Semiconductor Edge Ring Design for Plasma Sheath Uniformity
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Solution Overview
Problem
Conventional semiconductor process kits cause perturbations in the plasma sheath, leading to non-uniform ion flux and etch non-uniformities due to modifications in the shape of the plasma sheath, particularly at the edge of the substrate, resulting in inefficient semiconductor fabrication processes.
Innovation Solution
A process kit with an edge ring comprising a non-metallic, conductive inner ring and a quartz outer ring, featuring a notch along its inner diameter, is designed to minimize perturbations by maintaining a precise gap and height difference with the substrate, reducing edge effects and ensuring the plasma sheath remains undisturbed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional process kit is used in the plasma chamber, then the substrate can be processed, but the process kit causes perturbations in the plasma sheath leading to non-uniform ion flux and etch non-uniformities
Solution Approach 1:
The process kit components are designed with specific local properties: the edge ring is made of non-metallic conductive material with controlled resistivity (less than 50 Ohm-cm), the spacer has precise thickness (50-200 micrometers), and the process kit flange has specific dimensions. These localized quality specifications minimize plasma sheath perturbations at critical interfaces while maintaining overall kit functionality.
Solution Approach 2:
The invention changes key parameters of the process kit: using non-metallic conductive material instead of conventional materials, controlling resistivity to less than 50 Ohm-cm, specifying spacer thickness of 50-200 micrometers, and setting the edge ring outer diameter to 25-40 mm. These parameter changes optimize plasma sheath uniformity and reduce etch non-uniformities.
2Manufacturing precision
If the process kit is positioned close to the substrate to reduce edge effects, then processing uniformity improves, but the plasma sheath shape is modified causing ion flux non-uniformity
Solution Approach 1:
The spacer acts as an intermediary element between the substrate and the process kit flange, maintaining a precise gap of 50-200 micrometers. This intermediary spacing reduces edge effects on processing uniformity while minimizing disruption to the plasma sheath shape, thereby balancing both requirements.
3Manufacturing precision
If the process kit components are made with precise dimensions to maintain plasma sheath uniformity, then etch uniformity improves, but the device complexity increases
Solution Approach 1:
The process kit is segmented into distinct functional components: edge ring, spacer, process kit flange, and inner ring. Each component has specific dimensional specifications (edge ring outer diameter 25-40 mm, spacer thickness 50-200 micrometers, etc.) that can be manufactured independently with precise control, simplifying the overall manufacturing process while maintaining plasma sheath uniformity.
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 process kit effectively reduces ion focusing and defocusing effects, maintaining uniform plasma etching across the substrate, thereby improving processing uniformity and widening the processing window regardless of plasma conditions.
Implementation Method 1
The non-metallic, conductive body has a resistivity of less than about 50 Ohm-cm
Implementation Method 2
A plasma region comprising one or more processing gases is maintained within the semiconductor process chamber
Implementation Method 3
A plasma sheath is a thin region of strong electric fields formed by a space charge that separates the plasma to a material boundary
Implementation Method 4
The ions produced in a plasma region are accelerated in the plasma sheath in a trajectory perpendicular to the plasma sheath
Data Source
AI summary
The implementations described herein generally relate to a process kit suitable for use in a semiconductor process chamber, which reduces edge effects and widens the processing window with a single edge ring as compared to conventional process kits. The process kit generally includes an edge ring disposed adjacent to and surrounding a perimeter of a semiconductor substrate in a plasma chamber. A dimension of a gap between the substrate and the edge ring is less than about 1000 μm, and a height difference between the substrate and the edge ring is less than about (+/−) 300 μm. The resistivity of the ring is less than about 50 Ohm-cm.