Shallow Trench Structure Etching to Reduce STI Substrate Damage
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Solution Overview
Problem
Traditional shallow trench isolation (STI) technology causes damage to the substrate during lateral etching due to reliance on wet etching methods, which is not suitable for deep sub-micron semiconductor manufacturing.
Innovation Solution
A method combining wet etching and dry etching to laterally etch the mask layer, where wet etching is used initially to align the second material layer and then dry etching is employed to further refine the first material layer, using a mixed gas of difluoromethane, trifluoromethane, and helium to minimize substrate damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet etching is used for lateral etching of the mask layer, then the etching process is simple and can be performed throughout the entire process, but substrate damage occurs in the shallow trench area
Solution Approach 1:
The lateral etching process is segmented into two distinct stages: first wet etching is applied to the second material layer (silicon oxide), then dry etching is applied to the first material layer (silicon nitride). This segmentation allows each etching method to be optimized for its specific material layer, achieving both process simplicity and substrate protection
Solution Approach 2:
Different etching methods are applied to different material layers based on their specific properties. Wet etching is used for the silicon oxide layer where it provides effective removal without damage, while dry etching is used for the silicon nitride layer where it prevents substrate damage. This local optimization of etching methodology resolves the contradiction between process simplicity and substrate protection
2Ease of manufacture
If traditional wet etching is used for mask layer lateral etching, then the process is cost-effective and simple, but the lateral wall alignment precision is insufficient
Solution Approach 1:
The etching process is divided into two sequential steps with different methodologies. The first wet etching step establishes the basic lateral etching, and the second dry etching step refines the lateral wall alignment. This segmented approach achieves both cost-effectiveness and high precision
Solution Approach 2:
Wet etching is performed first as a preliminary action to remove the silicon oxide layer and establish the initial lateral etching profile. This preliminary wet etching prepares the structure for the subsequent dry etching step, which then achieves the precise lateral wall alignment required for deep sub-micron manufacturing
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 substrate damage and is cost-effective by utilizing existing dry etching machines, making it suitable for 28-90 nanometer integrated circuit manufacturing processes.
Implementation Method 1
performing a first lateral etching on the second material layer from the shallow trench to both sides by using wet etching
Implementation Method 2
performing a second lateral etching on the first material layer from the shallow trench to both sides by using dry etching
Data Source
AI summary
The present disclosure provides a method for making a shallow trench structure, which at least includes the following: preparing a substrate; forming a first material layer on one side of the substrate; forming a second material layer on the first material layer; forming a shallow trench in the second material layer, the first material layer and the substrate; performing a first lateral etching on the second material layer from the shallow trench to both sides by using wet etching; performing a second lateral etching on the first material layer from the shallow trench to both sides by using dry etching. The present disclosure solves the problem of the damage to the silicon in the shallow trench caused by the traditional lateral etching technology.