Susceptor Potential Synchronization for Plasma Discharge Prevention
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Solution Overview
Problem
In plasma processing apparatuses, abnormal electric discharges can occur between the substrate and the susceptor due to high potential differences, potentially damaging the substrate, especially when a current limiting device is not provided between the susceptor and the focus ring.
Innovation Solution
Applying a negative DC voltage corresponding to the self-bias to the susceptor maintains a small potential difference between the substrate and the susceptor, preventing abnormal electric discharges by synchronizing the potential of the susceptor with the substrate's self-bias during the plasma process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a positive and high DC voltage is applied to the inner electrode of the electrostatic chuck to hold the substrate, then the substrate is attracted by electrostatic force, but a great potential difference is created between the substrate and susceptor causing abnormal electric discharge that can damage the substrate
Solution Approach 1:
The focus ring is electrically connected to the susceptor through a current limiting device, establishing an equipotential relationship between these components. This connection ensures that the focus ring and susceptor maintain the same electrical potential, preventing abnormal electric discharge in the peripheral region while allowing the central region to maintain the necessary potential difference for substrate holding and processing
Solution Approach 2:
A current limiting device is introduced as an intermediary component between the susceptor and the focus ring. This device restricts the flow of electric current, preventing excessive current that would cause abnormal electric discharge, while still allowing the focus ring to be electrically connected to the susceptor and maintain appropriate potential relationships
2Reliability
If a current limiting device is provided between the susceptor and focus ring to suppress abnormal electric discharge, then substrate damage is prevented, but device complexity increases
Solution Approach 1:
The current limiting function is merged with the existing focus ring structure. Rather than adding a completely separate component, the focus ring itself is configured to work with the current limiting device, integrating the protection function into the existing peripheral structure and reducing overall system complexity
Solution Approach 2:
The current limiting device is designed as a simple, inexpensive component that can be easily replaced if needed. By using a straightforward current limiting mechanism rather than a complex active control system, the solution maintains reliability while minimizing device complexity and cost
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 stabilizes and securely suppresses abnormal electric discharges between the substrate and the susceptor, ensuring the substrate is not damaged and improving the plasma etching process yield.
Implementation Method 1
a static electricity is generated on the substrate mounted on the susceptor by applying a high DC voltage (typically, about 2000 V to about 3000 V) to the inner electrode, so that the substrate is attracted or held by an electrostatic force
Implementation Method 2
in order to efficiently transfer a heat of the susceptor to the substrate, a back side gas (typically, He gas) for heat transfer is supplied at a preset pressure to a rear surface of the substrate through a gas path formed in the susceptor
Implementation Method 3
a high frequency power having a certain frequency is applied to the susceptor from a high frequency power supply at an outside of the processing chamber via a matching device during the plasma process
Data Source
AI summary
At a first timing after mounting a semiconductor wafer W on an electrostatic chuck 38, a susceptor 12 is switched from an electrically grounded state into a floated state. From a second timing after the first timing, a second high frequency power HF for plasma generation is applied to the susceptor 12, and a processing gas is excited into plasma in a chamber 10. From a third timing after the second timing, a first high frequency power LF for ion attraction is applied to the susceptor 12, and a self-bias (−Vdc) is generated. From a fourth timing close to the third timing, a negative second DC voltage −BDC corresponding to the self-bias (−Vdc) is applied to the susceptor 12. From the fifth timing after the fourth timing, a positive first DC voltage ADC is applied to an inner electrode 42 of the electrostatic chuck 38.