Selective Silicon Oxide Etching via Fluorocarbon Deposit Protection
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Solution Overview
Problem
Conventional methods for selectively etching silicon oxide regions with respect to silicon nitride regions in electronic device manufacturing often result in the exposure and scraping of the silicon nitride regions, and require extended processing times.
Innovation Solution
A plasma etching method involving sequential steps of generating plasma from different fluorocarbon gases to form deposits on the workpiece, followed by etching with inert gas radicals, which protects the silicon nitride region and enhances the etching rate of the silicon oxide region, thereby preventing scraping and reducing processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional plasma etching with fluorocarbon gas is used to etch silicon oxide regions, then etching can be performed, but the silicon nitride regions are exposed and scraped
Solution Approach 1:
The patent applies preliminary action by forming fluorocarbon deposits on the workpiece surface before the silicon nitride region is exposed. These deposits are formed in advance during the etching process and serve as a protective layer that prevents scraping of the silicon nitride region when it becomes exposed. The deposits are created by introducing fluorocarbon gas and controlling plasma conditions to favor deposition over etching at critical stages.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting plasma power, gas flow rates, and pressure conditions during the etching process. By changing these parameters, the balance between etching and deposition is controlled - initially favoring etching of silicon oxide, then shifting to favor fluorocarbon deposit formation on the workpiece surface when the silicon nitride region approaches exposure, thereby preventing scraping.
2Manufacturing precision
If conventional plasma etching is used, then silicon oxide can be etched, but the etching rate of silicon oxide is insufficient compared to silicon nitride
Solution Approach 1:
The patent applies periodic action by alternating between etching phases and deposit formation phases during the plasma processing. In etching phases, parameters are optimized for silicon oxide removal; in deposit phases, parameters are adjusted to form fluorocarbon layers that protect underlying structures. This periodic switching enables selective etching at enhanced rates while maintaining protection of silicon nitride regions.
Solution Approach 2:
The fluorocarbon deposits act as an intermediary layer that mediates between the plasma environment and the workpiece surface. These deposits selectively form on certain surfaces while allowing etching to proceed on others, enabling differential etching rates. The intermediary deposits protect silicon nitride regions from excessive etching while permitting controlled removal of silicon oxide regions.
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 suppresses the scraping of silicon nitride regions while increasing the etching rate of silicon oxide regions, thereby shortening the overall processing time and ensuring reliable opening formation without clogging.
Implementation Method 1
a workpiece is exposed to plasma of a fluorocarbon gas so that the region is etched
Implementation Method 2
the first region is etched and an upper opening is formed
Implementation Method 3
generating plasma of a second fluorocarbon gas to form fluorocarbon deposits on the first region
Implementation Method 4
generating plasma of an inert gas to etch the first region by fluorocarbon radicals contained in the fluorocarbon deposits
Data Source
AI summary
An etching method including: (a) providing a workpiece including a first region made of a first material and a second region made of a second material defining a recess, the first region filling the recess of the second region while covering the second region; (b) generating plasma of a first fluorocarbon gas to etch the first region until before exposing the second region; (c) generating plasma of a second fluorocarbon gas to form fluorocarbon deposits on the first region; (d) generating plasma of an inert gas to etch the first region by fluorocarbon radicals contained in the fluorocarbon deposits; and (e) repeating step (c) and step (d) one or more times until after exposing the second region. An etching rate of the first material of the first region is higher than that of the second material of the second region with respect to the second fluorocarbon gas.