Isotropic Silicon Oxide Etching via Fluorocarbon-Oxygen Plasma Segmentation
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Solution Overview
Problem
Current plasma etching techniques are not suitable for isotropic etching of silicon oxide, particularly for advanced semiconductor structures like nanosheet FETs, as they rely on chemical oxide removal methods that are less desirable due to shrinking geometries and evolving structure types, and existing atomic layer etch techniques are not effective for isotropic etching.
Innovation Solution
A two-step plasma process using a fluorocarbon-based plasma followed by an oxygen plasma, with minimal low-frequency bias power and high pressures, to form and remove a fluorocarbon film on silicon oxide, promoting isotropic etching by minimizing ion bombardment and anisotropic mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching techniques are used, then anisotropic etching is achieved, but isotropic etching of silicon oxide cannot be obtained
Solution Approach 1:
The etching process is segmented into two distinct steps: (1) fluorocarbon-based plasma treatment to modify the silicon oxide surface and form a fluorocarbon-containing layer, and (2) oxygen plasma treatment to remove the modified layer. This segmentation allows each step to be optimized independently, achieving isotropic etching that conventional single-step plasma processes cannot provide.
Solution Approach 2:
The invention changes the chemical parameters by alternating between fluorocarbon-based plasma and oxygen plasma. The fluorocarbon plasma introduces carbon and fluorine species that modify the oxide surface, while the oxygen plasma removes these species. This parameter change enables isotropic etching behavior by controlling the chemical reactions at the etch front.
2Manufacturing precision
If chemical oxide removal (COR) is used for isotropic etching, then isotropic etching is achieved, but the technique becomes less desirable for shrinking geometries and advanced structures
Solution Approach 1:
The invention replaces the purely chemical oxide removal mechanism with a plasma-based process that uses controlled chemical reactions followed by physical removal. The two-step plasma process substitutes the conventional COR chemistry with a more controllable plasma chemistry that maintains isotropic etching while being compatible with advanced semiconductor structures and smaller geometries.
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 process achieves isotropic etching of silicon oxide with equal lateral and horizontal etching rates, suitable for various substrate process steps such as oxide spacer etches, fin reveal, and oxide liner etches, improving the precision and control in semiconductor processing.
Implementation Method 1
a first step (a modification step) includes the use of a fluorocarbon based plasma... This modification step provides for the formation of an interface layer and the deposition of a fluorocarbon film on the surface of the silicon oxide
Implementation Method 2
a second step (a removal step) includes the use of an oxygen (O2) based plasma. This removal step removes the fluorocarbon film and the interface layer
Implementation Method 3
Method of isotropic etching of silicon oxide utilizing fluorocarbon chemistry
Data Source
AI summary
An isotropic plasma etch process for etching silicon oxide is provided. In an embodiment, a first step, a modification step, includes the use of a fluorocarbon based plasma. This modification step provides for the formation of an interface layer and the deposition of a fluorocarbon film on the surface of the silicon oxide. Then, a second step, a removal step includes the use of an oxygen (O2) based plasma. This removal step removes the fluorocarbon film and the interface layer. To promote isotropic etching, the plasma process is performed with little or no low frequency bias power applied to the system. Thus, ion attraction to the substrate is minimized by providing no low frequency power. Further, relatively high pressures are maintained so as to further promote isotropic behavior.