Crested Barrier Injector for NROM Erase Reliability
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Solution Overview
Problem
Current nitride read-only memory (NROM) cells face challenges in efficient erase operations due to the reliance on hot hole injection, which can lead to reliability issues and charge redistribution problems, especially in scaling and reliability aspects.
Innovation Solution
The introduction of a crested barrier injector with materials like nitride, silicon-rich nitride, or oxynitride between the charge-storage stack and the gate or substrate, facilitating hole tunneling for erase operations while minimizing charge trapping and maintaining efficient electron injection for programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hot hole injection is used for erase operations in NROM cells, then erase capability is achieved, but reliability issues and charge redistribution problems occur
Solution Approach 1:
An injector layer is introduced as an intermediary component between the charge storage nitride layer and the oxide layer. This injector layer mediates the hole injection process during erase operations, enabling controlled hole tunneling while preventing direct hot hole injection that causes charge redistribution. The injector layer acts as a selective filter that allows holes to pass through to erase the charge storage region while blocking the harmful side effects of uncontrolled hot hole injection.
Solution Approach 2:
The patent replaces the hot hole injection mechanism with a hole tunneling mechanism facilitated by the injector layer. Instead of relying on hot hole injection that causes reliability issues, the system uses quantum mechanical tunneling through the injector layer to achieve erase operations. This substitution of the underlying physical mechanism eliminates charge redistribution problems while maintaining erase capability.
2Reliability
If conventional oxide layers are used in the charge storage stack, then insulation is provided, but hole tunneling efficiency is reduced
Solution Approach 1:
The patent modifies the energy band parameters of the charge storage stack by introducing the injector layer with specific material properties. The injector layer has a carefully selected band structure that creates favorable band alignment, reducing the band offset between the charge storage nitride layer and the oxide layer. This parameter change enables more efficient hole tunneling during erase operations while maintaining the insulating stability of the oxide layers.
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 enhances the efficiency and reliability of erase operations by reducing band offset and modulating hole-tunneling current, thereby improving the overall performance and scalability of NROM cells.
Implementation Method 1
facilitating hole tunneling for erase operations
Implementation Method 2
reducing band offset and modulating hole-tunneling current
Data Source
AI summary
In a nonvolatile memory (NVM) cell, an injector having one or more layers of material with a lower potential barrier for holes is disposed between a charge storage stack and a source of holes (the gate for top injection, the substrate for bottom injection), to facilitate hole tunneling from the source of holes into the charge-storage layer of the charge storage stack. The injector has a barrier potential for holes which is less than an insulating layer of the charge-storage stack which is oriented towards the source of holes. A multi-layer crested barrier injector may have layers of increasing potential barriers for holes from the source to the charge-storage layer. Methods of operating NVM cells are disclosed. The NVM cell may be NROM, SONOS, or other oxide-nitride technology NVM cells such as SANOS, MANOS, TANOS.