Stacked Photo Relay Layout for High-Frequency Signal Transmission
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Solution Overview
Problem
Existing photo relay devices face challenges in maintaining high-frequency transmission characteristics due to coupling capacitances and open stub effects, which deteriorate signal transmission at frequencies above 1 GHz.
Innovation Solution
The photo relay device configuration includes a light receiving element and a light emitting element disposed above the MOSFETs, reducing coupling capacitances and shortening interconnect lengths, thereby improving high-frequency transmission characteristics and allowing for device downsizing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the light receiving element and light emitting element are disposed close to the MOSFETs, then the coupling capacitances increase and interconnect lengths increase, but this makes the device structure more compact
Solution Approach 1:
The patent transitions from a planar layout to a three-dimensional stacked configuration, placing the light receiving element and light emitting element on different layers above the MOSFETs. This vertical arrangement reduces the horizontal area occupation while maintaining short interconnect lengths and minimizing coupling capacitances, thus resolving the contradiction between device compactness and high-frequency transmission characteristics.
2Reliability
If the interconnect lengths are increased to reduce coupling capacitances, then high-frequency transmission characteristics improve, but the device area increases
Solution Approach 1:
By stacking components vertically across multiple layers, the patent achieves short interconnect lengths without increasing the horizontal device footprint. The light receiving element and light emitting element are positioned directly above the MOSFETs in the vertical dimension, minimizing the distance for signal transmission while maintaining a compact planar area.
3Reliability
If the coupling capacitances are reduced for better high-frequency performance, then signal transmission above 1 GHz improves, but the layout complexity increases
Solution Approach 1:
The stacked configuration naturally minimizes coupling capacitances by reducing the horizontal separation between components and optimizing their vertical positioning. This geometric arrangement inherently achieves low coupling capacitance without requiring complex routing or additional shielding structures, thus improving high-frequency performance while maintaining layout simplicity.
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 configuration enhances high-frequency signal transmission by reducing coupling capacitances and shifting the influence of open stubs to higher frequency regions, while also reducing the device's installation area.
Implementation Method 1
a light emitting element (50)... In response to a voltage applied between both electrodes of the light emitting element, light is emitted from a light emitting surface provided on one electrode
Implementation Method 2
a light receiving element (30)... a light receiving surface... the light receiving element and the light emitting element are disposed so as to face each other
Data Source
AI summary
According to one embodiment, a semiconductor device includes: a first substrate; a first transistor provided on the first substrate; a light receiving element; and a light emitting element provided on the light receiving element, wherein the first substrate, the first transistor, the light emitting element, and the light receiving element are disposed sequentially in a first direction.