Dual Upper Electrode Plasma Uniformity Control
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Solution Overview
Problem
Capacitively coupled plasma processing apparatuses face challenges in achieving uniform plasma density distribution and etching characteristics across a substrate, particularly when processing conditions change or when etching multilayer films, due to the passive nature of impedance control methods.
Innovation Solution
A plasma processing apparatus with a configuration that includes a lower electrode and two upper electrodes, where the inner and outer upper electrodes are electrically isolated and supplied with independently variable DC voltages to control electron density distribution and process characteristics, improving uniformity by adjusting these voltages during etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a capacitively coupled plasma processing apparatus is used to realize plasma with large diameter, then plasma generation is achieved, but uniform plasma density distribution across the substrate cannot be obtained
Solution Approach 1:
The upper electrode is divided into an inner upper electrode and an outer upper electrode that are electrically isolated from each other. This segmentation allows independent control of plasma generation (inner electrode) and plasma density distribution (outer electrode), resolving the contradiction between achieving large plasma diameter and maintaining uniform plasma density across the substrate.
Solution Approach 2:
Different regions of the upper electrode are assigned different functions: the inner upper electrode is optimized for plasma generation while the outer upper electrode is optimized for controlling plasma density distribution. This local differentiation enables each region to perform its specialized function effectively, achieving both large plasma diameter and uniform density.
2Adaptability or versatility
If conventional impedance control method is used to vary plasma density distribution, then some control is achieved, but flexible control under various processing conditions is difficult
Solution Approach 1:
The control system is segmented into two independent DC voltage control channels, one for the inner upper electrode and one for the outer upper electrode. This segmentation provides flexible control capability without requiring complex interconnected control systems, as each channel can be adjusted independently to adapt to various processing conditions.
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 configuration allows for flexible control of plasma uniformity and etching characteristics, enhancing the uniformity of etching rates and pattern accuracy across the substrate, even under varying processing conditions, by effectively altering the etching rate at the substrate edge while maintaining consistency at the central portion.
Implementation Method 1
a radio frequency (RF) power supply unit for applying an RF power to the lower electrode or the inner and outer upper electrode to generate a plasma of the processing gas by RF discharge
Implementation Method 2
electrons accelerated by an RF electric field formed between the electrodes, secondary electrons emitted from the electrodes, or heated electrons collide with molecules of the processing gas to ionize them to thereby generate plasma of the processing gas
Implementation Method 3
a first DC power supply unit for applying a first variable DC voltage to the inner upper electrode; and a second DC power supply unit for applying a second variable DC voltage to the outer upper electrode
Data Source
AI summary
A plasma processing apparatus includes an inner upper electrode provided to face a lower electrode mounting thereon a substrate, an outer upper electrode provided in a ring shape at a radially outside of the inner upper electrode and electrically isolated from the inner upper electrode in a vacuum evacuable processing chamber and a processing gas supply unit for supplying a processing gas into a processing space between the inner and the outer upper electrode and the lower electrode. A radio frequency (RF) power supply unit is also provide to apply a RF power to the lower electrode or the inner and the outer upper electrode to generate a plasma of the processing gas by RF discharge. A first and a second DC power supply unit are provided to apply a first and a second variable DC voltage to the inner upper electrode, respectively.