Electrode Stack Structure Preventing Moisture Ingress in Photodiodes
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Solution Overview
Problem
Conventional photodiodes are prone to damage from moisture ingress due to poorly bonded dielectric and anti-reflection layers, especially in high-temperature and high-humidity environments, leading to structural weaknesses around the electrode conduction region.
Innovation Solution
An electrode stack structure is introduced, featuring a semiconductor layer, an inner electrode layer, a dielectric layer, an intermediate metal layer bonded through vapor deposition, and an anti-reflection layer with a groove to ensure airtightness, using materials like gold, titanium, and silicon nitride to maintain electrical conductivity and prevent moisture entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dielectric layer is coated on the sidewall of the semiconductor layer for insulation and passivation, then the photodiode structure is protected, but the bonding between the dielectric layer and anti-reflection layer becomes poor, especially in areas with uneven surfaces, leading to moisture ingress
Solution Approach 1:
An intermediate metal layer is introduced between the dielectric layer and anti-reflection layer to serve as a bonding intermediary. This metal layer has excellent adhesion to both the dielectric layer (via vapor deposition bonding) and the anti-reflection layer, eliminating the poor bonding issue between these two layers and preventing moisture ingress at their interface.
Solution Approach 2:
The patent employs a composite structure consisting of multiple materials (semiconductor layer, dielectric layer, intermediate metal layer, anti-reflection layer) stacked together. Each material is selected for its specific properties, and their combination creates a synergistic effect where the intermediate metal layer enhances overall structural integrity and moisture resistance.
2Loss of energy
If the dielectric layer is made thin to reduce loss, then light transmission is improved, but the layer becomes more irregular in thickness and bonds even worse to the anti-reflection layer, increasing moisture vulnerability
Solution Approach 1:
The intermediate metal layer acts as a reliable bonding mediator that is not sensitive to the thickness variations of the thin dielectric layer. It provides consistent adhesion to both the dielectric layer and anti-reflection layer regardless of the dielectric layer's thickness irregularities, ensuring bonding reliability even when the dielectric layer is made thin to reduce light loss.
3Reliability
If the electrode conduction region is positioned at the highest position for electrical conduction, then electrical performance is improved, but the dielectric layer becomes thinnest at this location, creating the most vulnerable area for moisture entry
Solution Approach 1:
The intermediate metal layer is strategically positioned at the electrode conduction region where the dielectric layer is thinnest. It serves as a protective intermediary that compensates for the reduced dielectric thickness, providing a reliable barrier against moisture while maintaining excellent electrical conduction properties.
Solution Approach 2:
The patent applies local quality enhancement by introducing the intermediate metal layer specifically at the vulnerable electrode conduction region. This localized intervention provides enhanced protection where it is most needed (at the thinnest dielectric area) without affecting other regions of the photodiode structure.
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 electrode stack structure effectively prevents moisture damage, maintains appropriate impedance, and ensures airtightness even when the dielectric layer shifts during formation, simplifying photomask alignment and protecting the photodiode from environmental hazards.
Implementation Method 1
the intermediate metal layer is bonded to the dielectric layer and the inner electrode layer through vapor deposition
Data Source
AI summary
The present invention provides an electrode stack structure capable of preventing moisture from entering a photodiode, comprising: a semiconductor layer; an inner electrode layer provided on the semiconductor layer; a dielectric layer coating a sidewall of the semiconductor layer; an intermediate metal layer provided on, bonded to, and in electrical conduction with the inner electrode layer, wherein the intermediate metal layer has a bottom side extending over and covering a portion of the dielectric layer to provide airtightness; and an anti-reflection layer coating on an outer side of the semiconductor layer, an outer side of the intermediate metal layer, and an outer side of the dielectric layer, with a groove formed in the anti-reflection layer by leaving a predetermined area of a top side of the intermediate metal layer uncoated or by removing a portion of the anti-reflection layer that coats the predetermined area of the top side of the intermediate metal layer, and an outer electrode layer plated on the predetermined area of the top side of the intermediate metal layer.