Shield Conductive Lines for Bitline Capacitive Coupling Compensation
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Solution Overview
Problem
In nonvolatile memory technology, the reduced distance between bitlines leads to capacitive coupling, causing parasitic electrical potentials that result in involuntary programming of memory cells, and grounding bitlines to prevent this increases leakage currents, which can collapse the voltage source.
Innovation Solution
The introduction of shield conductive lines capacitively coupled to bitlines, which are set to a compensation voltage when the bitlines are floating, reduces the parasitic potential by altering the capacitive coupling equation and minimizing the risk of involuntary programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the distance between bitlines is reduced to increase memory density, then productivity is improved, but capacitive coupling increases causing parasitic potential that leads to involuntary programming
Solution Approach 1:
A shield conductive line is introduced as an intermediary element between adjacent bitlines. This shield line is capacitively coupled to the bitline and receives a compensation voltage that is opposite in polarity to the parasitic potential, thereby canceling out the harmful capacitive coupling effect and preventing involuntary programming of memory cells.
Solution Approach 2:
The compensation voltage is applied to the shield conductive line in advance to counteract the parasitic potential before it can cause harmful effects. By applying a voltage with opposite polarity to the expected parasitic potential, the system preemptively neutralizes the harmful capacitive coupling that would otherwise lead to involuntary programming.
2Reliability
If floating bitlines are grounded to prevent parasitic potential, then reliability is improved, but leakage currents increase which can collapse the voltage source
Solution Approach 1:
The shield conductive line acts as an intermediary that provides a controlled path for managing parasitic potential without requiring direct grounding of the bitline. By coupling the shield line to the bitline through capacitance and applying compensation voltage to the shield line, the system eliminates parasitic potential while maintaining the bitline in a high-impedance floating state, thus avoiding large leakage currents.
3Reliability
If shield conductive lines are introduced to reduce parasitic potential, then reliability is improved, but device complexity increases
Solution Approach 1:
The shield conductive line serves multiple functions: it acts as a shielding element to reduce capacitive coupling, provides a pathway for compensation voltage to cancel parasitic potential, and can be integrated into existing memory cell structures without requiring fundamental redesign. This multi-functionality justifies the added complexity by delivering multiple benefits from a single structural addition.
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 solution effectively reduces the parasitic potential on floating bitlines, minimizing the risk of involuntary programming and maintaining low leakage currents, thereby preventing voltage source collapse.
Implementation Method 1
a shield conductive line extending above the bitline, capacitively coupled to the bitline
Data Source
AI summary
A method of programming memory cells in a nonvolatile memory, includes applying a programming voltage to a first bitline and setting a second bitline in a floating state. The method further includes applying a compensation voltage to a shield conductive line coupled to the bitline set in the floating state, and setting in the floating state a shield conductive line coupled to the bitline receiving the programming voltage. The method is applicable to the reduction of the parasitic programming phenomena of memory cells by capacitive coupling between bitlines.