is immersed in molten silicon. Then, molten silicon is impregnated in the gaps such as the recesses 23 and the cavities 25 by utilizing capillary action. As described above, since the cavity 25 is connected to the surface 7, the cavity 25 is also impregnated with molten silicon from the surface 7. As a result, all the voids formed in the silicon carbide sintered body 21 are filled with molten silicon, and there are no gaps. After that, when the molten silicon is cooled and solidified, the solidified silicon 27 is filled in the gap, and a part of the silicon 27 protrudes outward from the surface 7 to form a protruding portion 29. As a result, the support substrate 3 according to the present embodiment has a SiC-Si composite structure in which the base material is silicon carbide in which the voids are completely filled with the silicon 27.

  Next, as shown in FIG. 3C, when the surface 7 of the silicon carbide sintered body 21 filled with the solidified silicon 27 is polished, it becomes a smooth mirror surface, and the smooth surfaces 31 and 33 form the single crystal wafer 5. The joining surface 6 becomes. Note that the smooth surface 31 is a surface after polishing the protruding portion 29 of the silicon 27, and the smooth surface 33 is a surface after polishing the surface 7 of the silicon carbide sintered body 21 itself. As this polishing method, mechanical polishing, chemical polishing, chemical mechanical polishing (CMP), or the like can be widely used. Mechanical polishing is a method of mechanically finishing the surface of a workpiece into a mirror surface by an operation of rubbing a polishing pad carrying abrasive grains such as a GC grindstone or diamond with the workpiece. Chemical polishing is a method in which a chemical that removes surface irregularities of a workpiece is used as a polishing liquid, and the surface of the workpiece is chemically finished into a mirror surface by an operation of rubbing the workpiece and a tool surface. Chemical mechanical polishing is a polishing method in which efficiency is improved by providing a synergistic effect between the mechanical polishing and the chemical polishing. Thus, the support substrate 3 provided with the silicon carbide sintered body 21 having the recesses 23 and the cavities 25 as a plurality of voids and the silicon 27 filled in the voids is obtained.

  When the single crystal wafer 5 is bonded to the bonding surface 6 by applying an adhesive or the like, the bonded substrate 1 according to the present embodiment is formed.

The surface polishing by the difference in density will be described. In the case of the silicon carbide sintered body 21 having a density of 1.9 g / cm ³ , the Si ratio after impregnation is high, and the surface roughness Ra after polishing is only 5 nm due to the influence of Si that is easily polished. When the density is 2.3 to 3.0 g / cm ³ , the Si ratio after impregnation is low, and the surface roughness Ra after polishing is 1 nm or less. When the density is higher than 3.0 g / cm ³ , Si impregnation is impossible. Therefore, the density of the silicon carbide sintered body 21 according to the present embodiment is preferably 2.3 to 3.0 g / cm ³ .

(3) Effect Next, the effect by this embodiment is demonstrated.

  The bonded substrate support substrate 3 according to the embodiment of the present invention is a support substrate 3 bonded to a single crystal wafer 5 made of a single crystal, and the support substrate 3 includes a plurality of voids 23 and cavities 25. The bonding surface 6 of the support substrate 3 that is provided with the silicon carbide sintered body 21 and the silicon 27 filled in the gap and is bonded to the single crystal wafer 5 is smooth. For this reason, compared with the support substrate which consists of a normal silicon carbide sintered compact, the joining strength of a silicon carbide sintered compact and a single crystal wafer can be made high.

  Since the arithmetic average roughness at the bonding surface 6 of the embodiment of the present invention is 1 nm or less, a gap is generated between the single crystal wafer 5 and the substrate support substrate 3 when bonded to the single crystal wafer 5. It becomes difficult and joint strength improves.

The density of the silicon carbide sintered body 21 is 2.3 to 3.0 g / cm ³ . When the density is less than 2.3 g / cm ³ , it has been difficult to improve the smoothness by conventional mechanical polishing and chemical polishing. That is, in mechanical polishing, Si is more easily polished because there is a large hardness difference between low-density Si and SiC. Therefore, SiC can be polished into a concavo-convex surface having a mountain shape and Si having a valley shape, and Ra can only be about 5 nm. Also in the case of chemical polishing, there is a difference in the removal rate due to chemicals, and SiC is polished to an uneven surface having a mountain shape and Si having a valley shape, and Ra can only be about 5 nm. On the other hand, when the density is larger than 3.0 g / cm ³ , the number of voids decreases, and thus impregnation becomes difficult. Therefore, 2.3 to 3.0 g / cm ³ is most preferable from the viewpoint of the size of the gap and the ease of impregnation with Si.

  The method for manufacturing the bonded substrate support substrate 3 according to the embodiment of the present invention is a method for manufacturing the support substrate 3 bonded to the single crystal wafer 5 made of a single crystal, and in the porous silicon carbide sintered body 21. A step of impregnating molten silicon into the recesses 23 and cavities 25 which are a plurality of voids, a step of cooling and solidifying the molten silicon, and polishing the surface 7 of the silicon carbide sintered body 21 to form the single crystal wafer 5. Forming the joint surface 6.

  Thus, since the voids of the silicon carbide sintered body 21 are filled with the silicon 27 so that there are no gaps, the surface 7 is polished, so that the bonding surface 6 with the single crystal wafer 5 becomes uneven or hollow. It can be formed on a smooth surface having no voids.

  That is, the silicon carbide sintered body 21 is formed with fine irregularities on the surface 7 and has voids 25 formed by pores inside. As described above, the silicon carbide sintered body 21 has a large number of voids including irregularities and cavities 25. Therefore, even if the surface 7 of the silicon carbide sintered body 21 is polished as it is, the voids appear in the surface layer, so the surface 7 is not smoothed no matter how much it is polished. Therefore, as in this embodiment, when the surface 7 is polished after filling the voids of the silicon carbide sintered body 21 with the silicon 27 so that there are no voids, the smooth surfaces 31 and 33 which are the smooth bonding surfaces 6 are obtained. Is formed. For this reason, when the bonding surface 6 of the support substrate 3 and the single crystal wafer 5 are bonded to each other, a gap is hardly generated between them, and the bonding strength between the support substrate 3 and the single crystal wafer 5 can be improved. Since Si is a material that is easier to polish than SiC, polishing work is facilitated.

In the method for manufacturing the support substrate 3 according to the embodiment of the present invention, the density of the silicon carbide sintered body 21 is 2.3 to 3.0 g / cm ³ and the step of forming the bonding surface 6 includes: The surface 7 of the silicon carbide sintered body 21 is polished by chemical mechanical polishing. Since chemical mechanical polishing is a polishing method that combines the advantages of mechanical polishing and chemical polishing, the effect of smoothing the surface 7 is higher than that of mechanical polishing and chemical polishing.

Moreover, since the density of the said silicon carbide sintered compact 21 is 2.3-3.0 g / cm < ³ >, arithmetic mean roughness Ra in the joint surface 6 can be 1 nm or less. That is, at a low density of less than 2.3, since Si and SiC have a large hardness difference, Si is more easily polished, and Ra is larger than 1 nm. On the other hand, when the density is larger than 3.0 g / cm ³ , the number of voids decreases, so that it becomes difficult to impregnate with molten silicon. Accordingly, the case of 2.3 to 3.0 g / cm ³ is most preferable from the viewpoint of the size of the gap and the ease of impregnation with Si, and Ra on the bonding surface 6 can be 1 nm or less. When the bonded substrate 1 is formed by a method that does not use an adhesive, the bonded surfaces must be close to 1 nm or less in order to utilize the attractive force between atoms. If it is the support substrate 3 which concerns on this embodiment, the support substrate 3 and the single crystal wafer 5 can be joined suitably also by the method which does not use an adhesive agent. That is, even if it is a method which does not use an adhesive agent, the bonded substrate board 1 with sufficient joint strength can be formed.

  It should not be understood that the description and the drawings, which form part of the disclosure of the above-described embodiments, limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. It goes without saying that the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 1 Bonding substrate 3 Bonding substrate support substrate 5 Single crystal wafer 6 Bonding surface 7 Surface 23 Recess (gap)
25 Cavity
27 Silicon 31, 33 Smooth surface

Claims (2)

A method of manufacturing a support substrate to be bonded to a single crystal wafer made of a single crystal ,
Impregnating molten silicon into a plurality of continuous voids in a porous silicon carbide sintered body having a density of 2.3 to 3.0 g / cm ³ ;
Cooling and solidifying the molten silicon;
Polishing the surface of the silicon carbide sintered body by chemical mechanical polishing to an arithmetic average roughness of 1 nm or less to form a bonding surface with the single crystal wafer;
The manufacturing method of the support substrate containing this . A silicon carbide sintered body having a plurality of communicating voids and a silicon filled in the voids, and a support substrate having a smooth bonding surface bonded to the single crystal wafer,
A bonded substrate manufactured by the method for manufacturing a support substrate according to claim 1, wherein the silicon carbide sintered body has a density of 2.3 to 3.0 g / cm ³ and is bonded to the single crystal wafer. A support substrate having an arithmetic average roughness of 1 nm or less .

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