Benjamin H. Ashmore

An experimental 4 Mb flash EEPROM with sector erase

A 512K*8 flash EEPROM (electrically erasable programmable ROM) which operates from a single 5-V supply was designed and fabricated. A double-poly, single-metal CMOS process with a minimum feature size of 0.9 mu m was developed to manufacture the test vehicle, which resulted in a die size of 95 mm/sup 2/. The storage cell is 8.64 mu m/sup 2/ and consists of a one-transistor cell that uses a remote, scalable, tunnel diode for programming and erasing by Fowler-Nordheim tunneling. Process high-voltage requirements are relaxed by utilizing circuit techniques to alleviate the burden of high voltages. A segmented architecture provides the flexibility to erase any one sector (16 kB) or the entire chip during one cycle by an erase algorithm. The memory can be programmed one byte at a time, or the internal bit-line latches can be used to program a 256-B page in one cycle. A programming time of 10 ms is typical, which results in a write time of 40 mu s/B during page programming. The chip features an access time of 90 ns. >

A 20 ns 1 Mb CMOS burst mode EPROM

A 64-K*16-b burst-mode EPROM (electrically programmable read-only memory) with a 20-ns statistical access time was achieved using 1.4- mu m lithography. An orthogonal x-drive and split array architecture allows efficient array segmentation utilizing a contactless buried diffusion memory cell. The resultant die size is 54.6 mm/sup 2/. The contactless, buried-diffusion memory cell is constructed using a self-aligned thick oxide (SATO) process which minimizes the array dimensions by requiring diffusion contacts only every 16 bits. The SATO array can be continuously biased without a power penalty because of its virtual ground array configuration. In many system applications, the burst mode memory configuration offers performance approaching maximum processor capability.<<ETX>>