Stacked Photoelectric Conversion Pixels With Split Gate Dielectrics
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Solution Overview
Problem
Current photoelectric conversion apparatuses face challenges in achieving high pixel density while optimizing the relative permittivity of gate insulator films and reducing power consumption, particularly in the saturation charge of photoelectric conversion units.
Innovation Solution
The apparatus employs a stacked structure with different relative permittivity gate insulator films between transfer and amplifier transistors, where the gate insulator films are differentiated in nitrogen concentration or density to enhance drive force and reduce noise, and the transfer gates are designed to maintain a strong electric field while preventing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gate insulator film thickness is reduced to increase pixel density, then the drive force of transistors is improved, but leakage current increases and noise is generated
Solution Approach 1:
The patent applies different gate insulator film configurations to different transistor types: the transfer transistor uses a thicker gate insulator film (first thickness) to prevent leakage current, while the amplifier transistor uses a thinner gate insulator film (second thickness) to enhance drive force. This local differentiation resolves the contradiction by optimizing each transistor's gate insulator thickness according to its specific functional requirements rather than using a uniform thickness across all transistors.
Solution Approach 2:
The patent changes the gate insulator film thickness parameter between different transistor types. By setting the gate insulator film thickness of the transfer transistor to be greater than that of the amplifier transistor, the patent achieves both high drive force (through the thinner film in amplifier) and low leakage current (through the thicker film in transfer transistor), thereby resolving the technical contradiction.
2Power
If the relative permittivity of the gate insulator film is increased to enhance transistor drive force, then the transistor performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies high relative permittivity gate insulator films selectively to specific transistor regions where enhanced drive force is needed (amplifier transistor), while using standard gate insulator films in other regions (transfer transistor). This localized application of high-k materials achieves the desired performance improvement without requiring the entire device to be manufactured with complex high-k material processes.
Solution Approach 2:
The patent employs composite gate insulator structures combining different materials with different relative permittivities. By using a combination of high-k and standard-k gate insulator films in different locations, the patent achieves enhanced transistor drive force where needed while maintaining manufacturing feasibility through the use of conventional materials in other regions.
3Use of energy by stationary object
If the gate insulator film is made thinner to reduce power consumption, then power efficiency is improved, but saturation charge of photoelectric conversion units decreases
Solution Approach 1:
The patent differentiates gate insulator film thickness between transfer and amplifier transistors: the amplifier transistor uses a thinner gate insulator film to reduce power consumption during signal amplification, while the transfer transistor uses a thicker gate insulator film to maintain proper charge transfer capability and preserve saturation charge levels in photoelectric conversion units. This local differentiation resolves the contradiction by applying thin films only where power reduction is beneficial.
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 improves the drive force of amplifier transistors, reduces noise, and maintains high saturation charge levels, thereby enhancing the overall performance and efficiency of the photoelectric conversion apparatus.
Implementation Method 1
a photoelectric conversion element configured to receive light from the first surface
Implementation Method 2
The first gate insulator film and the second gate insulator film are different in relative permittivity
Data Source
AI summary
A photoelectric conversion apparatus includes a first component including a first semiconductor substrate having a first surface and a second surface opposite the first surface, a photoelectric conversion element configured to receive light from the first surface, a first semiconductor region, a transfer gate disposed on the second surface and configured to transfer a charge from the photoelectric conversion element to the first semiconductor region, and a first gate insulator film disposed between the second surface and the transfer gate, and a second component stacked on the first component and including a second semiconductor substrate having a third surface and a fourth surface opposite the third surface, an amplifier transistor including a gate connected to the first semiconductor region, and a second gate insulator film between the gate and the third surface. The first gate insulator film and the second gate insulator film are different in relative permittivity.