JP5654847B2 - Optical module - Google Patents

Description

  The present invention relates to an optical module that transmits or receives an optical signal.

  An optical module 50 shown in FIG. 10 includes an internal waveguide 52 provided in a groove formed on the surface of each first substrate 51 of the light emitting (transmitting) side optical module 50A and the light receiving (receiving) side optical module 50B. An optical path changing mirror 53 formed at the tip of the groove is provided. Further, it is mounted on the surface of each first substrate 51 and emits an optical signal to the core portion of the internal waveguide 52 via the mirror portion 53, or light from the core portion of the internal waveguide 52 via the mirror portion 53. A light emitting element (optical element) 54A and a light receiving element (optical element) 54B for receiving signals are provided. Further, an external waveguide (optical fiber) 55 optically coupled to the core portion of each internal waveguide 52 of the light emitting element 54A and the light receiving element 54B is provided (see Patent Document 1). In Patent Document 1, a flexible film-like one in which a resin optical waveguide is thinned is used as an external waveguide.

  In this patent document 1, the surface of each first substrate 51 is flip-chip mounted with bumps using the light emitting surface of the light emitting element 54A and the light receiving surface of the light receiving element 54B as mounting surfaces.

  Each first substrate 51 is installed on the surface of another second substrate (interposer substrate) 56. On the surface of each second substrate 56, an IC substrate 57A on which an IC circuit for transmitting an electric signal to the light emitting element 54A is formed and an IC circuit for receiving an electric signal from the light receiving element 54B are formed. Each IC substrate 57B is mounted. Reference numeral 59 denotes a connector for electrically connecting the IC boards 57A and 57B to other circuit devices.

  As shown in detail in FIG. 11, the signal wiring 60s and the ground wirings 60g and 60g of the light emitting element 54A and the light receiving element 54B of each first substrate 51 are formed of metal wiring (patterning circuit by copper or gold sputtering). . Further, each signal wiring 60s and ground wiring 60g, 60g, which are metal wirings, are electrically connected to IC substrates 57A, 57B of each second substrate 6 by wire bonding 58, respectively.

  A wiring board in which a signal line and a shield line are provided via an insulating film has been proposed (see Patent Document 2).

JP 2009-260227 A JP 2003-273115 A

  By the way, in the optical module as in Patent Document 1, impedance matching between the light emitting element 54A (light receiving element 54B) and the metal wirings 60s and 60g formed on the surface (upper surface) of the first substrate 51 cannot be achieved. The transmission characteristics of the are degraded. Here, when the dielectric constant and thickness of the first substrate 51 are constant, the impedance can be controlled by changing the width and interval of the signal wiring and the ground wiring.

  However, when a silicon substrate (silicon bench) is used as the first substrate 51, the wiring width is limited by the distance between the wire bonding 58 and the distance between the metal pads of the light emitting element 54A and the light receiving element 54B. Therefore, there is a problem that it is difficult to set the wiring width / interval so as to obtain an optimum impedance.

  The present invention has been made to solve the above problems, and an object thereof is to provide an optical module capable of optimally controlling impedance by adjusting the distance between a signal metal wiring and a ground plane. Is.

In order to solve the above-described problems, the present invention provides an optical path groove formed on the surface of a silicon substrate, an optical path conversion mirror formed at the tip of the optical path groove, and an optical path groove An external waveguide located near the edge and mounted on the surface of the silicon substrate so as to face the mirror, and emits an optical signal to the external waveguide via the mirror, or externally via the mirror An optical module including an optical element that receives an optical signal from a waveguide, wherein the signal wiring of the optical element is formed of a metal wiring, a downward recess formed on the surface of the silicon substrate, and an inner surface of the downward recess And a ground surface formed across the surface of the substrate, a resin portion filled in the downward concave portion so as to cover the ground surface in the downward concave portion, and positioned substantially directly above the ground surface , The resin The result in the signal wiring formed on the surface of, by changing the depth of the downwardly concave portion, there is provided an optical module, characterized in that adjusting the distance between the signal line and the ground plane.

  The silicon substrate may be grounded, and the ground surface of the downward recess may be grounded via the silicon substrate.

  Each of the recesses may be formed by etching.

According to the present invention, since the ground plane is arranged at a predetermined distance from the signal wiring of the optical element, the impedance can be optimally controlled by adjusting the distance between the signal wiring and the ground plane.
In addition, a ground surface is formed on the inner surface of the downward concave portion of the silicon substrate, and a signal wiring of the optical element is formed on the surface of the resin portion filled in the downward concave portion so as to cover the ground surface. Therefore, the impedance can be optimally controlled by changing the depth of the downward recess and adjusting the distance between the signal wiring and the ground plane. Further, since it is possible to form a downward recess simultaneously with the optical path groove in the silicon substrate by an etching process, the impedance can be controlled with a minimum number of processes.

1 is a schematic side view of an optical module according to the present invention. It is the 1st board | substrate of the optical module of the light emission side of FIG. 1, (a) is side surface sectional drawing, (b) is II sectional view taken on the line of (a), (c) is II-II line of (a). It is sectional drawing. 2A is a perspective view of the first substrate of FIG. 2, and FIG. 3B is a perspective view in which an internal waveguide is formed. FIG. 3A is a perspective view in which a light emitting element is mounted, and FIG. 3B is a perspective view in which an optical fiber is inserted. (A) is the perspective view which fixed the pressing block to the 1st board | substrate, (b) is the perspective view of an optical fiber. It is the light emission side optical module of 1st Embodiment, (a) is a top view, (b) is the III-III sectional view taken on the line of (a). It is the light emission side optical module of 2nd Embodiment, (a) is a top view, (b) is the IV-IV sectional view taken on the line of (a). It is the conventional optical module of 3rd Embodiment, (a) is a top view, (b) is the VV sectional view taken on the line of (a). It is the light emission side optical module of 4th Embodiment, (a) is a top view, (b) is the VI-VI sectional view taken on the line of (a). It is side surface sectional drawing of the conventional optical module. It is the conventional light emission side optical module, (a) is a top view, (b) is a front view of (a).

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic side view of an optical module according to the present invention. 2 is a first substrate 1 of the light-emitting side optical module of FIG. 1, (a) is a side sectional view, (b) is a sectional view taken along line II of (a), and (c) is a sectional view of (a). It is II-II sectional view taken on the line. 3A and 3B show the first substrate 1. FIG. 3A is a perspective view, and FIG. 3B is a perspective view in which an internal waveguide 16 is formed. 4A and 4B show the first substrate 1, in which FIG. 4A is a perspective view in which the light emitting element 12a is mounted, and FIG. 4B is a perspective view in which the optical fiber 2 is inserted. FIG. 5A is a perspective view in which the holding block 24 is fixed, and FIG. 5B is a perspective view of the optical fiber 2.

  In FIG. 1, the optical module includes a light emitting side optical module 40A, a light receiving side optical module 40B, and an optical fiber 2 that optically couples the light emitting side and light receiving side optical modules 40A, 40B.

  The first substrate 1 needs to be rigid in order to avoid the influence of heat during mounting and the influence of stress due to the use environment. Further, in the case of optical transmission, since optical coupling efficiency from the light emitting element to the light receiving element is required, it is necessary to mount the optical element with high accuracy and to suppress position fluctuation during use as much as possible. For this reason, a silicon (Si) substrate is employed as the first substrate 1 in the present embodiment.

  In particular, in the case of a silicon substrate, it is possible to process a highly accurate etching groove on the surface by utilizing the crystal orientation of silicon [a highly accurate mirror portion 15 (described later) using this groove, and an internal waveguide 16 ( (To be described later). ]. In addition, the silicon substrate has good flatness.

  The first substrate 1 is installed on the surface (upper surface) of a second substrate (interposer substrate) 6 having a larger size. Connectors 7 for electrically connecting to other circuit devices are respectively attached to the back surface (lower surface) of each second substrate 6.

  On the surface (upper surface) of the first substrate 1, a light emitting element 12a that converts an electrical signal into an optical signal is flip-chip mounted with bumps 12c (see FIG. 2) with the light emitting surface facing downward. An IC substrate (signal processing unit) 4a on which an IC circuit for transmitting an electrical signal to the light emitting element 12a is formed is mounted on the surface of the second substrate 6.

  In the present embodiment, a surface emitting laser (VCSEL (Vertical Cavity Surface Emitting Laser)) that is a semiconductor laser is employed as the light emitting element 12a. The light emitting element 12a may be an LED or the like.

  The IC substrate 4a is a driver IC that drives the VCSEL, and is disposed in the vicinity of the light emitting element 12a. As will be described later, as in the case of FIG. 11 (see the reference numerals in parentheses), the signal wiring (60s) and the ground wiring (60g, 60g) of the light emitting element 12a (54A) of the first substrate 1 (51). 60g) is formed of metal wiring (patterning circuit by copper or gold sputtering). The signal wiring (60s) and the ground wiring (60g, 60g), which are metal wiring, are electrically connected to the IC substrate 4a (57A) of the second substrate 6 (56) by wire bonding (58).

  On the surface of the first substrate 1, as shown in FIG. 3 (a), a substantially trapezoidal first groove (waveguide forming groove) 1a and a substantially V-shaped second deeper than the first groove 1a. The groove 1b is formed continuously in the front-rear direction. The first groove 1a may be a substantially V-shaped groove that is shallower than the second groove 1b.

  At the tip of the first groove 1a, an optical path changing mirror 15 for bending the optical path by 90 degrees is formed at a position directly below the light emitting element 12a.

  As shown in FIG. 3B, an internal waveguide 16 that is optically coupled to the light emitting element 12a of the first substrate 1 is provided in the first groove 1a of the first substrate 1. The internal waveguide 16 extends from the mirror portion 15 in the direction of the second groove 1b and is flush with the rear end portion 1d of the first groove 1a.

  The internal waveguide 16 includes a core portion 17 having a substantially square cross section with a high refractive index through which light propagates, and a cladding portion 18 having a refractive index lower than that. As shown in FIG. 2C, the left and right surfaces of the core portion 17 are covered with the cladding portion 18. When the first groove 1a is a shallow V-shaped groove that is shallower than the second groove 1b, the core portion 17 is not substantially square in cross section, but is substantially pentagonal in cross section along the substantially V-shaped groove. Form into shape. Further, the internal waveguide 16 is not necessarily provided in the first groove 1a. In this case, the first groove 1a is an optical path groove.

  As shown in FIG. 4A, a light emitting element 12a is mounted at a predetermined position on the surface of the first substrate 1 on which the internal waveguide 16 is provided, and the space between the light emitting element 12a and the core portion 17 is mounted. As shown in FIG. 2A, the optical transparent resin 13 is filled.

  Returning to FIG. 1, the light-receiving side optical module 40B will be described. The basic configuration of the first substrate 1 of the light receiving side optical module 40B is the same as that of the first substrate 1 of the light emitting side optical module 40A. However, a light receiving element 12b for converting an optical signal into an electric signal is flip-chip mounted with bumps on the surface (upper surface) of the first substrate 1 of the light receiving side optical module 40B with the light receiving surface facing downward. In addition, an IC substrate (signal processing unit) 4b on which an IC circuit for transmitting an electric signal to the light receiving element 12b is mounted on the surface of the second substrate 6, and the light emitting side optical module 40A is mounted. Different from the first substrate 1. As this light receiving element 12b, PD (Photo Diode) is adopted, and the IC substrate 4b is an element such as a TIA (Trans-impedance Amplifier) that performs current / voltage conversion.

  Next, the optical fiber 2 will be described. As shown in FIGS. 1 and 5, the optical fiber 2 has a fiber core portion 21 that can optically couple the core portion 17 of the light-emitting side optical module 40A and the core portion 17 of the light-receiving side optical module 40B. doing. And it is a cord type comprised by the fiber cladding part 22 surrounding the outer periphery of this fiber core part 21, and the coating | coated part 23 which coat | covers the outer periphery of this fiber cladding part 22. FIG. The fiber core portion 21, the fiber clad portion 22, and the covering portion 23 are circular.

  As shown in FIG. 1, the optical fiber 2 has the covering portion 23 peeled off in the vicinity of the second groove 1 b of the first substrate 1 to expose the fiber cladding portion 22.

  Then, as shown in FIGS. 2A, 2C, and 4B, the fiber clad portion 22 of the optical fiber 2 is installed in the second groove 1b of the first substrate 1, and the boundary portion with the first groove 1a. The fiber clad portion 22 is positioned at the rising slope portion. At this time, it is optically coupled with the optical axis of the core part 17 of the internal waveguide 16 of the first substrate 1 and the fiber core part 21 of the optical fiber 2 being aligned.

  The gap between the end face of the core portion 17 of the internal waveguide 16 of the first substrate 1 and the end face of the fiber core portion 21 of the optical fiber 2 is 200 μm or less. In general, the gap 0 is preferable in which the optical coupling efficiency is 100%. However, in this configuration, the gap is 60 μm to 100 μm due to restrictions on the groove width of the first substrate 1 and the outer diameter size of the optical fiber clad portion 26. It becomes.

  At the position of the surface of the first substrate 1, as shown in FIGS. 2A and 5, a holding block 24 is disposed on the upper portion of the fiber cladding portion 22 of the optical fiber 2, and the holding block 24 and the second groove 1 b are arranged. The space between is filled with the adhesive 14.

  As described above, the front end side of the fiber clad portion 22 of the optical fiber 2 is bonded and fixed to the first substrate 1 together with the pressing block 24 with the adhesive 14 while being pressed against the second groove 1 b by the pressing block 24. become.

  6A and 6B are the light-emitting side optical module 40A-1 (the same applies to the light-receiving side optical module 40B) according to the first embodiment. FIG. 6A is a plan view, and FIG. It is.

  On the surface of the first substrate 1, a downward trapezoidal recess 1 e is formed from the light emitting element 12 a to the end 1 f of the first substrate 1. A ground surface (corresponding to the ground wiring) 30 g is formed across the inner surface of the downward recess 1 e and the surface of the first substrate 1.

  Further, a resin portion 31 filled with an insulating resin is formed in the downward recess 1e so as to cover the ground surface 30g in the downward recess 1e. The signal wiring 30s, which is a metal wiring of the light emitting element 12a, is formed on the surface of the resin portion 31 so as to be located substantially directly above the ground surface 30g located at the bottom of the downward-facing recess 1e. Thus, the ground plane 30g is arranged on the signal wiring 30s so as to be separated by a predetermined distance L.

  In the light emitting side optical module 40A-1 of the first embodiment, the ground surface 30g is formed on the inner surface of the downward recess 1e of the first substrate (silicon substrate) 1. Further, the signal wiring 30s of the light emitting element 12a is formed on the surface of the resin portion 31 filled in the downward concave portion 1e so as to cover the ground surface 30g.

  Therefore, the impedance can be optimally controlled by adjusting the distance L between the signal wiring 30s and the ground surface 30g by changing the depth of the downward recess 1e. Further, since the downward recess 1e can be formed simultaneously with the first groove (optical path groove) 1a in the first substrate (silicon substrate) 1 in the etching process, the impedance can be controlled with a minimum number of processes. Can do.

  As shown in FIG. 6B, the first substrate (silicon substrate) 1 can be grounded, and the ground surface 30 g of the downward recess 1 e can be grounded via the first substrate 1. According to this, since an inexpensive low-resistance substrate can be used for the silicon substrate, the cost can be reduced.

  7A and 7B show the light-emitting side optical module 40A-2 according to the second embodiment, where FIG. 7A is a plan view and FIG. 7B is a sectional view taken along line IV-IV in FIG.

  On the back surface of the first substrate 1, an upward trapezoidal concave portion 1 g is formed from the light emitting element 12 a to the end 1 f of the first substrate 1. A ground surface (corresponding to the ground wiring) 30g is formed on the bottom inner surface of the upward recess 1g.

  The signal wiring 30s, which is a metal wiring of the light emitting element 12a, is formed on the surface of the first substrate 1 so as to be positioned almost directly above the ground surface 30g positioned at the bottom of the upward recess 1g. Thus, the ground plane 30g is arranged on the signal wiring 30s so as to be separated by a predetermined distance L.

  In the light emitting side optical module 40A-2 of the second embodiment, the ground surface 30g is formed on the bottom inner surface of the upward recess 1g of the first substrate 1, and the signal wiring 30s of the light emitting element 12a is formed on the surface of the first substrate 1 plate. Form. Accordingly, the impedance can be optimally controlled by adjusting the distance L between the signal wiring 30s and the ground surface 30g by changing the depth of the upward concave portion 1g.

  In the first and second embodiments, if the recesses 1e and 1g are formed by etching, the depths of the recesses 1e and 1g can be easily adjusted by etching. Therefore, the distance L between the signal wiring 30s and the ground surface 30g is set to be small. It can be adjusted with high accuracy.

  8A and 8B show the light-emitting side optical module 40A-3 according to the third embodiment, in which FIG. 8A is a plan view and FIG. 8B is a cross-sectional view taken along line VV in FIG.

  A signal wiring 30 s is formed on the surface of the first substrate 1. An insulator 32 is disposed on the surface of the signal wiring 30s. A ground surface 30g is formed on the entire surface of the insulator 32 so as to be located almost immediately above the signal wiring 30s.

  In the light emitting side optical module 40A-3 of the third embodiment, the signal wiring 30s is formed on the surface of the first substrate 1, and the ground surface 30g is formed on the surface of the insulator 32 disposed on the surface of the signal wiring 30s. . Accordingly, the impedance can be optimally controlled by changing the thickness L of the insulator 32 and adjusting the distance L between the signal wiring 30s and the ground plane 30g.

  Further, when the external waveguide is the optical fiber 2, if the glass substrate or the resin substrate used as the holding plate 24 for holding the optical fiber 2 is extended, it can be used (shared) as the insulator 32, so that the cost can be reduced. It will be able to plan.

  9A and 9B show the light-emitting side optical module 40A-4 according to the fourth embodiment. FIG. 9A is a plan view, and FIG. 9B is a sectional view taken along line IV-IV in FIG.

  A signal wiring 30 s is formed on the surface of the first substrate 1. In addition, a shield cover 34 that is connected to the ground and positioned via the insulating layer 33 is disposed almost directly above the signal wiring 30s. The shield cover 34 is formed in a substantially inverted U shape and extends from the light emitting element 12a portion to the end portion 1f of the first substrate 1. The both side portions 34b are fitted into the both side end portions 1h of the first substrate 1, and the upper end portion 34b is positioned substantially directly above the signal wiring 30s as the ground surface 30g.

  In the light emitting side optical module 40A-4 of the fourth embodiment, the signal wiring 30s is formed on the surface of the first substrate 1, and the upper end portion 34a of the shield cover 34 grounded to the ground is used as the ground surface 30g. It is positioned via the insulating layer 33 substantially above. Therefore, by changing the thickness of the insulating layer 33 (in other words, changing the height of the shield cover 34), the distance L between the signal wiring 30s and the upper end portion 34a of the shield cover 34 that is the ground surface 30g is adjusted. Thus, the impedance can be optimally controlled. Further, since the shield cover 34 and the impedance control ground plane 30g can be used together, the cost can be reduced.

  Further, since the insulating layer 33 is an air layer, the distance L can be easily adjusted without using an insulating member.

  As described above, the optical module according to the present invention includes the optical path groove formed on the surface of the silicon substrate, the optical path conversion mirror formed at the tip of the optical path groove, and the optical path groove. Mounted on the surface of the silicon substrate so as to face the mirror part and the core part of the external waveguide located near the rear end part, and emits an optical signal to the core part via the mirror part, or And an optical module that receives an optical signal from the core portion, the signal wiring of the optical element is composed of a metal wiring, and the ground plane is arranged at a predetermined distance from the signal wiring. It is characterized by that.

  According to this, since the ground plane is arranged at a predetermined distance from the signal wiring of the optical element, the impedance can be optimally controlled by adjusting the distance between the signal wiring and the ground plane.

  A downward recess formed on the surface of the silicon substrate; a ground surface formed on an inner surface of the downward recess; a resin portion filled in the downward recess so as to cover the ground surface; and It can be set as the structure which consists of the said signal wiring formed in the surface of the said resin part located substantially right above.

  According to this, the ground surface is formed on the inner surface of the downward recess of the silicon substrate, and the signal wiring of the optical element is formed on the surface of the resin portion filled in the downward recess so as to cover the ground surface. Therefore, the impedance can be optimally controlled by changing the depth of the downward recess and adjusting the distance between the signal wiring and the ground plane. Further, since it is possible to form a downward recess simultaneously with the optical path groove in the silicon substrate by an etching process, the impedance can be controlled with a minimum number of processes.

  The silicon substrate may be grounded, and the ground surface of the downward recess may be grounded via the silicon substrate.

  According to this, since an inexpensive low-resistance substrate can be used for the silicon substrate, the cost can be reduced.

  Further, the upward concave portion formed on the back surface of the silicon substrate, the ground surface formed on the inner surface of the upward concave portion, and the surface formed on the surface of the silicon substrate, located substantially directly above the ground surface. The signal wiring can be configured.

  According to this, the ground surface is formed on the inner surface of the upward concave portion of the silicon substrate, and the signal wiring of the optical element is formed on the surface of the silicon substrate. Therefore, the impedance can be optimally controlled by changing the depth of the upward concave portion and adjusting the distance between the signal wiring and the ground plane.

  Moreover, each said recessed part can be set as the structure currently formed by the etching.

  According to this, since the depth of each concave portion can be easily adjusted by etching, the distance between the signal wiring and the ground plane can be adjusted with high accuracy.

  In addition, the signal wiring formed on the surface of the silicon substrate, the insulator disposed on the surface of the signal wiring, and formed on the surface of the insulator, located almost directly above the signal wiring. It can be configured by a ground plane.

  According to this, the signal wiring is formed on the surface of the silicon substrate, and the ground surface is formed on the surface of the insulator disposed on the surface of the signal wiring. Therefore, the impedance can be optimally controlled by changing the thickness of the insulator and adjusting the distance between the signal wiring and the ground plane.

  The insulator may be a glass substrate or a resin substrate.

  According to this, when the external waveguide is an optical fiber, a glass substrate or a resin substrate used as a pressing plate for pressing the optical fiber can be used, so that the cost can be reduced.

  Further, the signal wiring formed on the surface of the silicon substrate and a shield cover that is grounded to the ground and is positioned directly above the signal wiring through an insulating layer may be used.

  According to this, the signal wiring is formed on the surface of the silicon substrate, and the shield cover grounded to the ground is positioned substantially directly above the signal wiring through the insulating layer. Therefore, the impedance can be optimally controlled by changing the thickness of the insulating layer and adjusting the distance between the signal wiring and the shield cover which is the ground plane. In addition, since the shield cover and the ground plane for impedance control can be used together, the cost can be reduced.

  The insulating layer may be an air layer.

  According to this, if the insulating layer is an air layer, the distance can be easily adjusted without using an insulating member.

1 First substrate (silicon substrate)
1a 1st groove (groove for optical path)
1e Downward concave part 1g Upward concave part 2 Optical fiber 12a Light emitting element (optical element)
15 Mirror part 16 Internal waveguide 21 Fiber core part 24 Holding block (glass substrate or resin substrate)
30a Signal wiring (metal wiring)
30g Ground plane (Ground wiring)
31 Resin part 32 Insulator (glass substrate or resin substrate)
33 Insulating layer 34 Shield cover L Distance

Claims (3)

An optical path groove formed on the surface of the silicon substrate, an optical path conversion mirror formed at the tip of the optical path groove, an external waveguide located near the rear end of the optical path groove, and An optical element mounted on the surface of the silicon substrate so as to face the mirror part, and emitting an optical signal to the external waveguide via the mirror part or receiving an optical signal from the external waveguide via the mirror part; In an optical module with
The signal wiring of the optical element is composed of metal wiring,
A downward recess formed on the surface of the silicon substrate, a ground surface formed across the inner surface of the downward recess and the surface of the substrate, and the downward recess so as to cover the ground surface in the downward recess The filled resin part and the signal wiring formed on the surface of the resin part, located substantially directly above the ground surface,
An optical module , wherein the distance between the signal wiring and the ground plane is adjusted by changing the depth of the downward recess . The optical module according to claim 1 , wherein the silicon substrate is grounded, and a ground surface of the downward recess is grounded via the silicon substrate . The optical module according to claim 1 or 2, wherein the recess is formed by etching.

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