Focus Ring Thickness Measurement Using In-Chamber Ultrasonic Sensors
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Solution Overview
Problem
Existing methods for monitoring focus ring thickness in microelectronic process chambers are ineffective due to varying rates of deterioration with different etch chemistries and process chambers, leading to inconsistencies in process uniformity.
Innovation Solution
Implementing in-chamber sensors to measure physical parameters of focus rings, using ultrasonic, capacitive, or resistive measurements to determine thickness, and adjusting focus ring position or replacing it based on these determinations to maintain process consistency across multiple chambers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If predictive models based on manufacture information are used to monitor focus ring deterioration, then the monitoring system is simple to implement, but the measurement precision is insufficient because deterioration rates vary with different etch chemistries and process chambers
Solution Approach 1:
The patent replaces mechanical/predictive modeling approaches with ultrasonic measurement technology. Ultrasonic sensors transmit sound waves through the focus ring and measure the time of flight or echo characteristics to determine thickness, providing direct physical measurement rather than relying on predictive models based on manufacturing data and operational history.
Solution Approach 2:
The patent introduces ultrasonic waves as an intermediary medium to measure focus ring thickness. The ultrasonic sensor acts as a mediator between the measurement system and the focus ring, allowing non-contact, precise thickness determination without requiring direct physical access or disassembly of the focus ring.
2Reliability
If focus rings are monitored using in-chamber sensors with real-time measurements, then the measurement precision and reliability are improved, but the device complexity increases due to additional sensors and measurement systems within the process chamber
Solution Approach 1:
The ultrasonic sensor system is designed to serve multiple functions: measuring focus ring thickness, monitoring plasma sheath characteristics, and detecting process chamber conditions. This multi-functionality reduces the need for separate dedicated sensors for each measurement type, thereby limiting the increase in overall system complexity.
Solution Approach 2:
The focus ring itself serves as part of the measurement system by reflecting ultrasonic waves back to the sensor. The structure being measured becomes an active participant in the measurement process, eliminating the need for additional complex measurement infrastructure.
3Measurement precision
If ultrasonic sensors are used to measure focus ring thickness, then the measurement precision is improved, but the use of energy increases due to continuous ultrasonic pulse transmission and reception
Solution Approach 1:
The ultrasonic sensor transmits pulses periodically rather than continuously, measuring focus ring thickness at specific intervals during the etch process. This periodic measurement approach maintains measurement precision while significantly reducing energy consumption compared to continuous monitoring.
Solution Approach 2:
The ultrasonic measurement system operates continuously during the etch process, utilizing the same plasma environment and chamber conditions for both processing and measurement. This eliminates the need for separate measurement cycles or additional energy-intensive preparation steps.
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
Accurately tracking focus ring deterioration allows for timely replacements and adjustments, extending maintenance intervals and ensuring uniformity in etch and deposition processes across process chambers.
Implementation Method 1
the one or more sensors are configured to provide ultrasonic measurements associated with the focus ring. In further embodiments, the processing system also includes one or more transmitters positioned to transmit ultrasonic pulses to the focus ring and one or more receivers configured to receive return pulses associated with surfaces of the focus ring, and the thickness determinations are based upon time differences between the return pulses
Implementation Method 2
the one or more sensors are configured to provide capacitive measurements associated with the focus ring based upon signals applied to the focus ring
Implementation Method 3
the one or more sensors are configured to provide resistive measurements associated with the focus ring
Data Source
AI summary
Methods and systems are disclosed for focus ring thickness measurement and feedback control within process chambers. For disclosed embodiments, in-chamber sensors measure physical parameters associated with focus rings, and these measurements are used to determine thickness for the focus rings. The thickness determinations can be used to detect when a focus ring should be replaced and can also be used as feedback to adjust the position of the focus rings within the chamber. For one embodiment, measurements from ultrasonic sensors are used to make thickness determinations for focus rings. For further embodiments, these ultrasonic sensors are positioned at end portions of focus ring lift pins. Other sensors can also be used such as capacitive sensors, resistive sensors, and/or other desired sensors. Further variations and implementations can also be achieved using in-chambers sensors to facilitate focus ring thickness determinations.