Plasma Processing RF Power Modulation for Uniform Plasma Density
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Solution Overview
Problem
Existing plasma processing apparatuses face challenges in achieving uniform plasma density distribution across the substrate, leading to high density at the center and low density on the outer radial sides, which can result in decreased or disappearing plasma density.
Innovation Solution
The plasma processing apparatus employs a radio frequency power source generating two distinct power levels within a cycle of the bias power, with a higher power level in a first period and a lower power level in a second period, overlapping partially with the cycle, to maintain plasma density uniformity and prevent its decrease.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If radio frequency power is supplied continuously at a constant power level, then plasma generation is maintained, but plasma density becomes non-uniform with high density at the center and low density on the outer radial sides
Solution Approach 1:
The patent applies periodic action by supplying radio frequency power in a pulsed manner with varying power levels within each period. Specifically, the power supply follows a periodic pattern where a first power level is applied during a first time period and a second power level (different from the first) is applied during a second time period within the same period. This periodic variation in power supply prevents plasma density non-uniformity and maintains stable plasma generation throughout the processing chamber.
Solution Approach 2:
The patent implements dynamics by making the radio frequency power supply variable rather than constant. The power level dynamically changes within each period, transitioning between at least two different power levels. This dynamic power adjustment allows the plasma density to be maintained uniformly across different radial positions in the processing chamber, preventing the formation of high-density centers and low-density outer regions that occur with constant power supply.
2Force
If radio frequency bias power is supplied to draw ions into the substrate, then ion bombardment is enhanced for processing, but plasma density may decrease or disappear
Solution Approach 1:
The patent resolves this contradiction by applying periodic action to the radio frequency power supply. Within each period, the power is supplied at a first power level during a first time period (enhancing ion bombardment for processing) and at a second power level during a second time period (maintaining plasma density). This periodic modulation allows the system to achieve both strong ion bombardment forces and sustained plasma density, preventing plasma disappearance that would occur with continuous high-power bias supply.
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 the uniformity of plasma density distribution in the radial direction and prevents a decrease or disappearance of plasma density, ensuring consistent processing results.
Implementation Method 1
The bias power source is coupled to the electrode and configured to generate bias power having a first frequency. The radio frequency bias power is supplied to the lower electrode.
Implementation Method 2
The radio frequency power source is coupled to the plasma processing chamber and configured to generate radio frequency power having a second frequency higher than the first frequency. The radio frequency power has a first power level in a first period within one cycle of the bias power and has a second power level lower than the first power level in a second period within one cycle of the bias power.
Data Source
AI summary
The disclosed plasma processing apparatus includes a plasma processing chamber, a substrate support, a bias power source, and a radio frequency power source. The substrate support is disposed in the plasma processing chamber and includes an electrode. The bias power source is coupled to the electrode and configured to generate a bias power having a first frequency. The radio frequency power source is coupled to the plasma processing chamber and configured to generate a radio frequency power having a second frequency higher than the first frequency. The radio frequency power has a first power level in a first period within one cycle of the bias power and has a second power level lower than the first power level in a second period within one cycle of the bias power.