Bottom Thick Thermal Oxide Growth in High-Aspect-Ratio Features
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for growing oxide layers in high aspect ratio semiconductor structures face issues such as rapid and uneven oxygen radical consumption, leading to top-thick oxide layers and reduced device reliability due to defects and traps in the formed oxide layers.
Innovation Solution
A method involving the formation of a non-conformal oxide layer on a substrate, followed by an oxidation process to grow a thermal oxide layer underneath, and subsequent selective removal of the non-conformal oxide layer to expose the oxidized portion, allowing for the growth of a bottom thick oxide layer in high aspect ratio features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional thermal oxidation is performed in high aspect ratio features, then oxide layer is formed, but the oxide layer becomes top-thick due to rapid oxygen radical consumption and depletion at the top
Solution Approach 1:
A non-conformal oxide layer is deposited on the substrate before thermal oxidation. This preliminary layer is thicker at the top and thinner at the bottom of high aspect ratio features, which pre-compensates for the expected non-uniform oxidation. During subsequent thermal oxidation, the oxygen radicals consume the non-conformal oxide layer first, allowing uniform thermal oxide growth underneath and resulting in a conformal final oxide layer thickness.
2Reliability
If oxide layer is grown by conventional deposition, then oxide layer is formed, but the oxide layer contains defects and traps leading to reduced device reliability
Solution Approach 1:
A non-conformal oxide layer is deposited using physical vapor deposition or chemical vapor deposition as a preliminary step. This deposited layer serves as a sacrificial layer that will be consumed during thermal oxidation, enabling the subsequent growth of high-quality thermal oxide without the defects and traps inherent in directly deposited oxide layers.
Solution Approach 2:
The non-conformal deposited oxide layer acts as an intermediary medium. It is first deposited to enable subsequent thermal oxidation, then selectively removed after serving its purpose of facilitating uniform thermal oxide growth. This intermediary layer allows the process to achieve both uniform thickness and high oxide quality.
3Manufacturing precision
If non-conformal oxide layer is formed and thermal oxidation is performed, then bottom thick oxide layer is grown, but the non-conformal oxide layer must be selectively removed
Solution Approach 1:
The non-conformal oxide layer is deposited with spatially varying thickness - thicker at the top and thinner at the bottom of high aspect ratio features. This local variation in layer thickness is designed to compensate for the expected non-uniform oxidation, enabling uniform final oxide thickness after the deposited layer is consumed and removed.
Solution Approach 2:
The process utilizes changes in material properties and process parameters. The non-conformal oxide layer has different etch selectivity compared to the thermal oxide layer, enabling selective removal. The thermal oxidation process parameters (temperature, time, oxygen flow) are optimized to grow uniform oxide underneath the non-conformal layer while minimizing damage to the underlying 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 enables the formation of a bottom thick oxide layer with improved quality and reliability, addressing the challenges of uneven oxidation and defect-prone deposited oxide layers, while maintaining the thermal budget and enhancing the oxidation rate at the bottom of high aspect ratio features.
Implementation Method 1
performing an oxidation process to oxidize the substrate and grow a thermal oxide layer underneath the non-conformal oxide layer
Implementation Method 2
performing a wet etching process to selectively remove the non-conformal oxide layer and expose an oxidized portion of the substrate
Data Source
AI summary
The present disclosure generally relate to semiconductor device fabrication, and more particularly, to methods of forming a bottom thick oxide layer in a high aspect ratio semiconductor structures. In certain embodiments, the method includes depositing a non-conformal oxide layer on in a feature on a substrate, performing an oxidation process to thermally grow an oxide layer beneath the deposited non-conformal oxide layer in the feature, and selectively stripping the non-conformal oxide layer to expose the thermally grown oxide layer.