GIST Develops Next-Generation Semiconductor Materials Improving Power Consumption and Information Density

Schematic diagram of perovskite materials with controlled ferroelectricity and dielectric properties regulated by grid tension, utilized as next-generation memory devices. Photo by GIST

[Asia Economy Honam Reporting Headquarters Reporter Cho Hyung-joo] Domestic researchers have developed a technology that can dramatically improve the power consumption and information density of existing semiconductor devices.

According to GIST (Gwangju Institute of Science and Technology) on the 1st, Professor Lee Sang-han's research team from the Department of New Materials Engineering at GIST succeeded in stepwise controlling the dielectric constant by utilizing lattice distortion of perovskite materials, which are used as basic materials for semiconductors.

The dielectric constant is an intrinsic property of materials, but if this dielectric constant can be controlled in dielectric materials, the storage levels of memory devices can be adjusted, thereby dramatically improving the power consumption and information density of existing semiconductor devices.

It has recently been reported through theoretical calculation papers that some dielectric materials with a perovskite (ABO3) structure can undergo a phase transition from paraelectricity to ferroelectricity depending on lattice distortion.

Among them, SrMnO3 (SMO) is a material that can undergo multiple phase transitions not only to ferroelectricity but also to ferromagnetism depending on lattice distortion, and this strong combination of two ferroelectricities has been spotlighted as a highly promising material for next-generation multi-memory devices.

However, in previous studies, when these materials were experimentally realized, it was difficult to directly confirm ferroelectricity and dielectric constant due to large leakage currents and structural defects caused by lattice distortion.

The GIST research team devised and applied a selective oxygen annealing method to overcome these limitations, and experimentally confirmed for the first time in SMO thin films that a phase transition from paraelectricity to ferroelectricity and stepwise control of the dielectric constant according to lattice strain are possible.

They induced lattice strain in SMO by forming crystalline thin films using pulsed laser deposition based on a strontium tantalum aluminum substrate with a larger lattice constant than the SMO thin film. In addition, by adjusting the thickness of the thin film, the lattice strain rate was stepwise controlled up to 2%.

Furthermore, they prepared an SrRuO3 protective layer on the SMO thin film and devised a selective oxygen annealing method that involves annealing in a high-temperature oxygen atmosphere followed by removal of the protective layer. Through this, they solved the large leakage current and structural defects caused by lattice distortion, which were limitations of the SMO thin film, and realized a structurally stable thin film.

Professor Lee Sang-han said, “This research achievement is significant in that it can provide a starting point for the development of memcapacitors, which are attracting attention as next-generation electronic devices but are still at the material development stage,” and added, “The development of dielectric materials that can be stepwise controlled according to lattice strain is expected to lead the development of next-generation semiconductor devices in the future.”

This research, led by Professor Lee Sang-han of GIST and conducted by Dr. Ahn Hyun-ji (first author), was supported by the Future Materials Discovery Project funded by the National Research Foundation of Korea and was selected as a highlight paper in the prestigious materials science journal ‘NPG Asia Materials (IF=10.481)’, published online on October 29, 2021.

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