99 Nm Memory Refresh Time Research And Improvement

The rapid development of integrated circuits, resulting in IC design and manufacturing requirements of smaller and smaller critical dimensions, resulting in a smaller unit area to get more chips, thus reducing costs, improving competitiveness, while improving the performance of the chip and lower power consumption, semiconductor companies to improve their competitiveness one of the main.This paper mainly studies the DRAM from 110nm shrink to 99nm node refresh time (t-Refresh time) improvement. In this paper we mainly take following actions to improve the refresh time:1) Increase the depth of Recessl 500nm to increase the parasitic transistor channel length; 2) Increases the thickness of Collar OX 10A, increasing the thickness of the parasitic transistor gate ox; 3) Increases 37A of the silicon nitride to increase capacitance of the dielectric constant of dielectric layer to improve the capacitance; 4) change the VT IMP condition of CELL MOS part to improve CELL VT to achieve the purpose of reducing the leakage current; 5) increase Node SIN thickness to prevent leakage of charge stored in capacitors and leakage of induced by doping ion diffusion caused the PN junction leakage current; 6) improve the CELL MOS source and drain side of the ion concentration gradient, add addition of new CB3 IMP, reducing junction leakage; 7) improve the active region thickness of the photo resist lithography process, the rough edges of the active region been improved, reducing the active area to the DT leakage current.Base on the experiment results, we have been able to fine tune some of the structure and electrical properties of the MOS parameters, to get the 99nm node, a new generation of products to a acceptable refresh time.Before above process tuning, 99nm DRAM production technology refresh time can not meet customer requirements, product refresh time is only 70-80 ms. Based on the above study,99 nm product refresh time has been improved to 150 ms or more, and been able to pass the CP test and go to mass production.