Sensing Module for Non-Volatile Memory State Identification
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Solution Overview
Problem
Conventional read operations for non-volatile memory cells, particularly one-time programmable (OTP) memory cells, face difficulties in accurately identifying the un-programmed/programmed state due to the unpredictable and uncontrollable position of conductive filaments, leading to erroneous cell current detection and incorrect state identification.
Innovation Solution
A sensing module comprising a sensing amplifier and a current sink is used to perform a read operation on memory cells, generating a sensing current and a reference current that is constant when the memory cell is either un-programmed or programmed, allowing for accurate identification of the cell state by differentiating between un-programmed and programmed states based on the sensing current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional read operation is performed on an OTP memory cell, then the read operation can be executed, but the cell current detection becomes erroneous due to unpredictable conductive filament position, leading to incorrect state identification
Solution Approach 1:
The patent introduces an intermediary conductive path through the P-type substrate that provides a controlled current flow path. This intermediary path bypasses the unpredictable conductive filament position issue by creating a dedicated sensing route that is independent of where the filament forms in the gate oxide, thereby resolving the contradiction between reliable state identification and accurate cell current detection
Solution Approach 2:
The patent replaces the direct cell current measurement approach with an alternative sensing mechanism that measures voltage drop across a known resistance in the substrate path. This substitution transforms the measurement from directly detecting the problematic cell current to detecting a related voltage signal that is less sensitive to filament position variations, improving both reliability and measurement precision
2Ease of manufacture
If the conductive filament position is left uncontrollable (conventional approach), then the programming process is simpler, but the cell current varies significantly leading to erroneous sensing results
Solution Approach 1:
The patent segments the current path into distinct components: the programming path through the gate oxide and the sensing path through the P-type substrate. By separating these functions, the filament position variability in the programming path no longer affects the sensing path, allowing simple programming processes to coexist with reliable sensing results
Solution Approach 2:
The P-type substrate acts as an intermediary element that decouples the programming and sensing functions. It provides a stable, predictable current path for sensing that is independent of the filament position created during programming, thus maintaining manufacturing simplicity while improving sensing reliability
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 proposed solution enables accurate identification of the un-programmed/programmed state of memory cells, regardless of the conductive filament's position, by ensuring the sensing current is higher for un-programmed cells and lower for programmed cells, thus correcting the errors in conventional read operations.
Implementation Method 1
The sensing amplifier generates a sensing current and identifies a state of the memory cell based on the sensing current
Implementation Method 2
The current sink generates a reference current being equivalent to a summation of the sensing current and a cell current flowing through the memory cell. The reference current is constant
Implementation Method 3
The OTP memory utilizes permanent MOS-gate-oxide breakdown as a programming scheme. When the NMOS memory cell is programmed, a programming voltage Vpgm is applied to the gate terminal, and defects are generated at the gate oxide, causing a conductive filament
Data Source
AI summary
A sensing module, a memory device, and a sensing method are provided to perform a read operation so that the un-programmed/programmed state of a memory cell is identified. The sensing module includes a sensing amplifier and a current sink, and both are electrically connected to the memory cell. The sensing amplifier generates a sensing current and identifies the un-programmed/programmed state of the memory cell accordingly. The current sink receives a reference current being equivalent to the summation of the sensing current and a cell current flowing through the memory cell. The reference current is constant, and the sensing current is changed with the cell current. The cell current is generated based on a high read voltage and a low read voltage applied to the memory cell. The sensing current is higher if the memory cell is un-programmed, and the sensing current is lower if the memory cell is programmed.