IN-SITU PHOSPHORUS-DOPED POLYSILICON EMITTER TECHNOLOGY FOR VERY HIGH-SPEED, SMALL EMITTER BIPOLAR-TRANSISTORS

In situ phosphorus-doped polysilicon emitter (IDP) technology for very high-speed, small-emitter bipolar transistors is studied. The device characteristics of IDP transistors are evaluated and compared with tho se of conventional ion-implanted polysilicon emitter transistors, IDP technology is used to fabricate double polysilicon self-aligned bipola r transistors and the I-V characteristics, current gain, transconducta nce, emitter resistance, and cut-off frequency are measured, In conven tional transistors, these device characteristics degrade when the emit ter is small because of the emitter-peripheral-thick-polysilicon effec t. In IDP transistors, the peripheral effect is completely suppressed and large-grain, high-mobility polysilicon can be used, The device cha racteristics, therefore, are not degraded in sub-0.2-mu m emitter tran sistors, In addition, large-grain, high-mobility, and high-phosphorus concentration IDP films increase current gain and lower emitter resist ance, The use of IDP technology to build very small emitter transistor s is evaluated and discussed.