Upper Electrode Bias Timing for Stable Plasma Ignition
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Solution Overview
Problem
Existing plasma processing apparatuses face challenges in managing discharges at the upper electrode, particularly during the initiation of plasma generation, which can lead to temperature increases and inefficiencies.
Innovation Solution
A plasma processing apparatus with a controller that manages the application of negative voltages to the upper electrode using multiple voltage levels and periods, including a first period with a lower absolute value followed by a second period with a higher absolute value, and an OFF period with an even higher absolute value, to control discharges and maintain electrode temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant negative voltage is applied to the upper electrode during the entire ON period, then ion drawing-in is maintained, but abnormal discharges occur at the gas holes during plasma initiation
Solution Approach 1:
The patent applies periodic action by dividing the ON period into distinct phases with different voltage levels. A first negative voltage is applied during a first period (including plasma initiation), then switched to a second negative voltage during a second period. This periodic voltage modulation suppresses abnormal discharges at the gas holes during initiation while maintaining ion drawing-in stability throughout the plasma generation cycle.
Solution Approach 2:
The patent implements parameter changes by varying the voltage level applied to the upper electrode based on the plasma generation stage. The controller switches between a first negative voltage (with first absolute value) and a second negative voltage (with second absolute value) to adapt to different plasma conditions. This dynamic parameter adjustment prevents harmful discharges during initiation while preserving ion drawing-in during stable operation.
2Temperature
If high negative voltage is applied to suppress discharges, then electrode temperature stability is maintained, but ion drawing-in efficiency decreases
Solution Approach 1:
The patent resolves this contradiction through periodic action by applying different voltage levels at different times. During the first period (plasma initiation), a first negative voltage is applied to suppress abnormal discharges and control temperature. During the second period (stable plasma generation), a second negative voltage with different absolute value is applied to optimize ion drawing-in efficiency. This time-dependent voltage modulation allows the system to achieve both temperature stability and high ion drawing-in efficiency at different stages.
Solution Approach 2:
The patent applies dynamics by making the upper electrode voltage adjustable and time-dependent rather than constant. The controller dynamically switches between voltage levels based on plasma generation progress, enabling the system to adapt to changing conditions. This dynamic voltage control allows optimization of both temperature stability during initiation and ion drawing-in efficiency during stable operation, resolving the static contradiction between these two requirements.
3Reliability
If negative voltage is applied throughout the entire ON period, then plasma generation is maintained, but unnecessary voltage application increases energy consumption
Solution Approach 1:
The patent applies periodic action by implementing distinct voltage application periods within the ON period. A first negative voltage is applied during a first period for plasma initiation and stabilization, then a second negative voltage (with different absolute value) is applied during a second period for maintained plasma generation. This periodic voltage modulation ensures plasma continuity while reducing energy consumption by adjusting voltage levels according to actual plasma generation needs at different stages.
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 effectively suppresses abnormal discharges and maintains electrode temperature stability, enhancing the efficiency and reliability of plasma processing.
Implementation Method 1
generate a source radio-frequency power for generating plasma from the gas in the chamber
Implementation Method 2
generate an electric bias for drawing ions in the chamber into a substrate on the substrate support
Implementation Method 3
apply a negative voltage to the upper electrode... effectively suppresses abnormal discharges and maintains electrode temperature stability
Data Source
AI summary
A plasma processing apparatus comprising: a chamber; a substrate support disposed in the chamber; an upper electrode disposed above the substrate support including a plurality of gas holes. In an ON period, a source radio-frequency power is supplied to a radio-frequency electrode from a radio-frequency power source, and an electric bias is supplied to the substrate support from control a first bias power source to in the ON period. A first negative voltage of which a voltage level has a first absolute value is applied from a second bias power source to the upper electrode in a first period of the ON period. A second negative voltage of which a voltage level has a second absolute value is applied from the second bias power source to the upper electrode in a second period of the ON period. The first absolute value is smaller than the second absolute value.