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Masato IWABUCHI Masami USAMI Masamori KASHIYAMA Takashi OOMORI Shigeharu MURATA Toshiro HIRAMOTO Takashi HASHIMOTO Yasuhiro NAKAJIMA
An 18-kb RAM with 9-kgate control logic gates operating during a cycle-time of 1.5 ns has been developed. A pseudo-dual-port RAM function is achieved by a two-bank structure and on-chip control logic. Each bank can operate individually with different address synchronizing the single clock. A sense-amplifier with a selector function reduces the reading propagation time. Bonded SOI wafers reduce the memory-cell capacitance, and this results in a fast write cycle without sacrificing α-particle immunity. The chip is fabricated in a double polysilicon self-aligned bipolar process using trench isolation. The minimum emitter size is 0.52 µm2 and the chip size is 1111 mm2.
Hiroaki NAMBU Kazuo KANETANI Youji IDEI Toru MASUDA Keiichi HIGETA Masayuki OHAYASHI Masami USAMI Kunihiko YAMAGUCHI Toshiyuki KIKUCHI Takahide IKEDA Kenichi OHHATA Takeshi KUSUNOKI Noriyuki HOMMA
An ultrahigh-speed 72-kb ECL-CMOS RAM macro for a 1-Mb SRAM with 0.65-ns address-access time, 0.80-ns write-pulse width, and 30.24-µm2 memory cells has been developed using 0.3-µm BiCMOS technology. Two key techniques for achieving ultrahigh speed are an ECL decoder/driver circuit with a BiCMOS inverter and a write-pulse generator with a replica memory cell. These circuit techniques can reduce access time and write-pulse width of the 72-kb RAM macro to 71% and 58% of those of RAM macros with conventional circuits. In order to reduce crosstalk noise for CMOS memory-cell arrays driven at extremely high speeds, a twisted bit-line structure with a normally on MOS equalizer is proposed. These techniques are especially useful for realizing ultrahigh-speed, high-density SRAM's, which have been used as cache and control storages in mainframe computers.