Photonic communication platform

Abstract

A photonic communication platform is described, thereby making the scaling of memory capacity and bandwidth far beyond the possibility of conventional computing systems. Some embodiments provide a photonic communication platform involving the use of a photonic module. Each photonic module includes programmable photonic circuitry for optically communicating the module with other modules based on the need of a particular application. The inventor developed architecture relies on the use of a common photomask group (or at least one generic photomask) to fabricate multiple photonic modules in a single wafer. Optical or electronic devices may be used to link photonic modules in multiple wafers together into a communication platform.

Description

[0001] This application is a divisional application of the application with application number 202080019018.X, application date March 5, 2020, and invention name “Photonic Communication Platform”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Serial No. 62 / 961,448, filed on January 15, 2020, with Attorney Docket No. L0858.70013US02, and entitled “PHOTONICS COMMUNICATIONS PLATFORM WITH SINGLE LITHOGRAPHIC MASK SET,” which is hereby incorporated by reference in its entirety.

[0004] This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Serial No. 62 / 923,889, filed on October 21, 2019, with Attorney Docket No. L0858.70013US01, and entitled “PHOTONICS COMMUNICATIONS PLATFORM WITH SINGLE LITHOGRAPHIC MASK SET,” which is hereby incorporated by reference in its entirety.

[0005] This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Serial No. 62 / 814,444, filed on March 6, 2019, with Attorney Docket No. L0858.70013US00, and entitled “PHOTONICS COMMUNICATIONS PLATFORM WITH LITHOGRAPHIC MASK SET,” which is hereby incorporated by reference in its entirety. Technical Field

[0006] The present application relates to photonic communication platforms and related methods. Background Art

[0007] A computer system includes a random access memory (RAM) for storing data and machine code. RAM is typically a volatile memory, so the stored information is lost when power is removed. In modern implementations, the memory is in the form of an integrated circuit. Each integrated circuit includes a plurality of memory cells. In order to be able to access the stored data and machine code, the memory is in electrical communication with the processor. Typically, these electrical communications are implemented as metal traces formed on a substrate on which the memory and processor are arranged. Summary of the invention

[0008] Some embodiments relate to a photonic system including a plurality of photonic modules, the plurality of photonic modules including at least a first photonic module and a second photonic module patterned according to at least one common photomask. Each of the first photonic module and the second photonic module includes a first boundary and a second boundary; an optical distribution network; a first optical waveguide optically coupling the optical distribution network to a first adjacent photonic module of the plurality of photonic modules, the first adjacent photonic module being adjacent to the first boundary; and a second optical waveguide optically coupling the optical distribution network to a second adjacent photonic module of the plurality of photonic modules, the second adjacent photonic module being adjacent to the second boundary.

[0009] In some embodiments, the first boundary and the second boundary are opposite to each other.

[0010] In some embodiments, the first optical waveguide and the second optical waveguide are patterned according to at least one common photomask.

[0011] In some embodiments, each of the first photon module and the second photon module further includes an out-of-plane optical coupler optically coupled to the optical distribution network.

[0012] In some embodiments, the optical distribution network is configured to selectively place a first adjacent photon module in optical communication with a second adjacent photon module.

[0013] In some embodiments, each of the first photon module and the second photon module is patterned according to a common photomask set, wherein at least one common photomask is part of the common photomask set.

[0014] In some embodiments, each of the first photon module and the second photon module further includes: a third boundary and a fourth boundary, wherein the first boundary and the second boundary are opposite to each other, and the third boundary and the fourth boundary are opposite to each other; a third optical waveguide that optically couples the optical distribution network to a third adjacent photon module among the plurality of photon modules, the third adjacent photon module being adjacent to the third boundary; and a fourth optical waveguide that optically couples the optical distribution network to a fourth adjacent photon module among the plurality of photon modules, the fourth adjacent photon module being adjacent to the fourth boundary.

[0015] In some embodiments, the optical distribution network is configured to selectively place a first adjacent photon module in optical communication with a second adjacent photon module or a third adjacent photon module.

[0016] In some embodiments, the optical distribution network includes a plurality of optical switches.

[0017] In some embodiments, the first photon module and the second photon module are adjacent to each other such that the second photon module is a first adjacent photon module to the first photon module.

[0018] Some embodiments relate to a method for manufacturing a semiconductor wafer, comprising: patterning each of at least some of a plurality of photon modules on the semiconductor wafer using at least one common photomask, wherein patterning each of at least some of the plurality of photon modules comprises: patterning an optical distribution network; patterning a first optical waveguide that optically couples the optical distribution network to a first adjacent photon module of the plurality of photon modules, the first adjacent photon module being adjacent to a first boundary of the photon modules; and patterning a second optical waveguide that optically couples the optical distribution network to a second adjacent photon module of the plurality of photon modules, the second adjacent photon module being adjacent to a second boundary of the photon modules.

[0019] In some embodiments, patterning each of at least some of the plurality of photon modules includes patterning the first optical waveguide and the second optical waveguide using at least one common photomask.

[0020] In some embodiments, the method further includes cutting the semiconductor wafer to obtain a photonic substrate comprising: a first photonic module of the plurality of photonic modules; a first adjacent photonic module adjacent to a first boundary of the first photonic module; and a second adjacent photonic module adjacent to a second boundary of the first photonic module.

[0021] In some embodiments, the first boundary and the second boundary of the first photon module are opposite to each other.

[0022] In some embodiments, patterning each of at least some of the plurality of photon modules further comprises: patterning a third optical waveguide of a third adjacent photon module that optically couples the optical distribution network to the plurality of photon modules, the third adjacent photon module being adjacent to a third boundary of the photon modules; and patterning a fourth optical waveguide of a fourth adjacent photon module that optically couples the optical distribution network to the plurality of photon modules, the fourth adjacent photon module being adjacent to a fourth boundary of the photon modules. The first boundary and the second boundary are opposite to each other, and the third boundary and the fourth boundary are opposite to each other.

[0023] In some embodiments, patterning each of at least some of the multiple photon modules also includes: patterning the first photon module using a first photolithography shot connected to at least one common photomask; and patterning the second photon module using a second photolithography shot connected to at least one common photomask after the first photolithography shot.

[0024] Some embodiments relate to a computing system comprising: a photonic substrate patterned with a plurality of photonic modules, the plurality of photonic modules comprising at least a first photonic module and a second photonic module, each of the first photonic module and the second photonic module being patterned according to at least one common photomask, wherein the first photonic module is optically coupled to the second photonic module; a first die in communication with the first photonic module; and a second die in communication with the second photonic module.

[0025] In some embodiments, the first die includes a processor and the second die includes a memory.

[0026] In some embodiments, the computing system also includes a laser die coupled to the photonic substrate.

[0027] In some embodiments, each of the first photon module and the second photon module includes: a first boundary and a second boundary; an optical distribution network; a first optical waveguide that optically couples the optical distribution network to a first adjacent photon module among the plurality of photon modules, the first adjacent photon module being adjacent to the first boundary; and a second optical waveguide that optically couples the optical distribution network to a second adjacent photon module among the plurality of photon modules, the second adjacent photon module being adjacent to the second boundary.

[0028] In some embodiments, the first boundary and the second boundary are opposite to each other.

[0029] In some embodiments, the first optical waveguide and the second optical waveguide are patterned according to at least one common photomask.

[0030] In some embodiments, each of the first photon module and the second photon module includes an out-of-plane optical coupler, wherein the first die is optically coupled to the out-of-plane optical coupler of the first photon module and the second die is optically coupled to the out-of-plane optical coupler of the second photon module.

[0031] In some embodiments, the first die is coupled to a first side of the photonic substrate and the second die is coupled to a second side of the photonic substrate opposite the first side.

[0032] In some embodiments, the computing system also includes a third die stacked on top of the first die.

[0033] In some embodiments, the first photon module and the second photon module share a border such that the first photon module is adjacent to the second photon module.

[0034] In some embodiments, the first die is mounted above or below the first photon module; and the second die is mounted above or below the second photon module.

[0035] In some embodiments, the first die is in electronic communication with a first photon module, and the second die is in electronic communication with a second photon module.

[0036] Some embodiments relate to a multi-node computing system, including multiple computing systems, which include at least a first computing system and a second computing system, each of the first computing system and the second computing system including: a photonic substrate patterned with multiple photonic modules including at least a first photonic module and a second photonic module, each of the first photonic module and the second photonic module being patterned according to at least one common photomask, wherein the first photonic module is optically coupled to the second photonic module; a first tube die in communication with the first photonic module; a second tube die in communication with the second photonic module; and an optical fiber connecting the first computing system and the second computing system to each other.

[0037] In some embodiments, each of the first computing system and the second computing system further includes a fiber optic coupler, wherein the optical fiber optically couples the respective fiber optic couplers of the first computing system and the second computing system to each other.

[0038] In some embodiments, the first die includes a processor and the second die includes a memory.

[0039] In some embodiments, each of the first computing system and the second computing system further includes a laser coupled to the photonic substrate.

[0040] In some embodiments, each of the first photonic module and the second photonic module of the photonic substrate includes: a first boundary and a second boundary; an optical distribution network; a first optical waveguide that optically couples the optical distribution network to a first adjacent photonic module of the plurality of photonic modules, the first adjacent photonic module being adjacent to the first boundary; and a second optical waveguide that optically couples the optical distribution network to a second adjacent photonic module of the plurality of photonic modules, the second adjacent photonic module being adjacent to the second boundary.

[0041] In some embodiments, the first optical waveguide and the second optical waveguide are patterned according to at least one common photomask.

[0042] In some embodiments, each of the first photon module and the second photon module includes an out-of-plane optical coupler, wherein the first die is optically coupled to the out-of-plane optical coupler of the first photon module and the second die is optically coupled to the out-of-plane optical coupler of the second photon module.

[0043] In some embodiments, the first die is coupled to a first side of the photonic substrate and the second die is coupled to a second side of the photonic substrate opposite the first side.

[0044] In some embodiments, the multi-node computing system further includes a third die stacked on top of the first die.

[0045] In some embodiments, the first photon module and the second photon module share a border such that the first photon module is adjacent to the second photon module.

[0046] In some embodiments, the first die is mounted above or below the first photon module; and the second die is mounted above or below the second photon module.

[0047] Some embodiments relate to a photonic communication platform, comprising: a photonic network including a plurality of optical switches formed on a semiconductor substrate, a plurality of dies communicating with the photonic network; an electronic switch network including a plurality of transistors co-integrated with the plurality of optical switches, the electronic switch network being configured to: at a first time, program the optical switches to form a first optical communication path coupling a first subset of the plurality of dies together, and at a second time after the first time, program the optical switches to form a second optical communication path coupling a second subset of the plurality of dies together, the second optical communication path being different from the first communication path.

[0048] In some embodiments, a plurality of transistors are formed on a semiconductor substrate.

[0049] In some embodiments, the semiconductor substrate is a first semiconductor substrate, and wherein the plurality of transistors are formed on a second semiconductor substrate, wherein the first semiconductor substrate and the second semiconductor substrate are 3D-bonded together.

[0050] In some embodiments, programming the optical switch to form a first optical communication path includes: identifying an optical communication path that couples a first subset of the plurality of dies together; and programming the optical switch based on the identified optical communication path.

[0051] In some embodiments, identifying an optical communication path coupling the first subset of the plurality of dies together includes monitoring usage of a photonic network.

[0052] In some embodiments, the electronic switch network is further configured to determine at least one characteristic of an optical signal at a first optical communication path; identify a coding scheme based on the at least one characteristic of the optical signal; and enable the photonic network to perform optical communication on the first optical communication path based on the coding scheme.

[0053] In some embodiments, the plurality of dies are in electronic communication with a photonic network.

[0054] In some embodiments, the electronic switch network is further configured to cause the photonic network to optically communicate over the first optical communication path using wavelength division multiplexing. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Various aspects and embodiments of the present application will be described with reference to the following drawings. It should be understood that these drawings are not necessarily drawn to scale. Items appearing in multiple drawings are represented by the same reference numerals in the drawings in which they appear.

[0056] Figure 1 A computing system based on a photonic communication platform is shown in accordance with some embodiments.

[0057] Figure 2A A semiconductor wafer is shown in accordance with some embodiments.

[0058] Figure 2B A photomask set is shown in accordance with some embodiments.

[0059] Figure 2C An exemplary photomask for forming an optical waveguide according to some embodiments is shown.

[0060] Figure 2D According to some embodiments, Figure 2B The photomask set is patterned Figure 2A of wafers.

[0061] Figure 2E Identify the Figure 2D A photonic substrate is formed on a patterned wafer.

[0062] Figure 3A According to some embodiments Figure 2E Example photonic module of a patterned wafer.

[0063] Figure 3B Out-of-plane coupling of light between a photonic module and a die is shown according to some embodiments.

[0064] Figure 3C Out-of-plane coupling of light between photonic communication structures is shown in accordance with some embodiments.

[0065] Figure 3D A set of photon modules of the type shown in FIG. 3 is shown in accordance with some embodiments.

[0066] Figure 3E A waveguide arrangement at a boundary between a pair of adjacent photonic modules is shown in accordance with some embodiments.

[0067] Figure 3F Another waveguide arrangement at a boundary between a pair of adjacent photonic modules is shown in accordance with some embodiments.

[0068] Figure 3G Another waveguide arrangement at a boundary between a pair of adjacent photonic modules is shown in accordance with some embodiments.

[0069] Figure 3H A group of photonic modules sharing the same metal trace pattern are shown in accordance with some embodiments.

[0070] Fig. 3I A cross-section of a photonic substrate is shown in accordance with some embodiments.

[0071] Figure 4 A photonic system including a die mounted to a photonic substrate is shown in accordance with some embodiments.

[0072] Figure 5A An example optical distribution network is shown in accordance with some embodiments.

[0073] Figure 5B According to some embodiments, Figure 5A Multiple photonic modules for optical distribution networks.

[0074] Figure 5C Another example optical distribution network is shown in accordance with some embodiments.

[0075] Figure 5D Another example optical distribution network is shown in accordance with some embodiments.

[0076] Fig. 6A A photonic module including a transceiver and a plurality of switches is shown in accordance with some embodiments.

[0077] Figure 6B In more detail, the Fig. 6A transceiver.

[0078] Figure 6C A plurality of photon modules of the type shown in FIG. 6 are shown in accordance with some embodiments.

[0079] Fig. 7A A photonic communication platform including an electronic switching network is shown in accordance with some embodiments.

[0080] Figure 7B The first optical path is controlled to form a first optical path according to some embodiments. Fig. 7A Photonic communication platform.

[0081] Figure 7C The second optical path is controlled to form a second optical path according to some embodiments. Fig. 7A Photonic communication platform.

[0082] Fig. 8A A computing system based on a photonic communication platform is shown in accordance with some embodiments.

[0083] Figure 8B According to some embodiments, the Fig. 8AA multi-node computing system of a plurality of computing systems of the type shown. DETAILED DESCRIPTION

[0084] I. Scalability of memory bandwidth

[0085] The inventors have recognized and appreciated that one of the major bottlenecks limiting the spread of data-intensive computing is the inability to scale memory capacity and bandwidth in modern computers at a high enough rate. The inventors have developed a photonic communication platform that is able to scale memory capacity and bandwidth far beyond the capabilities of traditional computers.

[0086] Data-intensive computing systems (such as those designed to process deep learning algorithms) need to access large amounts of data, thus increasing the requirements for memory capacity. In addition, most applications require real-time or quasi-real-time access to data, thus increasing the requirements for memory bandwidth. Some traditional computing systems use graphics processing units (GPUs) to improve memory access efficiency. Some GPUs transfer data from memory at bandwidths of up to 256GB / s. While such memory bandwidth may be sufficient for most graphics-based applications, it is far from enough for data-intensive applications (such as deep neural networks and high-frequency trading).

[0087] Deep neural networks rely on a large number of parameters, such as weights and activation parameters. For example, a typical 50-layer network with 26 million weight parameters can calculate up to 16 million activations in a forward pass. If 32-bit floating point values ​​are used to store weights and activation parameters, the total storage requirement is 168MB. In addition, if the data is represented as a dense vector, the memory requirements may increase to several gigabytes. During training, the location of the training data set is important due to the frequency of accessing these large data sets. These data volumes are too large to be stored in the internal memory of the GPU, so multiple external dynamic random access memories (DRAMs) need to be used. Each DRAM chip communicates with the processor via an electronic communication carrier. For example, in a computing system using a silicon interposer, where the processor and memory chips are mounted on the same interposer, the memory-processor communication is supported by conductive traces formed on the interposer. In recent years, the use of silicon interposers has become widespread because the density of conductive traces that the interposer can provide is much greater than that of a printed circuit board (PCB). However, the interposer cannot be infinitely scaled. The interposer manufactured using micromachining technology has a limited area, thus limiting the number of memory chips that the interposer can accommodate.

[0088] Furthermore, the presence of parasitic impedance further limits bandwidth scalability. Ideally, the impedance of the conductive traces of the interposer would be negligible. In practice, unfortunately, the impedance of the traces is significant. Parasitic impedance limits bandwidth scalability in two ways. First, it limits the bandwidth that the trace can support. Second, it increases power consumption. Even worse, parasitic impedance increases with trace length, meaning that the greater the separation between the memory chip and the processor, the lower the bandwidth. This is why traditional computing systems are typically designed to place memory chips within a few centimeters of the processor. However, there are only so many memory chips that can fit within this range. The result is that traditional computing systems are limited in both memory bandwidth and memory capacity.

[0089] II. Overview of Photonic Communication Platform

[0090] The communication platform developed by the inventors overcomes these limitations using photons. Optical communications are inherently immune to parasitic impedances based on the physics of light propagating within a waveguide. Immunity to parasitic impedances brings a major benefit—it eliminates the requirement to place memory chips within specific confines of the processor.

[0091] Another advantage of the photonic communication platforms developed by the inventors is that they can be easily adapted to different computer architectures. Single-node computer architectures involve a processor chip, each of which can have more than one processor core; and multiple memory chips. Multi-node computer architectures involve multiple processor chips and multiple memory chips. Some multi-node architectures use a ring topology—each processor communicates directly with two adjacent processors, and communications with other processors go through adjacent processors. Other multi-node architectures use a star topology—a central hub is responsible for routing core-to-core communications. Another multi-node architecture uses a multicast topology—each processor communicates directly with multiple other processors.

[0092] Some aspects of the photonic communication platforms described herein make them easy to adapt to any of these architectures (and others). Some embodiments provide a photonic communication platform using a "photonic module". Each photonic module includes a programmable photonic circuit that can be configured based on the needs of a specific computer architecture. Some platforms are arranged according to a one-dimensional scheme, such as in a block of 3×1 modules, in a block of 5×1 modules, in a block of 10×1 modules, in a block of 20×1 modules, etc. Some platforms are arranged according to a two-dimensional scheme, such as in a block of 3×3 modules, in a block of 5×3 modules, in a block of 5×5 modules, in a block of 10×10 modules, etc. More generally, the platform supports any block of N×M modules, where N≥1 and M≥1, and any topology, such as T-topology, L-topology, X-topology, etc. Each photonic module can be used as a node of a computing system. At each node, there may be one or more digital processor chips, one or more analog accelerators, one or more photonic accelerators, one or more memory chips, one or more network chips, or other devices.

[0093] Figure 1 An example computing system based on a photonic communication platform with nine photonic modules arranged in a 3×3 topology according to one example is shown. The computing system 10 includes a photonic substrate 20 patterned with nine photonic modules 22 (also referred to herein as "photonic sites" or simply "sites"). The photonic communication platform supports a processor die (30) located in the middle of the photonic substrate 20, and eight memory nodes surrounding the processor die. Some memory nodes include a single memory chip (e.g., see memory die 32). Other memory nodes include stacked memories including multiple vertically stacked memory dies (e.g., see stacked memory 32). The die can communicate with the photonic modules electronically (e.g., using through silicon vias, copper pillars, micro-bumps, ball grid arrays, or other electrical interconnects) or optically (e.g., using grating couplers, prisms, lenses, or other optical couplers).

[0094] As described in further detail below, the photon module is patterned with an optical waveguide and an optical distribution network. The optical distribution network of the photon module can selectively optically communicate the die of the particular photon module with any other die of the computing system. For example, the optical distribution network of the photon module below the processor die 30 can be reconfigured according to the needs of the processor. At the beginning of the routine, the processor may need to access data stored in a first memory node. The read operation involves configuring the corresponding optical distribution network to optically communicate the processor with the first memory node. Later in the routine, the processor may need to write data to a second storage node. The write operation involves reconfiguring the optical distribution network to optically communicate the processor with the second memory node.

[0095] The inventors also recognized that mass manufacturing of photonic modules can be expensive. The photonic communication platforms described herein are designed in a manner that limits manufacturing costs. These platforms rely on the use of a common photomask set (or at least one common photomask) to manufacture multiple photonic modules. This approach reduces costs in two ways. First, it reduces the additional costs that would be incurred when procuring multiple different photomask sets. Second, it enables the use of standard semiconductor foundries to manufacture photonic modules, some of which require the use of the same photomask set (or at least one photomask) across an entire wafer. Designing photonic modules that share at least one photomask enables the manufacture of many photonic modules on the same semiconductor wafer while utilizing a standard, low-cost step-and-repeat manufacturing process.

[0096] III. Photon Module

[0097] The photonic modules described herein can be manufactured using microfabrication techniques, including, for example, complementary metal oxide semiconductor (CMOS) microfabrication techniques. Thus, some embodiments relate to photonic silicon-based optical communication platforms. Some specific microfabrication techniques involve step-and-repeat methods—where a stepper is used to pattern a semiconductor wafer using multiple copies of a template layout. FIG. 2A to FIG. 2E Microfabrication techniques used to manufacture photonic modules are shown. FIG. 3A to FIG. 3F Examples of photonic modules patterned using these microfabrication techniques are shown.

[0098] First reference Figure 2A , which shows a semiconductor wafer 100. Wafer 100 can be made of any material. For example, wafer 100 can be made of (or include) silicon. In one example, wafer 100 is a silicon-on-insulator (SOI) wafer. In another example, wafer 100 is a bulk silicon wafer. Wafer 100 can have any size. For example, the diameter of wafer 100 can be 150mm, 300nm, or 450mm, among other possible values. However, not all wafers need to have a circular shape.

[0099] Figure 2B A photomask set that can be used to pattern a wafer 100 using photolithography techniques is shown. Photomask set 200 includes three photomasks (201, 202, and 203), but other sets may include more or fewer photomasks. Each photomask has a specific pattern of opaque and transparent areas. When the photomask is exposed to light, the opaque areas block the light, preventing it from illuminating the wafer, and the transparent areas allow the passage of light. The result is that the pattern of the photomask is transferred to the wafer.

[0100] Each photomask can define a specific layer of a photonic module. One photomask can be used to define an optical waveguide. When the wafer goes through an etching process, only the exposed areas (or only the non-exposed areas) are etched away, while other areas remain unetched. When the wafer is exposed to light through the photomask, the photomask can be patterned to form a network of optical waveguides. Figure 2C A portion of a photomask that can be used to form waveguides on wafer 100 is shown. The lines of the photomask 201 represent opaque areas. The background of the photomask 201 is transparent. Exposing the photomask 201 to light causes the image of the photomask to be projected onto the wafer 100, enabling the waveguides to be patterned in the shape of the opaque areas. In this particular example, the pattern of the lines of the photomask results in a grid of waveguides.

[0101] Some photon modules involve the use of different levels of optical waveguides. In some such embodiments, the photomask set 200 may include a dedicated photomask for each waveguide level. Another photomask may be used to define n-doped regions. When the wafer undergoes an ion implantation or dopant diffusion process, only the exposed regions (or only the non-exposed regions) receive doping, while other regions remain undoped. Another photomask may be used to define p-doped regions using a similar process. Some photon modules involve the use of different doping concentrations. In some such embodiments, the photomask set 200 may include a dedicated photomask for each doping concentration. In other embodiments, the photomask set 200 may include a photomask used to define the deposition of semiconductor materials other than silicon (such as germanium and / or other materials of the periodic table, such as III or V groups). Another photomask may be used to define metal contacts. Another photomask may be used to define metal traces. Some photon modules involve the use of different levels of metal traces. In some such embodiments, the photomask set 200 may include a dedicated photomask for each metal trace level.

[0102] In some embodiments, wafer 100 is patterned in a step-and-repeat manner. As wafer 100 is processed in a stepper, the pattern of the photomask is repeatedly exposed in a grid on the surface of the wafer. This process involves moving the wafer stepwise back and forth and left and right under the lens of the stepper, exposing the photomask at each step. The result is that wafer 100 is patterned with multiple copies of the pattern defined by the photomask. This operation can be repeated for each photomask (or at least some of the photomasks) of the set.

[0103] In some embodiments, this process can be used to pattern wafer 100 with multiple copies of a template photonic module. Figure 2DIn the example of , the wafer 100 has been patterned with a grid of photon modules 22. The photon modules can share the pattern of one or more photomasks of the group 200. For example, the photon modules can share the pattern of the same waveguide photomask and / or the same m-trace photomask. In other embodiments, the photon modules share the patterns of all photomasks of the group 200. For example, the photon modules can share the same optical waveguide pattern, the same n-doping pattern, the same p-doping pattern, the same contact pattern, the same metal trace pattern, etc.

[0104] In some embodiments, the entire surface of wafer 100 is patterned using photomask set 200. However, not all embodiments are limited in this regard, as some portions of wafer 100 may be patterned using a first photomask set and other portions of wafer 100 may be patterned using a second photomask set. In some embodiments, the first photomask set and the second photomask set may share one or more common photomasks, such as a waveguide photomask.

[0105] Once patterned, the wafer 100 may include multiple photonic substrates. The photonic modules 22 may be separated from the wafer together to form photonic substrates of any desired shape and size. For example, Figure 2E The wafer 100 has been labeled to obtain six photonic substrates from the wafer 100. The figure identifies a 1×1 photonic substrate having only one photonic module 22, a 2×2 photonic substrate having four photonic modules 22, a 2×3 photonic substrate having six photonic modules 22, and three 3×3 photonic substrates each having nine photonic modules 22. Separating the photonic substrates from the wafer involves cutting the wafer along the perimeter of the desired photonic substrate. One of the 3×3 photonic substrates of the wafer 100 can be used as Figure 1 An example of a photonic substrate for a computing system (see photonic substrate 20 ).

[0106] Combination Figures 2A-2D The described techniques enable the manufacture of photonic modules at a relatively low cost. Some semiconductor foundries require that the same photomask set (or at least one photomask) be used to pattern an entire wafer (or at least a portion of a wafer). Otherwise, patterning different portions of a wafer using different photomasks would involve replacing one photomask with another between photolithography exposures, which would make a step-and-repeat process inefficient and costly. Designing photonic modules that share at least one photomask enables the manufacture of many photonic modules on the same semiconductor wafer while utilizing a standard, low-cost step-and-repeat process.

[0107] Figure 3AAn example photon module 22 is shown. In this example, the photon module 22 is shaped as a rectangle (although other shapes are possible, such as a square or other polygon). Thus, the photon module 22 is bounded by four boundaries (boundaries 1, 2, 3, and 4). Boundary 1 is opposite boundary 2, and boundary 3 is opposite boundary 4. Boundary 1 is adjacent to boundaries 3 and 4, and boundary 2 is also adjacent to boundaries 3 and 4. The photon module 22 includes an optical distribution network 104 coupled to waveguides 111, 112, 113, and 114. Waveguide 111 optically couples the optical distribution network 104 to boundary 1. Thus, an optical signal coupled from the optical distribution network 104 to waveguide 111 can be transferred outside the photon module by crossing boundary 111. Similarly, waveguide 112 optically couples the optical distribution network 104 to boundary 2, waveguide 113 optically couples the optical distribution network 104 to boundary 3, and waveguide 114 optically couples the optical distribution network 104 to boundary 4. In some embodiments, the boundaries of the photon modules are defined based on a lithography shot (e.g., the boundaries are defined by the boundaries of a photomask used to fabricate the photon modules). However, in other embodiments, a lithography shot may define more than one photon module. For example, a photomask may be patterned with multiple side-by-side instances of a template photon module. In some such embodiments, the boundaries of the photon modules are defined where adjacent instances of the template photon modules meet.

[0108] Although Figure 3A The example of shows a waveguide coupling the optical distribution network to each boundary, but not all embodiments are arranged in this manner. In other embodiments, the photon module 22 may include two of the four waveguides, such as waveguides 111 and 112, or waveguides 111 and 113. In other embodiments, the photon module 22 may include three of the four waveguides, such as waveguides 111, 112, and 113. The optical distribution network 104 includes photonic components (e.g., photonic switches) for routing optical signals inside and outside the photon module 22.

[0109] In some embodiments, the photonic module may include multiple layers of photonic waveguides. Similar to how multiple layers of conductive traces improve the ability of an electronic circuit to route electrical signals, multiple layers of waveguides improve the ability of a photonic module to route optical signals. In one example, one layer includes a silicon waveguide and one layer includes a silicon nitride waveguide. In another example, multiple layers include a silicon waveguide. Additionally or alternatively, multiple layers include a silicon nitride waveguide. The choice of material for each waveguide layer may be determined by the wavelength of light to be routed by the waveguide. For example, a silicon layer and a silicon nitride layer may be used to route infrared light having a wavelength of approximately 1.3 μm or 1.5 μm in the telecommunications band. In some examples, the multilayer waveguide may also include an aluminum nitride waveguide that may be used to route visible light down to UV wavelengths or an aluminum oxide waveguide for routing UV light. Each layer may be fabricated in a manner similar to Figure 3AConfiguration shown - arranged with an optical distribution network that routes signals between layers of waveguides.

[0110] The photon module 22 also includes one or more out-of-plane couplers 105. The waveguide 117 optically couples the out-of-plane coupler 105 to the optical distribution network 104. The out-of-plane coupler 105 is configured to emit light received from the waveguide 117 outside the xy plane (e.g., in a direction parallel to the z-axis or at a certain angle relative to the z-axis). The out-of-plane coupler 105 can also be configured to capture light emitted outside the xy plane and pass the captured light to the waveguide 117. The out-of-plane coupler 105 is capable of optical communication between the photon module 22 and a die disposed above the photon module and / or below the photon module. The out-of-plane coupler 105 can be implemented using any suitable optical components, including, for example, gratings, lenses, and prisms. In some embodiments, the optical distribution network can be configured so that the same out-of-plane coupler 105 is capable of optical communication in two directions—from the optical distribution network 104 to the die and from the die to the optical distribution network 104. In other embodiments, one out-of-plane coupler 105 is capable of optical communication in one direction, while another out-of-plane coupler 105 ( Figure 3A In one embodiment, an out-of-plane coupler 105 may be used to couple a light source to the optical distribution network 104. The light source may be one of a laser (continuous wave or pulsed), an LED, or a superluminescent diode.

[0111] Figure 3B 1 shows how to use the out-of-plane coupler 105 for out-of-plane optical communication. For clarity, only the out-of-plane coupler 105, waveguide 117 and optical distribution network (ODN) 104 are shown inside the optical module 22. In this example, the out-of-plane coupler 105 is implemented with a grating. The die 320 is mounted to the photonic module 22. The die 320 may include a processor, memory and / or other electronic components ( Figure 3B 317). In addition, die 320 includes an out-of-plane coupler 351, a waveguide 317, and a controller 322. Controller 322 is electrically coupled to optical distribution network 104 via electrical connector 324, which may include, for example, a ball grid array, a copper pillar, a through silicon via, a microbump, a metal pad, etc. In this example, out-of-plane coupler 105 emits light in a direction parallel to the z-axis toward out-of-plane coupler 351. The out-of-plane coupler captures light and transmits the captured light to controller 322 via waveguide 317.

[0112] The controller 322 controls the operation of the optical distribution network 104. For example, the controller 322 controls the state of the switches of the optical distribution network 104. The control signals are provided to the optical distribution network 104 via the electrical connections 324. Alternatively or additionally, the controller may be formed directly on the photon module 22, and the controller may control the operation of the optical distribution network 104. The controller may provide the control signals to the optical distribution network 22 via conductive traces formed on the photon module 22.

[0113] Return to reference Figure 3A , the optical distribution network 104 can selectively couple any component of the photon module 22 to any other component of the photon module 22. For example, the optical distribution network 104 can enable light to pass between the waveguide 111 and the waveguide 112, and / or between the waveguides 111 and 112, and / or between the waveguide 113 and the waveguide 114, and / or between the out-of-plane coupler 105 and the waveguide 111, and / or between the out-of-plane coupler 105 and the waveguide 113, and so on.

[0114] Figure 3C 1 shows how an out-of-plane coupler 105 can be used to communicate between two photonic communication structures. For clarity, the figure shows only two photonic modules 22, using an out-of-plane coupler 105 to couple one light from each photonic communication structure to the other. The controller 322 is electrically coupled to the two optical distribution networks 104 using electrical connectors 324 and through silicon vias 125. Multiple photonic communication structures stacked on top of one another increase the number of optical and electronic communication channels between each site. In addition, having multiple communication structures can reduce the number of waveguide crossings required to route optical signals through the photonic modules, thereby reducing optical losses and improving the overall power budget.

[0115] A photonic substrate may include multiple photonic modules connected together to collectively form an optical network. Figure 3D An example 2×3 photonic substrate including six photonic modules 22 is shown. The photonic substrate is obtained by cutting a set of 2×3 photonic modules from a wafer 100 (see Figure 2E). The photonic modules 22 are arranged so that the waveguide 111 of the optical module is aligned with the waveguide 112 of the optical module to the left of the optical module, the waveguide 112 of the optical module is aligned with the waveguide 111 of the optical module to the right of the optical module, the waveguide 113 of the optical module is aligned with the waveguide 114 of the optical module above the optical module, and the waveguide 114 of the optical module is aligned with the waveguide 113 of the optical module below the optical module. As a result, the optical modules form an optical network. The optical distribution network 104 can route optical signals to anywhere inside or outside the network. For example, assume that the processor is mounted to the photonic module located at the northwest corner of the photonic substrate, and the memory is mounted to the photonic module located at the southeast corner of the photonic substrate. A read operation may involve reconfiguring the optical distribution network to optically communicate the processor with the memory. For example, the following optical communication paths can be formed: 1) coupling the processor to an out-of-plane coupler of a photonic module on which the processor is mounted, 2) coupling the out-of-plane coupler of the photonic module to waveguide 112 of the same photonic module, 3) coupling the waveguide 112 of the photonic module to the waveguide 111 of an adjacent photonic module (the topmost photonic module in the middle), 4) coupling the waveguide 112 of the topmost photonic module in the middle to the waveguide 111 of the next adjacent photonic module (the northeast corner of the photonic substrate), 5) coupling the waveguide 114 of the photonic module located at the northeast corner to the waveguide 113 of the photonic module on which a memory is mounted, and 6) coupling the waveguide 113 of the photonic module to the memory mounted to the out-of-plane coupler of the same photonic module.

[0116] As described above, the waveguides of adjacent photon modules are optically coupled to each other, thereby allowing light to pass from one photon module to the next. In some embodiments, the waveguides may be physically connected. Figure 3E , which depicts the region at the border of two adjacent photon modules. As shown, the waveguide 112 of the photon module on the left hand side is physically connected to the waveguide 111 of the photon module on the right hand side. In some embodiments, a continuous waveguide spans the border and extends between the respective optical distribution networks of the photon modules.

[0117] In other embodiments, there may be gaps between the waveguides. Figure 3F . In this example, each waveguide has an end at a distance from the boundary. Therefore, a gap is formed at the boundary area. Despite the gap, the waveguides 111 and 112 are still optically coupled to each other. In this case, in fact, the light emitted at the end of the waveguide propagates through free space to the end of the other waveguide. If the size of the gap is small enough (for example, less than 500 μm), most of the optical power radiated by one waveguide is coupled to the other waveguide.

[0118] In other embodiments, Figure 3GAs shown, a photonic bridge can be used to optically couple waveguides to each other. In this example, the ends of the waveguides are coupled to corresponding out-of-plane couplers 152. A photonic bridge die 300 is mounted to the boundary region. The photonic bridge die 300 includes a pair of out-of-plane couplers 352 and an optical waveguide 354 that couples the out-of-plane couplers to each other. Assume that the processor die 302 needs to send a read message to the memory die 304. This can be accomplished by: 1) transmitting out-of-plane light from the processor die 302 to the corresponding photonic module (e.g., in Figure 3B ), 2) passing the light to waveguide 112 and hence to out-of-plane coupler 152, 3) passing the light to out-of-plane coupler 352, 4) passing the light to waveguide 354 and hence to another out-of-plane coupler 352, 5) passing the light to another out-of-plane coupler 152, and 6) passing the out-of-plane light from the photonic module to the memory die 304 (e.g., in a manner as shown in FIG. Figure 3B as shown).

[0119] In some embodiments, the photon modules 22 can be patterned according to a common metal trace photomask. Thus, the photon modules share the same pattern of metal traces. In some embodiments, the photon modules 22 are patterned according to multiple common photomasks. Thus, multiple levels of metal traces share the same pattern on different photon modules. Some metal traces can be used to transfer power across the photon substrate. Some metal traces can be used to transfer electronic signals across the photon substrate.

[0120] Figure 3H A 2×3 photonic substrate is shown, where each photonic module 22 shares the same pattern of metal traces. For illustration purposes, for example, Figure 3D In the arrangement shown, only metal traces are shown in the figure, although each photon module also includes a waveguide, one or more out-of-plane couplers, and an optical distribution network. In this example, there are two levels of metal traces. Each level of metal traces has been manufactured using the same photomask on different photon modules. The metal traces of metal trace level 1 run in a horizontal direction, thereby electrically coupling adjacent photon modules to one another in the horizontal direction. The metal traces of metal trace level 2 run in a vertical direction, thereby electrically coupling adjacent photon modules to one another in the vertical direction. Of course, other arrangements are also possible. For example, in other embodiments, metal traces at the same level can electrically couple one photon module to all photon modules adjacent to it.

[0121] The metal traces are arranged to carry electrical power (e.g., signals and / or power) across the border of the photon module. This can be achieved by patterning the metal traces to continuously cross the border of the photon module. In this example, the metal traces of level 1 continuously cross the vertical border, and the metal traces of level 2 continuously cross the horizontal border. The metal traces of different levels can be connected using vias (in Figure 3H In some embodiments, the photon modules may share the same through-hole pattern. In other words, each photon module may use the same through-hole photomask. In some embodiments, the photon modules may have more (tens to hundreds) of metal traces. Some of these metal traces may be arranged to continuously span the photon modules, but in some embodiments, most of the metal traces do not need to be patterned to continuously span the modules.

[0122] Metal traces can be used to transfer power and / or electrical signals across the photonic substrate. In one example, a power supply is connected to a specific photonic module. The power generated by the power supply can be transferred from a specific photonic module to other photonic modules using metal traces. In another example, a controller chip can be bonded (e.g., 3D bonded) to a specific photonic module. The control signals generated by the controller can be transferred from a specific photonic module to other photonic modules using metal traces. The control signals can control the state of the optical distribution network of the photonic module.

[0123] As described above, electronic control circuits can be used to control the operation of the photon module. For example, these electronic control circuits can control how the optical distribution network 104 routes optical signals. The electronic control circuits can be integrated with the photon module in various ways. In some embodiments, the photon module can be formed on a first substrate and the electronic control circuit can be formed on a second substrate. The two substrates can be bonded together to electrically communicate the electronic control circuit with the optical distribution network. However, in other embodiments, the electronic control circuit can be directly manufactured on the same substrate as the photon module. Manufacturing the photon module and the electronic control circuit on the same substrate can reduce costs because it is not necessary to rely on two separate manufacturing processes and a bonding process, but only one manufacturing process may be required.

[0124] Fig. 3I is a cross-section of a photonic substrate that integrates a photonic module with transistors. The transistors can be connected to each other to define an electronic control circuit. In this example, the photonic substrate is formed on an SOI substrate, but other types of substrates are possible, including bulk silicon substrates. An insulating layer (e.g., a silicon dioxide layer) is formed on the silicon substrate. A silicon layer is formed on the insulator layer. The silicon layer is patterned to form waveguides and other optical components, such as bonding Figure 3AComponents described. The cross section shows a portion of a Mach-Zehnder interferometer having arms defined by waveguides 370 and 371. The Mach-Zehnder interferometer defines one of the switches of the optical distribution network 104. Transistor block 380 is formed in the same silicon layer as waveguides 370 and 371. Transistor block 380 includes a plurality of transistors (e.g., tens of thousands, hundreds of thousands, millions, or more) connected together to form an electronic control circuit. The photonic substrate also includes multiple levels of metal traces (although this example only shows two levels of metal traces). Vias connect the metal traces to the waveguides and transistors. The metal traces enable the electronic control circuit to control the operation of the Mach-Zehnder interferometer.

[0125] Figure 4 is a cross-sectional view of an example computing system 400 based on a photonic substrate 20 (e.g., a 3×3 photonic substrate). A die stack including die 420, 421, and 422 is mounted to a photonic module located on the left-hand side of the photonic substrate 20. These die may form, for example, a stacked memory cell. Laser die 430 is mounted on one side of the photonic module in the middle of the substrate, and die 431 is mounted on the other side of the same photonic module. In order to support the die on opposite sides, the photonic module may include at least one out-of-plane coupler that emits light in an upward direction and at least one out-of-plane coupler that emits light in a downward direction. Dies 440 and 441 are mounted side by side to the same photonic module. Dies 440 and 441 may include, for example, a processor or a memory. As shown in combination Figure 3D As described, photonic modules provide a platform for distributing optical signals from one die to another.

[0126] Laser die 430 includes one or more lasers. The light generated by the laser can be distributed throughout the computing system and can be used as a reference light modulated by data. Laser die 430 can include a III-V laser, such as an InP-based laser. For example, surface mounting technology can be used to bond the laser die 430 to a photonic substrate. An out-of-plane coupler can be used to couple the laser of the laser die 430 to a semiconductor substrate. In some embodiments, a ball lens can be used to direct the laser emitted in a direction parallel to the chip surface to the out-of-plane coupler.

[0127] Recent advances in III-V laser die-to-wafer bonding on silicon photonics-based wafers have shown that the yield of the process can be well below 100%. To avoid this problem, two or more lasers can be pointed at the same input of the photonic substrate. Only one laser can be used at a time, but if one laser fails, then another laser can be turned on and injected into the photonic substrate. Having multiple lasers per photonic substrate improves the reliability of the platform in the event of failure of one or more lasers.

[0128] Chip-based III-V lasers are not the only external light source option for optical communication platforms. Other lasers (e.g., semiconductor-based lasers, such as those used for optical telecommunications) can be coupled into the platform using optical fibers or using free-space optics such as lenses. In some embodiments, 1-N splitters can be used to enable a single laser to provide light to multiple photonic modules, thereby reducing the number of laser dies.

[0129] Some applications may require multiple lasers and may also require that the optical signals emitted by the lasers be mutually coherent (e.g., temporally coherent). In some such embodiments, an optical communication platform of the type described herein may be used to phase lock one or more lasers to a single master laser. One or more optical distribution networks 105 may be configured to mix the master laser with one of the slave lasers and measure their beat interference pattern. The beat interference pattern is used as an error signal to lock the phase so that the entire system is coherent.

[0130] In some embodiments, lasers emitting at different wavelengths can be used to support wavelength multiplexing schemes. For example, wavelength division multiplexing (WDM) schemes can be used to increase the bandwidth utilization of each waveguide. Other schemes include multimode waveguides, time division multiplexing, and / or polarization diversity. These technologies support multiple independent communication channels using the same optical path.

[0131] In some embodiments, a suitable light source other than a laser, such as an LED or a superluminescent diode, may be used in place of the laser described above. The choice of light source is also affected by the choice of wavelength in the photonic communication structure. If the structure is intended to communicate using visible light, the light source should be selected to output light of the appropriate wavelength.

[0132] IV. Optical Distribution Network

[0133] The optical distribution network 104 may be implemented using optical switches. Examples of optical switches include Mach-Zehnder interferometers, optical resonators, multimode interference (MMI) waveguides, arrayed waveguide gratings (AWGs), thermo-optic switches, acousto-optic switches, magneto-optic switches, MEMS optical switches, nonlinear optical switches, liquid crystal switches, piezoelectric beam steering switches, grating switches, dispersion switches, etc.

[0134] The optical distribution network 104 can be static or dynamic (e.g., reconfigurable based on electrical or optical control signals). A static network can, for example, receive multiple wavelengths from the same input waveguide and route each wavelength to a different output waveguide. Another static network can receive two orthogonal polarizations from the same input waveguide and route each polarization to a different output waveguide. Another static network can receive multiple modes from the same input multimode waveguide and route each mode to a different output waveguide.

[0135] The dynamic optical distribution network can be reconfigured according to the needs of the computing system. Figure 5A An example of a dynamic optical distribution network is shown. In this example, the optical distribution network 104 includes a 3×1 switch 602, two 1×2 switches 606, and an optical coupling element 107. This photonic module also includes waveguides 111-114 and an out-of-plane coupler 105, which can optically communicate with a laser die or other die. Switch 602 selects one of waveguide 111, waveguide 113, and out-of-plane coupler 105 as an input. The first switch 604 routes the input received from switch 602 to the optical coupling element 107 or switch 604. The optical coupling element 107 directs optical power to the photonic emitter shown in Figure 6. In some embodiments, the optical coupling element 107 includes an out-of-plane coupler for coupling light to the die. The second switch 604 routes the input received from the first switch 604 to the waveguide 112 or the waveguide 114. In some embodiments, a Mach-Zehnder interferometer is used to implement switch 604.

[0136] Figure 5B Shown included in Figure 5A 6. A 3×3 photonic substrate of a photonic module of the type shown in FIG. 6. In this example, the photonic chip located at the northwest corner of the photonic substrate is coupled to a laser 600. In some embodiments, the laser 600 is formed on the laser die and optically coupled to the out-of-plane coupler 105. In other embodiments, the laser 600 is integrated as part of the photonic module (e.g., placed in a groove formed through the top surface of the photonic module). The laser 600 can emit a single wavelength or multiple wavelengths. In some embodiments, the laser 600 provides light to the entire photonic substrate, but in other embodiments, other photonic modules may also have lasers.

[0137] Figure 5C and 5D Other possible implementations for the optical distribution network 104 are shown. Figure 5CAn example of is fully connected - all boundaries of the photonic module are coupled to each other. Light entering from the boundary passes through multiple 1×2 switches 604, which determine whether the light goes straight, left, or right. In some embodiments, routing can be performed for each optical channel (e.g., each waveguide mode, polarization, or wavelength).

[0138] However, in some embodiments, a fully connected routing topology may not be necessary or feasible. Figure 5D As shown in the example (including two 1×2 switches), routing can be restricted to fewer options to reduce the complexity of the optical distribution network. Reducing routing options reduces the number of switches per optical module, thereby reducing power consumption and channel crosstalk, and improving signal-to-noise ratio (SNR). However, these gains come at the expense of data bandwidth.

[0139] V. Optical Interconnect Structure

[0140] Fig. 6A An example of a reconfigurable photonic communication structure is shown. The communication structure includes a plurality of switches, where "2:2" represents a 2×2 switch and "3:3" represents a 3×3 switch. The switches can be configured according to the needs of the computing system. The transceiver 700 includes an optical-to-electrical converter and an electro-optical converter. In some embodiments, the transceiver 700 embodies Figure 5A The optical coupling element 107 is provided. Figure 6B An example of a transceiver 700 is shown. For clarity, only one transmitter / receiver pair is shown, but there may be a transmitter / receiver pair for each waveguide coupled to the transceiver 700. A switch 702 arbitrates between a transmitter (TX) 704 and a receiver (RX) 706. TX 704 includes an electrical-to-optical converter, such as an optical modulator. RX 706 includes an optical-to-electrical converter, such as an optical receiver. Figure 6C shows a 3×3 photonic substrate, where each node consists of Fig. 6A Photon module.

[0141] VI. Electronic Switching Network

[0142] The inventors have realized that docking a die (e.g., memory, processor, etc.) with a photonic substrate as described herein causes compatibility issues. Ideally, the die is predefined with a control circuit for controlling the operation of the optical distribution network and the pins that are perfectly aligned with the pins of the photonic substrate. In this way, once the die and the photonic substrate are bonded together, they are inherently inclined to communicate with each other. However, this approach may be impractical because the die and the photonic substrate are usually manufactured by different entities. For example, an entity in the United States can manufacture the photonic substrate, and another entity in Japan can manufacture the die. This approach burdens the entity that manufactures the die to include control circuits and pins that are compatible with the photonic substrate, which greatly increases the cost of the die manufacturer. Recognizing this problem, the inventors have developed an electronic switch network used as an interface between the photonic substrate and the die. These electronic switch networks are arranged so that the die does not need to be redesigned to be compatible with the photonic substrate, thereby saving costs for the die manufacturer. In essence, the electronic switch network defines the switching and control protocol for the photonic communication platform.

[0143] Some electronic switch networks are co-fabricated with the photonic modules. In some embodiments, the electronic switch networks are formed on the same substrate as the photonic modules. Fig. 3I , for example, the electronic switch network can be defined by transistors 380. In other embodiments, the photonic module is formed on a first substrate, the electronic switch network is formed on a second substrate, and the substrates are bonded (e.g., 3D bonded) together. Regardless of how it is formed, the electronic switch network can be used to program the optical distribution network 104. The use of the electronic switch network enables the design of dies with minimal interface circuitry, thereby reducing the costs that die manufacturers must incur to make their dies compatible with the photonic substrate.

[0144] Fig. 7A A photonic substrate is shown that is co-integrated (e.g., directly bonded or formed on the same substrate) with an electronic switching network. The photonic substrate includes six photonic modules arranged in a 2×3 configuration. As described above, each photonic module includes an optical distribution network 104. The electronic switching network includes a plurality of controllers 740, digital-to-analog converters (DACs) 750, a memory 742, and a debug unit 744. Each controller 740 controls the optical distribution network via a DAC 750. The controller 740 can control the state of the switches of the optical distribution network to dynamically reconfigure the optical links as needed. Return to Reference Figure 6C For example, the controller 740 may be used to control the states of a 2×2 switch and a 3×3 switch.

[0145] The electronic switch network can program the optical distribution network based on data stored in the memory 742. For example, the memory can store instructions that, when executed, cause the optical distribution network to execute a predefined switching sequence. Alternatively, the memory can store instructions that, when executed, cause the optical distribution network to dynamically optimize optical links based on the needs of a specific application. In some embodiments, the electronic switch network can monitor the use of optical links and can determine which optical links are being used and which optical links are available, or which optical links can provide bandwidth exceeding a threshold bandwidth. The electronic switch network can use this information to decide how to assign optical links to specific data streams. This may be particularly useful in a photonic communication platform that connects, for example, hundreds of memory dies and processors. Such a photonic communication platform can rely on the electronic switch network to determine the best optical path to allow a specific processor die to access information from a specific memory die. In some embodiments, a machine learning algorithm can be used to identify the best optical link.

[0146] In some embodiments, the electronic switch network is configured to perform the following steps. At a first time, the electronic switch network programs the optical switches of the photonic substrate to form a first optical communication path that couples a first subset of multiple dies together (e.g., coupling the first die to the second die). Programming the optical switches at the first time may involve changing the state of some switches (e.g., the first subset of switches) without changing the state of other switches, or may involve changing the state of all switches. At a second time after the first time, the electronic switch network programs the optical switches to form a second optical communication path that couples a second subset of multiple dies together (e.g., the third die to the first die or the third die to the fourth die). The electronic switch network can continue to reprogram the optical switches as needed. Programming the optical switches at the second time may involve changing the state of some switches (e.g., the first subset of switches or the second subset of switches) without changing the state of other switches, or may involve changing the state of all switches. Changing the state of a switch can involve any of the following operations: changing the output of the switch from an off state to an on state, changing the output of the switch from an off state to a partially on state (e.g., a state in which the switch passes a portion of the input power to an output terminal and a portion of the input power to one or more other output terminals), changing the output of the switch from an on state to a partially on state, changing the output of the switch from an on state to an off state, selecting one or more inputs of a previously unselected switch, and / or deselecting one or more inputs of a previously selected switch.

[0147] exist Figure 7B In the example of , an electronic switching network has programmed the photonic substrate to form an optical path from a first die to a second die. Figure 7CAs shown, the electronic switch network has reprogrammed the photonic substrate to form an optical path from the third die to the first die. In some embodiments, the electronic switch network can program the optical distribution network using wavelength division multiplexing and / or time division multiplexing.

[0148] A typical connection between nodes may start with a request message on the electronic switch network. The request may be arbitrated by the grid of electronic switches to establish the connection. At each network hop, once the electrical request wins arbitration, an optical link is established. Once the connection is fully established between the source and destination, an acknowledgment is returned to the requester on the electronic network, and data transfer proceeds over the optical link.

[0149] The controller 740 can use the debug unit 744 to perform testing, diagnosis and fault isolation of metal traces, contacts, pins, pads, etc. In some embodiments, the debug unit is implemented using the Joint Test Action Group (JTAG) industry standard. In some embodiments, manufacturing defects may result in a non-functional communication channel. Redundant connections (optical and / or electrical) can be included and mapped as replacements, eliminating the need to discard platforms with a small number of defects.

[0150] The ability to dynamically reconfigure a photonic communication platform in a dynamic manner allows the electronic switch network to operate at relatively low bandwidth, resulting in relatively low power consumption. Low power is particularly beneficial when the amount of data carried through the photonic modules between switching events is relatively large. In some embodiments, low power opens the opportunity for "always-on" operation where training or reconfiguration sequences can be monitored.

[0151] In some embodiments, the power and fidelity of an optical signal propagated across multiple photon modules may depend on the number of waveguide intersections that the signal passes through. Therefore, the farther the optical signal is transmitted, the greater the power consumption and the lower the fidelity. Recognizing this problem, the inventors have developed the following configuration: a coding scheme with a larger or smaller alphabet (more or fewer bits per symbol) can be adaptively selected according to the number of photon module boundaries that the signal should pass through or the expected optical loss or any other characteristics of the optical path. For example, when only a few crossovers or a small amount of loss are expected, a coding scheme with a larger alphabet can be used. Examples of such coding schemes include quadrature amplitude modulation (QAM) using a constellation of 16 points (16-QAM), 64 points (64-QAM) or 256 points (256-QAM), and pulse amplitude modulation (PAM) with many levels, such as PAM-16 or PAM-32. Vice versa, when many crossovers or a large amount of loss are expected, a coding scheme with a smaller alphabet can be used. Examples of such encoding schemes include binary phase shift keying (BPSK) or PAM with few levels, such as PAM-2 or PAM-4. In some embodiments, the bandwidth of the optical path can be set according to the changing communication mode or according to the number of photonic module boundaries that the signal should cross.

[0152] The clocking of the electronic switching network can be done using a single distributed clock. The clock phase can be adjusted in the photonic domain to achieve extremely low jitter at each receiver. This avoids the need for an embedded clock, and therefore the data does not need to be encoded. Uncoded data allows for increased bandwidth, reduced latency, and lower power.

[0153] VII. Computing systems based on photonic communication platforms

[0154] The photonic communication platforms described herein can be used to form computing systems. Unlike electronic distribution networks, these optical communication platforms can provide copies of the same message to multiple locations simultaneously without problems caused by parasitic impedance. This feature allows optical distribution networks to form multicast and / or broadcast communication schemes. Optical distribution networks can be dynamically reconfigured to route messages to a single node or multiple nodes. Using broadcast and / or multicast capabilities, some embodiments are able to perform MapReduce operations directly using optical communication platforms.

[0155] These types of computing systems can be used for a variety of applications, including, for example, high-performance computing, neural, machine learning and deep learning networks, graphics rendering, large-scale visualization, gaming, high-frequency trading, and video streaming, among others.

[0156] Fig. 8AAn example computing system 800 is shown. The computing system is formed on a 4×4 photonic substrate. Of course, other sizes and topologies are possible. In this example, there are four processor dies 704 located in the middle of the photonic substrate, and there are twelve memory dies 702 surrounding the processor dies. Each die is mounted on a photonic module. Each die uses, for example, an out-of-plane coupler (e.g., Figure 3B or Figure 3C ) to communicate with the corresponding photon module. Other embodiments may include a different number of processors and a different number of memories, and / or may include other types of dies, including, for example, analog accelerators, photon accelerators, photon memories, network chips, etc. In some embodiments, the computing system 800 is disposed on an interposer and may communicate with the interposer using through silicon vias.

[0157] Fig. 8A The bottom inset of FIG. 7 shows the photon module 722 in more detail. The photon module 722 can be implemented using (or including) any of the photon modules described above. For example, the photon module 722 includes the optical distribution network 104. The photon module 722 can also include a method for allowing communication with adjacent photon modules (see, e.g., Figure 3A The waveguides 111-114) for optical communication (not shown in Fig. 8A ). The photonic module 722 also includes at least one fiber optic coupler 710, which may include an edge coupler and / or an out-of-plane coupler. The fiber optic coupler 710 can be coupled to the end of an optical fiber, thereby enabling communication with other systems. Edge couplers enable optical coupling within the plane of the photonic module. Examples of edge couplers include tapered waveguides, V-grooves, and U-grooves. In some embodiments, the edge coupler includes only the end of a waveguide at the edge of the photonic substrate. In contrast, out-of-plane couplers (e.g., grating couplers and prisms) enable optical coupling outside the plane of the photonic chip. This particular computing system is arranged so that the bottom-most photonic module is connected to an optical fiber (as indicated by the label "Fiber Channel"). The photonic module 722 may also include one or more out-of-plane couplers (not shown). Fig. 8A ), which is capable of optical communication with a die mounted to a photonic module (see e.g. Figure 3A out-of-plane coupler 105).

[0158] Fig. 8AThe top illustration of shows the memory die 702 in more detail. The memory die 702 includes a memory block 720, which includes several memory cells (e.g., solid-state memory such as NAND, DRAM, SRAM, HBM, etc.). The memory die 702 also includes a communication block 724, which may include optical components for communicating with the photonic module on which the memory die is mounted. For example, the communication block 724 may include an out-of-plane coupler coupled to an out-of-plane coupler of the photonic module. The memory die 702 also includes a serializer / deserializer (SERDES) block 722. The SERDES block 722 converts data from serial to parallel and vice versa. In this particular embodiment, the SERDES block is located near the outer edge of the memory die 702 and the memory block 720 is located in the middle of the memory die. Of course, other arrangements are possible. Although Fig. 8A The processor die 704 is not shown in detail, but the processor die may also include out-of-plane couplers that couple with out-of-plane couplers of corresponding photonic modules.

[0159] Combination Fig. 8A The described computing system can be used as a stand-alone computing system or can be used in combination with other computing systems. The combination of computing systems is referred to herein as a multi-node computing system. Figure 8B An example of a multi-node computing system including four computing systems 800 is shown. Other multi-node computing systems may include many computing systems, such as tens or hundreds of units, or more. Optical fiber 712 is used to enable computing systems to communicate with each other. Each end of the optical fiber is coupled to a fiber coupler 710 of the computing system 800. In this example, the computing systems of the multi-node computing system share the same layout (the same number of photonic modules, processor dies, and memory dies). However, not all embodiments are limited in this regard. In some embodiments, communication between many multi-node computing systems can be accomplished electronically using a silicon interposer. If the computing systems are placed adjacent to each other or within a few centimeters to reduce capacitance and other parasitic resistances, this communication strategy can consume a considerable amount of power.

[0160] The inventors have also recognized that an optical module of the type described herein can be used as a transceiver to enable communication from a computing system to another computing system or from a computer system to a host. The transceiver can be optical or electronic. Exemplary optical interfaces include board-to-board communication via optical fiber or remote rack-to-rack communication using a higher-level protocol (such as Ethernet or Infiniband technology). The electronic interface of the host system includes a SERDES-based standard such as PCI Express. An external I / O module can manage communication between a host and a local system. This includes a direct memory access offload function for high-speed data movement between remote and local memory. The external I / O module can also provide a local interface for management, calibration, boot, and reliability and serviceability (RAS).

[0161] An optical communication platform of the type described herein can provide a layered network stack. An exemplary stack configuration is as follows. The physical layer includes optical interconnects, including optoelectronic converters, electro-optical converters, and optical distribution networks. The data link layer includes an electronic switch network that allows connections between modules. In some embodiments, communication between network nodes can start with a request message on the electronic switch network. The data link layer processes this request and arbitrates through a grid of electrical switches to establish a connection. At each photon module boundary, if the request wins the arbitration, an optical link is formed. Once the connection is fully established between the source and the destination, an acknowledgment can be returned to the requester on the electronic switch network, and data is transmitted through the photon module. The transport layer involves information packetization, data integrity, and buffer allocation. The transport layer implements upper layer protocols on the data link layer using information packetization. Flow control can be implemented with buffer credits. If reliability provisions provide additional protection for errors at the physical layer, data integrity can be used, which includes cyclic redundancy checks (CRC) (e.g., retransmission) and / or forward error correction (FEC) schemes.

[0162] Having thus described various aspects and embodiments of the technology of the present application, it will be appreciated that various changes, modifications and improvements will readily occur to those of ordinary skill in the art. Such changes, modifications and improvements are intended to be within the spirit and scope of the technology described in the present application. Therefore, it will be appreciated that the foregoing embodiments are presented only by way of example, and within the scope of the appended claims and their equivalents, embodiments of the present invention may be practiced in a manner different from that specifically described. In addition, any combination of two or more characteristics, systems, articles, materials and / or methods described herein is included within the scope of the present disclosure (if these characteristics, systems, articles, materials and / or methods are not mutually contradictory).

[0163] Likewise, as described, some aspects may be embodied as one or more methods. The actions performed as part of the method may be sequenced in any suitable manner. Thus, embodiments may be configured to perform actions in a different order than shown, which may include performing some actions simultaneously, even though shown as sequential actions in illustrative embodiments.

[0164] All definitions, as defined and used herein, should be understood to control over dictionary definitions in documents incorporated by reference and / or ordinary meanings of the defined terms.

[0165] The indefinite articles "a" and "an" as used herein in the specification and claims, unless explicitly stated to the contrary, should be understood to mean "at least one".

[0166] As used herein in the specification and claims, the phrase "and / or" should be understood to mean "one or both" of the elements so conjoined, ie, elements that are present in conjunction in some cases and separately in other cases.

[0167] As used herein in the specification and claims, when referring to a list of one or more elements, the phrase "at least one" should be understood to mean at least one element selected from any one or more elements in the list of elements, but not necessarily including at least one of each element specifically listed in the list of elements, and not excluding any combination of elements in the list of elements. This definition also allows elements to be selectively present other than those explicitly identified in the list of elements to which the phrase "at least one" refers, whether related or unrelated to those explicitly identified elements.

[0168] The terms "approximately" and "about" may be used to mean within ±20% of a target value in some embodiments, within ±10% of a target value in some embodiments, within ±5% of a target value in some embodiments, and within ±2% of a target value in some embodiments. The terms "approximately" and "approximately" may include a target value.

Claims

1. A photonic communication platform, comprising: A photonic network comprising a plurality of optical switches formed on a semiconductor substrate; a plurality of dies in communication with the photonic network; an electronic switch network, comprising a plurality of transistors co-integrated with the plurality of optical switches, the electronic switch network being configured to: At a first time, programming the plurality of optical switches to form a first optical communication path coupling a first subset of the plurality of dies together, wherein programming the plurality of optical switches to form the first optical communication path comprises: identifying optical communication paths coupling a first subset of the plurality of dies together, wherein identifying optical communication paths coupling the first subset of the plurality of dies together comprises identifying optical communication paths providing a bandwidth exceeding a threshold bandwidth; and programming the plurality of optical switches based on the identified optical communication paths; and At a second time after the first time, the optical switch is programmed to form a second optical communication path coupling a second subset of the plurality of dies together, the second optical communication path being different from the first communication path.

2. The photonic communication platform according to claim 1, wherein: The plurality of transistors are formed on the semiconductor substrate.

3. The photonic communication platform according to claim 1, wherein: The semiconductor substrate is a first semiconductor substrate, and wherein the plurality of transistors are formed on a second semiconductor substrate, wherein the first semiconductor substrate and the second semiconductor substrate are 3D-bonded together.

4. The photonic communication platform according to claim 1, wherein: Identifying an optical communication path coupling a first subset of the plurality of dies together further includes monitoring usage of the photonic network.

5. The photonic communication platform according to claim 1, wherein: The electronic switch network is further configured to: determining at least one characteristic of an optical signal at said first optical communication path; identifying a coding scheme based on at least one characteristic of the optical signal; and The photonic network is caused to perform optical communication over the first optical communication path based on the encoding scheme.

6. The photonic communication platform according to claim 1, wherein: The plurality of dies are in electronic communication with the photonic network.

7. The photonic communication platform according to claim 1, wherein: The electronic switch network is also configured to cause the photonic network to optically communicate over the first optical communication path using wavelength division multiplexing.

8. The photonic communication platform according to claim 1, wherein: The photonic network includes a plurality of photonic modules sharing a same waveguide layer layout, wherein a first photonic module of the plurality of photonic modules includes a first optical switch of the plurality of optical switches and a second photonic module of the plurality of photonic modules includes a second optical switch of the plurality of optical switches.

9. The photonic communication platform according to claim 8, wherein: The first subset of the plurality of dies includes a first die and a second die, wherein the first die is in communication with the first photonic module and the second die is in communication with the second photonic module.

10. The photonic communication platform according to claim 9, wherein: The first die is bonded to the semiconductor substrate corresponding to the first photon module, and the second die is bonded to the semiconductor substrate corresponding to the second photon module.

11. A method for operating a photonic communication platform, comprising: Programming, using an electronic switch network including a plurality of transistors, at a first time, a plurality of optical switches formed on a semiconductor substrate to form a first optical communication path coupling a first subset of a plurality of dies together, wherein the plurality of dies are in communication with the plurality of optical switches, and wherein the plurality of transistors are co-integrated with the plurality of optical switches, wherein programming the plurality of optical switches to form the first optical communication path comprises: identifying optical communication paths coupling a first subset of the plurality of dies together, wherein identifying optical communication paths coupling the first subset of the plurality of dies together comprises identifying optical communication paths providing a bandwidth exceeding a threshold bandwidth; and programming the plurality of optical switches based on the identified optical communication paths; and The plurality of optical switches are programmed, using the electronic switch network, at a second time after the first time to form a second optical communication path coupling a second subset of the plurality of dies together.

12. The method according to claim 11, further comprising: determining at least one characteristic of an optical signal at the first optical communication path; identifying a coding scheme based on at least one characteristic of the optical signal; as well as The plurality of optical switches are caused to optically communicate on the first optical communication path based on the encoding scheme.

13. The method of claim 11, further comprising causing the photonic network to optically communicate over the first optical communication path using wavelength division multiplexing.

14. The method of claim 11, further comprising debugging the electronic switch network using a Joint Test Action Group (JTAG) unit.

15. The method of claim 11, further comprising arbitrating between first requests received from die in the first subset and second requests received from die in the second subset.

16. The method of claim 15, further comprising programming the optical switch based on the arbitration.

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