Graded-Conductivity Focus Ring for Stable Wafer Edge Ion Angles
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Solution Overview
Problem
The miniaturization and high integration of semiconductor products lead to non-uniformities in the dry etching process, particularly in the edge region of wafers, due to variations in the incident angle of ions caused by the consumption of focus rings during plasma processing.
Innovation Solution
A plasma processing apparatus is designed with a focus ring having a lower region and an upper region with varying electrical conductivity, where the conductivity increases towards the lower region, and an edge ring to maintain a constant incident angle of ions at the wafer edge even as the focus ring is consumed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional focus ring with uniform electrical conductivity is used, then the structure is simple and easy to manufacture, but the incident angle of ions at the wafer edge becomes non-uniform during plasma processing due to focus ring consumption
Solution Approach 1:
The focus ring is designed with non-uniform electrical conductivity distribution, where different regions have different conductivity values. Specifically, the electrical conductivity varies in the vertical direction (from upper surface to lower surface) and/or radial direction, creating local property variations that compensate for the focus ring consumption during plasma processing, thereby maintaining uniform ion incident angle at the wafer edge throughout the process.
2Reliability
If the focus ring is designed with varying electrical conductivity to maintain constant ion incident angle, then plasma processing uniformity is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The electrical conductivity parameter of the focus ring is deliberately varied across different regions. This can be achieved by controlling the doping concentration distribution during semiconductor fabrication, where dopant concentration is adjusted to create the desired conductivity profile. This parameter change allows the focus ring to compensate for its own consumption during plasma processing, maintaining reliable and consistent ion incident angle without requiring complex mechanical adjustment mechanisms.
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 design ensures a consistent ion incident angle at the wafer edge throughout the plasma processing, preventing deformation and damage by maintaining uniform plasma treatment despite focus ring wear.
Implementation Method 1
the focus ring includes a lower region and an upper region disposed on the lower region, wherein an electrical conductivity of a first portion of the upper region is smaller than an electrical conductivity of a second portion of the upper region that is closer to the lower region than the first portion
Implementation Method 2
The dry etching process is mainly performed in a semiconductor manufacturing apparatus in which a plasma reaction is induced
Data Source
AI summary
A plasma processing apparatus may include a lower electrode supporting a wafer; a focus ring surrounding an edge of the lower electrode and having a ring shape; and an edge ring disposed in a position lower than a position of the focus ring. The focus ring may include a lower region and an upper region disposed on the lower region, and the upper region increases in electrical conductivity as the upper region is closer to the lower region.