Stacked Solid-State Image Sensor Back-Gate Noise Control
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Solution Overview
Problem
Existing solid-state image sensors face challenges in effectively reducing noise and display unevenness in captured images, despite efforts to suppress leakage current by controlling the back gate of sampling and analog memory reset transistors.
Innovation Solution
A solid-state image sensor design featuring a stacked substrate structure with a photoelectric conversion unit, a transfer gate unit, a floating diffusion unit, and insulating films, along with a transistor on a second substrate connected via an insulating film, including a back gate, which allows for adjustment of noise levels by varying the back gate voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the back gate of sampling transistor and analog memory reset transistor is suppressed to reduce leakage current, then noise control is improved, but display unevenness in captured image cannot be sufficiently reduced
Solution Approach 1:
The transistor is divided into two separate gates: a front gate for primary control and a back gate for noise suppression. This segmentation allows independent optimization of each gate's function, enabling the back gate to specifically address noise and display uniformity issues without interfering with the front gate's switching operations.
Solution Approach 2:
The back gate is applied locally to the transistor structure to provide targeted noise suppression at the transistor-substrate interface. This localized approach allows precise control of leakage current and noise in critical regions while maintaining overall device performance and display uniformity.
2Object-generated harmful factors
If conventional noise suppression methods are used, then leakage current is reduced, but noise sensitivity in correlated double sampling remains insufficient
Solution Approach 1:
The back gate is configured to preemptively suppress noise and leakage current before they can affect the sampling process. By applying noise suppression in advance through the back gate, the signal quality is improved prior to correlated double sampling, thereby enhancing noise sensitivity without requiring additional processing.
3Device complexity
If the transistor structure is simplified, then device complexity is reduced, but noise control capability is insufficient
Solution Approach 1:
Instead of increasing the complexity of the front gate structure, the solution adds a back gate dimension to the transistor. This dimensional addition provides enhanced noise control capability while maintaining the simplicity of the original front gate structure, allowing independent optimization of noise suppression without complicating the primary switching function.
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 enhances noise control and reduces display unevenness by improving noise sensitivity in correlated double sampling, effectively eliminating noise and preventing step-like gradation jumps in image gradation.
Implementation Method 1
a photoelectric conversion unit
Data Source
AI summary
It is an object of the present technology to provide a solid-state image sensor capable of reducing display unevenness of a captured image. A solid-state image sensor includes a first substrate that includes a photoelectric conversion unit, a transfer gate unit that is connected to the photoelectric conversion unit, an FD unit that is connected to the transfer gate unit, and an interlayer insulating film that covers the photoelectric conversion unit, the transfer gate unit, and the FD unit. The solid-state image sensor further includes a second substrate that includes an amplifier transistor and is disposed to be adjacent to the interlayer insulating film, the amplifier transistor constituting a part of a pixel transistor connected to the FO unit via the interlayer insulating film and including a back gate unit.