Naoto Tomita

A 62-ns 16-Mb CMOS EPROM with voltage stress relaxation technique

To meet the increasing demand for higher-density and faster EPROMs, a 16-Mb CMOS EPROM has been developed based on 0.6- mu m N-well CMOS technology. In scaled EPROMs, it is important to guarantee device reliability under high-voltage operation during programming. By employing internal programming-voltage reduction and new stress relaxation circuits, it is possible to keep an external programming voltage V/sub pp/ of 12.5 V. The device achieves a 62-ns access time with a 12-mA operating current. A sense-line equalization and data-out latching scheme, made possible by address transition detection (ATD), and a bit-line bias circuit with two types of depletion load led to the fast access time with high noise immunity. This 16-Mb EPROM has pin compatibility with a standard 16-Mb mask-programmable ROM (MROM) and is operative in either word-wide or byte-wide READ mode. Cell size and chip size are 2.2 mu m*1.75 mu m and 7.18 mm*17.39 mm, respectively. >

A 3.3 V-only 16 Mb flash memory with row-decoding scheme

A 3.3 V only 16 M flash memory with a row decoding scheme is fabricated in 0.4 /spl mu/m double-well double-metal CMOS. Negative-gate-biased erase enables 3.3 V-only operation, and a double-word-line structure with second aluminum minimizes word-line delay. Row redundancy with self-convergence improves yield. Quasi-differential sensing with address transition detection gives fast random access.

Optimum redundancy design for new-generation EPROMs based on yield analysis of previous generation

Failure modes of 4 Mbit EPROMs have been analyzed, and the model to formulate them is proposed. The redundancy scheme of a 16 Mbit EPROM was optimized by the model in consideration of area penalty. In applying the 4 Mbit data to 16 Mbit EPROM, fabrication line improvement was taken into account. The actual data of 16 Mbit EPROM failure analysis indicate the effectiveness of the prediction. The 16 Mbit EPROM has 2 rows*8 blocks redundancy, and the redundancy gives the highest yield in the time when the mass production begins.<<ETX>>