3D NAND Etching via Out-of-Phase Inductive RF Coils
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Solution Overview
Problem
Conventional etch methods for forming three-dimensional NAND structures result in non-uniform features across the substrate, leading to undesirable device defects such as low operability or failure.
Innovation Solution
A method involving a substrate with alternating nitride and oxide layers or polycrystalline silicon and oxide layers, using a photoresist layer, and a process gas comprising sulfur hexafluoride (SF6) and oxygen (O2) with RF power applied to inductive RF coils out of phase, to form a plasma and etch features uniformly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etch methods are used to form features in three dimensional devices, then the etching process can be completed, but non-uniformity in etched features across the substrate surface occurs causing device defects
Solution Approach 1:
The patent applies parameter changes by utilizing dual inductive RF coils with out-of-phase currents to modify the plasma distribution parameters across the substrate. This creates a more uniform plasma density and ion flux distribution, resulting in uniform etching rates across the entire substrate surface, thereby resolving the non-uniformity issue in conventional single-coil systems
Solution Approach 2:
The patent introduces an intermediary mechanism by using two inductive RF coils as mediators to control plasma generation. The coils act as intermediaries between the power source and the substrate, with their out-of-phase currents creating a balanced plasma environment that ensures uniform etching across the substrate surface
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
The method enhances the uniformity of etched features, improving the operability and reliability of three-dimensional NAND structures by maintaining consistent etching across the substrate.
Implementation Method 1
providing an RF power of about 4 kW to about 6 kW to a first inductive RF coil and a second inductive RF coil disposed proximate the process chamber to ignite the process gas to form a plasma
Implementation Method 2
etching through a desired number of the alternating nitride layers and oxide layers or alternating polycrystalline silicon consisting layers and oxide layers to form a feature
Data Source
AI summary
In some embodiments, methods for forming a three dimensional NAND structure include providing to a process chamber a substrate having alternating nitride layers and oxide layers or alternating polycrystalline silicon consisting layers and oxide layers formed atop the substrate and a photoresist layer formed atop the alternating layers; etching the photoresist layer to expose at least a portion of the alternating layers; providing a process gas comprising sulfur hexafluoride and oxygen to the process chamber; providing RF power of about 4 kW to about 6 kW to a first inductive RF coil and a second inductive RF coil disposed proximate the process chamber to ignite the process gas to form a plasma, wherein a current flowing through the first inductive RF coil is out of phase with RF current flowing through the second inductive RF coil; and etching through a desired number of the alternating layers to form a feature.