3D Multi-Chip Module With Vertical Optical Interconnects
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Solution Overview
Problem
Existing multi-chip modules (MCMs) are limited to two-chip layers due to optical proximity communication requirements, constraining device density, performance, form factor, and cost.
Innovation Solution
A three-dimensional MCM is achieved through optical interconnects using substrates with optical waveguides and couplers that redirect signals out of the plane, enabling vertical stacking of multiple chips and overcoming the two-chip layer constraint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If optical proximity communication is used between active surfaces, then optical interconnect functionality is achieved, but the number of chip layers is limited to two
Solution Approach 1:
The patent transitions from two-dimensional planar optical coupling to three-dimensional vertical coupling by introducing optical waveguides that extend through the substrate thickness. This allows optical signals to propagate in the vertical dimension (z-direction) rather than only in the plane of the chip surfaces, enabling stacking of multiple chip layers beyond the two-chip limitation.
Solution Approach 2:
The patent introduces substrate-integrated optical waveguides as intermediary structures that mediate optical signal transmission between chips. These waveguides act as guided pathways that couple optical signals from one chip's active surface to another chip's active surface through the substrate, enabling indirect optical communication that overcomes the direct surface-to-surface coupling limitation.
2Ease of operation
If two-dimensional multi-tiered array is used, then optical proximity communication is enabled, but device density is constrained
Solution Approach 1:
The patent enables three-dimensional stacking of chips by implementing vertical optical interconnects through substrate waveguides. This transitions the architecture from two-dimensional lateral arrangement to three-dimensional vertical stacking, significantly increasing device density by utilizing the vertical dimension for additional chip layers.
3Reliability
If direct optical surface coupling is used, then optical signal transmission is achieved, but vertical stacking beyond two chips is constrained
Solution Approach 1:
The patent introduces optical waveguides integrated into the substrate as intermediary transmission channels. These waveguides provide reliable optical signal transmission between vertically stacked chips by guiding light through the substrate thickness, replacing the need for direct surface-to-surface coupling and enabling extended vertical stacking.
Solution Approach 2:
The patent implements optical signal propagation in the vertical dimension (z-direction) through substrate waveguides, rather than relying on direct horizontal surface coupling. This dimensional transition enables reliable optical transmission across multiple vertical chip layers.
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 solution increases device density, reduces latency and power consumption, and allows for smaller form factors while enabling hybrid integration of different functional layers and components.
Implementation Method 1
the first optical coupler redirects an optical signal from the first optical waveguide to a first direction, or from the first direction to the first optical waveguide, where the first direction is other than in the plane of the first surface
Data Source
AI summary
A multi-chip module (MCM) includes a stack of chips that are coupled using optical interconnects. On a first surface of a middle chip in the stack, there are: a first optical coupler, an optical waveguide, which is coupled to the first optical coupler, and a second optical coupler, which is coupled to the optical waveguide. The first optical coupler redirects an optical signal from the optical waveguide to a first direction (which is not in the plane of the first surface), or from the first direction to the optical waveguide. The second optical coupler redirects the optical signal from the optical waveguide to a second direction (which is not in the plane of the first surface), or from the second direction to the optical waveguide. An optical path associated with the second direction passes through an opening in a substrate in the middle chip.