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本文描述了采用分开的工艺过程来形成有源基区和无源基区的一种改进的微波晶体管结构。在这种结构中,由于采用重掺杂的无源基区具有小的薄层电阻,所以可以得到低的基区电阻,又由于无源基区的横向扩散,因而减小了发射极的有效宽度。同时,用离子注入形成的有源基区可以独自取得最佳化,以改进电流增益截止频率。具有改进结构的晶体管,与具有同样几何图形但用通常双扩散工艺所制造的晶体管相比,在4千兆赫下,前者的噪声系数为2.3分贝,后者为3.6分贝。
Described herein is an improved microwave transistor architecture using separate processes for forming active base and passive base regions. In this structure, since the heavily doped passive base region has a small sheet resistance, a low base resistance can be obtained and the emitter is effectively reduced due to the lateral diffusion of the passive base region width. At the same time, the active base region formed by ion implantation can be optimized alone to improve the current gain cut-off frequency. Transistors with an improved structure have a noise figure of 2.3 dB at 4 GHz and a gain of 3.6 dB at the latter compared to transistors of the same geometry but manufactured by the usual double diffusion process.