SOI Substrate Etching Using Fluorocarbon Gas and Oxygen Plasma
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Solution Overview
Problem
Current semiconductor device manufacturing using SOI substrates faces challenges in achieving reliable element isolation and transistor formation due to issues with etching processes, leading to inconsistencies and potential reliability problems.
Innovation Solution
A method involving the use of a fluorocarbon gas for dry etching, followed by oxygen plasma treatment, to control the etching thickness of the element isolation portion and prevent semiconductor layer exposure, ensuring consistent step differences and reducing etch residues, thereby enhancing the manufacturing process and device reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etching processes are used to form element isolation portions, then manufacturing process simplicity is maintained, but etch residues remain and semiconductor layer exposure occurs leading to reliability issues
Solution Approach 1:
The etching process is divided into multiple sequential steps: first dry etching to remove the first insulating film, oxygen plasma treatment to prevent semiconductor layer exposure, and second dry etching to remove remaining insulating material. This segmentation allows each step to be optimized for its specific function, eliminating etch residues while preventing semiconductor layer exposure.
Solution Approach 2:
Oxygen plasma treatment is performed as a preliminary action between the first and second dry etching steps. This preliminary treatment modifies the surface of the element isolation portion to prevent semiconductor layer exposure during subsequent etching, thereby improving reliability without requiring complex process changes.
2Reliability
If the etching thickness of the element isolation portion is increased to prevent semiconductor layer exposure, then reliability improves, but step differences become inconsistent and manufacturing precision decreases
Solution Approach 1:
The total etching thickness is divided into two controlled portions: the first dry etching removes a controlled thickness of the first insulating film, and the second dry etching removes the remaining insulating material. This segmentation ensures consistent step differences while preventing semiconductor layer exposure, thereby maintaining both reliability and manufacturing precision.
Solution Approach 2:
The etching parameters are optimized and controlled at each step: the first dry etching uses specific parameters to remove the first insulating film to a controlled thickness, and the second dry etching uses adjusted parameters to remove remaining material without exposing the semiconductor layer. This parameter control ensures consistent step differences while maintaining reliability.
3Manufacturing precision
If multiple etching steps are implemented to remove etch residues, then manufacturing precision improves, but process time increases reducing productivity
Solution Approach 1:
The multiple etching steps are performed continuously without interrupting the manufacturing flow. The first dry etching, oxygen plasma treatment, and second dry etching are executed in sequence as part of the standard manufacturing process, eliminating the need for additional post-etching cleaning steps and maintaining high productivity while achieving precise etch residue removal.
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 improves the reliability of semiconductor devices by minimizing etch residues and maintaining the semiconductor layer integrity, ensuring consistent step differences and improved manufacturing yield.
Implementation Method 1
The first dry etching uses a first gas containing a fluorocarbon gas
Implementation Method 2
after the step (c), subjecting the substrate to oxygen plasma treatment
Data Source
AI summary
A substrate including an insulating layer, a semiconductor layer, and an insulating film stacked on a semiconductor substrate and having a trench filled with an element isolation portion is provided. After removal of the insulating film from a bulk region by a first dry etching, the semiconductor layer is removed from the bulk region by a second dry etching. Then, the insulating film in an SOI region and the insulating layer in the bulk region are removed. A gas containing a fluorocarbon gas is used for first dry etching. The etching thickness of the element isolation portion by a first dry etching is at least equal to the sum of the thicknesses of the insulating film just before starting the first dry etching and the semiconductor layer just before starting the first dry etching. After first dry etching and before second dry etching, oxygen plasma treatment is performed.