Optical device and method of forming the same

Abstract

A method of forming an optical device includes forming an optical signal coupling material layer comprising at least one set of gratings on an cladding layer, and patterning the optical signal coupling material layer to provide a geometry comprising a grating structure and a waveguide, wherein the grating structure comprises at least one set of gratings. A transition region includes curved sidewalls located between the grating structure and the waveguide. In some embodiments, the curved sidewalls of the transition region have a concave curvature. In some embodiments, the curved sidewalls have a convex curvature.

Description

Prior Technology

[0001] Electronic signal processing is a technology used for signal transmission and processing. In recent years, optical signal processing has been used in an increasing number of applications, especially for signal transmission in fiber optic applications.

[0002] Optical devices provide optical signal coupling from fiber to waveguide for optical signal and processing systems. The efficiency of optical coupling has gradually improved, making the design of tapered structures relevant to advancing optical signal transmission. However, further improvements are still needed. Simple Explanation of the Diagram

[0003] The best understanding of all aspects of this disclosure can be obtained 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 various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or decreased for clarity. Figure 1 is a side cross-sectional view illustrating the intermediary layer used in a method for forming a photonics platform, according to some embodiments. Figure 2 is a side cross-sectional view illustrating the processing of an intermediate layer to provide a first optical device according to some embodiments. Figure 2A is a side cross-sectional view illustrating, according to some embodiments, forming a mask to isolate the interposer layer in the grating coupler portion and removing the interposer layer in the first insulating layer of the grating coupler portion. Figure 2B is a top view illustrating a grating coupler structure including a tapered transition region with concave curvature sidewalls between the grating structure and the waveguide, according to some embodiments. Figure 2C is a top view illustrating a grating coupler structure including a tapered transition region with convex curvature sidewalls between the grating structure and the waveguide, according to an embodiment of the present disclosure. Figure 2D is a side cross-sectional view illustrating, according to some embodiments, the formation of a reflective layer on the grating coupler portion of the intermediate layer depicted in Figure 2A, and the formation of a first cladding layer on the reflective layer. Figure 2E illustrates, according to some embodiments, etching trenches in a first cladding layer and depositing a first material layer to form a multilayer optical device including grating structure portions, waveguide portions and transition portions, wherein the material filling the trenches provides a side cross-sectional view of the first set of gratings. Figure 2F is a top view illustrating, according to some embodiments, a multilayer grating coupler structure including a first layer having a linear transition between the grating structure portion and the waveguide portion, and a second layer having a concave curvature tapered transition between the grating structure portion and the waveguide portion. Figure 2G is a side cross-sectional view illustrating, according to some embodiments, the formation of a second material layer to fabricate a multilayer optical device including a grating structure portion, a waveguide portion and a transition portion, and the formation of trenches in the second material layer to form a second set of gratings. Figure 2H is a side cross-sectional view illustrating the transmission of light energy from the first side to the second side of the multilayer grating coupler structure depicted in Figure 2G, according to some embodiments. Figure 2I is a top view illustrating, according to some embodiments, a multilayer grating coupler structure including a first layer having a tapered transition with convex curvature between the grating structure portion and the waveguide portion, and a second layer having a linear transition between the grating structure portion and the waveguide portion. Figure 2J is a side cross-sectional view illustrating the transmission of light energy from the first side to the second side of the multilayer grating coupler structure depicted in Figure 2I, according to some embodiments. Figure 2K is a top view illustrating, according to some embodiments, a multilayer grating coupler structure including a first layer having a tapered transition with convex curvature between the grating structure portion and the waveguide portion, and a second layer having a tapered transition with concave curvature between the grating structure portion and the waveguide portion. Figure 2L is a side cross-sectional view illustrating the transmission of light energy from the first side to the second side of the multilayer grating coupler structure depicted in Figure 2K, according to some embodiments. Figures 3-9 are side cross-sectional views illustrating, according to some embodiments, the formation of a photonics platform integrating the grating couplers described in Figures 2A-2K. Implementation

[0004] The following disclosure provides numerous different embodiments or instances for implementing various features of the invention. Specific examples of elements and configurations are described below to simplify the disclosure. These examples are not intended to be limiting. For instance, in the following description, the formation of a first feature above or on a second feature may include embodiments where the first and second features are in direct contact, and may also include embodiments where additional features may be formed between the first and second features so that the first and second features are not in direct contact. Furthermore, reference numerals and / or letters may be repeated throughout the disclosure. This repetition is for brevity and clarity and does not in itself indicate a relationship between the various embodiments and / or configurations discussed.

[0005] Additionally, for ease of explanation, spatially relative terms such as "beneath," "below," "lower," "above," and "upper" may be used herein to describe the relationship between one element or feature shown in the figures and another element or feature. These spatially relative terms are intended to cover different orientations of the device in use or operation, in addition to those shown in the figures. The device may have other orientations (rotated 90 degrees or in other orientations), and the spatially relative descriptive terms used herein can be interpreted accordingly.

[0006] In some embodiments, the structures and methods described herein provide optical device structures including a tapered transition between a grating coupler portion and a waveguide portion. 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 discussed embodiments can be incorporated into a wide range of implementations, and all such implementations are fully intended to be included within the scope of the embodiments.

[0007] Referring now to FIG1, the initial structure of the optical interposer 100 is illustrated. In the specific embodiment shown in FIG1, the optical interposer 100 is a photonic integrated circuit (PIC) and at this stage includes a first substrate 101, a first insulating layer 103, and a material 105 layer for the first active layer 201 of the first optical element 203 (not shown separately in FIG1, but further described and discussed below with respect to FIG2). In one embodiment, at the start of the fabrication process of the optical interposer 100, the first substrate 101, the first insulating layer 103, and the material 105 layer for the first active layer 201 of the first optical element 203 may together be part of a silicon-on-insulator (SOI) substrate. First looking at the first substrate 101, the first substrate 101 may be a semiconductor material such as silicon or germanium, a dielectric material such as glass, or any other suitable material that allows support for upper-layer devices.

[0008] The first insulating layer 103 may be a dielectric layer separating the first substrate 101 from the upper first active layer 201, and in some embodiments, it may also be part of an overlay material surrounding a subsequently fabricated first optical element 203 (discussed further below). In one embodiment, the first insulating layer 103 may be silicon oxide, silicon nitride, germanium oxide, germanium nitride, a combination thereof, or the like, formed using methods such as implantation (e.g., forming a buried oxide layer (BOX)), or deposited onto the first substrate 101 using methods such as chemical vapor deposition, atomic layer deposition, physical vapor deposition, a combination thereof, or the like. However, any suitable materials and manufacturing methods may be used.

[0009] The material 105 used for the first active layer 201 is initially (before patterning) a conformal material layer that will be used to begin fabricating the first active layer 201 of the first optical element 203. In one embodiment, the material 105 used for the first active layer 201 may be a translucent material that can be used as a core material for the desired first optical element 203, such as a semiconductor material like silicon, germanium, silicon-germanium, combinations thereof, or the like, while in other embodiments, the material 105 used for the first active layer 201 may be a dielectric material such as silicon nitride or the like, although in other embodiments, the material 105 used for the first active layer 201 may be a group III-V material, lithium niobate material, or a polymer. In embodiments where the material 105 of the first active layer 201 is deposited, the material 105 used for the first active layer 201 may be deposited using methods such as epitaxial growth, chemical vapor deposition, atomic layer deposition, physical vapor deposition, combinations thereof, or similar methods. 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 prior to the implantation process for forming the first insulating layer 103. However, the material 105 of the first active layer 201 can be formed using any suitable materials and manufacturing methods.

[0010] Figure 2 illustrates that once the material 105 for the first active layer 201 is ready, the first optical element 203 of the first active layer 201 is fabricated using the material 105. In embodiments, the first optical element 203 of the first active layer 201 may include elements 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, combinations thereof, or the like. However, any suitable first optical element 203 may be used.

[0011] In order to begin forming the first active layer 201 of the first optical element 203 from the initial material, the material 105 for the first active layer 201 may be patterned into the desired shape of the first active layer 201 of the first optical element 203. In one embodiment, the material 105 for the first active layer 201 may be patterned using, for example, one or more photolithography masks and etching processes. However, any suitable method may be used to pattern the material 105 for the first active layer 201. For the first optical element 203, the patterning process may be used for all or at least most of the fabrication of these first optical elements 203.

[0012] In some embodiments, a portion of the interposer 100 may be processed to provide a grating coupler 204 (as shown in FIG. 3). The portion of the interposer 100 processed to provide the grating coupler 204 is hereinafter referred to as the grating coupler portion 205 of the interposer 100. In some embodiments, to protect the first optical element 203 during the processing used to form the grating coupler 204, the portion of the interposer 100 containing the first optical element 203 is covered by a mask structure. In some embodiments, the mask structure is patterned to expose the grating coupler portion 205 of the interposer 100. The mask structure protecting the first optical element 203 from the process used to form 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 interposer grating coupler portion 205 may be removed after the grating coupler 204 is completed.

[0013] Figure 2A illustrates an embodiment in which a first mask 206 is formed to protect the first optical element 203 and expose the grating coupler portion 205 of the interposer layer 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 interposer layer 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 an etching chemical reaction selectively applied to the first substrate 101. After the first insulating layer 103 is removed, the upper surface of the first substrate 101 may be exposed.

[0014] Figures 2B-2L illustrate the grating coupler portion 205 of the processed interposer layer 100 to form a grating coupler 204 including a nonlinear tapered structure for achieving low transmission loss on a silicon photonics platform. The nonlinear tapered structure provides a transition between the grating and the waveguide interface portion of the grating coupler. The tapered transition is a waveguide region that gradually changes from a larger size to a smaller size, for example, a reduction in width, which is configured to achieve an optical coupling effect.

[0015] Figure 2B is a top view illustrating one embodiment of the nonlinear tapered transition region 210. The optical signal captured by the grating coupler 204 is affected by dimensional variations during transmission, which can lead to signal loss and reflection. To effectively reduce these effects, tapered structures with different curvatures can be used. In the example depicted in Figure 2B, a grating coupler 204 is illustrated, comprising a transition region 210 with a tapered geometry between the grating structure portion 293 and the waveguide portion 215.

[0016] Figure 2B illustrates an embodiment of a transition region 210 with convex curvature sidewalls 211, which provides a tapered structure between the grating structure portion 293 and the waveguide portion 215. The tapered structure is a gradual decrease in width along the length of the transition region 210. The width is the dimension of the opposing sidewalls 211 that separate the transition region 210.

[0017] More specifically, in some examples, the input side of transition region 210 is adjacent to grating structure portion 293 at first interface 212. First interface 212 begins with the last grating 226 in the group of gratings 225 in grating structure portion 293. A first width W1 at first interface 212 is the maximum width of transition region 210. The width of transition region 210 decreases along its length L1 to its narrowest point on the exit side. The exit side of transition region 210 is adjacent to waveguide portion 215 at second interface 214. Second interface 214 exists at the beginning of waveguide portion 215. Waveguide portion 215 begins when the opposing sidewalls 227 of the structure following transition region 210 are parallel to each other. A second width W2 at second interface 214 is the minimum width of transition region 210.

[0018] Figure 2B illustrates an embodiment in which the curvature of the relative sidewall 211 has a concave curvature. Concave curvature means that the vertex A1 of the curvature defining the geometry of the sidewall 211 is the point on the curve closest to the centerline C1 of the transition region 210. The curvature (α) of the sidewall 211 depicted in Figure 2B can also be described as greater than 1, for example, α > 1.

[0019] Figure 2C is a top view illustrating another embodiment of a grating coupler structure including a transition region 210 with convex curvature sidewalls. The transition region 210 depicted in Figure 2C is another example of a nonlinear transition. In the embodiment depicted in Figure 2C, the transition region 210 includes a sidewall 211 with curvature that provides a tapered structure between the grating structure portion 293 and the waveguide portion 215. The tapered structure is a gradual decrease in width along the length of the transition region 210. For example, a first width W1 at the first interface 212 is the maximum width of the transition region 210. The width of the transition region 210 decreases along at least a portion of its length L1 to its narrowest point on the exit side. The exit side of the transition region 210 is adjacent to the waveguide portion 215 at a second interface 214. The second interface 214 is present at the beginning of the waveguide portion 215. A second width W2 at the second interface 214 is the minimum width of the transition region 210.

[0020] Figure 2C illustrates an embodiment in which the curvature of the relative sidewall 211 has a convex curvature. A convex curvature means that the vertex A2 defining the curvature of the sidewall 211 is a point on the curve extending away from the centerline C1 of the transition region 210, as depicted in Figure 2C. The curvature (α) of the sidewall 211 depicted in Figure 2C can also be described as less than 1, for example, α < 1.

[0021] The tapered transition region 210 depicted in Figures 2B and 2C, such as a transition region with concave curvature sidewalls 211 (α>1) and / or convex curvature sidewalls 211 (α<1), is an example of a nonlinear tapered transition structure suitable for the transition region 210 between the grating coupler portion 204 and the waveguide portion 215 of an optical device. When applied to the transition region 210, these nonlinear tapered structures can be used in silicon photonic platforms where low transmission loss is required. In some embodiments, by integrating the nonlinear tapered structures described herein into the optical device, instabilities in the two-dimensional transmission direction optical signal can be reduced. The tapered structure of the sidewalls 211 can be designed and manufactured according to the characteristics and requirements of the waveguide for optimal results.

[0022] For example, when selecting the curvature of a tapered structure, factors such as the shape and size of the waveguide, the wavelength of the optical signal, and the properties of the material need to be considered. In some embodiments, a smoother curvature can reduce optical signal reflection and loss, but the size of the tapered structure may be larger. In other embodiments, a steeper curvature can reduce the size of the tapered structure, but may result in greater reflection and loss. In some embodiments, the transition region 210 between the grating structure portion 293 and the waveguide portion 215 functions to converge the optical signal into the main transmission layer waveguide, for example in a multilayer structure.

[0023] Figures 2D-2H illustrate one embodiment of forming a multilayer grating coupler 204, wherein at least one optical signal coupling material layer of the grating coupler 204 includes the nonlinear conical structure shown in Figures 2B and / or 2C. For the embodiment depicted in Figures 2D-2H, the nonlinear conical structure is present in the transition region 210 of the second material layer 221, which is most evident in the top views shown in Figures 2B and 2F. In some embodiments, the nonlinear conical structure of the transition region 210 is provided by sidewalls 211 with concave curvature, as depicted in Figure 2B. More specifically, the curvature (α) of the sidewalls 211 depicted in Figure 2B can also be described as greater than 1, for example, α > 1.

[0024] Figure 2D illustrates an initial structure that can be used to form a multilayer grating coupler 204, wherein at least one layer of the grating coupler 204 includes a nonlinear tapered structure in the transition region 210. During the processing of the grating coupler portion 205 depicted in Figures 2D-2I, the remainder of the interposer layer 100, including the first optical element 203, may be protected by one or more blocking masks and / or hard masks.

[0025] Figure 2D illustrates the formation of a reflective layer 260 on the grating coupler portion 205 of the intermediary layer 100 depicted in Figure 2A, and the formation of a first cladding layer 103A on the reflective layer 260.

[0026] Figure 2D illustrates an embodiment of forming a reflective layer 260 on the upper surface of a first substrate 101 present in the grating coupler portion 205. The reflective layer 260 may be composed of a metallic constituent material. For example, the reflective 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 reflective layer 260 may begin with the deposition of a seed layer. For example, the seed layer may comprise a copper layer. The seed layer may be deposited using processes such as sputtering, vapor deposition, or plasma-enhanced chemical vapor deposition (PECVD), or similar processes, depending on the desired materials. The reflective layer 260 may then be electroplated onto the seed layer. The electroplated metal of the reflective layer 260 may be deposited on the seed layer using electroplating processes such as electroplating or electroless plating. It should be noted that the methods and composition of the reflective layer 260 are provided for illustrative purposes only and are not intended to limit the disclosure to the materials and methods described above. Other compositions and methods of the reflective layer 260 are also within the scope of this disclosure, provided that the formed reflective layer 260 is a reflective structure. For example, the reflective layer 260 may be formed using a back-side processing method in the later stages of the process flow, such as after the formation of the grating structure. In some embodiments, the reflective layer 260 may be a distributed Bragg reflector (DBR).

[0027] Figure 2D also illustrates the formation of a first cladding layer 103A on the reflective layer 260. The first cladding layer 103A may be composed of an oxide-containing material, such as silicon dioxide (SiO2). The first cladding layer 103A may be deposited using a chemical vapor deposition (CVD) process. It should be noted 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 may be formed using deposition processes such as atomic layer deposition (ALD) or physical vapor deposition (PVD). Furthermore, the composition of the first cladding layer 103A is not limited to silicon dioxide. For example, in addition to silicon dioxide, the first cladding layer 103A may also be composed of silicon nitride, germanium oxide, germanium nitride, and combinations thereof.

[0028] Figure 2E illustrates the first material layer 209 forming the multilayer optical device. The first material layer 209 may be composed of an optical signal coupling material; for example, the first material layer 209 may be an optical signal coupling material layer. As depicted in Figure 2F, the first material layer 209 is patterned to include a grating structure portion 293, a waveguide portion 215, and a transition portion 210 (also referred to as a transition region). The transition portion 210 is located between the grating structure portion 293 and the waveguide portion 215.

[0029] Referring again to FIG2E, prior to depositing the first material layer 209, the upper surface of the first cladding layer 103A may be patterned and etched to provide a plurality of trenches 216. In some embodiments, forming trenches 216 in the first cladding layer 103A includes forming an etching mask (not shown). The etching mask protects portions of the first cladding layer 103A to form trenches 216. In some embodiments, the etching process for forming trenches 216 may be directional etching, such as reactive ion etching (RIE). The trenches 216 formed in the first cladding layer 103A are then filled with the material of the subsequently formed first material layer 209. In some embodiments, filling the trenches 216 with the material of the first material layer 209 provides a first set of gratings 213. In some embodiments, the trench 216 may be patterned with a geometry having curvature and a tapered width so that when filled with the material of the first material layer 209, it can provide a first set of gratings 213 having a geometry having curvature and a tapered width toward the waveguide portion 215, similar to the geometry of the grating 225 depicted in Figures 2B and 2C.

[0030] Figure 2E also illustrates a first material layer 209 deposited in a multilayer optical device. In this embodiment, the material filling the trenches 216 also provides a first set of gratings 213 extending along a first direction D1. The first material layer 209 can be deposited using a deposition method. In some embodiments, the first material layer 209 may be composed of a semiconductor material, such as a silicon-containing material, for example, silicon (Si). In some embodiments, the first material layer 209 may be composed of a dielectric material, such as a nitride-containing material, for example, silicon nitride (Si3N4).

[0031] In some embodiments, the first material layer 209 may be deposited using a chemical vapor deposition (CVD) process, wherein deposition parameters are selected to at least fill the trench 216 with the material of the first material layer 209. In one example, the chemical vapor deposition (CVD) process may be plasma-enhanced chemical vapor deposition (PECVD). In other examples, the first material layer 209 may be deposited using high-density plasma chemical vapor deposition (HDPCVD), atomic layer deposition (ALD), or physical vapor deposition (PVD).

[0032] As previously described, the material of the first material layer 209 filling the trench 216 provides a first set of gratings 213. In some embodiments, the height of the first set of gratings 213 can be adjusted to provide coupling to different wavelengths of the optical signal. In some examples, the height of the first set of gratings 213 can be varied by changing the etching depth of the trench 216. To change the etching depth of the trench 216, one or more etching masks and etching processes can be applied, wherein the etching time is varied to change different etching depths. In a further embodiment, the etching process can be accompanied by an ion implantation process, which can change the etching rate of the etched material.

[0033] After depositing the first material layer 209, the first material layer 209 may be patterned and etched to provide the geometry of the grating structure portion 293, the waveguide portion 215, and the transition region 210 between the grating structure portion 293 and the waveguide portion 215, as depicted in FIG2F. The etching process may include a masking step and a subtractive etching step.

[0034] The etching process used to form the geometry of the grating structure portion 293, the transition region 210, and the waveguide portion 215 can define the sidewall geometry of each of the grating structure portion 293, the transition region 210, and the waveguide portion 215. The sidewall geometry can define the width of each of the grating structure portion 293, the waveguide portion 215, and the transition region 210. For example, the width of the grating structure portion 293 is greater than the width of the waveguide portion 215. In the embodiment depicted in the process flow described in Figures 2D to 2H, the transition region 210 between the grating structure portion 293 and the waveguide portion 215 in the first material layer 209 is linear.

[0035] Figure 2F is a top view of another embodiment in which a nonlinear transition region is incorporated into the structure, in which the first semiconductor layer 209 includes a linear transition region 210. The transition region 210 of the first material layer 209 includes planar sidewalls 211 without curvature. For example, the planar sidewalls 211 of the transition region 210 of the first material layer 209 can also be characterized as α=1.

[0036] To provide the geometry of the first material layer 209 depicted in FIG. 2F, a photomask is formed on the upper surface of the first material layer 209 depicted in FIG. 2E of the multilayer optical device. The photomask is patterned to provide the geometry of the grating structure portion 293, the transition region 210, and the waveguide portion 215 in the first material layer 209. The photomask may be composed of a photoresist material, and the photomask may be patterned using photolithography and development processes. In some embodiments, the photomask structure may also be provided by a hard photomask. In some embodiments, the photomask used to etch the first material layer 209 may be a combination of a photoresist photomask and a hard photomask. After forming the photomask structure, an anisotropic etching process, such as reactive ion etching (RIE), may be applied to the first material layer 209. The etching process removes portions of the first material layer 209, wherein portions of the first material layer 209 protected by the etched photomask are retained to provide the geometry depicted in FIG. 2F.

[0037] Figure 2G illustrates the formation of a second material layer 221 in a multilayer optical device. The second material layer 221 may be composed of an optical signal coupling material; for example, it may be an optical signal coupling material layer. As depicted in Figure 2F, the second material layer 221 may include a grating structure portion 293, a waveguide portion 215, and a transition portion 210. In some embodiments, the transition region 210 of the grating coupler 204 includes a nonlinear tapered structure. More specifically, in the embodiments described with reference to Figures 2D-2H, the transition portion of the second material layer 221 is configured to include a nonlinear tapered transition region 210, wherein the sidewalls 211 of the transition region 210 have a concave curvature.

[0038] Referring to Figure 2G, the second material layer 221 can be formed by directly contacting the upper surface of the first material layer 209 using a deposition method. In some embodiments, the second material layer 221 of the multilayer optical device may be composed of a semiconductor material, such as a silicon-containing material, for example, silicon (Si). In some embodiments, the second material layer 221 may be composed of a dielectric material, such as a nitride-containing material, for example, silicon nitride (Si3N4). In some embodiments, the second material layer 221 can be deposited using a chemical vapor deposition (CVD) process. In one example, the chemical vapor deposition (CVD) process may be plasma-enhanced chemical vapor deposition (PECVD). In other examples, the second material layer 221 may be deposited using high-density plasma chemical vapor deposition (HDPCVD), atomic layer deposition (ALD), or physical vapor deposition (PVD).

[0039] Figure 2G also illustrates an embodiment of forming a second set of gratings 217 on the upper surface of the second material layer 221. In some embodiments, the second set of gratings 217 may be formed by forming trenches 239 on the upper surface of the second material layer 221. Forming trenches 239 on the upper surface of the second material layer 221 may include an etching process. For example, the etching process for forming trenches 239 may include forming a patterned etching mask to expose portions of the second material layer 221 to be etched to form trenches 239. The portions of the second material layer 221 protected by the etching mask and located between each pair of trenches 239 provide the second set of gratings 217 after the etching step for forming trenches 239. In some embodiments, the etching process for forming trenches 239 may be anisotropic etching, such as directional etching, like reactive ion etching (RIE). The second set of gratings 217 depicted in Figure 2G has a height extending in a second direction D2, which is opposite to the first direction D1 of the first set of gratings 213.

[0040] In some embodiments, the depth of trench 239 can be adjusted to provide different grating heights in the first set of gratings 213 to couple different wavelengths of optical signals. In some examples, the height of the first set of gratings 217 can be varied by changing the etching depth of trench 239. To vary the etching depth of trench 239, one or more etching masks and etching processes can be applied, wherein the etching time is varied to change different etching depths. In a further embodiment, the etching process can be accompanied by ion implantation, which can change the etching rate of the etched material. In other examples, the height of the grating can be varied by recessing the upper surface of the grating itself, which can also be achieved using multiple masks and etching steps.

[0041] The first direction D1 of the first set of gratings 213 is opposite to the second direction D2 of the second set of gratings 217. In some embodiments, the opposite first and second directions D1 and D2 of the first and second sets of gratings 213, 217 provide a bidirectional grating coupler structure 280. The first set of gratings 213, present on the lower surface of the first material layer 209, is vertically offset from the second set of gratings 217, present on the upper surface of the second material layer 221. In some embodiments, the vertical offset of the first set of gratings 213 relative to the second set of gratings 217 can improve the coupling efficiency of the grating coupler 204. For example, by offsetting the orientation and center position of the gratings, coupling efficiency can be increased while reducing insertion loss and reflection loss.

[0042] In some other embodiments, the distance between adjacent gratings in the first set of gratings 213 and the second set of gratings 217 can be increased or decreased to couple different wavelengths of the optical signal. For example, the distance between adjacent gratings in the first set of gratings 213 can be greater than the distance between adjacent gratings in the second set of gratings 217, so that the first set of gratings 213 is configured to couple broadband light of the optical signal.

[0043] The second material layer 221 may include a grating structure portion, a waveguide portion, and a transition portion. Light used for optical signal transmission may be affected by asymptotic dimensional changes during transmission, which can lead to signal loss and reflection. To effectively reduce these effects, a tapered structure with different curvatures can be used in the transition portion. In some embodiments, as depicted in FIG2B, the transition of the second material layer 221 of the grating coupler 204 includes a nonlinear tapered structure.

[0044] Figure 2B illustrates an embodiment of a transition region 210 having sidewalls 211, which have curvature providing a tapered structure between the grating structure portion 293 and the waveguide portion 215. The tapered structure is a gradual reduction in width along the length of the transition region 210. The nonlinear tapered structure of the transition region 210 is provided by the sidewalls 211 having concave curvature, as depicted in Figure 2B. More specifically, the curvature (α) of the sidewalls 211 depicted in Figure 2B can also be described as greater than 1, for example, α > 1. The geometry of the transition region 210 depicted in Figure 2B is etched into the second material layer 221 depicted in Figure 2G.

[0045] To provide the geometry depicted in FIG2B, a photomask is formed on the upper surface of the second material layer 221 depicted in FIG2G of the multilayer optical device. This photomask has been patterned into a shape to provide the geometry depicted in FIG2B. The photomask may be composed of a photoresist material and can be patterned using photolithography and development processes. In some embodiments, the photomask structure may also be provided by a hard photomask. In some embodiments, the photomask used to etch the second material layer 221 may be a combination of a photoresist photomask and a hard photomask. After forming the photomask structure, an anisotropic etching process, such as reactive ion etching (RIE), may be applied to the second material layer 221. The etching process removes portions of the second material layer 221, leaving portions of the second material layer 221 protected by the etched photomask to provide a geometry including a nonlinear tapered transition region with concave sidewall curvature, as depicted in FIG2B. In some embodiments, an etched photomask is used to etch the second material layer 221 to have a geometry having a grating structure portion 293, a nonlinear tapered transition region 210, and a waveguide portion 215.

[0046] Returning to Figure 2F, a top view illustrating a multilayer grating coupler structure 280 comprising a first material layer 209 and a second material layer 221, wherein the first material layer 209 has a linear transition region 210 between the grating structure portion 293 and the waveguide portion 215, and the second material layer 221 has a tapered transition region 210 with concave curvature between the grating structure portion 293 and the waveguide portion 215. The second material layer 221 exists above the first material layer 209, receiving optical signals before the first material layer 209. The second material layer 221 includes a nonlinear tapered transition, wherein a portion of the curvature of the transition region 210 is integrated with the grating structure portion 293. The first material layer 209 does not include the curvature for the tapered structure in the transition region 210.

[0047] Figure 2H illustrates the transmission of light energy from the first side to the second side of the multilayer grating coupler structure depicted in Figure 2H. The optical signal 274 received from optical fiber 905 (as shown in Figure 9) is first received by the grating structure of the second material layer 221 of the bidirectional grating coupler structure 280. A portion of the optical signal 274 is coupled to the second material layer 221 in the grating coupler portion and transmitted as a first coupled optical signal 276. A portion of the optical signal 274 not coupled to the second material layer 221 is transmitted to the lower first material layer 209 and / or reflected from the reflective layer 260 as an uncoupled optical signal 275. The uncoupled optical signal 275 may be reflected from the reflective layer 260 as a reflected optical signal 277. The reflected optical signal 277 may be coupled to the second material layer 221. The coupled reflected optical signal 278 may exit the grating coupler portion through a transition region in the second material layer 221. The transition region in the second material layer 221 includes a nonlinear tapered transition with concave sidewalls (α>1), while the transition region in the first material layer 221 is linear (α=1). The nonlinear tapered transition effectively reduces transmission loss in the waveguide transition and improves optical coupling efficiency. The reduction in transmission loss and improved coupling efficiency are evident when comparing the transition region in the second material layer 221, which includes a nonlinear tapered transition with concave curvature sidewalls, with the linear transition region in the first material layer 221. The exit of the first material layer 221 does not include most of the optical signal transmitted from the transition region 210, as transmission loss may occur there.

[0048] Optical signals are subject to progressively varying effects during transmission, which can lead to signal loss and reflection. To effectively reduce these effects, tapered structures with different curvatures can be used. In some embodiments, the tapered structure can be designed and manufactured to achieve optimal results based on the waveguide's characteristics and requirements. When selecting the curvature of the tapered structure, factors such as the waveguide's shape and size, the wavelength of the optical signal, and the material properties need to be considered. Generally, a smoother curvature can reduce optical signal reflection and loss, but the size of the tapered structure may be larger. On the other hand, a steeper curvature can reduce the size of the tapered structure, but may result in greater reflection and loss.

[0049] Figures 2I and 2J illustrate another embodiment of the multilayer grating coupler 204, wherein at least one layer of the grating coupler 204 includes a nonlinear conical structure. More specifically, in the embodiments depicted in Figures 2I-2J, the nonlinear conical structure of the transition region 210 is provided by sidewalls 211 with convex curvature, as depicted in Figure 2C. More specifically, the curvature (α) of the sidewalls 211 depicted in Figure 2C can also be described as less than 1, for example, α < 1. The transition region 210 (as depicted in Figure 2C), including the nonlinear conical structure with convex curvature sidewalls 211, is located in the first material layer 209 of the bidirectional grating coupler structure 280 depicted in Figure 2I. In the embodiment depicted in Figure 2I, the second material layer 221 includes a linear transition region. In some embodiments, the transition region 210 in the second material layer 221 has planar sidewalls that can be described as α = 1.

[0050] The method described above for forming the multilayer optical device depicted in Figures 2C-2H is applicable to forming the embodiments depicted in Figures 2I and 2J. More specifically, the process steps described in Figures 2D, 2E, and 2G are applicable to forming the structures depicted in Figures 2I and 2J. The process steps described in Figure 2E provide the first material layer 209 depicted in Figures 2I and 2J, wherein a photomask for patterning the geometry of the first material layer 209 is selected to provide the geometry depicted in Figure 2C. Figure 2C illustrates an embodiment of a transition region 210 having convex curvature sidewalls 211, which provide a tapered structure between the grating structure portion 293 and the waveguide portion 215. The process steps described in Figure 2G provide the second material layer 221 depicted in Figures 2I and 2J, wherein a photomask for patterning the geometry of the second material layer 221 is selected to provide a linear transition region 210, wherein the sidewalls can be described as α=1.

[0051] Figure 2I is a top view illustrating a multilayer grating coupler structure 280 including a first material layer 209 and a second material layer 221. The first material layer 209 has a transition region 210 with a convex curvature tapered shape between the grating structure portion 293 and the waveguide portion 215 (as seen in Figure 2C). The second material layer 221 has a linear transition region 210 between the grating structure portion 293 and the waveguide portion 215. The second material layer 221 exists above the first material layer 209, and receives optical signals before the first material layer 209. The first material layer 209 includes a nonlinear tapered transition, wherein a portion of the curvature of the transition region 210 is integrated with the grating structure portion 293. The second material layer 221 does not include the curvature for the tapered shape in the transition region 210.

[0052] Figure 2J also illustrates the transmission of optical signals from the first side to the second side of the multilayer grating coupler structure. The optical signal 274 received from the optical fiber 905 (as seen in Figure 9) is first received by the grating structure of the second material layer 221 of the bidirectional grating coupler structure 280. A portion of the optical signal 274 is coupled to the second material layer 221 at the grating coupler portion and transmitted as a first coupled optical signal 276. The portion of the optical signal 274 not coupled to the second material layer 221 is transmitted to the lower first material layer 209 and / or reflected from the reflective layer 260 as an uncoupled optical signal 275. The uncoupled optical signal 275 may be reflected from the reflective layer 260 as a reflected optical signal 277. The reflected optical signal 277 may be coupled to the first material layer 209 as a coupled reflected optical signal 281. Furthermore, the first coupled optical signal 276 in the second material layer 221 may also be transmitted to the first material layer 209 as a transmitted optical signal 279. The coupled reflected optical signal 281 and the transmitted optical signal 279 from the second material layer 221 may exit the grating coupler section through a transition region in the first material layer 209. The transition region in the first material layer 209 includes a nonlinear tapered transition with a convex curvature (α<1), while the transition region in the second material layer 221 is linear (α=1). The nonlinear tapered transition effectively reduces transmission loss in the waveguide transition and improves optical coupling efficiency. A significant reduction in transmission loss and improvement in coupling efficiency can be observed when comparing the transition region in the first material layer 209, which includes a nonlinear tapered transition with convex curvature sidewalls (as depicted in Figure 2C), with the linear transition region in the second material layer 221. The exit of the first material layer 221 does not include most of the optical signal transmitted from the transition region 210 due to transmission loss that may occur therein.

[0053] Figures 2K and 2L illustrate another embodiment of the multilayer grating coupler 204, wherein at least two layers of the multilayer grating coupler 204 include nonlinear tapered structures. More specifically, in the embodiment depicted in Figures 2K-2L, the nonlinear tapered structure of the transition region 210 exists simultaneously in the first material layer 209 and the second material layer 221.

[0054] For example, in the first material layer 209, the nonlinear conical structure is provided by sidewalls 211 with convex curvature, as depicted in FIG2C. More specifically, the curvature (α) of the sidewalls 211 depicted in FIG2C can also be described as less than 1, i.e., α < 1. The transition region 210 of the first material layer 209 includes a nonlinear conical structure with sidewalls 211 having convex curvature (as depicted in FIG2C).

[0055] For example, in the second material layer 221, the nonlinear conical structure is provided by sidewalls 211 with concave curvature, as depicted in FIG2B. More specifically, the curvature (α) of the sidewalls 211 depicted in FIG2B can also be described as greater than 1, i.e., α>1. The transition region 210 of the second material layer 221 includes a nonlinear conical structure with sidewalls 211 having concave curvature (as depicted in FIG2B).

[0056] The method described above for forming the multilayer optical device depicted in Figures 2C-H is applicable to forming the embodiments depicted in Figures 2K and 2L. More specifically, the process steps described in Figures 2D, 2E, and 2G are applicable to forming the structures depicted in Figures 2K and 2L. The process steps described in Figure 2E provide a first material layer 209 depicted in Figures 2K and 2L, wherein a photomask for patterning the geometry of the first material layer 209 is selected to provide the geometry depicted in Figure 2C. Figure 2C illustrates an embodiment of the transition region 210, which has sidewalls 211 with convex curvature, providing a tapered structure between the grating structure 293 and the waveguide portion 215. The process steps described in Figure 2G provide a second material layer 221 depicted in Figures 2K and 2L, wherein a photomask for patterning the geometry of the second material layer 221 is selected to provide the geometry depicted in Figure 2B. Figure 2B illustrates an embodiment of the transition region 210, which has a concave curvature sidewall 211 that provides a tapered structure between the grating structure 293 and the waveguide portion 215.

[0057] Figure 2K is a top view illustrating a multilayer grating coupler structure 280 including a first material layer 209 and a second material layer 221. The first material layer 209 has a tapered transition with convex curvature between the grating structure portion 293 and the waveguide portion 215 (as seen in Figure 2C), while the second material layer 221 has a tapered transition with concave curvature between the grating structure portion 293 and the waveguide portion 215 (as seen in Figure 2B). The second material layer 221 is located above the first material layer 209, and receives optical signals in front of the first material layer 209.

[0058] Figure 2L illustrates the transmission of light energy from the first side to the second side of the multilayer grating coupler structure. The optical signal 274 received from the optical fiber 905 (as seen in Figure 9) is first received by the grating structure of the second material layer 221 of the bidirectional grating coupler structure 280. A portion of the optical signal 274 is coupled to the second material layer 221 in the grating coupler portion and transmitted as a first coupled optical signal 276. A portion of the optical signal 274 not coupled to the second material layer 221 is transmitted to the lower first material layer 209 and / or reflected from the reflective layer 260 as an uncoupled optical signal 275. The uncoupled optical signal 275 may be reflected from the reflective layer 260 as a reflected optical signal 277. The reflected optical signal 277 may be coupled to the first material layer 209 as a coupled reflected optical signal 281. Furthermore, the first coupled optical signal 276 in the second material layer 221 may also be transmitted to the first material layer 209 as a transmitted optical signal 279. The coupled reflected optical signal 281 and the transmitted optical signal 279 from the second material layer 221 may exit the grating coupler portion through the transition region in the first material layer 209. The transition region in the first material layer 209 includes a nonlinear tapered transition with a convex curvature (α<1), while the transition region in the second material layer 221 includes a nonlinear tapered transition with a concave curvature (α>1).

[0059] Figures 3-9 illustrate the integration of the grating coupler 204 described with reference to Figures 2A-2L into an optical package. Each embodiment depicted in Figures 2A-2L can be integrated into the optical package described with reference to Figures 3-9. For simplicity, the different embodiments of the grating coupler depicted in Figures 2A-2L can be collectively referred to in Figures 3-9 as the structure of grating coupler 204 with reference number. In some embodiments, any masking structures, such as hard masks and / or photoresist masks, used to isolate the interposer layer 100 during the formation of the grating coupler 204 may be removed before processing the integration of the grating coupler 204 into the optical package.

[0060] Figure 3 illustrates that for components requiring further fabrication processes, such as Mach-Zehnder silicon photonic switches utilizing resistance-heated elements, additional processing can be performed before or after patterning the material of the first active layer 201 to form the first optical element, or before or after forming the grating coupler 204. For example, implantation processes, additional deposition and patterning processes of different materials (e.g., resistance-heated elements, III-V materials for converters), combinations of all these processes, or similar methods can be used to facilitate further fabrication of various desired first optical elements 203. In a particular embodiment, as specifically illustrated in Figure 3, in some embodiments, epitaxial deposition of a semiconductor material 301 (e.g., germanium, for electro / optical signal modulation and conversion) can be performed on the patterned portion of the material 105 of the first active layer 201. In this embodiment, the semiconductor material 301 can be epitaxially grown to facilitate the fabrication of, for example, photodiodes for photoelectric converters. All these fabrication processes and all suitable first optical elements 203 can be fabricated, and all these combinations are fully intended to be included within the scope of the embodiments.

[0061] Figure 4 illustrates that once the grating coupler 204 and the first optical element 203 are formed, a second insulating layer 401 can be deposited to cover the grating coupler 204 and the first optical element 203. The second insulating layer 401 can provide additional covering material. In one embodiment, the second insulating layer 401 may be a dielectric layer that separates the individual elements of the first active layer 201 from each other and from the upper structure, and may additionally serve as another portion of the covering material surrounding the first optical element 203 and the grating coupler 204. In one embodiment, the second insulating layer 401 may be silicon oxide, silicon nitride, germanium oxide, germanium nitride, combinations thereof, or the like, formed using deposition methods such as chemical vapor deposition, atomic layer deposition, physical vapor deposition, combinations thereof, or similar deposition methods. Once the material for the second insulating layer 401 has been deposited, a process such as chemical mechanical polishing can be used to planarize the material, either by planarizing 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 element 203 and the grating coupler 204) or by planarizing the second insulating layer 401 with the top surfaces of the first optical element 203 and the grating coupler 204. However, any suitable material and manufacturing method can be used.

[0062] Figure 5 illustrates that once the first optical element 203 and grating coupler 204 have been fabricated and the second insulating layer 401 has been formed, a first metallization layer 501 is formed to electrically connect the first active layer 201 of the first optical element 203 and the grating coupler 204 to the control circuit, to each other, and to subsequently attached devices (not shown in Figure 5, but further illustrated and described in Figure 6). In one embodiment, the first metallization layer 501 is formed from alternating layers of dielectric and conductive materials and can be formed by any suitable procedure (such as deposition, single damascene, double damascene, etc.). In certain embodiments, multiple metallization layers may be used to interconnect the various first optical elements 203 and grating couplers 204, but the exact number of first metallization layers 501 depends on the design of the optical interposer 100.

[0063] Furthermore, during the fabrication of the first metallization layer 501, one or more second optical elements 503 may be formed as part of the first metallization layer 501. In some embodiments, the second optical elements 503 of the first metallization layer 501 may include elements such as couplers (e.g., edge couplers, grating couplers, etc.) for connecting external signals, optical waveguides (e.g., ridge waveguides, rib waveguides, buried channel waveguides, diffused waveguides, etc.), optical modulators (e.g., Mach-Zehnder silicon optical switches, microelectromechanical switches, microring resonators, etc.), amplifiers, multiplexers, demultiplexers, photoelectric converters (e.g., PN junctions), electro-optic converters, lasers, combinations thereof, or the like. However, any suitable optical element may be used for one or more second optical elements 503. In one embodiment, one or more second optical elements 503 may be formed by initially depositing material for one or more second optical elements 503. In one embodiment, the material of one or more second optical elements 503 may be a dielectric material such as silicon nitride, silicon oxide, combinations thereof, or the like, or a semiconductor material such as silicon, deposited using deposition methods such as chemical vapor deposition, atomic layer deposition, physical vapor deposition, combinations thereof, or similar deposition methods. However, any suitable material and any suitable deposition method may be used.

[0064] Once the material of one or more second optical elements 503 has been deposited or otherwise formed, the material can be patterned into the desired shape of the one or more second optical elements 503. In one embodiment, the material of one or more second optical elements 503 can be patterned using, for example, one or more photolithography masks and etching processes. However, any suitable method can be used to pattern the material of one or more second optical elements 503.

[0065] For some of the one or more second optical elements 503, such as waveguides or edge couplers, the patterning process may be used to form all or at least most of the fabrication of these elements. Furthermore, for elements requiring further fabrication processes, such as Mach-Zehnder silicon optical switches utilizing resistance-heated elements, additional processing may be performed before or after the material patterning of the one or more second optical elements 503. For example, implantation processes, additional deposition and patterning processes of different materials, combinations of all these processes, or similar processes may be used to aid in the further fabrication of various desired one or more second optical elements 503. All these fabrication processes and all suitable one or more second optical elements 503 can be fabricated, and all these combinations are fully intended to be included within the scope of the embodiments.

[0066] Once one or more second optical elements 503 of the first metallization layer 501 have been fabricated, a first bonding layer 505 is formed on the first metallization layer 501. In one embodiment, 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, or the like. The first dielectric material 509 can be deposited using any suitable method, such as CVD, high-density plasma chemical vapor deposition (HDPCVD), PVD, atomic layer deposition (ALD), or similar methods. However, any suitable materials and deposition processes can be used.

[0067] Once the first dielectric material 509 is formed, a first opening is formed in the first dielectric material 509 to expose the conductive portion of the underlying layer, preparing for the formation of a first bonding pad 507 within the first bonding layer 505. Once the first opening is formed in the first dielectric material 509, it can be filled with a seed layer and electroplated metal to form the first bonding pad 507 within the first dielectric material 509. A seed layer can be deposited over the entire surface of the first dielectric material 509, the exposed conductive portion of the underlying layer, and the sidewalls of the opening and the second opening. The seed layer may include a copper layer. The seed layer can be deposited using processes such as sputtering, evaporation, or plasma-enhanced chemical vapor deposition (PECVD), depending on the desired material. Electroplated metal can be deposited on the seed layer using electroplating processes such as electroplating or electroless plating. The electroplated metal may include copper, copper alloys, or the like. The electroplated metal can serve as a filler material. Prior to the seed layer, a barrier layer (not shown separately) can be deposited over the entire surface of the first dielectric material 509 and the sidewalls of the opening and the second opening. The barrier layer may include titanium, titanium nitride, tantalum, tantalum nitride, or the like.

[0068] After filling the first opening, a planarization process, such as CMP, is performed to remove excess portions of the seed layer and electroplated metal, 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 via the underlying conductive portion.

[0069] Furthermore, the first bonding layer 505 may also include one or more third optical elements 511 integrated within the first bonding layer 505. In this embodiment, before depositing the first dielectric material 509, one or more third optical elements 511 may be fabricated using methods and materials similar to those used for one or more second optical elements 503 (as described above), such as waveguides and other structures at least partially formed by deposition and patterning processes. However, any suitable structure, material, and manufacturing method may be used.

[0070] Figure 6 illustrates the bonding of the first semiconductor device 601 to the first bonding layer 505 of the optical interposer 100. In some embodiments, the first semiconductor device 601 is an electronic integrated circuit (EIC, e.g., a device without optical components), which may have a semiconductor substrate 603, a layer of active device 605, an interconnect structure 607 covering thereon, a second bonding layer 609, and an associated third bonding pad 611. In one embodiment, 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 device 605 may be a transistor, capacitor, resistor, etc. formed on the semiconductor substrate 603, the 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 device may be used.

[0071] In one embodiment, the first semiconductor device 601 may be configured to operate in conjunction with the optical interposer 100 to achieve the desired function. In some embodiments, the first semiconductor device 601 may be a high-bandwidth memory (HBM) module, xPU, logic die, 3DIC die, CPU, GPU, SoC die, MEMS die, a combination thereof, or similar device. Any suitable device with any suitable function may be used, and all such devices are fully intended to be included within the scope of the embodiments.

[0072] In one embodiment, the first semiconductor device 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, combinations thereof, or similar processes, as an example. In embodiments using wet processing, 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.

[0073] After the activation process, the optical interposer 100 and the first semiconductor device 601 can be cleaned using, for example, a chemical cleaning agent. The first semiconductor device 601 is then aligned and positioned to physically contact the optical interposer 100. Heat treatment and contact pressure are applied to the optical interposer 100 and the first semiconductor device 601 to bond the optical interposer 100 and the laser die 600. For example, the optical interposer 100 and the first semiconductor device 601 can be subjected to pressures of about 200 kPa or less, and temperatures between about 25°C and about 250°C to fuse the optical interposer 100 and the first semiconductor device 601. The optical interposer 100 and the first semiconductor device 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, between about 150°C and about 650°C, to fuse the metals. In this way, the optical interposer 100 and the first semiconductor device 601 form a dielectric-to-dielectric and metal-to-metal bonding device. In some embodiments, the bonded grains are baked, annealed, pressed, or otherwise treated to strengthen or complete the bond.

[0074] Furthermore, although specific processes for initiating and strengthening the bond have been described, these descriptions are intended to be illustrative and not to limit the embodiments. Specifically, any suitable combination of baking, annealing, pressing, or other processes may be utilized. All such processes are fully intended to be included within the scope of the embodiments.

[0075] Figure 6 further illustrates that once the first semiconductor device 601 has been bonded, a second interstitial material 613 is deposited to fill the space around the first semiconductor device 601 and provide additional support. In one embodiment, the second interstitial material 613 may be a material such as silicon oxide, silicon nitride, silicon oxynitride, combinations thereof, or similar materials, deposited to fill and overfill the space around the first semiconductor device 601. However, any suitable material and deposition method may be used.

[0076] Once the second interstitial material 613 has been deposited, it can be planarized to expose the first semiconductor device 601. In one embodiment, the planarization process can be a chemical mechanical planarization process, a polishing process, or a similar process. However, any suitable planarization process can be used.

[0077] Figure 7 illustrates the attachment of a support substrate 701 to a first semiconductor device 601 and a second interstitial material 613. In one embodiment, the support substrate 701 may be a support material transparent to the desired wavelength of light, such as silicon, and may be attached using, for example, an adhesive (not shown separately in Figure 7). However, in other embodiments, the support substrate 701 may be bonded to the first semiconductor device 601 and the second interstitial material 613 using, for example, a bonding process. Any suitable method may be used to attach the support substrate 701.

[0078] Figure 7 further illustrates that the support substrate 701 includes a coupling lens 703, positioned to facilitate movement from the optical fiber 905 (not shown in Figure 7 but further illustrated and described in Figure 9) to the grating coupler 204, the second optical element 503, or the third optical element 511 of the first metallization layer 501. In one embodiment, the coupling lens 703 can be formed by shaping the material of the support substrate (e.g., silicon) using a photomask and etching process. However, any suitable process can be used.

[0079] Figure 8 illustrates the removal of the first substrate 101 and optionally the first insulating layer 103, thereby exposing the first active layer 201 of the first optical element 203 and the grating coupler 204. In one embodiment, planarization processes such as chemical mechanical polishing, grinding, one or more etching processes, combinations thereof, or similar processes can be used to remove the first substrate 101 and the first insulating layer 103. However, any suitable method can be used to remove the first substrate 101 and / or the first insulating layer 103.

[0080] Once the first substrate 101 and the first insulating layer 103 have been removed, a second active layer 801 of the fourth optical element 803 can be formed on the back side of the first active layer 201. In one embodiment, the second active layer 801 of the fourth optical element 803 can be formed using similar materials and similar processes to those used for the second optical element 503 of the first metallization layer 501 (as described above with respect to FIG. 5). For example, the second active layer 801 of the fourth optical element 803 can be formed from alternating layers of a cladding material such as silicon oxide and a core material such as silicon nitride, using deposition and patterning processes to form optical elements such as waveguides and similar optical elements.

[0081] Figure 9 illustrates the formation of a first device 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 one embodiment, the first device 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 interposer 100. In one embodiment, the first device via 901 can be formed by initially forming a via opening in the optical interposer 100. The via opening can be formed by coating and developing a suitable photoresist (not shown) and removing exposed portions of the second active layer 801 and the optical interposer 100.

[0082] Once the device via opening is formed in the optical interposer 100, a liner can be used to cover the device via opening. The liner can be, for example, an oxide formed of tetraethyl orthosilicate (TEOS) or silicon nitride, although any suitable dielectric material can be used instead. The liner can be formed using a plasma-enhanced chemical vapor deposition (PECVD) process, although other suitable processes, such as physical vapor deposition or thermal processes, can also be used.

[0083] Once a liner is formed on the sidewalls and bottom of the device via opening, a barrier layer (also not shown separately) can be formed, and the remainder of the device via opening can be filled with a first conductive material. The first conductive material may include copper, although other suitable materials such as aluminum, alloys, doped polycrystalline silicon, combinations thereof, and the like may be used. The first conductive material can be formed by electroplating copper onto a seed layer (not shown), filling and overfilling the device via opening. Once the device via opening is filled, excess liner, barrier layer, seed layer, and first conductive material outside the device via opening can be removed by a planarization process such as chemical mechanical polishing (CMP), although any suitable removal process may be used.

[0084] Optionally, in some embodiments, once the first device via 901 is formed, a second metallization layer (not shown separately in FIG. 9) electrically connected to the first device via 901 can be formed. In one embodiment, the second metallization layer can be formed as described above with respect to the first metallization layer 501, for example, by using a damascene process, a dual damascene process, or a similar process to form alternating layers of dielectric and conductive materials. In other embodiments, an electroplating process can be used to form and shape the conductive material, and then the conductive material can be covered with a dielectric material to form the second metallization layer. However, any suitable structure and manufacturing method can be used.

[0085] A third bonding layer 903 is formed to provide an electrical connection between the optical interposer 100 and the subsequently connected device. In one embodiment, the third bonding layer 903 may be similar to the first bonding layer 505, for example having a fourth 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 device may be used.

[0086] Optionally, at this point in the process, fiber optic cable 905 can be connected. In one embodiment, fiber optic cable 905 serves as an optical input / output port for optical interposer 100. In one embodiment, fiber optic cable 905 is positioned such that it is optically coupled to an optical input (e.g., a grating coupler, not shown separately in FIG. 9) that is part of a first optical element 203, a second optical element 503, or a third optical element 511. By positioning fiber optic cable 905 in this way, optical signals exiting fiber optic cable 905 are directed, for example, to the first active layer 201 of the first optical element 203 and the grating coupler 204. Similarly, fiber optic cable 905 is positioned such that optical signals exiting the first active layer 201 of the first optical element 203 are introduced into fiber optic cable 905 for transmission. However, any suitable location can be used.

[0087] 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.

[0088] Furthermore, although the illustration shows fiber optic 905 connected at this point in the manufacturing process, this is merely illustrative and not intended to be limiting. Instead, fiber optic 905 can be connected at any suitable point in the process. Any suitable connection point can be used, and all such connections at any point in the process are fully intended to be included within the scope of this embodiment.

[0089] By utilizing the structures and methods presented herein, nonlinear designs in the transition region between the grating structure and the waveguide can effectively reduce transmission losses and improve optical coupling efficiency during the waveguide transition. In some embodiments, the nonlinear gradient structure can reduce instabilities during waveguide width convergence, avoiding additional losses and reflections. In some embodiments, the nonlinear design has significant application advantages, and can be applied to multilayer structures to reduce interlayer switching losses and improve overall optical performance. The nonlinear gradient structure can integrate components of different sizes and patterns to achieve optical coupling between components. In some embodiments, the nonlinear tapered structure design provides a transition in a multilayer optical device structure to focus light into the main transmission layer waveguide, such as an optical device including a multilayer grating coupler.

[0090] In some embodiments, a method of forming an optical device is provided, comprising forming an optical signal coupling material layer comprising at least one set of gratings on an cladding layer, and patterning the optical signal coupling material layer to provide a geometry comprising a grating structure having at least one set of gratings and a waveguide, wherein a transition region comprising curved sidewalls exists between the grating structure and the waveguide. In some embodiments, the curved sidewalls of the transition region begin at the interface between the grating structure and the transition region from the last grating of the at least one set of gratings. In some embodiments, the curved sidewalls of the transition region have a concave curvature relative to a centerline extending along the length of the grating structure, the transition region, and the waveguide. In some embodiments, the curved sidewalls of the transition region have a convex curvature relative to a centerline extending along the length of the grating structure, the transition region, and the waveguide. In some embodiments, the multilayer structure comprises a first material layer on the cladding layer and a second material layer on the first material layer. The at least one set of gratings comprises a first set of gratings extending from the base of the first material layer in a first direction and a second set of gratings extending from the upper surface of the second material layer in a second direction, wherein the first set of gratings having the first direction and the second set of gratings having the second direction provide a bidirectional grating structure. In some embodiments, the optical signal coupling material layer is a multilayer structure, and forming the optical signal coupling material layer includes forming a first material layer on a cladding layer; patterning the first material layer to include a linear transition region; and forming a second material layer on the first material layer, wherein the second material layer is formed on the first material layer, and the patterning of the optical signal coupling material layer includes patterning the second material layer to provide a geometry including a grating structure having at least one set of gratings and a waveguide, wherein a transition region including curved sidewalls exists between the grating structure and the waveguide. In some embodiments, the curved sidewalls have a concave curvature. In some embodiments, the optical signal coupling material layer is a multilayer structure, and forming the optical signal coupling material layer includes forming a first material layer on a cladding layer, wherein the patterning of the optical signal coupling material layer includes patterning the first material layer to provide a geometry including a grating structure having at least one set of gratings and a waveguide, wherein a transition region including curved sidewalls exists between the grating structure and the waveguide. In some embodiments, forming the optical signal coupling material further includes forming a second material layer on the first material layer and patterning the first material layer to include a linear transition region. In some embodiments, the curved sidewalls have a convex curvature. In some embodiments, the optical signal coupling material layer is a multilayer structure, wherein forming the optical signal coupling material layer includes forming a first material layer on a cladding layer, wherein patterning the optical signal coupling material layer includes patterning the first material layer to provide a geometry including a grating structure and a waveguide having at least one set of gratings, with a transition region including curved sidewalls having a first curvature type between the grating structure and the waveguide, the curved sidewalls having a first curvature type, forming a second material layer on the first material layer, and patterning the second material layer to include a tapered transition region having sidewalls of a second curvature type.In some embodiments, the first curvature type of the curved sidewalls in the transition region of the first material layer is convex curvature, and the second curvature type of the sidewalls in the conical transition region of the second material layer is concave curvature.

[0091] In another embodiment, the optical device includes a cladding layer; and an optical signal coupling material layer on the cladding layer, the optical signal coupling material layer including a grating structure having at least one set of gratings and a waveguide, wherein a transition region including sidewalls with concave curvature exists between the grating structure and the waveguide. In some embodiments, the optical signal coupling material layer is a multilayer structure. In some embodiments, the multilayer structure includes a first material layer on the cladding layer and a second material layer on the first material layer, wherein at least one set of gratings includes a first set of gratings extending from the base of the first material layer in a first direction and a second set of gratings extending from the upper surface of the second material layer in a second direction, wherein the first set of gratings having the first direction and the second set of gratings having the second direction provide a bidirectional grating structure. In some embodiments, the multilayer structure of the optical signal coupling material layer includes a first material layer on the cladding layer and a second material layer on the first material layer, wherein the first material layer includes a linear transition region, and the second material layer includes a grating structure having at least one set of gratings, a waveguide, and a curved sidewall of the transition region having concave curvature. In some embodiments, the multilayer structure of the optical signal coupling material layer includes a first material layer on the cladding layer and a second material layer on the first material layer, wherein the first material layer includes a grating structure, a waveguide and a transition region including a sidewall with concave curvature between the grating structure and the waveguide, and the second material layer includes a tapered transition region having a sidewall with convex curvature.

[0092] In another embodiment, the optical device includes a cladding layer; and an optical signal coupling material layer on the cladding layer, the optical signal coupling material layer including a grating structure having at least one set of gratings and a waveguide, wherein a transition region including sidewalls with convex curvature exists between the grating structure and the waveguide. In some embodiments, the optical signal coupling material layer is a multilayer structure. In some embodiments, the optical signal coupling material layer is a multilayer structure of a first material layer on the cladding layer and a second material layer in the first material layer, wherein at least one set of gratings includes a first set of gratings extending from the base of the first material layer in a first direction and a second set of gratings extending from the upper surface of the second material layer in a second direction, wherein the first set of gratings having the first direction and the second set of gratings having the second direction provide a bidirectional grating structure. In some embodiments, the multilayer structure of the optical signal coupling material layer includes a first material layer on the cladding layer and a second material layer on the first material layer, wherein the first material layer includes a tapered transition region with concave curvature type sidewalls, and the second material layer includes a grating structure, a waveguide, and a transition region including sidewalls with convex curvature existing between the grating structure and the waveguide.

[0093] The features of the above embodiments are beneficial for those skilled in the art to understand the present invention. Those skilled in the art should understand that the present invention can be used as a basis to design and modify other processes and structures to achieve the same purpose and / or the same advantages of the above embodiments. Those skilled in the art should also understand that these equivalent substitutions do not depart from the spirit and scope of the present invention, and changes, substitutions, or modifications can be made without departing from the spirit and scope of the present invention.

[0094] 100: Intermediary layer 101: First basement 103: First insulating layer 103A: First cladding layer 105: Materials 201: First Active Layer 203: First optical element 204: Grating Coupler 205: Grating Coupler Section 206: The First Curtain 209: First material layer 210: Transition Zone / Transition Section 211, 227: Sidewall 212: First Interface 213: First set of gratings 214: Second Interface 215: Waveguide Section 216, 239: Ditches 217: Second set of gratings 221: Second material layer 225: Grating 226: The Last Raster 260: Reflective layer 274: Optical Signal 275: Uncoupled optical signal 276: First Coupled Optical Signal 277: Reflected optical signals 278, 281: Coupled reflected light signals 279: Transmitted optical signals 280: Grating Coupler Structure 293: Grating Structure Part 301: Semiconductor Materials 401: Second Insulation Layer 501: First metallization layer 503: Second optical element 505: First bonding layer 507: First bonding pad 509: First Dielectric Material 511: Third optical element 600: Laser Grain 601: First Semiconductor Device 603: Semiconductor substrate 605: Active device 607: Internal Wiring Structure 609: Second bonding layer 611: Third joint pad 613: Second gap-filling material 701: Supporting substrate 703: Coupler Lens 801: Second Active Layer 803: Fourth Optical Element 900: First Optical Package 901: Through hole of the first device 903: Third bonding layer 905: Fiber Optic 909: Fourth joint pad 911: The Fifth Optical Element A1, A2: Vertex C1: Centerline D1: First Direction D2: Second Direction L1: Length W1: First width W2: Second width

Claims

1. A method for forming an optical device, comprising: An optical signal coupling material layer is formed on the coating layer; The optical signal coupling material layer is patterned to provide a geometry including a grating structure and a waveguide, wherein the grating structure includes at least one set of gratings, wherein a transition region includes a curved sidewall existing between the grating structure and the waveguide, wherein the optical signal coupling material layer is a multilayer structure, the multilayer structure including a first material layer on the cladding layer and a second material layer on the first material layer, wherein the at least one set of gratings includes a first set of gratings and a second set of gratings, the first set of gratings extending from the substrate of the first material layer along a first direction, and the second set of gratings extending from the upper surface of the second material layer along a second direction.

2. The method of claim 1, wherein the curved sidewall of the transition region originates from the end grating of the at least one set of gratings, the end grating being located at the interface between the grating structure and the transition region.

3. The method of claim 1, wherein the curved sidewall of the transition region has a concave curvature relative to a centerline extending along the length of the grating structure, the transition region, and the waveguide.

4. The method of claim 1, wherein the curved sidewall of the transition region has a convex curvature relative to a centerline extending along the length of the grating structure, the transition region, and the waveguide.

5. The method of claim 1, wherein the curved sidewall has a first curvature type, and the second material layer includes a tapered transition region having a sidewall of a second curvature type, wherein the first curvature type is convex curvature, and the second curvature type sidewall is concave curvature.

6. The method of claim 1, wherein forming the optical signal coupling material layer comprises: Forming a first material layer on the cladding layer, wherein patterning the optical signal coupling material layer includes patterning the first material layer to provide the geometry including the grating structure and the waveguide, wherein the grating structure includes the at least one set of gratings, and the transition region including the curved sidewalls exists between the grating structure and the waveguide, the curved sidewalls having a first curvature type; forming a second material layer on the first material layer; and patterning the second material layer to include a tapered transition region having sidewalls of a second curvature type different from the first curvature type.

7. An optical device, comprising: Coating layer; And an optical signal coupling material layer, on the cladding layer, the optical signal coupling material layer including a grating structure and a waveguide, wherein the grating structure includes at least one set of gratings, wherein a transition region includes a sidewall with a concave curvature, the sidewall existing between the grating structure and the waveguide, wherein the optical signal coupling material layer is a multilayer structure, wherein the multilayer structure includes a first material layer on the cladding layer and a second material layer on the first material layer, wherein the at least one set of gratings includes a first set of gratings extending from the substrate of the first material layer along a first direction, and a second set of gratings extending from the upper surface of the second material layer along a second direction, wherein the first set of gratings having the first direction and the second set of gratings having the second direction provide a bidirectional grating structure.

8. The optical device of claim 7, wherein the first material layer includes a linear transition region and the second material layer includes the grating structure, the grating structure including the at least one set of gratings, the waveguide, and the transition region having sidewalls with the concave curvature.

9. The optical device of claim 7, wherein the first material layer includes the grating structure, the waveguide, and the transition region including the sidewalls having concave curvature, the sidewalls existing between the grating structure and the waveguide, and the second material layer includes a tapered transition region having sidewalls of convex curvature type.

10. An optical device, comprising: Coating layer; And an optical signal coupling material layer, on the cladding layer, the optical signal coupling material layer includes a grating structure and a waveguide, wherein the grating structure includes at least one set of gratings, wherein a transition region includes a sidewall with a convex curvature, the sidewall being present between the grating structure and the waveguide, wherein the optical signal coupling material layer is a multilayer structure, wherein the multilayer structure includes a first material layer on the cladding layer and a second material layer on the first material layer, wherein the at least one set of gratings includes a first set of gratings extending from the substrate of the first material layer along a first direction, and a second set of gratings extending from the upper surface of the second material layer along a second direction, wherein the first set of gratings having the first direction and the second set of gratings having the second direction provide a bidirectional grating structure.

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