Design of a Capacitorless Dynamic Random Access Memory Based on Ultra-Thin Polycrystalline Silicon Junctionless Field-Effect Transistor with Dual-Gate

Abstract

In this paper, a 1T-DRAM based on the junctionless field-effect transistor (JLFET) with an ultrathin polycrystalline silicon layer was designed and investigated by using technology computer-aided design simulation (TCAD). The application of a negative voltage at the control gate results in the generation of holes in the storage region by the band-to-band tunneling (BTBT) effect. Memory characteristics such as sensing margin and retention time are affected by the doping concentration of the storage region, bias condition of the program, and length of the intrinsic region. In addition, the gate acts as a switch that controls the transfer characteristics while the control gate plays a role in retaining holes in the hold state. The device was optimized, considering various parameters such as the doping concentration of the storage region (Nstorage), intrinsic region length (Lint), and operation bias conditions to obtain a high sensing margin of 49.7 μA/μm and a long retention time of 2 s even at a high temperature of 358 K. The obtained retention time is almost 30 times longer than that predicted for modern DRAM cells by the International technology roadmap for semiconductors (ITRS).

Bulk-fin field-effect transistor-based capacitorless dynamic random-access memory and its immunity to the work-function variation effect

“…Note that most 1T-DRAMs store holes in the body region near the metal gate. [20][21][22][23][24][25] However, the proposed JL bulk-FinFETbased 1T-DRAM device stores holes in H body-fin rather than H fin , as shown in Fig. 5(a).…”

“…This side effect is one of the critical issues encountered in the implementation of the HK/MG technology, and it not only affects logic transistors but also influences memory transistors. [20][21][22][23][24][25] So far, a few studies on WFV have been reported in the literature; [12][13][14][15][16][17][18][19] however, the impact of WFV on memory characteristics is yet to be investigated. Recently, Lee et al studied and investigated the effect of WFV on the transfer characteristics and memory performance of a gate-all-around junctionless (JL) field-effect transistor-based capacitorless dynamic random-access memory (1T-DRAM).…”