Characterization of a Capacitorless DRAM Cell for Cryogenic Memory Applications

A partially depleted silicon-on-insulator MOSFET is analyzed over a wide temperature range from 380K to 80K to characterize memory performance at cryogenic temperatures and verify its feasibility as a cryogenic memory cell. In the Shockley-Read-Hall theory, the generation-recombination rate decreases with decreasing temperature, therefore, the retention properties of the capacitorless single transistor DRAM cell are greatly improved as temperature decreases. The static and dynamic retention times increase sharply as temperature decreases. The dynamic retention time reaches up to ~3.5 s at 80K, which is ~104 times larger than that at 300K. In addition, as the temperature decreases, the current sensing margin also increases more than 2.5 times at 80K (~11 μA) compared to that at 300K, due to the improved dynamic retention characteristics and the increased transconductance.