Junction Box Filtering for Pulsed Plasma Bias and Stable IEDF
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Solution Overview
Problem
Conventional plasma processing systems face challenges in maintaining a consistent sheath voltage and ion energy distribution function (IEDF) during plasma etching, leading to undesirable arcing and inadequate control over feature profiles, especially in high aspect ratio etch applications.
Innovation Solution
A plasma processing system utilizing a junction box enclosure that filters and separates pulsed voltage and radio frequency waveforms, allowing for independent control of these waveforms to be delivered to the substrate support and radio frequency baseplate, thereby maintaining a stable sheath voltage and controlling IEDF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple conventional sinusoidal waveforms from two or more RF sources are delivered to control plasma properties, then plasma density and ion energy can be adjusted, but arcing problems occur and cross-talk between RF sources diverts power away from the plasma
Solution Approach 1:
The patent segments the plasma processing system into two independent power delivery paths: a pulsed voltage source connected to the substrate support assembly and conventional RF sources connected to the plasma generation electrodes. This segmentation isolates the pulsed voltage control from the RF sources, preventing cross-talk and arcing while maintaining independent control over ion energy and plasma density
Solution Approach 2:
The patent introduces an intermediary coupling mechanism where the pulsed voltage source is connected to the substrate support assembly rather than directly to the plasma. This intermediary position allows control over ion energy at the substrate interface without interfering with the RF-driven plasma generation, eliminating the direct conflict that causes arcing and cross-talk
2Use of energy by moving object
If lower frequency RF bias generator is used to achieve higher self-bias voltages, then ion energy can be increased, but the difference in energy between peaks of IEDF becomes significant causing bowing of etched feature walls
Solution Approach 1:
The patent changes the temporal parameter of voltage application by using pulsed voltage waveforms instead of continuous sinusoidal RF. This allows the system to achieve high ion energy during the pulse while maintaining a more controlled IEDF, as the pulsed nature prevents the formation of multiple energy peaks that cause wall bowing
Solution Approach 2:
The patent employs periodic pulsed voltage application to the substrate support, creating controlled ion bombardment cycles. The periodic pulsing allows ions to be accelerated to high energies only during specific time windows, resulting in a more uniform IEDF compared to continuous low-frequency RF bias, thereby reducing etch profile distortion
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
The system provides precise control over the etch profile and shape of features on the substrate surface, reducing arcing issues and enhancing the reliability of plasma processing.
Implementation Method 1
a pulsed voltage source configured to generate a pulsed voltage waveform
Implementation Method 2
a radio frequency source configured to generate a radio frequency waveform
Implementation Method 3
The junction box enclosure includes a pulsed voltage filter circuit coupled between the radio frequency source and the radio frequency conductor and operable to filter the pulsed voltage waveform
Implementation Method 4
The junction box enclosure further includes a radio frequency filter circuit coupled between the pulsed voltage source and the direct current conductor and operable to filter the radio frequency waveform
Implementation Method 5
The application of RF voltage to the power electrode causes an electron-repelling plasma sheath (also referred to as the 'cathode sheath') to form over a processing surface of a substrate
Implementation Method 6
One method of forming high aspect ratio features uses a plasma assisted etching process, such as a reactive ion etch (RIE) plasma process, to form high aspect ratio openings in a material layer
Data Source
AI summary
A plasma processing system includes a pulsed voltage source configured to generate a pulsed voltage waveform having a first frequency. The plasma processing system includes a radio frequency source configured to generate a radio frequency waveform having a second frequency that is higher than the first frequency. The plasma processing system includes a junction box enclosure electrically coupling the pulsed voltage source to a direct current conductor coupled to a substrate support and further electrically coupling the pulsed voltage source to a radio frequency conductor coupled to a radio frequency baseplate. The junction box enclosure includes a pulsed voltage filter circuit coupled between the radio frequency source and the radio frequency conductor and operable to filter the pulsed voltage waveform. The junction box enclosure further includes a radio frequency filter circuit coupled between the pulsed voltage source and the direct current conductor and operable to filter the radio frequency waveform.