Subword Line Discharge 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 free electrons generated in the back-gate region, causing channel dissipation and voltage fluctuations.
Innovation Solution
The discharge of subword lines is controlled by driving the main word line to a first low potential and subsequently to a second low potential, which can be a negative voltage, and by resetting word driver line signals to manage the voltage and rate of discharge, thereby mitigating the effects of row hammer events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If repeated access to a particular subword line is performed, then data access speed is improved, but data degradation in nearby subword lines increases due to row hammer events
Solution Approach 1:
The patent applies preliminary anti-action by preemptively discharging accumulated charge from subword lines before row hammer events can cause harmful effects. The control circuit monitors and detects when charge accumulation reaches critical levels, then actively discharges the subword lines to prevent data degradation, counteracting the harmful effects before they occur
Solution Approach 2:
The patent implements feedback mechanisms where control circuits continuously monitor the state of subword lines and adjacent lines, detecting charge accumulation patterns that indicate impending row hammer effects. Based on this feedback information, the system dynamically activates discharge operations to maintain data integrity while allowing normal high-speed access to continue
2Productivity
If subword lines are driven to high potential frequently, then data access performance is improved, but channel dissipation and voltage fluctuations increase
Solution Approach 1:
The patent applies periodic action by implementing regular discharge cycles for subword lines. Between normal read/write operations, the control circuit periodically activates discharge paths to remove accumulated charge from subword lines and their diffusion regions, maintaining voltage stability without interfering with data access performance
Solution Approach 2:
The patent introduces intermediary discharge circuits and control logic that act as mediators between the subword lines and the rest of the memory system. These intermediary components provide controlled charge dissipation paths, allowing excess charge to be removed gradually through dedicated discharge transistors and resistors, preventing sudden voltage fluctuations while maintaining operational performance
Data Source
AI summary
Apparatuses and methods for controlling the discharge of subword lines are described. The rate of discharge and/or the voltage level discharged to may be controlled. In some embodiments, a main word line may be driven to multiple low potentials to control a discharge of a subword line. In some embodiments, a first word driver line signal and/or a second word driver line signal may be reset to control a discharge of a subword line. In some embodiments, a combination of driving the main word line and the first word driver line signal and/or the second word driver line signal resetting may be used to control a discharge of the subword line.