Solid-State Image Sensor Stacked Substrate Grounding
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Solution Overview
Problem
In solid-state image sensors, a sufficient space for arranging pixel transistors cannot be secured, leading to unstable operation of pixel transistors due to unfixed potential of the substrate.
Innovation Solution
A solid-state image sensor configuration where a first semiconductor substrate with a photoelectric conversion element is stacked with a second semiconductor substrate having an amplification transistor, with an insulating film in between, and the second substrate is grounded via a region with lower resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If pixel transistors and photoelectric conversion elements are integrated on the same substrate, then device complexity is reduced, but sufficient space for arranging pixel transistors cannot be secured
Solution Approach 1:
The device is divided into two separate substrates: a first substrate for photoelectric conversion elements and a second substrate for pixel transistors. This segmentation allows each substrate to be optimized for its specific function, providing sufficient space for pixel transistors on the second substrate while maintaining overall integration through the stacked configuration.
Solution Approach 2:
The design transitions from a planar integration approach to a three-dimensional stacked architecture. By arranging substrates in the vertical dimension, the patent achieves both sufficient space for pixel transistors on the second substrate and close proximity to photoelectric conversion elements on the first substrate, effectively resolving the space constraint.
2Area of stationary object
If substrates are separated to secure space for pixel transistors, then space for arranging transistors is improved, but potential of the substrate with pixel transistors becomes unfixed and operation becomes unstable
Solution Approach 1:
A conductive via is introduced as an intermediary element to electrically connect the second substrate (with pixel transistors) to the ground potential. This via acts as a mediator that provides a stable reference potential for the pixel transistors while allowing the substrate to be physically separated and optimized for transistor arrangement.
Solution Approach 2:
The conductive via establishes an equipotential connection between the second substrate and ground, ensuring that the pixel transistors operate with a stable, fixed potential. This equipotentialization resolves the instability issue while maintaining the spatial separation benefits.
3Area of stationary object
If photoelectric conversion elements and pixel transistors are on separate substrates, then space for arranging transistors is sufficient, but the operation of pixel transistors becomes unstable due to unfixed potential
Solution Approach 1:
The conductive via serves as an intermediary that provides a stable electrical reference for the pixel transistors on the second substrate. This intermediary connection to ground ensures stable operation while the physical separation maintains sufficient space for transistor arrangement.
Solution Approach 2:
By establishing an equipotential connection to ground through the conductive via, the pixel transistors operate with a stable reference potential, improving ease of operation while the substrate separation provides the necessary space for efficient transistor layout.
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 fixes the potentials of stacked substrates, stabilizing the operation of pixel transistors and allowing for sufficient space arrangement, thereby improving the noise level of random telegraph signal noise.
Implementation Method 1
a second semiconductor substrate facing the first semiconductor substrate with an insulating film interposed therebetween
Implementation Method 2
has a region having a resistance lower than a resistance of the second semiconductor substrate on a second main surface opposite to the first main surface, and is grounded via the region
Implementation Method 3
the second semiconductor substrate has an amplification transistor that amplifies an electrical signal output from the photoelectric conversion element
Data Source
AI summary
A solid-state image sensor according to the present disclosure includes a first semiconductor substrate having a photoelectric conversion element and a second semiconductor substrate facing the first semiconductor substrate with an insulating film interposed therebetween, in which the second semiconductor substrate has an amplification transistor that amplifies an electrical signal output from the photoelectric conversion element on a first main surface (MSa), has a region having a resistance lower than a resistance of the second semiconductor substrate on a second main surface (MSb) opposite to the first main surface (MSa), and is grounded via the region.