X-Band SiGe-MMIC Low Noise Amplifier Using Low Parasitic Capacitance Via Holes for Emitter Grounding

An X-band SiGe-MMIC single-ended two-stage low noise amplifier (LNA) using low parasitic capacitance via holes for the emitter grounding is described. In order to obtain low impedance emitter/source ground of a silicon based single-ended amplifier, we have developed via holes which can be fabricated after the 0.35 mum SiGe-BiCMOS process. Since there are low resistivity epitaxial layers in the silicon substrate, the via hole has the large parasitic capacitance. By introducing deep trench isolations to separate the epitaxial layers around a via hole from the other area of the chip, the parasitic capacitance of a via hole can be reduced. A fabricated X-band single-ended two-stage LNA using the developed low parasitic capacitance via holes shows a gain of 21 dB, a noise figure of 4.8 dB, an IP1dB of -26 dBm at 11 GHz. The power dissipation of the circuit is 19.1 mW at a 3.3 V supply voltage. The developed via holes can be useful for the silicon MMICs at the high frequency of X-band