Anisotropic Etching Device with Segmented Plasma Zones
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Solution Overview
Problem
Fluorine-based high-rate etching processes for silicon substrates face challenges due to the recombination of silicon-etching fluorine radicals and passivating Teflon-forming species in plasma, leading to suboptimal etching rates and selectivity, as these species typically annihilate each other in the plasma.
Innovation Solution
Spatial separation of the generation of silicon-etching fluorine radicals and Teflon-forming passivation species, allowing them to mix outside the plasma reaction zones, with a device featuring separate reaction chambers and a mixing system to ensure uniform mixing and application onto the substrate, enhancing etching rates and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If silicon-etching fluorine radicals and passivating Teflon-forming species are generated in the same plasma reaction zone, then the plasma generation is simplified, but the species annihilate each other by recombination reactions leading to suboptimal etching rates and selectivity
Solution Approach 1:
The plasma generation system is segmented into two separate plasma reaction zones: a first plasma reaction zone for generating silicon-etching fluorine radicals from etching gas, and a second plasma reaction zone for generating passivating Teflon-forming species from passivation gas. This spatial segmentation prevents recombination losses while maintaining high etching rates and selectivity.
Solution Approach 2:
A mixing device acts as an intermediary between the two plasma reaction zones and the etching chamber. This mixing device combines the separately generated fluorine radicals and Teflon-forming species in a controlled manner before they reach the substrate, ensuring optimal concentrations for both etching and passivation without premature recombination.
2Manufacturing precision
If the proportion of passivating gas is increased to improve sidewall protection, then mask selectivity improves, but etching rate decreases due to species recombination in plasma
Solution Approach 1:
By segmenting the plasma generation into separate zones, the system can optimize the passivation gas proportion in the second plasma reaction zone without suffering from recombination losses that would occur in a mixed plasma. This allows sufficient Teflon-forming species to reach the substrate for effective sidewall protection while maintaining high etching rates.
Solution Approach 2:
The passivating Teflon-forming species are generated in advance in the second plasma reaction zone and then mixed with the etching species just before reaching the substrate. This preliminary generation and controlled mixing ensures that the passivating species are available in sufficient quantities for sidewall protection without being lost to recombination reactions.
3Device complexity
If fluorine radicals and Teflon-forming species are mixed in the plasma reaction zone, then the process is simplified, but recombination reactions reduce the effectiveness of both etching and passivation
Solution Approach 1:
The reaction zones are segmented into separate plasma generation areas, with the first plasma reaction zone dedicated to generating fluorine radicals and the second plasma reaction zone dedicated to generating Teflon-forming species. This segmentation maintains reliability by preventing recombination reactions while the mixing device ensures proper mixing occurs only after both species are generated.
Solution Approach 2:
The mixing device serves as an intermediary that delays the mixing of fluorine radicals and Teflon-forming species until after both have been generated in their respective plasma zones. This controlled mixing approach preserves the effectiveness of both species by avoiding premature recombination reactions.
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 approach enables high-rate, anisotropic etching with improved mask selectivity and uniformity across the silicon wafer surface, even with a small proportion of passivating gas, by preventing premature recombination and optimizing the chain length of Teflon-forming species for effective protection and etching.
Implementation Method 1
By means of the first coil device, a first plasma is generated in the first reaction chamber
Implementation Method 2
By means of the second coil device, a second plasma is generated in the second reaction chamber
Implementation Method 3
The Teflon-forming reactive species generated in the passivation plasma advantageously have a minimum size or minimum length, also called minimum chain length, in order to be able to condense on the substrate and crosslink there to form the Teflon film
Data Source
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AI summary
The invention relates to a device for etching a substrate and to a method for operating a device according to the invention. The device comprises: a first reaction chamber into which a first gas can be introduced; a second reaction chamber into which a second gas can be introduced; a coil device by means of which an electromagnetic alternating field can be generated; wherein at least one first reactive species can be generated by applying the electromagnetic alternating field to the first gas and at least one second reactive species can be generated by applying the electromagnetic alternating field to the second gas; a separating device by means of which a direct gas exchange between the first reaction chamber and the second reaction chamber is prevented; an etching chamber for receiving the substrate to be anisotropically etched; and a mixing device which is arranged and designed such that the reactive species enter the mixing device, are mixed together, and in the mixed state act on the substrate so as to anisotropically etch same in the etching chamber.