Optical devices and methods of manufacture

Abstract

An optical device and manufacturing method are proposed, wherein a first set of gratings is vertically offset and horizontally offset from a second set of gratings. In some embodiments, the first and second sets of gratings exist in a single grating layer. In some embodiments, the first and second sets of gratings exist in a multilayer grating layer. One or more layers comprising the first and second sets of gratings exist on a cladding layer.

Description

Technical Field

[0001] The embodiments of the present invention relate to an optical device and a method for manufacturing the same. Prior Technology

[0002] Electrical signal transmission and processing is a technology for signal transmission and processing. In recent years, optical signal transmission and processing has been used in an increasing number of applications, especially due to the use of fiber optics for signal transmission.

[0003] Grating couplers provide optical coupling from optical fiber to optical waveguide for use in optical signal transmission and processing systems. Grating couplers are typically designed for unidirectional optical coupling, requiring additional metallic reflectors to improve coupling efficiency. Unidirectional coupling can lead to light leakage, thus reducing coupling efficiency. Unidirectional coupling can also be limited by the polarization selectivity of the grating coupler. Furthermore, the grating coupler can be a source of energy loss, which in turn affects the performance of optical signal transmission and processing systems integrating grating couplers. Summary of the Invention

[0004] In one embodiment, a method of forming an optical device includes: forming a first set of gratings in a grating layer present on a cladding layer; and forming a second set of gratings that are horizontally and vertically offset from the first set of gratings.

[0005] In another embodiment, the optical device includes: a single grating layer having a first set of gratings extending in a first portion of the single grating layer along a first direction and a second set of gratings extending in a second portion of the single grating layer along a second direction, the second portion being horizontally offset from the first portion; and a covering layer in contact with the single grating layer.

[0006] In another embodiment, the optical device includes: a first grating layer existing on the cladding layer and having a plurality of trenches; and a second grating layer existing on the first grating layer and having a first set of gratings on an upper surface of the second grating layer and a second set of gratings on a lower surface of the second grating layer that intersects with the first grating layer, wherein the first set of gratings has a height extending along a first direction, and the second set of gratings extends along a second direction into the plurality of trenches in the first grating layer. Simple Explanation of the Diagram

[0007] The various aspects of this disclosure can be best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be noted that, in accordance with industry standard practice, the features are not drawn to scale. In fact, for clarity of discussion, the dimensions of the features may be arbitrarily increased or decreased. Figure 1 is a side cross-sectional view according to some embodiments, illustrating the intermediaries used in a method for forming a photonic platform. Figure 2 is a side sectional view according to some embodiments, illustrating the processing medium to provide a first optical device. Figure 2A is a side cross-sectional view according to some embodiments, illustrating the grating coupler portion forming a cover to isolate the intermediate and the first insulating layer of the intermediate in the grating coupler portion being removed. Figure 2B is a side cross-sectional view according to some embodiments, illustrating the formation of a mirror layer and a first cladding layer in the grating coupler portion of the intermediate. Figure 2C is a side cross-sectional view according to some embodiments, illustrating the formation of a single grating layer on a first covering layer. Figure 2D is a side cross-sectional view according to some embodiments, illustrating etched trenches into the upper surface of a single grating layer to form a set of gratings. Figure 2E is a top view according to some embodiments, illustrating a grating coupler including a single grating layer. Figure 2F is a side cross-sectional view according to some embodiments, illustrating the varying grating height in the grating array of a grating coupler including a single grating layer. Figure 2G is a side cross-sectional view according to some embodiments, illustrating the varying trench depth in any grating array of a grating coupler including a single grating layer. Figure 2H is a side cross-sectional view according to some embodiments, illustrating the first grating layer on which a multilayer grating structure is formed on the first cladding layer. Figure 2I is a side cross-sectional view according to some embodiments, illustrating a second grating layer on which a multilayer grating structure is formed on a first grating layer. Figure 2J is a side cross-sectional view according to some embodiments, illustrating etched trenches into the upper surface of the second grating layer to form a set of gratings. Figure 2K is a top view according to some embodiments, illustrating a grating coupler including a multilayer grating structure. Figure 2L is a side cross-sectional view according to some embodiments, illustrating the varying trench depth in any grating array of a grating coupler including a multilayer grating structure. Figure 2M is a side cross-sectional view according to some embodiments, illustrating a grating coupler forming a multilayer grating structure including three sets of gratings. Figure 2N is a side cross-sectional view of a grating coupler including three sets of gratings according to some embodiments, the three sets of gratings being configured for optical coupling with TM mode and TE mode having wideband wavelengths. Figure 2O is a side sectional view of a grating coupler including three sets of gratings according to some embodiments, the three sets of gratings being configured for optical coupling with TM mode and TE mode having C / O wavelengths. Figures 3 to 9 are side cross-sectional views according to some embodiments, illustrating the formation of a photonic platform including the grating coupler described in Figures 2A to 2O. Implementation

[0008] The following disclosure provides numerous different embodiments or examples for implementing various features of the provided subject matter. Specific examples of components and arrangements are described below to simplify this disclosure. Of course, these are merely examples and are not intended to be limiting. For example, in the following description, forming a first feature above or on a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features such that the first and second features are not in direct contact. Additionally, reference numerals and / or letters may be repeated in the various examples of this disclosure. Such repetition is for simplicity and clarity and does not in itself define the relationship between the various embodiments and / or configurations discussed.

[0009] Furthermore, for ease of description, this document uses spatial relative terms such as “below,” “under,” “lower,” “above,” and “above” to describe the relationship between one element or feature and another element or feature as shown in the figures. In addition to the orientations shown in the figures, the spatial relative terms are intended to cover different orientations of the device or operation in use. The device may be oriented in other ways (rotated 90 degrees or otherwise) and the spatial relative descriptors used herein can be interpreted accordingly.

[0010] The embodiments will discuss optical devices with respect to some embodiments, wherein at least two sets of gratings, horizontally and vertically offset from each other, are integrated into the grating layer of a grating coupler. In some embodiments, the methods and structures disclosed herein provide single-layer and multi-layer bidirectional grating coupler structures that reduce energy loss and improve coupling efficiency and bandwidth. In some embodiments, the optical device structures described herein are suitable for light sources of different wavelengths. In some embodiments, a multi-layer structure is described that, compared to existing grating couplers, can achieve higher coupling efficiency, wider bandwidth, higher wavelength selectivity, and lower polarization dependence. In some embodiments, the bidirectional grating coupler structures described herein are optical components that, compared to previous optical couplers, enable more efficient optical coupling for fiber-optic related applications of signal transmission.

[0011] However, the embodiments presented herein are intended to be illustrative and are not intended to limit the embodiments to the precise descriptions discussed. Rather, the embodiments discussed can be incorporated into a wide variety of implementations, and all such implementations are fully intended to be included within the scope of the embodiments.

[0012] Referring now to FIG. 1, the initial structure of the optical medium 100 is illustrated. In the specific embodiment shown in FIG. 1, the optical medium 100 is a photonic integrated circuit (PIC) and at this stage includes a first substrate 101, a first insulating layer 103, and a layer of material 105 for a first active layer 201 for a first optical component 203 (not shown separately in FIG. 1, but illustrated in FIG. 2 below and discussed further). In the embodiment, at the initial stage of the manufacturing process of the optical medium 100, the first substrate 101, the first insulating layer 103, and the layer of material 105 for the first active layer 201 for the first optical component 203 may collectively be part of a silicon-on-insulator (SOI) substrate. Referring first to the first substrate 101, the first substrate 101 may be a semiconductor material (e.g., silicon or germanium), a dielectric material (e.g., glass), or any other suitable material that allows for structural support of the overlying components.

[0013] The first insulating layer 103 may be a dielectric layer separating the first substrate 101 from the upper first active layer 201, and additionally, in some embodiments, may be used as part of a covering material surrounding a subsequently fabricated first optical component 203 (discussed further below). In embodiments, the first insulating layer 103 may be silicon oxide, silicon nitride, germanium oxide, germanium nitride, combinations thereof, etc., formed using methods such as implantation (e.g., to form a buried oxide (BOX) layer), or may be deposited onto the first substrate 101 using deposition methods such as chemical vapor deposition, atomic layer deposition, physical vapor deposition, combinations thereof. However, any suitable materials and manufacturing methods may be used.

[0014] The material 105 of the first active layer 201 is initially (before patterning) a conformal layer of material that will be used to begin fabricating the first active layer 201 of the first optical component 203. In embodiments, the material 105 of the first active layer 201 can be a light-transmitting material that can be used as the core material of the desired first optical component 203, such as a semiconductor material, such as silicon, germanium, silicon-germanium, combinations thereof, etc. In other embodiments, the material 105 of the first active layer 201 can be a dielectric material, such as silicon nitride, etc., although in other embodiments, the material 105 of the first active layer 201 can be a III-V group material, lithium niobate material, or a polymer. In embodiments where the material 105 of the first active layer 201 is deposited, methods such as epitaxial growth, chemical vapor deposition, atomic layer deposition, physical vapor deposition, combinations thereof, etc., can be used to deposit the material 105 of the first active layer 201. In other embodiments where the first insulating layer 103 is formed using an implantation method, the material 105 of the first active layer 201 may initially be part of the first substrate 101 before the implantation process to form the first insulating layer 103. However, the material 105 of the first active layer 201 may be formed using any suitable material and manufacturing method.

[0015] Figure 2 illustrates that once the material 105 of the first active layer 201 is ready, the material 105 of the first active layer 201 can be used to fabricate the first optical component 203 of the first active layer 201. In embodiments, the first optical component 203 of the first active layer 201 may include components such as optical waveguides (e.g., ridge waveguides, rib waveguides, buried channel waveguides, diffused waveguides, etc.), directional couplers, optical modulators (e.g., Mach-Zehnder silicon photonic switches, microelectromechanical switches, microring resonators, etc.), amplifiers, multiplexers, demultiplexers, photoelectric converters (e.g., PN junctions), electro-optic converters, lasers, and combinations thereof. However, any suitable first optical component 203 can be used.

[0016] To begin forming the first active layer 201 of the first optical component 203 from initial material, the material 105 of the first active layer 201 can be patterned into the desired shape of the first active layer 201 of the first optical component 203. In embodiments, the material 105 of the first active layer 201 can be patterned using, for example, one or more photolithography masks and etching processes. However, any suitable method for patterning the material 105 of the first active layer 201 can be utilized. For some first optical components 203, the patterning process can be the fabrication used to form all or at least most of these first optical components 203.

[0017] In some embodiments, a portion of the intermediary 100 may be processed to provide a grating coupler 204 (as seen in FIG. 3). The portion of the intermediary 100 processed to provide the grating coupler 204 is hereinafter referred to as the grating coupler portion 205 of the intermediary 100. In some embodiments, to protect the first optical component 203 during the processing for forming the grating coupler 204, the portion of the intermediary 100 in which the first optical component 203 resides is covered by a mask structure. In some embodiments, the mask structure is patterned such that the grating coupler portion 205 of the intermediary 100 is exposed. The mask structure used to protect the first optical component 203 from the process of forming the grating coupler 204 may be a hard mask, a photoresist mask, or a combination of a photoresist mask and a hard mask. The mask structure used to isolate the grating coupler portion 205 of the intermediary may be removed after the grating coupler 204 is completed.

[0018] Figure 2A illustrates one embodiment in which a first mask 206 is formed to protect the first optical component 203 and expose the grating coupler portion 205 of the intermediary 100. After the first mask 206 is formed, an etching process can be used to remove any portions of the first active layer 105 and the first insulating layer 103 that may be present in the grating coupler portion 205 of the intermediary 100. The etching process used at this stage of the process flow can be anisotropic etching, such as reactive ion etching (RIE). In some embodiments, the etching process for removing the first insulating layer 103 may include etching chemicals that are selective to the first substrate 101. After the first insulating layer 103 is removed, the upper surface of the first substrate 101 can be exposed.

[0019] Figures 2B to 2D illustrate an embodiment of a grating coupler portion 205 of the processing medium 100 to form a grating coupler 204 in the grating coupler portion 205 and a second set of gratings 212 extending in a second direction in a second region 209 of the grating coupler portion 205 (see Figure 2C). During the processing of the grating coupler portion 205 shown in Figures 2B to 2D, the remaining portion of the medium 100 including the first optical element 203 may be protected by one or more block masks and / or rigid masks.

[0020] Figure 2B illustrates an embodiment in which a mirror layer 260 is formed on the upper surface of the first substrate 101 present in the grating coupler portion 205. The mirror layer 260 may be composed of a composite material containing metal. For example, the mirror layer 260 may be composed of metals such as gold (Au), silver (Ag), copper (Cu), tin (Sn), aluminum (Al), tungsten (W), tantalum (Ta), platinum (Pt), and alloys thereof. In some embodiments, the formation of the mirror layer 260 may begin with the deposition of a seed layer. For example, the seed layer may include a copper layer. Depending on the desired material, the seed layer may be deposited using processes such as sputtering, evaporation, or plasma-enhanced chemical vapor deposition (PECVD). The mirror layer 260 may then be plated onto the seed layer. The plating metal for the mirror layer 260 may be deposited onto the seed layer using a plating process such as electroplating or electroless plating. It should be noted that the methods and compositions for providing the mirror layer 260 are for illustrative purposes only and are not intended to limit this disclosure to the materials and methods described above. Other compositions and methods for fabricating the mirror layer 260 are also within the scope of this disclosure, provided that the formed mirror layer 260 is a reflective structure. For example, the mirror layer 260 can be formed using a back-side processing at a later point in the process flow (e.g., after the formation of the grating structure). Furthermore, the mirror layer 260 can provide a dispersed Bragg reflector.

[0021] Figure 2B also illustrates the formation of a first cladding layer 103A on the mirror layer 260. The first cladding layer 103A can be composed of an oxide-containing synthetic material (e.g., silicon oxide (SiO2)). The first cladding layer 103A can be deposited using a chemical vapor deposition (CVD) process. Note that chemical vapor deposition (CVD) is only one example of a suitable deposition process for forming the first cladding layer 103A. In other examples, the first cladding layer 103A can be formed using deposition processes such as atomic layer deposition (ALD) or physical vapor deposition (PVD).

[0022] Figure 2B also illustrates an embodiment in which trenches 210 are formed in a first cladding layer 103A present in the grating coupler portion 205 of the intermediary 100. In some embodiments, forming trenches 210 includes forming a first etch mask 207. The first etch mask 207 exposes the entire first cladding layer 103A in a first region 208 of the grating coupler portion 205. The first etch mask 207 also protects portions of the first cladding layer 103A in a second region 209 of the grating coupler portion 205 to form a plurality of trenches 210.

[0023] In some embodiments, the etching process for recessing the first cladding layer 103A in the first region 208 of the grating coupler portion 205 and for forming trenches 210 in the second region 209 of the grating coupler portion 205 can be directional etching, such as reactive ion etching (RIE). The trenches 210 formed in the first cladding layer 103A are then filled with the material of the subsequently formed single grating layer 211. In some embodiments, filling the trenches 210 with the material of the single grating layer 211 provides a second set of gratings 212 (not shown in FIG. 2B, but illustrated in FIG. 2C below). In some embodiments, the trenches 210 can be patterned with a geometry having curvature and tapered width, such that when the material of the single grating layer 211 is filled, a second set of gratings 212 with the geometry shown in the top view of FIG. 2E can be provided.

[0024] Figure 2C illustrates an embodiment in which a single grating layer 211 is formed on a first cladding layer 103A after trench 210 is formed. In the embodiments shown in Figures 2B to 2E, the single grating layer 211 is provided by a material layer deposited using a single deposition step. In some embodiments, the single grating layer 211 may be made of a semiconductor-containing material, such as a silicon-containing material, for example, silicon (Si). In other embodiments, the single grating layer 211 may be made of a dielectric material, such as a nitride-containing material, for example, silicon nitride (Si3N4).

[0025] In some embodiments, a chemical vapor deposition (CVD) process can be used to deposit the single grating layer 211, wherein deposition parameters are selected to fill the trench 210 with at least the material of the single grating layer 211. In one example, the chemical vapor deposition (CVD) process can be plasma-enhanced chemical vapor deposition (PECVD). In other examples, high-density plasma chemical vapor deposition (HDPCVD), atomic layer deposition (ALD), or physical vapor deposition (PVD) can be used to deposit the single grating layer 211.

[0026] As described above, a portion of the material of the single grating layer 211 fills the pre-formed trench 210 in a portion of the first cladding layer 103A. The grating group formed during the process steps is present in the second region 209 of the grating coupler portion 205 of the intermediate 100, and may be referred to hereinafter as the second set of gratings 212.

[0027] Figure 2D illustrates the formation of another set of gratings in the upper surface of the single grating layer 211, the other set of gratings existing in the first region 208 of the grating coupler portion 205 of the intermediate 100. The gratings existing in the first region 208 of the grating coupler portion 205 of the intermediate 100 are hereinafter referred to as the first set of gratings 214. Forming the first set of gratings 214 in the upper surface of the single grating layer 211 may include forming a second etch mask (not shown), the second etch mask being patterned to expose portions of the single grating layer 211 in the first region 208 to be etched to form trenches 213. The second etch mask may be a photoresist mask formed using photolithography. In some embodiments, the etching process used to form the trenches 213 may be an anisotropic etching process, such as reactive ion etching (RIE). After the etching process, the second etch mask may be removed using a chemical stripping or ashing process. The remaining portion of the single grating layer 211 between multiple sets of trenches 213 on the upper surface of the single grating layer 211 provides the first set of gratings 214. The first set of gratings 214 may have a geometry with curvature and tapered width, as shown in the top view of Figure 2E.

[0028] In some embodiments, a first set of gratings 214 in a first region 208 of the grating coupler portion 205 of the intermediary 100 is horizontally offset from a second set of gratings 212 in a second region 209. In some embodiments, the first set of gratings 214 has its maximum width at the end of the grating coupler 204 and gradually tapers to its narrowest width at the junction of the first set of gratings 214 and the second set of gratings 212. The width of the second set of gratings 212 gradually decreases from its widest point at the junction with the first set of gratings 214 to its narrowest width at the junction with the waveguide junction portion 215 of the grating coupler.

[0029] Referring to FIG. 2D, in some embodiments, a first set of gratings 214 exists in the upper surface of the single grating layer 211 and has a height extending along a first direction D1. A second set of gratings 212 exists in the lower surface of the single grating layer 211 and has a height extending along a second direction D2. The first direction D1 of the first set of gratings 214 is opposite to the second direction D2 of the second set of gratings. In some embodiments, the opposing first direction D1 and second direction D2 of the first set of gratings 214 and the second set of gratings 212 provide a bidirectional grating coupler structure.

[0030] The first set of gratings 214, located on the upper surface of the single grating layer 211, is also vertically offset from the second set of gratings 212, located on the lower surface of the single grating layer 211. In some embodiments, the vertical offset between the first set of gratings 214 and the second set of gratings 212 can increase the coupling efficiency of the grating coupler 204. For example, by offsetting the direction and center position of the grating groove, the coupling efficiency can be improved while reducing insertion loss and reflection loss. Furthermore, the offset method can improve the stability and reliability of the grating coupler. In some embodiments, the vertical offset can also reduce the manufacturing cost and complexity of the grating coupler.

[0031] Figure 2E is a top view of a grating coupler 204 comprising a single grating layer with a first set of gratings 214. The first set of gratings 214 may have a geometry containing curvature and tapered width, as shown in the top view of Figure 2E.

[0032] Figure 2F illustrates an embodiment of the grating coupler 204, wherein the height of the gratings in the grating array (e.g., the first set of gratings 214 or the second set of gratings 212) can be varied. In some embodiments, changing the height of the gratings in the grating coupler can reduce losses. For example, changing the height of the gratings in the first set of gratings 214 and / or the second set of gratings 212 can reduce at least one of insertion loss and reflection loss. In some embodiments, by reducing losses, changing the grating height of at least one of the first set of gratings 214 and the second set of gratings 212 can increase the coupling efficiency of the grating coupler.

[0033] Figure 2F illustrates an embodiment of a single grating layer 211 including a first set of gratings 214, which comprises a grating array with varying heights. In some embodiments, the height of the gratings in the grating array increases from edge gratings 216 at the edge of the array to a central grating 217 at approximately the center of the array. In some embodiments, the highest grating in the central portion of the array, such as the central grating 217, may provide a vertex for the grating array.

[0034] In some embodiments, variations in grating height can be provided through a series of photolithography and etching process steps, where different etch masks can be used for gratings of different heights. In other embodiments, the single grating layer 211 can be further processed to provide different etch rates in different regions, corresponding to gratings of different heights. For example, an ion implantation process can increase the etch rate of the implanted portion of the single grating layer 211 compared to the unimplanted portion. In some embodiments, the implant material can alter the chemical properties of the implanted region, which can increase or decrease the etch selectivity of the implanted region of the single grating layer 211 relative to the unimplanted region. In some other embodiments, the implant material can physically damage the implanted region of the single grating layer 211 or introduce porosity into the implanted region of the single grating layer 211, which can increase the etch rate relative to the portion of the single grating layer 211 not damaged by the ion implantation step. The implantation process can be used in conjunction with a photoresist mask to control which portions of the single grating layer 211 are implanted and which portions are not implanted. It is worth noting that the aforementioned patterning and etching methods for forming gratings with different heights in a grating array are provided for illustrative purposes only. Other etching and patterning methods may also be suitable for this stage of the process flow. For example, holographic patterning of a photoresist layer is another masking method that can be used to provide gratings with different grating heights.

[0035] Figure 2G illustrates another embodiment of how the height of the grating in at least one of the first set of gratings 214 and the second set of gratings 212 can be changed. In some embodiments, the height of the grating can be changed by altering the etching depth of the trenches separating the gratings. In some embodiments, the trenches separating the gratings can be referred to as grooves 218. For example, in the embodiment shown in Figure 2G, the first set of gratings 214 includes an array of grooves 218 having a depth that increases from the periphery of the groove array towards the center of the groove array. In one example, the grooves 218 at the periphery of the array can be shallower to provide edge gratings 219 with a low height. In this example, the depth of the grooves 218 increases towards the center of the array. The central grating 220 at the center region of the array can have the maximum height, which is caused by the grooves 218 on the opposite side of the central grating 220 having the maximum depth.

[0036] In some embodiments, variations in the depth of the recesses 218 of the grating can be provided through a series of photolithography and etching process steps, wherein different etching masks can be used for different etching depths of the recesses 218. In some embodiments, the single grating layer 211 can be further processed to provide different etching rates in different regions, which would correspond to recesses with different depths. For example, an ion implantation process can increase the etching rate of the implanted portion of the single grating layer 211 compared to the unimplanted portion. In some embodiments, the implant material can alter the chemical properties of the implanted region, which can increase or decrease the etching selectivity of the implanted region of the single grating layer 211 relative to the unimplanted region. In some other embodiments, the implant material can physically damage the implanted region of the single grating layer 211 or introduce porosity into the implanted region of the single grating layer 211, which can increase the etching rate relative to the portion of the single grating layer 211 not damaged by the ion implantation step. The implantation process can be used in conjunction with a photoresist mask to control which portions of the single grating layer 211 are implanted and which portions are not implanted.

[0037] It is worth noting that the aforementioned patterning and etching methods for forming grooves 218 of different depths in a grating array are provided for illustrative purposes only. Other etching and patterning methods may also be suitable for this stage of the process flow. For example, holographic patterning of a photoresist layer is another masking method that can be used to provide grooves 218 of different depths.

[0038] The grating coupler designs shown in Figures 2D to 2G may further include a second cladding layer (not shown) formed on the surface of a single grating layer 211 (which may be the upper surface of the single grating layer 211), the single grating layer 211 including a first set of gratings 214. In some embodiments, the second cladding layer may be composed of a cladding material (such as silicon oxide, silicon nitride, germanium oxide, germanium nitride, combinations thereof, etc.) formed using deposition methods such as chemical vapor deposition, atomic layer deposition, physical vapor deposition, etc.

[0039] Figures 2H to 2L illustrate another embodiment of a grating coupler portion 205 of a processing medium 100 to form a grating coupler including a multilayer grating structure on top of a first substrate 101. The multilayer grating structure includes a first grating layer 221 having multiple grooves and a second grating layer 223 present on the first grating layer 221. As can be seen in Figure 2J, the second grating layer 223 has a first set of gratings 214 on its upper surface. The second grating layer 223 also includes a second set of gratings 212 on its lower surface, which intersects with the first grating layer 221. In some embodiments, the first set of gratings 214 has a height extending along a first direction D1, while the second set of gratings 212 extends along a second direction D2. The second set of gratings 212 extends from the lower surface of the second grating layer 223 into multiple trenches of the first grating layer 221 (see Figure 2J). During the processing of the grating coupler portion 205 shown in Figures 2H to 2L, the remainder of the intermediary 100, including the first optical component 203, may be protected by one or more block veils and / or rigid veils.

[0040] Figure 2H illustrates the formation of a mirror layer 260 on the exposed surface of the first substrate 101, and the formation of a first cladding layer 103A on the mirror layer 260. The exposed surface of the first substrate 101 in the grating coupler portion 205 of the intermediary 100 on which the mirror layer 260 is formed has been described above with reference to Figure 2A. The formation of the mirror layer 260 has also been described above with reference to Figure 2B. Referring to Figure 2H, the first cladding layer 103A is formed on top of the mirror layer 260. The first cladding layer 103A can be an oxide, such as silicon oxide, and can be deposited using a chemical vapor deposition (CVD) method. Other deposition methods suitable for forming the first cladding layer 103A may include atomic layer deposition (ALD) and physical vapor deposition (PVD). In some embodiments, a planarization process, such as chemical mechanical planarization, may be performed on the upper surface of the first cladding layer 103A.

[0041] Figure 2H also illustrates the formation of a first grating layer 221 on the first cladding layer 103A. In some embodiments, the first grating layer 221 may be made of a semiconductor-containing material, such as silicon (Si). In some embodiments, the first grating layer 221 may be made of a nitride-containing material, such as silicon nitride (Si3N4). In some embodiments, the first grating layer 221 is patterned and etched to provide a plurality of trenches 222 etched into the upper surface of the first grating layer 221.

[0042] In some embodiments, a plurality of trenches 222 are formed in portions of the first grating layer 221 existing in the second region 209 of the grating coupler portion 205 of the interposer 100. In some embodiments, a block mask, such as a photoresist mask or a hard mask, may be formed to expose the second region 209 of the grating coupler portion 205 while protecting the first region 208 of the grating coupler portion 205. The plurality of trenches 222 can then be formed using an etching process such as reactive ion etching (RIE) in combination with the block mask.

[0043] Multiple trenches 222 are filled with subsequently deposited material to form a second grating layer 223 (as seen in FIG. 2I). The multiple trenches 222 filled in the first grating layer 221 will provide a second set of gratings 212 in the second region 209 of the grating coupler portion 205 of the intermediary 100. Thus, in some embodiments, the multiple trenches 222 may be patterned to have a geometry containing curvature and tapered width, such that when the material filling the second grating layer 223 is used, a second set of gratings 212 with the geometry shown in the top view of FIG. 2K can be provided.

[0044] After etching to form multiple trenches 222, at least the portion of the block mask patterned to provide multiple trenches 222 can be removed. However, while forming the multilayer grating structure, the mask structure can be retained or formed to protect the portion of the intermediate 100 other than the grating coupler portion 205 of the intermediate 100.

[0045] Figure 2I illustrates an embodiment in which a material layer is deposited on a first grating layer 221 to form a second grating layer 223. In some embodiments, the second grating layer 223 may be made of a semiconductor-containing material, such as a silicon-containing material, for example, silicon. In some embodiments, the second grating layer 223 may be made of a dielectric material, such as a nitride-containing material, for example, silicon nitride. The second grating layer 223 may be deposited using a chemical vapor deposition (CVD) process, wherein deposition parameters are selected to at least fill the trench 222. In one example, the chemical vapor deposition (CVD) process may be plasma-enhanced chemical vapor deposition (PECVD). The material of the second grating layer 223 filling the trench 222 provides a second set of gratings 212 present in a second region 209 of the grating coupler portion 205 of the intermediary 100.

[0046] Figure 2J illustrates the formation of another set of gratings in the upper surface of the second grating layer 223, which is located in the first region 208 of the coupler portion 205 of the intermediate 100. The gratings formed in the first region 208 of the grating coupler portion 205 in the upper surface of the second grating layer 223 can be referred to as the first set of gratings 214. Forming the first set of gratings 214 in the upper surface of the second grating layer 223 may include forming an etch mask (not shown) in the first region 208, the etch mask being patterned to expose portions of the second grating layer 223 to be etched to form trenches 224. The etch mask may be a photoresist mask formed using photolithography. The trenches 224 may be formed using an etching process. For example, the etching process used to form the trenches 224 may be an anisotropic etching process, such as reactive ion etching (RIE). After the etching process, the etch mask may be removed using a chemical stripping process. The first set of gratings 214 may have a geometry containing the curvature and tapered width shown in the top view of Figure 2K.

[0047] Referring to Figures 2J and 2K, in some embodiments, portions of the first set of gratings 214 in the first region 208 and portions of the second set of gratings 212 in the second region 209 may overlap at the junction of the first region 208 and the second region 209. In some embodiments, at least a first edge grating in the first set of gratings and at least a second edge grating in the second set of gratings horizontally overlap at approximately the middle portion of the grating coupler. The overlapping edge gratings 216 in the first set of gratings 214 and the second set of gratings 212 can combine the advantages of broadband gratings and high coupling efficiency gratings.

[0048] Figure 2K illustrates a top view of the formation of a multilayer grating coupler structure as described with reference to Figures 2H to 2J. A first set of gratings 214 in a first region 208 of the grating coupler portion 205 of the intermediary 100 is horizontally offset from a second set of gratings 212 in a second region 209. In some embodiments, the first set of gratings 214 has its maximum width at the end of the grating coupler 204 and gradually tapers to its narrowest width at the junction of the first set of gratings 214 and the second set of gratings 212. The width of the second set of gratings 212 gradually decreases from its widest point at the junction with the first set of gratings 214 to its narrowest width at the junction with the waveguide junction 215.

[0049] Referring to Figure 2J, in some embodiments, the multilayer grating coupler structure includes a first set of gratings 214, which exists in the upper surface of the second grating layer 223 and has a height extending along a first direction D1. A second set of gratings 212 exists in the lower surface of the second grating layer 223 and has a height extending along a second direction D2. The second set of gratings 212 extends from the second grating layer 223 into a trench formed in the first grating layer 221. The first direction D1 of the first set of gratings 214 is opposite to the second direction D2 of the second set of gratings 212. In some embodiments, the opposing first direction D1 and second direction D2 of the first set of gratings 214 and the second set of gratings 212 provide a bidirectional multilayer grating coupler structure. The first set of gratings 214 in the upper surface of the second grating layer 223 is also perpendicularly offset from the second set of gratings 212 in the lower surface of the second grating layer 223. In some embodiments, the perpendicular offset between the first set of gratings 214 and the second set of gratings 212 can improve the coupling efficiency of the grating coupler. For example, by shifting the direction and center position of the grating groove, coupling efficiency can be improved while reducing insertion loss and reflection loss.

[0050] In some embodiments, the multi-layer architecture of the grating coupling structure, as shown in Figures 2H to 2K, combined with the edge gratings 216 overlapping in the middle of the array, can effectively combine broadband gratings with high coupling efficiency gratings. High coupling efficiency gratings include gratings with smaller spacing between adjacent gratings than broadband gratings.

[0051] In some embodiments, multilayer grating couplers can reduce energy loss and improve optical coupling efficiency. In some embodiments, multilayer grating couplers can enhance bandwidth efficiency. Multilayer grating couplers are suitable for light sources of different wavelengths. Furthermore, multilayer grating couplers can achieve higher optical coupling efficiency and wider bandwidth, while also achieving high wavelength selectivity and lower polarization dependence.

[0052] Figure 2L illustrates an embodiment of a multilayer grating coupler structure incorporating a low-loss design. In the embodiment shown in Figure 2L, the grating structure is a multilayer structure, as described with reference to Figures 2H to 2K. However, in the embodiment shown in Figure 2L, the grating height of the grating array providing the first set of gratings 214 and the second set of gratings 212 has been changed, similar to the way the grating height was changed in the embodiment described above with reference to Figure 2G. By providing different heights, more light energy and a wider range of different wavelengths of light can be coupled.

[0053] Referring to FIG. 2L, in some embodiments, the height of the gratings in the first set of gratings 214 can be varied by changing the etching depth of the trenches 224 formed in the upper surface of the second grating layer 223 to separate the gratings. In some embodiments, the trenches 224 separating the gratings may be referred to as grooves. For example, in the embodiment shown in FIG. 2G, the first set of gratings 214 includes an array of grooves having a depth that increases from the periphery of the array to the center of the array. In one example, the groove depth at the periphery of the array may be shallower to provide edge gratings 219 with a low height. In this example, the groove depth increases towards the center of the array. The central grating 220 in the central region of the array may have the maximum height, which is generated by the grooves with the maximum depth on the opposite side of the central grating 220.

[0054] In some embodiments, variations in the depth of the trenches 224 or recesses separating the grating can be provided through a series of photolithography and etching process steps, wherein different etching masks can be used for recesses of different etching depths on the upper surface of the second grating layer 223. In some embodiments, the second grating layer 223 can be further processed to provide different etching rates in different regions, which would correspond to recesses of different depths. For example, an ion implantation process can increase the etching rate of the implanted portion of the second grating layer 223 compared to the unimplanted portion. In some embodiments, the implant material can alter the chemical properties of the implanted region, which can increase or decrease the etching selectivity of the implanted region of the second grating layer 223 relative to the unimplanted region. In some other embodiments, the implant material can physically damage the implanted region of the second grating layer 223 or introduce porosity into the implanted region of the second grating layer 223, which can increase the etching rate relative to the portion of the second grating layer 223 not damaged by the ion implantation step. The implantation process can be used in conjunction with a photoresist mask to control which portions of the second grating layer 223 are implanted and which portions are not implanted.

[0055] For example, in some embodiments, the height of the gratings in the second set of gratings 212 can be varied by changing the etching depth of the trenches 222 formed in the upper surface of the first grating layer 221. The second set of gratings 212 extends from the lower surface of the second grating layer 223 and fills the trenches 222 formed in the upper surface of the first grating layer 221. For example, in the embodiment shown in FIG. 2L, the second set of gratings 212 includes a grating array having a height that increases from the periphery of the grating array towards the center of the grating array. In one example, the height of the gratings at the periphery of the array can be shallower to provide edge gratings 219 with a low height. In this example, the height of the gratings increases towards the center of the array. For an array providing the second set of gratings 212, the central grating 220 located at the center of the array can have the maximum height.

[0056] In some embodiments, variations in the depth of trench 222 can be provided through a series of photolithography and etching process steps, wherein different etch masks can be used to form trenches 222 of different etch depths in the upper surface of the first grating layer 221. In some embodiments, the first grating layer 221 can be further processed to provide different etch rates in different regions, which would correspond to trenches 222 of different depths. For example, an ion implantation process can increase the etch rate of the implanted portion of the first grating layer 221 compared to the unimplanted portion. In some embodiments, the implant material can alter the chemical properties of the implanted region, which can increase or decrease the etch selectivity of the implanted region of the first grating layer 221 relative to the unimplanted region. In some other embodiments, the implant material can physically damage the implanted region of the first grating layer 221 or introduce porosity into the implanted region of the first grating layer 221, which can increase the etch rate relative to the portion of the first grating layer 221 not damaged by the ion implantation step. The implantation process can be used in conjunction with a photoresist mask to control which portions of the first grating layer 221 are implanted and which portions are not implanted.

[0057] It should be noted that the methods described above for providing gratings with different heights are provided for illustrative purposes and are not intended to be limiting. Other etching and patterning methods may also be suitable for this stage of the process flow. For example, holographic patterning of photoresist layers is another masking method that can be used to provide gratings with different trench depths.

[0058] The architecture shown in Figure 2L is suitable for light sources of different wavelengths. In some embodiments, the grating structure architecture of the grating coupler shown in Figure 2L is a low-loss design. The grating of the embodiment shown in Figure 2L, i.e., the diffraction grating, can be designed for different wavelengths. For example, the height of the grating and the spacing between adjacent gratings can be modified to be compatible with light of different wavelengths. In some embodiments, by providing a first set of gratings 214 and a second set of gratings 212 with a grating array having varying grating heights and vertices located at the center of the array, the grating structure can be used with different wavelengths. Overlapping portions can be defined as vertices, resulting in a wider wavelength range for the overall grating structure.

[0059] Figure 2M illustrates another embodiment of this disclosure. The architecture shown in Figure 2M is similar to the embodiment shown above with reference to Figure 2L. The architecture shown in Figure 2M further introduces a third set of gratings 225. The third set of gratings 225 may be a grating group with a broadband design, which can be used in conjunction with the first set of gratings 214 and the second set of gratings 212 that provide low-loss coupling, as described above with reference to Figure 2L. The third set of gratings may be referred to as a broadband grating and is present at the junction of the first grating layer 221 and the first cladding layer 103A.

[0060] In some embodiments, the gratings can be provided with different periods; for example, the gratings can have different intervals separating adjacent gratings. Gratings with different periods can be used for ultra-wide bandwidths, such as bandwidths greater than 100 nm, and higher wavelength selectivity. In some embodiments, a third set of gratings 225 can be formed at the junction of the first grating layer 221 and the first cladding layer 103A. In some embodiments, to provide a third set of gratings for coupling with wide bandgap light waves, the first cladding layer 103A can be patterned and etched to provide a trench 226 before forming the first grating layer 221. The trench 226 is then filled with the material of the first grating layer 221 to provide the gratings for the third set of gratings 225. Therefore, the trench 226 should be patterned and etched according to the geometry of the grating, which can have curvature. Furthermore, the plurality of gratings in the third set of gratings 225 can be arranged with a tapered width adjacent to the narrowest portion of the waveguide. In order to provide coupling with wide bandgap light, the width of the trench 226 for providing the third set of gratings 225 is greater than the width of the trench defining the first set of gratings 214 and the second set of gratings 212.

[0061] In some embodiments, forming trench 226 in the first cladding layer 103A includes forming an etch mask (not shown). The etch mask is patterned such that a subsequent etching process will recess exposed portions of the first cladding layer 103A to form trench 226. In some embodiments, the etching process for forming trench 226 may be a directional etching process, such as reactive ion etching (RIE). The trench 226 formed in the first cladding layer 103A is then filled with material from a subsequently formed first grating layer 221 to provide a third set of gratings 225, which may be configured as broadband gratings. Thus, in some examples, trench 226 is patterned and etched to provide different periods. In some examples, different periods can be provided by spacing adjacent trenches 226 at different sizes to achieve ultrawide bandwidth and higher wavelength selectivity for the gratings formed therein. For example, the spacing between adjacent gratings in a broadband configuration of the third set of gratings 225 can range from 20 nm to 1000 nm.

[0062] After etching trench 226, a first grating layer 221 is deposited, wherein at least a portion of the material of the first grating layer 221 fills trench 226. In some embodiments, the first grating layer 221 may be made of a semiconductor-containing material, such as a silicon-containing material, or the first grating layer 221 may be made of a dielectric material, such as a nitride-containing material, such as silicon nitride. A chemical vapor deposition (CVD) process can be used to deposit the first grating layer 221, wherein deposition parameters are selected to at least fill trench 226 with the material of the first grating layer 221. In one example, the chemical vapor deposition (CVD) process may be plasma-enhanced chemical vapor deposition (PECVD).

[0063] By filling the trench 226, the first grating layer 221 forms a third set of gratings 225, such as a set of broadband gratings, extending into the first cladding layer 103A along direction D3. The gratings in the broadband third set of gratings 225 exist in both the first region 208 and the second region 209 of the grating coupler portion 205 of the intermediary 100.

[0064] The multilayer grating structure shown in Figure 2M also includes a second grating layer 223, a first set of gratings 214, and a second set of gratings 212. The first set of gratings 214 and the second set of gratings 212 can be configured to provide a low-loss grating design to work in conjunction with a third set of gratings 225 configured for a broadband design. Further details regarding the composition, geometry, and methods of forming the second grating layer 223, the first set of gratings 214, and the second set of gratings 212 have been provided above with reference to Figures 2I to 2L.

[0065] In some embodiments, the multilayer grating structure shown in FIG2M includes a third set of gratings 225, a first set of gratings 214 and a second set of gratings 212, which can provide diffraction gratings of different wavelengths and / or diffraction gratings with different periods to achieve ultra-wide bandwidth (e.g., bandwidth greater than 100 nm) and higher wavelength selectivity.

[0066] Figure 2N illustrates one embodiment of a grating coupler comprising three sets of gratings configured to couple with TM and TE mode light having broadband wavelengths. Figure 2N illustrates how the grating periods of the first set of gratings 214, the second set of gratings 212, and the third set of gratings 225 can be varied to accommodate different polarizations. The grating structure shown in Figure 2N is similar to the grating structure shown above with reference to Figure 2M. However, the gratings in the grating coupler structure shown in Figure 2N include gratings configured to be compatible with light sources with different polarizations. For example, by varying the grating periods, such as by changing the spacing separating adjacent gratings, the grating structure can be adapted to couple different light wavelengths. Furthermore, by combining different layers with different grating parameters, a grating coupler can be provided that can simultaneously couple transverse electric (TE) mode and transverse magnetic (TM) mode light into adjacent waveguides, resulting in a lower polarization dependence of the grating coupler.

[0067] TE mode light is a transverse electromagnetic wave, sometimes also called an H-wave, characterized by its electric vector (E) always being perpendicular to the direction of propagation. TM mode light is a transverse magnetic wave, also called an E-wave. A transverse magnetic wave is characterized by its magnetic vector (H-vector) always being perpendicular to the direction of propagation.

[0068] Figure 2N illustrates one embodiment of a grating coupler 204, suitable for coupling with TE / TM light and broadband optical waves. The grating coupler shown in Figure 2N includes a first set of gratings 214 extending along a first direction D1 and a second set of gratings 212 extending along a second direction D2. The first set of gratings 214 and the second set of gratings 212 exist on the upper and lower surfaces of a second grating layer 223 and are therefore perpendicularly offset from each other. The first set of gratings 214 comprises a grating array with different heights and is suitable for coupling with TE and TM modes of light with C-band and O-band wavelengths. The C-band wavelength can be in the range of 1420 nm to 1620 nm. The O-band wavelength can be in the range of 1260 nm to 1360 nm.

[0069] The grating coupler 204 shown in Figure 2N also includes a third set of gratings 225 configured for coupling with wide bandgap light. Extending from the lower surface of the first grating layer 221, the third set of gratings 225 is suitable for coupling with TE and TM modes of light with wavelengths of ±50 nm in the C and O bands. The spacing P1 separating the gratings in the third set of gratings 225 of the grating coupler 204 shown in Figure 2N can range from 20 nm to 1000 nm.

[0070] Figure 20 illustrates another embodiment of the grating coupler 204, which includes three sets of gratings configured for coupling with TM and TE mode light having C / O wavelengths. Figure 20 also illustrates another embodiment where the grating periods of the first set of gratings 214, the second set of gratings 212, and the third set of gratings 225 can be varied to be compatible with different polarizations.

[0071] The grating coupler shown in Figure 20 includes a first set of gratings 214 extending along a first direction D1 and a second set of gratings 212 extending along a second direction D2. The first set of gratings 214 and the second set of gratings 212 exist on the upper and lower surfaces of the second grating layer 223 and are therefore perpendicularly offset from each other. The first set of gratings 214 includes a grating array of trenches of different depths separating the gratings and is suitable for coupling with the TE mode of light in the C and O band wavelengths.

[0072] The grating coupler shown in Figure 20 also includes a third set of gratings 225 extending from the lower surface of the first grating layer 221, which is suitable for optical coupling with TM modes in the C and O band wavelengths. The spacing P2 separating the gratings in the third set of gratings 225 of the grating coupler shown in Figure 20 can range from 20 nm to 1000 nm.

[0073] Figures 3 through 9 illustrate the formation of an optical package incorporating the grating coupler as described above with reference to Figures 2A through 2O. Each of the embodiments described in Figures 2A through 2O can be integrated into the optical package described with reference to Figures 3 through 9. For simplicity, the different embodiments of the grating coupler shown in Figures 2A through 2O can be commonly represented by the structure with reference numeral 204 in Figures 3 through 9. In some embodiments, any masking structure, such as a hard mask and / or photoresist mask, used to isolate the grating coupler portion 205 of the intermediary 100 may be removed during the formation of the grating coupler 204 prior to the process of integrating the grating coupler 204 into the optical package.

[0074] Figure 3 illustrates that for those components utilizing further fabrication processes, such as Mach-Zehnder silicon photonic switches employing resistance heating elements, additional processing can be performed before or after patterning the material of the first active layer 201 to form the first optical component, and / or before or after forming the grating coupler 204. For example, implantation processes, additional deposition and patterning processes for different materials (e.g., resistance heating elements, III-V materials for converters), combinations of all these processes, etc., can be used to facilitate the further fabrication of various desired first optical components 203. In certain embodiments, and as specifically illustrated in Figure 3, in some embodiments, epitaxial deposition of semiconductor material 301, such as germanium (e.g., for electro / optical signal modulation and conversion), can be performed on the patterned portions of the material 105 of the first active layer 201. In such embodiments, semiconductor material 301 can be epitaxially grown to facilitate the fabrication, for example, photodiodes for photoelectric converters. All such fabrication processes and all suitable first optical components 203 can be fabricated, and all such combinations are fully intended to be included within the scope of the embodiments.

[0075] Figure 4 illustrates that once the grating coupler 204 and the first optical component 203 are formed, a second insulating layer 401 can be deposited to cover the grating coupler 204 and the first optical component 203. The second insulating layer 401 can provide additional covering material. In an embodiment, the second insulating layer 401 can be a dielectric layer that separates the individual components of the first active layer 201 from each other and from the structure above, and can also serve as another part of the covering material surrounding the first optical component 203 and the grating coupler 204. In an embodiment, the second insulating layer 401 can be silicon oxide, silicon nitride, germanium oxide, germanium nitride, etc., formed using deposition methods such as chemical vapor deposition, atomic layer deposition, physical vapor deposition, combinations thereof, etc. Once the material of the second insulating layer 401 has been deposited, it can be planarized using, for example, a chemical mechanical polishing process, to planarize the top surface of the second insulating layer 401 (in embodiments where the second insulating layer 401 is intended to completely cover the first optical component 203 and the grating coupler 204) or to planarize the second insulating layer 401 together with the top surfaces of the first optical component 203 and the grating coupler 204. However, any suitable material and manufacturing method can be used.

[0076] Figure 5 illustrates that once the first optical component 203 and the grating coupler 204 are fabricated and the second insulating layer 401 is formed, a first metallization layer 501 is formed to electrically connect the first active layer 201 of the first optical component 203 and the grating coupler 204 to a control circuit, to each other, and to subsequently attached devices (not shown in Figure 5, but further illustrated and described in Figure 6 below). In embodiments, the first metallization layer 501 is formed of alternating layers of dielectric and conductive materials and can be formed by any suitable process (e.g., deposition, damascene, dual damascene, etc.). In certain embodiments, there may be multiple metallization layers for interconnecting the various first optical components 203 and the grating coupler 204, but the exact number of first metallization layers 501 depends on the design of the optical medium 100.

[0077] Additionally, during the fabrication of the first metallization layer 501, one or more second optical components 503 may be formed as part of the first metallization layer 501. In some embodiments, the second optical components 503 of the first metallization layer 501 may include components such as couplers (e.g., edge couplers, grating couplers, etc.) for connecting to external signals, optical waveguides (e.g., ridge waveguides, rib waveguides, buried channel waveguides, diffused waveguides, etc.), optical modulators (e.g., Mach-Zehnder silicon photonic switches, microelectromechanical switches, microring resonators, etc.), amplifiers, multiplexers, demultiplexers, photoelectric converters (e.g., PN junctions), electro-optic converters, lasers, and combinations thereof. However, any suitable optical component may be used for one or more second optical components 503.

[0078] In an embodiment, one or more second optical components 503 can be formed by first depositing a material for one or more second optical components 503. In an embodiment, the material for one or more second optical components 503 can be a dielectric material (e.g., silicon nitride, silicon oxide, combinations thereof), or a semiconductor material (e.g., silicon), deposited using deposition methods such as chemical vapor deposition, atomic layer deposition, physical vapor deposition, combinations thereof. However, any suitable material and any suitable deposition method can be used.

[0079] Once the material of one or more second optical components 503 has been deposited or otherwise formed, the material can be patterned into the desired shape of the one or more second optical components 503. In embodiments, the material of one or more second optical components 503 can be patterned using, for example, one or more photolithographic masks and etching processes. However, any suitable method for patterning material into one or more second optical components 503 can be utilized.

[0080] For some of the one or more second optical components 503, such as waveguides or edge couplers, the patterning process can be used to fabricate all or at least most of these components. Additionally, for those components utilizing further fabrication processes, such as Mach-Zehnder silicon photonic switches using resistance heating elements, additional processing can be performed before or after patterning the material into one or more second optical components 503. For example, implantation processes, additional deposition and patterning processes for different materials, combinations of all these processes, etc., can be used to facilitate the further fabrication of various desired one or more second optical components 503. All such fabrication processes and all suitable one or more second optical components 503 can be fabricated, and all such combinations are fully intended to be included within the scope of the embodiments.

[0081] Once one or more second optical components 503 in the first metallization layer 501 have been fabricated, a first bonding layer 505 is formed over the first metallization layer 501. In embodiments, the first bonding layer 505 can be used for dielectric-to-dielectric and metal-to-metal bonding. According to some embodiments, the first bonding layer 505 is formed of a first dielectric material 509 such as silicon oxide, silicon nitride, etc. Any suitable method can be used to deposit the first dielectric material 509, such as CVD, high-density plasma chemical vapor deposition (HDPCVD), PVD, atomic layer deposition (ALD), etc. However, any suitable material and deposition process can be utilized.

[0082] Once the first dielectric material 509 is formed, a first opening is formed in the first dielectric material 509 to expose the underlying conductive portion, preparing for the formation of a first bonding pad 507 within the first bonding layer 505. Once the first opening is formed within the first dielectric material 509, it can be filled with a seed layer and plated metal to form the first bonding pad 507 within the first dielectric material 509. The seed layer can be deposited over the entire surface of the first dielectric material 509 and the exposed conductive portion of the underlying layer, as well as over the sidewalls of the opening and the second opening. The seed layer may include a copper layer. Depending on the desired material, the seed layer can be deposited using processes such as sputtering, vapor deposition, or plasma-enhanced chemical vapor deposition (PECVD). Plated metal can be deposited on the seed layer using a plating process such as electroplating or electroless plating. The plated metal may include copper, copper alloys, etc. The plated metal may be a filler material. A barrier layer (not shown separately) can be deposited over the entire surface of the first dielectric material 509 and over the sidewalls of the opening and the second opening before the seed layer. The barrier layer may contain titanium, titanium nitride, tantalum, tantalum nitride, etc.

[0083] After filling the first opening, a planarization process, such as CMP, is performed to remove the seed layer and excess metal plating, thereby forming a first bonding pad 507 within the first bonding layer 505. In some embodiments, bonding pad vias (not shown separately) may also be used to connect the first bonding pad 507 to an underlying conductive portion, and the first bonding pad 507 to the first metallization layer 501 may be connected through the underlying conductive portion.

[0084] Additionally, the first bonding layer 505 may also include one or more third optical components 511 integrated within the first bonding layer 505. In such embodiments, the one or more third optical components 511 may be fabricated using methods and materials similar to those used for the one or more second optical components 503 (as described above), such as waveguides and other structures formed at least partially by deposition and patterning processes, prior to the deposition of the first dielectric material 509. However, any suitable structural material and any suitable manufacturing method may be utilized.

[0085] Figure 6 illustrates the bonding of a first semiconductor element 601 to a first bonding layer 505 of an optical medium 100. In some embodiments, the first semiconductor element 601 is an electronic integrated circuit (EIC, e.g., an element without optical components) and may have a semiconductor substrate 603, an active element 605, an overlay interconnect structure 607, a second bonding layer 609, and an associated third bonding pad 611. In embodiments, the semiconductor substrate 603 may be similar to the first substrate 101 (e.g., a semiconductor material, such as silicon or silicon-germanium), the active element 605 may be a transistor, capacitor, resistor, etc., formed over the semiconductor substrate 603, the overlay interconnect structure 607 may be similar to the first metallization layer 501 (without optical components), the second bonding layer 609 may be similar to the first bonding layer 505, and the third bonding pad 611 may be similar to the first bonding pad 507. However, any suitable element may be used.

[0086] In this embodiment, the first semiconductor element 601 may be configured to work in conjunction with the optical medium 100 to achieve the desired functionality. In some embodiments, the first semiconductor element 601 may be a high-bandwidth memory (HBM) module, xPU, logic die, 3DIC die, CPU, GPU, SoC die, MEMS die, or a combination thereof. Any suitable element with any appropriate functionality may be used, and all such elements are fully intended to be included within the scope of this embodiment.

[0087] In embodiments, the first semiconductor element 601 and the first bonding layer 505 can be bonded using dielectric-to-dielectric and metal-to-metal bonding processes. In specific embodiments using dielectric-to-dielectric and metal-to-metal bonding processes, the process can be initiated by activating the surfaces of the second bonding layer 609 and the first bonding layer 505. Activating the top surfaces of the first bonding layer 505 and the second bonding layer 609 can include dry processing, wet processing, plasma processing, exposure to inert gas plasma, exposure to H2, exposure to N2, exposure to O2, and combinations thereof, as examples. In embodiments using wet processing, for example, RCA cleaning can be used. In another embodiment, the activation process can include other types of processing. The activation process facilitates the bonding of the first bonding layer 505 and the second bonding layer 609.

[0088] Following the activation process, the optical medium 100 and the first semiconductor element 601 can be cleaned using, for example, chemical rinsing. The first semiconductor element 601 is then aligned and positioned to make physical contact with the optical medium 100. The optical medium 100 and the first semiconductor element 601 are then subjected to heat treatment and contact pressure to bond them. For example, the optical medium 100 and the first semiconductor element 601 can be subjected to pressures of about 200 kPa or less and temperatures between about 25°C and about 250°C to fuse them. The optical medium 100 and the first semiconductor element 601 can then be subjected to temperatures at or above the eutectic point of the materials of the first bonding pad 507 and the third bonding pad 611, for example, about 150°C to about 650°C, to melt the metal. In this way, the optical medium 100 and the first semiconductor element 601 form dielectric-to-dielectric and metal-to-metal bonding elements. In some embodiments, the bonded grains are subsequently baked, annealed, pressed, or otherwise treated to strengthen or complete the bond.

[0089] Furthermore, while specific processes for initiating and enhancing bonding have been described, these descriptions are illustrative and not intended to limit the embodiments. Rather, any suitable combination or combination of processes, such as baking, annealing, and pressing, can be utilized. All such processes are fully encompassed within the scope of the embodiments.

[0090] Figure 6 further illustrates that once the first semiconductor element 601 is bonded, a second gap-filling material 613 is deposited to fill the space around the first semiconductor element 601 and provide additional support. In an embodiment, the second gap-filling material 613 may be a material such as silicon oxide, silicon nitride, silicon oxynitride, or combinations thereof, deposited to fill and overfill the space around the first semiconductor element 601. However, any suitable material and deposition method may be used.

[0091] Once the second gap filler material 613 has been deposited, it can be planarized to expose the first semiconductor device 601. In embodiments, the planarization process can be a chemical mechanical planarization process, a polishing process, etc. However, any suitable planarization process can be used.

[0092] Figure 7 illustrates a support substrate 701 attached to a first semiconductor element 601 and a second gap filler material 613. In one embodiment, the support substrate 701 may be a support material transparent to the wavelength of the light to be used, such as silicon, and may be attached using, for example, an adhesive layer (not shown separately in Figure 7). However, in other embodiments, the support substrate 701 may be bonded to the first semiconductor element 601 and the second gap filler material 613 using, for example, a bonding process. Any suitable method for attaching the support substrate 701 may be used.

[0093] Figure 7 also illustrates a support substrate 701 including a coupling lens 703, positioned to facilitate movement from the optical fiber 905 (not shown in Figure 7, but further illustrated and described below with respect to Figure 9) to the grating coupler 204, the second optical component 503, or the third optical component 511 of the first metallization layer 501. In an embodiment, the coupling lens 703 can be formed by shaping the material of the support substrate (e.g., silicon) using a masking and etching process. However, any suitable process can be utilized.

[0094] Figure 8 illustrates the removal of the first substrate 101 and the optional first insulating layer 103, thereby exposing the first active layer 201 of the first optical component 203 and the grating coupler 204. In embodiments, the first substrate 101 and the first insulating layer 103 can be removed using planarization processes, such as chemical mechanical polishing, grinding, one or more etching processes, combinations of these processes, etc. However, any suitable method can be used to remove the first substrate 101 and / or the first insulating layer 103.

[0095] Once the first substrate 101 and the first insulating layer 103 are removed, a second active layer 801 of the fourth optical component 803 can be formed on the back side of the first active layer 201. In an embodiment, the second active layer 801 of the fourth optical component 803 can be formed using a similar material and a similar process to that used for the second optical component 503 of the first metallization layer 501 (described above with respect to FIG. 5). For example, the second active layer 801 of the fourth optical component 803 can be formed from alternating layers of a coating material such as silicon oxide and a core material such as silicon nitride, formed using deposition and patterning processes, to form an optical component such as a waveguide.

[0096] Figure 9 illustrates the formation of a first element via (TDV) 901, the formation of a third bonding layer 903, and the placement of an optical fiber 905 to form a first optical package 900. In an embodiment, the first element via 901 extends through the second active layer 801 and the first active layer 201 to provide a fast path for power, data, and ground through the optical medium 100. In an embodiment, the first element via 901 can be formed by first forming a through-via opening in the optical medium 100. The through-via opening can be formed by applying and developing a suitable photoresist (not shown) and removing exposed portions of the second active layer 801 and the optical medium 100.

[0097] Once the through-hole opening of the through element is formed within the optical medium 100, a gasket can be used to line the through-hole opening. The gasket can be, for example, an oxide formed from tetraethyl orthosilicate (TEOS) or silicon nitride, but any suitable dielectric material can also be used alternatively. The gasket can be formed using a plasma-enhanced chemical vapor deposition (PECVD) process, but other suitable processes such as physical vapor deposition or thermal processes can also be used.

[0098] Once a liner is formed along the sidewalls and bottom of the through-hole opening, a barrier layer (not shown separately) can be formed, and the remainder of the through-hole opening can be filled with a first conductive material. The first conductive material may contain copper, but other suitable materials may be used, such as aluminum, alloys, doped polycrystalline silicon, combinations thereof, etc. The first conductive material can be formed by electroplating copper onto a seed layer (not shown), filling and overfilling the through-hole opening. Once the through-hole opening is filled, excess liner, barrier layer, seed layer, and first conductive material outside the through-hole opening can be removed by a planarization process such as chemical mechanical polishing (CMP), but any suitable removal process can be used.

[0099] Optionally, in some embodiments, once the first element via 901 is formed, a second metallization layer electrically connected to the first element via 901 can be formed (not shown separately in FIG. 9). In embodiments, the second metallization layer can be formed as described above relative to the first metallization layer 501, for example, using a damascene process, dual damascene process, etc., to form alternating layers of dielectric and conductive materials. In other embodiments, an electroplating process can be used to form the second metallization layer to form and shape the conductive material, and then the conductive material is covered with a dielectric material. However, any suitable structure and manufacturing method can be utilized.

[0100] The third bonding layer 903 is formed to provide an electrical connection between the optical intermediary 100 and the subsequently attached device. In embodiments, the third bonding layer 903 may be similar to the first bonding layer 505, for example having a third bonding pad 909 (similar to the first bonding pad 507) or even a fifth optical element 911 (similar to the third optical element 511). However, any suitable element may be used.

[0101] Optionally, at this point in the process, fiber optic cable 905 can be attached. In an embodiment, fiber optic cable 905 serves as an optical input / output port to optical medium 100. In an embodiment, fiber optic cable 905 is positioned to optically couple fiber optic cable 905 and an optical input, such as a grating coupler (not shown separately in FIG. 9) that is part of a first optical component 203, a second optical component 503, or a third optical component 511. By positioning fiber optic cable 905 in this way, optical signals leaving fiber optic cable 905 are guided to, for example, the first active layer 201 of the first optical component 203 and the grating coupler 204. Similarly, fiber optic cable 905 is positioned such that optical signals leaving the first active layer 201 of the first optical component 203 are guided into fiber optic cable 905 for transmission. However, any suitable location can be used.

[0102] The optical fiber 905 can be fixed in place using, for example, optical adhesive. In some embodiments, the optical adhesive comprises a polymeric material, such as an epoxy acrylate oligomer, and may have a refractive index between about 1 and about 3. However, any suitable material may be used.

[0103] Furthermore, although fiber 905 is depicted as being attached at this point in the manufacturing process, this is intended to be illustrative and not limiting. Rather, fiber 905 can be attached at any suitable point in the process. Any suitable attachment point can be utilized, and all such attachments at any point in the process are fully intended to be included within the scope of this embodiment.

[0104] Using the structure and method proposed in this paper, a bidirectional grating coupler can be integrated into a silicon photonics platform, where the grating coupler can achieve higher coupling efficiency. Furthermore, the bidirectional grating coupler is suitable for light sources of different wavelengths and exhibits high wavelength selectivity, making it applicable to various optical systems. In addition, the multilayer bidirectional grating coupler structure can achieve wider bandwidth coupling and higher coupling efficiency, while also reducing polarization dependence.

[0105] In an embodiment, a method of forming an optical device includes: forming a first set of gratings in a grating layer present on a cladding layer; and forming a second set of gratings horizontally and vertically offset from the first set of gratings. In an embodiment, the grating layer is a single layer. In an embodiment, forming the first set of gratings in the grating layer includes etching a first trench in an upper surface of the grating layer, the upper surface of the grating layer being opposite to a lower surface of the grating layer, and the lower surface of the grating layer directly contacting the cladding layer. In an embodiment, the first trench of the first set of gratings includes a groove array, wherein the groove array forming the first set of gratings includes etching at a depth increasing from the periphery of the groove array to the center of the groove array. In an embodiment, the first set of gratings includes a grating array having a height increasing from the periphery of the grating array to the center of the grating array. In an embodiment, forming the second set of gratings in the grating layer includes patterning the cladding layer to provide a second trench, and depositing a grating layer on the cladding layer, wherein a portion of the grating layer fills the second trench to form the second set of gratings. In an embodiment, the grating layer is a multilayer structure. In an embodiment, forming the first set of gratings and the second set of gratings includes: etching a first trench into a first layer of a multilayer structure of grating layers; depositing a second layer on the first layer of the multilayer structure of grating layers, wherein the second layer fills a portion of the first trench in the first layer to provide the second set of gratings; and forming a second trench in the upper surface of the second layer to provide the first set of gratings. In an embodiment, the method further includes etching a third trench into the cladding layer before forming the first layer of the multilayer structure on the cladding layer, wherein the first layer of the multilayer structure formed after etching the third trench into the cladding layer fills the third trench to form the third set of gratings. In an embodiment, the method further includes forming a cladding layer on a mirror layer.

[0106] In another embodiment, the optical device includes: a single grating layer having a first set of gratings extending along a first direction in a first portion of the single grating layer and a second set of gratings extending along a second direction in a second portion of the single grating layer, the second portion being horizontally offset from the first portion; and a cladding layer in contact with the single grating layer. In an embodiment, at least one of the first set of gratings and the second set of gratings includes a trench array having a depth increasing from the periphery of the trench array to its center. In an embodiment, at least one of the first set of gratings and the second set of gratings includes a grating array having a height increasing from the periphery of the grating array to its center. In an embodiment, the single grating layer has a tapered width decreasing toward the waveguide junction portion. In an embodiment, a mirror layer is present on the cladding layer.

[0107] In another embodiment, the optical device includes: a first grating layer present on a cladding layer and having a plurality of trenches; and a second grating layer present on the first grating layer and having a first set of gratings on an upper surface of the second grating layer and a second set of gratings on a lower surface of the second grating layer that intersects with the first grating layer, wherein the first set of gratings has a height extending along a first direction, and the second set of gratings extends along a second direction into the plurality of trenches in the first grating layer. In an embodiment, at least one of the first set of gratings and the second set of gratings includes a groove array having a depth increasing from the periphery of the groove array to the center of the groove array. In an embodiment, at least one of the first set of gratings and the second set of gratings includes a grating array having a height increasing from the periphery of the grating array to the center of the grating array. In an embodiment, the optical device further includes a third set of gratings at the junction of the first grating layer and the cladding layer. In an embodiment, a first portion of the first set of gratings is horizontally offset from a second portion of the second set of gratings, and at least a first edge grating of the first set of gratings and at least a second edge grating of the second set of gratings horizontally overlap at a substantially central portion of the optical device.

[0108] The features of several embodiments have been summarized above to enable those skilled in the art to better understand aspects of this disclosure. Those skilled in the art should understand that they can readily use this disclosure as a basis for designing or modifying other processes and structures to achieve the same purposes and / or advantages as the embodiments described herein. Those skilled in the art should also recognize that such equivalent constructions do not depart from the spirit and scope of this disclosure, and that they can make various changes, substitutions, and alterations without departing from the spirit and scope of this disclosure.

[0109] 100: Optical Intermediates 101: First substrate 103: First insulating layer 103A: First cladding layer 105: Materials 201: First Active Layer 203: First optical component 204: Grating Coupler 205: Grating Coupler Section 206: The First Curtain 207: First Etched Mask 208: Area 1 209: Second Area 210, 213, 222, 224, 226: Ditches 211: Single grating layer 212: Second set of gratings 214: First set of gratings 215: Waveguide joint 216, 219: Edge raster 217, 220: Central grating 218: Groove 221: First grating layer 223: Second grating layer 225: Third group of gratings 260: Mirror layer 301: Semiconductor Materials 401: Second insulating layer 501: First metallization layer 503: Second optical component 505: First bonding layer 507: First bonding pad 509: First Dielectric Material 511: Third optical component 601: First Semiconductor Component 603: Semiconductor substrate 605: Active Component 607: Internal Wiring Structure 609: Second bonding layer 611: Third joint pad 613: Second gap filling material 701: Support substrate 703: Coupler Lens 801: Second Active Layer 803: Fourth optical component 900: First optical package 901: First component through hole 903: Third bonding layer 905: Fiber Optic 909: Third joint pad 911: Fifth Optical Component D1: First Direction D2: Second Direction D3: Direction P1, P2: Interval

Claims

1. A method for forming an optical device, comprising: The first set of gratings is formed in the grating layer existing on the cladding layer; And forming a second set of gratings that are horizontally and vertically offset from the first set of gratings, wherein forming the first set of gratings in the grating layer includes etching a first trench in the upper surface of the grating layer, the first trench of the first set of gratings including a groove array, wherein forming the groove array of the first set of gratings includes etching at a depth increasing from the periphery of the groove array to the center of the groove array.

2. The method of forming an optical device as claimed in claim 1, wherein the grating layer is a single layer, the upper surface of the grating layer is opposite to the lower surface of the grating layer, and the lower surface of the grating layer is in direct contact with the covering layer.

3. The method of forming an optical device as claimed in claim 2, wherein forming the second set of gratings in the grating layer includes patterning the cladding layer to provide a second trench, and depositing the grating layer on the cladding layer, wherein a portion of the grating layer fills the second trench to form the second set of gratings.

4. The method of forming an optical device as claimed in claim 1, wherein the grating layer is a multi-layer structure, and forming the first set of gratings and the second set of gratings comprises: Etch a second trench into the first layer of the multilayer structure of the grating layer; A second layer of the multilayer structure is deposited on the first layer of the multilayer structure of the grating layer, wherein the portion of the second layer that fills the second trench in the first layer provides the second set of gratings; And the first trench is formed in the upper surface of the second layer to provide the first set of gratings.

5. An optical device, comprising: A single grating layer having a first set of gratings extending along a first direction in a first portion of the single grating layer and a second set of gratings extending along a second direction in a second portion of the single grating layer, the second portion being horizontally offset from the first portion, and the first direction being different from the second direction; And a covering layer in contact with the single grating layer, wherein at least one of the first set of gratings and the second set of gratings includes a trench array having a depth increasing from the periphery of the trench array to the center of the trench array.

6. The optical device as claimed in claim 5, wherein the cladding layer is located between the single grating layer and the mirror layer.

7. An optical device, comprising: A first grating layer exists on the cladding layer, and the first grating layer has multiple trenches; And a second grating layer, existing on the first grating layer, the second grating layer having a first set of gratings on the upper surface of the second grating layer and a second set of gratings on the lower surface of the second grating layer that intersects with the first grating layer, wherein the first set of gratings extends along a first direction and the second set of gratings extends along a second direction into the plurality of trenches in the first grating layer, wherein at least one of the first set of gratings and the second set of gratings includes a groove array having a depth increasing from the periphery of the groove array to the center of the groove array.

8. The optical device of claim 7, wherein a first portion of the first set of gratings is horizontally offset from a second portion of the second set of gratings, and at least a first edge grating of the first set of gratings and at least a second edge grating of the second set of gratings are horizontally overlapped at a substantially central portion of the optical device.

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