Plasma Etching of Recessed Oxide Films With Nitride Selectivity
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Solution Overview
Problem
Existing etching methods struggle to selectively etch silicon oxide films with respect to silicon nitride films in a controlled manner, particularly in the presence of recesses, leading to inefficiencies and potential damage to underlying structures.
Innovation Solution
An etching method using a plasma processing apparatus that supplies a processing gas containing metal and fluorine, along with a gas capturing active species, and employs a source RF signal to generate plasma, allowing selective etching of silicon oxide films relative to silicon nitride films, especially in recessed areas, by controlling the power and frequency of RF signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to etch silicon oxide films, then etching can be performed, but selectivity with respect to silicon nitride films is insufficient leading to potential damage to underlying structures
Solution Approach 1:
The patent applies parameter changes by utilizing a dual-frequency RF system where a first RF signal at a first frequency generates plasma for etching, while a second RF signal at a second frequency (different from the first) is applied to the substrate bias electrode to control ion energy and direction. This dual-frequency parameter control enables precise adjustment of etching chemistry and ion bombardment energy independently, achieving high selectivity between silicon oxide and silicon nitride films while preventing damage to underlying structures through optimized ion flux control.
2Productivity
If high power RF signals are used to increase etching speed, then productivity improves, but control precision over the etching process deteriorates
Solution Approach 1:
The patent segments the RF power control into two independent frequency components: a first RF signal frequency component that controls plasma generation and chemistry, and a second RF signal frequency component applied to the substrate bias that controls ion energy and etching rate. This segmentation allows independent optimization of etching speed (through the second frequency power level) and etching precision (through the first frequency plasma conditions), resolving the trade-off between productivity and control precision.
3Device complexity
If single frequency RF signals are used to simplify the process, then device complexity is reduced, but etching selectivity and control deteriorate
Solution Approach 1:
The patent implements multi-functionality through a dual-frequency RF system where the first RF signal frequency generates plasma and controls chemical reactions, while the second RF signal frequency simultaneously controls ion acceleration and etching rate. This universal dual-frequency approach provides both simplified single-frequency operation (when only one frequency is needed) and enhanced dual-frequency control (when maximum selectivity is required), making the system adaptable to different process requirements while maintaining high etching selectivity.
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 enhances the selectivity and control of etching processes, ensuring precise removal of silicon oxide films without damaging underlying silicon nitride structures, thereby improving the precision and efficiency of semiconductor manufacturing.
Implementation Method 1
selectively etching the second film with respect to the first film in at least the recess by generating plasma from the processing gas by using a source radio frequency (RF) signal having a first frequency
Implementation Method 2
supplying a processing gas, which includes a first gas including metal and fluorine and a second gas capturing active species including fluorine, into the chamber
Data Source
AI summary
An etching method includes: (a) preparing a substrate on a substrate support disposed in a chamber, wherein the substrate includes a plurality of first regions and at least one second region disposed between the first regions in a plan view, wherein the substrate includes a first film containing silicon and nitrogen, wherein the first film is disposed in the first regions and includes a recess in the at least one second region, and wherein a second film is disposed in the recess; (b) supplying a processing gas, which includes a first gas including metal and fluorine and a second gas capturing active species including fluorine, into the chamber; and (c) while (b) is performed, selectively etching the second film with respect to the first film in at least the recess by generating plasma from the processing gas by using a source radio frequency signal having a first frequency.