Solid-State Imaging Device Vertical Well Potential Stabilization
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Solution Overview
Problem
Conventional solid-state imaging devices face issues with noise and reduced sensitivity due to the limited area for transistor gates and photoelectric converters, caused by the need to stabilize the well region's electric potential, which restricts the formation of these components and leads to variations in charge accumulation and image shading.
Innovation Solution
A solid-state imaging device with a semiconductor substrate of a first conductivity type, a dark-current drain region of a second conductivity type, and a connection region that maintains the well region at a fixed electric potential, allowing for stable potential without limiting the areas for photoelectric converters and transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If doped regions and light-shielding films are electrically connected via well contact regions to stabilize the well region's electric potential, then the electric potential uniformity is improved, but the area available for transistor gates and photoelectric converters is reduced
Solution Approach 1:
The invention transitions from a two-dimensional planar connection method (well contact regions in the same layer) to a three-dimensional vertical connection method (connection regions extending from the surface through insulating films to reach the well region). This dimensional change allows electrical connection without occupying lateral space, thereby resolving the contradiction between potential stabilization and area availability.
Solution Approach 2:
The invention introduces connection regions as intermediary structures that extend vertically through insulating films to establish electrical connection between the well region and external circuits. These connection regions act as mediators that provide the necessary electrical path without requiring lateral well contact regions, thus preserving the area for photoelectric converters and transistor gates while maintaining potential uniformity.
2Stability of the object's composition
If the area of photoelectric converters is reduced due to doped region placement, then the well region potential control is improved, but the light reception amount and sensitivity decrease
Solution Approach 1:
By moving the connection structure from the lateral plane to the vertical dimension, the invention eliminates the need for doped regions to occupy lateral space within the well region. This allows photoelectric converters to utilize the maximum available lateral area for light reception, thereby resolving the contradiction between potential control and light reception quantity.
3Stability of the object's composition
If transistor gate area is reduced due to well contact region constraints, then the well potential stabilization is achieved, but noise increases and reading speed decreases
Solution Approach 1:
The vertical extension of connection regions through insulating films eliminates lateral constraints on transistor gate dimensions. This allows transistor gates to achieve optimal area for low noise performance and high reading speed while the well potential remains stabilized through the vertical connection path, resolving the contradiction between potential stabilization and signal quality.
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 stabilizes the well region's electric potential, preventing noise and image shading while allowing for sufficient area for both photoelectric converters and transistors, enhancing sensitivity and charge accumulation uniformity across pixels.
Implementation Method 1
the well region is maintained at a fixed electric potential by being connected to the semiconductor substrate via the connection region
Implementation Method 2
N-type (second conductivity type) photodiodes 912, which are photoelectric converters formed within the well region 910
Data Source
AI summary
A solid-state imaging device including: a semiconductor substrate of a first conductivity type, having a fixed electric potential; a dark-current drain region of a second conductivity type, formed on a portion of the semiconductor substrate; a connection region of the first conductivity type, formed on another portion of the semiconductor substrate where the dark-current drain region is not formed; a well region of the first conductivity type, covering the dark-current drain region and the connection region; and a first region and a second region, formed within the well region and constituting a part of a read transistor that reads signal charge generated by photoelectric conversion. The well region is maintained at a fixed electric potential by being connected to the semiconductor substrate via the connection region.