The development of highly stackable oxide-semiconductor channel transistors, which would make high-density, low-power 3D DRAM feasible by Kioxia Corporation. This technology, which was introduced at the IEEE International Electron Devices Meeting (IEDM) on December 10 in San Francisco, USA, has the potential to lower power consumption in a variety of applications, such as IoT components and AI servers.
Demand for DRAM with larger capacity and lower power consumption that can handle massive volumes of data is rising in the AI era. The physical limits of memory cell size scaling are being reached by conventional DRAM technology, which is driving research into 3D stacking of memory cells to increase capacity.
Conventional DRAM uses single-crystal silicon as the channel material for transistors in stacked memory cells, which raises manufacturing costs and increases the power needed to refresh the memory cells in proportion to memory capacity.
We presented Oxide-Semiconductor Channel Transistor DRAM (OCTRAM) technology, which uses vertical transistors composed of oxide-semiconductors, at the IEDM last year.
The company demonstrated  the technique of highly stackable oxide-semiconductor channel transistors in this year’s presentation, enabling 3D stacking of OCTRAM and confirming the functionality of transistors layered in eight layers.
In order to simultaneously form vertical layers of horizontally stacked transistors, this novel approach stacks mature silicon-oxide and silicon-nitride films and substitutes an oxide-semiconductor (InGaZnO) for the silicon-nitride region. Additionally, we have shown a new 3D memory cell structure that can scale the vertical pitch. The economic obstacles of creating 3D stacking of memory cells are anticipated to be overcome by these manufacturing techniques and structures.
Additionally, it is anticipated that the low off-current properties of oxide-semiconductors will enable a reduction in refresh power.
For the horizontal transistors formed by the replacement process, the company states to have shown high on-current (more than 30?A) and ultra-low off-current (less than 1aA, 10^-18A) capabilities. Additionally, Kioxia has successfully fabricated an 8-layer stack of horizontal transistors and verified that the transistors inside that structure operate as intended.
