Alternating Dielectric Fill Prevents Gate Cut Power Rail Shorts
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Solution Overview
Problem
The etch processes used in forming power rails within gate cut trenches in semiconductor devices often result in electrical shorts due to lateral etching of dielectric layers, which can lead to device failure.
Innovation Solution
A method involving the formation of a multilayer fill of alternating nitride and oxide conformally deposited dielectric layers within the gate cut trench, which obstructs both vertical and lateral etching, preventing the formation of electrical shorts by controlling the aspect ratio of the dielectric layers to stop etching at specific layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-layer dielectric fill is used in the gate cut trench, then the manufacturing process is simpler, but lateral etching occurs during power rail formation causing electrical shorts
Solution Approach 1:
The single-layer dielectric fill is segmented into multiple alternating layers of first and second dielectric materials. This segmentation allows the etching process to selectively remove portions of alternating layers to form etch stops at multiple levels, preventing lateral etching from causing electrical shorts while maintaining manufacturing feasibility through conformal deposition techniques.
Solution Approach 2:
The patent uses composite dielectric structures with alternating layers of different dielectric materials (first and second dielectric materials with different etch selectivity). This composite structure enables differential etching where each layer type can be selectively removed, creating multiple etch stops that prevent lateral etching from compromising device reliability.
2Manufacturing precision
If conformal deposition is used to form alternating dielectric layers, then etching precision is improved, but the device structure becomes more complex
Solution Approach 1:
The conformal deposition process creates local variations in layer thickness and composition, with each alternating layer having specific etch selectivity properties. This local quality differentiation enables precise control over where etching stops occur, allowing high etching precision while managing structural complexity through targeted material placement rather than uniform structures.
Solution Approach 2:
The patent changes material parameters by using alternating dielectric layers with different etch selectivity characteristics. This parameter variation allows the etching process to selectively remove specific layers while leaving others intact, achieving high etching precision. The complexity is managed by selecting dielectric materials with well-established deposition and etch properties.
3Length of moving object
If the gate cut trench is deeply etched to form the power rail opening, then the power rail can be properly formed, but lateral etching increases causing electrical shorts
Solution Approach 1:
The alternating dielectric layers are deposited in advance before the power rail opening etch process. These pre-deposited layers with different etch selectivity serve as predetermined etch stops that control the etching depth and prevent lateral etching. This preliminary action ensures that when the deep etch is performed to create the power rail opening, the etch process automatically stops at the appropriate depth without causing electrical shorts.
Solution Approach 2:
The alternating dielectric layers act as intermediary structures between the trench walls and the etchant. These intermediate layers with differential etch selectivity mediate the etching process by providing selective stop points, allowing the etch to proceed deeply enough to form the power rail opening while preventing uncontrolled lateral etching that would cause electrical shorts.
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 electrical shorts and ensures precise etching, maintaining the integrity of the power rail structure and enhancing the reliability of semiconductor devices by selectively stopping etching processes at designated layers.
Implementation Method 1
a fill material of an alternating sequence of at least two different composition conformally deposited dielectric layers within the gate cut trench
Implementation Method 2
an aspect ratio of the vertically orientated portions of the alternating sequence of the at least two different composition conformally deposited dielectric layers obstructs lateral etching of the gate cut trench during etching to form a power rail opening
Data Source
AI summary
A method of forming a power rail to semiconductor devices that includes forming a gate structure extending from a first active region to a second active region of a substrate, and removing a portion of the gate structure forming a gate cut trench separating the first active region from the second active region. A fill material of an alternating sequence of at least two different composition conformally deposited dielectric layers is formed within the gate cut trench. A power rail is formed in the gate cut trench. An aspect ratio of the vertically orientated portions of the alternating sequence of the at least two different composition conformally deposited dielectric layer obstructs lateral etching of the gate cut trench during etching to form a power rail opening for housing the power rail.