Block Copolymer Patterning via UV-Assisted Solvent Etching
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Solution Overview
Problem
The existing directed self-assembly lithography techniques face challenges in achieving a high solubility ratio between A and B polymer regions in block copolymers when using organic solvents, which affects the formation of stable patterns for etching masks.
Innovation Solution
A pattern forming method involving the formation of a block copolymer film on a substrate, followed by heating and irradiation with ultraviolet light in an inert gas atmosphere, and subsequent treatment with an organic solvent to enhance the solubility ratio between A and B polymer regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an organic solvent is used to remove PMMA regions in block copolymer patterning, then the solubility of PMMA regions is improved, but the solubility ratio between PMMA and PS regions cannot be sufficiently increased
Solution Approach 1:
The patent changes the chemical state of the block copolymer by irradiating it with ultraviolet light, which chemically modifies the PMMA regions to enhance their solubility in organic solvents. This parameter change (chemical modification through UV irradiation) transforms the solubility characteristics of PMMA without requiring the development of new solvent systems, thereby resolving the contradiction between achieving high solubility ratio and limited solvent availability.
Solution Approach 2:
The patent introduces ultraviolet light irradiation as an intermediary process between the application of block copolymer and the solvent treatment step. This intermediary treatment modifies the PMMA regions in situ, creating a bridge that enables effective solubility differentiation without requiring external solvent optimization. The UV irradiation acts as a mediator that prepares the PMMA regions for subsequent organic solvent removal.
2Reliability
If energy rays such as electron rays or X-rays are used to cut PMMA main chains, then the solubility of PMMA in organic solvents is improved, but the solubility ratio is still not sufficient and the process complexity increases
Solution Approach 1:
The patent replaces expensive and complex high-energy irradiation equipment (electron rays, X-rays) with a simpler, more accessible ultraviolet light source. UV light achieves the same chemical modification effect on PMMA main chains but with significantly reduced equipment complexity and cost. This substitution follows the principle of using simpler, more readily available means to achieve the desired chemical effect.
Solution Approach 2:
The patent changes the energy parameter of the irradiation process from high-energy particles (electron rays, X-rays) to lower-energy ultraviolet photons. This parameter change maintains the effectiveness of PMMA main chain scission while dramatically simplifying the required equipment and reducing process complexity, thereby resolving the contradiction between achieving sufficient solubility improvement and minimizing device complexity.
3Reliability
If the block copolymer film is irradiated with ultraviolet light in air, then the PMMA regions become easier to dissolve, but excessive oxidation occurs which degrades the quality of polymer regions
Solution Approach 1:
The patent applies ultraviolet light irradiation in an inert gas atmosphere (nitrogen or rare gas) to prevent oxidation of the block copolymer film during the PMMA main chain scission process. The inert atmosphere acts as a protective environment that allows the desired chemical modification of PMMA to occur without the harmful side effect of oxidation. This resolves the contradiction between enhancing PMMA solubility and preventing polymer degradation.
Solution Approach 2:
The patent converts the potentially harmful effect of ultraviolet light (which can cause oxidation when present in air) into a beneficial process by controlling the atmosphere. The UV irradiation is used specifically to scission PMMA main chains, and by excluding oxygen through inert gas atmosphere, the harmful oxidation pathway is eliminated while the beneficial chain scission and solubility enhancement proceed uninterrupted.
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 method significantly improves the solubility ratio between A and B polymer regions, allowing for the formation of precise patterns that can withstand etching processes, thereby overcoming the limitations of previous techniques.
Implementation Method 1
when the substrate is heated, the A polymer chain and the B polymer chain mutually randomly solid-dissolve undergo phase separation to form A polymer regions and B polymer regions which are regularly arrayed
Implementation Method 2
irradiating the heated film of the block copolymer with ultraviolet light in an atmosphere of an inert gas... When the phase separated PS-b-PMMA is irradiated with the energy ray, the main chain of PMMA is cut and PMMA becomes easy to dissolve in the organic solvent
Implementation Method 3
it is preferable to use an organic solvent to which the solubility of the PMMA regions is high and the solubility of the PS regions is low... the solubility ratio of the solubility of the PMMA regions to the solubility of the PS regions
Data Source
AI summary
The present invention is a pattern forming method of forming a pattern on a substrate using a block copolymer, the pattern forming method including the steps of: forming a film of a block copolymer containing at least two kinds of polymers on the substrate; heating the film of the block copolymer; irradiating the heated film of the block copolymer with ultraviolet light in an atmosphere of an inert gas; and supplying an organic solvent to the film of the block copolymer irradiated with the ultraviolet light.