Fly-over Conductor Transistor for High Voltage Memory
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Solution Overview
Problem
High voltage transistors in high density memory devices experience unwanted charge trapping in insulating materials near the gate and source/drain terminals, leading to increased resistance and voltage drops, which interfere with device operation.
Innovation Solution
Incorporating fly-over conductors over the source/drain terminals, connected to a bias voltage circuit that offsets the effects of unwanted trapped charge, thereby reducing the electric field and maintaining transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high voltage is applied to the transistor for memory operations, then the transistor can perform read/program/erase operations, but unwanted charge trapping occurs in the insulating materials causing increased resistance and voltage drops
Solution Approach 1:
A fly-over conductor is introduced as an intermediary element positioned over the source/drain terminal. This conductor acts as a mediator that allows high voltage to be applied to the transistor while simultaneously providing a path to offset trapped charge effects, thus enabling high voltage operation without the reliability degradation that would otherwise occur
Solution Approach 2:
The fly-over conductor is configured to apply a preliminary counteracting electric field that opposes the harmful effects of trapped charge before they can significantly degrade transistor performance. By positioning the conductor to overlie the source/drain terminal region, the system proactively neutralizes trapped charge effects rather than reactively correcting them after damage occurs
2Ease of operation
If pass transistors are used to transfer voltages from global word lines to local word lines, then voltage transfer is enabled, but charge trapping in insulating materials causes increased resistance and substantial voltage drops
Solution Approach 1:
The fly-over conductor serves as an intermediary that facilitates voltage transfer while compensating for trapped charge effects. By positioning the conductor over the source/drain terminal, it provides a protective influence that maintains voltage transfer accuracy despite the presence of trapped charge in the insulating materials
3Reliability
If fly-over conductors are added to offset trapped charge effects, then transistor performance is maintained, but device complexity increases
Solution Approach 1:
The fly-over conductor is designed to perform multiple functions: it serves as part of the normal transistor structure, provides trapped charge compensation, and maintains voltage transfer capability. By making the conductor multi-functional, the design achieves improved reliability without proportionally increasing device complexity, as the same structural element serves multiple purposes
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 fly-over conductor bias voltage effectively neutralizes the electric field caused by trapped charge, enhancing the driving ability of transistors and maintaining voltage transfer efficiency in high voltage environments.
Implementation Method 1
A circuit applies a bias voltage to the fly-over conductor which can offset the effects of unwanted trapped charge
Data Source
AI summary
A transistor is described including a fly-over conductor. The transistor has a gate, a channel and a source/drain terminal. The fly-over conductor is disposed over the source/drain terminal. A circuit is connected to the fly-over conductor to apply a bias voltage tending to offset effects on the transistor of charge trapped in insulating material. A word line driver can include a transistor with a fly-over conductor.