[Tokyo Ohka Kogyo Co., Ltd.] Breaking through the 10 nm limit! Succeeded in developing a polymer block copolymer that enables semiconductor microfabrication with a line width of 7.6 nm
*Tokyo Ohka Kogyo Co., Ltd.*
Press release: August 22, 2024
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Breaking through the 10 nm limit! Succeeded in developing a polymer block copolymer that enables semiconductor microfabrication with a line width of 7.6 nm
*Tokyo Institute of Technology Tokyo Ohka Kogyo Co., Ltd.*
* [Key Points] *
○ Through molecular design in which the ratio of polar functional groups is precisely controlled and polymer synthesis using precision polymerization methods,
Developed a polymer block copolymer that enables semiconductor microfabrication with a line width of 7.6 nm
○ Contributing to bottom-up semiconductor microfabrication technology using nanostructures obtained through molecular self-assembly ○ Expectations for further improvements in the performance of electronic devices as semiconductor circuit patterns become finer and denser.
* 【overview】*
Tokyo Institute of Technology School of Materials Science and Engineering A research group consisting of materials professor Kokami Hayakawa, assistant professor Ken Hatakeyama, associate professor Yuta Nambae, graduate student Shinsuke Maekawa, Kazushi Sato, Naohiro Dazai, and Takehiro Seshita of Tokyo Ohka Kogyo Co., Ltd. is working to improve the performance of electronic devices. oriented 10
We have successfully developed a polymer block copolymer that enables sub-nm semiconductor microfabrication.
With the remarkable development of artificial intelligence and cloud services in recent years, and the miniaturization and higher performance of smartphones, it is important to develop finer processing technology to achieve even higher performance of
semiconductor chips installed in electronic devices. This has become a major issue. On semiconductor substrate*
Photoresist film*
(Term 1) Photolithography, which draws uneven patterns by irradiating light with a specific wavelength, is one of the top-down semiconductor microfabrication techniques and is the most widely used industrially. 13.5 as the current state-of-the-art technology
EUV lithography is an example of EUV lithography that uses light with a wavelength of nm.
The challenge is that microfabrication of nanometer scale or smaller cannot be achieved. To solve this problem, bottom-up microfabrication technology that uses nanostructures obtained through molecular self-assembly is currently attracting attention.
In this research, we aim to create a polymer that follows the chemical pattern of polystyrene by designing a molecule that precisely controls the proportion of *polar functional groups* (term 3) and synthesizing the polymer using a precision polymerization method.
Microphase separation structure*
We have developed a new polymer block copolymer in which (Term 4) is arranged. This polymer block copolymer is used to form a circuit pattern with a line width of 7.6 cm in a thin film coated on a silicon substrate.
It was revealed that a linear structure corresponding to nm was formed. This result will contribute to the improvement of bottom-up semiconductor microfabrication technology, and is expected to lead to miniaturization of semiconductor circuit patterns and higher density of integrated circuits.
This research result was obtained through joint research between Tokyo Institute of Technology and Tokyo Ohka Kogyo Co., Ltd., and was published in “* Nature Communications*” on July 6, 2024.
‘ Published online.
* ●Background*
With the remarkable development of artificial intelligence and cloud services in recent years and the miniaturization and higher
performance of smartphones, improving microfabrication technology to achieve even higher performance of semiconductor chips installed in electronic devices has become an important issue. It has become. Photolithography, which draws uneven patterns by irradiating a photoresist film on a semiconductor substrate with light of a specific wavelength, is one of the top-down semiconductor microfabrication technologies and is the most widely used industrially. .
The current state-of-the-art technology is EUV lithography that uses light with a wavelength of 13.5 nm, but with conventional exposure equipment, the uneven pattern obtained is uneven, and the line width is 10 nm.
Microfabrication of nm or less is difficult. On the other hand, the bottom-up method, which uses nanostructures obtained through the self-assembly of molecules, is attracting attention as a technology that compensates for the shortcomings of EUV lithography and enables finer processing.
Polymer block copolymers, which are expected to be used as bottom-up materials, have a characteristic molecular structure in which the ends of different polymer chains are bonded together, resulting in a structure called a microphase-separated structure due to the self-assembly of molecules. Forms a nanoperiodic structure. The periodic length of the microphase-separated structure is 5 to 100. Because it is on the order of nm, it is expected to be used as a mold for drawing circuit patterns on semiconductor substrates. A
microphase-separated structure is created in a block copolymer thinly coated on a semiconductor substrate, and by removing one component, the remaining component becomes a template for the desired circuit pattern (Figure 1). Block copolymers used in semiconductor
microfabrication are required to have the following properties. 1. The microphase-separated structure is oriented in the desired direction within the block copolymer thin film on the semiconductor substrate.
2. The repeating periodic length of the microphase separation structure is 20 nm or less (corresponding to the line width of the circuit pattern of 10 nm or less).
Figure 1. Schematic diagram of semiconductor microfabrication using block copolymers as bottom-up materials.
In order to use a microphase-separated structure as a template for microfabrication, the plate-like structure (lamellar structure) or columnar structure (cylinder structure) must be oriented
perpendicularly to the air interface. The key to vertical alignment is a special molecular design that tailors the interaction of the block copolymer components with air and the substrate. Block copolymers (PS-*) of polystyrene (PS) and polymethyl methacrylate (PMMA) have been most commonly used as bottom-up materials.
b* -PMMA) forms a vertical lamellar structure or a vertical
cylindrical structure because both components interact with air to the same degree. PS-* b* for companies and research institutes
-The development of semiconductor microfabrication processes based on PMMA is progressing, and it has become the standard material in the industry. However, it is an indicator of the difficulty of mixing ingredients*
Since the value of the Flory-Huggins interaction parameter (χ )* (term 5) is small for PS and PMMA and they easily mix with each other, PS-* b*
– Microfabrication using PMMA with a line width of 10 nm or less was extremely difficult.
* ●Research results*
In order to reduce the periodic length of the microphase-separated structure, it is required that the *χ* value between the constituent components of the block copolymer is large and that they are difficult to mix with each other. * between components
In block copolymers with large χ* values, PS-* b*
-A microphase-separated structure smaller than the lower limit of PMMA is formed, but there is a trade-off between the reduction in the periodic length and the vertical alignment of the microphase-separated structure.
Therefore, in this research, we developed a block copolymer with a large *χ* value while maintaining the vertical alignment of PS and PMMA, thereby achieving a line width of 10
We succeeded in forming a linear structure that can be used as a template for sub-nm circuit patterns. Specifically, *χ*
2,2,2-trifluoroethyl group and hydroxyl group are introduced into the PMMA block as polar groups to increase the value, and the introduction ratio is precisely controlled PS-* b*
-Designed PMMA derivatives.
The target block copolymer is one of the precision polymerization methods* Living anionic polymerization* (term 6) followed by* Polymer reaction*
(Term 7) (Fig. 2). Styrene, 1,1-diphenylethylene, and a mixture of methyl methacrylate (MMA) and glycidyl methacrylate (GMA) were sequentially added to the reaction solution, and the precursor PS-* b* -(PGMA-* r* -PMMA) was obtained. By adjusting the mixing ratio of MMA and GMA added to the reaction solution, PGMA-*r*
-We succeeded in synthesizing three types of precursors with controlled proportions of PGMA in PMMA: approximately 10, 20, and 30 mol%. PS-* b* -(PGMA-* r*
-PMMA) and 2,2,2-trifluoroethanethiol to obtain the desired PS-* b* -(PGMAF-* r* -PMMA).
Figure 2. Synthesis of PS-b-(PGMAF-r-PMMA)
In order to clarify the structural morphology and period length of the microphase-separated structure formed by the obtained block copolymer, small-angle X-ray scattering (SAXS) measurements and transmission electron microscopy (TEM) observations were performed. As a result of the analysis, the synthesized PS-*
b* -(PGMAF-* r* -PMMA) is line width 10
It was revealed that a fine lamellar structure corresponding to the nanometer scale was formed. In addition to 2,2,2-trifluoroethanethiol, we synthesized block copolymers using ethanethiol, benzenethiol, 2-phenylethanethiol, and cyclohexanethiol, and investigated the microphase-separated structure formed by each. When compared, PS-* It was found that b* -(PGMAF-* r* -PMMA) formed the most minute and clear lamellar structure.
PS-*b*
– In order to clarify the correlation between the amount of
2,2,2-trifluoroethyl groups and hydroxyl groups introduced into PMMA and the repulsive force between the constituent components, the apparent Flory-Huggins interaction parameter (*
When estimating χ* eff), we found that *χ*
It became clear that eff increased. This tendency is due to the effect of the introduced polar group and the * hydrogen bond * (Term 8) caused by the hydroxy group.
The research group believes that this is due to increased attractive interactions within the r* -PMMA block.
PS-* b* -(PGMAF-* r*
-PMMA) was deposited, and a microphase-separated structure was formed by heat treatment. Semiconductor microfabricated materials are required to have a microphase-separated interface in the block copolymer thin film oriented perpendicularly to the air interface. A fingerprint-like structure was observed by observing the thin film surface using an atomic force microscope (AFM), and the periodic length was 12.3–18.6.
It was found that a vertical lamellar structure of 1 nm was formed (lower left of Figure 3).
Figure 3. Schematic diagram of guided self-assembly and AFM phase image showing the difference in structures obtained with and without chemical patterns (Creative commons
Figures 5 and 7 of the published paper are reproduced with some modifications under the 4.0 license)
Scanning electron microscopy (SEM) observations of the inside of the thin film revealed that the lamellar structure interface was oriented perpendicular to the air interface even inside the thin film. PS-* b*
-Induced self-assembly, a method established based on PMMA, is a technology that promotes the arrangement of microphase-separated structures along the chemical pattern of PS and provides an ordered structure suitable for circuit patterns. A period length of 15.1 was achieved by guided self-assembly using a silicon substrate with a chemical pattern of PS.
By controlling the arrangement of the nano-lamellar structure, we succeeded in forming a linear structure with a line width of 7.6 nm (Figure 3).
* ●Social impact*
The line width of the linear structure obtained in this research is smaller than the lower limit of the pattern line width obtained by EUV lithography, and is 10
This enables microfabrication of nanometers or less. This is expected to lead to higher resolution of semiconductor circuit patterns and higher density of integrated circuits, leading to accelerated improvements in the performance of electronic devices.
* ●Future developments*
In the future, PS-* b* -(PGMAF-* r*
-PMMA) will be applied to form a circuit pattern through guided self-assembly, and we plan to evaluate its functionality for practical use as a semiconductor microfabrication material.
*●Additional note*
This research was supported by the Ministry of Education, Culture, Sports, Science and Technology Grant-in-Aid for Scientific Research (20H02785, 24H00052). Graduate student Shinsuke Maekawa is part of the JST Next Generation Researcher Challenging Research Program
The research was conducted with support from JPMJSP2106.
* [Term explanation] *
(1) *Photoresist film*: A film of photosensitive material used in photolithography.
The solubility changes with light irradiation, and the circuit pattern mold can be made by removing the soluble part. give.
(2) *Line width*: Width dimension of the circuit pattern. This is different from process nodes such as “3 nm process.”
(3) *Polar functional group*: A substituent in which an atom with high electronegativity and an atom with low electronegativity are covalently bonded.
The polarity of charge caused by the difference in the electric negative system between atoms is called polarity. As a polar functional group
Hydroxy group (-OH), carboxy group (-COOH), amino group (-NH2), Examples include trifluoromethyl group (-CF3).
(4) *Micro phase separation structure*: Formed when the constituent components of a block copolymer do not mix with each other and phase separate.
nanoperiodic structure. Various forms of periodic structures are formed depending on the molecular structure of the block copolymer and the proportions of its constituent components.
(5) *Flory-Huggins interaction parameter (χ )*: Miscibility of polymer-solvent or polymer-polymer
An indicator of When the value is positive, it is difficult for the components to mix with each other, and when the value is negative, the components are easy to mix.
(6) *Living anionic polymerization*: A precision polymerization method for vinyl monomers using a negatively charged substance as an initiator.
one. Because side reactions such as chain transfer reactions and termination reactions do not occur during the monomer growth reaction, separation is possible.
A polymer whose molecular structure is precisely controlled can be obtained. (7) *Polymer reaction*: Reaction between a polymer and a low molecule or between polymers.
(8) *Hydrogen bond*: A hydrogen atom that is covalently bonded to an atom with high electronegativity such as an oxygen atom binds a nearby isolated charge.
A type of non-covalent bond that is formed by interacting with an atom that has a child pair.
* [Paper information] *
Magazine: * Nature Communications *
Paper title: Chemically tailored block copolymers for highly reliable sub-10-nm patterns by directed self-assembly
Author: Shinsuke Maekawa, Takehiro Seshimo, Takahiro Dazai, Kazufumi Sato, Kan Hatakeyama-Sato, Yuta Nabae & Teruaki Hayakawa
DOI: 10.1038/s41467-024-49839-0
* [Inquiries] *
Tokyo Institute of Technology, School of Materials Science and Engineering, Materials Department, Professor
Akiyoshi Hayakawa
Email: hayakawa.t.ac@m.titech.ac.jp
TEL: 03-5734-2421
Tokyo Ohka Kogyo Co., Ltd. Public Relations CSR Department Public Relations Division
TEL: 044-435-3000
* [Interview application address] *
Tokyo Institute of Technology General Affairs Department Public Relations Division
Email: media@jim.titech.ac.jp
TEL: 03-5734-2975 FAX: 03-5734-3661
Tokyo Ohka Kogyo Co., Ltd. Public Relations CSR Department Public Relations Division
TEL: 044-435-3000