Research progresses of dynamic random access memory devices

Abstract

In this paper, the dynamic random access memory (DRAM) cell technology is introduced and the important technological breakthroughs are reviewed. The criteria of DRAM memory cell design is discussed and the key fabrication technologies of 6F2 memory cell and stack capacitor DRAM cell are summarized. The technological evolution of array access transistor is also reviewed. The transistors with U-shaped transistor or FinFET and the fabrication process flow of 6F2 DRAM chip were discussed. Based upon the technical requirements for DRAM cell, the possible device technologies for the next generation DRAM cell was summarized. It is predicted that (1) U-shape channel transistor will be the mainstream technology for the future DRAM cell beyond 20 nm; (2) low k material will be required for decreasing the bitline parasitic capacitance; (3) sense-amplifier with better signal-noise margin will be required to ease the requirement of high aspect-ratio storage capacitance; (4) low power DRAM design will draw more attention, rather than increasing the storage capacity of DRAM.