Plasma Etch Flash Steps for Polymer Buildup Control
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Solution Overview
Problem
During plasma etching processes, polymer accumulation on mask sidewalls leads to reduced etch rates, aspect ratio dependent etch-rate issues, and feature distortion due to deflected plasma species, with conventional methods failing to effectively decouple polymer accumulation at the top and sidewalls without impacting mask selectivity.
Innovation Solution
Incorporating multiple flash steps using a plasma etching system that generates plasma from a flash precursor gas containing oxygen and no fluorocarbons, with bias power applied during the flash step to selectively remove polymer material without damaging the mask, thereby controlling polymer accumulation and maintaining sidewall passivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional plasma etching is performed continuously, then etch rate is maintained, but polymer accumulates on mask sidewalls causing feature distortion and reduced etch rate consistency
Solution Approach 1:
The patent implements periodic flash steps interrupting the continuous etch process. During these flash steps, oxygen plasma is generated to remove accumulated polymer from mask sidewalls and openings. This periodic cleaning action prevents feature distortion while maintaining overall etch rate consistency by decoupling polymer removal from the main etching operation.
Solution Approach 2:
The patent extracts the polymer removal function from the continuous etch process by introducing separate flash steps with oxygen-based chemistry. This extraction allows selective removal of polymer deposits without affecting the mask material or target material etching, thereby resolving the contradiction between maintaining etch rate and preventing feature distortion.
2Manufacturing precision
If polymer removal is performed continuously, then polymer accumulation is reduced, but mask selectivity is compromised
Solution Approach 1:
By implementing periodic flash steps rather than continuous polymer removal, the patent maintains mask selectivity. The oxygen plasma is activated only during brief flash intervals to remove polymer, while the majority of the process time is dedicated to selective etching of the target material through fluorocarbon chemistry.
Solution Approach 2:
The patent changes plasma chemistry parameters by switching between fluorocarbon-based etch chemistry and oxygen-based cleaning chemistry. This parameter change enables selective polymer removal during flash steps while preserving mask selectivity during the main etch process, as the oxygen plasma conditions are optimized to affect polymer rather than mask material.
3Manufacturing precision
If flash steps are introduced to remove polymer, then polymer accumulation is controlled, but process time increases
Solution Approach 1:
The patent applies partial action by implementing brief flash steps that remove sufficient polymer to prevent feature distortion without completely eliminating all polymer. This partial removal approach achieves the necessary precision while minimizing the time penalty, as the flash steps are kept short and targeted rather than performing exhaustive polymer removal.
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 approach effectively decouples polymer accumulation at the top and sidewalls, reducing feature distortion and improving etch rate consistency by selectively removing polymer without impacting mask selectivity, thereby enhancing the efficiency and accuracy of the plasma etching process.
Implementation Method 1
The flash step is performed by generating plasma from a flash precursor gas
Implementation Method 2
The flash precursor gas includes oxygen and no fluorocarbons
Implementation Method 3
The etch step is performed by generating plasma from an etch precursor gas including an etchant species
Data Source
AI summary
A method of etching a target material using plasma includes cyclically performing the steps of an etch step for a first duration to etch a target material exposed in openings of a patterned mask material, and a flash step for a second duration after the first duration to remove polymer material accumulated at the openings during the etch step. The etch step is performed by generating plasma from an etch precursor gas including an etchant species. The target material may be a dielectric, such as a dielectric target material that includes an oxide. The flash step is performed by generating plasma from a flash precursor gas. Bias power may be provided to the substrate during the flash step. The flash species is different from the etchant species. The flash precursor gas may include oxygen and no fluorocarbons.