Plasma Mounting Table Periodic Voltage Control
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Solution Overview
Problem
In plasma processing, the application of a bias voltage to a mounting table prevents secondary electrons from reaching the substrate, limiting the ability to perform processes that utilize electrons, such as reforming photoresist films or alleviating shading effects.
Innovation Solution
A plasma processing method where a high frequency voltage is applied to a mounting table for a predetermined period, then stopped, alternating between application and cessation to allow secondary electrons to reach the substrate while maintaining effective etching with positive ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a bias voltage is applied to the mounting table to perform etching process, then positive ions are attracted to the wafer for physical etching, but the sheath generated repels electrons preventing them from reaching the wafer
Solution Approach 1:
The patent applies high frequency voltage to the mounting table in periodic cycles, alternating between application and cessation. During the application period, positive ions are attracted for etching; during the cessation period, the sheath disappears allowing secondary electrons to reach the wafer. This periodic switching resolves the contradiction by separating the two functions in time rather than space.
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
Enables both etching and curing processes on the substrate by ensuring secondary electrons can reach the wafer, improving etching selectivity and preventing striations, allowing for deeper hole formation and uniformity in semiconductor device fabrication.
Implementation Method 1
high frequency voltage for plasma generation is applied to the mounting table in the processing chamber, by which a processing gas supplied into the processing chamber is excited to generate a plasma (i.e., positive ions and/or electrons)
Implementation Method 2
as the mounting table is applied with a bias voltage, a sheath is generated above the wafer, which is a region of high electron density. The positive ions are accelerated toward the wafer by the sheath, thereby physically etching it
Implementation Method 3
Since a potential is a constant in the DC voltage unlike as in the high frequency voltage, the positive ions are continuously attracted to the upper electrode to thereby collide therewith. Secondary electrons are emitted from atoms in the upper electrode by the positive ions colliding therewith, thereby increasing the electron density in the processing chamber
Data Source
AI summary
A plasma processing method performed in a plasma processing apparatus including a processing chamber accommodating a substrate in which a plasma is generated; a mounting table mounting the substrate, which is provided in the processing chamber and to which a plasma attraction high frequency voltage is applied; and a facing electrode provided to face the mounting table in the processing chamber, to which a negative DC voltage is applied, the method including: applying a plasma attraction high frequency voltage to the mounting table for a predetermined period of time; and stopping the application of the plasma attraction high frequency voltage to the mounting table. In the plasma processing method, the application of the plasma attraction high frequency voltage and stopping thereof are alternately repeated.