Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – On insulating substrate or layer
Reexamination Certificate
2000-12-27
2001-09-25
Picardat, Kevin M. (Department: 2822)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
On insulating substrate or layer
C438S154000, C438S406000
Reexamination Certificate
active
06294413
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for fabricating semiconductor device, and more particularly, to a method for fabricating an SOI semiconductor device.
2. Description of Related Art
A related art SOI device is disclosed in U.S. Pat. No. 6,110,769 issued to Jeong Hwan Son, titled “SOI (SILICON ON INSULATOR) DEVICE AND METHOD FOR FABRICATING THE SAME”, which is shown in FIGS.
1
A and
1
B-
1
H. Refer to
FIG. 1A
, which is a cross-sectional view showing a structure of a conventional SOI device.
A buried oxide film
25
is formed on a semiconductor substrate
24
. P and N-type heavily doped polysilicon layers
23
a
and
23
b
are formed on the buried oxide film
25
and isolated from each other by an isolation oxide film
26
formed on the buried oxide film
25
. Buried oxide films
22
a
are formed in the p and N-type heavily doped polysilicon layers
23
a
and
23
b
to be spaced apart.
A P-type semiconductor layer
20
b
and a first active region are formed on the first buried oxide film
22
a,
spaced apart from the P-type heavily doped polysilicon layer
23
a.
A first oxide film
21
is formed between the P-type semiconductor layer
20
b
and the first active region.
An N-type semiconductor layer
20
c
and a second active region are formed on the first buried oxide film
22
a,
spaced apart from the N-type heavily doped. A first oxide film
21
is formed between the N-type semiconductor layer
20
c
and the second active region.
A gate oxide film
29
and a first gate electrode
30
a
are successively formed on the first active region on the P-type heavily doped polysilicon layer
23
a.
Source/drain regions
34
a
/
34
b
are formed in the first active region at both sides of the first gate electrode
30
a.
A gate oxide film
29
and a second gate electrode
30
b
are successively formed on the second active region on the N-type heavily doped polysilicon layer
23
b.
Source/drain region
32
a
/
32
b
are formed in the second active region at both sides of the second gate electrode
30
b.
Formed is an interlayer insulating film
35
having contact holes on the p and N-type semiconductor layers
20
b
and
20
c
and the source/drain regions
32
a
/
32
b
and
34
a
/
34
b.
Contact pads
36
a
and
36
f
and line layers
36
b,
36
c,
36
d,
and
36
e
are formed in the contact holes and on the interlayer insulating layer adjoining to the contact holes.
The first and second active regions are connected to the p and N-type semiconductor layers
20
b
and
20
c
through the p and N-type polysilicon layers
23
a
and
23
b,
respectively.
Refer to
FIGS. 1B-1H
, are cross-sectional views showing conventional process steps of a method for fabricating the SOI device as shown in
FIG. 1A
First refer to
FIG. 1B
, a first semiconductor substrate
20
is provided. The first substrate
20
is etched to form a plurality of trenches. An oxide film is deposited on the substrate
20
and the trenches. Subsequently, a CMP process is performed to form a first oxide film
21
filling the trenches.
Next, a first buried oxide film
22
is formed on the first semiconductor substrate
20
by CVD.
A photoresist film is formed on the first buried oxide film
22
and patterned to expose areas of the first buried oxide film
22
. Using the patterned photoresist as a mask, the first buried oxide film
22
is removed to expose the first substrate
20
. Next an undoped polysilicon layer is deposited on the first buried oxide film
22
and the first substrate
20
. The undoped polysilicon layer is then etched-back forming a thick undoped polysilicon layer
23
.
A second semiconductor substrate
24
is provided and a second buried oxide film
25
is deposited on the second substrate
24
. Subsequently, the second buried oxide film
25
on the second substrate
24
and the undoped polysilicon layer
23
on the first substrate
20
are bonded together by undergoing a high temperature process
Refer to FIG.
1
C. The first substrate
20
is polished until the first oxide film
21
using the first oxide film
21
as an etch stop. In order to form a trench isolation region, the semiconductor layer
20
a
between the first oxide film
21
, the first buried oxide film
22
, and the undoped polysilicon layer
23
are etched. An oxide film is deposited on the first oxide film
21
, the semiconductor layer
20
a,
and the trench isolation region and then planarizing the oxide film to form an isolation oxide film
26
.
Next, a photoresist film
27
covers the first oxide film
21
, the semiconductor layer
20
a
and the isolation oxide film
26
. The photoresist film
27
is patterned and removed to expose part of the isolation oxide film
26
. Using the patterned photoresist film
27
as a mask, the undoped polysilicon layer
23
is injected with boron ions to create a P-type heavily doped polysilicon layer
23
a.
Refer to FIG.
1
D. Subsequently, another photoresist film
28
covers the first oxide film
21
, the semiconductor layer
20
a
and the isolation oxide film
26
and patterned. The photoresist film
28
is then removed to expose part of the isolation oxide film that was covered by the photoresist film
27
in the previous step. Using the patterned photoresist film
28
as a mask, the undoped polysilicon layer
23
a
is injected with phosphorus ions to become an N-type heavily doped polysilicon layer
23
b.
Refer to FIG.
1
E. An oxide film and a silicon layer are deposited and etched. The result is a gate oxide film
29
and a first gate electrode
30
a
for an NMOS transistor and a gate oxide film
29
and a second gate electrode
30
b
for a PMOS transistor formed on the semiconductor layer
20
a.
Refer to
FIG. 1F. A
photoresist film
31
is formed and patterned to expose the semiconductor layer
20
a
on both sides of the second gate electrode
30
b
and where the first gate electrode
30
a
is not formed. Using the patterned photoresist film
31
as a mask, the P-type semiconductor layer
20
b
is injected with P-type boron ions to form lightly doped source/drain regions
32
a
and
32
b.
Refer to
FIG. 1G. A
photoresist film
33
is formed and patterned to expose the semiconductor layer
20
a
on both sides of the first gate electrode
30
a
and where the second gate electrode
30
b
is not formed. Using the patterned photoresist film
33
as a mask, the N-type semiconductor layer
20
c
is injected with N-type As ions to form lightly doped source/drain regions
34
a
and
34
b.
Refer to FIG.
1
H. Depositing and removing an insulating film
35
to expose areas of the P-type semiconductor layer
20
b,
the N-type semiconductor layer
20
c,
the P-type source/drain regions
32
a
and
32
b
and the N-type source/drain regions
34
a
and
34
b
and form contact holes. A conductive layer is formed to fill the contact holes. The conductive layer is etched to form contact pads
36
a
and
36
f
on the P-type and N-type semiconductor layers
20
b
and
20
c
and line layers
36
b,
36
c,
36
d,
36
e
on the n and p source/drain regions
32
a
/
32
b
and
34
a
/
34
b.
The conventional method for fabricating an SOI semiconductor device as described above comprises implanting P-type ions to form regions
20
b,
32
a,
and
32
b.
Additionally, the conventional method requires implanting N-type ions to form regions
20
c,
34
a,
and
34
b.
Since photoresist films are used as ion-implantation masks, two lithography mask steps and two ion implantation steps need to be performed, which increases the complexity of the fabrication process and the cost thereof.
SUMMARY OF THE INVENTION
In accordance with the foregoing and other objectives of the present invention, the invention provides a method for fabricating a SOI semiconductor device, which overcomes the drawbacks of the conventional SOI device.
A first semiconductor substrate is etched to form a plurality of trenches. An oxide film is deposited on the substrate and the trenches. A first oxide film is deposited which fills the trenches. A first buried oxide film is formed on the first sem
Huang Jiawei
J.C. Patents
Picardat Kevin M.
Vanguard International Semiconductor Corp.
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