JP5898732B2 - Manufacturing method of optical module - Google Patents

Description

  The present invention relates to a method of manufacturing an optical module that serves as a transmission / reception unit for transmitting a high-speed optical signal transmitted / received between chips or between boards in a device such as a data processing apparatus.

  In recent years, with the spread of high-speed broadband services such as FTTH (Fiber To The Home) for general users, high-speed and large-capacity IT equipment represented by routers and servers has been rapidly promoted. Under such circumstances, electrical interconnects conventionally used between and within IT devices are also required to transmit at 10-25 Gbps or more per channel. However, the speed limit has become a problem due to factors such as malfunction of the device due to the generation of high-frequency noise due to high speed and the necessity of a new waveform adjusting element due to the occurrence of transmission loss of high-frequency signals. On the other hand, since light is non-inductive, noise and crosstalk between optical signal transmission lines are not generated, and reflection and loss are independent of the modulation frequency and are easy to control. Thus, by opticalizing the signal transmission line between and within the equipment, a high-frequency signal of 10 Gbps or more can be propagated with low loss, so that the number of wirings can be reduced and the above-mentioned is also applied to the high-frequency signal. It is promising because no countermeasure is required. In addition to the above routers / switches, video devices such as video cameras and consumer devices such as PCs and mobile phones will increase the speed and capacity of video signal transmission between the monitor and terminals in the future for higher definition images. In addition, since conventional electrical wiring has problems such as signal delay and noise countermeasures, it is effective to make the signal transmission line optical.

  In order to realize such a high-speed optical interconnect system and apply it between and within devices, an optical module and a circuit that are excellent in terms of performance, small size, integration, and component mountability are required with inexpensive manufacturing means. Therefore, a small and high-speed optical module has been proposed in which an optical waveguide that is cheaper and more advantageous for higher density than conventional optical fibers is used as a wiring medium, and an optical component and an optical waveguide are integrated on a substrate.

  As an example of a conventional optical module for an optical interconnect system, a configuration in which an optical module in which a light emitting element array, a light receiving element array, and an integrated circuit are integrated on an optical waveguide wiring board is mounted by solder balls is disclosed in Patent Document 1. Is disclosed. In this example, when an optical module is mounted on an optical waveguide wiring board, light is connected in the vertical direction between the light emitting element array or the light receiving element array and the optical waveguide, and at the same time, the optical module and the optical waveguide wiring are connected. Electrical connection is made between the substrates.

JP 2008-294226 A

  According to the mounting form of the optical module disclosed in Patent Document 1, a surface emitting light emitting element such as a surface emitting laser (VCSEL) or a surface incident light receiving element is mounted on the optical module. In other words, the light emitting surface or light receiving surface for exchanging optical signals and the electrode for exchanging electrical signals are formed on the same surface of the optical element. The optical distance will increase. As a result, an optical connection loss between the optical element and the optical waveguide is increased due to the beam expansion of the light in the space. In particular, in the light receiving section, the light receiving diameter of the light receiving element becomes smaller (20 μmφ or less) for future optical module speed increase (20 Gbps / ch or more), and therefore the influence of the increase in the optical connection loss due to the beam expansion of the light becomes more remarkable It becomes. Furthermore, as the transmission speed of 25 Gbps / ch and 40 Gbps / ch increases, the limitations of direct modulation methods such as light source elements and surface emitting lasers (VCSEL), and the influence of inductance (L) in wire bond mounting It is expected that the influence of the deterioration of the electric signal due to will become remarkable.

  Based on the above, in order to realize future high-capacity and power-saving signal transmission within and between boards with low loss and low cost, in recent years, integration of Si photonics technology has become possible, which enables high-speed and compact integration of optical modules. The integrated optical module is attracting attention. In the present technology, by integrating optical elements and optical components on one Si chip, the number of components and the mounting process can be greatly reduced, and a chip-scale optical module can be miniaturized. In addition, the realization problem of the chip-scale optical module using Si described above is that the light propagating in the substrate parallel direction of Si is perpendicular to connect the light between the optical element and the optical waveguide in the substrate vertical direction. And a method for producing a mirror structure that changes the optical path, and a low-loss optical coupling structure between the optical waveguide substrate and the Si optical device.

  Accordingly, an object of the present invention is to provide a method for manufacturing a small and high-speed optical module in which an optical element, an optical waveguide wiring, and an optical path conversion mirror are integrated on a single chip of Si, and in particular, the emitted light is an optical path conversion mirror. An object of the present invention is to provide a method for manufacturing an optical module structure that reduces optical loss caused by detachment from a part.

  In order to achieve the above object, the main features of the optical module manufacturing method of the present invention are as follows.

Preparing a laminated substrate in which a buried oxide film serving as a cladding layer is formed between the surface of the Si substrate and the Si thin film layer serving as the core of the Si optical waveguide; and forming an oxide film on the surface of the Si thin film layer And a step of removing the oxide film, the Si thin film layer, and the buried oxide film all together so that the surface of the Si substrate is exposed, and selectively forming a groove on the Si substrate, and the groove is higher than the upper surface of the Si thin film layer. by regrowing Si to a position, forming a Si buried layer is subjected to anisotropic etching to Si buried layer, a first facing each other, the optical path conversion unit in the groove having a second tapered surface And forming a patterned Si optical waveguide and an end face portion of the Si optical waveguide, and the light emitted to the outside from the end face portion of the Si optical waveguide at the first taper surface, Si Refracted due to the difference in refractive index, propagates inside, further reflects the propagated light on the second taper surface by the difference in refractive index between Si and the outside, and then passes the reflected light through the Si substrate. Further, the optical path conversion unit is configured to emit light to the outside of the Si substrate .

  According to the present invention, a method for manufacturing a small and high-speed optical module in which an optical element, an optical waveguide wiring, and an optical path conversion mirror unit are integrated on one chip of Si, in particular, emitted light is emitted from the optical path conversion mirror unit. It is possible to provide a method of manufacturing an optical module structure that reduces optical loss caused by detachment.

It is the whole optical module which is the 1st example of the present invention, and an expanded sectional view of an optical path changing part. 1 is a top perspective view of an optical module according to a first embodiment of the present invention. It is SOI substrate sectional drawing of an example of the optical path change part manufacturing method of the optical module which is the 2nd Example of this invention. It is the figure which provided the groove part in the oxide film and Si layer of an example of the optical path change part manufacturing method of the optical module which is the 2nd Example of this invention. It is the figure which provided the Si regrowth layer in the groove part of an example of the optical path changing part manufacturing method of the optical module which is the 2nd example of the present invention. It is the figure which provided the optical path conversion structure which has a taper surface by etching in Si regrown layer of an example of the optical path conversion part manufacturing method of the optical module which is the 2nd Example of this invention. It is the figure which provided the light-projection end surface part of Si thin film layer by perpendicular etching of Si regrowth layer of an example of an optical path changing part manufacturing method of an optical module which is the 2nd example of the present invention. It is the figure which exposed Si waveguide to the surface by the oxide film removal of a resurface layer of an example of the optical path change part manufacturing method of the optical module which is a 2nd Example of this invention. It is the whole optical module which is the 3rd example of the present invention, and an expanded sectional view of an optical path changing part. It is the whole optical module which is the 4th example of the present invention, and an expanded sectional view of an optical path changing part. It is a top perspective view of the optical module which is the 5th Example of this invention. It is a top perspective view of the optical module which is the 6th Example of this invention. It is the whole optical module which is the 7th example of the present invention, and an expanded sectional view of an optical path changing part. It is sectional drawing of the opto-electric hybrid board by which the optical module which is the 8th Example of this invention was mounted. It is a top perspective view of the optical module which is the 9th Example of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  1A and 1B are diagrams showing an outline of an optical module according to a first embodiment of the present invention. As shown in FIG. 1A as a whole and an enlarged cross-sectional view of the optical path conversion unit, in this embodiment, the laser light source element 101 is placed on the same substrate 100 made of Si material, and The Si waveguide 102 is provided directly in the horizontal direction of the substrate. Further, on the optical axis extension line from the light emitting end of the Si waveguide 102, the first taper surface 106 having an inclination angle with respect to the substrate parallel and the substrate parallel to the position facing the first taper surface 106 are provided. The optical path changing unit 104 is provided with the second tapered surface 107 having an inclination angle with respect to the surface. In addition, the optical path conversion unit 104 that is sandwiched between the first taper surface 106 and the second taper surface 107 and is formed of a Si substrate may be referred to as a main body portion for convenience below.

  According to this structure, the light emitted from the laser light source element 101, propagated in the Si waveguide 102, and then emitted to the outside of the Si once passes through the first tapered surface of the optical path conversion unit 104 to the outside (for example, air). After being refracted by the difference in refractive index from Si, it propagates inside the Si optical path conversion. Further, the propagating light inside the Si optical path conversion is vertically below the substrate due to the difference in refractive index between Si (refractive index about 3.5) and the outside (for example, air, refractive index 1.0) at the second tapered surface 107. Then, the light passes through the Si substrate 100 and is emitted to the outside of the substrate.

  As described above, this structure integrates the laser light source element 101, the Si waveguide 102 integrated on the Si substrate 100, and the optical path conversion unit 104 into one Si chip, thereby allowing the optical component to be integrated into the Si wafer. It is possible to realize the optical module 108 that can be manufactured in a batch by the process, is inexpensive and downsized on a chip scale, and enables high-density and large-capacity signal transmission.

  Note that the Si substrate 100 may be a substrate having a Si-on-Insulator (SOI) structure in which an oxide film 103 is embedded between surface Si layers. By using the SOI substrate, the buried oxide film 103 can be configured as a low-refractive index cladding layer. Therefore, as shown in FIG. 1B, by forming a wiring pattern on the Si plane, the buried oxide film 103 can be easily formed by the Si wafer process. The Si layer can be used as the optical waveguide 102.

  Further, the first taper surface 106 and the second taper surface 107 of the optical path conversion unit 104 may have a structure in which the Si (111) orientation surface is exposed on the surface. The Si (111) plane can be obtained by dicing with a desired tilt angle, irradiating with laser light, or by a processing method using chemicals such as etching. In the case of etching, it can be easily produced by a commonly used Si wafer process such as alkaline wet etching. At the same time, since the inclination angle of the azimuth plane with respect to the parallel plane of the substrate is determined to be about 54.7 degrees, there is no manufacturing variation, and the tapered surface can be manufactured with high accuracy. Of course, the necessity of 54.7 degrees does not matter, but the first tapered surface 106 and the second tapered surface 107 are parallel to the substrate in order to change the optical path of the light emitted from the Si optical waveguide 102 in the direction perpendicular to the substrate. It is desirable that the angle is approximately 50 to 60 degrees with respect to the surface.

  Further, the laser light source element 101 placed on the Si semiconductor substrate 100 is a laser element manufactured on a substrate using a compound semiconductor material such as indium phosphide (InP), and the oscillation wavelength thereof is the light of Si. In order to avoid the problem of absorption, an infrared wavelength band of 980 nm or more is preferable.

  2A to 2F are diagrams illustrating an example of a method for manufacturing an optical path conversion unit of the optical module according to the second embodiment of the present invention.

  As shown in FIG. 2B, an oxide film 200 is formed on the surface of the SOI substrate in which the buried oxide film 103 is inserted between the Si substrate 100 and the Si thin film layer 202 as shown in FIG. A groove 203 is formed in the film 200, the Si thin film layer 202, and the buried oxide film 103 by etching or the like.

Next, as shown in FIG. 2C, a structure is formed in which Si is buried in the groove 203 by regrowth or the like.
The thickness of the Si buried layer 201 may be approximately the same as the height of the outermost surface oxide film 200 portion, but it is desirable that the Si buried layer 201 is buried to a position higher than the height of the Si thin film layer 202 portion.

  Next, as shown in FIG. 2D, an etching mask pattern is formed at an arbitrary position on the Si buried layer 201 by photolithography or the like, and then anisotropic wet etching is performed using an alkaline etching solution or the like. Tapered surfaces 106 and 107 with the (111) surface exposed on the surface are formed. As described in the first embodiment, the Si (111) taper surface produced by this method has an inclination angle of about 54.7 degrees with respect to the substrate parallel plane. Although not shown here, an Si mask pattern is formed by forming an etching mask pattern on the surfaces of the Si thin film layer 202 and the surface oxide film 200 by photolithography or the like and then forming a wiring pattern by etching. it can.

  Next, as shown in FIG. 2D, the Si buried layer 201 at the end of the Si thin film layer 202 is processed in the direction perpendicular to the substrate by etching or the like, thereby providing an end surface portion of the Si waveguide 102 and two tapered surfaces 106. , 107 are formed. The surface oxide film 200 on the Si waveguide 102 may be left as shown in FIG. 2E, or the surface oxide film 200 may be removed as shown in FIG. 2F. The performance is not expected to be significantly affected.

  Through the process steps as described in the present embodiment, the Si waveguide 102 and the optical path conversion unit 104 can be collectively manufactured on the Si substrate 100 by the Si wafer process, and an inexpensive and miniaturized optical module can be realized. Is possible.

  FIG. 3 is an enlarged cross-sectional view of the entire optical module and the optical path conversion unit according to the third embodiment of the present invention. In the present embodiment, the uppermost portions 104A of the first and second tapered surfaces 106 and 107 of the optical path conversion unit 104 are positioned higher than the light emission end of the Si waveguide 102, and the optical path conversion unit The lowermost portion 104B of the first and second tapered surfaces 106 and 107 of the 104 is provided so as to be positioned at a position lower than the light emitting end portion of the Si waveguide 102. With this structure, even when light propagating in the Si waveguide 102 spreads due to a difference in refractive index when emitted to the outside of Si, the light is efficiently applied to the first tapered surface 106 of the optical path conversion unit 104. Therefore, it is possible to suppress excess light loss when the emitted light is emitted outside the tapered surface 106 of the optical path conversion unit 104.

  FIG. 4 is an enlarged cross-sectional view of the entire optical module and the optical path conversion unit according to the fourth embodiment of the present invention. In this embodiment, the medium having a refractive index larger than air (1.0) and smaller than Si (about 3.5) in the optical path between the light exit end of the Si waveguide 102 and the optical path conversion unit 104. 400 is inserted. Specifically, the medium 400 having the same intermediate refractive index has a high transmittance (about 80% or more) with respect to the wavelength of light used (980 nm or more), and a refractive index of 1.4 to 1.5. A dielectric oxide film, resin, or the like is desirable. As described in the second embodiment, when the first and second taper surfaces 106 and 107 of the optical path conversion unit 104 are formed by anisotropic etching so that the Si (111) orientation surface is exposed, the taper with respect to the substrate parallel surface is formed. The inclination angle of the surface is about 54.7 degrees. When the refractive index of Si is 3.5, the refraction angle at the first taper surface 106 and the Si internal reflection angle at the second taper surface 107 are calculated at the same inclination angle, and the refraction of the medium 400 having the same intermediate refractive index is calculated. When the ratio is 1.4 to 1.5, the light after being reflected by the second taper surface 107 is optically path-changed in the substantially vertical downward direction of the Si substrate 100. Further, the medium 400 having a refractive index of 1.4 to 1.5 is a material such as a dielectric oxide film or a resin used for a normal semiconductor device, and can be easily applied. Furthermore, the refraction angle at the first tapered surface 106 can be changed by selecting the material of the medium 400 having various refractive indexes. That is, the optical path conversion angle of the optical signal 105 can be arbitrarily adjusted by the refractive index of the medium 400.

  FIG. 5 is a top perspective view of an optical module according to a fifth embodiment of the present invention. In this embodiment, the laser light source element array 500 of 2ch or more (4ch in this example) and the Si waveguide 102 array are mounted on the Si substrate 100. Further, on the optical axis extension line from the light exit end of each waveguide of the Si waveguide 102 array, the first taper surface 106 having an inclination angle with respect to the substrate parallel is opposed to the first taper surface 106. The Si optical path conversion unit 104 is provided at the position where the second tapered surface 107 having an inclination angle with respect to the substrate parallel is exposed on the surface.

  With this configuration, it is possible to increase the capacity of the optical module without increasing the number of components and the number of mounting steps, and while keeping the chip scale downsized.

  FIG. 6 is a top perspective view of an optical module according to the sixth embodiment of the present invention. In this embodiment, compared to the structure of the fifth embodiment, Si optical path conversion units 104A to 104D are alternately arranged in a staggered manner on the plane of the Si substrate 100 for each adjacent channel of the Si waveguide 102 array. It is configured.

  Compared with the structure described in the fifth embodiment, this configuration can reduce the pitch between channels while avoiding the light crosstalk between the channels of the light emitted from the Si waveguide 102 array. The module can be further reduced in size and density. In addition, since each of the Si optical path conversion units 104A to 104D can be formed in a pattern by photolithography, etching, etc., it can be easily performed at any position on the plane of the Si substrate 100 without increasing the number of parts and the number of mounting steps. Can be formed.

  FIG. 7 is an enlarged cross-sectional view of the entire optical module and the optical path conversion unit according to the seventh embodiment of the present invention. In the present embodiment, the laser light source element 101, the Si waveguide 102 provided directly on the Si substrate 100, and the same Si substrate 100 on which the first optical path conversion unit 104A is formed are inclined with respect to the substrate parallel. A second optical path conversion unit 104B having a tapered surface 701 having a corner exposed on the surface and a light receiving element unit 700 are provided.

  In this configuration, after the light 105B incident from the outside of the Si substrate 100 in the vertical direction of the Si substrate propagates through the Si substrate 100, Si (refractive index) is formed on the tapered surface 701 of the second optical path conversion unit 104B. After being reflected by the difference in refractive index between about 3.5) and the outside (for example, air, refractive index 1.0), it is optically connected to the light receiving element portion 700 provided on the surface of the Si substrate 100.

  The tapered surface 701 of the second optical path conversion unit 104B can be easily and highly accurately manufactured using the Si wafer process method described in the second embodiment, similarly to the first optical path conversion unit 104A. In addition, the light receiving element portion 700 formed on the Si semiconductor substrate 100 uses a germanium (Ge) material that has an absorption sensitivity in the infrared wavelength band of 980 nm or more in the light receiving portion and can be manufactured by a Si wafer process. Is desirable.

  With this configuration, the laser light source element 101, the Si waveguide 102 integrated with the Si substrate 100, the optical path conversion units 104A and 104B, and the light receiving element unit 700 are integrated on a single Si chip. Components can be manufactured in a batch by the Si wafer process, and the optical module 108 having a transmission / reception function capable of transmitting signals with high density and large capacity can be realized while being reduced in size and on a chip scale.

  FIG. 8 is a cross-sectional view of an opto-electric hybrid board on which an optical module according to an eighth embodiment of the present invention is mounted. In this embodiment, as shown in FIG. 80, an optical waveguide wiring board formed from a wiring core 801 made of a material having a higher refractive index than that of the cladding layer surrounded by the cladding layer 800 on a substrate 803 such as glass epoxy. Is provided. Further, an optical path conversion mirror 802 is placed on the end of the wiring core 801.

  In this configuration, the light emitted from the laser light source element 101, propagated through the Si waveguide 102, and once emitted to the outside of the Si is refracted by the optical path conversion unit 104 and reflected downward vertically to the Si substrate 100. It passes through the inside and is emitted to the outside of the substrate. Further, the emitted light 105 is bent in the horizontal direction of the substrate by an optical path conversion mirror 802 provided in the optical waveguide wiring board, is optically connected to the wiring core 801, and propagates in the core.

Note that the wiring core 801 and the optical path conversion mirror 802 are formed using a polymer material, and can be easily and inexpensively manufactured using a method generally used for printed wiring boards such as film lamination and photolithography.
As in this configuration, an optical module in which the laser light source element 101, the Si waveguide 102 integrated on the Si substrate 100, and the optical path conversion unit 104 are each integrated on one Si chip is provided with an optical path conversion mirror structure. By mounting on a substrate provided with an optical waveguide, a high-speed and large-capacity opto-electric hybrid board in which signals exchanged between the optical element and the optical waveguide are optically connected through the Si substrate with high efficiency can be realized. .

  FIG. 9 is a top perspective view of an optical module according to the ninth embodiment of the present invention. In this embodiment, the Si optical waveguide 102 provided on the Si substrate 100 has a tapered shape 900 in the vicinity of the light emitting end, so that the optical waveguide width is changed.

  With this configuration, the diameter of the outgoing beam of the Si optical waveguide 102 can be adjusted by changing the cross-sectional area near the light emitting end of the Si optical waveguide 102. That is, with this configuration, when optically connecting a multimode optical waveguide wiring board having a large wiring core diameter of about 50 μm square as described in Example 8 and the present optical module, the Si optical waveguide 102 and the It is possible to suppress an increase in optical coupling loss due to mode mismatch, which is caused by a difference in the core diameter and numerical aperture (NA) of the mode optical waveguide wiring.

  The cross-sectional area in the vicinity of the light emitting end of the Si optical waveguide 102 may be gradually reduced, or conversely increased. In either case, the beam diameter can be changed.

100 ... Si substrate,
101 ... Laser light source element,
102 ... Si optical waveguide,
103 ... buried oxide film,
104, 104A, 104B, 104C, 104D ... Si optical path conversion unit,
105, 105A, 105B ... optical signals 106, 107, 701 ... tapered surfaces,
108: optical module,
109 ... Solder,
200: oxide film,
201 ... Si regrowth layer,
202 ... Si thin film layer,
203 ... groove,
400: Intermediate refractive index medium of Si and air,
500 ... Laser light source element array,
700... Light receiving element portion,
800 ... cladding layer,
801 ... core layer,
802 ... Optical path conversion mirror,
803 ... a substrate,
804: A thin film layer.

Claims (1)

Preparing a laminated substrate in which a buried oxide film serving as a cladding layer is formed between the surface of the Si substrate and the Si thin film layer serving as the core of the Si optical waveguide;
Forming an oxide film on the surface of the Si thin film layer;
Removing the oxide film, the Si thin film layer, and the buried oxide film all together so that the surface of the Si substrate is exposed, and selectively forming a groove on the Si substrate;
Forming a Si buried layer in the groove by re-growing Si to a position higher than the upper surface of the Si thin film layer;
The Si buried layer is subjected to anisotropic etching to form an optical path changing portion having first and second tapered surfaces facing each other in the groove, and the patterned Si optical waveguide and an end surface of the Si optical waveguide Forming a portion , and
The light emitted to the outside from the end face portion of the Si optical waveguide is refracted by the first taper surface due to the difference in refractive index between the outside and Si, propagates inside the light, and further propagates the second light. The optical path conversion unit is configured so that the reflected light is reflected by the difference in refractive index between Si and the outside, and then the reflected light passes through the Si substrate and is emitted to the outside of the Si substrate. ing
A method for manufacturing an optical module.

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