Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Charge transfer device
Reexamination Certificate
2001-01-29
2003-02-11
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Charge transfer device
C257S221000, C257S222000, C257S249000
Reexamination Certificate
active
06518605
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solid state imaging pickup device and a manufacturing method thereof, and more particularly but not limited to a solid state imaging pick device in which a charge transfer electrode is formed by processing a single-layer conductive electrode material film, characterized in that the controllability or ease of planarizing is improved when planarizing a narrow inter-electrode gap by re-flowing a film.
2. Description of the Related Art.
FIG. 1
shows a cross sectional view of a charge transfer part of a conventional solid state imaging pickup device with a singe-layer electrode structure.
The charge transfer part comprises a charge transfer part
604
that is formed by ion-implanting phosphorus in a first P-type well layer
602
and a second P-type well layer
603
formed on a N-type semiconductor substrate
601
, a gate insulating film
605
formed by thermally oxidizing the surface of the N-type semiconductor substrate
601
, and a charge transfer electrode
606
that is formed on the gate insulating film
605
.
The charge transfer electrode
606
is formed by patterning a one-layer conductive electrode material film with an inter-electrode gap of about 0.25 &mgr;m to 0.50 &mgr;m.
On the charge transfer electrode
606
, an inter-layer insulating film
607
is formed, and a metal shielding film
608
is provided on the inter-layer insulating film
607
to prevent the incidence of light into the charge transfer part.
Cross sectional views of the charge transfer part of a conventional solid state imaging pickup device with a single-layer electrode structure are shown in
FIGS. 2
to
4
in the order of manufacturing steps.
First, a P-type well layer
702
, a second P-type well layer
703
, a charge transfer part
704
, and a gate insulting film
705
are formed in turn on an N-type semiconductor substrate
701
. Further, on the substrate
701
, charge transfer electrodes
706
are formed, having an arca separating them from each other in the charge transfer direction (inter-electrode gap) of a short distance of about 0.25 &mgr;m to 0.50 &mgr;m (as shown in FIG.
2
).
Next, an inter-layer insulating film
707
is formed on the whole surface of the device. At this moment, the inter electrode gap part has a large aspect ratio and the step-covering performance of the insulating film is poor. Therefore, a space (cavity)
709
is produced at the inter-electrode gap part, or the resulting coverage of the surface is defective and/or uneven (as shown in FIG.
3
).
Next, a metal shielding film
708
or a metal wiring is formed on the interlayer insulating film
707
, but there has been such a problem that a step-cut
710
is produced where the coverage on the inter-layer insulating film
707
is poor at the inter-electrode gap part, such that the shielding characteristic or the charge transfer characteristic may be degraded (as shown in FIG.
4
).
A method that has been considered, in order to prevent the step-cut of the metal layer, is filling and planarizing the inter-electrode gap by using an insulator film which provides good re-flow performance when heated, after the charge transfer electrode has been patterned. The process-flow at this moment will be described by using cross sectional views in the order of steps shown in
FIGS. 5
to
9
.
First, a first P-type well layer
802
, a second P-type well layer
803
, a charge transfer part
804
, and a gate insulating film
805
are formed in turn on an N-type semiconductor substrate
801
. Further, on the substrate
801
, charge transfer electrodes are patterned so that charge transfer electrodes
806
are formed (as shown in FIG.
5
).
Next, a first inter-layer insulating film
811
is formed on the whole surface of the device, and is heat-treated, for example, in an atmosphere of nitrogen at 900° C., thereby re-flowing, and filling up the inter-electrode gaps with the first inter-layer insulating film
811
(as shown in FIG.
6
).
Next, the first inter-layer insulating film
811
is etched until the surface of the charge transfer electrodes
806
is exposed, thus forming embedded insulating films
821
(as shown in FIG.
7
).
Next, a second inter-layer insulating film
812
is formed on the charge transfer electrodes
806
and the embedded insulating film
821
(as shown in FIG.
8
).
Finally, a metal shielding film
808
is formed on the second inter-layer insulating film
812
(as shown in FIG.
9
).
By the conventional method described above, it is possible to form the metal shielding film
808
with no step-cut.
However, the above mentioned method of re-flowing the insulating film in an attempt to fill the inter-electrode gaps has the following problems, as described below.
FIG. 10
typically shows a pattern of conventional charge transfer electrodes
906
. At the part B-B′, there is no adjacent electrode pattern at the terminal part of the electrode pattern, and thus, there is no “wall” for stopping the flow of the film during re-flowing. Therefore, there is a problem in that a fluctuation is caused in the film thickness because the film outflows during re-flowing, resulting in poor embedding performance.
FIGS. 11 and 12
show cross sectional views in the order of steps of the part B-B′ in FIG.
10
.
First, a first inter-layer insulating film
911
is formed after charge transfer electrodes
906
have been formed, (as shown in FIG.
11
).
Next, the first inter-layer insulating film
911
is removed by etching until at least the surface of the charge transfer electrodes
906
is exposed (as shown in FIG.
12
).
As this moment, the first inter-layer insulating film
911
remains at the side wall part of the terminal part of the charge transfer electrode
906
, and a film thickness uneven area
913
is produced.
It is one object of the present invention to provide a highly reliable solid state imaging pickup device, in which the charge transfer electrodes are formed by patterning a singe-layer conductive electrode material film and the embedding performance is improved in the case where the inter-electrode gap parts are filled with the first inter-layer insulating film for solving the problems of the above described conventional solid state imaging pickup device.
SUMMARY OF THE INVENTION
In an embodiment of the semiconductor device of the present invention, a semiconductor device comprises a gate insulating film formed on a substrate, a plurality of charge transfer electrodes formed on the gate insulating film, and a first inter-electrode insulating film for filling a space between the plurality of charge transfer electrodes, with one charge transfer electrode surrounding at least one other charge transfer electrode.
As a result, the embedding performance of an insulating film is improved when it is re-flowed for flattening the inter-electrode gaps. This enables formation of a good metal wire or shielding film with no step-cut, and makes it possible to provide a solid state imaging pickup device with an improved reliability.
REFERENCES:
patent: 5637894 (1997-06-01), Hori et al.
patent: 6028629 (2000-02-01), Shioyama et al.
patent: 6097044 (2000-08-01), Nakashiba
patent: 6111279 (2000-08-01), Nakashiba
Furumiya Masayuki
Hatano Keisuke
Kawasaki Toru
NEC Corporation
Nelms David
Sughrue & Mion, PLLC
Tran Long
LandOfFree
Solid state imaging pickup device and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Solid state imaging pickup device and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Solid state imaging pickup device and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3165036