Physics of Semiconductor Devices 6.7 Analogue Bipolar Processes 6.8 Digital Bipolar Processes Liu Yunlong

Analogue Bipolar Processes ※ Bipolar process is widely used today for the design and fabrication of analogue integrated circuits. We will begin our consideration of bipolar process by studying a simple example .

Analogue Bipolar Processes Starting materials of (100) or (111) orientation Oxidized to produce about 0.5μm of thermal oxide Define the buried layer Photolithography—implant arsenic(砷) or antimony(锑) (n+ region) A high –temperature drive-in

Analogue Bipolar Processes Ion Implanted(B+) to form the P buried layer Remove the silicon dioxide masking layer Deposite an n-type epitaxial layer(10μm ) on the silicon surface to form the collector

Analogue Bipolar Processes Grow a new silicon dioxide layer over the entire wafer Define the collector upon the buried layer A high –temperature drive-in Remove the silicon dioxide layer and grow a new one

Analogue Bipolar Processes A boron implant is used to produced an extrinsic base A high –temperature drive-in to grow a thermal oxide over the base Photolithography and define the base and isolations An Ion (B+) implantation is used

Analogue Bipolar Processes A high –temperature drive-in for diffusion Photolithography and define the emitter

Analogue Bipolar Processes Photolithography and define the contact windows Evaporate a layer of aluminium over the entire wafer and define the metal connections B E C Process in a low-temperature alloy in a H2/N2 ambient for low-resistance Ohmic cantacts

Analogue Bipolar Processes Standard npn transistor Lateral pnp transistor 3D

Analogue Bipolar Processes Resistor fabrication by bipolar transistor process A base resistor A pinch resistor 200Ω/sq 10KΩ/sq

Analogue Bipolar Processes A metal-oxide-semiconductor capacitor by bipolar transistor process SiO2 Emitter diffusion

Thin Film Silicon-On-Insulator of Bipolar Junction Transistor Osama S Hammad et. al. / International Journal of Engineering Science and Technology Vol. 2(5), 2010, 1037-1046

Digital Bipolar Processes ※ Advances in silicon bipolar technology have led to a considerable improvement in digital circuit performance. A variety of digital circuits have also been designed on high-speed bipolar process. These impressive results have been made possible by the evolution of self-aligned fabrication techniques for bipolar process. The advantages of the self-aligned bipolar transistor versus the conventional oxide-isolated transistors: ◆Reduction of the base resistance ◆Reduction of the collector/base capacitance

Digital Bipolar Processes ▼Reduction of the base resistance: The reduced base resistance is obtained because the p+ extrinsic base is self-aligned to the polysilicon emitter. These two regions of the device are separated by the thickness of the oxide spacer, which is typically less than 0.4μm. The extrinsic base region therefore extends right up to the edge of the active emitter, thereby providing avery low-resistance path to the base contact.

Digital Bipolar Processes n n+ ▼Reduction of the collector/base capacitance: In the self–aligned transistor contact to the base is made via the p+ polysilicon layer, and hence there is no requirement for a contact between metal and single- crystal silicon. This means that the recessed oxide isolation regions can be brought closer together, which makes possible a reduction in the collector/base capacitance.

Digital Bipolar Processes H.GOTO, JOURNAL DE PHYSIQUE ,Colloque C4, suppl6ment au n09, Tome 49, septembre 1988 Bipolar Process Engineering Department, Fuj i t su ~ i m i t e d ,1 015, Kamikodanaka, Nakahara, Kawasaki 211, Japan

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