ONO Stack Quality Monitoring via Differential Tunneling Voltage
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Solution Overview
Problem
Conventional methods for testing oxide-nitride-oxide (ONO) stack quality in non-volatile memory transistors are inefficient, as they require weeks to identify issues with the stack composition, leading to reduced yield and revenue due to delayed detection of malfunctions during the fabrication process.
Innovation Solution
A method and structure for determining ONO stack quality by measuring differential tunneling voltage through a corona charge method, allowing for inline monitoring of program/erase efficiency and threshold voltage window, enabling early detection of stack quality issues during fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional testing methods are used to test completed packaged devices, then measurement precision of ONO stack quality is achieved, but loss of time increases significantly (weeks after deposition)
Solution Approach 1:
The patent performs ONO stack quality testing during the fabrication process itself, before the device is completed and packaged. The tunneling voltage measurement is conducted on the ONO stack immediately after formation, allowing early detection of quality issues without waiting weeks for conventional post-packaging testing.
2Reliability
If conventional post-fabrication testing is performed, then reliability of measurement is ensured, but productivity decreases due to delayed yield optimization
Solution Approach 1:
The measurement is performed preliminarily during fabrication rather than after completion. This allows real-time monitoring and immediate corrective actions to be taken, maintaining measurement reliability while significantly improving productivity by preventing defective devices from proceeding through subsequent fabrication steps.
Solution Approach 2:
The patent implements a feedback mechanism where tunneling voltage measurements are used to monitor ONO stack quality in real-time during fabrication. This feedback allows process adjustments to be made immediately, optimizing yield and maintaining high productivity while ensuring reliable quality assessment.
3Measurement precision
If complete device fabrication is required before testing, then measurement accuracy is improved, but loss of time increases and yield is reduced
Solution Approach 1:
The patent extracts the quality measurement function from the complete device testing process. Instead of waiting for the entire device to be fabricated and packaged, the measurement is performed on the ONO stack structure itself during fabrication, separating the critical quality assessment from the complete device assembly process.
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
Enables predictive monitoring of non-volatile memory transistor performance without waiting for complete device fabrication, ensuring compliance with specified minimum threshold voltage windows and extending device operating life.
Implementation Method 1
measuring a differential tunneling voltage through a corona charge method
Implementation Method 2
The positive bias causes electrons from source and drains regions of the transistor to tunnel through the lower oxide layer of the ONO stack
Data Source
AI summary
Embodiments of structures and methods for determining operating characteristics of a non-volatile memory transistor comprising a charge-storage-layer and a tunneling-layer are described. In one embodiment, the method comprises: forming on a substrate a structure including a nitrided tunneling-layer and a charge-storage-layer overlying the tunneling-layer comprising a first charge-storage layer adjacent to the tunneling-layer, and a second charge-storage layer overlying the first charge-storage layer, wherein the first charge-storage layer is separated from the second charge-storage layer by a anti-tunneling layer comprising an oxide; depositing a positive charge on the charge-storage-layer and determining a first voltage to establish a first leakage current through the charge-storage-layer and the tunneling-layer; depositing a negative charge on the charge-storage-layer and determining a second voltage to establish a second leakage current through the charge-storage-layer and the tunneling-layer; and determining a differential voltage by calculating a difference between the first and second voltages.