1.4 The journey of i.c.technology from micro (1959) to nano (2009  (Page 49/2)

The Journey of I.C.Technology from micro (1959) to nano (2009) era.-Part 4.

Title:Part 4 of 50 yrs journey.

Keywords:Band-gap narrowing,BiCMOS,PolySi Emitter,Surface Recombination Velocity, Metal Silicide, base spreading resistance;

Summary: Part 4 of 50 years journey;

Section IV. The development in Bipolar Junction Transistor Structure over last 50 years for meeting the challenges of Post Industrial Society.

(“Transistor Design and Application Considerations for ≥200GHz SiGe HBT”, Grey Freeman et al, IEEE Transactions on ED, Vol 50,No.3, March 2003, pp.645-655)

BJT has historically been faster than MOSFET. FET depends on leading edge lithographic dimensions(45nm) but BJT depends on vertical base widths which has reached 10nm. BJT has structural flexibilities in minimizing the parasitic. It has higher transconductance, high self gain, low 1/f flicker noise and better V _BE matching. All these factors make BJT the device of choice for demanding applications. Today SiGe HBT are surpassing GaAs HBT . SiGe depends on more conventional Si Technology whereas GaAs depends on Molecular Beam Epitaxy which has a much higher overhead cost. So combination of HBT and CMOS, known as BiCMOS, with a large menu of passive devices such as R,C,L, Varactor Diode, and low loss transmission lines opens numerous possibilities and cost effective ways of realizing systems which cannot be achieved by GaAs ICs. BiCMOS reduces the cost of mobile consumer products, advance high BW wireless communication and collision-avoidance automobile radar. BiCMOS lead to VLSI, ASIC&Si based RF SOC solution. Hence SiGe/SiGeC is becoming the technology of future.

Growth of Personal Computers kept CMOS in limelight and fueled the CMOS scaling in 70s. Today the growth of INTERNET, high speed communication that converges data, video and audio and the growth of mobile communication has sharply brought in focus the need for cheap, high speed and low power devices. SiGe HBT is a major candidate for the needs of New Communication. DSP and DSP&Real World Interface are at the heart of INTERNET, so developing System on Chip (SOC) and integration of digital and Analog/RF function became the high priority area of research. Since advanced SiGe Process shrinks features and boosts performance it became the technology of choice for implementing 24GHz radar for blindside detection, for 77GHz radar system for automobile collision warning or advance cruise control, for 60Ghz Wi-Fi chips for next generation wireless LAN and backbone networks , for software defined radios, for cellular handset and for high frequency automatic test equipments.

The emergence of high performance SiGe Technology tailored for low voltage, low power RF&mixed signal applications has shown great potentials for microwave and mm wave applications.

IV.1. The relation between the physical parameters and performance parameters and Physics of High Performance nano BJT.

The carrier concentration profile in a forward biased diode is shown in Appendix III. As discussed in the Appendix III, in olden times EB junction was like a wide base diode but with dimension scaling and improvement in technology, EB junction became shallow and hence narrow base diode. In a narrow base diode the emitter surface contact is decisive in determining the resultant emitter injection efficiency. As shown in Figure 4, metal contact directly to pure single crystal emitter portion causes a poorer injection efficiency as compared to that where metal contact and n+ pure Silicon has heavily doped poly-Silicon emitter sandwiched between the two layers.