APPARATUS AND METHOD OF MANUFACTURING A VERTICALLY DISAGGREGATED PHOTONIC DEVICE

Apparatus and methods of manufacture are disclosed. In one example the apparatus includes a first substrate that has a first surface, a first optical waveguide that is at or near the first surface of the first substrate, a second substrate that has a second surface. The second substrate is coupled to the first substrate at an interface. The apparatus also has a photonic integrated circuit (PIC) with a portion at or near the second surface. The PIC is in alignment with and optically coupled to the first optical waveguide across the interface.

FIELD OF THE INVENTION

The invention relates to hybrid bonding of photonic devices.

BACKGROUND

Recent advances in hybrid bonding technology for emerging high-volume wafer-to-wafer and die-to-wafer 3-D stacking provide sub-micron alignment accuracy in the X, Y (laterally) directions and the Z (vertically) direction between the two wafers/dies that are hybridly bonded at an interface. Additionally, hybrid bonding allows essentially zero die gap in the Z direction with covalent bonding across the interface.

The figures are not to scale. Instead, the thickness of the layers or regions may be enlarged in the drawings. Although the figures show layers and regions with clean lines and boundaries, some or all of these lines and/or boundaries may be idealized. In reality, the boundaries and/or lines may be unobservable, blended, and/or irregular. In general, the same reference numbers will be used throughout the drawing(s) and accompanying written description to refer to the same or like parts. As used herein, unless otherwise stated, the term “above” describes the relationship of two parts relative to Earth. A first part is above a second part, if the second part has at least one part between Earth and the first part. Likewise, as used herein, a first part is “below” a second part when the first part is closer to the Earth than the second part. As noted above, a first part can be above or below a second part with one or more of: other parts therebetween, without other parts therebetween, with the first and second parts touching, or without the first and second parts being in direct contact with one another. Notwithstanding the foregoing, in the case of a semiconductor device, “above” is not with reference to Earth, but instead is with reference to a bulk region of a base semiconductor substrate (e.g., a semiconductor wafer) on which components of an integrated circuit are formed. Specifically, as used herein, a first component of an integrated circuit is “above” a second component when the first component is farther away from the bulk region of the semiconductor substrate than the second component. As used in this patent, stating that any part (e.g., a layer, film, area, region, or plate) is in any way on (e.g., positioned on, located on, disposed on, or formed on, etc.) another part, indicates that the referenced part is either in contact with the other part, or that the referenced part is above the other part with one or more intermediate part(s) located therebetween. As used herein, connection references (e.g., attached, coupled, connected, and joined) may include intermediate members between the elements referenced by the connection reference and/or relative movement between those elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and/or in fixed relation to each other. As used herein, stating that any part is in “contact” with another part is defined to mean that there is no intermediate part between the two parts.

DETAILED DESCRIPTION

High-bandwidth interconnects depend on photonic devices such as integrated lasers, resonant-ring modulators (RRMs), and resonant-ring photodetectors (RRPDs) for optical signaling over optical waveguides, connectors, and/or fibers at one or more (e.g., a combination of) specific wavelengths. The resulting photonic dies or optical integration can be expensive. For example, a large area can be required for waveguide routing to optical connectors at the edge of a package or outside a thermal solution such as a heat spreader/sink.

An optical signal is defined herein as an electromagnetic signal in the optical spectrum. The optical spectrum is defined herein as a light portion of the electromagnetic spectrum across a range of wavelengths including infrared, the visible spectrum, ultraviolet, and any other wavelengths that can be utilized for signaling purposes.

In some examples, precise 3-D semiconductor die stacking by hybrid bonding is utilized to bring a separately fabricated optically active region/element of a one or more photonic devices disposed in one die into a required close proximity to an optical waveguide disposed in another die. In different examples, a given die may be referred to also as a substrate or wafer and will be mainly referred to as a substrate in further examples below. The optically active region/element of a given photonic device in different examples can be any one of an optically active region of a hybrid laser, the resonant ring of a RRM, the resonant ring of a RRPD, or the input/output waveguide of any other needed photonic device.

As used herein, an “optically active” region or element of a photonic device is defined as a region or element of a device that is capable of actively performing functions on or with optical signals (e.g., light, electromagnetic waves), or is capable of having multiple functional states that are actively switched between, or is capable of being powered from a voltage (e.g., a bias voltage) to perform a function. An optically active region of a photonic device may be referred to as a photonic integrated circuit (PIC). In some examples, a modulator, a photodetector, and a hybrid laser are herein considered optically active elements (e.g., photonic integrated circuit elements).

As used herein, an “optically passive” region or element is defined as a region or element of a photonic device with a structure that does is not capable of performing the active functions described above related to optically active regions or elements. For example, an optically passive element may guide light (e.g., carry an electromagnetic wave, reflect an electromagnetic wave, etc.) but does not actively perform functions on that light. In some examples, waveguides and static mirrors are herein considered optically passive elements.

In many examples, the optical waveguide is disposed in a substrate that is used primarily for optical routing. A region referred to as optically active is defined herein as a photonic integrated circuit (PIC). The The vertical separation of different optical elements of photonic devices disposed in separately fabricated substrates can be referred to as vertical disaggregation. Hybridly bonding these substrates together in a precise 3-D stacked configuration couples the optical elements together, aggregating (e.g., photonically coupling) the optical elements to create fully functional photonic devices. Hybrid bonding provides sub-micron alignment accuracy between the two substrates that are hybridly bonded at an interface. Hybrid bonding allows dense electrical connections as well as optical connections to be made at the same time across the interface, for example to facilitate electrical signal connectivity and optoelectronic control. As a result, the substrate (sometimes referred to as a base die) including the optical waveguide can be optimized for waveguiding, performance, and/or cost. For example, the substrate can be a glass substrate with an interface to external optical fibers.

FIG.1is a schematic illustration of two example semiconductor substrates100,102that include vertically disaggregated elements of a photonic device. In the example ofFIG.1, the substrates100,102are separate. As such,FIG.1depicts the substrates100,102at an interim point of fabrication. The example illustration inFIG.1is shown in a modified isometric view for clarity. The isometric view illustrates a volumetric three-dimensional (X,Y,Z) space where the X-direction is measured left and right, the Y-direction is measured forward and backward, and the Z-direction is measured up and down (as shown by the coordinate axes in the upper left).

In the illustrated example, the first substrate100and second substrate102include a semiconductor material. In different examples, the semiconductor material may be silicon, gallium arsenide, germanium, glass, or one or more other known semiconductor materials. The first substrate100may be referred to as a base die. In some examples, the first substrate includes optically passive elements.

The example first substrate100includes a first optical waveguide104and a second optical waveguide106. For illustrative purposes inFIG.1, two different examples of vertically disaggregated photonic devices are shown. Specifically, the example illustrates the first substrate100including two optical waveguides104,106, but in other examples, there may be one optical waveguide or three or more optical waveguides included in the first substrate100. Each waveguide104,106included in the example first substrate100guide electromagnetic waves over its distance. An optical waveguide is an example of an optically passive element. In different examples, the first and second optical waveguides104and106are implemented by optical fiber, transparent dielectrics made of plastic or glass, and/or any other known optical waveguide material.

In this example, the first and second optical waveguides104and106are disposed in the first substrate100when the substrate100is fabricated. In another example, the first and second optical waveguides104and106are added to the first substrate100after the substrate is fabricated. As used herein, “being disposed in the first substrate100” refers to the first and second optical waveguides104and106being located within the volumetric three-dimensional space of the example first substrate100. As illustrated in the example inFIG.1, the upper surfaces of the first and second optical waveguides104and106are generally at the same (or a substantially similar) planar Z-height. “Substantially similar” in planar Z-height refers to being similar enough to allow for hybrid bonding to effectively take place across at least a surface region of the example first substrate100where the surface region includes both a portion of an optical waveguide (104and/or106) and a portion of the semiconductor material of the example first substrate100adjacent to the portion of the optical waveguide (104and/or106). Additionally, in the illustrated example inFIG.1the first and second optical waveguides104and106are significantly shallower in Z-height than the height of the example first substrate100. In other examples, the delta in Z-height between the first and second optical waveguides104and106and the Z-height of the first substrate100is smaller than shown inFIG.1(e.g., the optical waveguide and the substrate could have equal Z-heights).

In the illustrated example inFIG.1, the second substrate102includes a first optically active photonic device108and a second optically active photonic device110. In the illustrated example inFIG.1, each optically active photonic device is a resonant ring modulator (RRM) that includes an optical waveguide ring element110. To simplify the focus ofFIG.1, not all elements of RRMs are shown. Additional elements in RRMs are described below in reference toFIG.5.

For illustrative purposes to show two different examples of vertically disaggregated photonic devices, the example second substrate102includes two RRMs, RRM108and RRM110. RRM108is oriented parallel (in a horizontal orientation) in an X,Y plane of the second substrate102parallel with the X,Y plane of the first substrate100. The second substrate102of this example is a chiplet substrate.

The RRM110is oriented in a vertical orientation perpendicular to both the X,Y plane of the second substrate102. In the illustrated example there are two RRMs included in the second substrate102. In other examples, there can be one RRM or three or more RRMs included in the second substrate102. As illustrated in the example inFIG.1, at least a portion of the lower surfaces of the RRM108and the RRM110are generally at the same (or a substantially similar) planar Z-height as the lower surface of the second substrate102. In other examples, there are one or more additional optically active photonic devices other than RRMs in the substrate102.

Hybrid bonding is utilized to couple the first substrate100to the second substrate102. Specifically, in reference to the example substrate orientation illustrated inFIG.1, the upper surface of the first substrate100is positioned to be hybridly bonded to the lower surface of the second substrate102.

In order for hybrid bonding to effectively couple an RRM to a waveguide, precise disposition of the RRMs and optical waveguides within their respective substrates100,102is needed to align regions that are to be hybridly bonded. For example, accurately disposing the horizontal RRM108at a specific X,Y location (112,114) of the second substrate102allows alignment during hybrid bonding to a corresponding region at X,Y distances (118,120) from a specific point such as a corner of the substrate100. And accurately disposing the vertical RRM110at a specific X,Y location (112,116) of the second substrate102allows alignment during hybrid bonding to a corresponding region at X,Y distances (118,122) from a specific point such as a corner of substrate102. In many examples, one of several known alignment methods are utilized to achieve accurate positioning of the RRMs108,110and corresponding waveguides104,106.

Although the first substrate100is shown in the illustrated example as being the same size as the second substrate102, in some examples the two substrates are not the same size. In many examples, the first substrate100is larger than the second substrate102for cost effectiveness and routing efficiency purposes of the first and second optical waveguides104and106.

FIG.2is a schematic illustration of the example semiconductor substrates100,102ofFIG.1after hybrid bonding. The example illustration inFIG.2is shown in a modified isometric view for clarity.

FIG.1illustrated the first substrate100and the second substrate102prior to hybrid bonding.FIG.2illustrates the substrates100,102after a hybrid bonding process has occurred. With the hybrid bonding complete, the upper surface of the first substrate100and the lower surface of the second substrate102are physically coupled (i.e., attached) at a first interface200. The first interface200is the bonding surface and/or material that couples the two substrates together. Hybrid bonding allows the aforementioned surfaces of the first substrate100and the second substrate102, as well as elements disposed in those substrates at or near the bonded surfaces to be in contact and/or in extremely close proximity to one another. As a result, elements disposed at or near the upper surface of the first substrate100can be coupled (i.e., hybridly bonded) to corresponding optical and/or electrical elements at or near the lower surface of the second substrate102within 0.5 to 1.0 micrometers (μm) from each other (i.e., hybrid bonding proximity). In the illustrated example, a region of the horizontal RRM108is coupled within a hybrid bonding proximity to a region of the first optical waveguide104and a region of the vertical RRM110is coupled within a hybrid bonding proximity to a region of the second optical waveguide106.

FIG.3is a schematic illustration of a cross section of portions of the example semiconductor substrates100,102ofFIGS.1and2after hybrid bonding. In the illustrated example, the cross section shown is a close-up view of a region of the first substrate100that includes the second waveguide106and a region of the second substrate102that includes the vertical RRM110. An example of the first interface200is also shown.

In the illustrated example, when the first substrate100is hybridly bonded to the second substrate102, the first optical waveguide106becomes optically coupled to the vertical RRM110. As used here, “Optically coupled” is defined to mean two or more elements are in such proximity to each other such that an optical signal transmitted in one element can affect an optical signal transmitted in the other element, and/or the optical signal in one element can transfer into the other element. For example, an optical signal being transmitted through the second optical waveguide106can be affected by an optical signal being transmitted through the vertical RRM110.

In the illustrated example, the interface between the two substrates has a thickness of 0.5 to 1.0 μm (shown with the measurement300). In other examples, the thickness of the interface is less than 0.5 μm. In yet other examples, the thickness of the interface200is more than 1.0 μm, although as thicknesses increase significantly the effectiveness of the optical coupling of the elements decreases.

FIG.4is a schematic illustration of an example base semiconductor substrate with a meandering optical waveguide hybridly bonded to multiple chiplet substrates402,404,406,408, and410. The example illustration inFIG.4is shown in a top-down view. The dotted lines denote portions of waveguides and other transmission lines that are obscured below substrates that are closer to the viewer's relative position.

In the illustrated example, the chiplet substrates (402,404,406,408, and410) are hybridly bonded to the top surface of the base substrate400. An interface is located between each chiplet substrate and the corresponding area of the substrate400(the interfaces are not visible inFIG.4). In different examples, each chiplet substrate (402-410) may have unique functionality or may have the same functionality as one or more of the other chiplet substrates. In the illustration shown inFIG.4, the “top” surface or the “upper” surface of the example base substrate400is the surface shown facing a viewer of the illustration. Additionally, in the illustration shown inFIG.4, the “lower” surface or “bottom” surface of each example chipset substrate (402-410) is the surface facing away from the viewer of the illustration. Thus, as shown in the illustrated example, the top surface of the base substrate400is hybridly bonded to the bottom surfaces of the respective chiplet substrates (402-410). An optical waveguide412is disposed in the example base substrate400.

In the illustrated example, the optical waveguide412traverses a serpentine or meandering path (i.e., turning back and forth across the base substrate400). Having the optical waveguide412disposed in this manner allows a greater distance of the optical waveguide to be exposed to the top surface of base substrate400. This, in turn, allows a greater number of chiplet substrates to be hybridly bonded to the optical waveguide412over a surface area on the example base substrate400. Although inFIG.4, the path is serpentine, in other examples, the meandering layout of the optical waveguide412can be any other layout configuration, such as using 90-degree right angle turning structures (e.g., mirrors placed at angles) instead of curved turns or a layout of chiplet substrates that are not parallel to each other.

In the example ofFIG.4, one or more optically active photonic device elements are disposed in each chiplet substrate (402-410). In the illustrated example, there are four optically active photonic device elements disposed in each chiplet substrate (402-410). For example, in chiplet substrate410, there are optically active photonic device elements414,416,418, and420. In some examples, the elements414-420are resonant rings of either RRMs or RRPDs. In other examples, the elements414-420are optically active regions of a hybrid laser. In yet other examples, elements414-420are the input/output waveguides of one or more other photonic devices. In some examples, each chiplet substrate402-410has a homogeneous set of optically active photonic device elements (i.e., all elements shown in a given chiplet substrate, such as elements414-420in chiplet substrate410, are the same type of element). In other examples, the set of optically active photonic device elements in a given chiplet substrate are heterogeneous. For example, elements414and418can be resonant rings and elements416and420can be input/output waveguides. Some or all of the chiplet substrates may differ from one or more of the other chiplet substrates.

As discussed above, optically active photonic device elements utilize at least one electrical input. The electrical current applied on a given input can be modified to cause the optically active photonic device element to perform its function, change its state, and/or change its function. In other examples, the voltage applied on a given input changes. In some examples, a specific region of the optical waveguide includes a resonant ring with metallic (e.g., copper) leads on one or more sides of the region of the ring. One or more gaps can be left in the ring with a metallic lead on each side of the gap. The gap can be filled with an electro-optical material (e.g., a polymer). This electro-optical material can change the refractive index of the ring depending upon the amount of electrical current applied to the leads. The effective propagation constant (i.e., the refractive index) of the ring is dependent upon the refractive index of the material. The electrical signal applied to the ring can be used to tune the ring.

As illustrated inFIG.4, there are electrical inputs422,424,426, and428disposed in the base substrate400. The electrical inputs422,424,426,428are for the optically active elements414,416,418, and420respectively. In many examples, each electrical input can include multiple leads to allow for a complete circuit to transmit the electrical signal described above. The illustrated example shows electrical inputs422-428disposed at a portion of the surface of the base substrate400, for ease of visual explanation. In many other examples, electrical inputs are disposed vertically down into base substrate400directly underneath a chiplet substrate410using vias or other electrical transmission line routing mechanisms. Additionally,FIG.4only shows electrical inputs422-428for chiplet substrate410, but there are electrical inputs for each of the other chiplet substrates (402,404,406, and408).

Other optically active photonic device elements also utilize electrical inputs. For example, the photodetector element of a RRPD can be considered an optically active device. Photodetectors often include a semiconductor diode with a p-n junction and require a source of energy, a reverse bias voltage, to operate.

FIG.5is a schematic illustration of a cross-sectional view of a base semiconductor substrate hybridly bonded to a chiplet substrate. In the illustrated example, base substrate500is hybridly bonded to the chiplet substrate502at an interface504. In many examples, the interface504is a co-planar SiO2interface. The portion of the hybrid bonding process described above focused mainly on the optical coupling capabilities, which can also be referred to as solid state bonding. The solid-state bonding phase allows for elements of optically active photonic devices, such as RRM506inFIG.5, to be optically coupled to optical waveguides, such as waveguide508, across interface504, through a covalent bond (e.g., SiO2to SiO2).

In many examples, hybrid bonding of the optical and electrical connections are performed in a serial manner (e.g., the optical connections are hybridly bonded first and then the electrical connections are hybridly bonded second). In the illustrated example, the first phase of hybrid bonding couples corresponding optical elements to form a solid-state bond across the interface504. Once the solid-state bond phase has completed, then one or more electrically conductive (e.g., copper) pads are coupled across the example interface504during a second phase of the hybrid bonding process. In other examples, a different electrically conductive material other than copper is used in the construction of the pads. During the initial solid-state bonding phase, the copper pads will not bond to each other because there remains a physical gap in between the copper pads that are slightly recessed (e.g., concave). In the illustrated example, during the second phase, the copper pad510and a copper pad at the end of the electrically conductive line512are bonded across the interface504through an annealing process.

When the copper pads (e.g.,510and the end of512) have bonded, then the example optically active photonic device element (e.g., RRM506) is electrically coupled to an electrically conductive input. The electrically conductive input enables a charge to be introduced to a region514at or near the RRM506. In some examples, the region514is a charge modulated region that adjusts a condition (e.g., state) of the RRM506when an electric charge is applied across a pad510and a line512. The charge modulated region includes an electro-optical material in many examples. The electro-optical material can be a polymer or another type of material that is responsive to an applied electric field (e.g. a voltage applied to the material).

In some examples, the electrical line512includes two electrically conductive lines (such as vias or other metal leads). The electro-optical material can fill a region or space that defines a gap between the ends of the two electrically conductive lines (512). When a voltage is applied to the lines512, the electrical potential across the gap creates a charge in the electro-optical material and completes an electric circuit between the lines512. In the example shown inFIG.5, the RRM506modulates to a frequency that is controlled by the electric field applied at the region514. The modulated frequency can be controlled by changes in the applied voltage. Thus, the example RRM506can become a filter at an electromagnetic wavelength (i.e., a light filter) that is either dynamically adjustable using an adjustable voltage or is set with a fixed voltage. As shown in the illustrated example, the other three optically active photonic device elements displayed in the chiplet substrate502(shown as resonant rings) also have at least one pad, one line, and a charge modulated region in proximity to each ring.

In some examples, each of the RRMs in the chiplet substrate502modulates a different frequency in a transmitted optical signal carried by waveguide508. In some examples, one or more additional ring resonators that do not have a coupled modulator (i.e., optically passive ring resonators). A passive ring resonator is tuned to a specific frequency based on the circumference/diameter of the ring and the ring material. In other examples, instead of RRMs in chiplet substrate502, there may alternatively be RRPDs (e.g., in a receiver chiplet substrate), hybrid laser elements (e.g., in a transmitter chiplet substrate), input/output waveguide elements, and/or any other optically active photonic device elements, and/or passive optical elements. Additionally, in some examples there may be either a homogeneous or heterogeneous set of optically active photonic device elements per chiplet substrate. In other examples, there may be a combination of active and passive photonic device elements per chiplet substrate. In yet other examples, there may be other electrical circuits per chiplet substrate in addition to one or more active and/or passive photonic device elements.

The example interface504has a sub-micron thickness because the surfaces of the substrates to be bonded are polished to a precise plane through a chemical mechanical polishing (CMP), which allows for close contact at the interface504. The optical waveguide508and the optically active elements of photonic devices, such as vertical RRM506are disposed at or close enough to the surfaces of their respective substrates to allow photons to be sent across the interface504. As described above, this can be referred to being “optically coupled” across the interface504.

In other examples, a second waveguide similar to the optical waveguide508is disposed in the chiplet substrate502at or near its surface at the interface504. The second waveguide allows photons to transfer directly from the optical waveguide508in the base substrate500to the second waveguide in the chiplet substrate502.

In many examples, the ring resonators are disposed vertically in the chiplet substrate502to pack more ring resonators in a smaller (X, Y) area of the substrate since a good portion of the RRM structure is in the vertical direction and, therefore, can extend away from the interface in the Z-direction. In the illustrated example inFIG.5, four RRMs are shown. In other examples, there may be more or less RRMs in chiplet substrate502than the four shown inFIG.5.

While only vertical ring resonators are shown in the illustrated example inFIG.5, in many other examples the chiplet substrate502alternatively includes one or more horizontal RRMs, such as the horizontal RRM108inFIG.1. An example horizontal optical waveguide ring, such as the ring of the RRM108inFIG.1, can be fabricated in a horizontal planar fashion on a wafer and then disposed in that same plane orientation along the X,Y axes in a substrate.

An example vertical optical waveguide ring can be fabricated in multiple ways. For example, a vertical optical waveguide ring, such as the RRM506inFIG.5, can begin the fabrication process similarly to a horizontal optical waveguide ring (i.e., being fabricated in a horizontal planar fashion on a wafer). But prior to disposition in a substrate, the fabricated ring can then be rotated from a parallel position to a perpendicular position relative to the X,Y plane of the substrate (502in this example). At that point the substrate is fabricated with the optical waveguide ring dispositioned in a vertical manner within it.

In another example, the optical waveguide ring may not be round, but rather a closed square, rectangle, or oval loop that is oriented vertically (i.e., perpendicular to the X,Y plane of the substrate). An example square optical waveguide ring516is shown inFIG.5. To fabricate this example ring, In this example, a first optical waveguide layer is fabricated (shown as waveguide518). Then a second optical waveguide layer is fabricated (shown as waveguide520). Then two optical vias (522and524) are coupled to the ends of the two waveguides518and520to complete the loop. In many examples, each coupling between an optical via and an optical waveguide utilizes a 90-degree turning component, such as component526. In different examples the 90-degree turning component are mirrors, gratings, or other components that can turn an optical signal (e.g., 90-degrees) at a coupling location.

While the square ring is shown in the example inFIG.5next to the round rings, in many examples, a homogeneous set of rings that are either all round or all rectangular/square are disposed in the substrate502.

In some examples, one or more of the RRMs have a control input that is used to fine tune the resonance of the resonance ring. For example, fine tuning a given ring may be accomplished by a micro-heater element coupled to the ring to change the frequency of the ring. In another example, the voltage applied to the electro-optical polymer can also be used to fine tune the frequency of the ring.

FIG.6is a schematic illustration of a cross-sectional view of a 3-D stack of three semiconductor substrates. The illustrated example is similar to the example shown inFIG.5with the exception of the electrically conductive input source location and disposition.

Specifically, in the illustrated example ofFIG.6, the base substrate600is hybridly bonded to chiplet substrate602at an interface604. The hybrid bond at the interface604allows optically active photonic device elements, such as RRM606(as well as the three other RRMs shown) to be optically coupled to optical waveguide608. In the example inFIG.6, unlike the example inFIG.5, the RRMs are electrically coupled to electrically conductive pads, such as the pad610, that are disposed on a third substrate610. In different examples, the substrate610may be a compute die/substrate, an input/output (I/O) controller substrate, a custom controller substrate, or any other type of substrate that could be packaged in a 3-D substrate (i.e., die) stack with the base substrate600and the chiplet substrate602.

There are many reasons why it may be advantageous to have the electrical input to the RRMs originate from a substrate other than the base substrate600, such as layout and manufacturing efficiencies, costs, and customizations, among other reasons. Therefore, in the illustrated example, the first pad612(along with the other pads shown but not labeled in third substrate610) are coupled to the upper surface of the chiplet substrate602. Because there is no optical coupling necessary between the chiplet substrate602and the third substrate610, hybrid bonding is not necessary, although it could be employed. In other examples, other die stacking techniques are utilized, such as simple solder bumps (or any other known die stacking/coupling technique) to couple the electrically conductive pads at the bottom surface of the third substrate610, with the electrically conductive pads at the top surface of the chiplet substrate602. An example of the coupling is shown where the first pad612is coupled to the pad at the end of the electrical line (e.g., via)614.

As inFIG.5, each coupled pair of pads inFIG.6provides an electrical input to an electro-optically active region disposed on or near a RRM. For example, electro-optically active region616is supplied voltage from the first pad612through the electrical line614. Three other electro-optically active regions are shown inFIG.6but not labeled. Other examples include other optically active photonic device elements and may also exhibit more electrical inputs per device element, depending on the complexity of the needed control functionality.

In some examples, the base substrate600is not limited to optically passive elements, but also can also contain one or more optically active photonic device elements. For example, the base substrate could have one or more optically active photodetectors disposed within it. The specific disaggregation of photonic device elements across the multiple substrates is an application specific layout decision for each package.

FIG.7is a schematic illustration of a hybrid laser array transmission subsystem. The viewpoint ofFIG.7is top-down.

The illustrated example shows a base substrate700hybridly bonded to four hybrid lasers (702,704,706, and708). More specifically, the optically active element of each of the four hybrid lasers is hybridly bonded to the base substrate700. The example optical waveguides710,712,714, and716are disposed in the base substrate700. In the example shown, the waveguides710-716originate from a location at the interface between each of the hybrid lasers702-708and the base substrate700. The hybrid lasers702-708transmit optical signals along the optical waveguides710-716.

When the signals in the waveguides reach the example chiplet substrates718,720,722, and724, respectively, certain wavelengths are filtered out of the signals. The filtering occurs by modulating the resonant frequency of each RRM disposed in each chiplet substrate. For example, the RRMs730and732in chiplet substrate718are each utilized as a filter of an electromagnetic wave at a certain frequency. As the frequency modulates off and on, a data signal can be created at that frequency.

In many examples, once the signals pass the RRMs they are then combined in a combiner chiplet substrate726and are sent as a combined optical signal across a fiber connector728. The combiner combines individual signals coming from each waveguide (702-708) into a single optical signal on a single fiber waveguide. In other examples, a tree of combiners combines many signals into fewer signals and then fewer signals into one signal, the one signal incorporating all of the signals that were combined at every combination stage.

FIG.8is a schematic illustration of a cross-section of the 3-D stack of substrates discussed above inFIG.7regarding a hybrid laser array transmission subsystem.FIG.8shows a cross-section of a greater portion of the 3-D stack than what was shown inFIG.7. All components that were shown inFIG.7and are also shown inFIG.8maintain their numbering fromFIG.7. Additionally, the view of the substrates in the cross-section shows a significant air gap between each one for sake of illustration, but the air gaps may not be present.

As previously discussed above inFIG.7, the illustrated example shown inFIG.8includes a base substrate700and a hybrid laser702(hybrid lasers704-708fromFIG.7are not visible from theFIG.8viewpoint). Example optical waveguide710is shown disposed at or near the top surface of base substrate700.

The illustrated example hybrid laser702inFIG.8includes an optically active element800. The optically active element becomes operational in response to an applied voltage. The hybrid laser702of this example is hybridly bonded to the base substrate700and optically coupled to the optical waveguide710. As the optical signal is transmitted from the hybrid laser702across optical waveguide710it reaches the chiplet substrate718, which is also hybridly bonded to the base substrate700. Through the hybrid bond, the RRMs730and732are also optically coupled to the optical waveguide710and filter certain frequencies of the optical signal being transmitted across the waveguide710.

After the example optical waveguide710passes the chiplet substrate718, it reaches a 90-degree turning component to turn the optical signal perpendicular to the X,Y plane of the base substrate700. This turn is shown inFIG.8as turning up in the Z direction towards the top of the example stack. In the cross-section view, the X direction is shown as moving left or right along the dotted line denoting the waveguide710, whereas the Y direction is not able to be shown as it is oriented into/out of the paper ofFIG.8. In some examples, the 90-degree turning component may be a mirror, a grating, or any other known device capable of turning an optical signal in such a manner.

In the illustrated example, once the waveguide710passes the interface at the top surface of the base substrate700, it is then further disposed in the combiner chiplet substrate726. The waveguide710is then combined with the other optical waveguides fromFIG.7(the other waveguides are not shown inFIG.8) to generate a combined signal that is transmitted out to the fiber coupling/connector728.

In addition to the components of the stack that was shown in a top-down manner inFIG.7,FIG.8also includes additional components of the stack. For example, a compute-I/O die802is bonded to the hybrid laser702and the chiplet substrate718. The bonding method for compute-I/O die802can be any method that is functionally acceptable for the purpose needed. For example, when a hybrid bond is not needed, the compute-I/O die can be coupled to the hybrid laser702and the chiplet substrate718using solder bump bonding. Another system-level I/O chiplet substrate804is coupled to the compute-I/O die802in many examples.

WhileFIG.7andFIG.8described the transmission side of an optical signal subsystem,FIG.9is a schematic illustration of a cross-section of a 3-D stack of substrates for the receiving side of an optical signal subsystem. All similar components inFIG.9that were shown inFIG.7andFIG.8maintain their numbering from those previous figures.

The illustrated example shown inFIG.9includes an edge-receiving detector chip900that can detect optical signals from a connection at the edge of the chip as opposed to from the bottom of the chip. The term “chip” can be used interchangeably herein with die or substrate. In many examples, the detector chip900is hybridly bonded to a base substrate902. The package layout inFIG.9is able to obtain an optical signal through fiber connector728. In many examples, the signal is then routed through an optical waveguide to a 90-degree turning component904to allow each optical signal to traverse into the base substrate902.

Each optical signal is then turned 90-degrees again once in substrate902using another 90-degree turning component. After this turn, each waveguide is disposed along the X-axis of base substrate902and traverses a portion of the substrate. At a certain location down the X-axis of base substrate902, each waveguide is turned again 90-degrees, this time in the upward direction, to allow each waveguide to traverse into an example waveguide turning substrate906. Within the substrate906, another set of 90-degree turning components is used to turn each waveguide parallel again to the plane of the package components. Once turned, the waveguide then traverses from substrate906into the example detector chip900. The edge of the detector chip900, in many examples, is optically coupled to the waveguides. The optical signal, routed along the above described waveguide path, is converted into an electrical signal by an optical-to-electrical sensor and then processed in the detector chip900.

In many examples, the detector chip900is bonded (e.g., hybridly bonded, solder-bump bonded, or coupled through any other known bonding process) to compute-I/O die800. Compute-I/O die800can also be bonded/coupled to I/O substrate802and/or to any one or more other substrates in the package.

FIG.10is a schematic illustration of a cross-section of a 3-D stack of substrates for the receiving side of an optical signal subsystem. All similar components inFIG.10that were shown inFIG.7andFIG.8maintain their numbering from those previous figures.

The illustrated example shown inFIG.10includes a substrate1000with one or more RRPDs (two RRPDs are shown in the example inFIG.10). In many examples, the substrate1000is hybridly bonded to a base substrate1002. The package configuration inFIG.10includes a fiber connector728to carry an optical signal. In many examples, the signal is then routed through an optical waveguide and then through a 90-degree turning device904. As discussed above in reference toFIG.9, the turning device904turns the signal down into base substrate1002.

Once in base substrate1002, in this example, each waveguide is turned 90-degrees using 90-degree turning components. After this turn, each waveguide is disposed along the X-axis of the base substrate1002and traverses a portion of the substrate. At a certain location down the X-axis of the example base substrate1002, each waveguide, through the hybrid bonding process, is optically coupled to at least one of the optical waveguide ring elements in example substrate1000. Each ring is tuned to a resonant frequency and pulls the portion of the optical signal at that frequency into the ring, such as ring1004, which then sends that portion of the signal across another waveguide1006situated on the other side of the ring. The optical signal is then received by a photodetector component1008, which produces a photocurrent in response to the optical signal. In many examples, the photocurrent becomes an input at an optical receiver (not shown).

While an example manner of implementing the manufacturing of the structure ofFIG.3is illustrated inFIG.11, one or more of the elements, processes and/or devices illustrated inFIG.3may be combined, divided, rearranged, omitted, eliminated and/or implemented in any other way.

The method of manufacturing a vertically disaggregated photonic device by hybrid bonding starts by fabricating an optical waveguide in a first substrate (block1100). In different examples, the first substrate includes one or more known semiconductor materials. In different examples, the optical waveguide includes one or more optical waveguide materials such as silicon, glass, polymers, or any other known optical waveguide material. In different examples, the placement and shape of the optical waveguide in the first substrate may be done with any known fabrication technique designed to fabricate substrates including optical waveguides. In one example, the optical waveguide is fabricated and then the first substrate is fabricated around the optical waveguide. In another example, the first substrate is fabricated and then the optical waveguide is fabricated or placed in the first substrate. In yet another example, the first substrate and the optical waveguide are fabricated simultaneously. In some examples, at least a portion of the optical waveguide is placed at or near a surface of the first substrate. Placement of an optical waveguide “near” the surface of a substrate is defined herein as being placed close enough to the surface to allow the optical waveguide to be optically coupled to a second optical waveguide or photonic device element.

Next, the method of manufacturing continues by fabricating a second substrate with at least a portion of a photonic device (block1102). In different examples, the second substrate includes one or more known semiconductor materials. In different examples, the portion of the photonic device may be a resonant ring for a RRM or RRPD, an element of a hybrid laser, an optical input/output device, or any other known photonic device or portion thereof. In different examples, the placement and shape of the portion of the photonic device in the second substrate may be done with any known fabrication technique designed to fabricate substrates including photonic devices. In some examples, at least a portion of the photonic device is placed at or near a surface of the second substrate.

Finally, the method of manufacturing concludes by hybridly bonding the first substrate to the second substrate to optically couple at least a portion of the optical waveguide in the first substrate to at least a portion of the photonic device in the second substrate (block1104).

From the foregoing, it will be appreciated that example apparatus and methods of manufacture have been disclosed to vertical disaggregate photonic devices. The disclosed apparatus and methods of manufacture improve the efficiency of using a computing device by enabling high-bandwidth, power-efficient, and cost-optimized photonic I/O for computing products, including those computing products that are present in datacenters and high-performance computing environments. More specifically, semiconductor packages that have optical signaling can utilize the apparatus and methods of manufacture to optimize a base die for waveguiding and cost. The apparatus and methods of manufacture are accordingly directed to one or more improvement(s) in the functioning of a computer.

Although certain example apparatus and methods of manufacture have been disclosed herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all apparatus and methods of manufacture fairly falling within the scope of the claims of this patent. Further examples and combinations thereof include the following:

Example 1 includes an apparatus, comprising a first substrate, the first substrate having a first surface, a first optical waveguide at or near the first surface of the first substrate, a second substrate, the second substrate having a second surface, the second substrate coupled to the first substrate at an interface, and a photonic integrated circuit (PIC), at least a portion of the PIC at or near the second surface, the PIC in alignment with and optically coupled to the first optical waveguide across the interface.

Example 2 includes the apparatus of example 1, wherein the second substrate is hybridly bonded to the first substrate at the interface.

Example 3 includes the apparatus of example 2, wherein the first substrate is optically passive.

Example 4 includes the apparatus of example 1, further including a charge modulated region in the second substrate, the charge modulated region to adjust a state of the PIC in response to a signal.

Example 5 includes the apparatus of example 4, wherein the second substrate includes an electro-optical material in the charge modulated region of the second substrate, the electro-optical material is responsive to the signal, and at least one electrically conductive input electrically coupled to the electro-optical material.

Example 6 includes the apparatus of example 4, further including a ring resonator.

Example 7 includes the apparatus of example 6, wherein the ring resonator is a component of a ring resonator modulator.

Example 8 includes the apparatus of example 3, wherein the PIC includes a photodetector.

Example 9 includes the apparatus of example 3, wherein the PIC is a component of at least one hybrid laser.

Example 10 includes the apparatus of example 3, further including an electrical modulator input in the first substrate, the electrical modulator input electrically coupled, across the first interface, to the charge modulated region.

Example 11 includes the apparatus of example 3, further including an electrical modulator input in a third substrate, the electrical modulator input electrically coupled to the charge modulated region at a third surface of the second substrate, the third surface opposite the first interface.

Example 12 includes the apparatus of example 6, wherein the state includes a resonance frequency of the ring resonator.

Example 13 includes the apparatus of example 6, wherein the ring resonator is oriented perpendicular to a plane of the second substrate.

Example 14 includes the apparatus of example 6, wherein the ring resonator is oriented parallel to a plane of the second substrate.

Example 15 includes a method of assembling a vertically disaggregated photonic device, the method comprising fabricating a first substrate with an optical waveguide near a first surface of the first substrate, the waveguide is a first part of the vertically disaggregated photonic device, fabricating a second substrate with a photonic integrated circuit (PIC) at or near a second surface of the second substrate, the PIC is a second part of the vertically disaggregated photonic device, and hybridly bonding the first substrate to the second substrate with the optical waveguide and the PIC aligned and optically coupled to assemble the vertically disaggregated photonic device.

Example 16 includes the method of example 15, wherein the fabricating of the second substrate further includes fabricating a planar optical waveguide ring on a wafer, and positioning the planar optical waveguide ring in the second substrate in a perpendicular position relative to a horizontal plane of the second substrate, the horizontal plane parallel to the interface, wherein the planar optical waveguide ring is at least a portion of the PIC.

Example 17 includes the method of example 15, wherein the fabricating of the second substrate further includes fabricating a first optical waveguide layer in the second substrate, fabricating a second optical waveguide layer in the second substrate, coupling a first optical via to a first end of the first optical waveguide and to a first end of the second optical waveguide, and coupling a second optical via to a second end of the first optical waveguide and to a second end of the second optical waveguide such that the first and second optical waveguides and the first and second optical vias form an optical waveguide ring, wherein the optical waveguide ring is at least a portion of the PIC.

Example 18 includes the method of example 15, further including fabricating 90-degree turning components to couple the first and second optical vias to the first and second optical waveguides, respectively.

Example 19 includes an apparatus, comprising a semiconductor device package, the semiconductor device package including a first substrate, the first substrate having a first surface, a first optical waveguide at or near the first surface of the first substrate, a second substrate, the second substrate having a second surface and a third surface, the second substrate coupled to the first substrate at an interface, a photonic integrated circuit (PIC), at least a portion of the PIC at or near the second surface, the PIC in alignment with and optically coupled to the first optical waveguide across the interface, and a third substrate, the third substrate coupled to the second substrate at the third surface, the third surface opposite the first interface.

Example 20 includes the apparatus of example 19, wherein the second substrate is hybridly bonded to the first substrate at the interface.

Example 21 includes the apparatus of example 19, further including a charge modulated region in the second substrate, the charge modulated region to adjust a state of the PIC in response to a signal.

Example 22 includes the apparatus of example 21, wherein the second substrate includes an electro-optical material in the charge modulated region of the second substrate, the electro-optical material is responsive to the signal, and at least one electrically conductive input electrically coupled to the electro-optical material.

Example 23 includes the apparatus of example 22, further including an electrical modulator input in the third substrate, the electrical modulator input electrically coupled to the charge modulated region at a third surface of the second substrate, the third surface opposite the first interface.

Example 24 includes the apparatus of example 19, further including a ring resonator.

Example 25 includes the apparatus of example 24, wherein the ring resonator is a component of a ring resonator modulator.

Example 26 includes the apparatus of example 20, wherein the PIC includes a photodetector.

Example 27 includes the apparatus of example 20, wherein the PIC is a component of at least one hybrid laser.

Example 28 includes the apparatus of example 19, wherein the third substrate is a compute die.

Example 29 includes the apparatus of example 19, wherein the third substrate is an input/output controller.

Example 30 includes the apparatus of example 19, wherein the third substrate is solder bump bonded to the second substrate.

Example 31 includes the apparatus of example 19, wherein the third substrate is hybridly bonded to the second substrate.