Characteristics and scaling properties of n-p-n transistors with a sidewall base contact structure

Symmetrical n-p-n transistors with a sidewall base contact structure (SICOS) are developed and high cutoff frequency of 14 GHz in downward operation and 4 GHz in upward operation were obtained with a small transistor area of 145 µm²for a 3 µm × 4 µm emitter size. This excellent performance is the direct result of the extreme reduction of parasitic regions. Scaling laws of device characteristics are discussed. It is shown that the current gain and transconductance will be lowered in scaled down transistors. Regarding other properties, upward characteristics will be improved more than downward characteristics.