Edge Ring Voltage Control Circuits for Wafer Edge Profile Uniformity
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Solution Overview
Problem
Existing plasma processing technologies face challenges in achieving uniformity across substrates, particularly at the perimeter or edge, due to electric field termination effects, varying ion density, and RF uniformity, which can lead to reduced die yields.
Innovation Solution
The apparatus and methods involve independently tunable edge ring and substrate voltage control circuits to generate a voltage difference between the edge ring and substrate, allowing for precise control of the plasma sheath near the substrate edge, thereby improving process uniformity and feature verticality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple RF source voltages are applied to control edge ring voltage, then process uniformity at substrate edge is improved, but device cost increases
Solution Approach 1:
The patent replaces the traditional mechanical/electrical approach of using multiple RF source voltages with a DC voltage control system. A single RF power source is used, and the edge ring voltage is controlled by applying a DC voltage to the edge ring electrode, which modulates the plasma sheath height at the substrate edge without requiring multiple complex RF voltage sources.
2Manufacturing precision
If movable edge rings are used to control plasma sheath, then process profile control is improved, but reliability decreases due to arcing and particle contamination
Solution Approach 1:
The substrate support is segmented into two distinct electrodes: a substrate electrode for holding the substrate and an edge ring electrode for controlling the plasma sheath at the substrate perimeter. This segmentation allows independent control of the edge region without requiring movable parts, eliminating arcing issues while maintaining precise process profile control.
Solution Approach 2:
A DC voltage is introduced as an intermediary control mechanism between the power source and the plasma. By applying DC voltage to the edge ring electrode, the plasma sheath height is modulated without requiring direct RF voltage modulation or mechanical movement, thereby preventing arcing and improving reliability.
3Manufacturing precision
If DC voltage is applied to edge ring electrode, then process uniformity is improved without moving parts, but control circuit complexity increases
Solution Approach 1:
The invention changes the control parameter from RF voltage modulation to DC voltage application. By applying DC voltage to the edge ring electrode, the system achieves precise control over plasma sheath height and process uniformity. The DC voltage control circuits are designed to be independently tunable, allowing separate optimization of substrate and edge ring voltages without requiring complex coordinated control.
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 approach enhances process uniformity across the substrate, particularly at the edges, by adjusting the plasma sheath, which improves die yields and allows for precise control of extreme edge process profiles without the need for moving parts.
Implementation Method 1
manipulating the voltage at the edge ring relative to a substrate located on a substrate support, which functions as an effective tuning knob to control the process profile near a substrate edge
Data Source
AI summary
The present disclosure relates to an apparatus and method that manipulate the voltage at an edge ring relative to a substrate located on a substrate support assembly. The substrate support assembly has a body having a substrate support portion having a substrate electrode embedded therein for applying a substrate voltage to a substrate. The body of the substrate support assembly further has an edge ring portion disposed adjacent to the substrate support portion. The edge ring portion has an edge ring electrode embedded therein for applying an edge ring voltage to an edge ring. An edge ring voltage control circuit is coupled to the edge ring electrode. A substrate voltage control circuit is coupled to the substrate electrode. The edge ring voltage control circuit and the substrate voltage control circuit are independently tunable to generate a difference in voltage between the edge ring voltage and the substrate voltage.