Sub-chamber Plasma Endpoint Detection for High-Pressure Etching
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Solution Overview
Problem
Existing plasma etching methods face challenges in accurately detecting the endpoint of the etching process due to sluggish response and difficulty in monitoring exhaust and reaction products, particularly at high pressures where reaction products do not effectively reach the plasma, leading to potential delays and errors in end-point determination.
Innovation Solution
An apparatus with a sub-chamber and window upstream of the pumping port allows for the creation of a local plasma in exhaust gases, enabling monitoring of optical emissions to improve endpoint detection, featuring a coil for excitation and a detector for processing signals, which enhances sensitivity and response speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma etching is performed at high pressure, then etching efficiency is improved, but endpoint detection accuracy deteriorates due to sluggish response and inability of reaction products to reach the plasma
Solution Approach 1:
The system divides the exhaust gas monitoring into two separate plasma zones: a first plasma in the main etching chamber and a second plasma in a downstream analysis chamber. This segmentation allows the main chamber to operate at high pressure for efficient etching while the analysis chamber provides accurate endpoint detection by analyzing reaction products that have traveled through the exhaust path.
Solution Approach 2:
The exhaust gases act as an intermediary carrier, transporting reaction products from the high-pressure etching zone to the low-pressure analysis zone. This intermediary mechanism enables indirect monitoring of the etching process without compromising the high-pressure conditions needed for efficient etching.
2Device complexity
If optical emission monitoring is performed downstream of the pumping port, then system complexity is reduced, but response speed deteriorates due to sluggish response
Solution Approach 1:
The system performs preliminary action by creating a plasma in the exhaust gases downstream of the workpiece but upstream of the pumping port. This allows reaction products to be ionized and emit optical signals before being removed by the pump, providing early warning of endpoint conditions without requiring complex downstream analysis equipment.
Solution Approach 2:
The exhaust gases themselves serve the dual purpose of being removed from the system and simultaneously providing the medium for optical emission monitoring. The reaction products naturally present in the exhaust stream provide the signal source, eliminating the need for separate sampling and analysis systems.
3Measurement precision
If reaction products are ionized in the main plasma, then endpoint detection is achieved, but detection reliability deteriorates when pressure is high and products cannot reach the plasma
Solution Approach 1:
The system transitions from spatial monitoring (watching for products to reach plasma) to temporal monitoring (measuring optical emissions over time as products flow through the exhaust zone). This dimensional change in detection approach allows reliable endpoint detection even when reaction products cannot reach the main plasma due to high pressure conditions.
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 enables quick and accurate endpoint detection, reducing the risk of under- or over-etching and allows for more precise control of the etching process, even in high-pressure conditions, and can be used for other testing processes like gas quality assessment.
Implementation Method 1
creating a plasma in a sample of the exhaust gases to create an optical emission
Implementation Method 2
create an optical emission which can be monitored through the window
Data Source
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AI summary
Apparatus for chemically etching a Workpiece includes a chamber for receiving a process gas and having a pumping port for extracting exhaust gases, and a Workpiece support located in the chamber upstream of the pumping port. The chamber further includes a sub-chamber located upstream of the pumping port and downstream of the Workpiece support, and the sub-chamber includes a window and an excitation source, adjacent the window, for creating a plasma in a sample of the exhaust gases to create an optical emission which can be monitored through the window.