3D Dielectric Layer Etching With Vertex Protection
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Solution Overview
Problem
Current methods for etching dielectric layers on 3D microelectronic structures, such as FinFET transistors, face challenges in precision and damage control, leading to material loss and structural damage during the formation of spacers.
Innovation Solution
A method involving sequential plasma etchings with fluorine-based chemistry, forming protective oxide layers to prevent top surface damage, and carefully controlled etching to remove dielectric layers from sides without affecting the underlying semiconductor material, using an intermediate protective layer to safeguard the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to remove dielectric layer from the sides of 3D structures, then the dielectric layer can be removed, but the top surface of the 3D structure is damaged with material loss (recess) of 1-2 nm
Solution Approach 1:
A protective oxide layer is formed on the top surface of the 3D structure before the etching process begins. This preliminary protective action prevents direct exposure of the top surface to the etching plasma, thereby avoiding material loss and damage while allowing precise etching of the lateral dielectric layer.
Solution Approach 2:
The protective oxide layer acts as an intermediary barrier between the etching plasma and the top surface of the 3D structure. This intermediary layer selectively protects the top surface while permitting the etching of the dielectric material on the sides, enabling precise depth control without direct damage to the underlying structure.
2Manufacturing precision
If etching is extended to completely remove dielectric layer on sides, then complete removal is achieved, but underlying semiconductor material begins to be damaged
Solution Approach 1:
The protective oxide layer is formed in advance on the top surface and extends laterally to cover the underlying semiconductor material. This preliminary protection ensures that when etching proceeds to completely remove the dielectric layer, the semiconductor material remains shielded from plasma damage.
Solution Approach 2:
The protective oxide layer serves as a cushioning barrier that absorbs the impact of the etching process. By being present beforehand, it prevents the etching plasma from directly contacting and damaging the underlying semiconductor material, even when the dielectric layer is completely removed.
3Reliability
If multiple oxidation and etching sequences are repeated to protect the top, then top protection is improved, but the process complexity increases
Solution Approach 1:
The protective oxide layer formation and the etching process are merged into a single integrated sequence. The oxide layer is formed once before etching begins, and then both the protective layer and dielectric material are removed in a coordinated manner, eliminating the need for multiple separate oxidation and etching cycles.
Solution Approach 2:
The protective oxide layer serves multiple functions simultaneously: it protects the top surface during etching, provides a controlled etching front, and can be selectively removed after the dielectric layer is completely gone. This multi-functionality reduces the need for multiple specialized process steps.
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 precise and complete removal of dielectric layers on 3D structures while protecting the underlying semiconductor material, improving the control of etching depth and preventing material loss, thus enhancing the manufacturing process for FinFET transistors.
Implementation Method 1
a first etching of the dielectric layer, by a first plasma based on a chemistry comprising: at least a first compound based on fluorine (F) and oxygen (O)
Implementation Method 2
generate an ion bombardment directed mainly along a direction parallel to said flank
Implementation Method 3
form a first oxide-based protective layer at the top of the three-dimensional structure and form a second oxide-based protective layer on an upper portion of the dielectric layer located on the flank
Data Source
Figure 1~2
Figure 3A~3C
Figure 3D~3E
AI summary
The invention relates to a method for etching a dielectric layer covering a vertex (31) and a flank (32) of a three-dimensional structure, said method comprising: - a first etching of the dielectric layer, comprising: ∘ a first fluorine-based compound (F) ∘ oxygen (O), said first etching being carried out to: ∘ form a first protective layer on the vertex (31) and form a second protective layer on the dielectric layer (14f), - a second etching configured to remove the second protective layer while retaining a portion of the first protective layer, the first and second etchings being repeated until the dielectric layer (14f) located on the flank (32) of the structure (30) is removed. Advantageously, the method comprises, before deposition of the dielectric layer, the formation of an intercalated protective layer (20) between said vertex (31) and the dielectric layer.