Solid-State Imaging Element Impurity Modulation for Charge Transfer
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Solution Overview
Problem
The manufacturing process of solid-state imaging elements is complex and requires high accuracy to control the potential in accumulation regions, leading to inaccurate electron movement and residual images due to the need for sequential impurity implantation and precise positioning.
Innovation Solution
A solid-state imaging element with an impurity concentration modulation region having a locally high or low concentration of impurities, where the area or density of these regions increases with decreasing distance to the transfer section, allowing for a smooth incline of potential to accelerate electron movement without the need for precise multi-step implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the accumulation region increases in size to make the solid-state imaging element highly sensitive, then the sensitivity is improved, but the transfer speed of electric charges through the transfer section decreases
Solution Approach 1:
The patent applies local quality by creating an impurity concentration modulation region with a specific spatial distribution of impurities within the accumulation region. The impurity concentration is intentionally varied locally to generate a potential gradient that accelerates electron transfer toward the transfer section, while maintaining the overall large size of the accumulation region for high sensitivity.
Solution Approach 2:
The patent changes the impurity concentration parameter within the accumulation region to create a potential gradient. By modulating the impurity concentration spatially (higher concentration near the transfer section, lower concentration farther away), the patent optimizes both the storage capacity and transfer speed of electrons, resolving the contradiction between sensitivity and transfer speed.
2Manufacturing precision
If sequential impurity implantation is used to control potential in accumulation regions, then the potential distribution can be adjusted, but the manufacturing process complexity increases and positioning accuracy requirements increase
Solution Approach 1:
The patent segments the accumulation region into different zones with varying impurity concentrations. Instead of requiring multiple sequential implantation steps, the design uses a single implantation step that creates a spatially modulated impurity distribution, simplifying the manufacturing process while achieving precise potential control.
Solution Approach 2:
The patent performs preliminary action by designing the impurity concentration modulation region structure before manufacturing. The spatial distribution pattern is predetermined, allowing a single implantation step to achieve the desired potential gradient without requiring complex multi-step processes or high-precision positioning during manufacturing.
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 simplifies the manufacturing process and allows for precise control of electron movement, preventing residual images by adjusting the impurity concentration modulation regions to optimize electron transfer speed.
Implementation Method 1
an impurity concentration modulation region having a locally high concentration of an impurity having a second conductivity type, or having a locally low concentration of an impurity having a first conductivity type is formed in a part of the accumulation region
Implementation Method 2
a photoelectric conversion unit such as a photodiode in a substrate to generate electric charges by photoelectrically converting light inputted to the substrate
Data Source
AI summary
Provided are a solid-state imaging element which can be simply manufactured and can control movement of electric charges in an accumulation region with a high degree of accuracy, and a method of manufacturing the same. A solid-state imaging element (1a) includes a substrate (11) having a first conductivity type; an accumulation region (12) having a second conductivity type and provided in the substrate (11); a read-out region (13) for receiving the transferred electric charges accumulated in the accumulation region (12); and a transfer section (14) for transferring the electric charges from the accumulation region (12) to the read-out region (13). An impurity concentration modulation region 121 having a locally high concentration of an impurity having the second conductivity type, or having a locally low concentration of an impurity having the first conductivity type is formed in a part of the accumulation region (12). An area of the impurity concentration modulation region (121) per unit distance with respect to the transfer section (14), or a density of the discretely provided impurity concentration modulation region (121) increases with decreasing distance to the transfer section (14).