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Soft-Error Study of DRAMs with Retrograde Well Structure by New Evaluation Method
Yoshikazu OHNO Hiroshi KIMURA Ken-ichiro SONODA Tadashi NISHIMURA Shin-ichi SATOH Hirokazu SAYAMA Shigenori HARA Mikio TAKAI Hirokazu MIYOSHI
IEICE TRANSACTIONS on Electronics
Publication Date: 1994/03/25
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Quarter Micron Si Device and Process Technologies)
Category: Device Technology
soft-error, DRAM, microprobe, proton, mapping,
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A new method for the DRAM soft-error evaluation was developed. By using a focused proton microprobe as a radiation source, and scanning it on a memory cell plane, local sensitive structure of memory cells against soft-errors could be investigated with a form of the susceptibility mapping. Cell mode and bit-line mode soft-errors could be clearly distinguished by controlling the incident location and the proton dose, and it was also found that the incident beam within 4 µm around the monitored memory cell caused the soft-error. The retrograde well formed by the MeV ion implantation technology was examined by this method. It was confirmed that the B+ layers in the retrograde well were a sufficient barrier against the charge collection. The generation rate of the electron-hole pairs and the charge collection into n+ layers with a retrograde well and a conventional well were estimated by the device simulator, and were explained the experimental results.