Fluorohydrocarbon Polymer Nitride Etch Selectivity
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Solution Overview
Problem
Existing silicon nitride etch processes lack high selectivity to silicon and silicon oxide, especially at the nanoscale, leading to poor performance in semiconductor manufacturing, such as recess formation and excessive etching in spacer and trench silicide modules.
Innovation Solution
An anisotropic silicon nitride etch process using a fluorohydrocarbon-containing plasma forms distinct polymers on silicon and silicon oxide surfaces, preventing etching of silicon while allowing selective etching of silicon nitride, with the polymers' thicknesses varying to control the etch rates and achieve high selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional silicon nitride etch process using CH3F and O2 gases is employed, then etching of silicon nitride is achieved, but selectivity to silicon deteriorates due to significant silicon consumption for oxide conversion at nanoscale
Solution Approach 1:
A fluorocarbon-containing polymer is introduced as an intermediary protective layer on silicon surfaces. This polymer acts as a mediator that prevents direct interaction between the plasma and silicon, reducing silicon consumption while maintaining etch selectivity. The polymer deposits on silicon surfaces and serves as a protective barrier during the etch process.
Solution Approach 2:
The etch process parameters are changed by using a fluorohydrocarbon-containing plasma instead of conventional CH3F and O2 gases. This parameter change modifies the chemical reactions at the surface, enabling polymer formation that protects silicon while allowing selective etching of silicon nitride.
2Manufacturing precision
If conventional silicon nitride etch process is used, then etching is achieved, but selectivity to silicon oxide deteriorates causing excessive etching and recess formation
Solution Approach 1:
The fluorocarbon-containing polymer serves as an intermediary layer on silicon oxide surfaces, controlling the etch rate by modulating plasma-surface interactions. This polymer layer prevents excessive etching and recess formation by providing a protective effect while still allowing controlled removal of silicon nitride.
Solution Approach 2:
The process creates a protective polymer copy layer on the surface that replicates the protective function needed. This polymer layer copies the protective role that would otherwise require thick oxide layers, enabling protection at the nanoscale where material consumption must be minimized.
3Manufacturing precision
If single carbon CHxFy gases are used, then fluorohydrocarbon plasma provides selectivity to silicon oxide, but selectivity to silicon relies on oxide conversion which consumes significant silicon at nanoscale
Solution Approach 1:
The fluorocarbon-containing polymer acts as an intermediary that provides silicon protection without requiring oxide conversion. This mediator layer forms directly on silicon surfaces and provides the needed protection, eliminating the need to convert silicon to oxide and thereby reducing silicon consumption.
Solution Approach 2:
The chemical mechanism of oxide conversion is replaced by a polymer deposition mechanism. Instead of converting silicon to silicon oxide through chemical reactions, the process uses polymer deposition to create a protective layer, substituting one mechanical/chemical system for another more efficient system.
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 process provides high selectivity to silicon nitride relative to silicon and silicon oxide, enabling precise etching with reduced plasma damage and improved control over recess depths, even at small dimensions below 50 nm.
Implementation Method 1
a first fluorohydrocarbon-containing polymer having a first thickness is formed on the silicon portion, a second fluorohydrocarbon-containing polymer having a second thickness is formed on the silicon oxide portion, and a third fluorohydrocarbon-containing polymer having a third thickness is formed on the silicon nitride portion
Implementation Method 2
The fluorohydrocarbon-containing polymer interacts with silicon nitride to form a volatile compound, thereby enabling etching of silicon nitride
Implementation Method 3
anisotropically etching the silicon nitride portion employing a fluorohydrocarbon-containing plasma
Data Source
AI summary
An anisotropic silicon nitride etch provides selectivity to silicon and silicon oxide by forming a fluorohydrocarbon-containing polymer on silicon surfaces and silicon oxide surfaces. Selective fluorohydrocarbon deposition is employed to provide selectivity to non-nitride surfaces. The fluorohydrocarbon-containing polymer interacts with silicon nitride to form a volatile compound, thereby enabling etching of silicon nitride. The fluorohydrocarbon-containing polymer interacts with silicon oxide at a low reaction rate, retarding, or completely stopping, the etching of silicon oxide. The fluorohydrocarbon-containing polymer does not interact with silicon, and protects silicon from the plasma. The anisotropic silicon nitride etch can be employed to etch silicon nitride selective to silicon and silicon oxide in any dimension, including small dimensions less than 50 nm.