ETRI Develops Next-Generation DRAM Structure Without Electrical Storage Device

A Korean research team has developed a next-generation memory (DRAM) structure capable of reliably storing data without the need for electrical storage. This achievement is drawing attention as it advances the essential 'low-power, high-density' memory technology required in the age of artificial intelligence (AI).

The Electronics and Telecommunications Research Institute (ETRI) announced on April 14 that it has developed a '2T0C (2-Transistor-0-Capacitor)' DRAM structure that stores data without using a capacitor.

The ETRI research team is depositing an oxide semiconductor. Korea Electronics and Telecommunications Research Institute

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A capacitor is a small storage space for electricity. As semiconductor sizes shrink, it becomes more difficult to manufacture capacitors, leading to increased power consumption. This has created a need for a new memory structure that eliminates the capacitor.

However, most DRAMs currently in commercial use employ a 1T1C structure, where one transistor and one capacitor work together to store data, making it difficult to remove the capacitor from the semiconductor. Previous research also failed to find a decisive solution, as eliminating the capacitor resulted in difficulties maintaining data for extended periods or led to decreased stability.

To address these issues, ETRI applied oxide semiconductor transistors (TFTs), commonly used in the display industry, to develop the 2T0C DRAM structure. By using oxide semiconductors-which are well-suited for memory devices due to their low leakage current and ability to stably retain charge-ETRI produced this result.

The 2T0C DRAM developed using this approach is being evaluated as an alternative capable of overcoming the structural limitations of conventional silicon-based DRAM.

First, ETRI fabricated transistors using aluminum-doped indium-tin-zinc oxide (ITZO) material and precisely controlled internal defects via a nitrous oxide (N2O) plasma process. This allowed them to reduce device defects and effectively suppress leakage current. Additionally, they optimized the channel width-to-length ratio (W/L) of the read transistor to prevent stored charge from dissipating easily.

As a result, the 2T0C DRAM was able to retain data for over 1,000 seconds, and the memory window-representing the range in which data can be clearly distinguished as '0' or '1'-improved by approximately 13 times. This means data can be stored for longer periods and with greater accuracy.

In particular, ETRI not only succeeded in extending data retention time but also improved the stability of memory operation, setting this work apart from previous research.

This study goes beyond the structural limitations of traditional silicon-based DRAM technology, presenting new possibilities for memory technology and marking an important turning point in the development of high-density, low-power memory technology.

Sooji Nam, Ph.D., from the Flexible Electronic Device Research Laboratory at ETRI, said, "This research confirms that oxide semiconductor technology, which has been developed in the display field, can also be applied to next-generation memory devices. ETRI expects that the 2T0C DRAM will play a crucial role in the implementation of three-dimensional semiconductor integration technology and low-power computing systems moving forward."

Meanwhile, this research was carried out with Chahwan Yang, a master's student at the ETRI campus of the University of Science and Technology (UST), as the first author, and Dr. Sooji Nam of ETRI as the corresponding author.

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