Subword Driver Circuit Dynamic Potential Switching
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Solution Overview
Problem
In DRAM semiconductor devices, the negative potential applied to subword lines to reduce off-leak current and prevent information retention deterioration leads to increased GIDL current, making it challenging to balance disturbance characteristics and current specifications due to manufacturing processing deviations.
Innovation Solution
A semiconductor device with subword driver circuits that supply multiple non-selection and selection potentials, allowing the non-active potential of subword lines to be dynamically adjusted based on accessing states, thereby reducing GIDL current and improving disturbance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the negative potential applied to subword lines is lowered to reduce off-leak current and prevent information retention deterioration, then the disturbance characteristic is improved, but the GIDL current increases
Solution Approach 1:
The subword driver circuit dynamically switches between multiple negative potentials (first negative potential and second negative potential) based on the accessing state of memory cells. When memory cells are accessed, the first negative potential is applied; when not accessed, the second negative potential (lower than first) is applied. This dynamic adjustment resolves the contradiction by adapting the potential level to operational requirements, reducing GIDL current during non-access periods while maintaining disturbance protection during access periods.
Solution Approach 2:
The invention changes the parameter of subword line potential from a fixed negative value to a variable negative value with at least two distinct levels. The subword driver circuit selects between first and second negative potentials based on accessing state, thereby changing the electrical parameter adaptively. This parameter change enables optimization of both disturbance characteristic and GIDL current by matching potential level to operational context.
2Reliability
If a fixed negative potential is applied to subword lines, then the disturbance characteristic can be maintained, but the GIDL current increases and manufacturing tolerance becomes problematic
Solution Approach 1:
Instead of relying on precise manufacturing of a single fixed potential value, the invention uses a dynamic system that switches between two negative potentials generated by separate circuits. This approach makes the system less sensitive to manufacturing variations because each potential can be independently optimized and adjusted, reducing the impact of processing deviations on overall performance.
Solution Approach 2:
The subword driver circuit is segmented into multiple potential generation paths (first negative potential circuit and second negative potential circuit), each capable of independent optimization. This segmentation allows manufacturing variations to be managed separately for each potential generation path, improving ease of manufacture while maintaining reliable disturbance protection through the switching mechanism.
Data Source
AI summary
The present invention is provided with; subword drivers SWD for driving subword lines SWL, a selection circuit for supplying either negative potential VKK1 or VKK2 to the subword drivers SWD, and memory cells MC that are selected in the case when the subword line SWL is set to an active potential VPP and are not selected in the case when the subword line SWL is either a negative potential VKK1 or VKK2.