Plasma Etching of Silicon Films With Pulsed Bias RF Control
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Solution Overview
Problem
Existing etching processes struggle to suppress shape abnormalities, such as minute roughness on the side wall surfaces of etching patterns, particularly in 3D NAND high aspect ratio contact processes, which are critical for achieving higher stackability and integration in semiconductor devices.
Innovation Solution
A plasma processing method using a capacitively coupled plasma processing apparatus with controlled bias RF power supply and duty ratio, along with specific gas mixtures and periodic application of DC voltage, to enhance ion component control and minimize side wall damage during etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used with lower bias RF power, then the equipment load is reduced, but the vertical components of ions are insufficient causing shape abnormalities and LER on side wall surfaces
Solution Approach 1:
The patent applies periodic action by supplying bias RF power in a pulsed manner rather than continuously. The bias RF power is supplied periodically during the etching process, creating time-varying ion bombardment conditions that reduce charging effects and improve etching uniformity while maintaining acceptable power levels.
Solution Approach 2:
The patent changes the parameter of bias RF power from constant to variable by introducing periodic modulation. This parameter change allows dynamic control of ion energy and flux, enabling optimization of etching profiles and reduction of shape abnormalities without requiring continuously high power levels.
2Manufacturing precision
If higher bias RF power is supplied continuously, then the vertical components of ions increase improving etching precision, but charging effects worsen causing new shape abnormalities
Solution Approach 1:
By periodically modulating the bias RF power rather than applying it continuously, the patent creates cycles of high and low power delivery. This periodic action allows ion bombardment to occur in pulses, reducing cumulative charging effects while still providing sufficient vertical ion components during the active etching phases.
Solution Approach 2:
The patent introduces dynamic control of bias RF power by making it time-dependent through periodic modulation. This dynamic approach allows the system to adapt ion bombardment conditions during the etching process, balancing the need for vertical ion components with the need to minimize charging effects.
3Manufacturing precision
If the etching process is optimized for shape precision, then LER is reduced, but the etching rate and throughput decrease
Solution Approach 1:
The periodic supply of bias RF power creates alternating phases of high ion bombardment (improving etching quality) and lower power phases (allowing relaxation and reducing damage). This temporal modulation enables the process to achieve good etching profiles with acceptable rates by optimizing the duty cycle and frequency of the periodic power supply.
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 effectively reduces line edge roughness and improves the shape consistency of etching patterns, enhancing the quality and integration of semiconductor structures.
Implementation Method 1
etching the silicon-containing film by plasma generated from a processing gas containing a fluorocarbon gas and an oxygen-containing gas
Implementation Method 2
periodically supplying, to the substrate support, bias RF power of 20 kW to 50 kW at a duty ratio of 5% to 50%
Data Source
AI summary
A substrate etching method performed by using a plasma processing apparatus includes: providing a substrate including a silicon-containing film to a substrate support; periodically supplying, to the substrate support, bias RF power of 20 KW to 50 kW at a duty ratio of 5% to 50%; and etching the silicon-containing film by plasma generated from a processing gas containing a fluorocarbon gas and an oxygen-containing gas.