Plasma-Limiting Gap in Process Kit Shield
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Solution Overview
Problem
In plasma-enhanced substrate processing systems, materials from the processing volume can contaminate components on the non-processing side due to plasma penetration through gaps in the process kit, especially at higher RF frequencies and lower chamber pressures, causing arcing and deposition issues.
Innovation Solution
A process kit with a shield and a movable ring that forms gaps with a width less than two plasma sheath widths at frequencies of 40 MHz or higher and pressures of 140 mTorr or lower, effectively limiting plasma travel and preventing contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If process kits use standard gap sizes in components, then ease of manufacture is improved, but plasma penetration and contamination of non-processing volumes occurs at higher RF frequencies and lower pressures
Solution Approach 1:
The patent applies parameter changes by adjusting the gap width between process kit components to be less than two plasma sheath widths, specifically optimized for higher RF frequencies (40 MHz or higher) and lower pressures (140 mTorr or lower). This parameter adjustment prevents plasma penetration while maintaining ease of manufacture by using simple dimensional changes rather than complex structural modifications.
2Object-affected harmful factors
If gap width between process kit components is reduced to prevent plasma penetration, then contamination is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a quantitative parameter range for gap width (less than two plasma sheath widths) that balances contamination prevention with manufacturing feasibility. This parameter change provides clear manufacturing specifications while achieving the desired contamination reduction, avoiding overly stringent precision requirements.
3Object-affected harmful factors
If process kits are designed with movable rings that form precise gaps, then plasma containment is improved, but device complexity increases
Solution Approach 1:
The patent incorporates a movable ring component that can be positioned to form the required gap with the shield. This dynamic element allows the gap to be adjusted or maintained at the optimal width (less than two plasma sheath widths) while using a simple mechanical structure that does not significantly increase device complexity.
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 solution effectively restricts plasma from reaching non-processing volumes, reducing contamination and undesirable effects such as arcing and deposition, thereby enhancing the cleanliness and reliability of substrate processing.
Implementation Method 1
a gap is formed between an outer surface of the first ring and an inner surface of the one or more sidewalls, wherein a width of the gap is less than about two plasma sheath widths for a plasma formed at a frequency of about 40 MHz or higher and at a pressure of about 140 mTorr or lower
Data Source
AI summary
Apparatus for processing substrates are provided herein. In some embodiments, an apparatus includes a process kit comprising a shield having one or more sidewalls configured to surround a first volume, the first volume disposed within an inner volume of a process chamber; and a first ring moveable between a first position, wherein the first ring rests on the shield, and a second position, wherein a gap is formed between an outer surface of the first ring and an inner surface of the one or more sidewalls, wherein a width of the gap is less than about two plasma sheath widths for a plasma formed at a frequency of about 40 MHz or higher and at a pressure of about 140 mTorr or lower.