Capacitor-Transistor Strap Connections for DRAM Memory Cells
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Solution Overview
Problem
Current capacitor-transistor strap connections in DRAM memory cells face challenges in efficient charge transfer and structural integrity, leading to potential bridging issues and limitations in epitaxial growth.
Innovation Solution
A deep trench capacitor structure is fabricated with a collar of electrical insulator and a notch that connects a fin-type field effect transistor (FinFET) to the capacitor electrode via a connection strap, enhancing charge transfer and preventing bridging by confining epitaxial growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional capacitor-transistor strap connection is used, then the structure is simpler, but charge transfer efficiency is reduced and bridging issues occur
Solution Approach 1:
The connection structure is segmented into distinct functional components: a collar structure with insulating material, a defined notch region, and a strap connection. This segmentation isolates the charge transfer path from surrounding structures, preventing bridging while maintaining efficiency.
Solution Approach 2:
An insulating collar structure acts as an intermediary between the capacitor electrode and the transistor strap connection. This intermediary prevents direct contact that could cause bridging, while still allowing controlled charge transfer through the defined notch region.
2Reliability
If the collar structure is made completely enclosed, then bridging is prevented, but charge transfer is blocked
Solution Approach 1:
The collar structure is segmented with a defined notch region that breaks the continuous insulating material. This allows charge transfer through the notch while the remaining collar structure maintains bridging prevention, achieving both objectives simultaneously.
Solution Approach 2:
The insulating collar has different properties in different regions: the notch region allows charge transfer while the rest of the collar provides insulation and bridging prevention. This local differentiation of properties resolves the contradiction between enclosed protection and open transfer.
3Area of stationary object
If epitaxial growth is allowed to proceed freely, then surface area for contacts is increased, but bridging between structures occurs
Solution Approach 1:
The insulating collar structure is formed in advance before epitaxial growth occurs. This preliminary action defines the boundaries within which epitaxial growth can proceed, ensuring that increased surface area does not lead to bridging between adjacent structures.
Solution Approach 2:
The insulating collar acts as a mediator that confines epitaxial growth to specific regions. The collar's insulating material prevents lateral growth from causing bridges, while still allowing vertical growth to increase contact surface area.
Data Source
AI summary
Capacitor strap connections for a memory cell and device structures for making such capacitor strap connections. A deep trench capacitor is formed in a substrate. A collar comprised of an electrical insulator is formed at least partially inside an upper section of a deep trench in which the deep trench capacitor is formed. A portion of the collar is removed to define a notch extending through the collar, and a connection strap is formed in the notch. A fin is formed from a portion of the substrate, and is coupled by the connection strap with an electrode of the deep trench capacitor that is located inside the deep trench.