Variable-Thickness Channel Layer for Distorted Memory Cell Cross-Sections
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Solution Overview
Problem
As the number of laminated layers in semiconductor storage devices increases, the cross-sectional shapes of memory cells can become distorted into non-complete circular shapes due to manufacturing issues, leading to deteriorated electrical characteristics such as write characteristics.
Innovation Solution
A semiconductor storage device is designed with a channel layer that has a varying film thickness corresponding to the curvature of the electric charge holder, which is curved in a specific cross-section along the substrate surface. This configuration ensures that the channel layer's thickness adjusts to maintain optimal electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of laminated layers is increased to improve storage capacity, then the storage density is improved, but the cross-sectional shape of memory cells becomes distorted and electrical characteristics deteriorate
Solution Approach 1:
The channel layer is designed with non-uniform thickness, being thicker at curved portions and thinner at straight portions of the memory cell cross-section. This local variation in thickness compensates for the distortion caused by increased laminated layers, maintaining optimal electrical characteristics while preserving high storage capacity.
Solution Approach 2:
The patent changes the geometric parameter of the channel layer from uniform thickness to variable thickness based on the curvature of the memory cell cross-section. This parameter modification allows the structure to accommodate increased laminated layers without suffering from shape distortion-induced performance degradation.
2Ease of manufacture
If the channel layer has uniform thickness, then the manufacturing process is simplified, but electrical characteristics such as write characteristics deteriorate when cross-sectional distortion occurs
Solution Approach 1:
The channel layer implements local quality variation with different thicknesses at different locations. The thicker regions at curved portions provide enhanced electrical performance where distortion occurs, while thinner regions at straight portions maintain manufacturing efficiency. This localized differentiation resolves the contradiction between manufacturing simplicity and electrical reliability.
3Reliability
If the memory cell cross-section remains circular, then electrical characteristics are maintained, but the device complexity increases to prevent distortion in multi-layer structures
Solution Approach 1:
Instead of attempting to maintain a perfect circular cross-section through complex manufacturing controls, the patent inverts the approach by deliberately designing the channel layer thickness to match the expected distorted shape. This accepts the distortion and compensates for it, reducing manufacturing complexity while maintaining electrical performance.
Data Source
AI summary
According to one embodiment, a semiconductor storage device includes a substrate, a first electric charge holder, and a channel layer. At least a part of the first electric charge holder is curved in a first cross section along a surface of the substrate. The channel layer is inside the first electric charge holder in the first cross section. At least a part of the channel layer is curved in the first cross section. The first electric charge holder has a curvature varying in accordance with a position in the first cross section. The channel layer has a film thickness varying in accordance with the curvature of the first electric charge holder in the first cross section.