Etch-Back Protection for 3D Non-Volatile Memory
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Solution Overview
Problem
The existing methods for fabricating non-volatile memory devices with three-dimensional structures face challenges in preventing damage to critical layers such as the charge blocking layer, charge trap layer, tunnel insulation layer, and gate dielectric layer during the etch-back process, leading to degraded data retention and cycling characteristics.
Innovation Solution
A method involving the formation of a second material layer with high etch selectivity over the first material layer, which includes a charge blocking layer, charge trap layer, or tunnel insulation layer, to protect these layers from damage during the etch-back process, and the use of a passivation layer to further prevent damage, ensuring the integrity of the tunnel insulation layer and gate dielectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an etch-back process is used to remove the first material layer from the bottom of the trench, then the manufacturing process can proceed to form the channel, but the first material layer formed on the inner walls of the trench is damaged
Solution Approach 1:
A second material layer is introduced as an intermediary protective layer between the first material layer and the etching environment. This second material layer has high etch selectivity, meaning it can be removed by the etching process while leaving the first material layer intact. The second material layer acts as a sacrificial protective barrier that prevents direct contact between the etchant and the first material layer on the trench inner walls.
Solution Approach 2:
The second material layer is formed on the first material layer before the etch-back process is performed. This preliminary formation of the protective layer ensures that when the etching process is subsequently applied, the first material layer is already protected and will not be damaged. The protective arrangement is established in advance of the harmful etching action.
2Ease of manufacture
If the first material layer is removed from the bottom of the trench, then the channel can be formed, but the data retention characteristic and cycling characteristic are degraded
Solution Approach 1:
The second material layer serves as a protective intermediary that prevents the etching process from damaging the first material layer on the trench inner walls. By blocking the etchant from直接接触 the first material layer, the structural integrity and functional properties of the first material layer are preserved, thereby maintaining data retention and cycling characteristics.
Solution Approach 2:
The second material layer is formed in advance of the etching process to preemptively protect the first material layer. This preliminary protective arrangement ensures that when the etch-back process is performed to enable channel formation, the first material layer remains undamaged and the device maintains its reliability characteristics.
3Ease of manufacture
If the first material layer is removed from the bottom of the trench, then the channel can be formed, but the cycling characteristic is degraded
Solution Approach 1:
The second material layer acts as a protective mediator that shields the first material layer from damage during the etch-back process. By preventing direct etching of the first material layer on the trench inner walls, the cycling characteristic is preserved while still enabling channel formation through removal of the second material layer.
Solution Approach 2:
The second material layer is formed beforehand to provide preliminary protection to the first material layer. This advance protective measure ensures that the subsequent etching process can proceed to form the channel without degrading the cycling characteristic of the device.
4Manufacturing precision
If a passivation layer is formed over the first material layer, then damage to the first material layer is prevented, but the device complexity increases
Solution Approach 1:
The second material layer serves as a protective intermediary layer formed over the first material layer. Although this adds a layer to the structure, the second material layer is designed with high etch selectivity, meaning it can be selectively removed after serving its protective function. This selective removability mitigates the complexity issue by allowing the protective layer to be temporary rather than permanent.
Solution Approach 2:
The second material layer is chosen to have specific etch selectivity parameters that differ from the first material layer. This parameter difference allows the second material layer to be selectively removed by the etching process while protecting the first material layer. The change in etch selectivity parameter enables the protective layer to serve its function and then be easily removed, reducing the long-term structural complexity.
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 effectively prevents damage to the critical layers, enhancing the data retention and cycling characteristics of the non-volatile memory device, thereby improving its reliability and performance.
Implementation Method 1
forming a second material layer over the first material layer, wherein the second material layer has high etch selectivity with respect to the first material layer
Implementation Method 2
the use of a passivation layer to further prevent damage, ensuring the integrity of the tunnel insulation layer and gate dielectric layer
Data Source
AI summary
A method for fabricating a non-volatile memory device includes alternately stacking a plurality of interlayer dielectric layers and a plurality of conductive layers over a substrate, etching the interlayer dielectric layers and the conductive layers to form a trench which exposes a surface of the substrate forming a first material layer over a resulting structure in which the trench is formed, forming a second material layer over the first material layer, removing portions of the second material layer and the first material layer formed on a bottom of the trench to expose the surface of the substrate, removing the second material layer, and burying a channel layer within the trench in which the second material layer is removed.