JP2005215054A - Optical waveguide and its manufacturing method and optical circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide in which the propagation angle of light which propagates the inside of the optical waveguide can be set freely and moreover flatness of the surface of the optical waveguide can be sufficiently secured without increasing the number of processes and also internal stress is suppressed from being concentrated on its core and to provide its manufacturing method and an optical circuit board. <P>SOLUTION: The optical waveguide is configured in such a manner that a 2nd organic material layer is layered on a lower clad layer formed on a substrate, and a core part 3 and a peripheral part 5 which are separated mutually and which consist of one and the same organic material layer are formed by removing a part of the 2nd organic material layer so as to surround the core part, and an upper clad layer 4 is layered on the core part 3 and the peripheral part 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical waveguide, a method of manufacturing the same, and an optical circuit board. More specifically, the present invention relates to an optical waveguide in which the surface of an upper clad layer formed on a core portion that guides light is flattened, and the manufacture thereof. The present invention relates to a method and an optical circuit board using the optical waveguide.

  As the processor clock frequency has been increased to several GHz, it has become difficult to realize large-capacity transmission by the influence of electromagnetic noise and the like in the conventional wiring using electrical wiring. In recent years, various methods relating to optical interconnection have been proposed in which, for example, an optical wiring that is not affected by electromagnetic noise or the like is produced using an optical waveguide to increase transmission capacity.

  By the way, until now, quartz materials are often used for optical waveguides, and optical waveguides using quartz materials are difficult to manufacture, and light receiving elements and light emitting elements (hereinafter collectively referred to as light receiving and emitting elements). In addition, there are various difficulties in practical use such as high accuracy required for coupling between the optical waveguide and the optical waveguide, and the structure is expensive. For this reason, in recent years, various studies have been made on optical waveguides using organic materials.

  When an organic material is used for the optical waveguide, there is an advantage that the size (core size) of the core (core portion) can be increased to about several tens of μm, which is about 10 times or more, compared with the case where a quartz material is used. is there. As a result, since the light emitting / receiving element and the optical waveguide can be easily coupled, an inexpensive and practical optical wiring that does not require high accuracy can be obtained.

  Thus, when an organic material is used for the core of the optical waveguide, the core size can be increased. However, when the core method is increased, the step of the clad (upper clad layer) on the core caused by the core becomes remarkable. Therefore, there is a problem that the flatness of the surface of the optical waveguide is remarkably lowered. In an optical circuit board using an optical waveguide, chip parts such as resistors and capacitors and electrical wiring are formed on the optical waveguide. For this reason, there is a problem that a decrease in flatness of the surface of the optical waveguide leads to a defective mounting of a chip component provided on the optical waveguide or a defective formation of metal wiring.

  Therefore, a planarizing layer is provided on the surface of the upper clad layer of the optical waveguide (see, for example, Patent Document 1), or a core and a clad adjacent to the core using a photosensitive organic material whose characteristics are changed by light irradiation ( A method of flattening the surface of the optical waveguide, such as a method of manufacturing an optical waveguide (see, for example, Patent Document 2) by forming a side cladding portion or the like, has been actively studied.

  FIG. 8A is a cross-sectional view showing a schematic configuration of the main part of the optical waveguide described in Patent Document 1, and FIG. 8B is a schematic configuration of the main part of the optical waveguide shown in FIG. FIG.

  As shown in FIG. 8, in the optical waveguide described in Patent Document 1, a lower clad layer 102 is provided on a substrate 101, and a core layer 103 patterned in a rectangular shape is provided as a core portion on the lower clad layer 102. The upper clad layer 104 and the planarization layer 112 are provided in this order on the lower clad layer 102 and the core layer 103 so as to cover the core layer 103.

  Since the planarization layer 112 is provided so as to fill the step formed on the upper surface of the upper cladding layer 104 by the core layer 103, the upper portion 113 of the core layer 103 in the planarization layer 112 has almost no unevenness, The upper surface of the planarizing layer 112 is substantially flat.

  The lower cladding layer 102, the core layer 103, the upper cladding layer 104, and the planarization layer 112 are all made of polyimide, and the core layer 103 formed by etching the peripheral portion by reactive ion etching (RIE) has a high dimension. The width is about 8 μm. The refractive index of the core layer 103 is about 0.5% larger than the refractive indexes of the lower cladding layer 102 and the upper cladding layer 104, and the planarization layer 112 has a glass transition more than the polyimide used for the upper cladding layer 104. It is made of polyimide having a low temperature.

9A to 9E are cross-sectional views showing the optical waveguide manufacturing process described in Patent Document 2. FIG. First, as shown in FIG. 9A, an organic material is applied to the surface of the substrate 201 by a spin coating method, and baking is performed to form a buffer layer (lower cladding layer) 202. Further, as shown in FIG. 9B, a photosensitive organic material layer 205 is formed on the buffer layer 202 by a method similar to the method of forming the buffer layer 202. Next, as shown in FIG. 9C, a CO ² laser mask 214 is placed on the surface of the photosensitive organic material layer 205 and irradiated with CO ² laser light 216. The CO ² laser mask 214 has a pattern portion 215 that does not transmit the CO ² laser light 216.

A part of the material constituting the photosensitive organic material layer 205 evaporates in accordance with the amount of energy of the irradiated CO ² laser beam 216, so that the photosensitive layer is irradiated with the CO ² laser beam 216. The refractive index of the transmission region of the CO ² laser beam 216 in the organic material layer 205 can be changed. However, in the photosensitive organic material layer 205, a portion corresponding to the lower of the pattern portion 215, i.e., the portion to become a core portion 203 shown in FIG. 9 (d), since the CO ² laser beam 216 is not transmitted, refracted The rate does not change. For this reason, when the CO ² laser mask 214 is removed, as shown in FIG. 9D, the core portion 203 and the side cladding portion 206 having different refractive indexes can be obtained. Since the surfaces of the core part 203 and the side clad part 206 formed in this way are uniformly flat, the upper clad is formed on the core part 203 and the side clad part 206 as shown in FIG. When the layer 204 is formed, an optical waveguide having a planarized surface can be manufactured.
Japanese Laid-Open Patent Publication No. 2001-074958 (Publication Date: March 23, 2001) JP-A-10-232323 (publication date: September 2, 1998)

  However, in the method described in Patent Document 1, since the planarization layer 112 is provided on the upper clad layer 104, it is necessary to apply an organic material on the upper clad layer 104, and perform a heating / drying process. There is a problem that increases. Further, since the planarization layer 112 is further provided on the upper surface of the upper clad layer 104, the distance from the optical waveguide surface to the core layer 103 is increased, so that the light emitting and receiving elements and the core layer disposed on the optical waveguide are increased. Another problem arises in that it is difficult to directly optically couple to the 103.

  Further, in the method described in Patent Document 2, since the core portion 203 and the side clad portion 206 are formed by utilizing the structural change of the organic material by light irradiation, the photosensitive organic material whose structure is changed by light irradiation. There is a problem that it can be applied only when an optical waveguide is manufactured using the material, and cannot be applied when an organic material having no photosensitivity such as polyimide is used. Further, since the side clad portion 206 is formed by utilizing the decrease in the refractive index of the region irradiated with light, it is difficult to freely set the refractive index difference between the core portion 203 and the side clad portion 206. The propagation angle of the light beam propagating in the waveguide is limited. For this reason, even if the size of the core portion 203 of the optical waveguide is increased by using an organic material, the optical waveguide cannot propagate a light beam having a large propagation angle, and sufficiently obtains the effect of expanding the core size. I can't.

  In addition, in order to increase the propagation angle of light propagating in the optical waveguide, the organic material around the core is removed by wet etching with an alkaline solution or the like by utilizing the fact that the region irradiated with light becomes soluble. Thus, if the core part 203 is formed, the process can be simplified and the cost can be reduced as compared with the method using a vacuum apparatus such as RIE as shown in Patent Document 1. However, in this case, since a step is generated on the upper surface of the upper clad layer covering the core portion 203, another method for flattening the upper clad layer 204 needs to be studied as shown in Patent Document 1.

  Furthermore, in the optical waveguide formed by any of the above methods, in the planar region having the core (core portion), the portion other than the core (region) removes all the organic material used for forming the core, or The ratio of the organic material that forms the core to the entire planar area is small because the characteristics are changed (modified), such as by reducing the refractive index. The clad layer 104 and the side clad portion 206) are occupied by organic materials. For this reason, in the conventional optical waveguide, the influence of the organic material which comprises a clad becomes dominant in the plane area | region containing a core. Therefore, for example, when the thermal expansion coefficient of the organic material forming the cladding is larger than the thermal expansion coefficient of the organic material forming the core, the thermal expansion coefficient of the organic material forming the cladding in the planar region including the core is Since the influence becomes dominant, there is a problem that internal stress concentrates on the core. As a result, the light beam confined in the core of the optical waveguide leaks to the outside and the propagation loss of the light beam increases, or in some cases, a part of the core breaks and the light beam cannot be propagated. Occurs.

  The present invention has been made in view of the above-mentioned problems, and its object is to freely set the propagation angle of the light beam propagating in the optical waveguide, and to perform the optical operation without increasing the number of steps. An object of the present invention is to provide an optical waveguide, a method for manufacturing the same, and an optical circuit board that can sufficiently ensure the flatness of the surface of the waveguide and can suppress the concentration of internal stress on the core.

  In order to solve the above problems, an optical waveguide according to the present invention is an optical waveguide comprising a core part forming layer having a core part that propagates light and a clad layer covering the core part forming layer. The layer is characterized by comprising a core part and a peripheral part made of the same organic material as the core part and provided separately from the core part so as to surround the side surface of the core part.

  Further, in order to solve the above problems, the optical waveguide of the present invention comprises a plurality of the core parts, and is made of the same organic material as the core part between adjacent core parts, It is characterized in that a peripheral portion provided apart from the core portion is provided.

  Furthermore, the optical waveguide of the present invention is characterized in that the same organic material as the organic material forming the clad layer covering the core part forming layer is filled between the core part and the peripheral part.

  In order to solve the above problems, the optical waveguide of the present invention is filled with the same organic material as the organic material forming the cladding layer covering the core portion forming layer between the core portion and the peripheral portion. It is characterized by having.

  The optical circuit board of the present invention is characterized in that the optical waveguide according to the present invention is provided in order to solve the above problems.

  An optical waveguide manufacturing method of the present invention is a method for manufacturing an optical waveguide comprising a core part forming layer having a core part for propagating light, and a clad layer covering the core part forming layer. The groove part is formed in the organic material layer forming the part so as to surround the region to be the core part, and the groove part is made of the same organic material as the core part and surrounds the side surface of the core part. And a step of forming a peripheral portion provided apart from the core portion, and a step of forming a clad layer so as to cover the core portion and the peripheral portion.

In the optical waveguide of the present invention, as described above, the core part forming layer is made of the same organic material as the core part and the core part, and is provided separately from the core part so as to surround the side surface of the core part. By providing the peripheral portion, the core portion and the peripheral portion have substantially the same height so as to form the same plane. Therefore, according to the above configuration, it is not always necessary to provide a planarizing layer on the cladding layer, and a complicated process is not required to planarize the surface of the cladding layer, thereby increasing the number of processes. Therefore, the flatness of the upper surface of the optical waveguide after forming the cladding layer, that is, the surface of the cladding layer can be sufficiently ensured. According to the above configuration, as disclosed in Patent Document 2, In the planar region having the core part, the core part and the side cladding part are formed by partially altering the organic material layer forming the core part, for example, by reducing the refractive index of the part (area) other than the core part. The organic material that can be used for forming the core portion is not limited as in the case, and the refractive index and the refractive index difference can be freely set. Can be freely set.

  And according to said structure, the ratio for which the organic material which forms a core part in the plane area | region which has a core part, ie, the said core part formation layer, is remarkably large compared with the said patent documents 1 and 2, Concentration of internal stress on the core portion can be suppressed. For this reason, according to said structure, there exists an effect that the deformation | transformation and damage of a core part can be prevented, and the optical waveguide which does not have the light leakage from a core part and a propagation loss can be provided.

  Furthermore, according to the above configuration, since the film thickness variation on the surface of the cladding layer can be reduced, the amount of the organic material used for forming the cladding layer can be reduced. For this reason, according to said structure, cost reduction is possible, and there exists an effect that the time required for manufacture of the said optical waveguide can be shortened, such as shortening of sintering time. .

  Further, as described above, the optical waveguide according to the present invention includes the core portion forming layer including a plurality of the core portions, and is formed of the same organic material as the core portion between the adjacent core portions. Is provided with a peripheral portion provided so as to be spaced apart, so that when a plurality of light emitting / receiving elements are optically coupled to the core part, the light receiving / emitting elements do not interfere with each other. Even if it arrange | positions with sufficient space | interval, there exists an effect that it becomes possible to fully ensure the flatness of the said clad layer surface.

Further, as described above, the optical waveguide of the present invention is filled with the same organic material as the organic material forming the cladding layer covering the core portion forming layer between the core portion and the peripheral portion. ,
It is possible to more reliably prevent the light beam propagating through the core part from propagating to the peripheral part. Further, according to the above configuration, when forming the clad layer, the organic material for forming the clad layer can be filled between the core portion and the peripheral portion, so that the organic material is newly filled. There is no need to do this, and the effect of simplifying the manufacturing process of the optical waveguide is also achieved. Furthermore, according to the above configuration, the organic material forming the cladding layer is filled between the core portion and the peripheral portion, so that the refractive index difference can be adjusted more freely. Play together.

  Moreover, since the optical circuit board of the present invention includes the optical waveguide according to the present invention as described above, the propagation angle of the light beam propagating in the optical waveguide can be freely set, and the process It is possible to provide an optical circuit board that can sufficiently ensure the flatness of the surface of the optical waveguide without increasing the number and can suppress the concentration of internal stress on the core. In addition, according to the above configuration, since the optical circuit board is excellent in the flatness of the surface of the optical waveguide, it is possible to prevent defective connection of chip parts and metal wiring provided on the optical waveguide. Play.

  As described above, the optical waveguide manufacturing method of the present invention is the same as the core portion by forming the groove portion in the organic material layer forming the core portion so as to surround the region to be the core portion. A step of forming a peripheral portion that is separated from the core portion by the groove portion so as to surround the side surface of the core portion, and a cladding layer is formed so as to cover the core portion and the peripheral portion. The organic coupling with the process makes it possible to ensure sufficient flatness of the surface of the optical waveguide without increasing the number of processes, and to freely set the propagation angle of the light beam propagating in the optical waveguide. It is possible to easily provide an optical waveguide that can suppress the concentration of internal stress on the core (core).

  Further, according to the above configuration, the flatness of the surface of the optical waveguide can be sufficiently ensured. Therefore, even when a chip component or a metal wiring is provided on the optical waveguide, the chip component is poorly mounted or the wiring is poorly formed. And the like, and it is not necessary to provide a flattening layer on the cladding layer, so that the manufacturing process of the optical waveguide can be shortened.

  Further, according to the above method, since the film thickness variation on the surface of the cladding layer can be reduced, the amount of the organic material used for forming the cladding layer can be reduced. For this reason, according to said structure, cost reduction is possible, and there exists an effect that the time required for manufacture of the said optical waveguide can be shortened, such as shortening of sintering time. .

[Embodiment 1]
An embodiment of the present invention will be described below with reference to FIGS.

  Fig.1 (a) is a top view which shows the schematic structure of the optical waveguide concerning one Embodiment of this invention by a partial fracture | rupture, FIG.1 (b) is A of the optical waveguide shown to Fig.1 (a). FIG.

  As shown in FIG. 1B, the optical waveguide (optical waveguide substrate) according to the present embodiment includes a core portion (core) 3 that propagates light and a cladding portion (cladding) that surrounds the core portion 3. A lower clad layer 2, a side clad portion 6, and an upper clad layer 4; a core portion forming layer 7 including a lower clad layer 2, a core portion 3, a peripheral portion 5, and a side clad portion 6; The upper cladding layer 4 is laminated in this order.

  The lower clad layer 2, the core portion forming layer 7, and the upper clad layer 4 are all made of an organic material such as polyimide or polysilane, and the core portion 3 and each clad portion have a difference in refractive index between them. Thus, they are formed of organic materials having different refractive indexes.

  On the other hand, the core portion 3 and the peripheral portion 5 formed on the lower clad layer 2 are made of the same organic material, and as shown in FIGS. 3 are provided so as to be separated from each other so that the light beams propagating through the beam 3 do not propagate to the peripheral portion 5. As will be described later, the core portion 3 and the peripheral portion 5 are formed on the organic material layer that forms the core portion 3 and the peripheral portion 5 in the core portion forming layer 7, that is, on the lower cladding layer 2 that is the first organic material layer. In the second organic material layer provided in, the groove portions 10 having a width of about several μm to several tens of μm are provided so as to surround the core portion 3 so as to be separated from each other.

  The side clad portion 6 is formed by filling the groove portion 10 with the organic material constituting the upper clad layer 4 as the third organic material layer flowing into the groove portion 10. Thus, the side clad portion 6 surrounds the periphery (side surface) of the core portion 3 and is interposed between the core portion 3 and the peripheral portion 5 so as to separate the core portion 3 and the peripheral portion 5. Is provided.

  In addition, the core part 3 propagates the light from a light source (for example, light emitting element) in the longitudinal direction of the core part 3, and emits the light from the longitudinal end face on the opposite side to the longitudinal end face on the incident side. ing. For this reason, for example, as shown in FIG. 1A, the optical waveguide includes a mirror 9 for converting the optical path of the light beam propagating through the core portion 3 to the longitudinal end portion of the core portion 3 as necessary. 9 (for example, a 45-degree mirror), and using the mirrors 9 and 9, light from the light emitting element disposed on the upper clad layer 4 is passed through the core portion 3 onto the upper clad layer 4 You may guide to the arrange | positioned light receiving element. When the mirrors 9 and 9 are formed in this way, as shown in FIG. 1A, an optical waveguide in which a groove portion 10 is provided not only in the core portion 3 but also around the core portion 3 including the mirrors 9 and 9. With the structure, even when the mirrors 9 and 9 are provided, the effects of the present invention described later can be obtained.

  In the present embodiment, the film thickness of the lower cladding layer 2 is set to be in the range of several μm to several tens of μm. If the film thickness of the lower cladding layer 2 is about several μm to several tens of μm, it is possible to confine the light beam propagating through the core portion 3.

  Further, the thickness of the core portion forming layer 7, particularly the size of the core portion 3 is not particularly limited, but the thickness of the core portion 3 is about several μm to several tens of μm, specifically It is desirable to set it within a range of 5 μm to 30 μm, preferably within a range of 10 μm to 20 μm. When the film thickness of the core part 3 is too thick, there are problems such as a long time for pre-post baking and RIE processing and an increase in internal stress. Further, the width in the longitudinal direction of the core portion 3 is not particularly limited, and can be set according to the optical circuit board using the optical waveguide of the present invention. Further, the width of the core portion 3 in the short direction is set to be about several μm to several tens of μm, specifically within a range of 5 μm to 30 μm, and preferably within a range of 10 μm to 20 μm. Is desirable. When the width of the core portion 3 in the short direction is within this range, light can efficiently pass through the core portion 3.

  In addition, the longitudinal direction of the core part 3, ie, a cross section perpendicular | vertical to a light propagation direction is not specifically limited, However, It is preferable that it is a square. Thereby, it is possible to improve the propagation efficiency of light passing through the core portion 3 and the efficiency of optical coupling between the optical waveguide and the light emitting / receiving element.

The width of the groove 10, that is, the width of the side clad 6 may be about several μm to several tens of μm, and is preferably set to be in the range of 5 μm to 10 μm. If the width of the groove 10 is about several μm to several tens of μm, it is possible to prevent the light propagating through the core 3 from propagating to the peripheral portion 5 and to form a planarizing layer on the upper cladding layer 4. The flatness of the upper surface of the upper clad layer 4 can be ensured without providing. In addition, when the width of the groove 10 is smaller than several μm, it is difficult to form the groove 10. When the width of the groove 10 is larger than several tens of μm, it is necessary to increase the film thickness of the upper cladding layer 4.

The film thickness of the upper clad layer 4 may be optimized according to the width of the groove 10 provided in the core 3. For example, when the width of the groove 10 is narrow, the film thickness of the upper clad layer 4 is reduced. Thus, even if the excess organic material in the vicinity of the groove 10 is reduced, the flatness can be improved. On the other hand, when the width of the groove 10 is wide, if the thickness of the upper clad layer 4 is slightly increased, excess organic material in the vicinity of the groove 10 is increased, so that the flatness can be improved similarly. .

The film thickness of the upper clad layer 4 is desirably set within a range of 10 μm to 30 μm in order to directly optically couple the core 3 and the light emitting / receiving element. If the film thickness of the upper clad layer 4 is within this range, as will be described later, the flatness of the upper surface of the upper clad layer 4 can be ensured when the film thickness of the core part 3 is set to 20 μm, for example.

The lower cladding layer 2, the core forming layer 7, and the upper cladding layer 4 are all formed of an organic material. Thus, by using an organic material for the optical waveguide, it is possible to increase the thickness of the optical waveguide and facilitate optical coupling between the optical waveguide and the light receiving and emitting element. That is, high alignment accuracy of the light emitting / receiving element with respect to the optical waveguide is not required.

Next, the manufacturing method of the optical waveguide concerning this Embodiment is demonstrated below based on Fig.2 (a)-(e).
2A to 2E are cross-sectional views schematically showing a method for manufacturing an optical waveguide according to the present embodiment.

  First, as shown in FIG. 2A, an organic material (a polyimide material is used in the present embodiment) for forming a cladding layer on the substrate 1, and the thickness of the lower cladding layer 2 is desired. The lower clad layer 2 (first organic material layer) is formed by applying the film by spin coating so as to have a thickness (approximately several μm to several tens μm), and drying and curing. The thickness of the organic material applied on the substrate 1 can be freely adjusted between several μm and several tens of μm by adjusting the rotation speed of the spin coat. By adjusting, the lower clad layer 2 having a desired film thickness can be obtained.

  Next, as shown in FIG. 2B, in the same manner as when the lower cladding layer 2 is formed, an organic material (this embodiment) for forming the core portion 3 and the peripheral portion 5 on the lower cladding layer 2 is formed. In this embodiment, a polyimide material having a refractive index different from that of the polyimide material for forming the lower cladding layer 2 and the upper cladding layer 4, specifically, a polyimide material for forming the lower cladding layer 2 and the upper cladding layer 4 is used. The second organic material layer 15 for forming the core portion 3 is formed by laminating a polyimide material having a low refractive index.

  Subsequently, as shown in FIG. 2C, a resist layer 11 is formed on the second organic material layer 15 by applying a resist by spin coating. Then, using a mask provided with a pattern of a portion to be removed (groove portion formation planned region) in the second organic material layer 15, the pattern is transferred to the resist layer 11 by a light source such as UV light, and then alkalinized. Development processing is performed with a developer or the like. As a result, as shown in FIG. 2C, a portion of the resist layer 11 corresponding to the upper portion of the groove portion formation scheduled region of the second organic material layer 15 is removed. Thereafter, by removing the second organic material layer 15 corresponding to the portion where the resist layer 11 has been removed by reactive ion etching (RIE) or the like, as shown in FIG. As described above, the groove portion 10 having a width of several μm to several tens of μm is provided in the organic material layer 15. Further, the resist remaining on the second organic material layer 15 is removed by ashing or the like. Thereby, as shown in FIG. 2D, the core portion 3 and the peripheral portion 5 made of the second organic material and separated from each other can be formed on the lower cladding layer 2.

  Next, as shown in FIG. 2 (e), the upper cladding layer 4 (third organic material) is formed by using the same method as in the case where the lower cladding layer 2 is formed on the core portion 3 and the peripheral portion 5. Layer). At this time, the organic material forming the upper clad layer 4 flows into the groove 10 between the core portion 3 and the peripheral portion 5, so that the upper clad layer is interposed between the core portion 3 and the peripheral portion 5. A side clad portion 6 made of an organic material forming 4 is formed.

  Finally, the lower clad layer 2, the core portion 3, the peripheral portion 5, the side clad portion 6, and the upper clad layer 4 are collectively heated in an oven or the like to be sintered. Thereby, the optical waveguide concerning this Embodiment can be formed.

  In the description shown in FIGS. 2A to 2E, the description of the case where the mirrors 9 and 9 are provided in the optical waveguide has been omitted. However, as shown in FIG. When the mirrors 9 and 9 are provided at both ends in the longitudinal direction, after forming the core portion 3, for example, a mirror surface is formed at both ends in the longitudinal direction of the core portion 3 by using a dicer or the like. The mirror reflecting surface can be formed by performing a metal plating process or the like. It is also possible to form mirrors 9 and 9 at a desired position after the formation of the upper cladding layer 4 by the same method.

Next, a result of comparison between the optical waveguide according to the present embodiment and a general optical waveguide by calculation regarding the flatness of each surface will be described with reference to FIG.

  FIG. 3 is a cross-sectional view schematically showing a schematic configuration around the core portion of the optical waveguide according to the present embodiment, in particular, a configuration of the upper cladding layer 4 around the core portion, and the components shown in FIG. The same number is attached | subjected to the component which has the same function.

  FIG. 4 is a cross-sectional view schematically showing a schematic configuration around a core portion before forming a planarization layer in a conventional general optical waveguide. In the optical waveguide shown in FIG. 4, a lower cladding layer 12 is formed on a substrate 11, a core portion 13 is formed on the lower cladding layer 12, and an upper cladding layer 14 is formed so as to cover the core portion 13. It has the structure which was made.

  In the present embodiment, as shown in FIG. 3, the dimension (film thickness) in the height direction of the core part 3 is A, and the distance between the core part 3 and the peripheral part 5, that is, the width of the side cladding part 6 is t. The film thickness of the upper clad layer 4 is h, and the film thickness variation generated in the upper clad layer 4 is Δh. By measuring the film thickness variation Δh (μm) in each film thickness h (μm), the film thickness h ( μm) and the film thickness variation Δh (μm) were obtained. Similarly, the relationship between the film thickness h (μm) and the film thickness variation Δh (μm) in the optical waveguide shown in FIG. 4 was obtained. The film thickness h of the upper clad layer 4 is the height (film thickness) of the surface position of the upper clad layer 4 with reference to the surface positions of the core portion 3 and the peripheral portion 5, that is, the surface position of the core portion forming layer 7. The thickness h of the upper cladding layer 14 indicates the height (film thickness) of the surface position of the upper cladding layer 14 with respect to the surface position of the lower cladding layer 12.

  The film thickness variation Δh indicates the difference between the height of the uppermost surface and the height of the lowermost surface on the surface of the upper cladding layer 4, in other words, the difference between the maximum value and the minimum value of the film thickness h. The film thickness variation Δh was obtained by calculating the amount of reduction when the shape of the groove 10 was taken into consideration among the organic materials in the upper part of the groove 10 and the periphery thereof.

  FIG. 5 shows the film thickness h and film thickness variation Δh of the upper cladding layers 4 and 14 in the optical waveguide shown in FIGS. 3 and 4 when A = 20 μm and t = 10 μm.

  As shown in FIG. 5, in the optical waveguide of the present invention, the film thickness variation Δh is suppressed as a whole as compared with the conventional optical waveguide.

  Further, in the conventional optical waveguide, the film thickness variation Δh is 5 μm when the film thickness h is 30 μm, but in the optical waveguide of the present invention, the film thickness variation is 5 μm when the film thickness is 10 μm. Therefore, the optical waveguide of the present invention can suppress the film thickness variation Δh with a film thickness of 1/3 as compared with the conventional optical waveguide.

  Further, in the conventional optical waveguide, when the film thickness h is larger than the film thickness A of the core portion 3 (h> A), that is, when the film thickness h is larger than 20 μm, the film thickness variation Δh is reduced. In the optical waveguide according to the present embodiment, when the film thickness h is smaller than the film thickness A of the core portion 3 (h <A), that is, when the film thickness h is smaller than 20 μm, the film thickness variation Δh is 5 μm or less. It can be seen that the film thickness variation Δh is suppressed with respect to the film thickness h.

  As described above, according to the present embodiment, the core portion forming layer 7 includes the core portion 3 and the peripheral portion 5 provided apart from the core portion 3, and the second organic material layer. Without removing the organic material layer used to form the core portion 3 except that the organic material layer around the core portion 3 is removed with a width of several μm to several tens of μm by providing the groove portion 10 in the groove portion 10. The configuration is left as the peripheral portion 5 as it is. That is, the optical waveguide according to the present embodiment is provided in the same layer as the core portion 3, made of the same organic material as the core portion 3, and separated from the core portion 3 so as to surround the side surface of the core portion 3. The peripheral portion 5 is provided.

  For this reason, the optical waveguide according to the present embodiment includes the core part 3 in the core part formation layer 7 and the peripheral part 5 adjacent to the core part 3 and the groove part 10, that is, most parts of the core part formation layer 7. Are made of the same organic material layer, so that most of the core portion forming layer 7, that is, the core portion 3 and the peripheral portion 5 have substantially the same height so as to form the same plane. By forming the upper clad layer 4 on the part forming layer 7, for example, as shown in Patent Document 1, the organic material used for forming the core part in the part (area) other than the core part in the planar area including the core part As in the case of removing all of the above, a significant step does not occur on the surface of the upper clad layer, and an optical waveguide having excellent surface flatness can be obtained. Accordingly, even when a chip component or a metal wiring is provided on the optical waveguide, it is possible to prevent the chip component from being mounted incorrectly or from being poorly formed.

  Moreover, according to the present embodiment, it is not always necessary to provide a flattening layer on the upper surface of the upper clad layer in order to flatten the surface of the optical waveguide as shown in Patent Document 1. For this reason, according to the present embodiment, the flatness of the surface of the optical waveguide can be sufficiently ensured without increasing the number of steps, and the distance from the surface of the optical waveguide to the core portion 3 is set to be the same as that of Patent Document 1. It can be made smaller than In addition, according to the optical waveguide according to the present embodiment, as shown in FIG. 5, the film thickness variation (Δh) on the surface of the upper cladding layer 4 can be suppressed, and the film thickness (h) of the upper cladding layer 4 can be reduced. Therefore, the amount of organic material used for the upper cladding layer 4 can be reduced, the cost can be reduced, and the film thickness (h) of the upper cladding layer 4 can be reduced. It is possible to shorten the baking time, that is, to shorten the process, etc. by being able to be made thinner.

  In the optical waveguide according to the present embodiment, a planarization layer can be provided on the upper cladding layer 4 in order to further improve the planarity as in the conventional case. However, when the planarization layer is formed in this way, Even so, according to the optical waveguide according to the present embodiment, since there is no significant step on the surface of the upper clad layer 4 as in the prior art, the thickness of the planarizing layer can be made thinner than before. it can.

  In addition, according to the method shown in FIGS. 2A to 2E, when the upper cladding layer 4 is formed, the organic material for forming the upper cladding layer 4 flows into the groove 10 so that the groove 10 is formed. Since the side clad part 6 can be formed, it is not necessary to newly fill the groove part 10 with an organic material, and the manufacturing process of the optical waveguide can be simplified. Further, since the groove 10 is filled with an organic material for forming the upper cladding layer 4, that is, an organic material for forming the cladding, the light beam propagating through the core portion 3 is propagated to the peripheral portion 5. This can be prevented more reliably and the refractive index difference can be adjusted more freely.

  Moreover, according to this Embodiment, as shown in the said patent document 2, in the plane area | region which has a core part, the organic material layer which forms a core part, such as reducing the refractive index of parts (area | regions) other than a core part, etc. The organic material that can be used to form the core part is not limited as in the case of forming the core part and the side clad part by partially modifying the structure, and the refractive index and refractive index difference can be reduced. Since it can be set freely, the propagation angle of the light beam propagating in the optical waveguide can be set freely.

  Furthermore, according to the present embodiment, the proportion of the organic material forming the core portion 3 in the planar region having the core portion 3 is much larger than that of the Patent Documents 1 and 2, and Concentration of internal stress can be suppressed. That is, according to the present embodiment, since the core portion 3 and the peripheral portion 5 are made of the same organic material, the influence of the organic material forming the core portion 3 is dominant in the planar region having the core portion 3. It becomes the target. For this reason, even when the thermal expansion coefficient of the organic material flowing into the groove portion 10 is larger than the thermal expansion coefficient of the organic material forming the core portion 3, the internal stress applied to the core portion forming layer 7 is the peripheral portion 5. Therefore, the internal stress does not concentrate only on the core portion 3. For this reason, since an internal stress does not concentrate on the core part 3 unlike the past, the deformation | transformation and damage of the core part 3 are prevented, and the optical waveguide without the light leakage from the core part 3 and a propagation loss is provided. Can do.

  In the present embodiment, an organic material solution is formed by spin coating as a method of forming the lower cladding layer 2, the core portion forming layer 7, and the upper cladding layer 4, that is, the first to third organic material layers. Although the method of apply | coating was used, it is not limited to this, For example, other methods, such as a printing method, can also be used. The method for applying the organic material solution may be appropriately selected according to the size, material, and configuration of the substrate 1 and is not particularly limited.

  Moreover, in this Embodiment, although the case where the polyimide material was used as an organic material which comprises each said layer was demonstrated, the organic material used for each said layer is not limited to this, The said polyimide material is used. Instead, an organic material having photosensitivity such as polysilane may be used.

  Further, when a positive organic material having photosensitivity is used for the second organic material layer 15, the portions that become the core portion 3 and the peripheral portion 5 are formed in the step of forming the core portion 3 and the peripheral portion 5. The organic material between the core part 3 and the peripheral part 5 is made soluble by performing light-shielding with a mask and performing exposure processing with UV light or the like on the mask, and can be removed by wet etching with an alkaline solution or the like. According to this method, it is not necessary to use a vacuum apparatus such as RIE, and the manufacturing process of the optical waveguide can be further simplified and the cost can be reduced.

  The upper clad layer (third organic material layer) 4 may be made of the same organic material as the lower clad layer (first organic material layer) 2, but may be made of a different organic material.

  In the above-described optical waveguide manufacturing method, after the upper cladding layer 4 is formed, the lower cladding layer 2, the core part 3, the peripheral part 5, the side cladding part 6, and the upper cladding layer 4 are collectively put in an oven or the like. The case where the sintering process is performed by heating has been described as an example, but the present invention is not limited to this, and the layer made of each organic material, that is, the lower cladding layer 2 (first organic material) Layer), the core portion 3 and the peripheral portion 5 (layer made of the second organic material), the side cladding portion 6 and the upper cladding layer 4 (layer made of the third organic material) each time a sintering process is performed. May be performed.

  Furthermore, although the case where the structure of the optical waveguide is linear has been described in the present embodiment, the present invention is not limited to this, and for example, a configuration having a bent shape may be used.

  Further, according to the present embodiment, chip parts such as resistors and capacitors are formed on the upper clad layer 4 in the optical waveguide, and electrical wiring (none of which is shown) is performed by performing metal plating. And a light emitting element and a light receiving element (light emitting and receiving elements such as a light emitting diode (LED), a semiconductor laser, and a photodiode), or an array type in which these light emitting elements and light receiving elements are integrated into an array. The optical circuit board according to the present embodiment is attached by attaching the light emitting / receiving elements using solder and optically coupling these light emitting / receiving elements to the end surface of the core portion 3 via the mirror 9 or directly. Can be obtained. Since the optical circuit board is excellent in the flatness of the surface of the optical waveguide, it is possible to prevent poor connection of chip components and metal wiring provided on the surface of the optical waveguide.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to FIGS. 6 (a) and 6 (b) and FIGS. 7 (a) and 7 (b). For convenience of explanation, components having the same functions as those in the optical waveguide according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. In the present embodiment, differences from the first embodiment will be mainly described.

  FIG. 6A is a plan view showing a schematic configuration of the optical waveguide according to the present embodiment in which two core portions are provided in a partially broken view, and FIG. 6B is a plan view of FIG. It is a BB 'arrow directional cross-sectional view of the optical waveguide shown. FIG. 7A schematically shows a schematic configuration of the optical waveguide (optical circuit board) when a light emitting element is arranged on an optical waveguide having a structure in which two core portions are adjacent to each other through one groove portion. FIG. 7B is a cross-sectional view taken along the line CC ′ showing the schematic configuration of the optical waveguide shown in FIG.

  As described in the first embodiment, the light emitting / receiving element can be configured to optically couple with the end face of the core portion 3 via the mirror 9 or directly with respect to the optical waveguide. At this time, in the case where the arrayed light receiving / emitting elements having a plurality of light receiving elements or light emitting elements and the plurality of core portions 3 are optically coupled, the light emitting elements and the light receiving elements are adjacent to each other. If the interval between the optical waveguides is narrow, there is a possibility that a problem that the light receiving elements and the light emitting elements interfere with each other may occur.

  Therefore, as shown in FIG. 7A, the width of the light emitting / receiving element 24 optically coupled to the end of the core portion 3 (the width in the short direction of the core portion 3) is B μm, and the adjacent core portions 3 are adjacent to each other. When the interval between the central axes of 3 is H μm, when the core portions 3 and 3 are provided with one groove portion 10 interposed therebetween, if B / 2 is larger than H / 2, the groove portion 10 Needs to be widened so that H / 2 ≧ B / 2.

  For example, in FIGS. 7A and 7B, when the side cladding portion 26 having a width of 10 μm is provided between the core portions 3 and 3 having a width of 20 μm, the central axes of the adjacent core portions 3 and 3 are arranged. The interval H is 30 μm.

  At this time, for example, when a light receiving / emitting element 24 having a size of 50 μm square, that is, a width B of 50 μm, is optically coupled to the core portions 3 and 3, the adjacent core portions are prevented in order to prevent interference between the adjacent light emitting / receiving elements 24. The distance H between the central axes of 3 and 3 needs to be at least 50 μm or more. For this purpose, it is necessary to further increase the distance H between the central axes of the core portions 3 and 3 by 20 μm or more, that is, to increase the width of the side cladding portion 6 from 10 μm to 30 μm. However, when the width of the side cladding 6 is increased, the flatness of the surface of the upper cladding layer 4 is greatly deteriorated as shown in FIG. 7B, and it is necessary to increase the thickness of the upper cladding layer 4. As a result, the effects of the present invention cannot be sufficiently obtained.

  Therefore, in the optical waveguide according to the present embodiment, as shown in FIGS. 6A and 6B, when a plurality of core portions 3 are provided on the same plane, that is, in the core portion forming layer 7, A configuration in which a peripheral portion 5 is provided between the adjacent core portions 3 and 3 as necessary, more specifically, a side cladding portion 6 is interposed between the two adjacent core portions 3 and 3. The peripheral portion 5 is arranged so that adjacent light receiving and emitting elements 24 and 24 that are optically coupled (mounted) to the respective end faces of the core portions 3 and 3 do not interfere with each other. be able to.

  Accordingly, in the above-described example, it is necessary to further increase the distance H between the central axes of the core portions 3 and 3 by widening the groove portion 10. According to the configuration, by providing the peripheral portion 5 having a width of 20 μm or more between the core portions 3 and 3, the interval H between the central axes of the adjacent core portions 3 and 3 is 50 μm or more without widening the groove portion 10. Can be.

  As described above, according to the present embodiment, since the peripheral portion 5 is provided between the core portions 3 and 3, light reception / emission is performed even when the interval H between the central axes of the core portions 3 and 3 is increased. An optical waveguide with excellent surface flatness can be obtained regardless of the size of the element 24 and the positional relationship between the light emitting and receiving elements 24.

  Also in the present embodiment, since the core portions 3 and 3 and the peripheral portion 5 are made of the same second organic material, internal stress is not concentrated only on the core portions 3 and 3. Therefore, the deformation and breakage of the core portions 3 and 3 can be prevented.

  In the present embodiment, the case where two core portions 3 are provided on the same plane has been described as an example. However, the number of core portions 3 is not limited to this, and the same plane is provided. It is good also as a structure by which three or more core parts 3 are provided.

  As described above, the optical waveguide according to the present invention is an optical waveguide including a core part forming layer having a core part that propagates light, and a cladding layer that covers the core part forming layer. The core portion and the core portion are made of the same organic material, and have a configuration including a peripheral portion that is provided apart from the core portion so as to surround the side surface of the core portion. The optical waveguide includes, for example, a layer made of a first organic material formed on a substrate, a layer made of a second organic material formed on the layer made of the first organic material, and the second A layer made of a third organic material formed on the layer made of an organic material, and the layer made of the second organic material has a core surrounded by a groove and made of the first organic material. The layer and the layer made of the third organic material are configured to form a clad. It may be.

  In the optical waveguide, the layer made of the second organic material has two or more cores surrounded by the groove, and the second waveguide is disposed between the adjacent cores so as to be separated from the core. You may have the structure containing the area | region which consists of these organic materials.

Furthermore, the waveguide may have a configuration in which the groove is filled with the third organic material.

An optical waveguide manufacturing method according to the present invention is a method for manufacturing an optical waveguide comprising a core part forming layer having a core part for propagating light, and a clad layer covering the core part forming layer. The organic material layer forming the core portion is formed with a groove portion so as to surround the region to be the core portion, and the core portion is made of the same organic material as the core portion, and the side surface of the core portion is surrounded by the above A method comprising a step of forming a peripheral portion provided apart from the core portion at the groove portion, and a step of forming a clad layer so as to cover the core portion and the peripheral portion. An optical waveguide manufacturing method includes a step of forming a layer made of a first organic material on a substrate, a step of forming a layer made of a second organic material on the layer made of the first organic material, By forming a groove in the layer made of the second organic material A method comprising a step of forming a waveguide, a step of forming a layer made of a third organic material on the layer made of the second organic material forming the waveguide, and a step of performing a sintering treatment by firing. There may be.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The optical waveguide of the present invention can freely set the propagation angle of light propagating in the optical waveguide, and can sufficiently ensure the flatness of the optical waveguide surface without increasing the number of steps. The concentration of internal stress on the core can be suppressed. For this reason, the said optical waveguide is suitable for the optical wiring used for an optical interconnection with a high transmission capacity, for example, and can be used for various optical communication apparatus etc. which have optical wiring, such as an optical circuit element.

(A) is a top view which shows schematic structure of the optical waveguide concerning one Embodiment of this invention by a partial fracture | rupture, (b) is an AA 'line arrow view of the optical waveguide shown to (a). It is sectional drawing. (A)-(e) is sectional drawing which shows typically the manufacturing method of the optical waveguide of this invention. It is sectional drawing which shows typically schematic structure of the core part periphery in the optical waveguide of this invention. FIG. 4 is a cross-sectional view schematically showing a schematic configuration around a core portion before a planarization layer is formed in a conventional optical waveguide. 5 is a graph showing the relationship between the film thickness of the upper clad layer and the film thickness variation in the optical waveguide shown in FIGS. 3 and 4. (A) is a top view which shows schematic structure of the optical waveguide concerning this embodiment by a partial fracture | rupture, (b) is BB 'arrow sectional drawing of the optical waveguide shown to (a). . (A) is a plan view schematically showing a schematic configuration of an optical waveguide when a light emitting element is arranged on an optical waveguide having a structure in which two core portions are adjacent to each other through one groove portion; FIG. 7B is a cross-sectional view taken along the line CC ′ of the optical waveguide shown in FIG. (A) is sectional drawing which shows schematic structure of the principal part of the conventional optical waveguide, (b) is a top view which shows schematic structure of the principal part of the optical waveguide shown to (a). (A)-(e) is sectional drawing which shows the manufacturing process of the conventional optical waveguide.

Explanation of symbols

1 Substrate 2 Lower cladding layer (first organic material layer)
3 Core part (second organic material layer)
4 Upper cladding layer (third organic material layer, cladding layer)
5 Peripheral part (second organic material layer)
6 Side cladding part 9 Mirror 10 Groove part 11 Resist layer 13 Light-shielding part 15 2nd organic material layer (2nd organic material layer)
24 Light emitting / receiving element

Claims (5)

In an optical waveguide comprising a core part forming layer having a core part that propagates light, and a cladding layer covering the core part forming layer,
The core portion forming layer includes a core portion and a peripheral portion made of the same organic material as the core portion and provided apart from the core portion so as to surround a side surface of the core portion. Optical waveguide.   The core part forming layer includes a plurality of the core parts, and includes a peripheral part that is made of the same organic material as the core part and is spaced apart from the core part between adjacent core parts. The optical waveguide according to claim 1.   The optical waveguide according to claim 1 or 2, wherein the same organic material as an organic material forming a cladding layer covering the core portion forming layer is filled between the core portion and the peripheral portion.   An optical circuit board comprising the optical waveguide according to claim 1. A method of manufacturing an optical waveguide comprising a core part forming layer having a core part for propagating light, and a cladding layer covering the core part forming layer,
By forming a groove portion in the organic material layer forming the core portion so as to surround a region to be the core portion, the core portion is made of the same organic material as the core portion, and surrounds the side surface of the core portion. Forming a peripheral portion provided apart from the core portion in the groove portion;
And a step of forming a clad layer so as to cover the core portion and the peripheral portion.

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