Effect of Bottom SiN Thickness for AlGaN/GaN Metal–Insulator–Semiconductor High Electron Mobility Transistors Using SiN/SiO2/SiN Triple-Layer Insulators

概要

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We fabricated AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs) using SiN/SiO2/SiN triple-layer insulators. Our MIS-HEMTs are mechanically stable in the sub-50-nm-gate region and free from damage caused by dry etching. We fabricated two kinds of MIS-HEMTs with different bottom SiN thickness $d_{\text{B{\_}SiN}}$, i.e., 2.5 and 5 nm. We reduced gate length $L_{\text{g}}$ down to 25 nm. For the MIS-HEMTs with a $d_{\text{B{\_}SiN}}$ of 5 nm, a cutoff frequency $ f_{\text{T}}$ at $L_{\text{g}}=35$ nm starts to decrease with reducing $L_{\text{g}}$. On the other hand, we obtained a maximum $ f_{\text{T}}$ of 145 GHz for a 35-nm-gate MIS-HEMT with a $d_{\text{B{\_}SiN}}$ of 2.5 nm. Moreover, the $ f_{\text{T}}$ at $L_{\text{g}}=25$ nm is almost same as that at $L_{\text{g}}=35$ nm. These results indicate that the short-channel effects are suppressed by decreasing $d_{\text{B{\_}SiN}}$ to be 2.5 nm. The threshold voltages also indicate the suppression of the short-channel effects by decreasing $d_{\text{B{\_}SiN}}$.
INSTITUTE OF PURE AND APPLIED PHYSICSの論文
2006-07-25