Pixel Drive Circuit Layout Using Isolation Capacitance Against Burn-In
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Solution Overview
Problem
As pixel pitch becomes finer, the capacitance between transistors facing each other across the element isolation region increases, emphasizing a burn-in phenomenon in display images due to changes in the voltage-current characteristic of the light-emitting unit.
Innovation Solution
The drive transistor and write transistor are separated by an element isolation region, with the capacitance generated between them functioning as part of the capacitance unit, utilizing a shallow trench isolation structure to minimize capacitive coupling effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pixel pitch is reduced to achieve finer display resolution, then the display resolution is improved, but the capacitance between transistors increases causing burn-in phenomenon
Solution Approach 1:
The harmful capacitance effect is extracted and utilized by designating the capacitance between drive transistor and write transistor as a functional capacitance unit (Cst). This extracted capacitance is then used beneficially to maintain gate voltage during the light emission period, preventing burn-in rather than being treated as a parasitic effect to be eliminated.
Solution Approach 2:
The capacitance that naturally forms between adjacent transistors due to fine pixel pitch is converted from a harmful parasitic effect into a beneficial functional component. By intentionally designing the drive circuit to utilize this capacitance as the holding capacitance Cst, the patent transforms the burn-in causing factor into the mechanism that maintains stable gate voltage and prevents luminance degradation over time.
2Area of stationary object
If transistors are placed closer together to reduce pixel pitch, then the display density is improved, but the capacitance between transistors increases
Solution Approach 1:
The capacitance generated by close transistor placement is converted from a harmful parasitic effect into a beneficial functional component. The drive circuit is designed so that the capacitance between drive transistor and write transistor serves as the holding capacitance Cst, which maintains gate voltage during light emission and prevents burn-in phenomenon.
Solution Approach 2:
The capacitance between drive transistor and write transistor serves multiple functions: it acts as the holding capacitance Cst for maintaining gate voltage during light emission, and simultaneously provides the charge storage function needed for the write transistor to maintain signal voltage. This multi-functionality eliminates the need for separate capacitance components.
3Manufacturing precision
If a shallow trench isolation structure is used to separate transistors, then the element isolation is improved, but the manufacturing complexity increases
Solution Approach 1:
The element isolation structure and the capacitance formation are merged into a single process. The insulating film that forms the shallow trench isolation also serves as the dielectric layer for the capacitance unit, eliminating the need for separate capacitance formation steps and reducing overall manufacturing complexity.
Solution Approach 2:
The insulating film in the element isolation region serves dual purposes: providing electrical isolation between adjacent transistors and forming the dielectric layer for the capacitance unit. This multi-functionality reduces the number of manufacturing steps while achieving both isolation and capacitance formation.
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 reduces the emphasis of burn-in phenomena by minimizing the impact of capacitance changes on the voltage-current characteristics of the light-emitting unit, maintaining image quality over time.
Implementation Method 1
a capacitance generated in a portion where the drive transistor and the write transistor face each other through the element isolation region functions as at least a part of the capacitance unit
Data Source
AI summary
A display element includes a light-emitting unit of a current drive type, and a drive unit that drives the light-emitting unit, in which the drive unit includes a capacitance unit, a drive transistor that causes a current corresponding to a voltage held by the capacitance unit to flow through the light-emitting unit, and a write transistor that writes a signal voltage to the capacitance unit, the drive transistor and the write transistor are formed in a state of being separated by an element isolation region, on a semiconductor substrate, and a capacitance generated in a portion where the drive transistor and the write transistor face each other through the element isolation region functions as at least a part of the capacitance unit.