Professor Bong-Joong Kim's research team develops a super-insulating 3D nanostructure that is stable at high temperatures
□ Professor Bong-Joong Kim of the School of Material Science and Engineering at the Gwangju Institute of Science and Technology (GIST, President Seung Hyeon Moon) collaborated with Professor Julia Greer of the California Institute of Technology to develop a strong, lightweight, and flexible low-k dielectric material that is an electrically and thermally stable super-insulator.
* Low-k dielectric: A material with a low dielectric constant, typically less than 4, that has a physical value that indicates the influence of the medium between the charges when an electric field is applied.
□ In recent years, the development of materials with low dielectric constant is becoming an important research topic because they play a key role in the application of high efficiency microelectronic devices, such as computer processing, wireless communication, and autonomous vehicles.
∘ Lowering the dielectric constant value of the low-k materials used between the wirings of the semiconductor devices mitigates the resistance-capacitance delay (RC delay *) caused by the integration of the semiconductor devices (Cross-talk *). Low dielectric properties are also a key factor in the direct implementation of passive components, such as inductors, capacitors, and resistors, in multichip module technology and 3D circuits for the microwave communications industry. In particular, antennas and RF modules require substrates of low dielectric materials to prevent surface wave propagation and to increase the frequency range. Furthermore, low permittivity structures are attracting attention for insulation and insulation purposes in high voltage systems, such as spacecraft, aircraft, and hydrogen-powered vehicles.
* RC delay: Delay due to the time it takes to charge and discharge the capacitor in a circuit composed of a resistor and a capacitor.
* Cross talk: The electric signal of a communication line is usually coupled electromagnetically with another communication line to interfere with the operation of another communication line.
□ However, despite the importance of low dielectric materials, the development of materials is difficult because a lower dielectric constant makes it more difficult it is to satisfy the other required properties. To apply low dielectric materials in semiconductors, the mechanical strength, electrical reliability, and thermal stability must be improved in addition to low dielectric constants.
∘ The recent introduction of a porous structure to lower the dielectric constant is considered a solution. As the porosity increases, the dielectric constant of the material decreases due to the low dielectric constant (about 1.0) of the air layer. However, in such a low-density structure, it is difficult to control the density, size, and distribution of pores by using hard, inorganic materials, but the mechanical strength, ductility, thermal stability, and electrical reliability are very weak. Because of this problem, researchers have not been able to fabricate materials with dielectric constants lower than 1.45 in the frequency range of 1 MHz, and there have been no case studies of various properties of materials at these ultralow dielectric constant regions (k <1.5).
□ To achieve the necessary properties while lowering the dielectric level of the air, the joint research team used sophisticated 3d laser etching and atomic layer deposition technology. Ceramic nanotubes were successfully arranged to form a 3D-nanolattice structure. In particular, it was possible to quantify the dielectric constants and other physical properties could be quantified by introducing a planar layer capable of depositing electrodes on the top and bottom surfaces of the nanolattice structure.
∘ The fabricated three-dimensional nanolattice capacitors consisted of about 99% of the total volume of air and showed an ultra-low dielectric constant of 1.06-1.10 (measured at 1 MHz). The mechanical properties showed a Young's modulus of 30 MPa, a yield strength of 1.07 MPa, and excellent ductility as the structure was completely restored even after compressive deformation of more than 50%. Thermal stability is almost negligible, with the TCK up to 800oc, 2.43 × 10-5 K-1, in the range of wide frequencies (105 to 106 Hz), voltage (-20v to 20v), temperature (room temperature to 800 degrees Celsius), and the dielectric loss value was at a very low 0.01 to 0.1.
* Young's modulus: The ratio of the rate of change of the length of the object to the applied stress when stretching or compressing the object from both sides. It is the strength of the elastic deformation area without permanent deformation of the material.
* Yield strength: The actual approximate value of the elastic limit as the material exhibits permanent deformation.
□ The overall performance of this low dielectric material is about 100 times superior in terms of mechanical strength of semiconductors produced by NASA and other prominent companies.
□ Professor Bong-Joong Kim said, "The result of this study is the first successful application of ceramic 3D-nanolattice structure in the field of low dielectric materials for use in microelectronics applications. It is a breakthrough that totally improves the strength, electrical, and thermal properties of ultralow dielectric materials."
