Word Driver Line Control for Row Hammer Mitigation
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Solution Overview
Problem
The repeated access to a particular subword line in semiconductor memory devices, known as a 'row hammer' event, leads to increased data degradation in nearby subword lines due to the generation of free electrons in the back-gate region when the channel of a transistor disappears, causing rapid discharge and voltage fluctuations.
Innovation Solution
The discharge of subword lines is controlled by driving the word driver line in a gradual manner, such as step-wise, with intermediate potentials between active and inactive states, to reduce the rate of channel dissipation and mitigate row hammer effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If subword lines are driven to high potential rapidly, then access speed is improved, but row hammer effects are exacerbated causing data degradation
Solution Approach 1:
The patent applies preliminary action by pre-charging the word driver line to an intermediate potential level before fully activating the subword line. This preparatory step reduces the voltage differential that causes rapid channel dissipation and free electron generation, thereby mitigating row hammer effects while maintaining acceptable access speed
Solution Approach 2:
The patent implements periodic action by using multi-stage voltage transitions with intermediate holding periods. The word driver line is activated in steps with pause periods at intermediate potentials, allowing controlled discharge that prevents the sudden voltage fluctuations responsible for row hammer damage while still achieving timely subword line activation
2Speed
If subword lines are discharged rapidly to low potential, then operation speed is improved, but voltage fluctuations increase causing nearby subword lines to degrade
Solution Approach 1:
The patent applies preliminary action by pre-discharging the word driver line to an intermediate potential level before fully deactivating the subword line. This preparatory step reduces the voltage differential that causes rapid channel dissipation and free electron generation, thereby mitigating row hammer effects while maintaining acceptable access speed
Solution Approach 2:
The patent implements periodic action by using multi-stage voltage transitions with intermediate holding periods. The word driver line is deactivated in steps with pause periods at intermediate potentials, allowing controlled discharge that prevents the sudden voltage fluctuations responsible for row hammer damage while still achieving timely subword line deactivation
Data Source
AI summary
Apparatuses and methods for driving word driver lines in a gradual manner are disclosed herein. Word driver lines may be driven to intermediate potentials between high and low potentials. In some examples, the word driver lines may be driven in a step-wise manner. In some examples, the intermediate potential may be a bias voltage. The bias voltage may be provided by a bias voltage generator. One or more enable signals may be used to control the driving of the word driver line. In some examples, an address signal may be used to control the driving of the word driver line. Driving the word driver line in a gradual manner may cause a word line to discharge in a gradual manner in some examples.