Stacked SPAD Sensor Electrical Insulation Design
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Solution Overview
Problem
Conventional SPAD sensor devices face challenges in maximizing sensitivity and reliability due to inadequate electrical insulation, leading to potential shorting issues during dicing and packaging, which affects device performance and flexibility.
Innovation Solution
A stacked SPAD sensor device design featuring a sensor layer with SPAD pixels and a logic layer separated by insulation regions, including insulation walls and a bonding layer with electrical connectors, to provide effective electrical insulation and prevent shorting, allowing for improved device reliability and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SPAD sensor devices are used without adequate electrical insulation, then device structure is simpler, but electrical shorting occurs during dicing and packaging leading to reduced reliability
Solution Approach 1:
The device is divided into distinct functional layers (sensor layer, logic layer) separated by insulation regions. The insulation region is further segmented into insulation walls that physically divide and electrically isolate different circuit elements, preventing shorting while maintaining structural organization
Solution Approach 2:
An insulation region acts as an intermediary layer between the sensor layer and logic layer. This intermediate structure provides electrical insulation without preventing necessary electrical connections through bonded through-regions, thus resolving the contradiction between isolation and connectivity
2Reliability
If insulation regions are added to prevent electrical shorting, then device reliability improves, but manufacturing complexity increases
Solution Approach 1:
The insulation region serves multiple functions simultaneously: it provides electrical insulation, acts as a structural support, and defines bonding areas. By merging these functions into a single integrated structure, the manufacturing process is simplified despite the added functionality
3Adaptability or versatility
If stacked sensor and logic layers are bonded together, then device integration is improved, but electrical insulation between layers becomes more difficult to maintain
Solution Approach 1:
The insulation structure has varying properties in different locations: insulation walls provide complete isolation in certain areas, while bonded through-regions allow electrical connections in other areas. This local differentiation of insulation quality enables both integration and electrical isolation
Solution Approach 2:
The insulation problem is solved by transitioning from a two-dimensional planar insulation approach to a three-dimensional stacked architecture with vertical insulation walls and bonded through-regions. This dimensional change allows simultaneous insulation and connection
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 solution enhances device reliability and performance by preventing electrical shorting, simplifying dicing and packaging, and increasing implementation flexibility, while maintaining compatibility with existing manufacturing processes and systems.
Implementation Method 1
a bonding layer characterized by a third thickness, the bonding layer being positioned between the sensor layer and the logic layer
Implementation Method 2
An insulation region is configured between the SPAD pixels and the peripheral region to provide electrical insulation
Implementation Method 3
When a photon of sufficient energy strikes the diode, it creates an electron-hole pair. This mechanism is also known as the inner photoelectric effect
Implementation Method 4
The avalanche photodiodes are photodiodes with a structure optimized for operating with high reverse bias, approaching the reverse breakdown voltage. This allows each photo-generated carrier to be multiplied by avalanche breakdown, resulting in internal gain within the photodiode
Data Source
AI summary
The present invention relates generally to sensing devices. A stacked SPAD sensor device includes a sensor layer and a logic layer. The sensor layer includes a plurality of SPAD pixels and a peripheral region surrounding the SPAD pixels. An insulation region is configured between the SPAD pixels and the peripheral region to provide electrical insulation. The logic layer includes logic circuits coupled to SPAD pixels. The logic circuits are electrically insulated from the SPAD pixels by the insulation region. There are other embodiments as well.