Void-Free Gap Fill in High Aspect Ratio Trenches via Segmented ALD and Oxidation
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Solution Overview
Problem
Conventional methods for filling shallow trench insulators with high aspect ratios, such as HDPCVD and SACVD, often result in voids and non-conformal films, while emerging flowable oxide processes are limited by high carbon content, failing to effectively eliminate seams during silicon dioxide deposition in gap fill applications.
Innovation Solution
The method involves partially filling trenches with a first silicon dioxide layer using ALD, depositing an amorphous silicon layer, and then filling the trench with a second silicon dioxide layer, followed by an oxidation treatment to convert the amorphous silicon layer to silicon dioxide, densifying the seam material and eliminating voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If HDPCVD process is used to fill trenches with high aspect ratio, then deposition speed is improved, but voids form in the filled trench
Solution Approach 1:
The filling process is divided into multiple ALD cycles with intermediate oxidation steps. The oxide layer is deposited in segments rather than continuously, allowing oxidation to occur between deposition phases. This segmented approach enables complete void elimination while maintaining conformal filling in high aspect ratio trenches.
Solution Approach 2:
The process employs periodic alternation between ALD deposition cycles and oxidation treatments. This periodic action allows the oxide film to be deposited, then oxidized to eliminate voids, repeated until the trench is fully filled. This cyclic process ensures both conformal deposition and void-free filling.
2Manufacturing precision
If SACVD process is used to fill trenches, then conformal deposition is improved, but fill profile control becomes difficult and voids form
Solution Approach 1:
The SACVD process is segmented into multiple thin deposition cycles rather than a single continuous deposition. Each cycle deposits a thin conformal layer that can be fully oxidized to eliminate voids. This segmentation maintains the conformal advantage while enabling complete void elimination through intermediate oxidation steps.
Solution Approach 2:
The process parameters are changed by using atomic layer deposition instead of SACVD, allowing precise control of deposition thickness and rate. The ALD process provides superior conformal coverage and enables the segmented deposition approach that eliminates voids while maintaining ease of manufacture.
3Manufacturing precision
If flowable oxide process is used to fill trenches, then gap filling capability is improved, but film quality deteriorates due to high carbon content
Solution Approach 1:
The material composition is changed by using silicon-based precursors in ALD instead of carbon-based flowable oxide materials. This parameter change maintains the gap filling capability through conformal ALD deposition while eliminating the high carbon content problem, resulting in high quality silicon dioxide film suitable for subsequent wet chemical processes.
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 ensures conformal film deposition and void-free gap filling in trenches with aspect ratios greater than 4:1, improving film quality by eliminating seams and enhancing the reliability of the substrate processing system.
Implementation Method 1
An oxidation treatment is performed on the substrate to oxidize the amorphous silicon layer
Implementation Method 2
The oxidation treatment includes heating the substrate to a process temperature and exposing the substrate to water vapor or molecular oxygen
Implementation Method 3
The first silicon dioxide layer and the second silicon dioxide layer are deposited using an atomic layer deposition (ALD) process
Implementation Method 4
The ALD process uses process gases including Bis(tertiary-butyl-amino)silane (BTBAS), nitrous oxide (N2O) and oxygen (O2)
Data Source
AI summary
A method for filling a trench in a substrate includes partially filling the trench with a first silicon dioxide layer. An amorphous silicon layer is deposited on the silicon dioxide layer. The trench is filled with a second silicon dioxide layer. An oxidation treatment is performed on the substrate to oxidize the amorphous silicon layer.