Dopingless 1T DRAM: Proposal, Design, and Analysis

In this paper, we have proposed a dopingless 1T DRAM (DL-DRAM) that utilizes the charge plasma concept. The proposed device employs a misaligned double-gate architecture to store holes and differentiates between the two logic states. The source, drain, backgate, and frontgate workfunctions are optimized to achieve the required concentration profiles in an intrinsic silicon body. Using TCAD simulations, we have analyzed the read/write mechanism in the device. Our study shows that the mechanism of current transport during reading operation depends strongly on the source workfunction. When the source workfunction is less than 4.5 eV the transport mechanism during reading is dominated by drift-diffusion. However, when the source workfunction is greater than 4.5 eV , the transport mechanism during read is dominated by band-to-band tunneling (BTBT). In general, when the dominant mechanism of current transport is BTBT, the retention time and the read-1/0 current ratio is higher, and the sense margin is lower in the case in which the dominant mechanism of current transport is drift-diffusion. Due to the avoidance of doping, the proposed DL-DRAM is expected to be free from random dopant fluctuation. Moreover, high temperature annealing processes required after ion implantation can be avoided. The lower thermal requirements of a DL-DRAM opens the possibility of fabricating DRAMs using processes which are compatible with bio-materials and opto-electronics and in ensuring bottom MOSFET and interconnects preservation in 3D VLSI integration.