Stepped Focus Ring Structure for Stable Plasma Edge Etching
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Solution Overview
Problem
Plasma etching apparatuses face challenges in achieving uniform etching due to difficulty in controlling plasma on the outer side of the electrostatic chuck, leading to lower etch rates at the edge of substrates compared to the central area, and existing focus rings are prone to instability during the etching process.
Innovation Solution
A focus ring design with a seating part and a body part, featuring a first and second corrosion-resistant layer, where the second layer is thinner and includes a chucking enhancement layer with a dielectric constant lower than the second layer, enhancing chucking force by 30% or more, and a gas layer between the focus ring and electrostatic chuck to improve plasma guidance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a focus ring is provided on the outer circumference of the object to be etched to guide plasma flow, then etching uniformity is improved, but the focus ring shakes during the etching process causing unstable etching
Solution Approach 1:
The focus ring is divided into multiple sections with different thicknesses along the radial direction. The first section has a greater thickness than the second section, creating segments with different mechanical properties. This segmentation allows the thicker first section to provide structural support and prevent shaking, while the thinner second section maintains plasma guidance functionality, thus resolving the contradiction between stability and uniformity.
2Ease of operation
If high-frequency power is supplied above and below the electrostatic chuck to generate plasma, then plasma generation is easy to control in the high-frequency power supply area, but plasma control is difficult on the outer side of the electrostatic chuck
Solution Approach 1:
The focus ring acts as an intermediary component between the electrostatic chuck and the plasma environment. It is supplied with high-frequency power to generate plasma locally on the outer side of the electrostatic chuck, where plasma control is otherwise difficult. This intermediary plasma generation mechanism bridges the gap between the easily controllable central area and the difficult-to-control outer area, enabling uniform etching across the entire substrate surface.
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 enhanced focus ring design stabilizes the chucking force and improves etching uniformity by increasing the chucking force and maintaining balance, allowing for more efficient and uniform plasma etching across the substrate surface.
Implementation Method 1
an electrostatic chuck disposed within the chamber
Implementation Method 2
The plasma etching process may be performed by converting gas introduced into the chamber into a plasma using a high-frequency power source supplied between the electrodes, and using the plasma to etch a substrate mounted on the electrostatic chuck. The radicals or ions that make up the plasma react physically and chemically with the substrate surface to etch the substrate.
Implementation Method 3
the focus ring guides the plasma to flow toward the surface of the object to be etched, thereby improving the processing efficiency
Implementation Method 4
The body area includes a first corrosion resistant layer and the chucking reinforcement area includes a second corrosion resistant layer. The second corrosion resistant layer is thinner than the first corrosion resistant layer, and the second corrosion resistant layer has a minimum thickness of 1 mm or more.
Data Source
AI summary
A plasma etching apparatus includes a chamber configured to generate plasma, an electrostatic chuck disposed in the chamber, and a focus ring placed on the electrostatic chuck and configured to support an object to be etched. The focus ring includes a seating part and a body part. A seating surface is provided on at least a portion of the seating part configured to seat the object to be etched thereon. The focus ring further includes a step provided between the seating part and the body part. The body part includes a body area and a chucking reinforcement area. The body area includes a first corrosion resistant layer, and the chucking reinforcement area includes a second corrosion resistant layer. The second corrosion resistant layer is thinner than the first corrosion resistant layer, and has a minimum thickness of 1 mm or more.