Electron-Stimulated Silicon Etching for Selective Anisotropic Profiles
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Solution Overview
Problem
Conventional etching techniques, such as reactive ion etching and electron beam etching with chlorine-based chemistries, face challenges in achieving selectivity and anisotropic etching of complex semiconductor structures, leading to issues like corner residues and tapered profiles, especially at advanced technology nodes.
Innovation Solution
A method involving physisorption of a fluorine etchant on a silicon substrate, followed by electron-impact dissociation to release atomic fluorine for etching, which includes forming a fluorine-containing reaction layer and irradiating it with electrons to etch the substrate, with optional purging steps to enhance control and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional reactive ion etching (RIE) is used to achieve anisotropic etching profiles, then anisotropic etching is possible, but ion energy thresholds reduce etch selectivity and may damage the structure being etched
Solution Approach 1:
The patent replaces ion bombardment (mechanical/physical process) with electron beam irradiation (electromagnetic radiation process) to activate the etching chemistry. This substitution eliminates the need for high ion energy thresholds that damage structures while maintaining anisotropic etching capability through the directional electron beam and physisorbed fluorocarbon layer
Solution Approach 2:
The patent introduces a fluorocarbon-containing reaction layer as an intermediary between the electron beam and the silicon substrate. This intermediate layer physisorbs onto the substrate surface and, when irradiated by electrons, releases atomic fluorine that performs the etching, thereby decoupling the need for high ion energy from the etching process and improving selectivity
2Productivity
If chlorine-based chemistries are used with ion bombardment for silicon etching, then etching can be achieved, but very tight control of ion energy is required to achieve selectivity
Solution Approach 1:
The patent replaces the complex ion energy control mechanism with a simpler electron beam irradiation system. Electrons are used to activate the physisorbed fluorocarbon layer, eliminating the need for precise ion energy control while maintaining effective silicon etching capability
Solution Approach 2:
The patent changes the fundamental activation mechanism from ion bombardment to electron irradiation. This parameter change shifts the process from requiring tight control of ion energy to using electron beam parameters (energy, flux, duration) to activate the fluorocarbon layer, thereby simplifying the control requirements
3Productivity
If conventional etching processes are used for narrow structures less than 10 nm, then etching can proceed, but clogging occurs which reduces accessibility of corners resulting in corner residues
Solution Approach 1:
The patent replaces ion bombardment with electron beam irradiation, which does not require high energy thresholds and can effectively activate etching in narrow, high aspect ratio structures without causing the clogging and corner residue issues associated with conventional ion-based processes
Solution Approach 2:
The physisorbed fluorocarbon-containing reaction layer acts as an intermediary that enables uniform fluorine release throughout the structure, including in narrow corners and high aspect ratio features, preventing the clogging issues that occur with direct ion bombardment approaches
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 achieves high selectivity and anisotropic etching of silicon relative to silicon oxide and silicon nitride, reduces byproduct redeposition, and increases etch rate, while avoiding tight control of ion energy thresholds.
Implementation Method 1
irradiating the layer of the fluorine-containing reaction layer on the surface of the substrate with electrons having an energy sufficient to cause electron-impact dissociation of the fluorine-containing reaction layer thereby releasing atomic fluorine
Implementation Method 2
contacting the substrate comprising silicon in a processing chamber with a fluorine etchant at a substrate temperature, pressure, and for a period of time sufficient to form a fluorine-containing reaction layer on a surface of the substrate
Data Source
AI summary
Methods and apparatus for processing a substrate which include contacting the substrate comprising silicon in a processing chamber with a fluorine etchant at a substrate temperature, pressure, and for a period of time sufficient to form a fluorine-containing reaction layer on a surface of the substrate and irradiating the fluorine-containing reaction layer on the surface of the substrate with electrons having an energy sufficient for electron-impact dissociation thereby releasing atomic fluorine to etch the surface of the substrate.