Integrated SPAD Trench Structure for Smaller Chip Area
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Solution Overview
Problem
Existing semiconductor device fabrication techniques for single-photon avalanche diodes (SPADs) result in large footprints and significant chip area consumption due to the need for large transistors and deep trench isolation regions.
Innovation Solution
A structure comprising a semiconductor substrate with a trench and a deep trench isolation region that includes a dielectric layer and a semiconductor layer inside the trench, along with an active device featuring a doped region in the semiconductor layer, is proposed. This configuration reduces the overall size of the SPAD while maintaining its functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a transistor is used to control the operation of the single-photon avalanche diode, then the SPAD operation can be controlled, but the transistor consumes significant chip area
Solution Approach 1:
The patent merges the transistor and SPAD into a single integrated structure where the transistor is formed within the same semiconductor layer as the SPAD. The transistor gate controls the SPAD operation while sharing the same substrate and isolation structures, eliminating the need for separate discrete components and reducing total chip area.
Solution Approach 2:
The semiconductor layer serves multiple functions: it forms both the active region of the SPAD and the transistor structure. The same dielectric layer provides isolation for both devices. This multi-functionality reduces the overall component count and chip area required.
2Reliability
If deep trench isolation regions are used to electrically isolate the single-photon avalanche diode, then electrical isolation is achieved, but significant chip area is consumed
Solution Approach 1:
The isolation structure is merged to serve both the SPAD and transistor simultaneously. A single dielectric layer within a shared trench provides electrical isolation for both devices, eliminating the need for separate isolation regions for each component and reducing total chip area.
Solution Approach 2:
The deep trench isolation region performs dual functions: it electrically isolates the SPAD from surrounding structures and simultaneously isolates the transistor. This multi-functional isolation structure reduces the total area required compared to separate isolation regions for each device.
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
The proposed solution allows for a more compact and efficient integration of SPADs and transistors, reducing chip area consumption and enabling the formation of smaller, more efficient semiconductor devices.
Implementation Method 1
A single-photon avalanche diode can detect single photons providing short duration current pulses
Implementation Method 2
photon-initiated charge carriers are accelerated by the electric field to a kinetic energy that is large enough to knock electrons out of atoms of the bulk material and generate additional charge carriers that may exponentially grow to generate an avalanche of charge carriers
Data Source
AI summary
Structures including a single-photon avalanche diode and methods of forming such structures. The structure comprises a semiconductor substrate including a trench. The trench surrounds a portion of the semiconductor substrate. The structure further comprises a deep trench isolation region that includes a dielectric layer and a semiconductor layer inside the trench. The dielectric layer is disposed between a sidewall of the trench and the semiconductor layer. The structure further comprises an active device that includes a doped region in the semiconductor layer.