Single-Photon Avalanche Diode Isolation Structure for Lower Dark Current
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Solution Overview
Problem
Single-photon avalanche diodes face issues with oxide pilling and defect-induced dark current due to complex trench-based formation processes, which can lead to particulate contamination and reduced detection probability.
Innovation Solution
A semiconductor structure for a single-photon avalanche diode is formed with a semiconductor substrate, a semiconductor layer, a doped region, and a deep trench isolation structure that includes a dielectric liner and a conductor layer, eliminating the need for trench filling and simplifying the process by positioning the absorption and multiplication regions outside deep trenches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a trench-based formation process is used to create absorption and multiplication regions, then the single-photon avalanche diode can be formed with proper structural isolation, but oxide pilling occurs causing particulate contamination and defect-induced dark current
Solution Approach 1:
The patent extracts the harmful oxide pilling problem by eliminating the trench filling step entirely. Instead of filling trenches with silicon dioxide and then patterning, the invention uses shallow trench isolation with dielectric material deposited only where needed, removing the source of oxide pilling and particulate contamination that causes defects and dark current.
Solution Approach 2:
The patent replaces the complex, multi-step trench-based formation process with a simpler, more robust shallow trench isolation approach. This simplified process uses readily available dielectric materials and standard deposition techniques, reducing manufacturing complexity and eliminating the need for multiple masks and dry etches while maintaining device performance.
2Object-affected harmful factors
If the thickness of epitaxially-grown semiconductor material is reduced to reduce oxide pilling, then oxide pilling is reduced, but detection probability is adversely reduced
Solution Approach 1:
The patent applies local quality by creating distinct regions with different dielectric properties. The shallow trench isolation uses dielectric material with appropriate breakdown voltage characteristics localized to specific areas, allowing the absorption and multiplication regions to maintain optimal thickness for photon detection while being properly isolated electrically. This local differentiation enables both reduced oxide pilling and maintained detection probability.
3Manufacturing precision
If a complex process with multiple masks, multiple dry etches, and chemical mechanical polishing is used to form the trench-based structure, then the absorption and multiplication regions can be formed in deep trenches, but the fabrication complexity increases and defect risk is elevated
Solution Approach 1:
The patent segments the isolation structure into shallow trenches that are filled with dielectric material, rather than using a single deep trench approach. This segmentation allows the absorption and multiplication regions to be formed separately and independently, eliminating the need for multiple masks and complex etching sequences while maintaining precise structural formation through simpler, more controlled deposition 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 reduces optical and electrical crosstalk, minimizes defects, and enhances detection probability by simplifying the fabrication process, reducing the risk of oxide pilling and particulate contamination, and allowing for a more compact pixel size.
Implementation Method 1
A single-photon avalanche diode is biased well above its reverse-bias breakdown voltage. When a single-photon avalanche diode is placed under such a high reverse bias, photon-initiated 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. A large avalanche of current carriers grows exponentially
Implementation Method 2
photon-initiated carriers are accelerated by the electric field. A single-photon avalanche diode can detect single photons providing short duration current pulses
Data Source
AI summary
Structures for a single-photon avalanche diode and methods of forming a structure for a single-photon avalanche diode. The structure includes a semiconductor substrate having a top surface, a semiconductor layer on the top surface of the semiconductor substrate, a light-absorbing layer on a portion of the semiconductor layer, and a doped region in the portion of the semiconductor layer. The doped region is positioned in the portion of the semiconductor layer adjacent to the light-absorbing layer.