Active solid-state devices (e.g. – transistors – solid-state diode – Bipolar transistor structure – With emitter region having specified doping concentration...
Reexamination Certificate
2001-04-26
2003-05-06
Thomas, Tom (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Bipolar transistor structure
With emitter region having specified doping concentration...
C257S565000
Reexamination Certificate
active
06559517
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to semiconductor devices and in particular to semiconductor devices for use in amplifiers for high frequency applications.
FIG. 1
depicts a cross section of a conventional BJT
100
. As shown in
FIG. 1
, the conventional BJT
100
is formed on a silicon substrate
102
of a second conductivity type (e.g., N type) upon which an epitaxial layer
104
is deposited. The epitaxial layer
104
may be a second conductivity type and form part of the collector. A base region
106
having a first conductivity type (e.g., P type) is formed in the epitaxial layer
104
. An insulating layer
108
, such as SiO
2
, is formed over the base region
106
. Windows are formed in insulative layer
108
to provide access for metallic connections
110
to the base region and for the emitter region. An emitter region
112
made of polysilicon having a second conductivity type is formed in connection with the base region
106
and an emitter contact
114
is provided. Substrate
102
provides a sub-collector, contact with which may be made from the bottom surface of the substrate. Multiple BJT's
100
may be formed on a common substrate with the subcollectors typically isolated from each other by suitable technology.
A drawback to the conventional BJT
100
is that the whole transistor is fabricated on the subcollector area
102
. Such a design yields high parasitic collector capacitance which results in poor performance of BJT
100
in high frequency applications. The variation of collector capacitance with bias results in poor linearity in power amplification applications.
BRIEF SUMMARY OF THE INVENTION
An exemplary embodiment of the invention is a semiconductor device comprising a substrate of a first conductivity type and a subcollector of a second conductivity type provided on the substrate. An intrinsic epitaxial layer is formed on the substrate. A collector region of the second conductivity type is adjacent the subcollector and a base region of the first conductivity type is adjacent the collector region. An emitter region of the second conductivity type is adjacent the base region and the emitter region has an emitter size. The subcollector and collector region both have a size not substantially greater than the emitter size. An alternate embodiment includes a spacer layer formed between the emitter region and the base region.
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RF Micro Devices Introduces Trio of GaAs HBT Amplifiers, RF Micro Devices, Dec. 11, 2000, pp. 1-2.
HP Offers High Dynamic Range, Low-noise Isolated-collector Silicon Bipolar Junction Transistor for RF Applications, Agilent, Feb. 22, 1999, pp. 1-3.
High Volume Production of AlGaAs/GaAs Heterojunction Bipolar Transistors, N. Pan, D. Hill, C. Rose, D. McCullough, P. Rice,D. P. Vu, Kopin Corp.; K. Hong, C. Farley, Rockwell Semiconductor Systems, Date Unknown, pp. 1-4.
Cantor & Colburn LLP
Owens Douglas W.
Thomas Tom
LandOfFree
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