Shallow Trench Isolation Void Prevention via Segmented Deposition
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Solution Overview
Problem
Conventional shallow trench isolation (STI) structures face challenges in forming narrow trenches with high aspect ratios, leading to voids and silicon substrate over-consumption, which affects the electric performance of devices like fin field emission transistors (FinFETs).
Innovation Solution
A method involving the formation of a hard mask, trench creation, removal of the hard mask before filling with isolation material, and a sequence of deposition and etch-back processes to reduce aspect ratios and prevent voids, with a silicon layer serving as an etch stop for planarization, ensuring uniform polishing and improved isolation material quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a trench with high aspect ratio is formed to reduce isolation region size, then integration density is improved, but voids are formed after filling with isolation material
Solution Approach 1:
The filling process is segmented into multiple steps: first filling the trench with isolation material, then performing etch-back to remove the hard mask and excess material, followed by refilling the trench. This segmentation allows the aspect ratio to be effectively reduced during the process, preventing void formation while maintaining small isolation region size.
Solution Approach 2:
The hard mask is removed before filling the trench with isolation material in the refined process. This preliminary action reduces the aspect ratio of the trench beforehand, creating favorable conditions for void-free filling. The sequence of operations is rearranged to perform mask removal at an optimal point in the process flow.
2Ease of manufacture
If flowable chemical vapor deposition is used to fill the trench, then filling is achieved, but silicon substrate is over-consumed altering active area size
Solution Approach 1:
The deposition process is controlled to deposit isolation material in a partial or regulated manner, followed by etch-back steps that remove excess material. This approach prevents over-consumption of the silicon substrate while ensuring complete trench filling. The combination of controlled deposition and selective removal maintains active area dimensions.
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 reduces void formation and enhances the quality of isolation structures, maintaining device performance and integration density by minimizing silicon substrate alteration and ensuring uniform planarization.
Implementation Method 1
a silicon layer is substantially conformally formed to cover the trench and the original surface of the substrate
Implementation Method 2
A first etch process is performed to partially etch back the first isolation material layer to partially expose the trench
Implementation Method 3
A planarization process is performed and allowed to stop on the silicon layer on the original surface of the substrate
Data Source
AI summary
The present invention relates to a method of forming an isolation structure, in which, a trench is formed in a substrate through a hard mask, and deposition, etch back, deposition, planarization, and etch back are performed in the order to form an isolation material layer of the isolation structure after the hard mask is removed. A silicon layer may be formed to cover the trench and original surface of the substrate before the former deposition, or to cover a part of the trench and original surface of the substrate after the former etch back and before the later deposition, to serve as a stop layer for the planarization process. Voids existing within the isolation material layer can be exposed or removed by partially etching the isolation material layer by the former etch back. The later deposition can be performed with a less aspect ratio to avoid forming voids.