Fixed Charge Dielectric Isolation Trenches for High Voltage Scaling
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Solution Overview
Problem
Current transistor structures in CMOS devices face challenges in achieving adequate breakdown voltage and scaling due to limitations in isolation trench width and dielectric materials, which affect the performance of memory devices, particularly in high-voltage operations.
Innovation Solution
Incorporating a fixed charge dielectric layer within the isolation trench between transistors, which increases the breakdown voltage and allows for narrower trench widths, enhancing voltage modulation and stability, and using materials like lanthanum, aluminum, or hafnium oxides to induce a dipole charge for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dielectric materials are used in isolation trenches, then manufacturing is simpler, but breakdown voltage is insufficient for high-voltage operations
Solution Approach 1:
The patent uses a composite dielectric structure consisting of a first dielectric material (e.g., silicon oxide) and a second dielectric material with higher breakdown voltage characteristics (e.g., silicon nitride, silicon oxynitride, or aluminum oxide) deposited in sequence within the isolation trench. This composite structure achieves higher overall breakdown voltage while maintaining manufacturability through standard sequential deposition processes.
Solution Approach 2:
The patent changes the dielectric material parameters by introducing materials with different breakdown voltage characteristics and physical properties (such as silicon nitride with approximately 10-15 MV/cm breakdown strength versus silicon oxide with approximately 10 MV/cm). This parameter change enables the isolation trench to withstand higher voltages while allowing for narrower trench widths.
2Productivity
If isolation trench width is reduced for scaling, then device density increases, but breakdown voltage decreases
Solution Approach 1:
By depositing multiple dielectric layers with complementary properties, the patent achieves high breakdown voltage in narrower trenches. The first dielectric provides good interface characteristics, while the second dielectric provides enhanced breakdown strength, allowing the isolation trench to be narrower while maintaining or improving voltage withstand capability.
Solution Approach 2:
The patent transitions from relying solely on trench width (one dimension) to control breakdown voltage to using a multi-layer dielectric structure (adding the layer dimension). This dimensional change allows narrower trenches to achieve the same or higher breakdown voltage through the cumulative effect of multiple dielectric layers.
3Reliability
If fixed charge dielectric layer is added to increase breakdown voltage, then voltage modulation improves, but device complexity increases
Solution Approach 1:
The patent introduces dielectric materials with inherent fixed charge characteristics (such as silicon nitride or aluminum oxide) that provide voltage modulation and breakdown voltage enhancement. These materials achieve the desired electrical parameter changes through their intrinsic properties rather than requiring additional charge trapping layers or complex structures.
Solution Approach 2:
The second dielectric material serves multiple functions simultaneously: it provides breakdown voltage enhancement, voltage modulation through fixed charge, and acts as part of the isolation structure. This multi-functionality reduces the need for separate specialized layers, thereby limiting the increase in device 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
The use of a fixed charge dielectric layer significantly increases breakdown voltage, enables narrower isolation trenches, and improves transistor voltage modulation, leading to enhanced memory device performance and scalability.
Implementation Method 1
a first dielectric layer adjacent to a bottom of the isolation trench, wherein the first dielectric layer includes a fixed charge
Implementation Method 2
using materials like lanthanum, aluminum, or hafnium oxides to induce a dipole charge for improved performance
Data Source
AI summary
Apparatus and methods are disclosed, including transistors, semiconductor devices and systems. Example semiconductor devices and methods include isolation trenches between transistors that include a dielectric layer that includes a fixed charge. Fixed charge dielectric layers enable trench widths that scale smaller than trenches that do not include fixed charge dielectric layers. This allows increases in device density without sacrificing electronic properties of device shown.