Self-Aligned Strap Structures in Trench Capacitors
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Solution Overview
Problem
The electrical isolation of conductive straps in trench capacitors is challenging due to misalignment issues, leading to potential electrical shorts with neighboring components in semiconductor devices.
Innovation Solution
A semiconductor structure is formed with a dielectric spacer on the first sidewall of the source region, and a raised source region on the second sidewall, which serves as an etch mask to create self-aligned strap structures electrically isolated from adjacent access transistors, using a conductive strap to contact the inner electrode of the trench capacitor and the raised source region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive strap is formed to connect the inner electrode of a trench capacitor to a source region, then electrical connection is achieved, but misalignment can cause electrical shorts with neighboring components
Solution Approach 1:
Dielectric spacers are formed on the sidewalls of source regions before forming the conductive straps. These spacers serve as preliminary protective structures that define the spatial relationship between the strap and adjacent transistor components, ensuring electrical isolation is established in advance of the connection formation process
Solution Approach 2:
Dielectric spacers act as intermediary structures positioned between the conductive strap and adjacent transistor components. These spacers provide physical and electrical separation, serving as a mediator that prevents direct contact and potential shorts while allowing the strap to maintain its electrical connection function
2Reliability
If dielectric spacers are formed on sidewalls to provide electrical isolation, then electrical shorts are prevented, but device structure becomes more complex
Solution Approach 1:
The dielectric spacers serve multiple functions: they provide electrical isolation between the conductive strap and adjacent transistor components, act as etch masks during fabrication processes, and define the geometric boundaries of the strap structure. This multi-functionality reduces the need for additional separate structures, thereby limiting the increase in device complexity while achieving reliable electrical isolation
Data Source
AI summary
After formation of trench capacitors and source and drain regions and gate structures for access transistors, a dielectric spacer is formed on a first sidewall of each source region, while a second sidewall of each source region and sidewalls of drain regions are physically exposed. Each dielectric spacer can be employed as an etch mask during removal of trench top dielectric portions to form strap cavities for forming strap structures. Optionally, selective deposition of a semiconductor material can be performed to form raised source and drain regions. In this case, the raised source regions grow only from the first sidewalls and do not grow from the second sidewalls. The raised source regions can be employed as a part of an etch mask during formation of the strap cavities. The strap structures are formed as self-aligned structures that are electrically isolated from adjacent access transistors by the dielectric spacers.