Anti-Fuse Gate Dielectric Breakdown Stability
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Solution Overview
Problem
The existing OTP unit cells in semiconductor devices face instability in gate dielectric breakdown during writing operations due to leakage currents and incomplete breakdown of the gate dielectric layer, leading to reduced data sensing margins and device malfunction.
Innovation Solution
The proposed solution involves an anti-fuse structure with a gate dielectric layer comprising a first and second dielectric layer of different thicknesses, where the second dielectric layer breaks down to provide permanent conductivity between the gate electrode and junction region, while the first dielectric layer maintains the writing voltage, ensuring stable breakdown and improved data sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single thin gate dielectric layer is used in the anti-fuse, then the breakdown can occur more easily, but the breakdown is not stable and leads to leakage currents and device malfunction
Solution Approach 1:
The gate dielectric layer is divided into two separate layers: a first gate dielectric layer and a second gate dielectric layer. This segmentation allows each layer to serve a specific function - the first layer provides stable breakdown characteristics while the second layer ensures complete breakdown, thereby resolving the reliability issue without requiring a single complex thick layer.
Solution Approach 2:
Different regions of the gate dielectric structure are assigned different thicknesses and materials. The first gate dielectric layer has a thickness in the range of 50-150 nm providing stable breakdown, while the second gate dielectric layer has a thickness of 10-50 nm ensuring complete breakdown. This local differentiation of properties optimizes both stability and completeness of breakdown.
2Reliability
If the gate dielectric layer is partially broken-down, then the field effect is reduced, but leakage currents occur between the well and channel stop region
Solution Approach 1:
The first gate dielectric layer is designed to break down first during the writing operation, creating a controlled initial breakdown. This preliminary breakdown action establishes a conductive path that allows subsequent complete breakdown of the second layer without causing uncontrolled leakage currents, thereby preventing the harmful effects of partial breakdown.
Solution Approach 2:
The two-layer gate dielectric structure acts as a cushioning mechanism against the harmful effects of improper breakdown. The first layer absorbs the initial breakdown energy in a controlled manner, preventing direct damage to the channel stop region and eliminating the condition that would lead to leakage currents and reduced data sensing margins.
3Reliability
If a thick gate dielectric layer is used, then the breakdown stability is improved, but the writing voltage requirement increases due to sheet resistance
Solution Approach 1:
The gate dielectric is segmented into two layers with different thicknesses. The first layer (50-150 nm) provides the necessary breakdown stability, while the second thinner layer (10-50 nm) reduces the overall voltage requirement. This segmentation allows the system to achieve both stability and lower power requirements by distributing the voltage stress across two layers rather than requiring a single thick layer.
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 enhances the reliability of the OTP unit cell by maintaining a stable breakdown of the gate dielectric layer, ensuring continuous high field effect and improved data sensing margins during reading operations.
Implementation Method 1
a high field effect occurs between the gate electrode 105 and the substrate 100 and causes a breakdown of the gate dielectric layer 104
Data Source
AI summary
There is provided an anti-fuse, including a gate dielectric layer formed over a substrate, a gate electrode, including a body portion and one or more protruding portions extending from the body portion, the body portion and the one or more protruding portions being formed to contact on the gate dielectric layer, and a junction region formed in a portion of the substrate exposed by sidewalls of the one or more protruding portions.