Redundancy Technique for Ultra-High-Speed Static RAMs

Hiroaki NAMBU  Kazuo KANETANI  Youji IDEI  Kunihiko YAMAGUCHI  Toshirou HIRAMOTO  Nobuo TAMBA  Kunihiko WATANABE  Masanori ODAKA  Takahide IKEDA  Kenichi OHHATA  Yoshiaki SAKURAI  Noriyuki HOMMA  

IEICE TRANSACTIONS on Electronics   Vol.E76-C   No.4   pp.641-648
Publication Date: 1993/04/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Integrated Electronics
redundancy technique,  static RAM (SRAM),  focused ion beam (FIB),  laser chemical vapor deposition (L-CVD),  access time,  

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A new redundancy technique especially suitable for ultra-high-speed static RAMs (SRAMs) has been developed. This technique is based on a decoding-method that uses two kinds of fuses without introducing any additional delay time. One fuse is initially ON and can be turned OFF afterwards, if necessary, by a cutting process using a focused ion beam (FIB). The other is initially OFF and can be turned ON afterwards by a connecting process using laser chemical vapor deposition (L-CVD). This technique is applied to a 64 kbit SRAM having a 1.5-ns access time. The experimental results obtained through an SRAM chip repaired using this redundancy technique show that this technique does not introduce any increase in the access time and does not reduce the operational margin of the SRAM.