Inductively Coupled Plasma Ammonium Fluoride Etching
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Solution Overview
Problem
Current semiconductor surface interface engineering methods, such as remote plasma processes, are inadequate for sub-10 nm node devices due to insufficient ion species reaching the substrate, leading to inefficient native oxide removal and surface modification, resulting in rough interfaces and yield drops.
Innovation Solution
The method involves generating an inductively coupled plasma from a mixture of ammonia (NH3) and nitrogen trifluoride (NF3) gases to form ammonium fluoride (NH4F) ions, which selectively etch silicon oxide layers on a substrate, improving surface smoothness and interface quality by allowing ion species to directly interact with the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If remote plasma process is used for oxide removal, then selective SiO2/Si removal is achieved, but ion species cannot reach the substrate effectively, resulting in insufficient surface modification and rough interfaces
Solution Approach 1:
The patent replaces the remote plasma mechanism with inductively coupled plasma (ICP), substituting a low-energy, non-direct ion delivery system with a high-energy, direct ion delivery system. The ICP source generates high-density ion species that are directly delivered to the substrate surface, enabling both effective oxide removal and surface morphology modification simultaneously.
Solution Approach 2:
The patent changes the plasma generation parameters by using inductive coupling instead of remote plasma, which fundamentally alters the ion energy, density, and delivery mechanism. This parameter change enables ions to reach the substrate with sufficient energy to modify surface morphology while maintaining selective oxide removal capability.
2Manufacturing precision
If remote plasma process is used, then some oxide removal is achieved, but the process is isotropic and strongly dependent on geometric receiving angle, causing more removal at feature top than bottom
Solution Approach 1:
The patent replaces the isotropic remote plasma process with anisotropic inductively coupled plasma, which provides directional ion bombardment. The direct ion delivery mechanism inherent in ICP naturally provides better directionality and reduced geometric angle dependence, enabling uniform oxide removal across feature tops and bottoms.
3Reliability
If NH4F is used for selective oxide removal, then SiO2/Si selectivity is achieved, but substantial amounts of true silicon oxide are removed, causing device shorting and yield drop
Solution Approach 1:
The patent replaces the chemical reaction-based remote plasma process with a physical ion bombardment-based inductively coupled plasma process. The high-energy ions directly sputter and remove oxide through physical momentum transfer rather than chemical reaction, enabling precise control over removal depth and preventing over-etching of the protective SiO2 liner.
Solution Approach 2:
The patent performs preliminary surface preparation through direct ion bombardment that removes contaminants and modifies surface morphology before the selective oxide removal step. This preliminary action creates a cleaner, smoother surface that enables more controlled and selective subsequent processing, reducing the need for aggressive chemistry that could damage protective layers.
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 selective and efficient removal of silicon oxide, enhancing surface smoothness and interface quality, reducing silicon loss, and improving device performance by allowing precise control over etch directionality and selectivity, particularly in small features like sub-10 nm nodes.
Implementation Method 1
generating an ion species from an inductively coupled plasma formed within the processing volume of the processing chamber from a first process gas
Implementation Method 2
exposing a first layer of the substrate to the ion species to form an ammonium fluoride (NH4F) film atop the first layer
Implementation Method 3
heating the substrate to a second temperature at which the ammonium fluoride film reacts with the first layer to selectively etch the silicon oxide
Implementation Method 4
heating the substrate to a second temperature at which the ammonium fluoride film reacts with the first layer
Data Source
AI summary
Methods for surface interface engineering in semiconductor fabrication are provided herein. In some embodiments, a method of processing a substrate disposed atop a substrate support in a processing volume of a processing chamber includes: generating an ion species from an inductively coupled plasma formed within the processing volume of the processing chamber from a first process gas; exposing a first layer of the substrate to the ion species to form an ammonium fluoride (NH4F) film atop the first layer, wherein the first layer comprises silicon oxide; and heating the substrate to a second temperature at which the ammonium fluoride film reacts with the first layer to selectively etch the silicon oxide.