Active solid-state devices (e.g. – transistors – solid-state diode – Bipolar transistor structure
Reexamination Certificate
2001-12-10
2004-03-09
Thomas, Tom (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Bipolar transistor structure
C257S273000, C257S197000, C257S370000, C257S378000, C257S477000, C257S511000, C257S517000, C257S552000, C257S556000, C257S565000, C257S573000, C257S584000, C257S591000, C257S581000, C257S561000, C257S560000, C257S563000, C257S577000, C257S578000, C257S590000, C438S205000, C438S213000, C438S340000
Reexamination Certificate
active
06703685
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to integrated circuit fabrication, and, more specifically, the present invention relates to the fabrication of a super self-aligned collector for a bipolar junction transistor device design and process flow that allows for a compact bipolar junction transistor layout.
BACKGROUND OF THE INVENTION
Description of Related Art
A bipolar junction transistor (BJT) exhibits significant resistance and substrate capacitance that raise performance issues. In high-performance bipolar complementary metal oxide semiconductor (BiCMOS) processing the process flow needs to be integrated. The addition of high energy, high dose implantation, the use of a heavily doped substrate layer, and the use of high temperature cycles all significantly degrade CMOS performance. Independent optimization of the deep collector plug (DCP) implant and the buried layer (BL) is difficult especially in the presence of CMOS devices.
FIG. 9
illustrates an existing BJT
10
. The BJT
10
includes a substrate
12
, a collector structure
14
disposed in substrate
12
, a buried layer
16
, and deep trench isolation (DTI) structures
18
. BJT
10
also includes shallow trench isolation (STI) structures that include a collector-proximate STI (collector STI)
20
, a middle- or emitter-proximate STI (emitter STI)
22
, and a base-proximate STI (base STI)
24
. Upon substrate
12
, an epitaxial layer
26
is formed. An emitter stack
28
is disposed above the epitaxial layer
26
. Additionally, a deep collector plug
30
, a collector tap
32
and a base tap region
34
are part of BJT
10
.
Total resistivity from the collector structure to the collector tap in a BJT has a significant effect on performance. In
FIG. 9
, three significant resistivity paths exist. Although each path is depicted schematically by a dashed line, it is understood that the resistivity paths are actually located in 3-dimensional solid space in substrate
12
that is approximated by the dashed lines. A downward vertical first resistivity path
36
passes from collector structure
14
into substrate
12
toward buried layer
16
. First resistivity path
36
may amount to about 10% of the total resistivity between collector structure
14
and collector tap
32
. A horizontal second resistivity path
38
passes from first resistivity path
36
, under emitter STI
22
and toward deep collector plug
30
. Second resistivity path
38
may amount to about 30% of the total resistivity between collector structure
14
and collector tap
32
. An upward vertical third resistivity path
40
passes from second resistivity path
38
into collector plug
30
. Third resistivity path
40
may amount to about 60% of the total resistivity between collector structure
14
and collector tap
32
. For example first resistivity path
36
represents a range from about 300 ohm·cm
−2
to about 700 ohm·cm
−2
, second resistivity path
38
represents a range from about 1,300 ohm·cm
−2
to about 1,700 ohm·cm
−2
, and third resistivity path
40
represents a range from about 2,750 ohm·cm
−2
to about 3,250 ohm·cm
−2
.
Direction changes in current flow also affect efficiency. Accordingly, because of the downward first, horizontal second, and upward third resistivity paths, efficient current flow also is detrimentally affected due to directional changes.
FIG. 10
is a top layout schematic view depicting selected structures of BJT
10
without depicting elevational differences. A BJT perimeter
42
measures the BJT
10
from the outer edges
44
(
FIG. 9
) of collector STI
20
and base STI
24
. Emitter STI
22
and base STI
24
are part of a guard ring that is encompassed by BJT perimeter
42
. An exptaxial base layer perimeter
46
is also depicted that relates to epitaxial base layer
26
in FIG.
9
. Emitter stack
28
is depicted by its perimeter, and an intrinsic base region
48
, is also depicted by its perimeter as it forms substantially above collector structure
14
. Other selected structures include collector tap
32
and a base tap
50
portion of epitaxial layer
26
that is located within epitaxial base layer perimeter
46
. It is noted that current flows through substrate, beneath emitter STI
22
.
REFERENCES:
patent: 5064772 (1991-11-01), Jambotkar
patent: 6232638 (2001-05-01), Suzuki
patent: 6365479 (2002-04-01), U'Ren
patent: 6476452 (2002-11-01), Suzuki
patent: 0 354 153 (1990-02-01), None
patent: 0 468 271 (1992-01-01), None
patent: 0 476 380 (1992-03-01), None
patent: 0 779 663 (1997-06-01), None
patent: 61085864 (1986-01-01), None
W. Liu, et al., “Novel Doubly Self-Aligned AlGaAs/GaAs HBT,” Abstract, Electronic Letters, IEE Stevenage, GB, vol. 26, No. 17 Aug. 16, 1990 2 pages.
PCT Search Report dated Sep. 12, 2003, 7 pages.
Ahmed Shahriar
Bohr Mark
Chambers Stephen
Green Richard
Im Junghwa
Thomas Tom
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