Polysilicon Etching in FinFETs Using HBr-Cl2 Plasma
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Solution Overview
Problem
In semiconductor device manufacturing, particularly for fin-type field effect transistors, there is a challenge in effectively removing a polycrystalline silicon layer without damaging underlying metal layers during the etching process, as existing methods often leave residues or cause damage to the metal layers.
Innovation Solution
A semiconductor device manufacturing method involving a processing gas mixture of HBr and Cl2 gases, with Cl2 flow rates between 5% and 10% of HBr, excited at high pressures within a plasma processing chamber, along with the use of an organic mask and specific plasma etching processes to minimize residue and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a polycrystalline silicon layer is etched by exciting a mixed gas containing HBr gas, Cl2 gas, and Ar gas, then the polycrystalline silicon layer can be removed, but the metal layer may be damaged by the etching process
Solution Approach 1:
The patent changes the chemical composition parameters of the processing gas by incorporating Cl2 gas at a specific flow rate ratio (5-10% relative to HBr gas). This parameter modification enables the etching process to achieve complete removal of polycrystalline silicon while the controlled concentration of Cl2 prevents excessive damage to the underlying metal layer, thus resolving the contradiction between etching precision and metal layer protection
2Manufacturing precision
If the Cl2 gas flow rate is increased to improve etching completeness, then polycrystalline silicon removal is enhanced, but damage to the metal layer increases
Solution Approach 1:
The patent establishes an optimal parameter range for Cl2 gas flow rate (5-10% of HBr gas flow rate) that balances two competing requirements: sufficient Cl2 concentration to ensure complete polycrystalline silicon removal, and limited Cl2 concentration to prevent excessive metal layer damage. This precise parameter control resolves the contradiction between removal completeness and damage prevention
3Manufacturing precision
If the polycrystalline silicon layer is etched in fine gaps between adjacent fin regions, then the silicon can be removed from tight spaces, but residues may remain in the gap regions
Solution Approach 1:
The addition of Cl2 gas to the processing mixture changes the chemical reaction characteristics, forming reaction products that do not remain as residues in the fine gap regions. The specific Cl2 concentration (5-10% of HBr flow rate) ensures complete silicon removal from tight spaces while the reaction chemistry prevents residue formation, resolving the contradiction between gap etching completeness and residue prevention
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 method effectively suppresses the polycrystalline silicon layer from being left in unwanted regions and reduces damage to the metal layer, ensuring precise etching with minimal residue and damage, even in complex pattern formations.
Implementation Method 1
exciting a processing gas containing a HBr gas and a Cl2 gas within a processing chamber
Data Source
AI summary
A semiconductor device manufacturing method includes exciting a processing gas containing a HBr gas and a Cl2 gas within a processing chamber that accommodates a target object including a substrate, regions made of silicon, which are protruded from the substrate and arranged to form a gap, a metal layer formed to cover the regions, a polycrystalline silicon layer formed on the metal layer, and an organic mask formed on the polycrystalline silicon layer. The Cl2 gas is supplied at a flow rate of about 5% or more to about 10% or less with respect to a flow rate of the HBr gas in the processing gas.