CN112987170A - Optical device and method of manufacturing the same - Google Patents

Optical device and method of manufacturing the same Download PDF

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Publication number
CN112987170A
CN112987170A CN202110200975.9A CN202110200975A CN112987170A CN 112987170 A CN112987170 A CN 112987170A CN 202110200975 A CN202110200975 A CN 202110200975A CN 112987170 A CN112987170 A CN 112987170A
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Prior art keywords
waveguide
layer
substrate
groove
optical fiber
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CN202110200975.9A
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Chinese (zh)
Inventor
冰见进
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Huawei Technologies Co Ltd
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Huawei Technologies Co Ltd
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
    • G02B6/4228—Passive alignment, i.e. without a detection of the degree of coupling or the position of the elements
    • G02B6/423—Passive alignment, i.e. without a detection of the degree of coupling or the position of the elements using guiding surfaces for the alignment
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12083—Constructional arrangements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/36—Mechanical coupling means
    • G02B6/3628—Mechanical coupling means for mounting fibres to supporting carriers
    • G02B6/3632—Mechanical coupling means for mounting fibres to supporting carriers characterised by the cross-sectional shape of the mechanical coupling means
    • G02B6/3636—Mechanical coupling means for mounting fibres to supporting carriers characterised by the cross-sectional shape of the mechanical coupling means the mechanical coupling means being grooves

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Optical Couplings Of Light Guides (AREA)
  • Optical Integrated Circuits (AREA)

Abstract

The invention relates to an optical device comprising: a substrate having a groove on a first surface; a waveguide disposed on the first surface of the substrate; an optical fiber disposed in the groove; wherein a difference between a distance of the first surface to an optical axis of the waveguide and a distance of the first surface to an optical axis of the optical fiber is about 0.5 μm or less.

Description

Optical device and method of manufacturing the same
Technical Field
The present invention described herein relates generally to optical and electrical fields, and more particularly to an optical device for aligning a waveguide and an optical fiber with high precision and a method of manufacturing the same.
Background
In the prior art, optical devices always form structures on a substrate, said structures forming waveguides and grooves, wherein optical fibers are placed in said grooves. Further, the optical fiber is aligned with the waveguide. However, in the prior art, it is difficult to obtain a structure capable of achieving accurate alignment of the optical fiber with the waveguide.
Disclosure of Invention
It is an object of the present invention to provide an optical device in which the optical coupling between a waveguide and an optical fiber is improved by precise alignment of the waveguide and the optical fiber, and a method for manufacturing the optical device.
The present invention provides an optical device comprising: a substrate having a groove on a first surface; a waveguide on the first surface of the substrate; an optical fiber located in the groove; wherein a difference between a distance of the first surface to an optical axis of the waveguide and a distance of the first surface to an optical axis of the optical fiber is about 0.5 μm or less.
The waveguide and the optical fiber have excellent optical coupling due to the precise alignment of the optical axis of the waveguide and the optical axis of the optical fiber.
The substrate may be a silicon substrate. The waveguide may include a lower cladding layer, a core layer, and an upper cladding layer. The lower cladding layer may have a thickness of about 3 μm. The upper cladding layer may have a thickness of about 6 μm. The thickness of the core layer may be about 3 μm. The lower cladding and the upper cladding may comprise SiO2. The small size of the waveguides in micron dimensions facilitates integration.
The core layer may be flat. Since the core layer is flat, the optical axis of the waveguide including the core layer and the optical axis of the optical fiber are accurately aligned.
The core layer may include a semiconductor core and an insulator core. The core layer may include a silicon layer and a SiOx layer (0< x < 2). The semiconductor core may include silicon and the insulator core may include SiOx (0< x < 2). The semiconductor core has a width of about 400nm and a thickness of about 200nm to 250nm in a plane perpendicular to the longitudinal direction of the waveguide. The semiconductor core may be completely covered by the insulator core. Since the waveguide can be fabricated by a Complementary Metal Oxide Semiconductor (CMOS) compatible process, the fabrication efficiency and cost effectiveness are high.
The groove may have a V-shaped cross-section in a plane perpendicular to the longitudinal direction of the optical fiber. The groove having the V-shaped cross section, i.e., the V-shaped groove, may have a depth of about 60 μm. The depth error of the V-shaped groove may be about 0.5 μm or less, preferably about 0.4 μm or less. The optical fiber arranged on the V-shaped groove is accurately aligned with the waveguide due to the small error of the V-shaped groove.
A portion of the waveguide may protrude above the groove along the first surface. Accordingly, the distance between the waveguide and the optical fiber can be shortened, thereby improving optical coupling therebetween.
The groove may have a U-shaped or rectangular cross-section in a plane perpendicular to the longitudinal direction of the optical fiber. Since the recess having a U-shaped or rectangular cross section can be formed by a CMOS compatible process, manufacturing efficiency and cost effectiveness are high.
Commercially available optical fibers may be used as the optical fibers disposed in the grooves. The diameter of the optical fiber may be about 125 μm. The diameter of the optical fiber is selected to provide precise alignment of the optical fiber and the waveguide.
A secondary lower cladding layer may be included in the substrate, the secondary lower cladding layer being located below the waveguide and adjacent to the groove. Due to the auxiliary lower cladding layer, reflection by the substrate is suppressed. Thus, the optical coupling between the waveguide and the optical fiber is improved.
The substrate may include a groove, and a light source may be disposed in the groove.
The depth of the trench may be about 10 μm. Commercially available light sources may be used as the light source disposed in the groove.
In addition, the present invention also provides a method of manufacturing an optical device, the method comprising: step (S1): preparing a first substrate, wherein a groove is formed on the first surface of the first substrate; step (S2): providing a waveguide layer in said first surface by bonding; step (S3): forming a waveguide by etching a portion of the waveguide layer and exposing the groove; step (S4): an optical fiber is disposed in the groove.
Since the groove may be provided on the first substrate before the waveguide layer is provided on the first surface of the first substrate, the groove of the first substrate may be formed by any method. When the groove is formed by wet etching, the depth error of the groove can be precisely controlled to about 0.5 μm or less.
The step of providing a waveguide layer in the first surface by bonding (S2) may include: step (S2-1): preparing a second substrate having a first insulating layer thereon, a semiconductor core layer on the first insulating layer, and a lower cladding layer on the semiconductor core layer; step (S2-2): bonding the first substrate and the second substrate through the first surface and the lower cladding layer; step (S2-3): removing the second substrate and the first insulating layer; step (S2-4): etching a portion of the semiconductor core layer to form a semiconductor core; step (S2-5): forming an insulator core layer covering the semiconductor core on the lower cladding layer, and forming an upper cladding layer covering the insulator core layer on the lower cladding layer.
The first insulating layer may have a thickness of about 0.2 μm, and the semiconductor core layer may have a thickness of about 200nm to 250 nm.
The step of preparing the second substrate (S2-1) may include: step (S2-1-1): bonding the second substrate and a third substrate through a second insulating layer on the semiconductor core layer and a third insulating layer on the third substrate; step (S2-1-2): removing the third substrate and forming the lower cladding layer, the lower cladding layer including the second insulating layer and the third insulating layer.
The thickness of the second insulating layer may be about 0.2 μm, and the thickness of the third insulating layer may be about 3 μm.
By bonding two insulating layers, thick layers can be prepared, but are difficult to prepare using the CMOS process.
The step of preparing the first substrate (S1) may include: step (S1-1): the recess is formed in the first surface by wet etching.
The step of preparing the first substrate (S1) may include: step (S1-2): forming a secondary lower cladding layer in the first substrate.
The thickness of the auxiliary lower cladding layer may be about 2 μm to 12 μm. The auxiliary lower cladding may be composed of the same material as the lower cladding.
The step of preparing the first substrate (S1) may include: step (S1-3): a trench is formed in the first surface by etching.
The step of forming the waveguide by etching a portion of the waveguide layer and exposing the groove (S3) may include: step (S3-1): etching a portion of the waveguide layer such that the waveguide portion overlies the groove.
The step of forming the waveguide by etching a portion of the waveguide layer and exposing the groove (S3) may include: step (S3-2): a portion of the waveguide layer is etched such that the semiconductor core is not exposed.
The step of forming the waveguide by etching a portion of the waveguide layer and exposing the groove (S3) may include: step (S3-3): the trench is exposed by etching a portion of the waveguide layer.
The first, second, and third substrates may be silicon substrates; the first, second, and third insulating layers may be SiO2A layer; the semiconductor core layer may be a silicon layer; the insulator core layer may be a SiOx layer (0)<x<2) (ii) a The lower cladding and the upper cladding may be SiO2And (3) a layer.
The groove may have a V-shaped cross-section in a plane perpendicular to the longitudinal direction of the optical fiber.
The difference between the distance from the first surface to the optical axis of the waveguide and the distance from the first surface to the optical axis of the optical fiber may be about 0.5 μm or less.
Furthermore, the present invention also provides a method for manufacturing an optical device, the method comprising: step (P1): preparing a first substrate, passing a third substrate through the lower cladding layer in the first surface, and passing a second substrate through the etch stop layer in the second surface; step (P2): providing a waveguide layer in the first surface of the first substrate; step (P3): forming a waveguide and a groove by etching the waveguide layer and a part of the first substrate to expose the etch stop layer; step (P4): an optical fiber is disposed in the groove.
Due to the etch stop layer, the depth of the groove formed in the first substrate is precisely controlled when the first substrate is etched. Therefore, the optical fiber disposed in the groove and the waveguide have excellent optical coupling.
The etch stop layer may comprise SiO2. The etch stop layer may be about 1 μm thick.
The step of preparing the first substrate (P1) may include: step (P1-1): bonding the first substrate and the second substrate through the etch stop layer on the second substrate.
The step of preparing the first substrate (P1) includes: step (P1-2): bonding the first substrate and the third substrate through the lower cladding layer on the first surface; step (P1-3): removing a portion of the first substrate.
The step of removing a portion of the first substrate (P1-3) may be performed by grinding and fine Chemical Mechanical Polishing (CMP). The thickness (H) of the first substrate obtained can be controlled to have an error of about 0.5 μm or less, preferably about 0.4 μm or less.
The step of providing a waveguide layer (P2) may comprise: step (P2-1): forming a semiconductor core by thinning the third substrate; step (P2-2): forming a semiconductor core by etching a portion of the semiconductor core layer; step (P2-3): forming an insulator core layer covering the semiconductor core on the lower cladding layer, and forming an upper cladding layer covering the insulator core layer on the lower cladding layer.
The thickness of the semiconductor core layer may be about 200nm to 250 nm.
The step of preparing the first substrate (P1) may include: step (P1-4): forming an intelligent peeling line by implanting impurities in the third substrate; the step of forming the semiconductor core layer (P2-1) may include: step (P2-1-1): peeling the third substrate along the smart peeling line.
The step of forming the waveguide and the groove (P3) may include: step (P3-1): a portion of the waveguide layer is etched such that the semiconductor core is not exposed.
The step of forming the waveguide and the groove (P3) may include: step (P3-2): the waveguide and the groove are formed by dry etching.
The step of forming the waveguide and the groove (P3) may include: step (P3-3): a trench is formed by etching the waveguide layer and a portion of the first substrate.
The step of preparing the first substrate (P1) may include: step (P1-5): a secondary under-cladding layer is formed within the first substrate.
The step of forming the waveguide and the groove (P3) may include: step (P3-4): and etching the first substrate to expose the auxiliary lower cladding layer.
The first, second, and third substrates may be silicon substrates; the semiconductor core layer may be a silicon layer; the insulator core layer may be a SiOx layer (0)<x<2) (ii) a The etch stop layer, the lower cladding layer, and the upper cladding layer may be SiO2And (3) a layer.
The groove may have a U-shaped or rectangular cross-section in a plane perpendicular to the longitudinal direction of the optical fiber.
The difference between the distance from the first surface to the optical axis of the waveguide and the distance from the first surface to the optical axis of the optical fiber may be about 0.5 μm or less.
The present invention can provide an optical device in which optical coupling between the waveguide and the optical fiber is improved by precisely aligning the waveguide and the optical fiber, and a method for manufacturing the optical device.
Drawings
Fig. 1 to 12 show a manufacturing process of the optical device provided by the first embodiment of the present invention;
fig. 13 shows the light device provided by a first variant of the first embodiment of the invention;
fig. 14 shows the optical device provided by a second variant of the first embodiment of the invention;
fig. 15 to 25 show a manufacturing process of the optical device provided by the second embodiment of the present invention;
fig. 26 to 36 show a manufacturing process of the optical device according to a variation of the second embodiment of the present invention;
FIG. 37 shows a perspective view of the light device of the present invention;
fig. 38 shows a cross-sectional view of the light device of the invention.
Detailed Description
Embodiments of the present invention will be described in detail below.
The present invention provides an optical device in which optical coupling between a waveguide and an optical fiber is improved by accurately aligning the waveguide and the optical fiber, and a method for manufacturing the optical device.
(first embodiment) referring to fig. 12, 37 and 38, the light device 10 of the first embodiment is described. Fig. 12 is a cross-sectional view of the optical device 10 along the optical axis 121 of the optical fiber 120 and the optical axis 111 of the waveguide 110. Fig. 37 is a perspective view of the optical device 10. Fig. 38 is a sectional view showing a positional relationship between the substrate 100 and the optical fiber 120 included in the optical device 10.
The light device 10 comprises the substrate 100, the substrate 100 having a V-shaped groove 102 and a groove 104 on a first surface 101; the waveguide 110, the waveguide 110 being provided on the first surface 101 of the substrate 100; the optical fiber 120, the optical fiber 120 being located in the V-groove 102; a light source 105, the light source 105 being located in the trench 104.
The waveguide 110 includes a lower cladding layer 112, a core layer 113, and an upper cladding layer 114, and the lower cladding layer 112, the core layer 113, and the upper cladding layer 114 are provided in this order on the first surface 101 of the substrate 100. The core layer 113 includes a semiconductor core 115 and an insulator core 116, and the insulator core 116 covers the semiconductor core 115. The waveguide 110 has a precise thickness because it is formed using conventional CMOS technology.
As shown in fig. 37, the V-shaped groove 102 of the substrate 100 has a V-shaped cross section in a plane perpendicular to the longitudinal direction of the substrate 100. The longitudinal direction of the substrate 100 corresponds to the y-axis in fig. 37. Fig. 38 shows a cross-sectional view of the V-groove 102 in which the optical fiber 120 is disposed. The V-shaped groove 102 is formed by using anisotropic wet etching. An etchant comprising potassium hydroxide (KOH) is capable of selectively etching (100) planes of silicon. The etch rate of the (100) plane is known to be about 100 times faster than the etch rate of the (111) plane. Therefore, the V-shaped groove 102 exposing the (111) plane is formed by anisotropic etching of the substrate 100 having the first surface 101 as the (100) plane. The V-shaped groove 102 formed by wet etching has a precise depth. Specifically, the V-shaped groove 102 formed by wet etching is precisely controlled with an error of about 0.5 μm or less.
Furthermore, the V-groove 102 may also have an inclined plane 108 in a plane parallel to the longitudinal direction of the optical fiber 120, as shown in fig. 12.
The optical fibers 120 are located in the V-grooves 102 with their depth precisely controlled. Accordingly, by disposing the optical fiber 120 in the V-groove, the optical axis 121 of the optical fiber 120 can be set to a desired height. Accordingly, the optical axis 121 of the optical fiber 120 disposed in the V-groove 102 and the optical axis 111 of the waveguide 110 are precisely aligned. Therefore, the optical fiber 120 and the waveguide 110 have excellent optical coupling.
The light source 105 is located in the groove 104. The light source 105 is connected to a predetermined circuit (not shown) by solder 107.
In the optical device 10 of the first embodiment, since the optical fiber 120 is disposed in the V-groove 102 formed by wet etching, the optical axis 111 of the waveguide 110 and the optical axis 121 of the optical fiber 120 are accurately aligned.
A first variation of the above-described first embodiment will be described below.
(first variation) the first variation of the first embodiment is shown in fig. 13. Fig. 13 is a cross-sectional view of the optical device 10 along the optical axis 121 of the optical fiber 120 and the optical axis 111 of the waveguide 110. A portion of the waveguide 110 extends along the first surface 101 of the silicon substrate 100 over the V-groove 102 (fig. 13). In the first embodiment, the V-shaped groove 102 is formed by anisotropic wet etching. The V-groove 102 has a V-shaped cross-section in a plane perpendicular to the longitudinal direction of the optical fiber 120. Further, the V-groove 102 may have an inclined plane 108 in a plane parallel to the longitudinal direction of the optical fiber 120. The inclined plane 108 of the V-groove 102 may cause a problem in that the distance between the waveguide 110 and the optical fiber 120 is widened to reduce optical coupling therebetween. The first variation may solve the problem that may arise in the first embodiment. In the first variation, since a portion of the waveguide 110 protrudes above the inclined plane 108 or above the inclined plane 108 and above the V-groove 102, the distance between the waveguide 110 and the optical fiber 120 is shortened, thereby improving optical coupling between the waveguide 110 and the optical fiber 120.
(second variation) the second variation of the first embodiment is shown in fig. 14. Fig. 14 is a cross-sectional view of the optical device 10 along the optical axis 121 of the optical fiber 120 and the optical axis 111 of the waveguide 110. In the second modification, as shown by a circle 142 in fig. 14, a thick region of the lower cladding 112 in an edge portion of the waveguide 110 near the optical fiber 120 is formed by forming a secondary lower cladding 103. This region is referred to as a Spot Size Converter (SSC) 142, and can enlarge the spot size of the waveguide 110. The auxiliary lower cladding 103 may be composed of the same material as the lower cladding 112. Without the auxiliary lower cladding layer 103, the thickness of the lower cladding layer 112 alone may not be sufficient. In this case, the signal from the light source 105 may be reflected by the silicon substrate 100 in the edge portion of the waveguide 110 and may not reach the optical fiber 120. By forming the auxiliary lower cladding layer 103, the lower cladding layer 112 can have a sufficient thickness at the edge portion of the waveguide 110. Therefore, since reflection of the silicon substrate 100 is suppressed at the edge portion of the waveguide 110, optical coupling between the waveguide 110 and the optical fiber 120 is improved.
(second embodiment) next, referring to fig. 25, a light device 20 of a second embodiment is described. Fig. 25 is a cross-sectional view of the optical device 20 along the optical axis 221 of the optical fiber 220 and the optical axis 211 of the waveguide 210. A description about the same structure as the optical device 10 of the first embodiment is omitted.
The optical device 20 of the second embodiment differs from the optical device 10 of the first embodiment in that the optical device 20 comprises a first substrate 200, an etch stop layer 231, a second substrate 230 and SiO2Layer 232. Further, the optical device 20 of the second embodiment and the first embodimentThe optical device 10 of an embodiment differs in that a U-shaped or rectangular groove 202 is formed in the first substrate 200.
In the optical apparatus 20 of the second embodiment, the first substrate 200 is provided on the etch stop layer 231. The waveguide 210 is provided on the first surface 201 of the first substrate 200. The U-shaped or rectangular groove 202 is formed in the first substrate 200 by completely removing a portion thereof in the depth direction. Since the distance from the first surface 201 of the first substrate 200 to the etch stop layer 231 (i.e., the thickness of the first substrate 200) is precisely controlled, the U-shaped or rectangular groove 202 formed by dry etching has a precise depth. Further, the U-shaped or rectangular groove 202 has a U-shaped or rectangular cross section in a plane perpendicular to the longitudinal direction of the base plate 200, respectively. The optical fibers 220 are disposed in the U-shaped or rectangular groove 202. Thus, the optical axis 221 of the optical fiber 220 disposed in the U-shaped or rectangular groove 202 and the optical axis 211 of the waveguide 210 are precisely aligned. Therefore, the optical fiber 220 and the waveguide 210 have excellent optical coupling.
The light source 205 is located in the trench 204. The light source 205 is connected to a predetermined circuit (not shown) by solder 207.
(variation) a variation of the second embodiment is shown in fig. 36. Fig. 36 is a cross-sectional view of the optical device 20 along the optical axis 221 of the optical fiber 220 and the optical axis 211 of the waveguide 210. In the variation, as shown by a circle 242 in fig. 36, a thick region of the lower cladding 212 in the edge portion of the waveguide 210 near the optical fiber 220 is formed by forming the auxiliary lower cladding 203. This region is referred to as a Spot Size Converter (SSC) 242, and can enlarge the spot size of the waveguide 210. The auxiliary lower cladding 203 may be composed of the same material as the lower cladding 212. Without the auxiliary lower cladding 203, the thickness of the lower cladding 212 alone may not be sufficient. In this case, the signal from the light source 205 may be reflected by the first substrate 200 in the edge portion of the waveguide 210, and may not reach the optical fiber 220. By forming the auxiliary lower cladding layer 203, the lower cladding layer 212 can have a sufficient thickness at the edge portion of the waveguide 210. Accordingly, since reflection of the silicon substrate 200 is suppressed at the edge portion of the waveguide 210, optical coupling between the waveguide 210 and the optical fiber 220 is improved.
Next, a method for manufacturing the optical device described in the above-described embodiment and the modifications is described as follows.
(first embodiment) fig. 1 to 12 show a method of manufacturing an optical device 10 for opto-electrically bonding structured SOI and silicon in the present invention. Fig. 1 to 12 are cross-sectional views of the optical device 10 along the optical axis 121 of the optical fiber 120 and the optical axis 111 of the waveguide 110.
The manufacturing process of the structured SOI is illustrated in fig. 1 to 5. Preparing a silicon substrate 130, the silicon substrate 130 having a thin BOX (SiO)2) Layer 131, thin silicon layer 115' and thin SiO2Layer 117 (fig. 1).
Next, a silicon substrate 140 is prepared, said silicon substrate 140 having a conventional thick thermally oxidized SiO on at least one surface thereof2Layers 118, 119. The thermal oxidation SiO2The thickness of the layers 118, 119 may be about 3 μm. The silicon substrate 130 and the silicon substrate 140 are bonded through the thin SiO using conventional bonding techniques2Layer 117 and the thermally oxidized SiO2The layers 118 are bonded. Increasing the thin SiO by high temperature annealing2Layer 117 and the thermally oxidized SiO2The bond strength of layer 118 (fig. 2).
Removing the thick SiO by grinding, etching or fine chemical mechanical polishing (CMP for short)2Layer 119 and the silicon substrate 140, and the thick SiO remaining2Layer 118 (fig. 3).
Another silicon substrate 100 is prepared and the V-shaped grooves 102 and the trenches 104 are formed in the first surface 101 thereof by conventional wet etching. The V-groove 102 is formed by selectively etching a (100) plane of silicon, for example, by using an etchant including potassium hydroxide (KOH). The etch rate of the (100) plane is known to be about 100 times faster than the etch rate of the (111) plane. Thus, the V shape of the (111) plane is exposedThe grooves 102 are formed by anisotropic etching of the substrate 100 in which the first surface 101 is a (100) plane. Next, the silicon substrate 100 and the silicon substrate 130 are bonded through the first surface 101 and the thick SiO using conventional bonding techniques2The layers 118 are bonded (fig. 4).
Then, the silicon substrate 130 is removed by grinding, etching, or fine Chemical Mechanical Polishing (CMP). Finally, the thin SiO is removed by etching using hydrofluoric acid (HF) or the like2Layer 131 (fig. 5).
Referring to fig. 1 to 5, a process of manufacturing the structured SOI having the V-shaped groove 102 is described. The subsequent processes shown in fig. 6-10 are conventional silicon waveguide formation processes compatible with CMOS.
The thick SiO2Layer 118 and the thin SiO2Layer 117 constitutes the lower cladding layer 112' (fig. 6).
A portion of the semiconductor core layer 115' is etched to form the semiconductor core 115 (fig. 7).
An insulator core layer 116 ' covering the semiconductor core 115 is formed on the under clad layer 112 ', and a side portion of the insulator core layer 116 ' is etched. An upper cladding layer 114 ' covering the insulator core layer 116 ' is formed on the lower cladding layer 112 ' (fig. 8).
The lower cladding layer 112 ', the semiconductor core 115, the insulator core layer 116', and the upper cladding layer 114 'constitute a waveguide layer 110'.
A portion of the waveguide layer 110' is removed by dry etching and the trench 104 is exposed (fig. 9).
A portion of the waveguide layer 110' is removed by dry etching, exposing the V-grooves 102 and forming the waveguide 110 (fig. 10). The waveguide 110 includes the lower cladding 112, the semiconductor core 115, the insulator core 116, and the upper cladding 114.
Solder 107 is formed in the trench 104 to dispose the light source 105 (fig. 11).
The optical fiber 120 is disposed in the V-groove 102 such that the optical axis 111 of the waveguide 110 and the optical axis 121 of the optical fiber 120 have optical coupling. Further, the light source 105 is disposed in the trench 104 by the solder 107 so that the waveguide 110 and the light source (LD) 105 have optical coupling (fig. 12).
In the first embodiment, the exposed V-shaped groove 102 is formed in advance by wet etching. Thus, the optical fiber 120 formed in the V-groove 102 is disposed at a desired position. In addition, the waveguide 110 is formed with high precision using conventional silicon waveguide formation processes. Therefore, the connection between the waveguide 110 and the optical fiber 120 achieves high accuracy through passive alignment, achieving high efficiency and low coupling loss.
The first embodiment is a method for manufacturing the light device 10 shown in fig. 12. The fabrication method of the present invention may provide the structured SOI using wafer bonding techniques. The structured SOI has conventional V-shaped grooves and trenches under the BOX layer of the SOI. Such an SOI can be used in a conventional silicon waveguide formation process compatible with CMOS because the surface of the SOI is completely planar. After the processes for forming the waveguide and the trench for the LD mesa are completed, the BOX layer on the V-shaped groove can be easily removed. Since the V-groove is formed with high accuracy by a wet etching process, alignment of the optical fiber and the waveguide is easily achieved.
(first variation) a first variation of the first embodiment is shown in fig. 13. Fig. 13 is a cross-sectional view of the optical device 10 along the optical axis 121 of the optical fiber 120 and the optical axis 111 of the waveguide 110. In the first embodiment, the waveguide layer 110' is etched such that the waveguide 110 does not protrude above the groove 102, as shown in fig. 10. Meanwhile, in the first variation, the waveguide 110' is etched such that the waveguide 110 protrudes above the V-groove 102 along the first surface 101, as shown in fig. 13. The waveguide 110 may protrude above the inclined plane 108 or be located above the V-groove 102 through the inclined plane 108. Since the V-shaped groove 102 is preformed in the substrate 100, an optical device as shown in fig. 13 can be obtained.
(second variation) a second variation for manufacturing the light device 10 is shown in fig. 14. The light device 10 shown in fig. 14 is manufactured similarly according to a variant of the second embodiment, which will be described below.
(second embodiment) the detailed flow of the second embodiment is shown in fig. 15 to 25. Fig. 15-25 are cross-sectional views of the optical device 20 along the optical axis 221 of the optical fiber 220 and the optical axis 211 of the waveguide 210. The processes shown in fig. 15-19 provide a SOI that includes two BOX layers 212', 231.
The smart cut line 241 is formed by implanting an impurity such as hydrogen into the silicon substrate 240 (fig. 15).
Then, a silicon substrate 200 is prepared, the silicon substrate 200 having thick SiO on both surfaces or on one surface (not shown)2Layers 212', 212 ". The silicon substrate 240 and the silicon substrate 200 are formed by the thick SiO2The layers 212' are bonded (fig. 16). The SiO2The layer 212 ' corresponds to the lower cladding layer 212 ' of the waveguide layer 210 '. The thickness of the thick SiO2 layers 212', 212 "of the silicon substrate 200 may be about 2 μm to 3 μm.
Subsequently, all of the SiO is removed by grinding and fine chemical mechanical polishing (CMP for short)2Layer 212 "and a portion of the silicon substrate 200 (fig. 17).
This process is carefully performed since the thickness (H) of the remaining silicon substrate 200 corresponds to the depth of the groove 202 in which the optical fiber 220 is disposed.
Next, a silicon substrate 230 is prepared, the silicon substrate 230 having a thin SiO layer on both surfaces or on one surface (not shown)2Layers 231, 232. The thin SiO2 layers 231, 232 may be about 1 μm thick.
The silicon substrate 200 and the silicon substrate 230 pass through the SiO2The layers 231 are bonded (fig. 18). The SiO2The layer 231 corresponds to the etch stop layer 231.
Then, the silicon substrate 240 is peeled along the pre-formed smart-peeling line 241 to obtain a thin silicon layer 215' (fig. 19). The thin silicon layer 215 ' corresponds to the semiconductor core layer 215 ' of the waveguide layer 210 '.
The processes shown in fig. 20-24 below are the same as the integrated process compatible with the CMOS flow. A semiconductor core 215 is formed by etching a portion of the semiconductor core layer 215' (fig. 20).
An insulator core layer 216 ' covering the semiconductor core 215 is formed on the under clad layer 212 ', and a side portion of the insulator core layer 216 ' is etched. An upper cladding layer 214 ' covering the insulator core layer 216 ' is formed on the lower cladding layer 212 ' (fig. 21). The lower cladding layer 212 ', the semiconductor core 215, the insulator core layer 216', and the upper cladding layer 214 'constitute the waveguide layer 210'.
Next, a portion of the waveguide layer 210' and a portion of the silicon substrate 200 are etched to form trenches 204 (fig. 22).
Before exposing the etch stop layer 231, a portion of the waveguide layer 210' and a portion of the silicon substrate 200 are etched to form a U-shaped or rectangular groove 202 (fig. 23). In the process shown in fig. 23, the U-shaped or rectangular groove 202 may be formed by dry etching. Since the SOI shown in FIG. 23 contains the SiO2Layer 231, thus the etch stops to SiO2And (3) a layer. Thus, a U-shaped or rectangular groove 202 having a controlled depth (depth, abbreviated as H) of about 0.5 μm or less can be obtained. Therefore, it is easy to achieve passive alignment between the optical fiber 220 disposed in the U-shaped or rectangular groove 202 and the waveguide 210.
Next, solder 207 is formed in the groove 204 to set a light source 205 (fig. 24).
The light source 205 is disposed in the groove 204 and the optical fiber 220 is disposed in the U-shaped or rectangular groove 202 (fig. 25).
In the second embodiment, in order to solve the problem that the accuracy of the dry etching is not high, the etching stopper layer 231 is provided between the silicon substrate 200 and the silicon substrate 230. By precisely controlling the depth of the first surface 201 of the substrate 200 to the etch stop layer 231, the depth of the recess 202 formed in the silicon substrate 200 is precisely defined. Accordingly, an optical device may be provided in which a positional error of the waveguide 210 between the optical axis 211 on the substrate 200 and the optical axis 221 of the optical fiber 220 disposed in the groove 202 is about 0.5 μm or less.
The second embodiment is a method for manufacturing the light device 20 shown in fig. 25. The optical device 20 includes two BOX layers 212', 231 as shown in fig. 19. The distance between the two BOX layers 212', 231, i.e., the thickness of the first substrate 200, is precisely controlled by an optimized value for forming the U-shaped or rectangular groove 202. Such an SOI can be used in a conventional silicon waveguide formation process compatible with CMOS because the surface of the SOI is completely planar. After the formation of the waveguide and the formation of the trench for the LD mesa are completed, since the BOX layer 231 is defined as an etch stop layer, a high-precision U-shaped or rectangular groove 202 is easily manufactured by a dry etching process.
(variation) referring to fig. 26 to 36, a variation of the second embodiment is described. The description of the portion overlapping with the second embodiment is omitted. Fig. 26-36 are cross-sectional views of the optical device 20 along the optical axis 221 of the optical fiber 220 and the optical axis 211 of the waveguide 210.
The processes shown in fig. 26-30 provide a SOI that includes two BOX layers 212', 231. The smart cut line 241 is formed by implanting an impurity such as hydrogen into the silicon substrate 240 (fig. 26).
Then, a silicon substrate 200 is prepared, the silicon substrate 200 having thick SiO on both surfaces or on one surface (not shown)2Layers 212', 212 ". The silicon substrate 240 and the silicon substrate 200 pass through the thick SiO of the silicon substrate 2002The layers 212' are bonded (fig. 27). As shown in FIG. 27, in the SiO2A secondary lower cladding 203 'is formed adjacent to layer 212'.
Subsequently, the SiO is removed by grinding and fine chemical mechanical polishing (CMP for short)2Layer 212 "and the silicon substrate 200 such that the secondary under-cladding layer 203' is not exposed (fig. 28).
Next, a silicon substrate 230 is prepared, the silicon substrate 230 being on two sidesWith thin SiO on one surface or on one surface (not shown)2Layers 231, 232. The silicon substrate 200 and the silicon substrate 230 pass through the SiO2The layers 231 are bonded (fig. 29).
Then, the silicon substrate 240 is peeled along the pre-formed smart-peeling line 241 to obtain a thin silicon layer 215' (fig. 30).
The process shown in fig. 31 to 35 is the same as the integrated process compatible with the CMOS flow. The process shown in fig. 31 to 33 is the same as the process shown in fig. 20 to 22. After the trenches are formed, a portion of the waveguide layer 210 ', a portion of the auxiliary lower cladding layer 203', and a portion of the silicon substrate 200 are etched until the etch stop layer 231 is exposed, thereby forming a waveguide 210, the waveguide 210 having the auxiliary lower cladding layer 203 and the grooves 202 (fig. 34). The process shown in fig. 35 and 36 is the same as the process shown in fig. 24 and 25.
Since the waveguide 210 has the auxiliary lower cladding 203 in the edge portion adjacent to the optical fiber 220, reflection of the silicon substrate 200 is suppressed, thereby improving optical coupling between the waveguide 210 and the optical fiber 220.
The disclosed manufacturing method can provide an optical device including a high-precision V-groove or U-groove or rectangular groove and a waveguide. Therefore, the positional error between the optical axis of the waveguide and the optical axis of the optical fiber can be set to a submicron order, thereby improving the optical coupling between the waveguide and the optical fiber.

Claims (13)

1. A light device, comprising:
a substrate having a groove on a first surface;
a waveguide on the first surface of the substrate;
a light source on the first surface of the substrate for delivering light to the waveguide;
an optical fiber located in the groove;
and the auxiliary lower cladding is positioned below the waveguide, and the distance from the auxiliary lower cladding to the optical fiber is smaller than the distance from the auxiliary lower cladding to the light source.
2. The optical apparatus of claim 1, wherein the waveguide comprises a lower cladding layer, a core layer, and an upper cladding layer.
3. The light device of claim 2, wherein the secondary lower cladding layer is the same material as the lower cladding layer.
4. A light device according to claim 2 or 3, characterized in that the core layer comprises a semiconductor core and an insulator core, the insulator core covering the semiconductor core.
5. The optical device according to claim 4, wherein the semiconductor core has a thickness between 200nm and 250nm in a plane perpendicular to the longitudinal direction of the waveguide.
6. A light device according to any one of claims 1-5, characterized in that the thickness of the auxiliary lower cladding is between 2 μm and 12 μm.
7. The optical device according to any of claims 1-6, wherein the difference between the distance of the first surface to the optical axis of the waveguide and the distance of the first surface to the optical axis of the optical fiber is not more than 0.5 μm.
8. A light device according to claim 2 or 3, characterized in that the surface of the core layer is flat.
9. An optical device according to claim 2 or 3, wherein the core layer comprises a silicon layer and SiOxLayer (0)<x<2)。
10. A light device according to any one of claims 1-9, characterized in that the groove has a V-shaped cross-section in a plane perpendicular to the longitudinal direction of the optical fiber.
11. The optical device according to any one of claims 1 to 9, wherein a portion of the waveguide protrudes above the groove in a longitudinal direction of the optical fiber.
12. A light device according to any one of claims 1-9, characterized in that the groove has a U-shaped or rectangular cross-section in a plane perpendicular to the longitudinal direction of the optical fiber.
13. A light device according to any one of claims 1 to 12, wherein the substrate has a trench, the light source being located in the trench in alignment with the waveguide.
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