Stepped Focus Ring Structure for Stable Plasma Edge Uniformity
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Solution Overview
Problem
Plasma etching apparatuses face challenges in achieving uniform etching across the substrate due to difficulty in controlling plasma on the outer side of the electrostatic chuck, leading to lower etch rates at the edge 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 step between them, where the body part includes a first corrosion-resistant layer and a thinner second corrosion-resistant layer with a chucking reinforcement area, enhanced by a chucking enhancement layer, which improves chucking force by 30% or more, and is configured with a gas layer between the focus ring and the electrostatic chuck for improved plasma guidance.
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 its circumference. The thicker sections provide structural support and stability to prevent shaking, while the thinner sections allow plasma to pass through more effectively. This segmentation resolves the contradiction by maintaining both etching uniformity and stability simultaneously.
2Ease of operation
If high-frequency power is supplied above and below the electrostatic chuck to generate plasma, then plasma control is easy in the high-frequency power supply area, but plasma control is difficult on the outer side of the electrostatic chuck leading to lower etch rates at the edge
Solution Approach 1:
The focus ring is designed with non-uniform thickness distribution, having different thicknesses at different locations around its circumference. This local variation in structure allows the focus ring to guide plasma flow effectively to areas that would otherwise have poor plasma control, specifically compensating for the lower plasma density at the outer edges of the substrate.
3Productivity
If the focus ring is made with various shapes such as inclined shape to improve processing efficiency, then plasma guidance is enhanced, but etching becomes unstable due to focus ring shaking
Solution Approach 1:
Rather than using a uniform inclined shape throughout, the focus ring employs segmented thickness variation where only specific sections have inclined or reduced thickness. This segmentation maintains the plasma guidance benefits of inclined shapes in critical areas while preserving structural stability in other sections, preventing the shaking that would occur with a completely inclined design.
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 plasma etching across the substrate surface.
Implementation Method 1
an electrostatic chuck disposed within the chamber
Implementation Method 2
converting gas introduced into the chamber into a plasma using a high-frequency power source supplied between the electrodes
Implementation Method 3
using a high-frequency power source supplied between the electrodes
Implementation Method 4
the focus ring guides the plasma to flow toward the surface of the object to be etched
Data Source
Figure 1
Figure 2~3
Figure 4~5
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.