On-Chip Optical Interconnect Layout With MicroLEDs and Waveguides
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Solution Overview
Problem
Current chip-to-chip interconnects face limitations in density and power dissipation due to fundamental constraints of electrical interconnects, which hinder the performance of high-performance computing and networking systems, while optical interconnects offer potential solutions but are challenging to integrate with standard technology.
Innovation Solution
The integration of optical components into integrated circuit (IC) chips, including a semiconductor substrate with transistors, alternating metal and dielectric interconnect layers, microLEDs, and photodetectors, with light passageways and waveguides to enable high-speed optical interconnects that bypass the limitations of electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If electrical interconnects are used for chip-to-chip connections, then the interconnect structure is simple and easy to manufacture, but the interconnect density is limited and power consumption is high
Solution Approach 1:
The patent replaces electrical interconnects with optical interconnects, substituting the mechanical/electrical field-based signal transmission with optical field-based transmission. This allows for higher density interconnections without the fundamental RC limitations of electrical conductors, while maintaining manufacturability through integration with standard CMOS processes.
Solution Approach 2:
The patent changes the fundamental transmission parameter from electrical signals to optical signals, enabling interconnect density to scale independently of the RC time constant limitations that constrain electrical interconnects. This parameter change allows for higher density while reducing power consumption per bit.
2Ease of manufacture
If electrical interconnects are used for chip-to-chip connections, then the interconnect structure is simple and easy to manufacture, but the power consumption is high
Solution Approach 1:
The patent substitutes optical transmission for electrical transmission, eliminating the I²R power losses inherent in electrical interconnects. Optical interconnects consume power primarily at the transceiver endpoints rather than proportionally to length and density, dramatically reducing overall system power consumption.
Solution Approach 2:
By changing from electrical to optical transmission, the patent alters the power consumption characteristics fundamentally. Optical interconnects enable power-efficient high-density connections by decoupling power consumption from interconnect length and density, unlike electrical interconnects where power loss scales with these parameters.
3Quantity of substance
If optical components are integrated into IC chips, then the interconnect density and speed are improved, but the device complexity increases
Solution Approach 1:
The patent merges optical components (microLEDs, photodetectors, waveguides) with standard CMOS integrated circuit fabrication processes. By integrating these components on the same chip substrate using compatible manufacturing steps, the patent achieves high-density optical interconnects without requiring separate assembly processes, thereby managing device complexity.
Solution Approach 2:
The patent designs optical interconnect components that can be fabricated using standard CMOS process tools and materials where possible, making the optical integration universal with existing semiconductor manufacturing infrastructure. This multi-functionality approach allows the same fabrication platform to produce both electronic and optical components.
4Speed
If optical components are integrated into IC chips, then the interconnect speed and efficiency are improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent combines optical component fabrication with standard CMOS processing steps, utilizing the same precision lithography and deposition tools already optimized for sub-10nm transistor fabrication. This merging ensures that optical component placement and alignment achieve the same manufacturing precision as electronic components without requiring separate high-precision processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables dense parallel optical chip-to-chip interconnects that significantly reduce latency and power consumption, overcoming the limitations of electrical interconnects and enhancing system performance in high-performance computing and networking applications.
Implementation Method 1
a microLED on a pad on the stack of interconnect layers, with at least one electrical connection coupling the pad and at least one transistor of the semiconductor substrate
Implementation Method 2
a photodetector integrated in the semiconductor substrate, with a light passageway to the photodetector through the stack of interconnect layers
Implementation Method 3
a first waveguide on the stack of interconnect layers, the first waveguide extending over the light passageway to the photodetector through the stack of interconnect layers
Data Source
AI summary
Optical interconnects for IC chips may include optical sources and receivers integrated with the IC chips. MicroLEDs may be mounted on an interconnect layer of the IC chip, and embedded within a waveguide. Photodetectors to receive light from the waveguide may be fabricated in a top surface of a semiconductor substrate, below a level of the interconnect layer, but with a passageway for light through the interconnect layer.