Oxide Layer Etching for Semiconductor Gate Reliability
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Solution Overview
Problem
The quality of the gate oxide layer in semiconductor devices is critical for their performance and reliability, but defects in this layer can lead to lower yield and performance due to the high integration of semiconductor chips, especially when the surface is damaged during the formation of well regions by ion implantation.
Innovation Solution
A method is developed to form a semiconductor structure by increasing the thickness of the oxide layer, followed by etching a specific thickness to remove defects, and then forming a polysilicon gate on the oxide layer, which includes forming an oxide layer, a sacrificial layer, trenches, isolation structures, and well regions, with precise etching using a dilute hydrofluoric acid solution to enhance the oxide layer's quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ion implantation is used to form well regions, then well regions are formed in the semiconductor substrate, but the oxide layer surface is damaged and defects are caused
Solution Approach 1:
The patent applies preliminary action by forming a thicker oxide layer (first thickness) before ion implantation occurs. This pre-formed thick oxide layer serves as a protective buffer that absorbs the damage from ion implantation, preventing direct damage to the final gate oxide layer. After ion implantation, a portion of this preliminary oxide layer is removed through etching, revealing a high-quality oxide layer surface that was not exposed to ion damage.
2Reliability
If a thicker oxide layer is formed, then the oxide layer can protect against ion implantation damage, but the oxide layer thickness is excessive and may cause penetration
Solution Approach 1:
The patent segments the oxide layer formation process into two distinct stages: first, a thick oxide layer (first thickness) is formed to provide protection during ion implantation; second, after ion implantation, a portion of this oxide layer is removed through etching to achieve the final required thickness (second thickness). This segmentation allows the oxide layer to serve different functions at different times - protection during implantation and precise thickness control for final device performance.
3Reliability
If the oxide layer thickness is increased, then ion implantation damage is prevented, but the etching process complexity increases
Solution Approach 1:
The patent applies parameter changes by carefully controlling the etching process parameters, including using a dilute hydrofluoric acid solution with specific concentration ratios (1:300 to 1:400) and controlling etching time (300s to 400s). These precise parameter controls enable selective removal of the excess oxide layer while preserving the underlying structure and achieving the desired final thickness without requiring overly complex multi-step etching 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 method improves the reliability of semiconductor devices by effectively removing defects from the oxide layer, ensuring a consistent thickness and preventing penetration, thereby enhancing the performance and yield of semiconductor devices.
Implementation Method 1
Etching part of the oxide layer, so that the thickness of the oxide layer is a second thickness
Implementation Method 2
When a first well region and a second well region are formed in a substrate in the manner of ion implantation
Data Source
AI summary
The present disclosure provides a semiconductor structure and a manufacturing method thereof. The method includes: preparing a semiconductor substrate; sequentially forming an oxide layer and a sacrificial layer on the semiconductor substrate, the thickness of the oxide layer is a first thickness; forming a plurality of trenches in the semiconductor substrate, wherein the trenches extending from the sacrificial layer into the semiconductor substrate; forming an isolation dielectric layer on the plurality of trenches and the sacrificial layer, and removing the isolation dielectric layer on the sacrificial layer to form a plurality of isolation structures; forming a well region in the semiconductor substrate; processing the oxide layer by an etching process, so that the thickness of the oxide layer is equal to a second thickness, the first thickness is greater than the second thickness; and forming a polysilicon gate on the etched oxide layer.