Nonvolatile Memory Gate Electrode Curvature
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Nonvolatile memory devices using localized charge storage face issues with spatial variations in tunneling rates due to sharp corners in gate electrodes, leading to inefficient erase processes and data retention problems.
Innovation Solution
Designing a nonvolatile memory cell with a gate electrode having a midsection and edge portions where the edge portions converge towards the opposing surface, or using a multilayer gate electrode with sublayers of different widths to reduce spatial variations in tunneling rates, thereby minimizing locally enhanced electric fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gate electrodes with sharp corners are used, then manufacturing is simpler, but spatial variations in tunneling rate increase causing erase inefficiency and data retention problems
Solution Approach 1:
The gate electrode is designed with rounded corners instead of sharp corners. The first surface of the gate electrode includes a midsection and two edge portions where the edge portions extend away from the plane defined by the midsection, creating a curved transition. This curvature eliminates the sharp corners that cause locally enhanced electric fields, thereby reducing spatial variations in tunneling rate and improving data retention and erase efficiency.
2Reliability
If gate electrodes with extended edge portions are used, then tunneling rate uniformity improves, but manufacturing precision requirements increase
Solution Approach 1:
The rounded corner design with edge portions extending away from the midsection plane provides a gradual geometric transition that is easier to manufacture with standard semiconductor fabrication processes compared to sharp corners. The curvature naturally distributes the electric field more uniformly without requiring extremely tight tolerances, thus achieving tunneling rate uniformity while maintaining reasonable manufacturing precision requirements.
3Productivity
If sharp cornered gate electrodes are used, then device structure is simpler, but erase process efficiency decreases due to locally enhanced electric fields
Solution Approach 1:
By rounding the corners of the gate electrode so that edge portions extend away from the midsection plane, the design eliminates the sharp corners that create locally enhanced electric fields. This curvature ensures more uniform electric field distribution across the charge storage layer during erase operations, preventing electrons from being inadvertently added at cell edges and improving overall erase efficiency.
Solution Approach 2:
The gate electrode design applies different geometries to different regions: the midsection maintains a standard planar configuration while the edge portions are extended and rounded. This local modification targets specifically the problematic corner regions where enhanced electric fields occur, improving erase efficiency without unnecessarily complicating the entire gate electrode structure.
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 configuration reduces tunneling variations across the memory cell, improving data retention and erase efficiency by maintaining a more uniform electric field, which enhances the performance of nonvolatile memory devices.
Implementation Method 1
For some types of localized charge storage memory devices, the charging and discharging of the charge storage layer is accomplished by electron (or hole) tunneling.
Implementation Method 2
Such sharp corners can create locally enhanced electric fields and, consequently, spatial variations in the tunneling rate during charging and/or discharging of the memory device.
Data Source
AI summary
A nonvolatile memory cell includes a substrate comprising a source, drain, and channel between the source and the drain. A tunnel dielectric layer overlies the channel, and a localized charge storage layer is disposed between the tunnel dielectric layer and a control dielectric layer. A gate electrode has a first surface adjacent to the control dielectric layer, and the first surface includes a midsection and two edge portions. According to one embodiment, the midsection defines a plane, and at least one edge portion extends away from the plane. Preferably, the edge portion extending away from the plane converges toward an opposing second surface of the gate electrode. According to another embodiment, the gate electrode of the nonvolatile memory cell includes a first sublayer and a second sublayer of a different width on the first sublayer.