Solid-State Imaging Device Floating Diffusion Voltage Control
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Solution Overview
Problem
Miniaturization of solid-state imaging devices leads to decreased breakdown voltage and power supply voltage, resulting in lower FD capacitance, making it difficult to detect high intensity luminance and causing residual image electrons, with existing solutions limited by parasitic capacitance coupling effects.
Innovation Solution
A solid-state imaging device with a voltage control circuit that increases the column signal line voltage before charge transfer, using a voltage control transistor to enhance FD capacitance and dynamic range, and incorporating multiple photodiodes to increase saturated electrons, while minimizing the effect of load transistors and optimizing timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the solid-state imaging device is miniaturized, then the device size is reduced, but the breakdown voltage and power supply voltage decrease, resulting in lower FD capacitance
Solution Approach 1:
The voltage control circuit pre-charges the column signal line to a high voltage level (e.g., 0.7V to 1.0V above VDD) before the floating diffusion reset operation. This preliminary voltage elevation creates a stronger electric field that compensates for the reduced FD capacitance in miniaturized devices, enabling sufficient charge transfer capacity despite the smaller device size.
Solution Approach 2:
The invention changes the voltage parameter of the column signal line from the conventional VDD level to a elevated level (VDD + 0.7V to VDD + 1.0V). This parameter change increases the voltage difference across the floating diffusion during charge transfer, thereby compensating for the reduced capacitance effect in miniaturized devices and maintaining adequate charge transfer capability.
2Volume of moving object
If the FD capacitance is reduced due to miniaturization, then the device can be made smaller, but it becomes difficult to detect high intensity luminance and residual image electrons occur
Solution Approach 1:
The voltage control circuit performs preliminary charging of the column signal line before the photodiode charge transfer. This pre-established high voltage condition ensures that even with reduced FD capacitance in miniaturized devices, the electric field strength is sufficient to collect all photoelectrons including those from high intensity luminance, preventing residual image electrons and maintaining detection reliability.
Solution Approach 2:
The invention applies a preliminary counter-action by elevating the column signal line voltage before charge transfer occurs. This pre-compenstation for the reduced capacitance effect prevents the harmful consequence of insufficient charge collection, thereby eliminating residual image electrons and ensuring accurate detection of high intensity luminance despite miniaturization.
3Volume of moving object
If the power supply voltage is lowered, then the device can be miniaturized, but the dynamic range is reduced and saturated electrons are insufficient
Solution Approach 1:
The invention changes the operating voltage parameter of the column signal line from VDD to an elevated level (VDD + 0.7V to VDD + 1.0V). This parameter modification increases the voltage swing and electric field strength during charge transfer, enabling the floating diffusion to accumulate sufficient saturated electrons even when the power supply voltage is reduced for miniaturization purposes, thereby maintaining adequate dynamic range.
Solution Approach 2:
The voltage control circuit performs preliminary voltage elevation of the column signal line before charge transfer. This pre-established high voltage condition compensates for the reduced power supply voltage, ensuring that the floating diffusion can achieve sufficient saturation electron capacity despite the lower operating voltage required for miniaturized device operation.
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
Enables detection of higher intensity luminance with a wide dynamic range and reduced residual images by increasing FD capacitance and saturated electrons, overcoming limitations of miniaturization and power supply voltage constraints.
Implementation Method 1
a photodiode which photoelectrically converts incident light
Implementation Method 2
a voltage control circuit which increases a voltage of the column signal line to a predetermined voltage between the reset of the potential by the reset transistor and the transfer of the charge by the transferring transistor
Data Source
AI summary
A solid-state imaging device includes plural pixel cells, arranged in a matrix, each of which includes a photodiode that photoelectrically converts incident light. The solid-state imaging devices also includes a transferring transistor that transfers a charge generated by the photodiode, a floating diffusion that accumulates the transferred charge, a reset transistor that resets a potential of said floating diffusion, and an amplifying transistor that converts the charge accumulated in the floating diffusion into a voltage. The solid-state imaging device further includes column signal lines, each connected to associated ones of plurality of amplifying transistors, including the amplifying transistor corresponding to a corresponding one of columns having the associated plurality of pixel cells, and a voltage control circuit which increases a voltage of the column signal line to a predetermined voltage between the reset of the potential by the reset transistor and the transfer of the charge by the transferring transistor.