Abstract:
Disclosed is an integrated circuit comprising a plurality of cores attached to at least one transmitter and receiver, an optical transmission network embedded within the wire levels of the integrated circuit, and wherein the transmitter and receivers send and receive data on the network. Also disclosed is a method of transmitting signals within an integrated circuit comprising an integrated circuit comprising a plurality of cores and optical paths, selecting an optical path from the plurality of optical paths for transmitting data, and transmitting the data on the selected optical path. Also disclosed is an integrated circuit comprising an optical transmission network, a plurality of cores, and a plurality of controllers, all three being operatively attached to each other.

Description:
BACKGROUND OF INVENTION  
     FIELD OF INVENTION  
       [0001]     This invention relates generally to using a fiber optic medium within a SOC (i.e., System On Chip) silicon dioxide layer of a chip to transmit light thereby serving as a signal transmission means within the chip.  
       BACKGROUND OF INVENTION  
       [0002]     In the field of integrated circuit construction, in general, and in the construction of large ASIC&#39;s (i.e., Application Specific Integrated Circuit), in particular, the wiring distance between cores has become greater and greater as the space or paths to physically run the numerous wiring becomes more and more impinged upon due to overcrowding by additional cores. A resultant disadvantage is that latency problems occur wherein a signal fails to be latched onto the receiving core within the current clock cycle.  
         [0003]     Accordingly, there is a need in the field of ASIC&#39;s for an improved way for communicating that overcomes the aforementioned, and other, disadvantages.  
       SUMMARY OF INVENTION  
       [0004]     The present invention provides an integrated circuit using an optical transmission network and a method for transmitting data using the optical transmission network.  
         [0005]     A first general aspect of the invention provides an integrated circuit comprising: 
        a plurality of cores operatively attached to at least one transmitter and at least one receiver;     an optical transmission network embedded within at least one wire level of the integrated circuit;     said at least one transmitter for sending data on said optical transmission network; and     said at least one receiver for receiving data on said optical transmission network.        
 
         [0010]     A second general aspect of the invention provides a method of transmitting signals within an integrated circuit comprising: 
        providing said integrated circuit, wherein said integrated circuit includes a plurality of cores and a plurality of optical paths;     selecting an optical path from said plurality of optical paths for transmission of data; and     transmitting data on said selected optical path.        
 
         [0014]     A third general aspect of the present invention provides an integrated circuit comprising: 
        an optical transmission network;     a plurality of cores operatively attached to said optical transmission network; and     a plurality of controllers operatively attached to said optical transmission network and said plurality of cores.        
 
         [0018]     The foregoing and other features of the invention will be apparent from the following more particular description of various embodiments of the invention. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0019]     Some of the embodiments of this invention will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:  
         [0020]      FIG. 1A  depicts a top view of a fiber optic transmission layer, in accordance with an embodiment of the present invention;  
         [0021]      FIG. 1B  depicts an alternative embodiment of the same view as  FIG. 1A , in accordance with an embodiment of the present invention;  
         [0022]      FIG. 1C  depicts a third embodiment of the same view as  FIG. 1A , in accordance with an embodiment of the present invention;  
         [0023]      FIG. 2A  depicts a side sectional view of die showing multiple fiber transmission layers, in accordance with an embodiment of the present invention;  
         [0024]      FIG. 2B  depicts an alternative embodiment of the same view as  FIG. 2A , in accordance with an embodiment of the present invention;  
         [0025]      FIG. 3  depicts a schematic top view of a fiber transmission layer along with a plurality of transmitters and receivers connected thereto, in accordance with an embodiment of the present invention;  
         [0026]      FIG. 4  depicts a functional diagram of a portion of a fiber optic network, in accordance with an embodiment of the present invention;  
         [0027]      FIG. 5  depicts a flow chart of a communication method, in accordance with an embodiment of the present invention;  
         [0028]      FIGS. 6A, 6B ,  6 C depict top views of various bumps, in accordance with an embodiment of the present invention;  
         [0029]      FIGS. 7A, 7B ,  7 C depict side views of the corresponding views depicted in  FIGS. 6A, 6B ,  6 C, respectively, in accordance with an embodiment of the present invention;  
         [0030]      FIG. 8  depicts a larger side sectional view of  FIG. 7C , in accordance with an embodiment of the present invention;  
         [0031]      FIGS. 9A, 9B , and  9 C depict various configurations of redirection terminations, in accordance with an embodiment of the present invention;  
         [0032]      FIG. 10  depicts a side sectional close up view of a portion of a die employing some of the redirection terminations, in accordance with an embodiment of the present invention; and  
         [0033]      FIG. 11  depicts a side sectional close up view of an edge of a die, in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0034]     Although certain embodiments of the present invention will be shown and described in detail, it should be understood that various changes and modifications may be made without departing from the scope of the appended claims. The scope of the present invention will in no way be limited to the number of constituting components, the materials thereof, the shapes thereof, the relative arrangement thereof, etc., and are disclosed simply as an example of an embodiment. Although the drawings are intended to illustrate the present invention, the drawings are not necessarily drawn to scale.  
         [0035]     The present invention provides for an improved integrated chip design.  
         [0036]     General:  
         [0037]     Integrated Chips (i.e., IC), as currently configured have several disadvantages. Integrated chips are getting more and more dense and more complex. The number of active circuits in a given area of the chip is increasing, as is the amount of connectivity of the integrated circuit. Studies have shown that as the number of vias connecting metal layers further increases, a point will be reached wherein the further adding of additional levels of metal connectivity layers will not, in turn, significantly increase the amount of connections because the new level of vias will not have available any connection path to the lower metal levels due to the previously open, available areas now being blocked by wires or vias. Current silicon is reaching a constraint of physical distance and RC load limits, where an alternative cross chip means of communication is desired. In sum, the IC, as currently configured, is heading to the point wherein eventually there will be no room at the IC.  
         [0038]     The wiring in current IC&#39;s is a problem. Relatively speaking the wiring creates slow communication across a die. The requirement of using buffers, which effectively is part of the virtual wiring results in effective wiring delay.  
         [0039]     A solution to this problem, as the present invention provides, is to use the oxide, which is currently silicon dioxide or glass, between the metal layers, as a transmission means for transmitting (i.e., sending and receiving) optical signals from one device to another. An optical transmission path would not necessarily be shaped, but instead use diffusion of light through the oxide medium to go from an optical transmitter to an optical receiver.  
         [0040]     Thus, the present invention effectively is replacing the traditional wiring and buffers in the IC with optical fibers and cores. Amongst other resultant improvements, the cycle time is improved across the die. Other improvements include: no heat generation in the circuitry, little signal loss, communication without electrical noise, and the capability of having N number of channels for transmission.  
         [0041]     Currently, vias substantially limit wireability as the number of metal layers increases (and therefore the number of vias increase too). In the present invention, however, by using an oxide plane for the optical signals, the transmitted light can diffuse around the existing vias. This ability in the present invention creates the added benefit of thereby allow for the further increase of the number of layers in an IC that can be used for traditional wiring.  
         [0042]     Ultimately, the present invention creates a faster ASIC (i.e., Application Specific Integrated Circuit) that overcomes latency problems, a more powerful ASIC, and an ASIC with more functionalities.  
         [0043]     Specifics:  
         [0044]     Turning to the enclosed figures,  FIGS. 1A, 1B , and  1 C depict top views of various embodiments of possibly layouts of a layer, or plane, of fiber optic channels, tunnels, or wires to be used within an ASIC. A fiber optic network  9  (See e.g.,  FIGS. 2, 10 ,  11 ), within an IC is made up of one, or more, layers, planes, or grids, denoted by a  10 . Single fiber optic fibers  12  make up the grid  10 . The fiber optic fibers  12  may be made of any suitable optical transmission medium, either typically now found in IC&#39;s or as an added or improved upon feature. For example, the fiber optic fibers  12  may be made of silicon dioxide, glass, etc. As  FIGS. 1A, 1B , and  1 C all indicate, the fibers  12  may be run in numerous configurations. For example,  FIGS. 1A and 1B  show how the fibers  12  in grid  10  can be parallel or perpendicular to itself, or some combination of the two.  FIG. 1C  shows that the density of the fibers  12  within  10  can differ, as well, for in  FIG. 1C  the density of fibers  12  is much higher than in the embodiments in  FIGS. 1A and 1B . It should be apparent to one skilled in the art, that there is virtually an infinite variety of grids  10  conceivable wherein the location, density, direction of the fibers  12  can differ and vary.  
         [0045]     While  FIGS. 1A, 1B , and  1 C show a single layer, or plane,  10  of fibers  12 , the fibers  12 , in the present invention, can traverse across multiple layers within the ASIC, following an essentially vertical configuration, as well. For example,  FIGS. 2A and 2B , depict side sectional views of portions of a die, or ASIC,  5 . A fiber network comprises the plurality of fiber layers  10 . As seen, the optical fibers  12  can traverse the various layers of the die  5  in a plurality of directions and configurations. For example,  FIG. 2A  shows a plurality of glass levels  10 A,  10 B,  10 C,  10 C made up of optical fibers  12 . The glass fibers  12  run in a first direction in the top glass level  10 A, as depicted by directional arrow  11 A. Conversely, the optical fibers  12  in the bottom glass level  10 C run in a second direction, as depicted by directional arrow  11 B. Note that directional arrows  11 A and  11 B run in different directions. The angle between directional arrows  11 A,  11 B can be 90 degrees, acute, or obtuse.  FIG. 2B  shows sectional side view of a portion of a die, in this embodiment wherein the glass fibers  12  run in different directions in successive layers, and in the same direction in layers  10 A,  10 C, or in layers  10 B,  10 C. See, for example, directional arrows  11 C,  11 D for glass fibers  12  in layers  10 A and  10 D.  
         [0046]     Turning to  FIG. 3  which depicts a schematic top view of a portion of a die  5 , showing one layer  10  of fibers  12  with associated elements. Located within the fiber layer, or plane  10  are a plurality of drivers  20 , or optical transmitters, and optical receivers  30 . The optical transmitters  20  and optical receivers  30  are coupled to the fiber layer  10  which is, in turn, connected to the other fiber layers  10  within the ASIC  5 . A single fiber layer  10  (if there is only one fiber layer  10  within the ASIC  5 ) or the plurality of fiber layers  10  thus make up an entire fiber optic network  9  (not shown) within the ASIC  5 . A plurality of local fiber optic controllers  40  (See  FIG. 4 ) act as routers and arbiters between the fiber optic channels  10  and a plurality of cores  50  (See  FIG. 4 ) within the ASIC  5 . The term core  50  (See e.g.,  FIG. 4 ), as used herein, refers to a particular section of logic. The controllers  40  are responsible for choosing an optimal fiber optic channel  12  to reach the destination core  50 . The controllers  40  can communicate with a single core  50 , or a plurality of cores  50 , as well as a pair of optical transmitters  20  and optical receivers  30 . The controller  40 , along with their respective optical transmitter  20  and optical receiver  30  can be located as needed on the ASIC  5 . For example, a desired location for a particular controller  40  on the ASIC  5  would be where there is a greater need for latency-free communication between cores  50 .  
         [0047]      FIG. 4  shows a conceptual view of a particular portion of an ASIC  5  showing the communication via fiber optic lines  12  (e.g.,  12 A,  12 B) between just two cores  50  (e.g.,  50 A,  50 B), presuming that the two particular cores  50 A,  50 B in  FIG. 4  need to communicate with each other. A first, or source core,  50 A needs to read data from the second, or destination core  50 B. Each core  50 A,  50 B have affiliated drivers  20 , and receivers  30 . For example, drivers  20 D,  20 E,  20 F and receivers  30 D,  30 E are affiliated with core  50 B. Conversely, drivers  20 A,  20 B,  20 C and receivers  30 A,  30 B,  30 C are affiliated with core  50 A. During a first clock cycle, the first core  50 A will send a read address, control and transfer qualifier bits to a local fiber optic controller  40 A. The fiber optic controller  40 A determines which fiber optic channel ( 12 A or  12 B) should be used for transmission to the desired destination core, namely the second core  50 B. In  FIG. 4  the controller  40 A determines that fiber optic channel  12 A shall be used for transmission. Various reasons that a controller  40  will select a particular fiber optic channel  12  over another fiber optic channel  12  include that one channel  12  may be defective, one channel  12  may have a different (e.g., shorter) length than other channels  12 , etc. The fiber optic controller  40 A then send the data to the appropriate transmitter, or driver  20 , in this case driver  20 A. The driver  20 A, in turn, encodes the data for fiber optic transmission and drives the optical data packet through the fiber optic channel  12 A specified by the controller  40 A. The controller&#39;s  40 A corresponding optical receiver  30 , in this case specifically  30 D, then decodes the returning handshake and lets the controller  40 A know that the transmission of data was either successful or needs to be retransmitted. This reply back to the controller  40 A is done from driver  20 D back to receiver  30 A, via fiber optic channel  12 B. If the transfer was successful, the controller  40 A sends a type of ACK (i.e., acknowledgment) signal back to the source core  50 A. If, however, the transmission was unsuccessful, then the controller  40 A can take steps to retry the transmission. If there is a collision in the attempted transmission, the controller  40 A could choose a secondary fiber optic path  12  (not shown). If an error existed in the data itself or if the receiving core  50 B was busy, the controller  40 A could simply retry a transmission again.  
         [0048]     Some additional features could be provided with the present invention. An error checking scheme could be included thereby allowing recovery of the sent data if there are collisions and/or incorrect transmissions. Additionally, there could be snoopers along the fiber optic network  10  which could decode addresses to ensure cache coherency. Also, features from traditional bus arbitration architecture could be added such as core abort mechanisms, timeout errors, and retry signals.  
         [0049]      FIGS. 6A, 6B , and  6 C show top views of a progression of the construction of an optical medium connection, in accordance with the present invention.  FIGS. 7A,7B , and  7 C show side views of the same corresponding constructs shown in  FIGS. 6A-6C , respectively. In all six figures, on an oxide passivation surface  60  is attached a bump  15 . In  FIGS. 6B and 7B  is shown a bump  15  which has been etched in half, thereby producing an etched face  16 . As  FIGS. 6C and 7C  show a optical fiber  12  is connected to the etched face  16  of the bump  15 . The light transmitted  200  is thus able to be sent along the optical fiber  12  and upon reaching the etched bump  15  turns vertically wherein the light  200  is able to be sent to other levels (not shown) and ultimately on to the optical detector circuit, specifically the receiver  30 .  
         [0050]      FIG. 8  shows a broader view of the detailed connection of  FIGS. 6C and 7C  and its relationship to a portion of an ASIC  5 . Numerous Damascene wires  320  are connected to traditional (i.e., metal) vias  310  amongst the plurality of oxide passivation surfaces  60 . As the present invention provides, and  FIG. 8  indicates, light  200  transmitting along a fiber  12  from a transmitter  12  (not shown) through a bump  15  and on to receiver(s)  30 . In so doing, however, the transmitted light  200  is able to readily avoid the various constructs such as the wires  320  and vias  310 .  
         [0051]     There is a need in the present invention for redirecting the transmitted light  200 . One example of a location where this redirection occurs is when transmitted light  200  is required to leave a particularly glass layer, or plane  10 . Another example of this is when transmitted light  200  must turn, or be redirected, onto a particular, required glass layer  10 . Thus, a redirection termination  17  acts much like a reflector of sorts. There are numerous shapes for redirection terminations  17 , several depicted in  FIGS. 10A, 10B , and  10 C. The redirection terminations  17  which is made from a reflective material, such as metal, and is configured so as to produce, or allow, a reflection of the transmitted light  200  signal either onto or off of a light level  10 . The redirection terminations  17  can be curved, or hemispherical ( FIG. 9A ), slanted ( FIG. 9B ), V or cone-shaped ( FIG. 9C ), or another suitable shape for redirecting the light signal  200 . The various redirection termination  17  configurations also offer an advantage of minimizing the transmit strength required for the light source.  
         [0052]      FIG. 10  similarly shows a sectional side view of a portion of an ASIC  5  employing aspects of the present invention. The portion of the ASIC  5  shown has a plurality of metal layers  300 A,  300 B,  300 C and a fiber optic network  9  comprised of a plurality of glass layers  10 A,  10 B,  10 C interspersed amongst the metal layers  300 A,  300 B,  300 C. A particular section of logic (i.e., core  50 )(See e.g.,  FIG. 4 ) would contain an optical transmitter  20  (See e.g.,  FIG. 4 ) that can transmit light  200  within a particular glass layer  10 A. Suppose a signal, in the form of transmitted light  200  is required to be sent from the transmitter  20  at the first glass layer  10 A to a receiver  30  (See e.g.,  FIG. 4 ) on the third glass layer  10 C. In order to redirect the transmitted light  200  from the first glass layer  10 A to the third glass layer  10 C a means must be created that allows the transmitted light  200  to be redirected, or reflected, out of the first glass layer  10 A, then in the direction of the third glass layer  10 C, and then onto the third glass layer  10 C where the desired receiver  30  resides. Thus, a light path  18 , with the use of a redirection termination(s)  17 , provides the requisite redirectioning of light. This light path, although functionally similar to a metal via, is constructed from a material that allows for the transmission of light through it. Because this light path, or light via  18 , can be constructed of the same material as the glass layers  10 A,  10 B,  10 C, an added advantage of the invention is that the thermal contraction and expansion constants between the various glass layers  10 A,  10 B,  10 C and the light via(s)  18  would be the same which prevents thermal stresses that would otherwise result from differential coefficient of thermal expansion under temperature-varying conditions.  
         [0053]     Thus, as  FIG. 10  depicts a light signal  200  could originate from a transmitter  20  on the first glass layer  10 A. The transmitted light  200  would approach a redirection termination  17 B (i.e., slant-shaped) causing the light  200  to be reflected out of the first glass layer  10 A and along a light via  18 . When the transmitted light  200  reaches the destination third glass layer  10 C, the light  200  reflects off of a second redirection termination  17 A (i.e., hemispherical-shaped). The transmitted light  200  then is appropriately transmitted along the third glass layer  10 C to receiver  30 . It should be apparent to one skilled in the art, that various shaped redirection termination  17 A,  17 B,  17 C (See  FIGS. 9A, 9B ,  9 C) can be used, as can a plurality of light vias  18 .  
         [0054]     Thus, optic transmitters  20  (See e.g.,  FIG. 4 ) can direct light signals  200  upwards (or downwards) onto a redirection termination, or dispersion, device  17 , wherein the redirection device  17  scatters the light across the optic plane  10 . As a result, all receivers  30  (See e.g.,  FIG. 4 ) will be able to detect the transmission. The redirection device  17  can be spherical in shape in order to ensure even dispersal of the light. The receiver  30  can also utilize a lens for light gathering. In order to avoid interference from light reflections and to create signal attenuation, the base of the optic plane(s)  10  can be made, or coated, with a non-reflective material. Thus, the light-absorbing attribute of the base of the optic plane  10  will reduce the number of times a signal reflects around the optic plane  10 .  
         [0055]     An LED can be used as the optical transmitter  20 . The selection of the particular type of LED used as the transmitter  20  affects the wavelength of the light signal  200 . As a result, an embodiment can have multiple light signals of differing frequencies propagating simultaneously to multiple receivers  30  without impeding, or interfering, with each other. This can be done also all within a single oxide layer  10 . For example, for each pair of cores  50  that wish to communicate with each other, there could be a separate wavelength of light for that particular pair of cores  50 . As a result, the communication between two particular cores  50  would not require overhead for decoding or arbitration since the communication can flow freely between those two particular cores  50 , while other light frequencies are being used by other cores  50 .  
         [0056]     For purposes of this invention, it should be noted that the frequencies of light that can transmitted through the optical fibers  12  in the present invention include electromagnetic waves in both the visual spectrum (i.e., about 3.8×10 14 −7.5×10 4  Hz) and infrared radiation (i.e., about 10 11 −3.8×10 4  Hz). Thus, the term light, light signal, etc., as used in this disclosure includes both infrared radiation and visible spectrum electromagnetic radiation.  
         [0057]     In  FIG. 11  shows an embodiment of an ASIC  5 , detailing an edge of the passivation  65  of the ASIC  5 , in accordance with the present invention. The feature shown in  FIG. 11  indicates one way that the present invention will dump the photons from the various oxide levels  10  once the light signals  200  have been transmitted and received (i.e., used). The plurality of oxide levels  10  and metal levels  300  are shown above several active circuits  7  on the ASIC  5 . Thus, the beveled oxide, or glass, edge  65  serves as a type of light sink, wherein the light signals  200  are absorbed, or dumped into the oxide edge  65  and/or ultimately off the edge  6  of the chip  5 . An oxide edge  65  near the chip edge  6  is beveled at an angle, Θ, to fully reflect the light  200  further down into the glass, or oxide edge  65 . The angle of reflection, Θ, will differ depending on the particular index of refraction of the material used in the oxide edge  65 . In essence, this feature prevents the recirculation of light  200  back into the plurality of oxide layers  10  and metal layers  300  once the light has been transmitted and received appropriately by the transmitters  20  and receivers  30 .  
         [0058]     Communication Protocol:  
         [0059]      FIG. 5  depicts a flow chart for a method for communicating using the present invention of transmitting data via a fiber optic medium  12  (See e.g.,  FIG. 4 ). The flow chart  100  starts with a sending step  105 , wherein a sending, or source core  50  (See e.g.,  FIG. 4 ) sends a request with an address and control signals to its respective controller  40  (See e.g.,  FIG. 4 ). In the second step  110 , the controller  40  both decodes the desired destination and determines the best driver, or optical transmitter  20  (See e.g.,  FIG. 4 ), on which to send the signals. Then in step  115 , the driver  20  sends the request, data and address to a optical receiver  30  (See e.g.,  FIG. 4 ). At the decision step  120 , a determination as to whether the receipt of the transmission sent in step  115  is made. If the receipt at the optical receiver  30  is not successful, then step  115  is re-executed. How-ever, if the transmission to the optical receiver  30  is successful, then step  130  is next executed. In step  130 , data is decoded and sent on from the optical receiver  30  to destination controller  40 . Upon receipt of the decoded data, the destination controller  40  sends in step  140  an acknowledgment (i.e., ACK), or data, depending on the request, back to the source.  
         [0060]     The present invention can use a communication protocol that can consist of initiated pulse patterns such that the recipient device (i.e., core  50 ) would recognize its optical i.d., so that all subsequent communications would be received by that particular recipient core  50 . The communication transmission could be terminated by a pulse gap, for example. Other communications schemes could be employed that use common media.  
         [0061]     This communication protocol could be used from multiple transmitters  20  with multiple receivers  30  per glass layer  10  or separated by non-opaque regions on the same layer  10 . The communication can be accomplished by using the same frequency of light while employing a collision protocol, or by using differing frequencies of light for tuned receivers  30 . See e.g.,  FIG. 3 . Another advantage of the present invention is that communication signals can send data packets with an I.D., control segments, and data segments all within the same packet; whereas previously data and control segments were sent separately. This results in more efficient communication transmission.  
         [0062]     While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention as defined in the following claims.