Selective Silicon Oxide Etching Using Cyclic Plasma
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Solution Overview
Problem
Existing methods for etching trenches in silicon oxide containing layers with via plugs suffer from issues like chamfering, fencing, and aspect ratio-dependent etching, leading to device failures such as leakage and metal void formation.
Innovation Solution
A method involving a plasma processing chamber with alternating deposition and etch phases using specific fluorocarbon or hydrofluorocarbon gases and RF power settings to selectively etch trenches, minimizing polymer deposition and aspect ratio dependence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to etch trenches in silicon oxide containing layers, then etching can be performed, but chamfering, fencing, and aspect ratio-dependent etching occur leading to device failures
Solution Approach 1:
The patent applies periodic action by implementing alternating deposition and etch phases in a cyclic manner. During each cycle, a deposition phase deposits polymer material to protect sidewalls, followed by an etch phase that removes silicon oxide. This periodic cycling continues for multiple iterations to achieve the desired trench depth while maintaining profile precision and preventing device failures
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting gas flow rates, RF power levels, and phase durations throughout the etching process. The deposition phase uses specific gas compositions and power levels to optimize polymer deposition, while the etch phase uses different parameters to optimize silicon oxide removal. These parameter variations enable precise control over trench profile and etching selectivity
2Manufacturing precision
If polymer deposition is minimized during etching, then trench profile improves, but etching selectivity and protection of via plugs may be compromised
Solution Approach 1:
The periodic alternation between deposition and etch phases allows the process to accumulate protective polymer layers during deposition phases, then utilize these layers during etch phases to protect via plugs and maintain selectivity. The cycling ensures sufficient polymer protection is built up before etching begins, resolving the contradiction between minimizing polymer and maintaining protection
Solution Approach 2:
The patent uses parameter changes to optimize the balance between polymer deposition and etching. By adjusting gas flow rates, RF power, and phase durations, the process deposits just enough polymer to protect via plugs and maintain selectivity, then switches to etching parameters that remove silicon oxide efficiently while preserving the protective polymer layer on non-target surfaces
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 reduces chamfering and fencing, enhances etching selectivity, and reduces aspect ratio dependence, resulting in improved trench profiles and device reliability.
Implementation Method 1
providing a constant RF power with a RF frequency of at least 60 MHz, which forms the deposition phase gas into a plasma
Implementation Method 2
providing a pulsed RF power with a RF frequency of at least 60 MHz, which forms the etch phase gas into a plasma
Data Source
AI summary
A method for selectively etching trenches in a silicon oxide containing layer with an organic planarization layer is provided. Processing the silicon oxide layer comprises a plurality of process cycles, wherein each etch cycle comprises a deposition phase, comprising providing a flow of a deposition phase gas comprising a fluorocarbon or hydrofluorocarbon containing gas with a fluorine to carbon ratio, providing a constant RF power, which forms the deposition phase gas into a plasma, and stopping the deposition phase and an etch phase, comprising providing a flow of an etch phase gas comprising a fluorocarbon or hydrofluorocarbon containing gas with a fluorine to carbon ratio that is higher than the fluorine to carbon ratio of the deposition phase gas, providing a pulsed RF power, which forms the etch phase gas into a plasma, and stopping the etch phase.