Selective Silicon Nitride Etch Using Ozone Passivation
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Solution Overview
Problem
In semiconductor processing, achieving selective etching of silicon nitride over silicon with high selectivity is challenging due to the continuous scaling down of device dimensions, requiring advanced methods to maintain material integrity and reduce silicon recess in devices like 3D NAND memory and miniaturized transistors.
Innovation Solution
The method involves introducing ozone gas into a processing chamber, where it reacts with the silicon surface to form a passivating oxide layer, followed by plasma-induced etching with fluorine-containing gases, which selectively etches the silicon nitride layer more than the silicon layer, enhancing the etch selectivity ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching is used to remove silicon nitride, then the silicon nitride layer can be etched, but the silicon layer is also etched simultaneously resulting in low selectivity and silicon recess
Solution Approach 1:
The patent applies preliminary action by exposing the silicon surface to ozone gas before the plasma etching process. This pre-treatment forms a passivating oxide layer on the silicon surface that protects it during subsequent etching, enabling selective removal of silicon nitride while preventing silicon recess
Solution Approach 2:
The patent uses ozone gas as a strong oxidant to rapidly form a dense oxide layer on the silicon surface. This accelerated oxidation creates a protective barrier that significantly reduces silicon etching rates during the plasma process, achieving high selectivity for silicon nitride removal
2Productivity
If device dimensions are scaled down to advance semiconductor nodes, then device performance is improved, but maintaining material integrity and achieving high selectivity becomes increasingly difficult
Solution Approach 1:
The patent changes the chemical parameters of the etching process by introducing ozone gas, which fundamentally alters the surface chemistry of silicon. This parameter change enables high selectivity and maintains material integrity even as device dimensions scale down to advanced nodes
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 significantly improves the selectivity of silicon nitride etch over silicon, maintaining silicon substrate integrity and reducing silicon recess, thereby enhancing the performance and reliability of semiconductor devices by achieving an etch rate ratio greater than 90 for silicon nitride to silicon.
Implementation Method 1
introducing ozone gas into a processing chamber, where it reacts with the silicon surface to form a passivating oxide layer
Implementation Method 2
followed by plasma-induced etching with fluorine-containing gases, which selectively etches the silicon nitride layer more than the silicon layer
Data Source
AI summary
Apparatus, systems, and methods for processing a workpiece are provided. In one example implementation, the workpiece can include a silicon nitride layer and a silicon layer. The method can include admitting an ozone gas into a processing chamber. The method can include exposing the workpiece to the ozone gas. The method can include generating one or more species from a process gas using a plasma induced in a plasma chamber. The method can include filtering the one or more species to create a filtered mixture. The method can further include exposing the workpiece to the filtered mixture in the processing chamber such that the filtered mixture at least partially etches the silicon nitride layer more than the silicon layer. Due to ozone gas reacting with surface of silicon layer prior to etching process with fluorine-containing gas, selective silicon nitride etch over silicon can be largely promoted.