Ramp Edge Ring Geometry for Plasma Etch Uniformity
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Solution Overview
Problem
The consumption of edge rings in plasma treatment leads to non-uniform ion incidence on substrates, causing plane uniformity issues due to changes in the shape of the sheaths at the top of the edge rings, which affects the tilt of ions and the lifetime of the focus rings.
Innovation Solution
An edge ring design with an inner edge-side portion and an outer edge-side portion featuring a ramp surface where the height decreases from the outer edge-side portion toward the inner edge-side portion, configured to satisfy the relation T2/T1 > T4/T3, where T1 and T2 are pre-treatment thicknesses, and T3 and T4 are post-treatment thicknesses, to adjust the electric field strength and consumption rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional edge ring with uniform thickness is used, then the structure is simple and easy to manufacture, but the consumption rate is high at the inner edge-side portion causing ion tilt and plane uniformity failure
Solution Approach 1:
The edge ring employs a non-uniform thickness distribution along its radial direction, with the inner edge-side portion having a smaller thickness than the outer edge-side portion. This local variation in thickness creates different consumption rates at different radial positions, specifically reducing consumption at the inner edge-side portion to maintain plane uniformity and prevent ion tilt.
Solution Approach 2:
The edge ring design introduces asymmetry in the thickness distribution, where the thickness T(r) varies with radial position r. The inner edge-side portion (closer to the substrate center) has a different thickness compared to the outer edge-side portion, creating an asymmetric structure that optimizes consumption characteristics and maintains plasma uniformity.
2Reliability
If the thickness of the inner edge-side portion is increased to reduce consumption, then consumption rate decreases, but ion tilt increases and plane uniformity deteriorates
Solution Approach 1:
The edge ring employs a non-uniform thickness distribution along its radial direction, with the inner edge-side portion having a smaller thickness than the outer edge-side portion. This local variation in thickness creates different consumption rates at different radial positions, specifically reducing consumption at the inner edge-side portion to maintain plane uniformity and prevent ion tilt.
3Duration of action of stationary object
If DC voltage is applied to the focus ring to mitigate consumption effects, then lifetime is extended, but device complexity and operational complexity increase
Solution Approach 1:
The invention changes the geometric parameter (thickness) of the edge ring rather than applying electrical parameters. By modifying the physical structure (thickness distribution) of the edge ring, the consumption characteristics are optimized without requiring additional power sources or control systems, thus avoiding increased device complexity.
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 reduces the consumption rate of the inner edge-side portion, decreases ion energy at the inner edge, and improves plane uniformity by setting a greater electric field strength at the outer edge-side portion, thereby extending the edge ring's lifetime and reducing manufacturing costs.
Implementation Method 1
a greater electric field strength at the outer edge-side portion than at the inner edge-side portion
Data Source
AI summary
An edge ring includes a ramp surface of which a height decreases from an outer edge-side portion toward an inner edge-side portion. The edge ring is configured to satisfy the relation of T2/T1>T4/T3. Where, T1 is a thickness of the edge ring, before plasma treatment, at a first position on the ramp surface of the inner edge-side portion, and T2 is a thickness of the edge ring, before plasma treatment, at a second position on the ramp surface of the outer edge-side portion. T3 is a thickness of the edge ring, after plasma treatment, at the first position, and T4 is a thickness of the edge ring, after plasma treatment, at the second position.