View source for BiCMOS

{{short description|Semiconductor technology}}
{{redirect-distinguish|BiMOS|BIMOS|Bimo (disambiguation)}}
{{more citations needed|date=January 2017}}
'''Bipolar CMOS''' ('''BiCMOS''') is a [[semiconductor]] technology that integrates two [[semiconductor]] technologies, those of the [[bipolar junction transistor]] and the [[CMOS]] (complementary [[metal–oxide–semiconductor]]) [[logic gate]], into a single [[integrated circuit]].<ref>{{cite thesis |chapter-url=http://www.iue.tuwien.ac.at/phd/puchner/node47_app.html |chapter=5.2 BiCMOS Process Technology |first=H. |last=Puchner |title=Advanced Process Modeling for VLSI Technology |year=1996 |type=PhD |publisher=Institut für Mikroelektronik, Technischen Universität Wien |url=http://www.iue.tuwien.ac.at/phd/puchner |id=TUW-101186}}</ref><ref>{{harvnb|Puchner|1996|loc=[http://www.iue.tuwien.ac.at/phd/puchner/node48_app.html 5.2.1 BiCMOS Process Flow]}}</ref> In more recent times the bipolar processes have been extended to include high mobility devices using [[silicon–germanium]] junctions.
Bipolar [[Transistor|transistors]] offer high speed, high gain, and low [[output impedance]] with relatively high power consumption per device, which are excellent properties for high-frequency analog [[amplifiers]] including low noise [[radio frequency]] (RF) amplifiers that only use a few active devices, while CMOS technology offers high [[input impedance]] and is excellent for constructing large numbers of low-[[electric power|power]] [[logic gate]]s. In a BiCMOS process the [[Doping (semiconductor)|doping]] profile and other process features may be tilted to favour either the CMOS or the bipolar devices. For example [[GlobalFoundries]] offer a basic 180&nbsp;nm BiCMOS7WL process and several other BiCMOS processes optimized in various ways.<ref>{{cite web |last= |first= |date= |title=High-performance SiGe BiCMOS solutions |url=https://gf.com/sites/default/files/sige_hp_pb_2020-0212web.pdf |url-status=dead |archive-url=https://web.archive.org/web/20211130165636/https://www.globalfoundries.com/sites/default/files/sige_hp_pb_2020-0212web.pdf |archive-date=November 30, 2021 |access-date= |website= |publisher=Global Foundries |quote=}}</ref> These processes also include steps for the deposition of precision [[Resistor|resistors]], and high Q RF [[Inductor|inductors]] and [[Capacitor|capacitors]] on-chip, which are not needed in a "pure" CMOS logic design.
BiCMOS is aimed at [[Mixed-signal integrated circuit|mixed-signal ICs]], such as [[Analog-to-digital converter|ADCs]] and complete [[software radio]] [[System on a chip|systems on a chip]] that need amplifiers, [[analog electronics|analog]] [[power management]] circuits, and logic gates on chip. BiCMOS has some advantages in providing digital interfaces. BiCMOS circuits use the characteristics of each type of transistor most appropriately. Generally this means that high current circuits such as on chip power regulators use [[metal–oxide–semiconductor field-effect transistor]]s (MOSFETs) for efficient control, and 'sea of logic' use conventional CMOS structures, while those portions of specialized very high performance circuits such as [[Emitter-coupled logic|ECL]] dividers and [[Low-noise amplifier|LNAs]] use bipolar devices. Examples include RF oscillators, [[bandgap]]-based references and low-noise circuits.{{Citation needed|date=February 2008}}
The [[SuperSPARC]], [[Intel P5|Pentium]] and [[Pentium Pro]] [[Microprocessor|microprocessors]] also used BiCMOS, but starting with [[Pentium II]], designed with increasingly smaller (0.35μm) processes and operating at lower voltages, bipolar transistors ceased to offer performance advantages for this sort of application and were removed.<ref>{{cite book | page=277 | title=CMOS VLSI Design: A Circuits and Systems Perspective | author1=Neil H. E. Weste | author2=David Money Harris | edition=4th | year=2010}}</ref>
== Disadvantages ==
{{speculation section|date=August 2023}}
Some of the advantages of CMOS fabrication, for example very low cost in mass production, do not transfer directly to BiCMOS fabrication.  An inherent difficulty arises from the fact that optimizing both the BJT and MOS components of the process is impossible without adding many extra fabrication steps and consequently increased process cost and reduced yield.  Finally, in the area of high performance logic, BiCMOS may never offer as low a power consumption as a foundry process optimized for CMOS alone, due to the potential for higher standby leakage current.
==References==
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{{Logic Families}}
{{Electronic components}}
[[Category:Logic families]]
[[Category:Integrated circuits]]
[[Category:MOSFETs]]