Inductively Coupled Plasma Etch Rate Recovery via Segmented Oxygen and Argon Treatment
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Solution Overview
Problem
Prolonged etching of polyimide-coated silicon wafers in PVD pre-clean modules leads to carbonaceous deposits in the chamber, causing particle contamination and a significant drop in etch rate due to oxygen plasma treatment, resulting in non-uniformity and reduced throughput.
Innovation Solution
Interruption of etch processing for an oxygen plasma treatment followed by an argon plasma with biased platen to remove trapped oxygen, restoring the etch rate by diffusing oxygen out of the chamber walls as gaseous by-products, specifically using an inductively coupled plasma with RF biasing for 500-1200 seconds, preferably 600 seconds at 800 watts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If oxygen plasma treatment is used to remove carbonaceous deposits, then particle contamination is reduced, but etch rate drops significantly
Solution Approach 1:
The plasma treatment process is divided into two distinct segments: first an oxygen plasma step to oxidize and remove carbonaceous deposits, then an argon plasma step to restore etch rate by removing oxygen from chamber walls. This segmentation allows each step to optimize for its specific function without compromising the other.
Solution Approach 2:
The oxygen introduced during the first plasma step, which initially causes etch rate reduction, is converted into a beneficial effect in the second step. The trapped oxygen becomes the target for removal by argon plasma, and its elimination restores the etch rate. The harmful effect of oxygen trapping is transformed into a controllable intermediate state that can be deliberately removed.
2Object-affected harmful factors
If frequent oxygen plasma treatment is applied to maintain particle control, then chamber cleanliness is improved, but process uniformity deteriorates due to etch rate variation
Solution Approach 1:
The treatment is segmented into two functional parts: oxygen plasma for particle control and argon plasma for etch rate restoration. This segmentation allows frequent treatment to maintain cleanliness without the detrimental cumulative effect on etch rate uniformity, as each argon plasma step resets the etch rate condition.
Solution Approach 2:
The dual plasma treatment is applied periodically between batches of wafers. This periodic intervention maintains particle control while restoring etch rate conditions, creating a cyclic process that prevents both particle accumulation and etch rate degradation, thereby maintaining process uniformity across multiple wafer batches.
3Object-generated harmful factors
If oxygen plasma is used to oxidize carbon species, then carbonaceous deposits are removed, but oxygen becomes trapped in chamber walls causing subsequent etch rate reduction
Solution Approach 1:
The second argon plasma step specifically extracts and removes the oxygen that was trapped in the chamber walls during the oxygen plasma treatment. By taking out this trapped oxygen, the etch rate is restored to its original level, converting the harmful trapped oxygen into a removable intermediate that can be eliminated.
Solution Approach 2:
The oxygen trapped in chamber walls, which initially represents a harmful condition causing etch rate loss, is converted into a beneficial target for removal. The argon plasma treatment deliberately removes this trapped oxygen, and the resulting restoration of etch rate transforms the harmful trapped oxygen into a useful indicator of when treatment is needed.
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 method effectively recovers the original etch rate and maintains uniformity across successive wafers, with a >99% recovery after 600 seconds of biased argon plasma treatment, ensuring stable and consistent processing.
Implementation Method 1
the introduction of an oxygen plasma into a carbonised chamber will promote carbon oxidation, leading to CO/CO2 which may readily be pumped away
Implementation Method 2
Prolonged or frequent etching of PI wafers through the PVD pre-clean module can lead to a build-up of sputtered material around the chamber lid and walls
Implementation Method 3
Conveniently the argon plasma is an inductively coupled plasma
Data Source
AI summary
A method is for etching successive substrates on a platen in an inductively coupled plasma chamber in which the etching process results in carbonaceous deposits in the chamber. The method includes (a) interrupting the etching processing of substrates, (b) running an oxygen or oxygen containing plasma within the chamber and removing gaseous by-products, and (c) resuming the etch processing of substrates. The method is characterized in that it further includes the step of running an argon plasma in the chamber after step (b) with the platen biased.