Plasma Chuck Bias Circuits for Uniform Edge Ring Ion Incidence
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Solution Overview
Problem
Existing plasma processing apparatuses face challenges in maintaining uniform voltage waveforms between the substrate and the edge ring due to differences in capacitance, leading to non-uniform ion incidence on the substrate, particularly as the edge ring wears and thins.
Innovation Solution
The apparatus incorporates a first and second bias power source with separate circuits having different impedances to equalize current distribution between the substrate and edge ring, using variable resistors and capacitors to adjust impedance based on edge ring thickness, and a controller to manage these adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single bias power source is used for both substrate and edge ring, then device complexity is reduced, but voltage waveform uniformity deteriorates due to capacitance differences
Solution Approach 1:
The single bias power source is segmented into two separate bias power sources: a first bias power source connected to the substrate electrode and a second bias power source connected to the edge ring electrode. This segmentation allows independent control of voltage waveforms applied to the substrate and edge ring, compensating for capacitance differences and achieving uniform voltage waveforms despite the increased device complexity
Solution Approach 2:
Different bias power sources with different output characteristics are applied to different regions (substrate vs. edge ring) based on their specific capacitance requirements. The first bias power source is optimized for the substrate's larger capacitance while the second is optimized for the edge ring's smaller capacitance, achieving local optimization of voltage waveform uniformity
2Duration of action of stationary object
If edge ring thickness decreases due to wear, then device durability worsens, but voltage waveform difference increases leading to processing uniformity deterioration
Solution Approach 1:
The system incorporates feedback control where the second bias power source continuously monitors and adjusts the voltage waveform applied to the edge ring based on the actual capacitance value, which changes as the edge ring wears. This feedback mechanism compensates for thickness degradation, maintaining voltage waveform uniformity and processing consistency throughout the edge ring's service life
Solution Approach 2:
The bias power source system transitions from static to dynamic operation, where the second bias power source dynamically adjusts its output parameters in response to changing edge ring capacitance. This dynamic adaptation allows the system to maintain optimal performance despite the progressive wear and thinning of the edge ring
3Reliability
If capacitance difference between substrate and edge ring is large, then electrical performance varies, but current distribution uniformity deteriorates
Solution Approach 1:
The system changes the electrical parameters (voltage amplitude, frequency, phase) of the two bias power sources to compensate for the capacitance difference. By adjusting these parameters independently for each electrode, the system achieves uniform current distribution despite the inherent capacitance mismatch between the substrate and edge ring
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 reduces the difference in voltage waveforms between the substrate and edge ring, ensuring uniform ion incidence and maintaining processing consistency even as the edge ring wears.
Implementation Method 1
The second circuit has impedance higher than impedance of the first circuit at a common bias frequency of the first electrical bias and the second electrical bias
Implementation Method 2
The substrate support has a lower electrode and an electrostatic chuck. The electrostatic chuck is provided on the lower electrode
Implementation Method 3
Radio frequency bias power is supplied to the lower electrode in order to draw ions from plasma into the substrate
Data Source
AI summary
A disclosed plasma processing apparatus includes a substrate support. The substrate support has a first region configured to support a substrate and a second region configured to support an edge ring. The first electrode is provided in the first region. The second electrode is provided in the second region. The first bias power source is connected to the first electrode via the first circuit. The second bias power source is connected to the second electrode via the second circuit. The second circuit has impedance higher than impedance of the first circuit at a common bias frequency of a first electrical bias generated by the first bias power source and a second electrical bias generated by the second bias power source.