CN116482814A - Optical system, integrated circuit and method of forming integrated circuit - Google Patents

Abstract

Various embodiments of the present invention are directed to integrated circuits. The integrated circuit includes a substrate having an upper face and a lower face. The upper face includes a central region and an outer sidewall laterally surrounding the central region and extending from the upper face to the lower face. An optical edge coupler is disposed above the upper face of the substrate, and the optical edge coupler extends in a first direction from the central region toward the outer sidewall. The outer side wall of the optical edge coupler corresponds to the outer side wall of the substrate and has a concave or convex surface. The embodiment of the invention also provides a method for forming the integrated circuit and an optical system.

Description

Optical system, integrated circuit and method of forming integrated circuit

Technical Field

Embodiments of the invention relate to optical systems, integrated circuits, and methods of forming integrated circuits.

Background

Optical edge couplers are commonly used as components in integrated optical circuits that integrate multiple photonic functions. The optical edge coupler is used to limit and direct light from a first point on an Integrated Chip (IC) to a second point on the IC with minimal attenuation. Typically, optical edge couplers provide functionality for signals applied at wavelengths of light in the visible spectrum (e.g., between about 850nm and about 1650 nm), although some optical edge couplers may also provide functionality for signals in other regions of the electromagnetic spectrum.

Disclosure of Invention

Some embodiments of the invention provide an integrated circuit comprising: a substrate having an upper face and a lower face, the upper face comprising a central region and an outer sidewall laterally surrounding the central region and extending from the upper face to the lower face; and an optical edge coupler disposed above the upper face of the substrate and extending in a first direction from the central region toward the outer sidewall, wherein the outer sidewall of the optical edge coupler corresponds to the outer sidewall of the substrate and has a concave or convex surface.

Further embodiments of the present invention provide an optical system comprising: an optical transmitter or receiver comprising an optical communication path; and an integrated circuit, the integrated circuit comprising: a substrate; an optical core over the substrate, the optical core having a first refractive index and being aligned with an optical communication path of the optical transmitter or receiver; a lower optical cladding layer over and separating the substrate from the optical core, the lower optical cladding layer having a second refractive index less than the first refractive index; and an upper optical cladding layer located above the optical core, the upper optical cladding layer having a second refractive index; and wherein the optical core has a concave or convex sidewall that corresponds to an outer edge of the substrate and is aligned with the optical communication path of the optical transmitter or receiver.

Still further embodiments of the present invention provide a method of forming an integrated circuit, comprising: a receiving substrate comprising a base substrate, a lower optical cladding layer over the base substrate, and an optical core over the lower optical cladding layer; forming an upper optical cladding over the optical core; performing an etching process to pattern the upper optical cladding layer, the optical core, the lower optical cladding layer, and the upper surface of the substrate to provide a patterned optical edge coupler having an outer sidewall with a substantially planar profile, the outer sidewall being spaced apart from an outermost edge of the substrate; and performing wet etching on the patterned optical edge coupler to recess the outer sidewall of the optical core relative to the outer sidewall of the lower optical cladding and the outer sidewall of the upper optical cladding.

Drawings

Aspects of the invention are best understood from the following detailed description when read in connection with the accompanying drawing figures. It should be noted that the various components are not drawn to scale according to standard practice in the industry. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

Fig. 1 illustrates a top view of some embodiments of an optical edge coupler.

Fig. 2 illustrates a cross-sectional view of some embodiments consistent with the optical edge coupler of fig. 1.

Fig. 3-6 illustrate cross-sectional views of some embodiments of optical edge couplers, each including a raised outer sidewall.

Fig. 7-11 illustrate cross-sectional views of some embodiments of optical edge couplers, each including a recessed outer sidewall.

Fig. 12-19 illustrate cross-sectional views of some embodiments of optical edge couplers including an optical core having concave or convex outer sidewalls and an anti-reflective coating (ARC) layer having inner sidewalls that matingly engage the concave or convex outer sidewalls of the optical core.

Fig. 20-27 illustrate perspective views of some embodiments of slab waveguide form optical edge couplers, each including raised outer sidewalls.

Fig. 28-35 illustrate perspective views of some embodiments of optical edge couplers in the form of channel waveguides, each of which includes a raised outer sidewall.

Fig. 36 illustrates a perspective view of some embodiments of rib waveguides including concave or convex outer sidewalls.

Fig. 37 shows a perspective view of some embodiments of a slot waveguide comprising two segments, each segment comprising a concave or convex outer sidewall.

Fig. 38-49 show perspective views of some additional embodiments of optical edge couplers.

Fig. 50-52 illustrate perspective views of some additional embodiments of optical edge couplers.

Fig. 53 illustrates a flow chart of a method of manufacturing an optical edge coupler, according to some embodiments.

Fig. 54, 55, 56, 57, 58A-58B, and 59 illustrate a series of cross-sectional views that collectively depict some fabrication methods according to some embodiments.

Detailed Description

The following disclosure provides many different embodiments, or examples, of the different components used to implement the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. Of course, these are merely examples and are not intended to be limiting. For example, in the following description, forming a first component over or on a second component may include embodiments in which the first component and the second component are formed in direct contact, and may also include embodiments in which additional components may be formed between the first component and the second component, such that the first component and the second component may not be in direct contact. Furthermore, the present invention may repeat reference numerals and/or characters in the various embodiments. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms such as "under …," "under …," "lower," "above …," "upper," and the like may be used herein for ease of description to describe one element or component's relationship to another element(s) or component(s) as illustrated. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

Optical edge couplers may use light or other electromagnetic waves to provide high-speed signal communication. Generally, the use of light or other electromagnetic waves provides lower power consumption and less heating than conventional electrical signals.

Fig. 1 and 2 illustrate examples of optical systems 100 according to some embodiments, fig. 1 and 2 illustrate top views and corresponding cross-sectional views, and fig. 1 and 2 are now described concurrently. The optical system 100 includes an optical transmitter or receiver 102, such as a chip, optical fiber, or other component, configured to transmit and/or receive optical signals along an optical communication path 104. The integrated circuit 106 is configured to interact with the optical transmitter or receiver 102 through the optical communication path 104. In some embodiments, integrated circuit 106 may include circuitry or other structures 108 that may generate optical signals, detect optical signals, analyze optical signals, modify optical signals, transmit optical signals, and/or convert optical signals to electrical signals (and vice versa); thereby ensuring communication and/or signal processing between the integrated circuit 106 and the optical transmitter or receiver 102.

Integrated circuit 106 includes a substrate 110 having an upper surface 114 and a lower surface 116, and an optical edge coupler 112 disposed on upper surface 114 of substrate 110. The upper surface 114 includes a central region 114c, and the outer sidewall 118 laterally surrounds the central region 114c and extends from the upper surface 114 to the lower surface 116. The optical edge coupler 112 is disposed above the upper surface of the substrate and extends in a first direction from the central region 114c toward the outer sidewall 118.

The optical edge coupler includes a core 120, a lower cladding layer 122 separating the core 120 from the substrate 110, and an upper cladding layer 124 disposed over the core 120. The optical core 120 is disposed over the substrate 110 and aligned with the optical communication path 104 of the optical transmitter or receiver 102. The optical core 120 has a first refractive index. Lower light cladding layer 122 has a second refractive index that is less than the first refractive index. The upper light cladding layer 124 also typically has a second refractive index.

The optical core 120 has an outer sidewall 120s positioned on the optical communication path 104. Thus, when a signal is transmitted and/or received on the optical communication path 104 between the optical transmitter or receiver 102 and the integrated circuit 106, the signal enters and/or exits the optical core 120 through the outer sidewall 120s. The outer sidewall 120s generally corresponds to the outer sidewall 118 of the substrate 110 and may have an outermost point recessed from the outer sidewall 118 of the substrate 110 by a distance d or have an outermost point aligned (e.g., coplanar) with the outer sidewall 118 of the substrate 110. The outer sidewall 120s may have various contours depending on the embodiment. In some embodiments, substrate 110, optical core 120, and lower optical cladding layer 122 are formed from a silicon-on-insulator (SOI) substrate, where substrate 110 corresponds to a handle substrate of the SOI substrate, lower optical cladding layer 122 corresponds to an insulating layer of the SOI substrate, and optical core 120 corresponds to a silicon device layer of the SOI substrate.

In some cases, the outer sidewall 120s of the optical core 120 has a planar profile 120p that aligns with corresponding outer sidewalls (122 s, 124 s) of the lower and upper optical cladding layers (122, 124, respectively). However, in order to achieve good transmission efficiency between the integrated circuit 106 and the optical transmitter or receiver 102 having such a planar profile 120p, a lens 126 is typically inserted along the optical communication path 104 in this case.

As has been appreciated in some aspects of the invention, changing the profile of the outer sidewall 120s of the optical core 120 to concave or convex may increase the beam pointing and coupling efficiency of the optical edge coupler 112, thereby reducing the need for the lens 126. Thus, some embodiments may reduce cost and manufacturing complexity by having no lenses between the optical edge coupler 112 and the optical transmitter or receiver 102. It should be understood that the term "concave or convex" as used in this disclosure is not limited to curved surfaces having a single radius of curvature, but may also include surfaces having a plurality of flat facets, a plurality of radii of curvature, and/or a combination of one or more flat facets and one or more radii of curvature. Thus, the concave or convex sidewalls may include any protruding shape, including triangular, polygonal, circular or oval portions, and the like.

As shown in fig. 2, when the outer sidewall 120s has a raised profile 120x, the raised profile 120x facilitates beam pointing, which may be advantageous when light entering or exiting the optical edge coupler becomes narrower (e.g., more focused) away from the outer sidewall 120s than when a planar sidewall 120p is used. Furthermore, when the outer side wall 120s has a concave profile 120v, the concave profile 120v facilitates beam widening, which may be advantageous when light entering or exiting the optical edge coupler becomes wider (e.g., more diffuse) away from the outer side wall 120s than when a planar side wall 120p is used.

In some embodiments, the optical core 120 is made of a first material and the lower optical cladding 122 and/or the upper optical cladding 124 is made of a second material. The first material may have a first refractive index that is greater than a second refractive index of the second material. For example, in some cases, the first refractive index is between 25% and 300% greater than the second refractive index, or between 50% and 150% greater than the second refractive index. In some embodiments, the first material may include monocrystalline silicon, polycrystalline silicon, amorphous silicon, or silicon nitride (e.g., si ₃ N ₄ ) And the first material may have a refractive index in a range between about 2 to about 3.5, and the second material may comprise silicon dioxide, and the second material may have a refractive index between 1.4 to 1.5. In some embodiments, the substrate 110 is a monocrystalline silicon substrate.

Furthermore, in some embodiments, the thicknesses of the optical core 120, the lower optical cladding 122, and the upper optical cladding 124 may be approximately equal when measured perpendicular to the upper surface 114 of the substrate 110; however, in other embodiments, the optical core 120, the lower optical cladding 122, and the upper optical cladding 124 may have different thicknesses. Thus, in some cases where the substrate is a silicon-on-insulator (SOI) substrate and the optical core 120 corresponds to the silicon/device layer of the SOI substrate and the lower optical cladding 122 corresponds to the insulator layer of the SOI substrate, the upper optical cladding 124 may be thinner than the optical core 120 and the lower optical cladding 122. For example, in some embodiments, the optical core 120 may have a thickness of about 3 microns +/-0.1 microns, the lower optical cladding 122 may have a thickness of about 2 microns +/-0.1 microns, and the upper optical cladding 124 may have a thickness of about 1.5 microns +/-0.1 microns. Although some waveguides and/or optical couplers according to the present disclosure have upper and lower optical cladding layers of the same thickness, it should be appreciated that making upper optical cladding layer 124 thinner than lower optical cladding layer 122 provides manufacturing efficiencies that cannot be achieved with upper and lower optical cladding layers of the same thickness.

Referring now collectively to fig. 3-6, various cross-sectional views of some embodiments of optical edge couplers 112 may be seen, each optical edge coupler 112 including an outer sidewall 120s having a raised profile. In each illustrated example, the outer sidewall 120s of the optical core 120 protrudes outward beyond at least one of the outer sidewall 124s of the upper optical cladding 124 and/or the outer sidewall 122s of the lower optical cladding 122. In addition, outer sidewall 124s of upper optical cladding layer 124 and/or outer sidewall 122s of lower optical cladding layer 122 are traversed by plane 300, and optical core 120 has a varying thickness as measured perpendicular to plane 300 from lower optical cladding layer 122 to upper optical cladding layer 124. Thus, the raised profile of the optical core 120 has varying thicknesses (e.g., a first thickness t1 and a second thickness t2, where t1> t 2) at various heights in the optical core

In fig. 3, the raised outer sidewall 120s includes an upper planar facet 302 and a lower planar facet 304 that intersect at a point 306. In the example of fig. 3, the point 306 is disposed along the centerline 120m of the optical core. The midlines 120m are equally spaced between the upper surface 120u of the core and the lower surface 120l of the core. The upper planar facet 302 intersects the upper surface 120u of the optical core at a first angle θ1 and the lower planar facet 304 intersects the lower surface 120l of the optical core at a second angle θ2. In some embodiments, θ1 and θ2 are both greater than 90 degrees and equal to each other, such that the optical edge coupler 112 is symmetrical about a centerline 120m running along the length of the optical core. In some cases, θ1 and θ2 may be in a range between 92 degrees and 150 degrees, although other ranges are possible. Furthermore, the outer side wall 124s of the upper light cladding layer and the upper planar facet 302 are planar, and the outer side wall 122s of the lower light cladding layer and the lower planar facet 304 are planar, although in other embodiments these surfaces may be offset or "kinked" with respect to each other.

In fig. 4, outer sidewall 120s is a continuously curved surface in the form of an ellipse or oval extending from lower light cladding layer 122 to upper light cladding layer 124. Thus, since the outer sidewall 120s shown in FIG. 4 is elliptical or oval, the radius of curvature of the outer sidewall 120s varies at different points on the outer sidewall. In other embodiments, the continuously curved surface may take the form of a semi-circular or rounded portion or a spherical portion, with a single, fixed radius of curvature over the entire curve. In fig. 4, the outer side wall 124s of the upper light cladding layer 124 and the outer side wall 122s of the lower light cladding layer 122 are coplanar with each other, however they may also be angled/tapered, as shown for example in fig. 3.

In fig. 5, the outer sidewall 120s includes an upper planar facet 502 and a lower planar facet 504 that intersect at a middle planar facet 506. The intermediate planar facet 506 is traversed by the midline 120m of the optical core. In fig. 4, the outer sidewalls of the upper and lower light cladding layers are coplanar with each other (and along plane 300), however they may also be angled/tapered, as shown for example in fig. 3.

In fig. 6, the outer sidewall 120s includes an upper planar facet 602 and a lower planar facet 604. The lower planar facet 604 is coplanar with the outer sidewall 122s of the lower light cladding layer. Thus, the lower planar facet 604 and the outer sidewall of the lower optical cladding are perpendicular and perpendicular relative to the upper surface of the substrate (not shown). In other embodiments, the outer sidewall 124s of the upper light cladding may also be vertical and may correspond to the plane 300.

Fig. 7-11 illustrate cross-sectional views of some embodiments of optical edge couplers 112, each optical edge coupler 112 including an optical core 120 having an outer sidewall with a concave profile. Thus, in each of fig. 7-11, the outer sidewall 124s of the upper optical cladding 124 and/or the outer sidewall 122s of the lower optical cladding 122 protrudes outwardly beyond the outer sidewall 120s of the optical core 120, creating a concave profile.

In fig. 7, the concave outer sidewall 120s includes an upper planar facet 702 and a lower planar facet 704 that intersect at a point 706. In the example of fig. 7, the points 706 are disposed along the centerline of the optical core and are equally spaced between the upper surface 120u of the optical core and the lower surface 120l of the optical core. The upper planar facet 702 intersects the upper surface 120u of the optical core at a first angle θ1 and the lower planar facet 704 intersects the lower surface 120l of the optical core at a second angle θ2. In some embodiments, θ1 and θ2 are each less than 90 degrees and equal to each other, such that the optical edge coupler 112 is symmetrical about a centerline 120m running along the length of the optical core. In some cases, θ1 and θ2 may be in a range between 88 degrees and 40 degrees, although other ranges are possible. Further, the outer sidewalls of upper light cladding layer 124 and lower light cladding layer 122 are shown as being perpendicular and thus non-coplanar with upper planar facet 702 and lower planar facet 704, but in other embodiments, outer sidewall 124s of upper light cladding layer 124 may be coplanar with upper planar facet 702 and outer sidewall 122s of lower light cladding layer 122 may be coplanar with lower planar facet 704.

In fig. 8, the outer sidewall 120s includes an upper planar facet 802 and a lower planar facet 804 that intersect at a middle planar facet 806. The intermediate planar facet 806 is disposed along the centerline 120m of the optical core. In fig. 8, the outer sidewalls 122s, 124s of the lower and upper light cladding are coplanar with each other, however they may also be angled/tapered, as shown for example in fig. 3.

In fig. 9, outer sidewall 120s is a continuously curved surface in the form of a rounded portion extending from lower light cladding layer 122 to upper light cladding layer 124. Thus, the continuous curved surface is shown as a rounded or spherical portion and has a single, fixed radius of curvature throughout the curve. In other embodiments, the outer sidewall 120s may be elliptical or oval, with the outer sidewall 120s having a varying sidewall radius of curvature at different points on the concave outer sidewall.

In fig. 10, the outer sidewall 120s includes a series of discrete steps or squares that increase in depth from the upper and lower surfaces 120u, 120l to the midline 120 m. Each step includes a horizontal plane and a vertical plane, which may have equal lengths and may intersect each other at about 90 degrees.

Fig. 11 depicts an example somewhat similar to fig. 8, in which the outer sidewall 120s includes an upper planar facet 1102 and a lower planar facet 1104 that intersect at a middle planar facet 1106. However, in fig. 11, the upper planar facet 1102 and the lower planar facet 1104 are disposed along the 111 face of the crystal of the optical core 120, and the intermediate planar facet 1106 is disposed along the 100 face of the crystal of the optical core. Further, the upper optical cladding 124 has a tapered outer sidewall 124s, so that the portion closest to the optical core extends further outward than the portion furthest from the optical core. Lower light cladding layer 122 has an angled outer sidewall 122s, but angled outer sidewall 122s is asymmetric with the sidewall of upper light cladding layer 124.

Fig. 12-19 illustrate cross-sectional views of some embodiments of optical edge couplers that include an anti-reflective coating (ARC) layer 1200 disposed on the outer sidewall 120s. Thus, in each of fig. 12-19, ARC layer 1200 has an inner sidewall that matingly engages the outer sidewall of the optical edge coupler. ARC layer 1200 has a third refractive index that is less than the refractive index of Yu Guangxin and greater than the refractive index of air (or any surrounding environment surrounding the optical edge coupler). In some cases, the third refractive index may also be less than the refractive index of the upper and/or lower light cladding layers 122, 124, may be equal to the refractive index of the upper and/or lower light cladding layers 122, 124, or may be greater than the refractive index of the upper and/or lower light cladding layers 122, 124. In the illustrated embodiment, the ARC layer 1200 has a varying thickness along the outer sidewall of the optical edge coupler such that the outer sidewall of the anti-reflective coating terminates at the planar surface 1200o. ARC layer 1200 may be a single film or may include multiple layers stacked over outer sidewall 120s. If multiple layers are used, each layer is oriented in a generally vertical direction (e.g., covering the outer side walls of the optical core and the outer side walls of the upper and lower optical cladding layers).

Fig. 20-27 illustrate perspective views of some embodiments of optical edge couplers in the form of "slab" waveguides, each of which includes a raised outer sidewall 120s. Fig. 20-23 are generally identical to fig. 3-6 and depict an optical core 120 sandwiched between a lower optical cladding layer 122 and an upper optical cladding layer 124. Each depicted slab waveguide extends generally in a first direction (e.g., left to right on a page) and has planar sidewalls extending in a direction parallel to the first direction, and a planar top surface. In fig. 24, the upper and lower optical cladding layers are rounded, so the outer sidewall profile of the optical edge coupler is a continuous curved surface with an outermost limit corresponding to the optical core 120. In fig. 25, the upper and lower optical cladding layers are rounded, so the outer sidewall profile of the optical edge coupler is a continuous curved surface, but here the outermost limit of the outer sidewall corresponds to the bottom of the lower optical cladding layer 122. In fig. 26, the outer side wall of the optical core ends at a point, whereas in fig. 27, the outer side wall is rounded or bulbous when viewed in perspective. Although fig. 20-27 depict examples corresponding to raised outer sidewalls, recessed profiles may also be used (see, e.g., fig. 7-11), and/or an ARC layer may be provided on the outer sidewalls (see, e.g., fig. 12-19).

Fig. 28-35 illustrate perspective views of some embodiments of channel waveguides, each comprising a raised outer sidewall. In contrast to slab waveguides (see, e.g., fig. 20-27, where the optical core is sandwiched between an upper optical cladding layer and a lower optical cladding layer), channel waveguides have optical cores axially surrounded on all sides by an optical cladding material that has a lower refractive index than the optical cores. Although the channel waveguides are shown in fig. 28-35 as having convex outer sidewalls, the outer sidewalls of the optical cores may optionally have concave profiles (see, e.g., fig. 7-11), and/or ARC layers may be provided on the outer sidewalls (see, e.g., fig. 12-19) to provide high optical coupling efficiency with other components.

Fig. 36 illustrates a perspective view of some embodiments of a rib waveguide 3600, the rib waveguide 3600 including an outer sidewall 120s having a concave or convex profile. The rib waveguide includes an optical core 120, the optical core 120 having a base 3602 and a rib 3604 extending upward from an upper portion of the base 3602. The rib 3604 perpendicularly intersects the end cap structure 3606 also disposed above the base. The rib waveguide includes an outer sidewall 120s having a convex or concave profile, such as shown in fig. 3-35, or may have other profiles shown and/or described herein.

Fig. 37 shows a perspective view of some embodiments of a slot waveguide 3700, the slot waveguide 3700 comprising a first segment 3702 and a second segment 3704 extending in parallel in a first direction with a slot 3706 therebetween above an upper surface of the substrate 110. The first segment 3702 includes a first outer sidewall 120s-1 having a first concave or convex profile, and the second segment 3704 includes a second outer sidewall 120s-2 also having the same concave or convex profile. Thus, in some cases, the first and second outer sidewalls may have the same convex or concave profile, such as shown in fig. 3-35, or may have other profiles shown and/or described herein, while in other cases, the first and second outer sidewalls may have profiles that are different from one another.

Fig. 38-47 illustrate perspective views of some additional embodiments of optical edge couplers. In these cases, the optical edge coupler includes an optical core 3820 having an outer sidewall 120s, the outer sidewall 120s having a concave or convex profile. However, the optical edge coupler of fig. 38-47 includes a left light cladding layer 3822 and a right light cladding layer 3824 disposed at the same height above the substrate 110, rather than having an upper light cladding layer and a lower light cladding layer as shown in the previous embodiments.

Fig. 48-49 illustrate perspective views of some additional embodiments of optical edge couplers. In fig. 48 to 49, the optical edge coupler again has an optical core sandwiched between a lower optical cladding layer and an upper optical cladding layer, but here the convex profile is observed along a section taken parallel to the upper surface of the substrate 110. Additional raised profiles and/or recessed profiles (optionally with an ARC layer), such as those previously shown and/or described, may also be oriented in this manner, with fig. 48-49 being only non-limiting examples.

Fig. 50-52 illustrate perspective views of some additional embodiments of optical edge couplers. As shown in fig. 50, the optical edge coupler or waveguide may include a plurality of branches disposed on or above an upper surface of the substrate 110 and horizontally spaced apart from one another. Each branch may terminate in an outer sidewall 120s having a concave or convex profile and may optionally be covered by an ARC layer.

As shown in fig. 51, the optical edge coupler or waveguide may include a plurality of branches disposed on or above the upper surface of the substrate 110 and vertically spaced apart from each other. Each branch may terminate in an outer sidewall 120s having a concave or convex profile and may optionally be covered by an ARC layer.

As shown in fig. 52, the optical edge coupler or waveguide may include a plurality of branches disposed on or over the upper surface of the substrate 110, with the branches being laterally and horizontally spaced apart from one another. Each branch may terminate in an outer sidewall 120s having a concave or convex profile and may optionally be covered by an ARC layer.

Fig. 53 illustrates a flow chart of a method of manufacturing an optical edge coupler, according to some embodiments.

At 5302, a substrate is received.

At 5304, a lower optical cladding layer is formed over the substrate.

At 5306, an optical core is formed over the lower optical cladding layer. As represented by 5308, in some embodiments 5302, 5304, and 5306 are produced by a fabrication facility that transports a semiconductor-on-insulator (SOI) substrate having a semiconductor processing wafer, an insulator layer above the semiconductor processing wafer, and a semiconductor device layer above the insulator layer. Thus, in some cases, method 5300 begins by simply obtaining an SOI substrate, where the substrate of 5302 corresponds to a handle substrate of the SOI substrate, the lower optical cladding corresponds to an insulator layer of the SOI substrate, and the optical core corresponds to a semiconductor device layer of the SOI substrate.

At 5310, an upper optical cladding layer is formed over the optical core.

At 5312, an etching process is performed to pattern the upper optical cladding layer, the optical core, the lower optical cladding layer, and the upper surface of the substrate to provide a patterned optical edge coupler having an outer sidewall spaced apart from an outermost edge of the substrate.

At 5314, etching is performed on the patterned optical edge coupler to reshape the outer sidewall of the optical core relative to the outer sidewall of the lower optical cladding and the outer sidewall of the upper optical cladding. In this way, an outer sidewall with a concave or convex profile can be formed for the optical edge coupler.

In some cases, the etching in 5314 is a wet etching that produces an outer sidewall of the optical core having a plurality of planar facets (e.g., 111 planar facets and 100 planar facets) that intersect at respective intersections. Optionally, after such wet etching, an annealing operation is performed to reflow the core material to transform the plurality of planar facets into a continuous curved surface between the upper and lower optical cladding layers.

In 5316, an ARC layer is optionally formed over the outer sidewall, wherein the ARC layer has an inner sidewall matingly engaging the outer sidewall of the optical core.

Fig. 54, 55, 56, 57, 58A-58B, and 59 illustrate a series of cross-sectional views that collectively depict some fabrication methods according to some embodiments.

In fig. 54, a substrate 5600 is received. In the example shown, the substrate received is a semiconductor-on-insulator (SOI) substrate having a semiconductor processing wafer, an insulator layer over the semiconductor processing wafer, and a semiconductor device layer over the insulator layer. Semiconductor processing wafers typically comprise single crystal silicon, insulator layers comprise silicon dioxide or high-k dielectric layers, and semiconductor device layers comprise silicon or silicon nitride.

In fig. 55, an upper optical cladding layer 124 is formed over the semiconductor device layer. The upper optical cladding layer is an insulating material, and in some cases the upper optical cladding layer may have the same material composition as the insulator layer. Thus, in some embodiments, the upper optical cladding layer may comprise silicon dioxide or a high-k dielectric material. Notably, in fig. 55, the reference numerals reflect the named variations, the handle wafer 5602 may be referred to as the substrate 110, the insulator layer 5604 may be referred to as the lower optical cladding layer 122, and the device layer 5606 may be referred to as the optical core 120. Lower optical cladding layer 122, optical core 120, and upper optical cladding layer 124 may be included in optical edge coupler 112 disposed over substrate 110.

In fig. 56, a first etching process is performed to pattern upper optical cladding layer 124, optical core 120, lower optical cladding layer 122, and an upper portion of substrate 110 to provide a patterned optical edge coupler having an outer sidewall 118' spaced apart from outer sidewall 118 of the substrate. In general, the first etching process includes forming a mask over upper optical cladding layer 124, wherein the mask covers some portions of upper optical cladding layer 124 and exposes other portions of the upper optical cladding layer, and performing an etch to remove the exposed portions of the upper optical cladding layer and the lower portion of optical core 120, lower optical cladding layer 122, and portions of substrate 110. The outer sidewall 118' formed by the first etching process may be a substantially flat sidewall and may extend from the upper surface of the upper light-cladding layer 124 to a narrow mesa 110l formed in the substrate 110. In some cases, the first etching process may include dry etching, but other etches may also be used.

In fig. 57, a second etching process is performed on the outer sidewall 118' to reshape the outer sidewall 120s of the optical core 120 relative to the outer sidewall 122s of the lower optical cladding 122 and the outer sidewall 124s of the upper optical cladding 124. In this way, an outer sidewall 120s with a concave or convex profile may be formed for the optical edge coupler. In some cases, the second etching process is a wet etch in the form of a tetramethylammonium hydroxide (TMAH) etch. In some cases, the second etching process produces an outer sidewall of the optical core having a plurality of planar facets (e.g., 111 planar facets and 100 planar facets).

In fig. 58A, fig. 58A may optionally be derived from fig. 57, with an annealing operation being performed to reflow the material of the optical core 120 to transform the plurality of planar facets on the outer sidewall 120s into a continuous curved surface between the upper optical cladding and the lower optical cladding.

In fig. 58B, fig. 58B may alternatively be derived from fig. 57, with ARC layer 5800 formed on the facets of outer sidewall 120s shown in fig. 57. The ARC layer has an inner sidewall that matingly engages the facets on the outer sidewall of the optical core.

In fig. 59, fig. 59 may alternatively be derived from fig. 58A, with an ARC layer 5900 formed on the continuously curved surface of the outer sidewall 120s shown in fig. 58A. The ARC layer has an inner sidewall matingly engaging the continuous curved surface on the outer sidewall of the optical core.

Various embodiments of the present invention are directed to integrated circuits. The integrated circuit includes a substrate having an upper face and a lower face. The upper face includes a central region and an outer sidewall laterally surrounding the central region and extending from the upper face to the lower face. An optical edge coupler is disposed above the upper face of the substrate and extends in a first direction from the central region toward the outer sidewall. The outer side wall of the optical edge coupler corresponds to the outer side wall of the substrate and has a concave or convex surface.

In some embodiments, the optical edge coupler comprises: an optical core extending in a first direction over a substrate; a lower light cladding layer extending in a first direction over the substrate and separating the optical core from the substrate; and an upper light cladding layer extending in the first direction and disposed over the light core.

In some embodiments, the outer sidewall of the optical core protrudes outwardly beyond at least one of the outer sidewall of the upper optical cladding or the outer sidewall of the lower optical cladding, wherein the outer sidewall of the upper optical cladding and the outer sidewall of the lower optical cladding are traversed by a plane and the optical core has a varying thickness as measured perpendicular to the plane from the lower optical cladding to the upper optical cladding.

In some embodiments, the upper and lower optical cladding layers comprise silicon dioxide and the optical core comprises silicon or silicon nitride.

In some embodiments, the outer side wall of the upper optical cladding layer or the outer side wall of the lower optical cladding layer protrudes outward beyond the outer side wall of the optical core, wherein the outer side walls of the upper optical cladding layer and the outer side walls of the lower optical cladding layer are traversed by a plane and the outer side walls of the optical core are spaced apart from the plane by a varying distance as measured perpendicular to the plane from the lower optical cladding layer to the upper optical cladding layer.

In some embodiments, the concave or convex surface is a continuously curved surface extending from the lower light cladding layer to the upper light cladding layer.

In some embodiments, the concave or convex surface comprises an upper planar facet and a lower planar facet intersecting at a point disposed along a midline of the optical core, the midline of the optical core being equally spaced between the upper surface of the optical core and the lower surface of the optical core.

In some embodiments, the concave or convex surface comprises an upper planar facet and a lower planar facet intersecting at a middle planar facet disposed along a centerline of the optical core, the centerline of the optical core being equally spaced between the upper surface of the optical core and the lower surface of the optical core.

In some embodiments, the integrated circuit further comprises: an anti-reflection coating disposed on the outer sidewall of the optical edge coupler, the anti-reflection coating having an inner sidewall matingly engaging the outer sidewall of the optical edge coupler and having a varying thickness along the outer sidewall of the optical edge coupler such that the outer sidewall of the anti-reflection coating terminates in a planar surface.

In some embodiments, the outer sidewall of the optical core includes an upper planar facet and a lower planar facet, wherein the lower planar facet is coplanar with the outer sidewall of the lower optical cladding.

In some embodiments, the outer sidewall of the optical core comprises a series of discrete steps or squares that increase in depth from the upper surface of the optical core and from the lower surface of the optical core to the midline of the optical core.

Other embodiments relate to an optical system including a light emitter or receiver including an optical communication path. An integrated circuit includes a substrate and an optical core over the substrate. The optical core has a first refractive index and is aligned with an optical communication path of the optical transmitter or receiver. A lower optical cladding layer is disposed over the substrate and separates the substrate from the optical core. The lower optical cladding layer has a second refractive index that is less than the first refractive index. The upper optical cladding is disposed over the optical core. The upper light cladding layer has a second refractive index. The optical core has concave or convex sidewalls corresponding to the outer edge of the substrate and aligned with the optical communication path of the optical transmitter or receiver.

Another embodiment of the present invention is directed to an optical system including: an optical transmitter or receiver comprising an optical communication path; and an integrated circuit, the integrated circuit comprising: a substrate; an optical core over the substrate, the optical core having a first refractive index and being aligned with an optical communication path of the optical transmitter or receiver; a lower optical cladding layer over and separating the substrate from the optical core, the lower optical cladding layer having a second refractive index less than the first refractive index; and

an upper optical cladding layer located above the optical core, the upper optical cladding layer having a second refractive index; and wherein the optical core has a concave or convex sidewall that corresponds to an outer edge of the substrate and is aligned with the optical communication path of the optical transmitter or receiver.

In some embodiments, there is no lens on the optical communication path between the light emitter or receiver and the concave or convex sidewall.

In some embodiments, the integrated circuit further comprises circuitry or other structure operatively coupled to the optical transmitter or receiver via an optical communication path, the circuitry or other structure configured to generate, detect, analyze, modify, and/or redirect electromagnetic radiation to or from the optical transmitter or receiver.

In some embodiments, the integrated circuit further comprises: an anti-reflective coating film disposed on the concave or convex sidewalls of the optical core, the anti-reflective coating film having inner sidewalls matingly engaging the concave or convex sidewalls and having a varying thickness along the concave or convex sidewalls such that the outer sidewalls of the anti-reflective coating film terminate in a planar surface.

In some embodiments, the anti-reflective coating film extends from the upper surface of the upper optical cladding layer to the lower surface of the lower optical cladding layer.

In some embodiments, the optical core protrudes outward beyond the outermost sidewall of the upper optical cladding and/or the outermost sidewall of the lower optical cladding.

In some embodiments, the outermost side wall of the upper optical cladding layer and/or the outermost side wall of the lower optical cladding layer protrudes outwardly beyond the outermost side wall of the optical core.

Still other embodiments relate to a method. In the method, a substrate is received. The substrate includes a base substrate, a lower optical cladding layer over the base substrate, and an optical core over the lower optical cladding layer. An upper optical cladding layer is formed on the optical core. An etching process is performed to pattern the upper optical cladding layer, the optical core, the lower optical cladding layer, and the upper surface of the substrate to provide a patterned optical edge coupler having an outer sidewall that has a substantially planar profile and is spaced apart from an outermost edge of the substrate. Wet etching is performed on the patterned optical edge coupler to recess the outer side wall of the optical core relative to the outer side wall of the lower optical cladding layer and the outer side wall of the upper optical cladding layer.

In some embodiments, the performing of the wet etch produces an outer sidewall of the optical core having a plurality of planar facets that intersect at respective intersections, and further comprising: an annealing operation is performed to reflow the material of the optical core to transform the plurality of planar facets into a continuous curved surface between the upper optical cladding layer and the lower optical cladding layer.

The foregoing outlines features of a drop-on embodiment so that those skilled in the art may better understand aspects of the present invention. Those skilled in the art should appreciate that they may readily use the present invention as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the invention.

Claims (10)

1. An integrated circuit, comprising:

a substrate having an upper face and a lower face, the upper face comprising a central region and an outer sidewall laterally surrounding the central region and extending from the upper face to the lower face; and

an optical edge coupler disposed above the upper face of the substrate and extending in a first direction from the central region toward the outer sidewall, wherein the outer sidewall of the optical edge coupler corresponds to the outer sidewall of the substrate and has a concave or convex surface.

2. The integrated circuit of claim 1, wherein the optical edge coupler comprises:

an optical core extending in the first direction over the substrate;

a lower light cladding layer extending in the first direction over the substrate and separating the optical core from the substrate; and

an upper light cladding layer extending in the first direction and disposed over the light core.

3. The integrated circuit of claim 2, wherein an outer sidewall of the optical core protrudes outwardly beyond at least one of an outer sidewall of the upper optical cladding layer or an outer sidewall of the lower optical cladding layer, wherein the outer sidewall of the upper optical cladding layer and the outer sidewall of the lower optical cladding layer are traversed by a plane, and the optical core has a varying thickness as measured perpendicular to the plane from the lower optical cladding layer to the upper optical cladding layer.

4. The integrated circuit of claim 3, wherein the upper optical cladding layer and the lower optical cladding layer comprise silicon dioxide and the optical core comprises silicon or silicon nitride.

5. The integrated circuit of claim 2, wherein an outer sidewall of the upper optical cladding layer or an outer sidewall of the lower optical cladding layer protrudes outwardly beyond an outer sidewall of the optical core, wherein the outer sidewall of the upper optical cladding layer and the outer sidewall of the lower optical cladding layer are traversed by a plane, and the outer sidewall of the optical core is spaced apart from the plane by a varying distance as measured perpendicular to the plane from the lower optical cladding layer to the upper optical cladding layer.

6. The integrated circuit of claim 2, wherein the concave surface or the convex surface is a continuously curved surface extending from the lower optical cladding layer to the upper optical cladding layer.

7. The integrated circuit of claim 2, wherein the concave surface or the convex surface comprises an upper planar facet and a lower planar facet intersecting at a point disposed along a centerline of the optical core, the centerline of the optical core being equally spaced between the upper surface of the optical core and the lower surface of the optical core.

8. The integrated circuit of claim 2, wherein the concave surface or the convex surface comprises an upper planar facet and a lower planar facet intersecting at an intermediate planar facet, the intermediate planar facet disposed along a midline of the optical core, the midline of the optical core being equally spaced between the upper surface of the optical core and the lower surface of the optical core.

9. An optical system, comprising:

an optical transmitter or receiver comprising an optical communication path; and

an integrated circuit, the integrated circuit comprising:

a substrate;

an optical core over the substrate, the optical core having a first refractive index and being aligned with the optical communication path of the optical transmitter or receiver;

a lower optical cladding layer over and separating the substrate from the optical core, the lower optical cladding layer having a second refractive index less than the first refractive index; and

an upper optical cladding layer located above the optical core, the upper optical cladding layer having the second refractive index; and

wherein the optical core has a concave or convex sidewall corresponding to an outer edge of the substrate and aligned with the optical communication path of the optical transmitter or receiver.

10. A method of forming an integrated circuit, comprising:

a receiving substrate comprising a base substrate, a lower optical cladding layer over the base substrate, and an optical core over the lower optical cladding layer;

forming an upper optical cladding over the optical core;

performing an etching process to pattern the upper optical cladding layer, the optical core, the lower optical cladding layer, and the upper surface of the substrate to provide a patterned optical edge coupler having an outer sidewall with a substantially planar profile, and spaced apart from an outermost edge of the substrate; and

wet etching is performed on the patterned optical edge coupler to recess the outer side wall of the optical core relative to the outer side wall of the lower optical cladding layer and the outer side wall of the upper optical cladding layer.