Antifuse Replacement Determination Circuit for Semiconductor Memory
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Solution Overview
Problem
Conventional antifuse replacement determination circuits in semiconductor memory devices often produce unstable results due to insufficiently decreased resistance of the destroyed AF element, leading to erroneous determinations and reduced yield, with devices being classified as substandard products.
Innovation Solution
An antifuse replacement determination circuit that charges a node of the antifuse element to a predetermined voltage and allows self-discharge, then compares the voltage with multiple reference voltages after a predetermined time, using three reference levels to determine if the replacement was performed correctly, thereby improving the accuracy of the determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single reference level is used for AF element destruction determination, then the determination process is simple, but the determination accuracy is insufficient leading to unstable results
Solution Approach 1:
The patent divides the determination process into multiple stages, each comparing the voltage at node X0 with a different reference level (VREF0, VREF1, VREF2). This segmentation of the measurement process into discrete comparison steps enables more accurate determination of AF element destruction status while maintaining a systematic and manageable determination flow.
2Reliability
If the resistance of the destroyed AF element decreases sufficiently, then the replacement determination becomes more reliable, but the determination process becomes more complex
Solution Approach 1:
The patent implements a feedback mechanism where the determination result from comparing with the first reference level (VREF0) is used to control whether subsequent comparisons with VREF1 and VREF2 are performed. This feedback-based conditional execution improves reliability by adaptively adjusting the determination process based on intermediate results, while avoiding unnecessary operations that would increase complexity.
3Stability of the object's composition
If multiple reference levels are used for voltage comparison, then the determination stability improves, but the screening process time increases
Solution Approach 1:
The patent performs a preliminary comparison with reference level VREF0 before proceeding to comparisons with VREF1 and VREF2. This preliminary action allows the system to quickly eliminate cases where the AF element is clearly not destroyed, avoiding unnecessary subsequent comparison steps and reducing the average screening time while maintaining determination stability through multi-level verification when needed.
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
This approach reliably detects the completion of AF replacement, reducing the production of substandard products and increasing yield by providing stable determination results during re-screening and actual use.
Implementation Method 1
an antifuse element charging circuit for charging a node of the antifuse element to have a predetermined voltage, and making charge at the node self-discharge via the antifuse element
Implementation Method 2
a comparison and determination circuit for comparing a voltage at the node of the antifuse element with a plurality of reference voltages
Data Source
AI summary
An antifuse replacement determination circuit of a semiconductor memory device, in which the address of a bad memory cell is stored by destroying the insulation of an antifuse element, includes a charging circuit for charging a node of the antifuse element to have a predetermined voltage, and making the charge at the node self-discharge via the antifuse element after the charging of the node is completed; a comparison and determination circuit for comparing the voltage at the node of the antifuse element with a plurality of reference voltages when a predetermined time has elapsed after the completion of the charging of the node; and a determination part for determining, based on a determination result with respect to the comparison using the plurality of reference voltages in the comparison and determination circuit, whether or not replacement of the bad memory cell has been performed normally by using the antifuse element.