A 126.6 mm/sup 2/ AND-type 512 Mb flash memory with 1.8 V power supply

A 512-Mb flash memory, which is applicable to removable flash media of portable equipment such as audio players, has been developed. The chip is fabricated with a 0.18-/spl mu/m CMOS process on a 126.6-mm/sup 2/ die, and uses a multilevel technique (2 bit/1 cell). The memory cell is AND-type, which is suitable for multilevel operation. This paper reports new techniques adopted in the 512-Mb flash memory. First, techniques for low voltage operation are described. The charge pump, control of pumps, and the reference voltage generator are improved to generate internal voltage stably for multilevel flash memory. Next, a method for reducing total memory cost in the removable flash media is described. A new operation mode named read-modify-write is introduced on the chip. This feature makes the memory system simple, because the controller does not have to track sector-erase information.