CSONOS Logic Element Non-Destructive Read Mechanism
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Solution Overview
Problem
Reading the state of SONOS transistors disturbs the trapped charge, leading to a reduction in data integrity due to the shrinking sense window, which affects the reliability of stored information.
Innovation Solution
A complementary SONOS (CSONOS) logic element is implemented using a pair of NMOS and PMOS transistors with a specific gate stack configuration that allows for programming and erasing without disturbing the trapped charge, enabling non-destructive reading by applying voltages that maintain the same potential across all terminals of the transistors, thus preserving data integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reading is performed by applying voltage across SONOS transistor and sensing current, then logic state can be detected, but trapped charge is disturbed causing sense window to shrink and data integrity to reduce
Solution Approach 1:
The invention segments the reading operation into two distinct phases: a non-destructive sensing phase that detects the logic state without significantly disturbing trapped charge, and a periodic reprogramming phase that restores any degraded charge. This segmentation allows continuous reading while maintaining data integrity through occasional restoration operations.
Solution Approach 2:
The invention implements preliminary reprogramming actions at scheduled intervals before the trapped charge can significantly degrade. By proactively restoring the charge state before reading operations cause substantial sense window shrinkage, the system maintains data integrity and prevents cumulative degradation from affecting measurement precision.
2Productivity
If continuous reading operations are performed on SONOS transistors, then data can be accessed, but the sense window shrinks over time reducing the reliability of stored information
Solution Approach 1:
The invention implements periodic reprogramming operations at predetermined intervals to restore trapped charge that has degraded from continuous reading operations. This periodic restoration maintains the sense window stability while allowing continuous data access in between reprogramming cycles, thus preserving both productivity and reliability.
3Speed
If high current is used to read transistor state quickly, then reading speed is improved, but more trapped charge is disturbed reducing data integrity
Solution Approach 1:
The invention optimizes the reading current parameter to operate at a level that provides sufficient reading speed while minimizing disturbance to trapped charge. By carefully selecting and maintaining this optimal current parameter, the system achieves fast reading without the trade-off of significant charge disturbance, thus improving speed without sacrificing reliability.
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 effectively maintains data integrity by allowing for the reading of logic states without disturbing the trapped charge, resulting in a stable sense window over time, even after endurance cycling, ensuring reliable data retention.
Implementation Method 1
A SONOS transistor is a type of insulated gate field effect transistor with an oxide-nitride-oxide stack (ONO stack) instead of a single oxide layer. SONOS transistors can be fabricated in large arrays where each transistor can store one bit of information. A single SONOS transistor can be switched between a normally off state (logical 0) and a normally on state (logical 1) by storing charge in a charge-trapping layer
Implementation Method 2
The state of the SONOS transistor can be read by applying a voltage across the transistor and sensing the current that flows through the transistor. If the current is less than some specified maximum leakage current, the transistor is read as off. If the current is greater than some specified minimum conduction current, the transistor is read as on
Data Source
AI summary
A complementary SONOS-type (CSONOS) logic device is programmed and erased with a common voltage. The programming method involves reading the logic state of a complementary pair without disturbing the logic state after setting the complementary pair of non-volatile trapped-charge memory devices, including a first memory device and a second memory device, to a first logic state or a second logic state with a common voltage to control the complementary pair. The CSONOS device retains data integrity over extended read endurance cycles.