Active solid-state devices (e.g. – transistors – solid-state diode – Bipolar transistor structure – With base region having specified doping concentration...
Reexamination Certificate
2000-11-17
2002-10-22
Elms, Richard (Department: 2824)
Active solid-state devices (e.g., transistors, solid-state diode
Bipolar transistor structure
With base region having specified doping concentration...
C257S565000, C257S622000
Reexamination Certificate
active
06469366
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same, and particularly relates to a semiconductor device provided with a bipolar transistor and a method of manufacturing the same.
2. Description of the Background Art
Bipolar transistors have been known as a kind of semiconductor devices. Bipolar transistors include npn (npn-type) bipolar transistors and pnp (pnp-type) bipolar transistors. The npn and pnp bipolar transistors may be arranged in a common semiconductor device. This kind of semiconductor device will be referred to as a “bipolar IC (Integrated Circuit)” hereinafter. The process of manufacturing the bipolar IC is executed based on the process of forming the npn bipolar transistor. Therefore, a structure shown in
FIG. 28
is often used for producing the pnp bipolar transistor of a good performance in the bipolar IC.
FIG. 28
is a schematic perspective view of a bipolar transistor IC which is an example of a conventional semiconductor device. Referring to
FIG. 28
, the conventional bipolar IC will now be described.
Referring to
FIG. 28
, the bipolar IC is provided with a pnp bipolar transistor and a npn bipolar transistor. In bipolar IC, n-type epitaxial layers
104
a
-
104
c,
104
f
-
104
h
are formed on a p
−
-type substrate
101
by an epitaxial growth method. n
+
-type buried regions
102
a
and
102
b
are formed in the boundary region between p
−
-type substrate
101
and n-type epitaxial layers
104
a
-
104
c,
104
f
-
104
h.
n
+
-type buried region
102
a
electrically isolates the pnp bipolar transistor from p
−
-type substrate
101
. n
+
-type buried region
102
b
forms a low resistance portion in a collector region of the npn bipolar transistor.
A p-type buried region
103
b
is formed on n
+
-type buried region
102
a.
p-type buried region
103
b
operates as a collector region of the pnp bipolar transistor. The bipolar IC is further provided with p
+
-type diffusion regions
105
b
and
105
c,
which are in contact with p-type buried region
103
b,
and extend to the top surfaces, i.e., the main surfaces of n-type epitaxial layers
104
a
-
104
c,
104
f
-
104
h.
p
+
-type diffusion regions
105
b
and
105
c
form a collector leader portion of the pnp bipolar transistor. An n-type epitaxial layer
104
c
is located in a region surrounded by p-type buried region
103
b
and p
+
-type diffusion regions
105
b
and
105
c.
n-type epitaxial layer
104
c
forms a base region of the pnp bipolar transistor. A p
+
-type diffusion region
106
b
serving as an emitter region of the pnp bipolar transistor is formed at the main surface of n-type epitaxial layer
104
c.
A p
+
-type diffusion region
106
a
is likewise formed in p
+
-type diffusion region
105
b.
This p
+
-type diffusion region
106
a
is provided for lowering the resistance of the collector leader portion of the pnp bipolar transistor. n-type epitaxial layer
104
c
is provided with an n
+
-type diffusion region
107
a.
n
+
-type diffusion region
107
a
is provided for lowering the base leader resistance. The pnp bipolar transistor is surrounded by n-type epitaxial layers
104
b
and
104
f
serving as an element isolating region.
An oxide film
108
is formed on the top surfaces of n-type epitaxial layers
104
a
-
104
c,
104
f
-
104
h.
Oxide film
108
is provided with a contact hole
109
a
located above p
+
-type diffusion region
106
a.
In a region located above p
+
-type diffusion region
106
b,
oxide film
108
is provided with a contact hole
109
b.
In a region located above n
+
-type diffusion region
107
a,
oxide film
108
is provided with a contact hole
109
c.
Electrodes
110
a
-
110
c
are formed on oxide film
108
. Electrode
110
a
is electrically connected to p
+
-type diffusion region
106
a
through contact hole
109
a.
Electrode
110
a
serves as a collector leader electrode. Electrode
110
b
is electrically connected to p
+
-type diffusion region
106
b
through contact hole
109
b.
Electrode
110
b
serves as an emitter leader electrode. Electrode
110
c
is electrically connected to n
+
-type diffusion region
107
a
through contact hole
109
c.
Electrode
110
c
serves as a base leader electrode. The pnp bipolar transistor shown in
FIG. 28
is of a vertical type, as can also be seen from FIG.
28
.
In the region located above n
+
-type buried region
102
b,
a p
+
-type diffusion region
106
c
is formed at the top surface of n-type epitaxial layer
104
g.
n
+
-type buried region
102
b
forms a high resistance portion of the collector region of the npn bipolar transistor. An n
+
-type diffusion region
107
c
is formed at the top surface of p
+
-type diffusion region
106
c.
An n
+
-type diffusion region
107
b
is formed at the top surface of n-type epitaxial layer
104
g.
n-type epitaxial layer
104
g
serves as a high resistance portion of the collector region of the npn bipolar transistor. p
+
-type diffusion region
106
c
serves as a base region of the npn bipolar transistor. n
+
-type diffusion region
107
c
serves as an emitter region of the npn bipolar transistor. n
+
-type diffusion region
107
b
is provided for lowering the collector leader resistance of the npn bipolar transistor.
Oxide film
108
is formed on the top surface of n-type epitaxial layer
104
g
as already described. In a region located above n
+
-type diffusion regions
107
b
and
107
c
as well as p
+
-type diffusion region
106
c,
oxide film
108
is provided with contact holes
109
d
-
109
f.
In regions located above contact holes
109
d
-
109
f,
electrodes
110
d
-
110
f
are formed on oxide film
108
, respectively. Electrode
10
d
is connected to n
+
-type diffusion region
107
b
through contact hole
109
d.
This electrode
110
d
serves as a collector leader electrode. Electrode
110
e
is electrically connected to n
+
-type diffusion region
107
c
through contact hole
109
e.
Therefore, electrode
110
e
serves as an emitter leader electrode. Electrode
110
f
is electrically connected to p
+
-type diffusion region
106
c
through contact hole
109
f.
This electrode
110
f
serves as a base leader electrode. This npn bipolar transistor is surrounded by an element isolating region which is formed of p-type buried regions
103
c
and
103
d
as well as p
+
-type diffusion regions
105
d
and
105
e.
In a region opposed to the npn bipolar transistor with the pnp bipolar transistor therebetween, the bipolar IC is provided with an additional npn bipolar transistor, although not shown. The element isolating region formed of p-type buried region
103
a
and p
+
-type diffusion region
105
a
serves as the element isolating region for this additional npn bipolar transistor. n-type epitaxial layer
104
a
serves as a high resistance portion of the collector region of the above additional npn bipolar transistor. An additional npn bipolar transistor is formed in a position opposed to the pnp bipolar transistor with the npn bipolar transistor therebetween. n-type epitaxial layer
104
h
forms a high resistance portion of the collector region of this additional npn bipolar transistor.
Referring to
FIGS. 29
to
32
, description will now be made on the method of manufacturing the bipolar IC shown in FIG.
28
.
FIGS. 29
to
32
are schematic cross sections or schematic perspective views for showing the method of manufacturing the bipolar IC, which is an example of the conventional semiconductor device and is shown in FIG.
28
.
As shown in
FIG. 29
, n
+
-type buried regions
102
a
and
102
b
are formed at the top surface of p
−
-type substrate
101
. p-type buried regions
103
a
-
103
d
are formed at predetermined regions of the top surface of p
−
-type substrate
101
.
Then, an epitaxial method is conducted to from n-type epitaxial layer
104
(see
FIG. 30
Nakashima Takashi
Tominaga Atsushi
Elms Richard
Smith Bradley
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