Title :
Threshold voltage-related soft error degradation in a TFT SRAM cell
Author :
Ikeda, Shuji ; Yoshida, Yasuko ; Kamohara, Shiro ; Imato, Koichi ; Ishibashi, Koichro ; Takahashi, Kazuo
Author_Institution :
Trecenti Technol. Inc., Ibaraki, Japan
Abstract :
This is the first report of abnormal behavior in the soft error rate (SER) dependence on supply voltage (Vcc) for a bottom-gated polysilicon PMOS thin-film transistor (TFT) static random access memory (SRAM). We found that the TFT SER does not continuously improve (as is expected and desirable) with increasing Vcc when Vcc exceeds -Vth (threshold voltage) of the TFT within a range of about 0-2 V. This was confirmed with samples of TFT with Vth intentionally varied from 0 to -5 V (by adjusting channel doping). A possible explanation of this Vcc independence is proposed in the form of a SPICE simulation with as little as a 0.1-V TFT transient Vth shift due to the TFT´s floating body. The accelerated SER was measured by using an Americium alpha particle source.
Keywords :
CMOS memory circuits; SRAM chips; alpha-particle effects; errors; thin film transistors; -5 to 2 V; NMOS SRAM driver; SER dependence; SPICE simulation; TFT SRAM; TFT SRAM cell; TFT threshold voltage; alpha particles; bottom-gated polysilicon PMOS TFT; floating body; soft error; soft error rate dependence; static random access memory; supply voltage; thin-film transistor SRAM; threshold voltage-related soft error degradation; Acceleration; Degradation; Doping; Error analysis; Particle measurements; Random access memory; SPICE; SRAM chips; Thin film transistors; Threshold voltage;
Journal_Title :
Electron Devices, IEEE Transactions on
DOI :
10.1109/TED.2002.808449
