OTP Memory Cell Structure for Stable Anti-Fuse State Reading
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Solution Overview
Problem
Existing one-time-programmable (OTP) memory elements in integrated circuits face challenges in efficiently determining the programmed state due to variations in read voltage thresholds, leading to inaccuracies in data retention and retrieval.
Innovation Solution
The implementation of a novel OTP memory cell structure with a programmable anti-fuse device that includes a substrate, source and drain regions, and a gate oxide, where programming is achieved by breaking down the gate oxide to minimize resistance, and data is read based on current path presence or absence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a programming electric field is applied across the dielectric material layer to break it down and decrease resistance, then the anti-fuse bit is programmed, but variations in read voltage thresholds occur leading to inaccuracies in data retention and retrieval
Solution Approach 1:
A reference cell with identical structure to the anti-fuse bit but without the programming electric field is introduced as an intermediary element. This reference cell provides a stable reference point for voltage comparison during read operations, eliminating the measurement precision issues caused by variations in read voltage thresholds. The reference cell allows accurate determination of the anti-fuse bit's programmed state through voltage differential measurement.
2Ease of operation
If the gate oxide is broken down to minimize resistance for programming, then data can be read through current path detection, but the structure becomes more complex requiring additional reference cells
Solution Approach 1:
The memory device is segmented into multiple identical anti-fuse bit cells and reference cells arranged in parallel. Each anti-fuse bit cell operates independently with its own programming and reading mechanism, while the reference cells provide distributed reference points. This segmentation allows the complex reference cell structure to be replicated and distributed, making the overall system more manageable and scalable despite the increased individual cell 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
Ensures reliable data retention and accurate data reading by distinguishing between programmed and un-programmed states through distinct current paths, enhancing the reliability and efficiency of OTP memory operations.
Implementation Method 1
a programming electric field is applied across the dielectric material layer to sustainably alter (e.g., break down) the dielectric material, thus decreasing the resistance of the dielectric material layer
Implementation Method 2
a read voltage is applied across the dielectric material layer and a resultant current is read
Data Source
AI summary
An OTP memory device includes a substrate, a first transistor, a second transistor, a first word line, second word line, and a bit line. The first transistor includes a first gate structure, and first and second source/drain regions on opposite sides of the first gate structure. The second transistor is operable in an inversion mode, and the second transistor includes a second gate structure having more work function metal layers than the first gate structure of the first transistor, and second and third source/drain regions on opposite sides of the second gate structure. The first word line is over and electrically connected to the first gate structure of the first transistor. The second word line is over and electrically connected to the second gate structure of the second transistor. The bit line is over and electrically connected to the first source/drain region of the first transistor.