JP2010224335A - Dissimilar material assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dissimilar material assembly, for eliminating the generation of a crack between the different materials, for example, between a semiconductor substrate and a material such as a magneto-optical material when manufacturing an optical isolator. <P>SOLUTION: This dissimilar material assembly is formed by joining the substrate comprising a semiconductor material, and the different kind of material different from the material of the substrate, and is arranged with a plurality of divided island-like joining part with a separation part, on a surface of the substrate or the different kind of material. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a dissimilar material joined body formed by joining dissimilar materials, in particular, a semiconductor substrate and a magneto-optical material.

  A technique for directly joining different kinds of materials without using an adhesive or the like (sometimes referred to as direct bonding or simply bonding) is used in the field of manufacturing components and devices formed using a composite material. Among these, in recent years, the surface activated bonding method is known as a technique for directly bonding different materials when manufacturing parts and devices.

As a part (device) manufactured using the above method, for example, Patent Document 1 (International Patent Publication No. 2007/083419) discloses an optical isolator as shown in FIG. The optical isolator shown in FIG. 1 includes a magneto-optical material 102 of CeY ₂ Fe ₅ O ₁₂ (Ce: YIG) on a waveguide layer 101 made of semiconductor GaInAsP grown on a semiconductor InP substrate 100. As shown in FIG. 2, the cross-sectional structure is a simple laminated structure.

  However, such a device in which a semiconductor laser and an optical isolator are integrated integrally activates a magneto-optical material necessary for the optical isolator function on an optical waveguide formed of a III-V compound semiconductor in the manufacturing process. When joining by joining (heating the material at a high sound of about 120 to 400 ° C. and joining) without distortion at the time of joining at high temperature, if the joined part is returned to room temperature, joining is performed due to the difference in thermal expansion coefficient of the material. There is a problem that stress is generated in the vicinity of the interface, and cracks are generated from the material surface. FIG. 3 shows an example of the occurrence of a crack, and a portion that appears to spread in a strip shape in the major axis direction is a crack. Since such a crack is formed so as to cross the optical waveguide, the optical waveguide is divided and the light transmission loss is remarkably increased. Therefore, preventing the occurrence of cracks is indispensable for the production of components and devices.

  On the other hand, as a method for mitigating or suppressing stress that causes cracks in the joint surface during device manufacturing by surface activation bonding as described above, a method of arranging grooves in a material is disclosed in, for example, JP-A-2007- No. 214369 (Patent Document 2).

  However, although the method disclosed in Patent Document 2 discloses that the effect of stress relaxation or suppression is exhibited by disposing grooves in the material, the bonding itself has no non-joined portion with the groove as a boundary. It is bent, and the bent portion is involved in joining. For example, when a waveguide is disposed on a non-joint surface when manufacturing a device such as an optical isolator, according to a technique such as Patent Document 2, the substrate is deformed by joining, and the waveguide is divided. Therefore, there is a high possibility that the function as the waveguide will not be fulfilled. Therefore, the joining method using deformation (warping or the like) of the non-joining part as in Patent Document 2 is an integrated circuit or semiconductor component such as light or electricity, It is not suitable for manufacturing devices.

International Patent Publication No. 2007/083419 JP 2007-214369 A

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a semiconductor substrate and a material such as a magneto-optical material when manufacturing different materials, for example, optical isolators. An object of the present invention is to provide a joined body of different materials that eliminates the occurrence of cracks in the meantime.

  The above-mentioned object of the present invention is a dissimilar material joined body formed by joining a substrate made of a semiconductor material and a dissimilar material different from the substrate, and a spacing portion is formed on the surface of the substrate or the dissimilar material. This is achieved effectively by having a plurality of divided island-shaped joint portions.

  Further, the object of the present invention is that the dissimilar material is a magneto-optical material, or that the cross-sectional shape of the divided island-shaped joint is rectangular or circular, or the width of the divided island-shaped joint is large. When it is 1 to 200 μm, or when the width of the separated portion is 5 to 60% of the width of the divided island-shaped joint, or the height of the divided island-shaped joint is 10 to 200 nm. Some are achieved more effectively.

  Furthermore, it can also be effectively achieved by an optical isolator composed of the above-mentioned dissimilar material joined body.

  In the dissimilar material joined body of the present invention, the size of the stress generated by the difference in thermal expansion can be reduced by reducing the joint area (joint dimension) per place. Also, in order to obtain a sufficient bonding force, it is necessary to secure the entire bonding area to some extent, so instead of bonding a uniform wide area, the bonding surface is divided into islands with a rectangular or circular cross section, By shortening the dimension per joint, the strain generated by the difference in thermal expansion coefficient can be reduced.

  Further, by dividing the joint surface into islands, the generation of thermal stress can be reduced in the state where the temperature is returned to room temperature from the time of high-temperature bonding, and the generation of cracks in the bonding of different materials can be reduced or suppressed.

It is an external view which shows an example of an optical isolator. FIG. 2 is a cross-sectional view illustrating the bonding of the substrate, the waveguide layer, and the dissimilar material (Ce: YIG) in FIG. 1. FIG. 2 is an electron micrograph showing an example in which a crack is generated on a bonding surface between a substrate and a different material (magneto-optical material) in FIG. 1. It is sectional drawing which shows an example of the conjugate | zygote cross section which consists of a board | substrate and a dissimilar material in this invention. It is a figure which shows an example of the surface of the board | substrate in this invention. It is sectional drawing which shows the joining simulation (conventional example) of a surface uniform board | substrate and a dissimilar material. It is sectional drawing which shows the joining simulation (this invention) of a division | segmentation island-like junction part installation board | substrate and a dissimilar material. It is a figure for demonstrating the stress distribution of the joining simulation of FIG. It is a figure for demonstrating the stress distribution of the joining simulation of FIG. It is sectional drawing which shows the example of joining of a surface uniform substrate and a dissimilar (magneto-optic) material. It is a top view of the board | substrate which shows the example of the division | segmentation island-like junction part of this invention. It is a figure which shows the joint surface of the board | substrate in the sample A. FIG. It is a figure which shows the joint surface of the board | substrate in the sample B. FIG. It is sectional drawing of the semiconductor structure which shows the application example of the conjugate | zygote of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 4 is a cross-sectional view showing an example of a laminated structure of a joined body made of the substrate 1 and the different material 2 in the present invention. The bonding of the substrate 1 and the different material 2 is divided on the upper surface of the substrate 1. This is performed by the divided island-shaped joint portion 3 having a height H provided in an island shape. Here, the substrate 1 and the dissimilar material 2 constituting the laminated structure, and the method of joining the substrate 1 and the dissimilar material 2 will be sequentially described.

  The material of the substrate 1 is not particularly limited as long as it is a flat substrate without warping or bending, but among them, a semiconductor material (III-V group, IV group, etc.) is preferable. Further, when considering the strength, thermal conductivity, etc. of the substrate 1 itself, III-V (group 13-15) compound semiconductors such as indium phosphide (InP) and gallium arsenide (GaAs) are preferable. Here, when manufacturing an optical isolator or the like is considered, a semiconductor material that can be a constituent material such as a waveguide needs to be crystal-grown on the substrate 1 in advance. Note that the crystal growth method at this point may be a conventional method such as metal organic chemical vapor deposition or molecular beam epitaxy. The thickness of the substrate 1 may be in the unit of μm, but is preferably about 100 μm to 1 mm.

Next, as with the substrate 1, the dissimilar material 2 is not particularly limited as long as it is an inorganic compound according to the application (magneto-optical characteristics, semiconductor characteristics, etc.). A material capable of crystal growth of the material, particularly a garnet crystal is preferable. Examples include gadolinium gallium garnet (Gd ₃ Ga ₅ O ₁₂ : GGG), substituted gadolinium gallium garnet (SGGG), and the like. In consideration of actual application, for example, production of an optical isolator, the cerium-substituted yttrium iron garnet (Ce: YIG) and bismuth-substituted yttrium iron garnet (Bi: YIG) are formed on the upper surface of the dissimilar material 2 in the same manner as the substrate 1. Such a magneto-optical material is used after crystal growth. The crystal growth method at this time may be a conventional method such as sputtering epitaxy, liquid phase growth, FZ, Czochralski, or solvent transfer floating zone melting. The thickness of the different material 2 is also preferably about 100 μm to 1 mm.

  Next, an example of the surface structure of the substrate 1 is shown in FIG. As described above, after the constituent material is crystal-grown on the substrate 1, the divided island-shaped joint portions 3 having a rectangular cross section are arranged on the substrate 1 at equal intervals, and the width of the joint portion 3 is set between the joint portions 3. It is provided so as to have a width of about 5 to 60% with respect to D. That is, when the width of the divided island-shaped joint portion 3 is D in the xy-axis direction, the separation distance Dx in the x-axis direction that forms the separation portion 4 of the adjacent divided island-shaped joint portion is D × (0.05-0.0.0). 6), the separation distance Dy in the y-axis direction is D × (0.05 to 0.6), and the separation distances Dx and Dy may be different.

  The cross-sectional shape of the divided island-shaped joint portion 3 is not particularly limited as long as the separation portion 4 can be provided on the substrate 1 (however, the width D of the divided island-shaped joint portion 3 and the separation distances Dx and Dy are in the above described range). However, for example, as shown in FIG. 5, it is desirable that the corner is a rectangle or a circle having an arc shape. When the cross section of the divided island-shaped divided portion 3 is rectangular, the stress relaxation effect can be increased by making the corners arc-shaped as compared to the rectangle as it is, but the corners are not arc-shaped. Also has a mitigating effect. Further, the width D of the divided island-shaped joint portion 3 is preferably 1 to 200 μm. In this case, if the width D is 1 μm or less or 200 μm or more, the stress relaxation due to the thermal expansion of the substrate 1 is not sufficient.

  Since the divided island joints 3 are arranged in an orthogonal lattice shape, the stress applied to the joint surface is evenly dispersed. For example, when the optical isolator is manufactured, a waveguide may be provided in the separation portion 4. Moreover, as for the height (depth of the separation part 4) H of the division | segmentation island-like junction part 3, 10-200 nm is desirable. When the thickness is 10 nm or less, the relaxation of stress due to thermal expansion of the substrate 1 is not sufficient, and when the thickness is 200 nm or more, cracks or the like may occur in the substrate 1 or the stress may be further applied. Here, providing the widths Dx and Dy of the above-described separated portion 4 so as to be 5 to 60% of the width D of the divided island-shaped joint portion 3 is, for example, the width D of the divided island-shaped joint portion 3. Is 100 μm, the widths Dx and Dy of the separation portion 4 are set to 5 to 60 μm. Incidentally, the widths Dx and Dy of the separation part 4 do not have to be the same width as long as the condition of 5 to 60% with respect to the width D of the divided island-like joint part 3 is respected. I do not care. If the spacing portion 4 has a width of 5% or less, stress relaxation due to thermal expansion of the substrate 1 becomes insufficient, and if it has a width of 60% or more, the bonding surface of the substrate 1 may be deformed. is there.

  A conventional manufacturing method such as etching, molding, mechanical embossing, or the like can be used as a method of providing the divided island-shaped joints 3 on the substrate 1. In addition, the divided island-shaped joint 3 may be provided on the different material 2 side in consideration of the hardness, thermal conductivity, etc. of the substrate 1 or the different material 2.

  Next, joining of the substrate 1 and the dissimilar material 2 will be described. The bonding temperature is preferably 100 to 500 ° C. If the bonding temperature is 100 ° C. or lower, the surface may not be activated and bonding may be insufficient. Further, when the temperature is 500 ° C. or higher, the substrate 1 or the different material 2 is deformed by melting, composition change, surface state change or the like before the bonding, or even if the substrate 1 or the different material 2 is bonded. When this is cooled to room temperature, distortion may occur, or cracks may occur.

  Although the joined body of the present invention has been described above, the present invention is not limited to these, and various modifications can be made.

  Next, the details of the embodiment of the present invention described above will be described based on specific examples (joining in the manufacturing process of the optical isolator).

[Example 1] Thermal stress simulation around the joining region First, when dissimilar materials were joined without distortion during high-temperature joining, a simulation using finite element method analysis was performed on the stress distribution generated at room temperature.

6 and 7 are cross-sectional views showing how the substrate 5 and the dissimilar material 6 are joined in the simulation, FIG. 6 shows a joining surface of the conventional surface uniform substrate 6A, and FIG. The bonding surface of the substrate 6 provided with the divided island-shaped bonding portions 7 is shown. In each case, as a material condition, a garnet crystal Gd ₃ Ga ₅ O ₁₂ (hereinafter abbreviated as GGG) was used as the dissimilar material 5. . GGG is a material that becomes a crystal growth substrate of a magneto-optical material for optical isolators (Ce-substituted Y ₃ Fe ₅ O ₁₂ (Ce: YIG)), and has substantially the same mechanical properties as Ce: YIG. The thickness of the dissimilar material 5 used in Example 1 was 500 μm (y-axis direction in FIG. 6).

  Further, III-V compound semiconductor crystal InP was used as the substrates 6 and 6A. This InP is a material used as a crystal growth substrate for the semiconductor waveguide constituent material GaInAsP, and has substantially the same mechanical properties as GaInAsP. The substrate surface of the substrate 6A is uniform, and the substrate 6 has the divided island-shaped joint portions 7 having a width of 200 μm and a height of 200 nm on the substrate surface, and the separation distance between the divided island-shaped joint portions 7 is 100 μm. ing. Here, the thickness of the substrates 6 and 6A used in Example 1 is 350 μm, the length of the different material 5 (x-axis direction in FIG. 6) is 10 mm, and the length of the substrates 6 and 6A (in FIG. 6). x-axis direction) is 15 mm. Table 1 shows material constants of the respective materials.

  Next, the case where the dissimilar material 5 and the substrate 6A are bonded at a temperature of 400 ° C. (FIG. 6) and the case where the dissimilar material 5 and the substrate 6 are bonded at the same temperature of 400 ° C. (FIG. 7) are brought to room temperature. The stress distribution generated was calculated (see FIGS. 8 and 9). In the stress distribution calculation, the structure is a two-dimensional structure. That is, in FIGS. 6 and 7, the structure is uniform in the direction perpendicular to the plane.

  In the case of FIG. 6, 8.3 GPa is generated as the largest stress in the InP of the substrate 6A at the portion (the portion indicated by the arrow in FIG. 8A) facing the end of the dissimilar material 5 (the portion indicated by the arrow in FIG. 8A). (See the underlined portion in FIG. 8B). In the case of FIG. 7, the maximum stress was reduced to 3.2 GPa (see the underlined portion in FIG. 9B). The location where the maximum stress is generated is almost the same location as that of the uniform joint surface (the portion indicated by the arrow in FIG. 9A). That is, the stress reduction effect by the joint surface division of the present invention could be confirmed by the simulation as described above.

[Example 2] Joining Experiment Considering joining in the manufacturing process of an optical isolator, which is an actual application, a case where a dissimilar material (magneto-optic material) 8 is joined using a substrate 9 having a uniform surface (see FIG. 10). The comparison was made with the case where the dissimilar material 8 was joined to the substrates 10 and 10A each having the divided island joints 11 and 11A arranged on the surface (see FIGS. 11A and 11B).

FIG. 10 is a cross-sectional view of a side surface when a magneto-optical material 9 and a substrate 9 having a uniform upper surface are bonded as a comparative example (hereinafter referred to as “sample A”) in the second embodiment. As the magneto-optical material 8, a material obtained by growing Ce: YIG having a thickness of 0.5 μm on a GGG (Gd ₃ Ga ₅ O ₁₂ ) substrate by sputtering epitaxy is used. As the substrate 9, a substrate in which a GaInAsP crystal having a thickness of 0.36 μm is grown on InP by sputtering epitaxy is used. Both the magneto-optical material 8 and the substrate 9 were bonded by a surface activated bonding method at a bonding temperature of 150 ° C.

  FIG. 11 is a plan view when the divided island-shaped joint portion is arranged on the surface of the substrate as Example 2 of the present invention. FIG. FIG. 5 is a plan view when the divided island-shaped joint portions 11 having a rectangular cross section (100 μm × 100 μm) are arranged in three stages and the waveguide 12 is arranged in the center of the boundary of each stage. The cross section of the divided island-shaped joint portion 11 is a 100 μm × 100 μm square corner portion formed into an arc shape, and the divided island-shaped joint portion 11 having a height of 10 nm is arranged in three steps and spaced apart every 5 μm. In addition, a separation portion of 30 μm is provided between each of the divided island-shaped joint portions 11 and the waveguide 12. The substrate 10 was manufactured under the same conditions as the substrate 9 shown in FIG. 10. Hereinafter, a sample subjected to a bonding experiment using the substrate 11 shown in FIG. To do.

  FIG. 11B shows a cross section when the divided island-shaped joint portions 11A having a circular cross section (diameter of 200 μm) are arranged in three stages on the surface of the substrate 10A, and the waveguide 12A is arranged in the center of the boundary of each stage. FIG. The divided island-shaped joint portion 11A is a circular shape having a diameter of 200 μm, and the divided island-shaped joint portions 11A having a height of 10 nm are arranged in three steps and spaced apart every 5 μm. A space of 30 μm is provided between 11A and the waveguide 12A. The substrate 10A was manufactured under the same conditions as the substrate 9 shown in FIG. 10. Hereinafter, a sample subjected to a bonding experiment using the substrate 10A shown in FIG. 11B is referred to as “sample C”. To do.

  As shown in FIG. 11 (a), the cross-section of the divided island-shaped joint portion 11 is not a perfect rectangle, but a pattern in which corners are arcuate, and a circular island-like pattern as shown in FIG. 11 (b). The reason for this is to avoid stress concentration by eliminating the corners.

  In addition, as matters common to the samples A, B and C, the surface widths of the substrates 9, 10 and 10A are 4 mm × 4 mm, the magneto-optical material 8 to be bonded is the same, and the bonding temperature is 150 ° C. As mentioned above, it is bonded by a surface activated bonding method.

  In the second embodiment, the sputter epitaxy method is used as the Ce: YIG crystal growth method, and the metal organic vapor phase growth method is used as the GaInAsP crystal growth method. However, the present invention is limited to the sputter epitaxy method and the metal organic vapor phase growth method. There is no need.

  As a result, in Sample A, as seen in the micrograph shown in FIG. 12, the occurrence of cracks on the surface of GaInAsP and the substrate 9 was observed at a plurality of locations. On the other hand, in sample B, no crack was observed (FIGS. 13A and 13B). Here, FIG. 13A is a photomicrograph of the vicinity of the center of the bonding material 8, and FIGS. Note that Sample C was the same as Sample B although no micrograph was taken.

  Therefore, even when the temperature at the time of bonding is relatively low, such as 150 ° C., by reducing the stress at the time of returning from the temperature at the time of bonding to room temperature by forming one of the bonding surfaces into an island shape. It is concluded that there is an effect.

[Application Example] Manufacturing of Semiconductor Laser Integrated Circuit on Silicon Optical Circuit As an example of application of the joining experiment of Example 2, the manufacturing of a semiconductor laser integrated circuit on a silicon optical circuit will be schematically described with reference to the drawings.

FIG. 14 is a schematic diagram of a semiconductor laser integrated circuit on a silicon optical circuit according to the third embodiment. The silicon optical circuit 13 includes a silicon substrate 14, a box layer 15 made of silicon dioxide (SiO ₂ ), and a silicon waveguide 16. The silicon optical circuit 13 is manufactured by a conventional method.

  Next, the substrate 17 that plays the role of semiconductor laser integration is a substrate obtained by crystal-growing GaInAsP19 on the InP substrate 18.

  Although not shown in the present specification, in this application example, an island-shaped divided junction surface as shown in FIGS. 5 and 11 can be arranged on the surface of the silicon optical circuit 13 (the junction surface with the substrate 17). In this application example, the island-shaped divided joint portion or the separated portion can be manufactured by a conventional method such as etching, and the width and height of the island-shaped divided joined portion, the width of the separated portion, the bonding temperature, etc. are changed as appropriate. Is possible.

  In the above description, the cross-sectional shape of the divided island-shaped joint is described as a rectangle and a circle, but the shape is arbitrary, and a structure in which at least two long joints are provided may be used.

1, 6, 6A, 9, 10, 10A, 17 Substrate 2, 5, 8 Dissimilar material 3, 7, 11, 11A Divided island joint 4 Spacing part 12, 12A Waveguide 13 Silicon optical circuit 14 Silicon substrate 15 Box Layer 16 Silicon waveguide 18, 100 InP substrate 19 GaInAsP
101 Waveguide layer 102 Magneto-optic material

Claims (7)

  A dissimilar material joined body obtained by joining a substrate made of a semiconductor material and a dissimilar material different in material from the substrate, and having a plurality of divided islands on the surface of the substrate or the dissimilar material. Dissimilar material joined body, characterized in that a joint is disposed.   The dissimilar material joined body according to claim 1, wherein the dissimilar material is a magneto-optical material.   The heterogeneous material joined body according to claim 1 or 2, wherein a cross-sectional shape of the divided island joint is a rectangle or a circle.   The heterogeneous material joined body according to any one of claims 1 to 3, wherein the divided island-shaped joined portion has a width of 1 to 200 µm.   5. The dissimilar material joined body according to claim 1, wherein a width of the spaced-apart portion is 5 to 60% with respect to a width of the divided island-shaped joint portion.   The heterogeneous material joined body according to any one of claims 1 to 5, wherein a height of the divided island-shaped joined portion is 10 to 200 nm. The optical isolator which consists of a dissimilar-material joined body of any one of Claims 1 thru | or 6.