Plasma Etching Sequence for Oxide Selectivity Without Nitride Wear
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Solution Overview
Problem
In existing methods for selectively etching silicon oxide regions with respect to silicon nitride regions using plasma processing, there is a challenge in preventing wear on the silicon nitride regions during the etching process of the silicon oxide regions.
Innovation Solution
A method involving a sequence of plasma processing steps, where a deposit containing fluorocarbon is formed on the workpiece, and then the silicon oxide region is etched using radicals of fluorocarbon, while maintaining a substantially oxygen-free environment to minimize wear on the silicon nitride region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If plasma of a processing gas containing fluorocarbon gas and oxygen gas is used for etching the first region, then the etching speed is improved, but the second region made of silicon nitride is worn
Solution Approach 1:
A protective film is formed on the second region (silicon nitride) before the etching process begins. This preliminary protective layer prevents the silicon nitride from being worn during subsequent etching operations while allowing the first region (silicon oxide) to be etched at high speed using fluorocarbon-based plasma.
Solution Approach 2:
The protective film is selectively formed only on the second region (silicon nitride) that requires protection, while leaving the first region (silicon oxide) exposed for etching. This localized protection allows different regions to have different properties: the protected region resists wear while the unprotected region undergoes rapid etching.
2Manufacturing precision
If the processing gas is switched during etching to control deposit formation, then the selectivity is improved, but the processing time increases due to gas switching and discharge stabilization
Solution Approach 1:
The processing conditions (such as power, pressure, or gas flow rates) are adjusted within the fluorocarbon-based plasma to control the formation and removal of deposits on the protective film. This allows the protective film thickness to be dynamically controlled during a single etching process without switching gases, maintaining high selectivity while avoiding time losses from gas switching and discharge stabilization.
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 effectively etches the silicon oxide region while significantly reducing wear on the silicon nitride region, ensuring precise control over the etching process without the need to switch processing gases, thus avoiding complications related to discharge stabilization.
Implementation Method 1
generating plasma of a processing gas containing a fluorocarbon gas, an oxygen-containing gas, and an inert gas in a processing container accommodating the workpiece
Implementation Method 2
etching the first region with radicals of the fluorocarbon contained in the deposit
Implementation Method 3
form a deposit containing fluorocarbon on the workpiece
Data Source
AI summary
An apparatus which selectively etches a first region with respect to a second region made of a material different from that of the first region. The apparatus is controlled to perform a first step for generating, in a processing container housing a workpiece to be treated, a plasma of a treatment gas from a gas supply including a fluorocarbon gas, an oxygen-containing gas, and an inert gas, and forming a deposit including fluorocarbon on the object to be treated, and a second step for etching the first region with radicals of the fluorocarbon included in the deposit. The apparatus is also controlled to perform the first step and the second step repeatedly.