Discharge Transistors for IR-DROP Suppression in Semiconductor Memory
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Solution Overview
Problem
Conventional semiconductor memory devices experience a voltage rise due to IR-DROP when a ground voltage is applied to a memory cell during a program operation, leading to increased chip area and reduced device reliability.
Innovation Solution
Incorporating discharge transistors between the ground and bit lines connected to the memory cell, with independent discharge control signals to manage the application of ground and positive voltages, thereby suppressing voltage rise and reducing chip area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ground voltage is applied to the source of a memory cell during a program operation through the conventional current path, then the program operation can be performed, but a voltage rise due to IR-DROP occurs in the current path
Solution Approach 1:
A discharge transistor is introduced as an intermediary component between the ground voltage source and the source bit line. This discharge transistor provides a dedicated low-impedance path to ground, acting as a mediator that prevents voltage rise in the main current path while still enabling the program operation to proceed
2Productivity
If the conventional current path is used to apply ground voltage to the memory cell source, then the program operation can proceed, but the chip area increases
Solution Approach 1:
The ground voltage application function is segmented from the main current path. Instead of using the entire conventional path (ground voltage application transistor → column transistors → main bit line → selection transistor sub-bit line), the ground voltage application is segmented into a direct path through the discharge transistor, separating the grounding function from the data transmission function
3Reliability
If discharge transistors are added to suppress voltage rise, then device reliability improves and chip area is reduced, but the device complexity increases
Solution Approach 1:
The discharge transistor is designed to serve multiple functions: it acts as a ground voltage application path during program operations, provides a discharge path for bit line voltage, and helps maintain source voltage stability. By making this single component multi-functional, the need for additional separate components is reduced, thereby limiting the increase in device complexity
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 solution effectively reduces voltage rise due to IR-DROP, enabling low-voltage write operations and minimizing chip area, while maintaining source voltage close to ground, thus improving device reliability.
Implementation Method 1
the ground voltage applied to the source of the memory cell rises from the original ground voltage due to IR-DROP in a current path from the ground to the source of the memory cell MC
Data Source
AI summary
In a semiconductor memory device, a voltage rise due to IR-DROP is suppressed which occurs when a ground voltage is applied to a memory cell during a program operation. Discharge transistors are provided between the ground and bit lines connected to the source and drain of the memory cell. The discharge transistors receive mutually independent discharge control signals which are generated and outputted from a DS decoder driver at the respective gates thereof. To the bit line which applies the ground voltage to the memory cell, the ground voltage can be set using the discharge transistor.