Radical Etching Apparatus for Thick SiO2 Films
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Solution Overview
Problem
Conventional radical etching techniques using NFH radicals are limited in etching thickness, with an upper limit of about 8 nm, and struggle to efficiently remove thick films due to short-lived H radicals and deactivation issues during transportation to the vacuum chamber.
Innovation Solution
A radical etching apparatus and method utilizing a vacuum chamber with plasma generation and microwaves to produce H radicals, which react with F-containing gases like NF3, HF, or F2, forming HF radicals for etching SiO2 layers, allowing for high-speed etching of thick films up to 100 nm without self-stopping effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional radical etching using NFH radicals is used, then etching can be performed on SiO2 films, but the etching thickness is limited to about 8 nm due to short-lived H radicals that deactivate during transportation
Solution Approach 1:
The patent generates H radicals directly within the vacuum chamber before introducing NF3 gas, ensuring that H radicals are present and active when NF3 is introduced to form NFH radicals for etching. This preliminary generation of H radicals eliminates the transportation deactivation problem.
Solution Approach 2:
The patent uses NF3 gas as an intermediary that reacts with H radicals to form NFH radicals. This intermediary approach allows the system to overcome the short lifetime of H radicals by converting them into more stable NFH radicals that can perform the etching function.
2Manufacturing precision
If NFH radicals are used for etching, then SiO2 removal is achieved, but the process is slow and cannot handle thick films efficiently
Solution Approach 1:
The patent dynamically switches between two etching modes: using NFH radicals for high-selectivity etching of thin SiO2 films, and using HF radicals for high-speed etching of thick SiO2 films. This dynamic adaptation allows the system to optimize for both precision and speed depending on the film thickness.
Solution Approach 2:
The patent changes the chemical composition parameters of the etching plasma by controlling the introduction timing and amount of NF3 gas. By adjusting these parameters, the system can shift the dominant radical species from NFH to HF, thereby changing the etching characteristics from high-selectivity to high-speed mode.
3Productivity
If HF radicals are generated by direct plasma irradiation of NF3, then high etching speed is achieved, but F radicals are also generated causing unwanted etching of SiNx films
Solution Approach 1:
The patent performs preliminary generation of H radicals in the vacuum chamber before introducing NF3 gas. This ensures that when NF3 is introduced, it reacts with pre-generated H radicals to form HF radicals through a controlled chemical reaction rather than direct plasma dissociation, thereby avoiding excessive F radical generation.
Solution Approach 2:
The patent uses H radicals as an intermediary that mediates the conversion of NF3 to HF radicals. This intermediary mechanism provides a controlled pathway that produces HF radicals for high-speed etching while avoiding the uncontrolled dissociation that would generate harmful F radicals.
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 enables high-speed etching of thick films exceeding conventional limits, achieving etch thicknesses of over 100 nm with improved etching efficiency and selectivity, suitable for semiconductor manufacturing processes.
Implementation Method 1
the formation of NFH radicals has been accelerated by controlling the direct formation of HF while taking care not to cause any direct irradiation of NF3 with plasma or ions and the NFxHy radicals thus generated have been used for the etching of SiO2
Implementation Method 2
allowing the H radicals to undergo a reaction with NF3 separately introduced into the vacuum chamber (see, for instance, Patent Document 1 as will be specified below). The generation of a plasma through the use of μ waves has been carried out by introducing N2 gas and H2 gas or NH3 gas into a quartz tube or a sapphire tube and then irradiating the gas mixture with μ waves
Implementation Method 3
H radicals; introducing the resulting H radicals into a vacuum chamber; and then allowing the H radicals to undergo a reaction with NF3 separately introduced into the vacuum chamber
Implementation Method 4
a radical etching technique (CDT) in a gaseous phase has recently been used, which makes use of NFH radicals (NFxHy radicals) such as NF2H or NFH2 radicals. When carrying out the removal of an SiO2 film through etching procedures with the use of NFH radicals, (NH4)2SiF6 is formed as a residue product
Implementation Method 5
the lifetime of the H radicals thus produced is quite short and a problem correspondingly arises such that it is quite difficult to transport the H radicals to a vacuum chamber without any deactivation of the same
Implementation Method 6
The removal of this residue product has in general been carried out through evaporation, while heating the product to a temperature on the order of 200° C. This method for the removal of (NH4)2SiF6 as the residue product makes the most use of the characteristic properties peculiar to the same such that it can be vaporized at a temperature of about 120° C.
Data Source
AI summary
A radical etching apparatus comprising a vacuum chamber for a substrate to be treated; a pipe pathway, connected to the vacuum chamber, a zone for generating plasma and a gas introduction device through which N2 and at least one of H2 and NH3 can be introduced; a microwave applying microwaves to the interior of the pipe pathway; a gas introducer as a source of supply for F, between the vacuum chamber and the zone; and a shower plate. A method comprises introducing N2 and at least one of H2 and NH3 into a pipe pathway and applying microwaves. The gas mixture is decomposed by the plasma forming decomposition products as active species which react with F during transportation to the vacuum chamber to make radicals. An SiO2 layer on the substrate etched in the vacuum chamber, by irradiating the substrate with the radicals through the shower plate.