Solid-State Imaging Pixel Charge Injection for Global Shutter Linearity
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Solution Overview
Problem
In MOS-type solid-state imaging apparatuses, the linearity of signals is degraded when operating in global shutter mode due to the electric potential of the contact unit being higher than the barrier unit, causing electrons to bypass the barrier and not accumulate in the charge accumulation unit.
Innovation Solution
A solid-state imaging apparatus with a pixel unit comprising a photoelectric conversion film, an injection unit, an accumulation unit, and a barrier unit, where the charge is selectively injected into the injection unit, allowing electrons to pass through the barrier and accumulate in the semiconductor substrate, improving signal linearity by controlling the charge injection process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the contact unit is separated from the charge accumulation unit to reduce dark currents, then dark current reduction is achieved, but the electric potential control becomes complex
Solution Approach 1:
The barrier unit is introduced as an intermediary component between the contact unit and the charge accumulation unit. This barrier unit controls the electric potential distribution, allowing electrons to be injected from the contact unit while preventing direct connection that would cause dark current. The barrier unit mediates the electric potential difference, enabling charge accumulation without direct contact between the contact unit and accumulation unit.
2Reliability
If a discharge transistor is added to synchronize images in global shutter mode, then image synchronicity is improved, but signal linearity is degraded due to electric potential imbalance
Solution Approach 1:
The electric potential of the contact unit is made dynamically controllable through the discharge transistor, allowing it to switch between different potential states. During the accumulation period, the contact unit potential is adjusted to match the barrier unit potential, enabling linear electron injection. The discharge transistor dynamically adjusts the potential to maintain linearity while achieving global shutter functionality.
3Quantity of substance
If the electric potential of the contact unit is increased to enable charge injection, then charge accumulation is improved, but electrons bypass the barrier unit causing non-linear signals
Solution Approach 1:
The electric potential parameter of the contact unit is dynamically changed based on the operational phase. During accumulation, the contact unit potential is set equal to the barrier unit potential to enable controlled electron injection. This parameter change ensures that electrons are injected in proportion to the light intensity, maintaining signal linearity while achieving sufficient charge accumulation.
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 enhances signal linearity in global shutter mode by ensuring electrons accumulate correctly in the charge accumulation unit, thereby improving image quality and synchronicity during exposure periods.
Implementation Method 1
a photoelectric conversion film 9... electrons generated by photoelectric conversion at the photoelectric conversion film 9
Data Source
AI summary
An imaging device includes a photoelectric conversion unit, a contact region, and an accumulation region. The contact region is configured to receive a charge from the photoelectric conversion unit. The accumulation region is configured to store the charge from the contact region. The imaging device is configured to selectively inject a charge into the contact region.