JP5185895B2 - Photoelectric conversion submount substrate and manufacturing method thereof - Google Patents

Description

  The present invention relates to a photoelectric conversion submount substrate that mutually converts light and electric signals, and a method for manufacturing the same.

  In recent years, the need for an information processing circuit having a very high-speed information transmission path is increasing with the rapid widening of communication infrastructure and the dramatic increase in information processing capability of computers and the like. Under such circumstances, transmission by an optical signal is considered as one means for breaking the transmission speed limit of an electric signal, and various studies have been made on mounting an optical circuit in an electric circuit. A photoelectric conversion submount substrate is known as a unit that converts an optical signal into an electrical signal or vice versa.

  FIGS. 13A and 13B show an example of a conventional photoelectric conversion submount substrate. FIG. 13A is a plan view, and FIG. 13B is a horizontal side view of FIG. The photoelectric conversion submount substrate is formed by covering and sealing the substrate 1, the core layer 21 formed on the concave surface 20 of the substrate surface, and the core layer 21, and the upper end surface protruding from the substrate surface. The optical waveguide 2 composed of the clad layer 22, the optical element 4 optically coupled to the optical waveguide 2, the underfill 5 filled between the optical element 4 and the optical waveguide 2, and the end thereof are bonded to the substrate surface. And an external waveguide film 3 having an external waveguide 23 and a film 24.

  12A and 12B are enlarged views of a main part of the photoelectric conversion submount substrate. FIG. 12A is a cross-sectional view of (b) and FIG. 12 (b) is a perspective view. In FIG. 12B, the underfill 5 is omitted. In FIGS. 12 and 13, 6 is a circuit layer formed of a metal pattern, and 7 is a light reflecting layer formed as a 45 ° mirror. As shown in FIG. 12, the upper end surface of the cladding layer 22 is higher than the substrate surface, and a step X is formed between the cladding layer 22 and the substrate 1. The step X has a height of about 1 to 15 μm.

  In such a photoelectric conversion submount substrate, light and electricity can be efficiently converted, and the optical element 4 is fixed to the substrate 1 by the underfill 5 so that it is strong and has good photoelectric conversion performance. it can.

  However, in the photoelectric conversion submount substrate as described above, the underfill 5 filled between the optical element 4 and the substrate 1 crosses the step X of the cladding layer 22 by the capillary phenomenon, and the external waveguide film 3 When the liquid flows out to reach the film adhesion surface, there is a problem that a connection strength failure of the external waveguide film 3 occurs.

  In FIG. 12B, the underfill 5 flows out in the direction indicated by the thick arrow shown in the step X of the cladding layer 22. Further, in FIG. 13A, the flow of the underfill 5 is indicated by a hatched portion (UF outflow) indicated by an arrow.

  In manufacturing the photoelectric conversion submount substrate as described above, after forming each layer such as the optical waveguide 2 on the wafer and mounting the optical element 4, the underfill 5 is filled, and then the wafer is separated while protecting the element. The substrate 1 is taken out and separated, and the external waveguide film 3 is bonded to the separated substrate 1. Therefore, the underfill 5 that has reached the surface to which the film is to be bonded due to the outflow reduces the adhesiveness of the adhesive, and thus prevents the external waveguide film 3 from being bonded to the substrate 1. In addition, filling the underfill 5 first at the wafer level, not after film bonding, has better handling properties, and also serves to protect the element when separated into pieces (when cutting by dicing or the like). Because it fulfills.

  As described above, when the underfill 5 flows out and reaches the adhesion surface of the external waveguide film 3, a connection failure occurs. This poor connection strength causes the external waveguide film 3 to peel off, resulting in poor photoconductivity. In addition, there is a problem in that the reliability of the photoelectric conversion submount substrate is deteriorated because it leads to component failure.

  Patent Document 1 discloses a structure for preventing the underfill 5 from flowing out in the photoelectric element. In this document, a recess is provided on the mounting surface of the optical semiconductor element, and the underfill is prevented from flowing out by filling the recess with the underfill. However, in the structure of this document, in addition to the formation of the recess in the part where the optical semiconductor element is mounted, the optical semiconductor element must be embedded in the recess so as to be mounted, and the manufacturing is complicated. It was to become. In addition, the underfill overflowing from the concave portion cannot be prevented from flowing out due to capillary action, and in the structure such as the photoelectric conversion submount substrate of FIGS. It wasn't possible.

Japanese Patent Laid-Open No. 2007-3906

  The present invention has been made in view of the above points. The underfill 5 filled between the optical element 4 and the substrate 1 connects the step X of the clad layer 22 by the capillary phenomenon, and the external waveguide film 3. Even if it flows out toward the substrate, the underfill 5 is prevented from reaching the film adhesion surface, and the external waveguide film 3 is peeled off by suppressing the poor connection strength of the external waveguide film 3 to the substrate 1. It is an object of the present invention to provide a highly reliable photoelectric conversion submount substrate and a method for manufacturing the same.

  According to the first aspect of the present invention, the substrate 1, the core layer 21 formed on the concave surface 20 of the substrate surface, and the core layer 21 are covered and sealed, and the upper end surface protrudes from the substrate surface. The optical waveguide 2 composed of the clad layer 22, the optical element 4 optically coupled to the optical waveguide 2, the underfill 5 filled between the optical element 4 and the optical waveguide 2, and an end bonded to the substrate surface The underfill 5 that flows out from between the optical element 4 and the optical waveguide 2 is provided on the substrate surface between the optical element 4 and the end of the external waveguide film 3. The photoelectric conversion submount substrate is characterized in that an outflow prevention portion 10 is formed to prevent reaching the adhesion surface with the substrate surface.

  According to a second aspect of the present invention, in the photoelectric conversion submount substrate having the above-described configuration, the outflow prevention portion 10 is made of the same material as the core layer 21 and is formed in a wall shape on the substrate surface. It is a conversion submount substrate.

  According to a third aspect of the present invention, there is provided a photoelectric conversion submount substrate having the above-described structure, wherein the outflow prevention portion 10 is made of the same material as that of the cladding layer 22 and is formed in a wall shape on the substrate surface. It is a conversion submount substrate.

  According to a fourth aspect of the present invention, in the photoelectric conversion submount substrate having the above-described configuration, the outflow prevention portion 10 is a groove 12 formed on the substrate surface.

  The invention according to claim 5 is the photoelectric conversion submount substrate having the above structure, wherein the recess 12 is provided in the groove 12.

  According to a sixth aspect of the present invention, in the photoelectric conversion submount substrate having the above configuration, the depth of the groove 12 gradually increases as the distance from the optical waveguide 2 increases.

  According to a seventh aspect of the present invention, in the photoelectric conversion submount substrate having the above-described configuration, the substrate 1 has an insulating film 14 formed on the surface thereof, and the outflow prevention portion 10 is formed without the insulating film 14 provided on the substrate surface. This is a photoelectric conversion submount substrate characterized in that the groove 12 is formed.

  The invention according to claim 8 is the photoelectric conversion submount substrate, wherein the outflow prevention portion 10 is a metal thin film 15 formed on a surface of the substrate.

  The invention according to claim 9 is the photoelectric conversion submount substrate having the above-described configuration, wherein the circuit layer 6 is provided on the substrate surface, and the metal thin film 15 is made of the same material as the circuit layer 6. Mount substrate.

  The invention according to claim 10 is the photoelectric conversion submount substrate having the above-described configuration, wherein the outflow prevention portion 10 is formed so as to surround the periphery of the optical element 4.

  The invention according to claim 11 is the photoelectric conversion submount substrate, wherein the outflow prevention portion 10 is formed from the optical waveguide 2 to the end portion of the substrate 1 in the photoelectric conversion submount substrate having the above configuration. is there.

  The invention of claim 12 includes the following steps (a), (c), (d), (f), (g) and (h): (a) (b) (c) (d) (f) (g) And (h), or (a), (c), (d), (e), (f), (g), and a method of manufacturing the photoelectric conversion submount substrate having the above-described structure. (A), (b), (c), (d), and (e), on the substrate surface between the optical element 4 and the end of the external waveguide film 3, A method for manufacturing a photoelectric conversion submount substrate, comprising forming an outflow prevention portion 10 for preventing underfill 5 flowing out from between optical waveguides 2 from reaching an adhesive surface with the substrate surface of external waveguide film 3. It is.

(A) Step of forming concave surface 20 on the surface of the substrate (b) Step of forming insulating film 14 on the surface of the substrate (c) Step of forming core layer 21 on the surface of concave surface 20 (d) Core (C) forming a circuit layer 6 made of a metal thin film 15 on the substrate surface; and (f) forming a clad layer 22 having an upper end protruding from the substrate surface. A step of attaching the optical element 4 to the substrate 1 so as to be optically coupled to the optical waveguide 2 composed of the layer 21 and the clad layer 22; and (g) a step of filling an underfill 5 between the optical element 4 and the optical waveguide 2. h) A step of attaching the external waveguide film 3 to the substrate 1 by bonding the end of the external waveguide film 3 to the surface of the substrate.

  According to invention of Claim 1, the outflow prevention part formed in the board | substrate surface between an optical element and the edge part of an external waveguide film is an adhesive surface with the board | substrate surface of an external waveguide film when an underfill flows out. Even if the underfill filled between the optical element and the substrate flows through the step of the clad layer and flows toward the external waveguide film due to the capillary phenomenon, the underfill does not reach the film. Since it does not reach the bonding surface, it is possible to prevent a poor connection strength of the external waveguide film, and to obtain a highly reliable photoelectric conversion submount substrate without peeling off the film.

  According to the invention of claim 2, since the outflow prevention part can be formed simultaneously with the formation of the core layer by forming the outflow prevention part with the same material as the core layer, the number of steps for forming the outflow prevention part is increased. Thus, the outflow prevention portion can be formed easily without any problem, and the photoelectric conversion submount substrate can be easily obtained. In addition, because the outflow prevention part is made of the same material as the core layer, the height of the wall of the outflow prevention part can be easily controlled, so it is possible to prevent underfill outflow without waste with the necessary and sufficient amount of material. In addition, the photoelectric conversion submount substrate can be prevented from becoming heavy or bulky.

  According to the invention of claim 3, since the outflow prevention portion can be formed simultaneously with the formation of the cladding layer by forming the outflow prevention portion with the same material as the cladding layer, the number of steps for forming the outflow prevention portion is increased. Thus, the outflow prevention portion can be formed easily without any problem, and the photoelectric conversion submount substrate can be easily obtained. In addition, the outflow prevention part is made of the same material as the cladding layer, so the height of the wall of the outflow prevention part can be easily controlled, so it is possible to prevent underfill outflow without waste with the necessary and sufficient amount of material. In addition, the photoelectric conversion submount substrate can be prevented from becoming heavy or bulky. Furthermore, since the outflow prevention portion is made of the same material as the cladding layer, the outflow prevention portion can be formed without affecting the optical coupling loss.

  According to the invention of claim 4, by forming the outflow prevention portion by the groove, it is possible to store a volume of underfill in the groove and prevent the outflow, so even if the amount of outflow of the underfill increases. The underfill can surely be prevented from reaching the external waveguide film.

  According to the invention of claim 5, since the groove volume is increased by providing the recess in the groove, the amount of the underfill to be stored can be increased, and even if the amount of underfill outflow increases, It is possible to more reliably prevent the underfill from reaching the external waveguide film. In addition, when the concave portion is a through hole penetrating the substrate, the underfill can be discharged to the back surface of the substrate, and even if the amount of outflow of the underfill further increases, the underfill is surely applied to the external waveguide film. It can be prevented from reaching. Moreover, this recessed part can be formed by simple methods, such as a sandblasting process, and can obtain the photoelectric conversion submount board | substrate which prevents the outflow of an underfill easily.

  According to the sixth aspect of the invention, the depth of the groove gradually increases as the distance from the optical waveguide increases, so that the volume of the groove can be increased and the underfill can be flowed and stored along the depth of the groove. Therefore, the underfill can be efficiently discharged and prevented from reaching the film. Further, the depth of the groove can be formed by a simple method such as sandblasting using a gray mask, and a photoelectric conversion submount substrate that prevents outflow of underfill can be easily obtained.

  According to the invention of claim 7, since the insulation between the circuits is ensured by forming the insulating film on the substrate surface, a photoelectric conversion submount substrate having conduction reliability can be obtained. . In addition, since the outflow prevention portion is formed as a groove formed without an insulating film, the outflow prevention portion can be formed by providing a portion where the insulating film is not formed when forming the insulating film. Therefore, the outflow prevention part can be easily formed without increasing the number of steps for forming the outflow prevention part, and the photoelectric conversion submount substrate can be easily obtained. In addition, since the insulating film can also serve as a cladding, a photoelectric conversion submount substrate that does not cause light loss can be easily obtained.

  According to invention of Claim 8, since the outflow prevention part is formed with the metal thin film, since the thickness of this thin film can be made very thin, an outflow prevention part is formed without forming an unnecessary unevenness | corrugation in the substrate surface. Can be formed. In addition, since the metal thin film can be formed of a Ti (titanium) thin film having poor wettability, it is possible to prevent the underfill from flowing through the metal thin film and to improve the outflow prevention effect. is there.

  According to the ninth aspect of the present invention, since the circuit layer and the metal thin film of the outflow prevention portion are made of the same material, the outflow prevention portion can be formed simultaneously with the formation of the circuit layer. The outflow prevention part can be easily formed without increasing the number of steps, and a photoelectric conversion submount substrate can be easily obtained.

  According to the invention of claim 10, since the outflow prevention portion is formed so as to surround the periphery of the optical element, the underfill is surrounded and stored in the outflow prevention portion even when the amount of outfill outflow increases. Therefore, it is possible to prevent the underfill from reaching the external waveguide film by bypassing the outflow prevention portion or the like, thereby further preventing the film from peeling.

  According to the eleventh aspect of the present invention, even when the outflow amount of the underfill increases because the outflow prevention portion is formed from the optical waveguide to the end portion of the substrate, the underfill is used as the outflow prevention portion. Since it can be discharged outside the surface of the substrate along the line, it is possible to prevent the underfill from reaching the external waveguide film by bypassing the outflow prevention part, thereby further preventing the film from peeling. Is.

  According to the invention of claim 12, since the outflow prevention portion can be formed simultaneously with other steps, the outflow prevention portion can be easily formed without increasing the number of steps for forming the outflow prevention portion, and the photoelectric conversion A submount substrate can be easily obtained.

It is a top view which shows an example of the photoelectric conversion submount board | substrate of this invention. (A) is a top view which shows another example same as the above, (b) is a schematic sectional drawing of the principal part. It is a top view which shows another example same as the above. It is a top view which shows another example same as the above. It is a top view which shows another example same as the above. It is a top view which shows another example same as the above. It is a figure which shows another example same as the above, (a) is a II sectional drawing of (b), (b) is a top view. It is a top view which shows another example same as the above. It is a top view which shows another example same as the above. It is a top view which shows another example same as the above. It is a figure which shows an example of the manufacturing process of a photoelectric conversion submount board | substrate, (a)-(l) is sectional drawing. It is an enlarged view of the principal part of a photoelectric conversion submount substrate, (a) is a roll sectional view of (b), and (b) is a perspective view. It is a figure which shows an example of the conventional photoelectric conversion submount board | substrate, (a) is a top view, (b) is a side view.

  Hereinafter, modes for carrying out the present invention will be described.

  FIG. 1 is a plan view showing an example of the photoelectric conversion submount substrate of the present invention. FIG. 12 is an enlarged view of a main part of the photoelectric conversion submount substrate. In FIG. 1, the optical element 4 is indicated by a broken line.

  The photoelectric conversion submount substrate includes a substrate 1, an optical waveguide 2 including a core layer 21 and a cladding layer 22 that covers and seals the core layer 21, an optical element 4 that is optically coupled to the optical waveguide 2, and an optical element. 4 and an optical waveguide 2, and an external waveguide film 3 having an end bonded to the substrate surface.

  The substrate 1 is for forming the optical waveguide 2 on the surface or mounting the optical element 4, and can be formed, for example, as a silicon (Si) substrate. On the surface of the substrate 1, a groove portion for providing the optical waveguide 2 is formed in a linearly recessed manner, and the bottom surface of the groove portion is provided as a recessed surface 20.

  The optical waveguide 2 is for transmitting an optical signal, and includes a core layer 21 and a clad layer 22. As materials for the core layer 21 and the cladding layer 22, for example, a resin composition having a high refractive index can be used as the material for the core layer 21, and a resin composition having a low refractive index can be used as the material for the cladding layer 22. Specifically, examples of the material for the core layer 21 and the clad layer 22 include epoxy resin, acrylic resin, fluorinated resin, and polyimide. For example, in the case of using an epoxy resin, a material having a higher blending ratio of the high refractive index bisphenol type epoxy compound is used as the material of the core layer 21, and a blend of the low refractive index alicyclic epoxy compound is used as the material of the cladding layer 22. The optical waveguide 2 can be configured by using a material with a higher ratio.

  The core layer 21 is linearly formed on the surface of the recessed surface 20 toward the external waveguide 23. The cladding layer 22 surrounds and seals the core layer 21 formed on the concave surface 20 of the substrate 1, and its upper end surface is formed so as to protrude from the substrate surface. Therefore, as shown in the figure, a step X is generated between the cladding layer 22 and the substrate surface.

  The end of the core layer 21 on the side optically coupled to the optical element 4 is formed as an inclined surface 21a for reflecting light, and the recessed surface 20 is also inclined at the same inclination angle in this inclined surface 21a. A light reflecting layer 7 is provided between the inclined surface 21a and the recessed surface 20 facing the inclined surface 21a in order to reflect light efficiently. The light reflecting layer 7 is composed of, for example, a 45 ° mirror formed of a metal thin film.

  The external waveguide film 3 is bonded to the surface of the end portion of the substrate 1 where the core layer 21 is extended. The external waveguide film 3 is provided with an external waveguide 23 that is optically coupled to the core layer 21 and exchanges optical signals with the outside on the surface of the film 24, and an end portion thereof is formed by an adhesive. Bonded to the surface of the substrate 1. That is, the film 24 is disposed above the upper end surface of the cladding layer 22 of the substrate 1 via an adhesive, and the step X enters between the film 24 and the substrate 1 across the end edge of the film 24. It extends in. In the illustrated example, the step X and the edge of the film 24 intersect substantially perpendicularly. Note that an adhesive layer having a thickness higher than the step X is formed in the gap between the substrate 1 and the film 24, and the film 24 is bonded to the substrate 1 so as to be substantially flat.

  The optical element 4 is an element that mutually converts an optical signal and an electrical signal. The optical element 4 is mounted on the substrate 1 so as to be optically coupled to the optical waveguide 2 above the inclined surface 21 a of the core layer 21. In the form of FIG. 1, the optical element 4 is electrically connected by a circuit layer 6 formed of a metal thin film provided on the surface of the substrate 1 and a terminal 6a formed protruding from the surface of the circuit layer 6. It is connected to the.

  That is, the optical waveguide 2 is disposed between the terminal 6 a and another terminal 6 a, and the optical element 4 is attached in contact with the plurality of terminals 6 a so as to straddle the optical waveguide 2. A gap corresponding to the height of the terminal 6 a is formed between the optical element 4 and the optical waveguide 2 so as to be larger than the height of the step X and the thickness of the circuit layer 6. The gap extends from below and extends toward the end of the substrate 1. An underfill 5 is filled between the optical element 4 and the optical waveguide 2 so as to fill this gap.

  The underfill 5 is for bonding the optical element 4 to the substrate 1 for mounting. As the underfill 5, for example, a resin solution is used, and the resin is solidified by evaporating and drying the solvent in the resin solution, and the optical element 4 is fixed to the substrate 1.

  As a material of the underfill 5, for example, a thermosetting epoxy resin, an acrylic resin, a silicone rubber, a silicone gel, or the like can be used.

  In the photoelectric conversion submount substrate as described above, when the underfill 5 in the solution state is filled, this step is caused by the capillary phenomenon of the step X formed by the clad layer 22 and the substrate surface. May flow along X. A thick arrow in FIG. 12B indicates the direction in which the underfill 5 flows. When the underfill 5 flows out and reaches the adhesion surface between the external waveguide film 3 and the substrate 1, the adhesion strength of the external waveguide film 3 is weakened, and a problem that the film 24 peels occurs. Therefore, in the present invention, the underfill 5 is prevented from flowing out onto the substrate surface between the optical element 4 and the end portion of the external waveguide film 3 to reach the adhesive surface with the substrate surface of the external waveguide film 3. An outflow prevention unit 10 is formed.

  In the form of FIG. 1, the outflow prevention portion 10 is formed continuously with the exposed side surface (surface on which the step X is formed) of the cladding layer 22. The outflow prevention portions 10 are provided on the exposed side surfaces on both sides of the cladding layer 22 and are formed as a pair. The outflow prevention unit 10 is formed of, for example, a rectangular wall 11 having a long side arranged in a direction perpendicular to the extending direction of the optical waveguide 2, a groove 12, a metal thin film 15, and the like. It is provided in close contact with X without a gap. And when the underfill 5 flows out by forming the outflow prevention portion 10 on the substrate surface, the flow of the underfill 5 is blocked so that the underfill 5 does not flow toward the external waveguide film 3. Become. In this way, the outflow prevention portion 10 formed on the substrate surface between the optical element 4 and the end portion of the external waveguide film 3 is bonded to the substrate surface of the external waveguide film 3 when the underfill 5 flows out. The underfill 5 filled between the optical element 4 and the substrate 1 flows out toward the external waveguide film 3 through the step X of the cladding layer 22 by capillary action. Even so, the underfill 5 does not reach the film adhesion surface. Therefore, the connection strength defect of the external waveguide film 3 can be prevented, and a highly reliable photoelectric conversion submount substrate can be obtained without the film 24 peeling off. The outflow prevention unit 10 is not limited to a rectangular shape, and may be a square shape such as a trapezoidal shape, an L shape, or an arc shape with the center position of the circle facing the optical element 4.

  FIG. 2A is a plan view showing another example of the photoelectric conversion submount substrate. In this embodiment, the outflow prevention part 10 is formed of a wall-like body 11 that is in close contact with the exposed side surface of the clad layer 22 without gaps and protrudes from the substrate surface. Although the wall-like body 11 can be formed using an appropriate material, in this embodiment, the material of the core layer 21 is used as the material of the wall-like body 11. That is, the outflow prevention part 10 is made of the same material as the core layer 21 and is laminated on the substrate surface to be formed in a wall shape. Thereby, since the outflow prevention part 10 can be formed simultaneously with the formation of the core layer 21, the outflow prevention part 10 can be easily formed without increasing the number of steps for forming the outflow prevention part 10.

  Moreover, since the outflow prevention part 10 consists of the same material as the core layer 21, the height (layer thickness) of the wall of the outflow prevention part 10 can be controlled easily. The wall height is preferably 1 to 10 μm. If the height of the wall is less than 1 μm, the underfill 5 may not be prevented from flowing out. On the other hand, if the height of the wall is 10 μm, there is a sufficient prevention effect, and if it exceeds that height, the optical coupling efficiency may be lowered on the sub-mount substrate side on which the light receiving element is mounted. That is, as shown in the schematic cross-sectional view of the main portion (portion including the light reflection layer 7) in FIG. 2B, when the outflow prevention portion 10 is too high, that is, the core layer 21 is formed high. If too much, light (arrow in the figure) propagating through the core layer 21 does not hit the light reflecting layer 7, but may pass through the head and generate a lot of light "loss". The optical coupling efficiency may be reduced. As described above, a wall-like body can be formed with a necessary and sufficient amount of material without waste, and the outflow of the underfill 5 can be surely prevented, and the photoelectric conversion submount substrate becomes heavy or bulky. It is possible to prevent that.

  FIG. 3 is a plan view showing another example of the photoelectric conversion submount substrate. In this embodiment, the material of the cladding layer 22 is used as the material of the wall-like body 11. That is, the outflow prevention portion 10 is made of the same material as that of the cladding layer 22 and is formed in a wall shape that is laminated on the substrate surface and integrated and connected to the cladding layer 22. Thereby, since the outflow prevention part 10 can be formed simultaneously with the formation of the cladding layer 22, the outflow prevention part 10 can be easily formed without increasing the number of steps for forming the outflow prevention part 10.

  Further, since the outflow prevention part 10 is made of the same material as that of the cladding layer 22, the wall height (layer thickness) of the outflow prevention part 10 can be easily controlled. It is preferable to form the wall with a height of 1 to 20 μm. If the height of the wall is less than 1 μm, the underfill 5 may not be prevented from flowing out. On the other hand, as the height of the wall is higher, the effect of preventing the flow can be expected, but 20 μm is sufficient, and there is a possibility that the wall becomes bulky even if the height is exceeded. As described above, a wall-like body can be formed with a necessary and sufficient amount of material without waste, and the outflow of the underfill 5 can be surely prevented, and the photoelectric conversion submount substrate becomes heavy or bulky. It is possible to prevent that. Furthermore, when the outflow prevention part 10 is formed from the same material as the cladding layer 22, the cladding layer 22 and the outflow prevention part 10 are formed integrally (that is, the outflow prevention part 10 is extended by extending the cladding layer 22). And the wall 11 can be formed firmly fixed to the substrate 1, and even if the clad layer 22 is thick, it does not affect the optical coupling loss. It is possible to form the outflow prevention part 10 having a high wall prevention effect by increasing the height of the wall. That is, as shown in FIG. 2B, there is a possibility that optical coupling loss may occur when the core layer 21 becomes high, but the light does not propagate through the cladding layer 22, so even if the layer becomes high, the optical coupling loss is not affected. . Therefore, it is possible to make the outflow prevention part 10 thicker than when the core layer 21 is used. In practice, the height of the cladding layer 22 is limited by the height of the element, that is, the height of the terminal 6, and the actual terminal height is about 20 μm.

  FIG. 4 is a plan view showing another example of the photoelectric conversion submount substrate. In this embodiment, the outflow prevention unit 10 has a linear shape with its end portion connected to the exposed side surface of the cladding layer 22 and extending in a direction perpendicular to the extending direction of the optical waveguide 2 and recessed in the substrate surface. The groove 12 is formed. The grooves 12 are provided on the exposed side surfaces on both sides of the cladding layer 22, respectively. According to this embodiment, by forming the outflow prevention portion 10 with the groove 12, the underfill 5 corresponding to the volume of the groove 12 can be stored in the groove 12 to prevent the outflow. Even if the number increases, it is possible to reliably prevent the underfill 5 from reaching the external waveguide film 3.

  The depth of the groove 12 is preferably 0.5 to 50 μm, and more preferably about 40 μm. If the groove 12 has a depth of 0.5 μm or more, the underfill 5 can be sufficiently prevented from flowing out. If the depth of the groove 12 is less than 0.5 μm, the outflow prevention effect of the underfill 5 may not be sufficiently obtained. On the other hand, if the depth of the groove 12 exceeds 50 μm, the processing cost increases, which may be uneconomical. It is also preferable to set the depth of the groove 12 to the depth of the optical waveguide 2 (depth from the substrate surface to the recessed surface 20). Thereby, the groove 12 and the optical waveguide 2 can be easily formed simultaneously.

  That is, the groove 12 can be formed simultaneously with a groove portion (waveguide groove) for forming the optical waveguide 2 in the substrate 1 such as a silicon substrate. Therefore, the outflow prevention unit 10 can be easily formed without increasing the number of steps for forming the outflow prevention unit 10. In the illustrated embodiment, the groove 12 is linear, but the groove 12 may be curved or arcuate. A plurality of grooves 12 may be provided.

  FIG. 5 is a plan view showing another example of the photoelectric conversion submount substrate. In this form, in addition to the form of FIG. 4, a recess 13 is provided on the bottom surface of the groove 12 so as to be deeper than the groove 12. In the illustrated example, the recess 13 is provided in a round shape at a position approximately half the length of the groove 12. In this embodiment, since the volume of the groove 12 is increased by providing the recess 13 in the groove 12, the amount of the underfill 5 to be stored can be increased, and the outflow amount of the underfill 5 is increased. However, it is possible to more reliably prevent the underfill 5 from reaching the external waveguide film 3.

  Here, the recess 13 can be formed as a through hole penetrating the substrate 1. In that case, the underfill 5 can be discharged to the back surface of the substrate 1, and even if the outflow amount of the underfill 5 further increases, the underfill 5 can be reliably prevented from reaching the external waveguide film 3. It can be done. And this recessed part 13 can be formed by simple methods, such as a sandblasting process, and can form the outflow prevention part 10 with a high outflow prevention effect easily. In the illustrated embodiment, the recess 13 is round, but the recess 13 may be square. The position where the recess 13 is formed is not limited to that shown in the figure, and the recess 13 may be provided at the end opposite to the side of the groove 12 that is connected to the cladding layer 22. A plurality of recesses 13 may be provided.

  FIG. 6 is a plan view showing another example of the photoelectric conversion submount substrate. In this form, in the form of FIG. 4, the depth of the groove 12 gradually increases as the distance from the optical waveguide 2 increases. That is, the groove 12 is formed in a tapered shape that gradually becomes deeper from one end on the optical waveguide 2 side toward the other end. In the illustrated example, the depth of the groove 12 is indicated by shades of color. The deeper the color, the deeper the groove 12. The groove 12 may be such that the bottom of the groove 12 is linearly inclined and gradually becomes deep, or the bottom of the groove 12 is curved and gradually deepened. The depth of the groove 12 is preferably shallow, that is, the depth of the end connected to the cladding layer 22 is 0.5 μm or more, and the deep portion, that is, the end connected to the cladding layer 22 is The depth of the opposite end is preferably 100 μm or less. If the depth of the shallow portion of the groove 12 is less than 0.5 μm, the underfill 5 may not be sufficiently prevented from flowing out. On the other hand, if the depth of the deep groove 12 exceeds 100 μm, the processing cost may increase, which may be uneconomical. However, from the viewpoint of preventing the underfill 5 from flowing out, the deeper the depth of the groove 12, the better. For example, the groove 12 may penetrate the substrate 1 at the deepest position.

  In this configuration, the depth of the groove 12 gradually increases, so that the volume of the groove 12 can be increased and the underfill 5 can be flowed and stored along the depth of the groove 12. 5 can be efficiently discharged and prevented from reaching the film 24. The depth of the groove 12 can be adjusted by a simple method such as sandblasting using a gray mask, and the outflow prevention portion 10 having a high outflow prevention effect can be easily formed. is there.

  7A and 7B are diagrams showing another example of the photoelectric conversion submount substrate, in which FIG. 7A is a cross-sectional view taken along the line (b), and FIG. 7B is a plan view. In this embodiment, an insulating film 14 is formed on the surface of the substrate 1, and the outflow prevention unit 10 is formed as a groove 12 formed without the insulating film 14 on the substrate surface. The shape of the groove 12 can be the same as that shown in FIG. In this embodiment, since the insulating film 14 is formed on the surface of the substrate, the insulation between the circuits is ensured, so that a photoelectric conversion submount substrate having conduction reliability can be obtained. The outflow prevention unit 10 may be formed by providing a portion where the insulating film 14 is not formed when the insulating film 14 is formed, or after the insulating film 14 is formed on the entire surface of the substrate, the outflow prevention unit 10 may be formed. Alternatively, the insulating film 14 may be removed by using a resist in which only a portion to be formed is opened. When the outflow prevention unit 10 is formed by providing a portion where the insulating film 14 is not formed, the outflow prevention unit 10 can be easily formed without increasing the number of steps for forming the outflow prevention unit 10. On the other hand, when the outflow prevention part 10 is formed by removing the insulating film 14, a resist having an opening for forming the outflow prevention part 10 is provided on the substrate surface, and dry etching is performed to remove the insulating film 14 in the opening part. And it can carry out by the method of removing the resist of the substrate surface. The insulating film 14 can also serve as a cladding. That is, as shown in FIG. 7A, the insulating film 14 is disposed between the core layer 21 and the concave surface 20 of the substrate surface, and the insulating film 14 has a lower refractive index than the core layer 21. Therefore, since the insulating film 14 can function as a clad, the core layer 21 can be easily surrounded by a clad material constituted by the insulating film 14 and the clad layer 22, and a photoelectric conversion submount that does not cause optical loss. A substrate can be easily obtained. As a material for forming the insulating film 14, for example, a silicon oxide film (Si oxide film) can be used. The depth of the groove 12 is equal to the thickness of the insulating film 14, and can be, for example, 0.5 to 50 μm.

  FIG. 8 is a plan view showing another example of the photoelectric conversion submount substrate. In this embodiment, the outflow prevention part 10 is formed by being laminated as a metal thin film 15 on the substrate surface. The metal thin film 15 is formed as a rectangular thin film layer having a long side arranged in a direction perpendicular to the extending direction of the optical waveguide 2 in close contact with the exposed side surface of the cladding layer 22. In this embodiment, since the outflow prevention portion 10 is formed of the metal thin film 15, the thickness of the thin film can be extremely reduced, so that the outflow prevention portion can be formed without forming unnecessary irregularities on the substrate surface. 10 can be formed. The thickness of the metal thin film 15 can be preferably 1 μm or less. Thereby, unnecessary unevenness can be further eliminated. The lower limit of the thickness of the metal thin film 15 is substantially 0.05 μm. Since the metal thin film 15 can be formed of a Ti (titanium) thin film having poor wettability, the underfill 5 does not flow across the surface of the metal thin film 15. That is, since the underfill 5 is prevented from flowing out by utilizing the poor wettability of the metal thin film 15, the thickness of the layer is increased like a wall as compared with the case where the wall is formed and physically blocked. There is no need, and the outflow prevention part 10 can be formed with a thin layer. And since the outflow of the underfill 5 is prevented using wettability, the outflow prevention effect can be improved.

  In the form of FIG. 8, it is preferable that the circuit layer 6 formed on the substrate surface and the metal thin film 15 forming the outflow prevention portion 10 are made of the same material. Thereby, since the outflow prevention part 10 can be formed simultaneously with the formation of the circuit layer 6, the outflow prevention part 10 can be easily formed without increasing the number of steps for forming the outflow prevention part 10.

  FIG. 9 is a plan view showing another example of the photoelectric conversion submount substrate. In this embodiment, the outflow prevention unit 10 is formed on the surface of the substrate so as to surround the optical element 4. The outflow prevention unit 10 may be the wall-like body 11 described above, the groove 12, or the metal thin film 15. According to this embodiment, since the outflow prevention unit 10 is formed so as to surround the optical element 4, the outflow amount of the underfill 5 is increased, or the outflow prevention unit 10 is formed of a highly wettable material. Even in this case, since the underfill 5 can be surrounded and stored in the outflow prevention unit 10, the underfill 5 is prevented from reaching the external waveguide film 3 by bypassing the outflow prevention unit 10, etc. The peeling of the film 24 can be further prevented. In the example shown in the figure, the periphery of the optical element 4 is enclosed in a square shape, but the periphery may be enclosed in a circle. By the way, when the outflow prevention part 10 is formed with the metal thin film 15, especially when the outflow prevention part 10 is formed with the same metal thin film 15 as the circuit layer 6, the part through which the circuit layer 6 passes so as not to short-circuit the circuit. In this case, the outflow prevention unit 10 is not provided, and the separated outflow prevention unit 10 is preferably surrounded by the optical element 4.

  FIG. 10 is a plan view showing another example of the photoelectric conversion submount substrate. In this embodiment, the outflow prevention unit 10 is formed from the optical waveguide 2 to the end of the substrate 1. That is, the outflow prevention unit 10 is formed such that one end is connected to the exposed side surface of the cladding layer 22 and the other end extends to the tip of the end of the substrate 1 in a direction perpendicular to the extending direction of the optical waveguide 2. ing. The outflow prevention unit 10 may be the wall-like body 11 described above, the groove 12, or the metal thin film 15. According to this embodiment, even when the outflow amount of the underfill 5 increases or the outflow prevention portion 10 is formed of a material having high wettability, the underfill 5 is moved along the outflow prevention portion 10 from the surface of the substrate. Since it can be discharged to the outside, it is possible to prevent the underfill 5 from reaching the external waveguide film 3 by bypassing the outflow prevention portion 10 or the like, and further prevent the film 24 from peeling off. is there.

  Next, manufacture of a photoelectric conversion submount substrate will be described.

  FIG. 11 is a cross-sectional view showing a part of the manufacturing process of the photoelectric conversion submount substrate (production of the optical waveguide 2). FIGS. 11A to 11D show a state where a groove for providing the optical waveguide 2 is processed on the surface of the substrate 1. In processing the surface of the substrate 1, first, a mask 31 for forming the optical waveguide 2 is formed on the surface of the substrate 1 as shown in FIG. Next, as shown in (b), the substrate 1 is recessed by anisotropic etching, and the recessed surface 20 for forming the optical waveguide 2 is formed. Then, as shown in (c), the mask 31 is removed, and then, as shown in (d), the insulating film 14 is laminated on the surface of the substrate 1 to be formed.

  FIGS. 11E to 11H show how the core layer 21 is produced. In preparation of the core layer 21, first, as shown in (e), the core resin composition 32 which forms the core layer 21 is apply | coated on the recessed surface 20, and preheating (PB) is carried out. Next, after flattening and flattening the upper surface of the core layer 21 as shown in (f), patterning is performed with a mask 31 and the resin is cured with energy rays such as UV as shown in (g). . And as shown by (h), the core layer 21 can be produced by removing the insoluble core resin composition 32 by development and heating (PDB). Before forming the core layer 21, the light reflecting layer 7 can be provided by forming a metal thin film on the surface of the recessed surface 20 where the inclined surface 21 a of the core layer 21 is formed.

  11 (i) to 11 (l) show how the clad layer 22 is produced. In producing the clad layer 22, first, as shown in (i), a clad resin composition 33 for forming the clad layer 22 is applied and pre-heated (PB). Next, as shown in (j), the flattening press is performed to make the upper surface of the clad layer 22 project higher than the surface of the substrate, followed by patterning with a mask 31 as shown in (k). The resin is cured with energy rays such as UV. Then, as shown in (l), the clad layer 22 can be produced by removing the insoluble clad resin composition 33 by development and heating (PDB).

  In this way, the substrate 1 on which the optical waveguide 2 constituted by the core layer 21 and the cladding layer 22 is formed is formed. Then, the circuit layer 6 is formed on the substrate 1, the optical element 4 is attached to the terminal 6 a formed on the surface of the circuit layer 6, and the underfill 5 is filled between the optical element 4 and the optical waveguide 2. On the other hand, the external waveguide film 3 is adhered to the substrate surface at the end of the substrate 1 where the optical waveguide 2 is extended with an adhesive. As the adhesive, a photocurable resin or the like can be used. Note that a gap is formed between the substrate surface and the film 24 by the height of the step X of the clad layer 22, and this gap is filled with an adhesive to form an adhesive layer. The film 24 is usually attached after the optical element 4 is mounted and the underfill 5 is filled. At this time, since the underfill 6 is prevented from flowing out by the outflow prevention unit 10 and does not reach the portion where the film 24 is to be bonded, the film 24 can be securely bonded to the substrate 1. In this manner, a photoelectric conversion submount substrate on which the optical element 4 is mounted and the external waveguide film 3 is provided can be obtained.

  The upper end surface of the clad layer 22 manufactured as described above is higher than the substrate surface, and a step X is generated. That is, since the respective resins forming the core layer 21 and the clad layer 22 are flattened by pressing, the upper end surface of the core layer 21 is substantially flush with the surface of the substrate 1 so as to surround the core layer 21. The upper end surface of the cladding layer 22 protrudes from the surface of the substrate 1. The step X is caused by the protrusion of the upper end surface of the cladding layer 22, and this step X causes the underfill 5 to flow out. However, in the present invention, as described above, the outflow prevention portion 10 is formed to prevent the underfill 5 from flowing out.

  And formation of outflow prevention part 10 is preferably performed in a part of manufacturing process of a photoelectric conversion submount substrate.

  For example, when the outflow prevention portion 10 of the wall-like body 11 is the same as the material of the core layer 21 as in the example of the form of FIG. 2, the formation process of the core layer 21 of FIGS. Can be formed simultaneously. That is, in (e), the core resin composition 32 is also applied to the part where the outflow prevention part 10 is formed. Then, the patterning of the mask 31 shown in (g) is made into a pattern that forms the outflow prevention part 10 together with the core layer 21. Thus, the outflow prevention part 10 can be formed simultaneously with the core layer 21, and the outflow prevention part 10 can be formed without increasing the number of steps.

  When the outflow prevention portion 10 of the wall-like body 11 is made of the same material as that of the cladding layer 22 as in the embodiment of FIG. 3, the formation process of the cladding layer 22 in FIGS. Can be formed. That is, in (i), the clad resin composition 33 is also applied to the portion where the outflow prevention portion 10 is formed. Then, the patterning of the mask 31 shown in (j) is made into a pattern for forming the outflow prevention portion 10 together with the cladding layer 22. In this way, the outflow prevention part 10 can be formed simultaneously with the cladding layer 22, and the outflow prevention part 10 can be formed without increasing the number of steps.

  Moreover, when the outflow prevention part 10 is formed by the groove 12 as in the form of FIG. 4, the outflow prevention part 10 is formed by the processing steps of the surface of the substrate 1 shown in FIGS. 11 (a) to 11 (c). be able to. That is, the patterning of the mask 31 shown in FIG. Thereby, the outflow prevention part 10 can be formed simultaneously with the recessed surface 20 for forming the optical waveguide 2, and the outflow prevention part 10 can be formed without increasing the number of steps. In the case where the recess 12 is provided in the groove 12 as in the form of FIG. 5, the bottom of the groove 12 can be formed by sandblasting or the like. The formation of the recess 13 may be performed during the processing step of the surface of the substrate 1 or may be performed after the optical waveguide 2 is formed. When the depth of the groove 12 is gradually increased as shown in FIG. 6, the groove 12 is formed in advance by patterning as described above, and the groove 12 is deepened by sandblasting using a gray mask. It can be formed by adjusting the thickness and shaving.

  Further, as shown in FIG. 7, when the insulating film 14 is not formed and the groove 12 is provided to form the outflow prevention portion 10, the outflow prevention is performed in the step of forming the insulating film 14 shown in FIG. The part 10 can be formed. That is, in (d), the part where the outflow prevention part 10 is to be formed is covered with a mask, patterned to deposit the insulating film 14, and the mask is removed. Thereby, the outflow prevention part 10 can be formed simultaneously with the insulating film 14, and the outflow prevention part 10 can be formed without increasing the number of steps.

  Further, in the embodiment of FIG. 8, the outflow prevention part 10 can be formed in the process of forming the circuit layer 6. In this embodiment, the outflow prevention unit 10 is formed as a metal thin film 15 made of the same material as the circuit layer 6, and patterning is performed to form the outflow prevention unit 10 together with the circuit layer 6 when forming the circuit layer 6. The circuit layer 6 and the metal thin film 15 are laminated at the same time. Thereby, the outflow prevention part 10 can be formed simultaneously with the insulating film 14, and the outflow prevention part 10 can be formed without increasing the number of steps.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Optical waveguide 3 External waveguide film 4 Optical element 5 Underfill 6 Circuit layer 7 Light reflection layer 10 Outflow prevention part 11 Wall-like body 12 Groove 13 Concave 14 Insulating film 15 Metal thin film 20 Concave surface 21 Core layer 22 Clad Layer 23 External waveguide 24 Film 31 Mask

Claims (12)

  An optical waveguide comprising a substrate, a core layer formed on a concave surface of the substrate surface, and a clad layer that covers and seals the core layer and has an upper end surface protruding from the substrate surface; and an optical waveguide; An optical element for optical coupling; an underfill filled between the optical element and the optical waveguide; and an external waveguide film having an end bonded to the substrate surface. The underflow flowing out from between the optical element and the optical waveguide is formed on the substrate surface between the substrate and the outflow prevention portion for preventing the underfill from reaching the adhesive surface with the substrate surface of the external waveguide film. A photoelectric conversion submount substrate.   The photoelectric conversion submount substrate according to claim 1, wherein the outflow prevention portion is made of the same material as the core layer and is formed in a wall shape on the substrate surface.   2. The photoelectric conversion submount substrate according to claim 1, wherein the outflow prevention portion is made of the same material as that of the cladding layer and is formed in a wall shape on the substrate surface.   The photoelectric conversion submount substrate according to claim 1, wherein the outflow prevention portion is a groove formed on the substrate surface.   The photoelectric conversion submount substrate according to claim 4, wherein a recess is provided in the groove.   The photoelectric conversion submount substrate according to claim 4, wherein the depth of the groove gradually increases as the distance from the optical waveguide increases.   2. The photoelectric conversion submount substrate according to claim 1, wherein the substrate has an insulating film formed on the surface, and the outflow prevention portion is a groove formed without an insulating film provided on the substrate surface. .   The photoelectric conversion submount substrate according to claim 1, wherein the outflow prevention portion is a metal thin film formed on the substrate surface.   9. The photoelectric conversion submount substrate according to claim 8, wherein a circuit layer is provided on the substrate surface, and the metal thin film is made of the same material as the circuit layer.   The photoelectric conversion submount substrate according to claim 1, wherein the outflow prevention portion is formed to surround the periphery of the optical element.   The photoelectric conversion submount substrate according to claim 1, wherein the outflow prevention portion is formed from the optical waveguide to an end portion of the substrate. A process including the following (a), (c), (d), (f), (g), and (h), and a process including (a), (b), (c), (d), (f), (g), and (h) Or (a), (c), (d), (e), (f), (g), and a method for producing a photoelectric conversion submount substrate according to any one of claims 1 to 11 by a process comprising (h). (A), (b), (c), (d), and (e), the optical element and the optical waveguide are formed on the substrate surface between the optical element and the end portion of the external waveguide film. A method for manufacturing a photoelectric conversion submount substrate, comprising: forming an outflow prevention portion that prevents an underfill that has flowed out from between the layers from reaching an adhesion surface of the external waveguide film to the substrate surface.
(A) Step of forming a concave surface on the substrate surface (b) Step of forming an insulating film on the substrate surface (c) Step of forming a core layer on the surface of the concave surface (d) Covering the core layer (C) forming a circuit layer made of a metal thin film on the substrate surface; and (f) comprising a core layer and a cladding layer. A step of attaching an optical element to the substrate so as to be optically coupled to the optical waveguide. (G) A step of filling an underfill between the optical element and the optical waveguide. (H) Adhering an end portion of the external waveguide film to the surface of the substrate. Attaching the external waveguide film to the substrate

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