Double-Gate Junctionless 1T DRAM With Physical Barriers for Retention Improvement

• Published in: IEEE transactions on electron devices 2020-04, Vol.67 (4), p.1471-1479
• Main Authors: Ansari, Md. Hasan Raza, Navlakha, Nupur, Lee, Jae Yoon, Cho, Seongjae
• Format: Article
• Language: English
• Subjects: Barriers; Capacitors; Double-gate (DG) junctionless (JL) transistor; Dynamic random access memory; Elongated structure; Junctions; Logic gates; one-transistor dynamic random-access memory (1T DRAM); physical barrier; Random access memory; Retention; retention time; Semiconductor devices; Semiconductor process modeling; Silicon; temperature effect; Temperature effects; Thickness; Topology; Transistors
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2020.2976638

In this article, a double-gate (DG) junctionless (JL) transistor with physical barriers is proposed for one-transistor dynamic random-access memory (1T DRAM) application. In this topology, the holes are stored in the region blocked by physical barriers constructed by oxides underneath the source and drain regions rather than a potential well formed by n + -p-n + as in the conventional structures. The proposed topology achieves an elongated retention time ( {T}_{\text {ret}} ) with larger physical barrier thickness ( {T}_{\text {oxPB}} ) and wider barrier offset length ( {L}_{\text {BO}} ) due to a reduction in band-to-band tunneling (BTBT) (during hold "0") and recombination (during hold "1"). Maximum retention times of ~2.5 s and ~33 ms have been achieved for channel doping of 10 19 cm −3 at 27 °C and 85 °C, respectively, with gate length ( {L}_{g} ) of 100 nm at small drain bias ( {V}_{\text {DS}} ) of 1 V during write "1." Results demonstrate a better gate length scalability and a retention time of ~4 ms at {L}_{g} of 15 nm with thinner Si channel thickness under the gate ( {T}_{\text {Si}} ) and thicker {T}_{\text {oxPB}} . In addition, the effect of temperature on retention time has been analyzed. With optimized {T}_{\text {oxPB}} at {L}_{g} = {100} nm, the retention time decreases due to thermal generation and recombination from ~2.5 s at 27 °C to ~3 ms at 125 °C.