Deep Trench Spacer Isolation for SOI Capacitors
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Solution Overview
Problem
Current processing techniques for deep trench capacitors in SOI substrates are imperfect, particularly in controlling recess depth, which can lead to short circuits due to inadequate isolation between the base substrate and the conductive layer as semiconductor structures shrink in size.
Innovation Solution
A method involving recessing a node dielectric and conductive layers below a buried oxide layer, depositing a spacer along the trench sidewall and bottom, performing angled ion implantation or bombardment to remove the spacer portion, and depositing a third conductive layer to fill the trench, ensuring robust isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If current processing techniques are used for recessing node dielectric and conductive layers, then the fabrication process is simple, but the recess depth control is poor leading to short circuits
Solution Approach 1:
A spacer is deposited along the sidewall of the deep trench before the final recessing step. This spacer serves as a preliminary structure that defines the maximum recess depth, preventing the node dielectric and conductive layers from being recessed too deeply and causing short circuits between the base substrate and the conductive layer.
Solution Approach 2:
The spacer acts as an intermediary element between the trench formation process and the final capacitor structure. It provides a physical barrier that mediates the recessing process, ensuring precise depth control while allowing the rest of the fabrication process to proceed with standard techniques.
2Reliability
If the recess depth is increased to improve isolation, then the isolation between base substrate and conductive layer is improved, but the risk of short circuit increases due to imperfect processing
Solution Approach 1:
The spacer is deposited in advance to establish a precise depth limit before the recessing operation. This preliminary action ensures that even with processing variations, the node dielectric and conductive layers will not be recessed beyond the spacer's position, maintaining reliable isolation while preventing short circuits.
Solution Approach 2:
The spacer provides a cushioning effect by acting as a protective barrier that prevents over-recessing. It compensates for processing imperfections by providing a physical stop that ensures the recess depth remains within safe limits, thereby cushioning against the harmful effect of short circuits.
3Length of moving object
If semiconductor structures are shrunk to continue scaling, then the device size is reduced, but the isolation requirements become more stringent and harder to meet
Solution Approach 1:
The spacer is deposited as a preliminary depth-defining structure before the recessing step. This approach provides built-in precision control that is particularly valuable when scaling to smaller device dimensions, where even minor variations in recess depth can compromise isolation. The spacer ensures consistent, precise depth control regardless of the absolute size of the structure.
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 enhances spacer isolation, reducing the risk of short circuits and alleviating the challenge of precise recess depth control, thereby improving the reliability of deep trench capacitors.
Implementation Method 1
removing the spacer from the bottom surface of the opening
Implementation Method 2
Performing at least one of an ion implantation and an ion bombardment in one direction at an angle into an upper portion of the spacer
Implementation Method 3
Performing at least one of an ion implantation and an ion bombardment in one direction at an angle into an upper portion of the spacer
Implementation Method 4
depositing a spacer along a sidewall of the deep trench and the bottom surface of the opening
Data Source
AI summary
A method of forming improved spacer isolation in deep trench including recessing a node dielectric, a first conductive layer, and a second conductive layer each deposited within a deep trench formed in a silicon-on-insulator (SOI) substrate, to a level below a buried oxide layer of the SOI substrate, and creating an opening having a bottom surface in the deep trench. Further including depositing a spacer along a sidewall of the deep trench and the bottom surface of the opening, and removing the spacer from the bottom surface of the opening. Performing at least one of an ion implantation and an ion bombardment in one direction at an angle into an upper portion of the spacer. Removing the upper portion of the spacer from the sidewall of the deep trench. Depositing a third conductive layer within the opening.