OTP Memory Test Structures for Pretesting Support Circuitry
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Solution Overview
Problem
One-Time Programmable (OTP) memory devices present challenges in testing, as 100% testing is impossible without rendering the memories unusable, leading to statistical risks and waste in manufacturing batches.
Innovation Solution
Incorporating dedicated memory test cells to pretest the support circuitry associated with regular OTP memory cells, allowing for determination of usability without programming the regular cells, thereby avoiding waste and ensuring only usable memories are used for operational purposes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If 100% testing is performed on OTP memory devices, then testing completeness is improved, but the memories become unusable for other purposes
Solution Approach 1:
The memory array is segmented into two distinct types of cells: dedicated test cells and regular OTP memory cells. The test cells are specifically designated for testing purposes only, while the regular cells remain available for operational use. This segmentation allows complete testing of the memory array through the test cells without consuming the regular cells, thereby resolving the contradiction between testing completeness and memory usability.
Solution Approach 2:
Dedicated test cells serve as intermediary elements that mediate between the testing process and the regular memory cells. These test cells act as placeholders or representatives that can be programmed and tested without affecting the regular OTP memory cells, enabling 100% testing coverage while preserving the usability of the regular cells for their intended operational purposes.
2Productivity
If sample testing is performed on OTP memory devices, then memory usability is preserved, but statistical risk factors increase and memories are wasted
Solution Approach 1:
By segmenting the memory array into dedicated test cells and regular OTP cells, the system eliminates the need for sample testing. The test cells provide a complete test representative of the entire memory array, ensuring 100% testing coverage without statistical risk factors. This segmentation allows all regular memory cells to be used for operational purposes while maintaining high testing reliability through the dedicated test cells.
Solution Approach 2:
The dedicated test cells function as copies or representatives of the regular OTP memory cells. These test cells replicate the same programming and reading characteristics as the regular cells, allowing them to serve as accurate test subjects that reflect the performance of the entire memory array without requiring actual consumption of the regular cells for testing.
3Ease of manufacture
If regular OTP memory cells are used for testing, then testing can be performed, but the cells are rendered unusable for operational purposes
Solution Approach 1:
The memory array is divided into dedicated test cells and regular OTP memory cells with distinct functions. The test cells are specifically designed and positioned to facilitate complete testing of the memory array, while the regular cells are preserved for operational use. This segmentation ensures that testing capability is achieved without sacrificing memory yield, as the regular cells remain fully functional after the testing process.
Solution Approach 2:
The testing function is extracted from the regular OTP memory cells and assigned to separate dedicated test cells. By taking out the testing responsibility from the regular cells, the system allows the regular cells to maintain their primary operational function while the extracted test cells handle all testing activities, thereby preserving memory yield and productivity.
Data Source
AI summary
One Time Programmable (OTP) memory structures and methods for pretesting the support circuitry are provided. A group of dedicated test cells associated with one or more groups of regular OTP cells are used to test the support circuitry for the regular OTP cells. The dedicated cells are programmed and read. The read values are compared to the programmed values or expected values. As a result of the comparison, failing memories may be designated “Not Usable”, while regular OTP cells of passing memories can be programmed for their purpose resulting in elimination of wasted memories during test.