Silicon Nitride Plasma Etching with F/H Ratio Profile Control
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Solution Overview
Problem
Existing methods for etching silicon nitride layers in semiconductor manufacturing face challenges in achieving high selectivity over silicon oxide layers, particularly due to issues with wet etching and the limitations of dry etching gases that either result in polymer film formation or inadequate etching selectivity.
Innovation Solution
A substrate processing method involving plasma etching using a gas mixture containing fluorine and hydrogen, with an atomic ratio of fluorine to hydrogen controlled between 15:1 and 35:1, to selectively etch silicon nitride layers while adjusting the etch profile in the thickness direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet etching using phosphoric acid-based etchant is used to etch silicon nitride film, then high etching selectivity is achieved, but the etchant penetrates into the device pattern due to surface tension and etching is not properly performed to the lowermost nitride layer
Solution Approach 1:
The patent replaces wet etching (liquid-based) with dry etching (gas-based plasma process). This substitution eliminates surface tension issues that cause etchant penetration and incomplete etching, while maintaining high etching selectivity through controlled plasma reactions with silicon nitride film.
Solution Approach 2:
The patent changes the etching process parameters by using plasma state gas instead of liquid etchant. This parameter change allows the etching process to reach the lowermost nitride layer completely while maintaining high selectivity, as plasma can penetrate patterns more effectively without surface tension constraints.
2Productivity
If hydrogen-containing etching gases such as monofluoromethane and difluoromethane are used for silicon nitride dry etching, then etching process is enabled, but a thick polymer film is produced which lowers the etch rate
Solution Approach 1:
The patent optimizes the composition parameters of the etching gas by using a mixed gas system with specific ratios of CF4 (20-80 sccm), CH2F2 (0-100 sccm), and H2 (0-50 sccm). This parameter optimization balances polymer film formation and etch rate, achieving both high productivity and reduced harmful effects.
Solution Approach 2:
The patent uses a composite gas mixture instead of single gas etching. The combination of CF4, CH2F2, and H2 creates a synergistic effect where the mixed plasma provides both sufficient etch rate and controlled polymer film formation, resolving the contradiction between productivity and harmful byproducts.
3Object-generated harmful factors
If only etching gas containing no hydrogen is used to suppress polymer film formation, then polymer film is reduced, but etching selectivity of silicon nitride film with respect to silicon oxide film is not high and silicon oxide film is also etched
Solution Approach 1:
The patent carefully controls the hydrogen content parameter in the etching gas mixture, maintaining H2 flow rate at 0-50 sccm. This parameter control allows sufficient polymer film suppression while preserving high etching selectivity between silicon nitride and silicon oxide films through optimized plasma chemistry.
Solution Approach 2:
The patent employs a composite gas system where CF4 provides fluorine radicals for etching, CH2F2 contributes to polymer film control, and H2 fine-tunes the plasma characteristics. This composite approach achieves both low polymer film formation and high etching selectivity simultaneously.
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 enables selective etching of silicon nitride layers with respect to silicon oxide layers, while also controlling the etch profile, thereby improving the efficiency and accuracy of semiconductor manufacturing processes.
Implementation Method 1
plasma etching the silicon nitride layers using plasma of a plurality of gases
Implementation Method 2
the silicon nitride film is etched using etching radicals generated therefrom
Implementation Method 3
an RF power source may apply power having a predetermined RF frequency to the shower head to form plasma inside the shower head
Implementation Method 4
Transform Electrical Energy to Electromagnetic Energy
Data Source
AI summary
The present invention relates to a substrate processing method for selectively etching a silicon nitride layer on a substrate on which silicon oxide layers and silicon nitride layers are alternately stacked, the method including plasma etching the silicon nitride layers using plasma of a plurality of gases, wherein the plurality of gases include a first gas containing fluorine excluding nitrogen trifluoride (NF3) and a second gas containing hydrogen, and the etch profile in the thickness direction of the silicon nitride layers is controlled by adjusting the atomic ratio of fluorine to hydrogen included in the plurality of gases.