Plasma Junction Box Filtering for Stable Sheath Voltage Control
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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 etch profiles and potential arcing issues due to cross-talk between multiple RF sources.
Innovation Solution
A plasma processing system with a junction box enclosure that includes dedicated filter circuits for a pulsed voltage source and a radio frequency source, allowing for the generation of distinct waveforms to be delivered to a substrate support and radio frequency baseplate without interference, enabling precise control over the IEDF and etch profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple RF sources are used to control plasma properties, then plasma density and ion energy control is improved, but cross-talk between RF sources causes arcing and power diversion
Solution Approach 1:
The patent segments the power delivery system into separate dedicated pathways for each RF source. Each RF source has its own matching network and power delivery line, preventing cross-talk and power diversion while maintaining the ability to independently control plasma properties through multiple RF sources
Solution Approach 2:
The patent introduces an intermediary impedance matching network between each RF source and the plasma load. This matching network acts as a buffer that prevents direct coupling between RF sources, eliminating cross-talk and arcing while still allowing each source to effectively control plasma properties
2Power
If lower frequency RF bias is used to achieve higher self-bias voltages, then self-bias voltage is improved, but ion energy distribution becomes broadened causing bowing of etched feature walls
Solution Approach 1:
The patent applies periodic pulsed RF bias instead of continuous sinusoidal RF bias. By delivering RF power in controlled pulses, the system achieves high self-bias voltages while maintaining a narrower ion energy distribution function, preventing the broadening that causes etch profile bowing
Solution Approach 2:
The patent changes the temporal parameters of RF bias delivery from continuous sinusoidal to pulsed waveform. This parameter change allows achieving higher self-bias voltages without the detrimental side effect of broadened ion energy distribution, thereby maintaining precise etch profile control
3Reliability
If RF voltage is applied to power electrode through thick dielectric layer, then plasma sheath formation is improved, but power delivery efficiency is reduced
Solution Approach 1:
The patent applies preliminary impedance matching through a dedicated matching network before power is delivered through the thick dielectric layer. This preliminary action optimizes the impedance relationship, maximizing power transfer efficiency while maintaining reliable plasma sheath formation through the dielectric barrier
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 robust and reliable plasma processing by maintaining a nearly constant sheath voltage, enhancing control over ion energy and etch profile, and reducing the risk of arcing, thereby improving the precision of feature formation on substrates.
Implementation Method 1
a radio frequency source configured to generate a radio frequency waveform having a second frequency that is higher than the first frequency
Implementation Method 2
a pulsed voltage source configured to generate a pulsed voltage waveform having a first frequency
Implementation Method 3
a pulsed voltage filter circuit coupled between the radio frequency source and the radio frequency conductor, the pulsed voltage filter circuit operable to filter the pulsed voltage waveform; a radio frequency filter circuit coupled between the pulsed voltage source and the direct current conductor, the radio frequency filter circuit operable to filter the radio frequency waveform
Implementation Method 4
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 5
ions from the plasma are accelerated towards a surface of a substrate to form openings in a material layer
Implementation Method 6
a radio frequency (RF) generator that is coupled to an RF electrode through an RF matching network ('RF match') that tunes the apparent load to 500 to minimize the reflected power and maximize the power delivery efficiency
Data Source
AI summary
Embodiments of plasma processing systems are provided. The plasma processing systems include a junction box enclosure electrically coupling a pulsed voltage source to a direct current conductor that is coupled to a substrate support and further electrically coupling the pulsed voltage source to a radio frequency conductor coupled to the radio frequency baseplate. The junction box enclosure includes a pulsed voltage filter circuit coupled between the radio frequency source and the radio frequency conductor, the pulsed voltage filter circuit operable to filter the pulsed voltage waveform. The junction box enclosure includes a radio frequency filter circuit coupled between the pulsed voltage source and the direct current conductor. The junction box enclosure includes a blocking capacitor coupled between the pulsed voltage source and the radio frequency filter circuit. The junction box enclosure includes one or more electrical components coupled between the direct current conductor and the radio frequency conductor.