IEDM: Kioxia Develops OCTRAM (Oxide-Semiconductor Channel Transistor DRAM) Technology

Kioxia Corporation announced the development of OCTRAM (Oxide-Semiconductor Channel Transistor DRAM), a new type of 4F² DRAM, comprised of an oxide-semiconductor transistor that has a high ON current, and an ultra-low OFF current, simultaneously.

Fig.1 Cross sectional Tem image for  Ingazno vertical transistor

This technology is expected to realize a low power DRAM by bringing out the ultra-low leakage property of the InGaZnO ⁽¹⁾ transistor. This was 1st announced at the IEEE International Electron Devices Meeting (IEDM) held in San Francisco, CA on December 9, 2024. This achievement was jointly developed by Nanya Technology Corp. and Kioxia Corporation. This technology has the potential to lower power consumption in a wide range of applications, including AI and post-5G communication systems, and IoT products.

The OCTRAM utilizes a cylinder-shaped InGaZnO vertical transistor (Fig.1) as a cell transistor. This design enables the adaptation of a 4F² DRAM, which offers significant advantages in memory density compared to the conventional silicon-based 6F² DRAM.

Fig.2 (a)on and (b)off current properties for developed Ingazno transistor

The InGaZnO vertical transistor achieves a high ON current of over 15μA/cell (1.5 x 10^-5 A/cell) and an ultra-low OFF current below 1aA/cell (1.0 x 10^-18 A/cell) through device and process optimization (Fig.2). In the OCTRAM structure, the InGaZnO vertical transistor is integrated on top of a high aspect ratio capacitor (capacitor-first process).

Fig.3 Panoramic view of Octram

This arrangement allows for the decoupling of the interaction between the advanced capacitor process and the InGaZnO performance (Fig.3).

⁽¹⁾ InGaZnO is a compound of In(indium), Ga(gallium), Zn(zinc), and O(oxygen)