Nonvolatile Memory Voltage Adjustment for Temperature-Dependent Breakdown
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Solution Overview
Problem
Nonvolatile semiconductor memories using anti-fuse elements face challenges in ensuring complete breakdown of the insulating film due to voltage and temperature dependencies, leading to inconsistent program times and potential reliability issues.
Innovation Solution
A nonvolatile semiconductor memory design that includes a memory cell array with insulating films programmed by electric stress, utilizing a power supply circuit that adjusts the program voltage based on a negative temperature coefficient and incorporates a band gap reference circuit with variable resistive elements and diodes to generate a reference voltage, ensuring consistent breakdown times across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the program operation is shortened to reduce excessive electric stress, then reliability is improved, but the insulating film may be incompletely broken leading to false reads
Solution Approach 1:
The power supply circuit monitors the breakdown state of the insulating film through sensing and dynamically adjusts the program voltage based on feedback signals. When the insulating film is completely broken, the sensing circuit stops applying voltage, preventing excessive electric stress while ensuring complete breakdown to avoid false reads.
Solution Approach 2:
The patent dynamically changes the program voltage parameter based on temperature conditions and breakdown state. The power supply circuit adjusts voltage levels in real-time during the program operation to optimize both breakdown completeness and reliability, rather than using a fixed voltage throughout the process.
2Manufacturing precision
If the program operation is lengthened to ensure complete breakdown, then read characteristic is improved, but excessive electric stress is applied causing reliability problems
Solution Approach 1:
The sensing circuit continuously monitors the insulating film breakdown state and provides feedback to the power supply circuit. When complete breakdown is detected, the system automatically stops applying voltage, preventing excessive electric stress while ensuring the insulating film is completely broken for reliable reading.
Solution Approach 2:
The insulating film itself serves as the sensing element - its breakdown state is directly detected through the circuitry. The system uses the film's own electrical characteristics to determine when breakdown is complete, eliminating the need for separate monitoring mechanisms and reducing overall operation time.
3Device complexity
If a fixed program voltage is used, then device complexity is reduced, but program time varies with temperature leading to inconsistent performance
Solution Approach 1:
The power supply circuit transitions from a static fixed voltage approach to a dynamic voltage adjustment system. The program voltage is continuously adapted based on real-time temperature sensing and breakdown state monitoring, ensuring consistent program times across different temperature conditions while maintaining manageable device complexity through integrated circuits.
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 maintains constant breakdown times and reduces the risk of false writes by adjusting program voltages according to temperature, thereby ensuring reliable data storage across different environmental conditions.
Implementation Method 1
a power supply circuit that supplies to the memory cell a program voltage for the electric stress depending on a negative temperature coefficient
Implementation Method 2
a band gap reference circuit, the band gap reference circuit including plural resistance elements and plural diodes to generate a reference voltage
Implementation Method 3
when a high voltage for an electric stress is applied to the anti-fuse element once, a composition of the insulating film is broken to lower an electric resistance
Data Source
AI summary
A nonvolatile semiconductor memory according to an aspect of the invention includes a memory cell array and a power supply circuit. The memory cell array includes memory cells each having an insulating film and being programmed to store information by inflicting an electric stress on the insulating film to break the insulating film. The power supply circuit supplies to the memory cell a program voltage for the electric stress depending on a negative temperature coefficient the electric stress.