Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2001-06-13
2003-09-30
Wilson, Allan R. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S293000, C257S294000, C257S435000, C257S462000, C257S465000
Reexamination Certificate
active
06627929
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solid state image sensor and, more particularly, to a solid state image sensor and a method for fabricating the same which is adapted to simplify the process and enhance the morphology of the sensor.
2. Discussion of Related Art
With reference to the attached drawings, a conventional solid state image sensor and its fabricating method will be described below with respect to a method of forming a metal line between PDs (Photo-Diodes).
FIG. 1
is a cross-sectional view of a solid state image sensor fabricated according to prior art and
FIGS. 2
a
-
2
e
are cross-sectional views illustrating a method of fabricating the conventional solid state image sensor, wherein there are shown a pixel region, a contact forming region in a ferry region, and a pad forming region in the order from the left side of the figures.
Such a solid state image sensor, as shown in
FIG. 1
, has first, second and third transfer gates
12
,
13
and
14
between the PDs of the pixel region and in the contact forming region of the ferry region.
An HLD (High-temperature and Low-pressure Dielectric) layer
15
is provided to surround the first, second and third transfer gates
12
,
13
and
14
. There are further formed a second aluminum film
21
approximately 4000 Å thick as a light-shielding layer in the region exclusive of the photo-diodes, and a passivation layer
23
on the whole surface in the pixel region.
A contact hole is disposed between the HLD layer
15
and a smooth protective layer
16
, exposing defined regions of the first, second and third transfer gates
12
,
13
and
14
in the contact forming region. Further, a first aluminum film
17
is formed on the contact hole and smooth protective layer
16
and an insulating layer
19
consisting of PSiO is formed on the first aluminum film
17
. On the insulating layer
19
is disposed a passivation layer
23
.
On substrate
11
in the pad forming region are sequentially laminated HLD layer
15
, smooth protective layer
16
and first aluminum film
17
. The insulating layer
19
and passivation layer
23
are pad-open such that a defined portion of the first aluminum layer
17
is exposed.
FIGS. 2
a
-
2
e
are cross-sectional views illustrating a method for fabricating such a conventional solid state image sensor.
As shown in
FIG. 2
a
, a substrate
11
has first, second and third transfer gates
12
,
13
and
14
laminated between PDs (Photo-Diodes) and in the ferry region, and an HLD layer
15
surrounding the first, second and third transfer gates
12
,
13
and
14
. A nitride layer is deposited on the substrate
11
and a part of the nitride layer disposed in the ferry region is then eliminated. After deposition of a smooth protective layer
16
on the substrate
11
, a photo resist is deposited on the whole surface. Part of the photo resist in the contact forming region is then selectively patterned through an exposure and a development. Using the photo resist patterned as a mask, the smooth protective layer
16
and HLD layer
16
in the contact forming region are eliminated, exposing defined portions of the first, second and third transfer gates
12
,
13
and
14
. A first aluminum film
17
is deposited on the whole surface by a sputtering technique. Subsequently, a photo resist
18
is formed on the whole surface of the substrate
11
and selectively patterned through an exposure and a development to eliminate only the pixel region.
As shown in
FIG. 2
b
, the photo resist
18
patterned is used as a mask in eliminating the first aluminum film
17
in the pixel region. An insulating layer
19
consisting of PSiO is deposited on the smooth protective layer
16
in the pixel region and on the first aluminum film
17
in the contact forming region and in the pad region.
As shown in
FIG. 2
c
, a photo resist
20
is formed on the whole surface and selectively patterned through an exposure and a development such that only the photo resist
20
in the pixel region is eliminated. The photo resist
20
selectively patterned is used as a mask to eliminate the insulating layer
19
and smooth protective layer
16
.
As shown in
FIG. 2
d
, following removal of the photo resist
20
, a second aluminum film
21
is formed on the whole surface of the substrate
11
by the sputtering technique. A photo resist
22
is formed on the second aluminum film
21
and selectively patterned through an exposure and a development, etching the upper portion of the photo-diode in the pixel region and the photo resist
22
in the ferry region.
As shown in
FIG. 2
e
, the photo resist
22
patterned is used as a mask in performing an anisotropic etching of the upper portion of the photo-diode in the pixel region and the second aluminum film
21
in the ferry region. On the whole surface of the substrate
11
is deposited a passivation layer
23
consisting of PSiN. Next, the passivation layer
23
in the pas forming region and the insulating layer
19
consisting of PSiO are anisotropically etched to expose the first aluminum film
17
.
However, such a solid state image sensor and method for fabricating the same involves a problem that the entire number of processes is increased with a consequence of reduction in the productivity because two time of deposition of the aluminum film is required in forming the light-shielding layer in the pixel region and the metal line in the contact forming region and the pad forming region of the ferry region.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a solid state image sensor and method for fabricating the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a solid state image sensor and method for fabricating the same which is adapted to simplify the process and enhance the productivity.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a solid state image sensor, which has photo-diodes formed on a semiconductor substrate, and transfer gates disposed around the photo-diodes to transfer signal charges generated from the photo-diodes, includes: an insulating layer forming on the whole surface of the semiconductor substrate and having a contact hole exposing a defined portion of the transfer gates; a metal line formed to include the inside of the contact hole; and a light-shielding layer formed in the same layer with the metal line without overlapping the upper parts of the photo-diodes.
In another aspect of the present invention, a method for fabricating a solid state image sensor includes the steps of: forming an insulating layer on the whole surface of a semiconductor substrate having photo-diodes and transfer gates formed around the photo-diodes; selectively etching the insulating layer to form a contact hole exposing a defined portion of the transfer gates; forming a metal line on the whole surface of the substrate including the inside of the contact hole; first etching the metal line to a specified depth exclusive of a defined portion including the contact hole; and second etching part of the metal line etched corresponding to the photo-diode.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 4046609 (1977-09-01), Digoy
patent: 5338691 (1994-08-01), Enomoto et al.
patent: 5403384 (1995-04-01), Faul et al.
patent: 55102
Lee Seo Kyu
Shim Jin Seop
LG Semicon Co. Ltd.
Morgan & Lewis & Bockius, LLP
Warren Matthew E.
Wilson Allan R.
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