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

2. 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 .

3. 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

4. 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

5. 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

6. 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

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

8. 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

9. Analogue Bipolar Processes
Standard npn transistor
Lateral pnp transistor 3D

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

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

12. 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,

13. 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

14. 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.

15. Digital Bipolar Processesn 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.

16. 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

17. Thank You!